11/30/10
A group of scientists in Taiwan recently postulated that placing gold nanoparticles within the leaves of trees, causes them to give off a luminous reddish glow. The idea of using trees to replace street lights is an ingenious one – not only would it save on electricity costs and cut CO2 emissions, but it could also greatly reduce light pollution in major cities.
The discovery came about accidentally after the scientists were looking for a way to create high-efficiency lighting similar to LED technology, but without using toxic chemicals such as phosphor powder.
The researchers infused sea urchin shaped nanoparticles of gold inside the leaves of a Bacopa Caroliniana plant. The gold reacted with the chlorophyll, causing the leaves to emit a red glow, essentially creating a bio-LED. Under a high wavelength of ultraviolet light, the gold nanoparticles were able to produce a blue-violet fluorescence to trigger a red emission in the surrounding chlorophyll.
The research is still in its infancy and there are many issues that need to be ironed out, not the least of which is the high price of gold, which makes infusing even tiny amounts quite an expensive proposition.With all these challenges these kind of streetlights are dreams with the attached questions: what happens when the tree sheds leaves?, will gold nanoparticles disrupt the ability of chlorophyll to transfer its energy to the photosynthetic pathway? and so on, but the idea is certainly intriguing and could lead to other more feasible applications.
The discovery came about accidentally after the scientists were looking for a way to create high-efficiency lighting similar to LED technology, but without using toxic chemicals such as phosphor powder.
The researchers infused sea urchin shaped nanoparticles of gold inside the leaves of a Bacopa Caroliniana plant. The gold reacted with the chlorophyll, causing the leaves to emit a red glow, essentially creating a bio-LED. Under a high wavelength of ultraviolet light, the gold nanoparticles were able to produce a blue-violet fluorescence to trigger a red emission in the surrounding chlorophyll.
The research is still in its infancy and there are many issues that need to be ironed out, not the least of which is the high price of gold, which makes infusing even tiny amounts quite an expensive proposition.With all these challenges these kind of streetlights are dreams with the attached questions: what happens when the tree sheds leaves?, will gold nanoparticles disrupt the ability of chlorophyll to transfer its energy to the photosynthetic pathway? and so on, but the idea is certainly intriguing and could lead to other more feasible applications.
11/30/10 0
Gold nanoparticles are being used for an ever-growing number of applications. Gold nanoparticles are used in electronics, healthcare products, as pharmaceuticals to fight cancer, imaging tumors, carrying drugs, and delivering pulses of heat. Gold nanoparticles could function as in vivo sensors, photoactive agents for optical imaging, drug carriers, disinfection and tissue repair, contrast enhancers in computer tomography and X-ray absorbers in cancer therapy, automobile sensors, cell phones, blood sugar monitors and hydrogen gas production, but the process to make these nanoparticles requires dangerous and extremely toxic chemicals and acids as reducing and/or capping agents which have severe environmental impact. Hence green chemistry should be integrated into nanotechnologies at the source especially when nanomaterials are to be used in medical applications and when metal nanoparticles are intended for application to the human body, toxic chemicals should be excluded entirely from the process. Researchers have found methods that could replace nearly all of the toxic chemicals required to make gold nanoparticles by a natural products like cinnamon, soybeans, cumin, gum arabic, pear, black tea, turmeric, curcumin, geranium extract, bacteria and fungi etc.
Cinnamon
Researchers at University of Missouri have found a method that could replace nearly all of the toxic chemicals required to make gold nanoparticles by a natural product namely cinnamon. The researchers mixed gold salts with cinnamon and stirred the mixture in water to synthesize gold nanoparticles. The new process used no electricity and utilized no toxic agents making it is a true 'green' process.
Soybean
University of Missouri research team has used soybeans as a Phytochemical Reservoir for the Production and Stabilization of Biocompatible Gold Nanoparticles.
Researchers found that by submersing gold salts in water and then adding soybeans, gold nanoparticles could be generated. The water pulls a phytochemical out of the soybean that is effective in reducing the gold to nanoparticles. A second phytochemical from the soybean, also pulled out by the water, interacts with the nanoparticles to stabilize them and keep them from fusing with the particles nearby. This process creates nanoparticles that are uniform in size in a 100-percent green process. No toxic waste was generated.
Cumin
Researchers report an unprecedented synthetic route that involves the production of well-defined spherical gold nanoparticles by simple mixing of cumin to an aqueous solution of sodium tetrachloro aurate. Production of gold nanoparticles in this cumin-mediated Green Nanotechnological process is achieved under biologically benign conditions. The gold nanoparticles generated through cumin-mediated process did not aggregate suggesting that the cocktail of phytochemicals including proteins serve as excellent coatings on nanoparticles and thus, provide robust shielding from aggregations. In addition, the phytochemical coatings on nanoparticles have rendered nontoxic features.
Gum arabic
The researchers became interested in gum arabic, a substance taken from species of the acacia tree, because it is already used to stabilize everyday foods such as yogurt, Big Macs and soda. Gum arabic has unique structural features, including a highly branched polysaccharide structure consisting of a complex mixture of potassium, calcium and magnesium salts derived from arabic acid. The scientists found that gum arabic could be used to absorb and assimilate metals and create a "coating" that makes gold nanoparticles stable and nontoxic. Gum arabic can effectively 'lock' gold nanoparticles to produce nontoxic, nanoparticulate constructs that can be used for potential applications in nanomedicine.
Black tea, turmeric, curcumin or cinnamon
In methods of the invention, an aqueous solution containing gold salts is mixed with polyphenols- or flavanoids-rich plant material. In preferred embodiment methods of making, an aqueous solution containing gold salts is provided. The aqueous solution is mixed with black tea, turmeric, curcumin or cinnamon or a similar naturally occurring polyphenols- or flavanoids-rich plant material. The gold salts react to form biocompatible gold nanoparticles that are stabilized with a coating of the polyphenols- or flavanoids-rich plant material. The black tea, turmeric, curcumin or cinnamon or similar naturally occurring polyphenols- or flavanoids-rich plant material can be a powder or can be in its root or bark form.
Pear
Korean researchers have used pear extract to obtain phytochemically-derived reducing agents for the generation and stabilization of gold nanoparticles. Pear extract is a reservoir of phytochemicals including organic acids, amino acids, peptides and proteins. In addition, the presence of saccharides in the extract provides synergistic reducing power for the rapid transformation of chloroaurate ions into gold nanoparticles. Simple mixing of pear extract (50% [v/v]) with HAuCl4 (2 mM) at 90 oC promptly initiated the appearance of a purple-red color, indicating the formation of gold nanoparticles.
Geranium extract
It has been reported that the synthesis of gold nanoparticles using geranium extract required more time to initiate and was complete in 48 h.
Emblica officinalis fruit extract
The extra cellular synthesis of highly stable Ag and Au nanoparticles has also been achieved using Emblica officinalis fruit extract.
Bacteria and fungi
Biosynthesis of silver and gold nanoparticles using bacteria, and fungi,has been reported, and the time required for completion of the reaction ranged from 24 to 120 h. Intracellular synthesis, prolonged synthesis, multiple purification steps and the maintenance of cell cultures are the drawbacks of microbial procedures.
These methods are attractive because biocompatible gold nanoparticles can be rapidly produced and stabilized under safe conditions.
Cinnamon
Researchers at University of Missouri have found a method that could replace nearly all of the toxic chemicals required to make gold nanoparticles by a natural product namely cinnamon. The researchers mixed gold salts with cinnamon and stirred the mixture in water to synthesize gold nanoparticles. The new process used no electricity and utilized no toxic agents making it is a true 'green' process.
Soybean
University of Missouri research team has used soybeans as a Phytochemical Reservoir for the Production and Stabilization of Biocompatible Gold Nanoparticles.
Researchers found that by submersing gold salts in water and then adding soybeans, gold nanoparticles could be generated. The water pulls a phytochemical out of the soybean that is effective in reducing the gold to nanoparticles. A second phytochemical from the soybean, also pulled out by the water, interacts with the nanoparticles to stabilize them and keep them from fusing with the particles nearby. This process creates nanoparticles that are uniform in size in a 100-percent green process. No toxic waste was generated.
Cumin
Researchers report an unprecedented synthetic route that involves the production of well-defined spherical gold nanoparticles by simple mixing of cumin to an aqueous solution of sodium tetrachloro aurate. Production of gold nanoparticles in this cumin-mediated Green Nanotechnological process is achieved under biologically benign conditions. The gold nanoparticles generated through cumin-mediated process did not aggregate suggesting that the cocktail of phytochemicals including proteins serve as excellent coatings on nanoparticles and thus, provide robust shielding from aggregations. In addition, the phytochemical coatings on nanoparticles have rendered nontoxic features.
Gum arabic
The researchers became interested in gum arabic, a substance taken from species of the acacia tree, because it is already used to stabilize everyday foods such as yogurt, Big Macs and soda. Gum arabic has unique structural features, including a highly branched polysaccharide structure consisting of a complex mixture of potassium, calcium and magnesium salts derived from arabic acid. The scientists found that gum arabic could be used to absorb and assimilate metals and create a "coating" that makes gold nanoparticles stable and nontoxic. Gum arabic can effectively 'lock' gold nanoparticles to produce nontoxic, nanoparticulate constructs that can be used for potential applications in nanomedicine.
Black tea, turmeric, curcumin or cinnamon
In methods of the invention, an aqueous solution containing gold salts is mixed with polyphenols- or flavanoids-rich plant material. In preferred embodiment methods of making, an aqueous solution containing gold salts is provided. The aqueous solution is mixed with black tea, turmeric, curcumin or cinnamon or a similar naturally occurring polyphenols- or flavanoids-rich plant material. The gold salts react to form biocompatible gold nanoparticles that are stabilized with a coating of the polyphenols- or flavanoids-rich plant material. The black tea, turmeric, curcumin or cinnamon or similar naturally occurring polyphenols- or flavanoids-rich plant material can be a powder or can be in its root or bark form.
Pear
Korean researchers have used pear extract to obtain phytochemically-derived reducing agents for the generation and stabilization of gold nanoparticles. Pear extract is a reservoir of phytochemicals including organic acids, amino acids, peptides and proteins. In addition, the presence of saccharides in the extract provides synergistic reducing power for the rapid transformation of chloroaurate ions into gold nanoparticles. Simple mixing of pear extract (50% [v/v]) with HAuCl4 (2 mM) at 90 oC promptly initiated the appearance of a purple-red color, indicating the formation of gold nanoparticles.
Geranium extract
It has been reported that the synthesis of gold nanoparticles using geranium extract required more time to initiate and was complete in 48 h.
Emblica officinalis fruit extract
The extra cellular synthesis of highly stable Ag and Au nanoparticles has also been achieved using Emblica officinalis fruit extract.
Bacteria and fungi
Biosynthesis of silver and gold nanoparticles using bacteria, and fungi,has been reported, and the time required for completion of the reaction ranged from 24 to 120 h. Intracellular synthesis, prolonged synthesis, multiple purification steps and the maintenance of cell cultures are the drawbacks of microbial procedures.
These methods are attractive because biocompatible gold nanoparticles can be rapidly produced and stabilized under safe conditions.
11/29/10
Since carbon nanotubes have a high electrical conductivity and fine tip, they are really good field emitters. However, their aspect ratio has made it difficult to fit them into triodes without losing this advantage. They are also relatively difficult to produce in large uniform batches, are very sensitive to adsorbed gases, and are rather difficult to bind securely within the device.
CNT based field Emission Cold Cathode
Carbon nanotubes are the best field emitters of any known material. They can be metallic as well as semi conducting, depending on the tube geometry. They are mechanically extremely stiff and resistant to bending with high electrical conductivity and sharp tip. If the tip is placed close to another electrode and a voltage is applied between the tube and electrode, a large electric field builds up near the tip of the tube and emits an electron beam. The magnitude of the electric field is inversely proportional to the radius of curvature of the tip. Thus the sharper the tip is, the larger the electric field. Even with only a few volts applied to an electrode a few microns away from the nanotube tip, electric fields in the range of a millions of Volts per centimeter will build up near the tip. These fields are large enough to pull a substantial number of electrons out of the tip. As "cold cathode" electron emitters, carbon nanotube films have been shown to be capable of emitting over 4 Amperes per square centimeter. Furthermore, the current is extremely stable.
CNT based field Emission Cold Cathode
Carbon nanotubes are the best field emitters of any known material. They can be metallic as well as semi conducting, depending on the tube geometry. They are mechanically extremely stiff and resistant to bending with high electrical conductivity and sharp tip. If the tip is placed close to another electrode and a voltage is applied between the tube and electrode, a large electric field builds up near the tip of the tube and emits an electron beam. The magnitude of the electric field is inversely proportional to the radius of curvature of the tip. Thus the sharper the tip is, the larger the electric field. Even with only a few volts applied to an electrode a few microns away from the nanotube tip, electric fields in the range of a millions of Volts per centimeter will build up near the tip. These fields are large enough to pull a substantial number of electrons out of the tip. As "cold cathode" electron emitters, carbon nanotube films have been shown to be capable of emitting over 4 Amperes per square centimeter. Furthermore, the current is extremely stable.
Carbon nanotubes (CNTs) based field emission (FE) cathodes are used in the area of electric propulsion (EP) which need an efficient electron source to neutralize the exhaust plume in low-power EP devices. Since most low-power EP systems have limited power capacity, any expenditure in power that does not directly generate thrust is a source of inefficiency. Hence rather than using a hollow cathode, CNT cathodes are used for plume neutralization. Researchers have demonstrated the potential of FE cathodes not only in the areas of low power EP, but also in the areas of propellant-less propulsion such as space tethers, and spacecraft charge control.
Lateral field emitters, or emitters parallel to a substrate, have attracted considerable attention in vacuum microelectronics due to ease of fabrication and packaging, design versatility of electrode geometry, and precise control of spacing between electrodes by fine photolithography. Researchers have found that lateral emitter arrays can be fabricated based on the lateral arrays of CNTs assembled using dielectrophoresis.
Highly graphitic carbon nanotubes of diameter of 5−8 nm can be obtained from a thermal reaction of activated carbon and Bi2O3 powders, which was grown via a carbon-thermal reduction and Bi catalyzed vapor−liquid−solid process. Individual carbon nanotubes terminated with an onion-shaped carbon can be used to make field emitters having excellent emission properties. They can be operated at a very large current density, low voltage for a long period of high emission stability at a high emission current density under a constant applied voltage. Hence, as-fabricated CNTs could act as excellent electron emitters and have great potential application in field emission panel displays.
Researchers at the Naval Research Laboratory (NRL), US, have made carbon nanotube arrays that can produce a field emission. The devices contained arrays of carbon nanotubes grown by chemical vapour deposition on micro fabricated template structures with integral gates. The researchers claim that the current densities are more than adequate for applications such as micro satellite thrusters, portable x-ray sources, miniature gas analyzers, general cold-cathode lighting sources, high-performance microwave tubes, lightning arrestors, electron microscope cathodes and field emission displays. The carbon nanotube field emitter arrays are also robust, can be regenerated and do not suffer from destructive arcing.
Film field emitter (FFE) s is very useful in many applications like accelerator and high intensity X-ray sources for medical and security examinations.
However, carbon nanotubes can lead to the creation of new types of flat-panel displays. In contrast to traditional cathode ray tube monitor, where one electron gun creates the entire picture, using carbon nanotubes can instead create individual electron guns for each pixel, thus increasing the resolution of the monitor.
MWNT based field emitters
Multi-walled nanotubes (MWNTs)-based conducting polymer/metal-oxide/metal/MWNTs composites (polyaniline (PANI)/SnO2/Sn/MWNTs) have been synthesised. MWNTs can be made by chemical vapour deposition technique. SnO2/Sn/MWNTs can be prepared by using chemical reduction followed by calcinations. By in situ polymerisation method, surface of SnO2/Sn/MWNTs were coated with PANI. PANI/SnO2/Sn/MWNTs field emitters were fabricated over flexible graphitised carbon fabric substrate by spin coating technique. The fabricated PANI/SnO2/Sn/MWNTs field emitters exhibit excellent field emission properties with a turn on field of 1.83 V µm-1 and a field enhancement factor of 4800.
Samsung and Motorola besides others are using the above materials for display applications.
Film field emitter (FFE) s is very useful in many applications like accelerator and high intensity X-ray sources for medical and security examinations.
However, carbon nanotubes can lead to the creation of new types of flat-panel displays. In contrast to traditional cathode ray tube monitor, where one electron gun creates the entire picture, using carbon nanotubes can instead create individual electron guns for each pixel, thus increasing the resolution of the monitor.
MWNT based field emitters
Multi-walled nanotubes (MWNTs)-based conducting polymer/metal-oxide/metal/MWNTs composites (polyaniline (PANI)/SnO2/Sn/MWNTs) have been synthesised. MWNTs can be made by chemical vapour deposition technique. SnO2/Sn/MWNTs can be prepared by using chemical reduction followed by calcinations. By in situ polymerisation method, surface of SnO2/Sn/MWNTs were coated with PANI. PANI/SnO2/Sn/MWNTs field emitters were fabricated over flexible graphitised carbon fabric substrate by spin coating technique. The fabricated PANI/SnO2/Sn/MWNTs field emitters exhibit excellent field emission properties with a turn on field of 1.83 V µm-1 and a field enhancement factor of 4800.
Samsung and Motorola besides others are using the above materials for display applications.
11/29/10 0
11/28/10
Carbon nanotubes hold great promise due to their extraordinary electrical, mechanical, optical, thermal, and chemical properties. Their current applications range from improving consumer electronics, to medicine delivery to cells, to strengthening airplane components. Carbon nanotubes come in many different forms and purities. They range from flexible, thin, few-walled or single-walled nanotubes (SWNTs) to rigid, long, thick, multi-walled nanotubes (MWNTs), with a spectrum of characteristics.
Nanotubes transistor developments
Researchers at Stanford University, Cornell University and Purdue University have jointly produced a carbon nanotube transistor that they claim has better properties than silicon transistors of an equivalent size. The device uses zirconium oxide rather than silicon dioxide, which has a lower dielectric constant, as the gate insulator. Highest performance carbon nanotube field-effect transistors were made to date by integrating zirconia gate insulators. They obtained 70 mV/decade sub threshold swings approaching the theoretical limit for transistors. The scientists used semi conducting single-walled nanotubes (SWNTs) to make p-type field-effect-transistors (FETs). They formed the zirconia gate insulators by atomic layer deposition, creating zirconia films of about 8 nm thick without significantly degrading key transistor performance parameters of the nanotubes, such as mobility. The team converted p-type ZrO2/SWNT-FETs to n-type transistors by heating them in molecular hydrogen at 400°C for one hour. The properties of the n-type transistors, although good, were not as ideal as the p-type FETs. The researchers also made a NOT logic gate, i.e. an inverter, by connecting a p- and n-type ZrO2/SWNT-FET. The device had a high voltage gain.
Zurich researchers have built a transistor whose crucial element is a carbon nanotube, suspended between two contacts, with outstanding electronic properties. A novel fabrication approach allowed the scientists to construct a transistor with no gate hysteresis. This opens up new ways to manufacture nano-sensors and components that consume particularly little energy.
Researchers of University of California at Irvine developed a device which consists of a single-walled carbon nanotube sandwiched between two gold electrodes to operate at extremely fast microwave frequencies. This has resulted is an important effort to develop nano electronic components that could be used to replace silicon in a range of electronic applications.
Researchers from the University of California, San Diego and Clemson University synthesized Y-shaped carbon nanotubes to make transistors. The nanotube transistors were initially grown as straight nanotube elements. Titanium-modified iron catalyst particles added to the synthesis mixture were then attached to the straight nanotubes, nucleating additional growth, which continued in a fashion similar to branches growing from a tree trunk. The nascent nanotubes assumed a Y-shape with the catalyst particle gradually becoming absorbed at the junction of the stem and two branches. When electrical contacts are attached to the nanotube structures, electrons travel into one arm of the Y, hop onto the catalyst particle, and then hop to the other arm and flow outward. The movement of electrons through the Y-junction can be finely controlled, or gated, by applying a voltage to the stem, a replication of the function of existing transistors.
Printable transistors
The semi conducting properties of carbon nanotubes can be exploited to create printable transistors with extremely high performance. Specifically, researchers have shown CNT-based transistors employing a sparse nanotube network to achieve mobility of 1 cm2/V-s, while those using an aligned array of single-walled nanotubes can reach as high as 480 cm2/V-s. Nanotubes also prove to be useful additives to polymer-based TFTs and help to overcome some of the shortcomings of those devices. Beyond their performance, such devices are compatible with solution-based printing techniques, which enable dramatic cost savings in such devices as LCDs and OLED-based displays.
11/28/10 0
11/27/10
Researchers from the University of Massachusetts Lowell Nanomanufacturing Center of Excellence have created nano-heater elements and systems to overcome the limitations of macroscale heaters, The nano-heaters may be used in nanoscale manufacturing or on-board thermal actuation and for autonomous powering during operation of nanosized devices such as Micro and Nano-Electro-Mechanical Systems (MEMS & NEMS). Nano-heaters can be used as a power source for nanorobots or find use in biomedical applications, pharmaceutical and chemical devices using on-board thermal conditioning for sensors and processing, industrial and military biochemical detectors and patterned porous scaffolds for tissue engineering. Nano-heater elements and systems that could make nanofabrication processes cheaper and more precise.
But this technology has been used in the kitchen to heat and make tea.
Mexican designer Emma Moreno has come up with an innovative infuser entitled the “Duo” that uses nanotechnology for heating, giving an entirely new meaning to the traditional way of making tea. The new infuser is simple to use, all you need to do is fill it up, turn it on and choose the heating level, and then put it into your cup where it heats up as soon as it gets in touch with hot water. Leave it there for a few minutes, before enjoying the refreshing cup of tea. Featuring a touch screen interface with on/off and heating button, the Duo attaches the tea tag at the bottom cap to keep all the pieces together, while the transparent cover ensures that you see the whole process. Hope this technology makes a refreshing tea.
11/27/10 1
11/26/10
Many methods are used for nanoribbon production like, lithography, chemical reactions and ultrasoundinfluenced chemistry. But all these methods fail to produce the needed quantity or quality of graphene nanoribbons.
Fabrication processes
Fabrication processes
Researchers at Stanford University have developed a new method that will allow relatively precise production of mass quantities of the tiny ribbons by slicing open carbon nanotubes. The nanotube is to be opened up without destroying the whole structure. For this, carbon nanotubes are placed on a substrate and then coated with a polymer film. The film covers the entire surface of each nanotube, save for a thin strip where the nanotube is in contact with the substrate. The film is easily peeled off from the substrate, taking along all the nanotubes and exposing the thin strip of polymer free surface on each of them. A chemical etching process using plasma can then slice open each nanotube along that narrow strip. The process works not only on single-layer carbon nanotubes but also on nanotubes with concentric layers of nanotubes, allowing each layer to be sliced open. The ribbons can easily be removed from the polymer film and transferred onto any other substrate, making it easy to create items such as graphene transistors for making high-performance electronic devices and computer chips.
Researchers at Rice University have developed a room-temperature chemical process that splits, or unzips, carbon nanotubes to make flat nanoribbons. This technique makes it possible to produce the ultra thin ribbons in bulk quantities.
Sulfuric acid and potassium permanganate are used to attack single and multi walled carbon nanotubes, reacting with the carbon framework and unzipping them in a straight line. Nearly all of the nanotubes subjected to unzipping turn into graphene ribbons. But the multi walled nanotubes are much cheaper starting materials, and the resulting nanoribbons would be useful in a host of applications.
Engineers at University of Michigan have demonstrated that when a light was shone on flat nanoribbons, they curled up into spirals. The photons of light can lead to such a remarkable change in rigid structures a thousand times bigger than molecules, This spiral structure is very important for optics and could lead to the development of new materials.
Stanford chemists have developed a new way to make transistors out of carbon nanoribbons. The devices could be integrated into high-performance computer chips to increase their speed and generate less heat, which can damage silicon-based chips when transistors are packed together tightly.
University of California at Berkeley, US, has now used ab initio calculations to show that certain carbon nanoribbons will display half-metallicity, Researchers have predicted that a small ribbon made of the carbon honeycomb pattern found in graphite and nanotubes could display intriguing electronic properties and serve as a material for spin-based electronics (spintronics),
Properties
Properties
Nanoribbons are strong, thermally and electrically conductive and have a very large aspect ratio. This material is amorphous as it has little long-range atomic order. As a result the surface chemistry is more closely related to Diamond-like Carbon and Carbon Blacks, making nanoribbons much more easy to disperse in most media. The fibres are flat in cross-section, with an average fibre measuring 30nm wide by ca.2nm thick by 100’s of microns long (up to 1mm). Material is commercially supplied as a highly porous black powder. See : www.nano-tek.co.uk/
Applications of Nano-ribbons
• Multi-functional composites
• Biosensors
• Catalyst support
• Electrodes
• Lubricant additive
Potential applications of nanoribbon coatings
• Catalysis
• Sensors
• Electrodes
Available forms
Nano-Ribbons are also available as a homogeneous coating on substrates such as Quartz, Si-wafer, 316 and 440c stainless foils and plate. The majority of the nano-fibres show some alignment perpendicular to the plane of the substrate CostNano-Ribbons of purity ca. 99.9% C, SSA ca. 300m2g-1 has a price of £80 to 350/ g.
11/26/10 0
11/25/10
Carbon fibers
Carbon fibers are used in structural composites in aerospace, automotives, and sporting equipment, a strong fibre when added to polymer precursor. Here CNTs act as a nucleating agent for polymer crystallization to improves the polymer orientation. Incorporation of 1 wt % of nanotubes into polyacrylonitrile precursors can increase the tensile strength and modulus of the resulting carbon fiber by 64% and 49%, respectively. Plastics which are good electrical insulators, but they can be made to have electrical conductivity by loading them with conductive fillers, such as carbon black, Carbon nanotubes and graphite fibers. The natural tendency of Carbon nanotubes to form ropes provides inherently very long conductive pathways even at relatively low loadings.
Carbon nanotubes
Carbon nanotubes can be dispersed in polymers and epoxies to improve the compression, shear, and bending strengths, including stiffness, toughness, fatigue life, failure mechanisms and wear properties. Likewise nanotubes can be used to improve the modulus and toughness of elastomers and a wide variety of thermoset composite systems at loading levels of one percent or less. Carbon nanotubes blend well with plastics, and can impart reasonable conductivity at modest loadings. Carbon nanotubes have very high surface area (upto 1000 m2/g), good electrical conductivity, excellent chemical stability in acidic environments, linear geometry that makes their surface highly accessible to the electrolyte which are the desired intrinsic characteristics necessary for use as electrodes in batteries, capacitors (exceeding 100 Farads/gram), and fuel cells. Carbon nanotubes have the highest reversible capacity of any carbon material for use in lithium-ion batteries. Nanotubes could also have a significant impact on the biotech, pharmaceutical, and medical device industries. Nanotubes can be functionalized to target certain types of cells. Several research groups have published data demonstrating that nanotubes could be used as drugs or to deliver drugs to targeted cells. Nanotubes might also be used as miniature biosensors for drug discovery, diagnostics, detect small amounts of molecules through electrical, optical, or mechanical means to get specific information about targets for therapeutics.
11/25/10 1
11/24/10
Carbon nanotubes can be considered as graphitic sheets rolled into open cylindrical form with diameters in the range of few nanometers and lengths up to several micrometers. Each nanotube is a single molecule made up of a hexagonal network of covalently bonded carbon atoms.
Types
Carbon nanotubes are of both single-walled and multi-walled. A single-walled carbon nanotube (SWNT) has a single grapheme cylinder, while a multi-walled carbon nanotube (MWNT) has several concentric grapheme cylinders.
Properties
Nanotubes have unusual properties due to strong covalent bonding, nanometer size and unique one-dimensional structure. The extraordinary properties include very high tensile strength, high resilience, electronic properties ranging from metallic to semi-conducting, the ability to sustain high current densities and high thermal conductivity. This makes carbon nanotubes a suitable material to be used as fillers in super-strong composite materials, as wires and components in nano-electronic devices, as tips of scanning probe microscopes and in flat panel displays and gas sensors.
Basis of properties
In a single carbon nanotube, every atom is on two surfaces - the inside and the outside, and a single gram of nanotubes has over 2400 m2 of surface area. The nature of the carbon bonding gives the tubes their great tensile strength and electrical and thermal conductivity. The carbon nanotubes stiffness and toughness derives from their molecular perfection. In most materials the actual observed stiffness and toughness are degraded very substantially by the occurrence of defects in their structure. For example, high strength steel typically fails at about 1% of its theoretical breaking strength. Carbon nanotubes, however, achieve values very close to their theoretical limits because of their perfection of structure - there are no structural defects where mechanical failures can begin. It is, however, the tubular geometry of carbon nanotubes that gives them their most exotic properties.
An example of CNT typical properties:
Purity of CNTs90%, Content of SWNTs, 60%, Diameter 2 nm, Length 20 nm, Amorphous carbon 5%, Ash (catalyst residue) 3%, surface area 450 m2/g, Thermal conductivity 4000 W/m•k.
Preparation
MWNTs were earlier prepared by the arc-discharge of graphite electrodes, but now, MWNTs are prepared in large quantities by the chemical vapor deposition process. High yields of SWNTs can be obtained by the following methods.
1.Arc-discharge of Ni-Y catalyzed graphite electrodes,
2.Laser ablation of Ni-Co catalyzed graphite targets and
3.Vapor phase paralysis of CO and Fe(CO)5 (HiPCO process).
Purity
Carbon nanotubes are always get contaminated with impurities like amorphous carbon, residual metal catalyst and graphitic nanoparticles during manufacture and handling and hence purification and chemical processing are vital steps in before any application of Carbon nanotubes.
Applications
• Electronical nanocomponents (diodes, transistors, nano-wires, etc.)
• Field emission
• Multi-functional composites(EMI shielding, thermal conducting, strengthen, conducting, etc.)
• Hydrogen storage
• Rechargeable lithium batteries
• Atomic force microscope (AFM) tips
• Electrode material of supercapacitors
• Biosensors
Cost (approx.)
SWNT
SWNTs prepared by the electric arc method with purity 40-60%, price $50/gram,
Processed AP-SWNTs containing lower carbonaceous and catalyst related impurities with purity 70-90%, price $ 400/gram,
Purified SWNTs with high carboxylic acid content 80-90%, price $ 400/gram,
Water soluble SWNTs functionalized with poly m-aminobenzene sulfonic acid (PABS) price $ 1500/gram
MWNT
Coiled multi-walled carbon nanotubes with purity: > 60%, Outside diameter: 100-200 nm, Length: 1-10 um,SSA: > 50 m2/g, price $70/g
Multi-walled nanotubes Purity: 95+%, Amorphous carbon: <3%,>
Multi-wall nanotubes purity 99+%, outside dia <>
Suppliers
There are a number of manufacturers and suppliers of carbon nanotubes and it is difficult to list them all. In general North American manufacturers focus more on single wall Carbon nanotubes. In Asia and Europe, Japan tops the list and China stands second in the production of multi wall Carbon nanotubes. Showa Denko, Mitsui and Hodogaya Chemical are among the largest suppliers. Many of the nanotubes marketed by the suppliers are incorporated into transparent conductive films for the display and touch panel industries. Nanotubes are sold to select customers as powders and in suspensions in liquids, also called inks.
Cheap production, purification and separation of conducting and semiconducting nanotubes of selective and uniform size with specific diameter, length and electrical properties is yet to be completely achieved in commercial scale.
Safety
Safety
Safe-handling and environmentally sound handling of carbon nanotube by academic, governmental and industry organizations is very important. Due to difficulty in safe-handling requirements these materials, manufacturers do not sell nanotubes directly to the public and the consumer products containing nanotubes have minimal risk of exposure because the nanotubes are bound in polymeric solid or film, isolated from the consumer and environment. The chemical industries adopt well-established procedures for protecting workers who are handling nanomaterials. Always waste materials resulting from the manufacture of nanotubes are disposed of in accordance with regulations.
11/24/10 2
11/23/10
Basic books
1. Carbon Nanotubes and Related Structures New Materials for the Twenty-First Centuryby Peter J F Harris, (Department of Chemistry, University of Reading, UK), Published by Cambridge University Press and also published in China by Beijing World Publishing., 296pp Hardback ... ISBN: 0521554462. Price: £50-00/$80-00, Paperback ISBN: 0521005337. Price: £29.95/$39.95.
The new book by Peter Harris reviews the properties of carbon nanotubes and clarifies their promise as revolutionary new materials for the twenty-first century. Harris has written a most readable and useful book, which contains a wealth of up-to-date information for specialists and non-specialists. The book highlights the main challenges that have to be overcome if carbon-based nanotube technology is to fulfil the exciting, indeed revolutionary, promise that the already-known properties forecast.
2. Physical Properties of Carbon Nanotubes, English / Japanese, Authors: Riichiro Saito, Gene Dresslhaus, and M. S. Dresselhaus, Publisher: Imperial College Press (London) , ISBN 1-86094-093-5, Price: $35(hard Cover)/$24(soft cover) U.S. 258pages.
Physical Properties of Carbon Nanotubes is an introductory textbook for the graduate students and researchers who start to learn carbon nanotubes from many fields of science. Although progress in the field is still at an early stage, the book focuses on the basic principles behind the physical properties. Some computational source codes which generate coordinates of carbon nanotube are included in the textbook which will be useful to start the research.
3. Science and Application of Nanotubes, Edited by:David Tománek Richard Enbody, Kluwer Academic Publishers (available as of early March, 2000), ISBN 0-306-46372-5, David Tomanek at Michigan State University.
4. Carbon Nanotubes, Basic Concepts and Physical Properties, ISBN-10: 3-527-40386-8, ISBN-13: 978-3-527-40386-8 - Wiley-VCH, Berlin, 1. Edition - January 2004, 132.- Euro, 2004. IX, 215 Pages, Hardcover 126 Fig.- Monograph.
This text is an introduction to the physical concepts needed for investigating carbon nanotubes and other one-dimensional solid-state systems. Written for a wide scientific readership, each chapter consists of an instructive approach to the topic and sustainable ideas for solutions. The former is generally comprehensible for physicists and chemists, while the latter enable the reader to work towards the state of the art in that area. The book gives for the first time a combined theoretical and experimental description of topics like luminescence of carbon nanotubes, Raman scattering, or transport measurements. The theoretical concepts discussed range from the tight-binding approximation, which can be followed by pencil and paper, to first-principles simulations.
Nano sites
• www.thenanoage.comwww.pa.msu.edu/cmp/csc/nanotube.html,
Mirror Sites:
nanotube.msu.edu/,
www.pa.msu.edu/cmp/csc/nanotube.html
Nanotube Link Sites
University of Reading: Peter Harris' Nanotube Site
Enzo Menna at University of Padova: Library of nanotechnology links
11/23/10 0
11/21/10
Tungsten trioxide nanomaterials are of tremendous interest due to their potential use as electro chromic, gas sensing, and photo catalyst materials. The synthesis of doped and undoped tungsten oxide nanowires is done using either tungsten foils or powders as sources. Utilizing chemical vapor transport of metal oxide vapor species andoxygen flow over hot-filaments onto substrates, metal oxide nanowires can be fabricated. In vapor phase synthesis route, the chemical vapor of tungsten oxide is transported onto substrates kept at temperatures higher than the decomposition temperature resulting in tungsten nanowires. The synthesis of tungsten oxide nanowires can also be accomplished without the use of any catalysts or any medium.
Hot-filament CVD reactor
Hot filament CVD reactor setup is used for the synthesis. It consists of a quartz tube housed in a tube furnace heater with the ends connected to the necessary accessories for flow and pressure control. A tungsten filament of small diameter and long length is used as the tungsten source. The tungsten filament is always heated to a temperature of about 1950 K and quartz boats are employed to curtail the deposition directly onto the tube walls. The substrates (quartz and fluorinated tin oxide coated quartz slides) are placed on the boat and heated for 10-15 minutes. The synthesized nanowires are collected in a dry powder form by scraping the material from the quartz substrates.
The nanowires obtained are oxygen deficient W18O49 phase and subsequent oxidation of these substrates in an oven changes the phase to WO3 as indicated by a change in color from blue to green. Tungsten oxide nanowires can remain in the solution for longer periods of time without sediment or any kind of agglomeration compared to nanoparticles in organic solvents.
11/21/10 0
11/20/10
Engineered nanomaterials have a positive impact in improving many sectors of economy, including consumer products, pharmaceutics, cosmetics, transportation, energy and agriculture etc., and are being increasingly produced for a wide range of applications within industry and research establishments. These are intentionally designed and created with physical properties tailored to meet the needs of specific applications. They can be end products in and of themselves, as in the case of quantum dots or pharmaceutical drugs, or they can be components later incorporated into separate end products, such as carbon black in rubber products. Either way, the physical properties of the particles are extremely important to their performance and the performance of any product into which they are ultimately incorporated.
Types
Engineered nanomaterials can be grouped into four types:
1 - Carbon based materials, usu¬ally including fullerene, single walled carbon na¬notube (SWCNT) and multiwalled carbon nano¬tubes (MWCNT);
2 - Metal based materials such as quantum dots, nanogold, nanozinc, nanoalumi¬num and nanoscales metal oxides like TiO2, ZnO and Al2O3;
3 - Dendrimers which are nano-sized polymers built from branched units, capable of being tailored to perform specific chemical func¬tion and
4 - Composites which combine nanoparticles with other nanoparticles or with larger bulk-type materials and present differ¬ent morphologies such as spheres, tubes, rods and prisms.
Uses
Uses
Nanoscale materials are used in electronic, magnetic and optoelectronic, biomedical, pharmaceutical, cosmetic, energy, catalytic and materials applications. Areas producing the greatest revenue for nanoparticles reportedly are chemical-mechanical polishing, magnetic recording tapes, sunscreens, automotive catalyst supports, biolabeling, electro conductive coatings, optical fibers, non-volatile magnetic memory, automotive sensors, landmine detectors and solid-state compasses.
11/20/10 0
A spiral or twisted carbon fiber shows various properties which a straight carbon fiber does not possess. The spiral or twisted carbon fiber has a large surface area compared with a straight carbon fiber having the same length of fiber, has a fine curved surface or angle as seen from any direction, has an electrical inductance, and has a mechanical spring function.
Nanorope structure
Carbon nanotubes can self-organize into "ropes," which consist of many (typically, 10-100) tubes running together along their length in contact with one another. Since the sides of the tubes are very smooth, carbon bonds of one tube can get relatively close to the next one and the electrons in one tube will influence the motion of some electrons in its neighbor to give rise to a short-range attractive van der Waals force between the tubes. This binding energy is approximately 0.5eV per nanometer of contact length and carbon bonds will be very difficult to separate. Such formed ropes can be far longer than any individual tube within them, but are virtually endless, branching off from one another, then joining others while individual tubes are typically about 100-2000 nm in length. In the nanoropes more than dozens of individual nanotubes are stacked together in a fairly regular pattern and looped up. These ropes are useful in providing very long electrically conductive pathways in nanotube films and composite materials.
This structure also lead to a cable or rope that has much better load transfer mechanism in tension, than a straight bundle would have. This is akin to the fact that twisted textile fibre or a steel wire is more stronger than a bundle of untwisted fibres.
The carbon nano-twist and carbon nano-rope has a structure having no space, that is, a structure having no hole in its central portion as seen from its longitudinal direction and is more stronger due to the fact that more than one carbon nano-fibers is twisted and intertwined.
Fabrication
Carbon nano-rope films can be fabricated on the Ni-catalysed Si substrate by microwave plasma-enhanced chemical vapor deposition employing a mixture of acetylene and hydrogen. These nano-ropes will be in the form of self-assembled, stranded of carbon nano-fibers aligned perpendicular to the substrate.
A carbon nano-fiber, particularly twisted carbon nano-fiber such as a carbon nano-coil, carbon nano-twist or carbon nano-rope is produced by means of a catalyst by CVD method using carbon-containing gas as a raw material and a catalyst comprising one or more components selected from the group consisting of Cr, Mn, Fe, Co, Ni and oxide thereof and one or more components selected from the group consisting of Cu, Al, Si, Ti, V, Nb, Mo, Hf, Ta, W and oxide thereof.
Application
A nano-rope made of a single type of specially chosen molecule will be very strong. A cable or rope can be assembled with incredible tensile strength with correctly-aligned nanotubes. A nanotube rope of one centimeter diameter can support the weight of one human being and weighs just 10 milligrams per kilometer.It is lightweight and invisible and can be used to create a series of invisible ropes in architecture.
Nanorope structure
Carbon nanotubes can self-organize into "ropes," which consist of many (typically, 10-100) tubes running together along their length in contact with one another. Since the sides of the tubes are very smooth, carbon bonds of one tube can get relatively close to the next one and the electrons in one tube will influence the motion of some electrons in its neighbor to give rise to a short-range attractive van der Waals force between the tubes. This binding energy is approximately 0.5eV per nanometer of contact length and carbon bonds will be very difficult to separate. Such formed ropes can be far longer than any individual tube within them, but are virtually endless, branching off from one another, then joining others while individual tubes are typically about 100-2000 nm in length. In the nanoropes more than dozens of individual nanotubes are stacked together in a fairly regular pattern and looped up. These ropes are useful in providing very long electrically conductive pathways in nanotube films and composite materials.
This structure also lead to a cable or rope that has much better load transfer mechanism in tension, than a straight bundle would have. This is akin to the fact that twisted textile fibre or a steel wire is more stronger than a bundle of untwisted fibres.
The carbon nano-twist and carbon nano-rope has a structure having no space, that is, a structure having no hole in its central portion as seen from its longitudinal direction and is more stronger due to the fact that more than one carbon nano-fibers is twisted and intertwined.
Fabrication
Carbon nano-rope films can be fabricated on the Ni-catalysed Si substrate by microwave plasma-enhanced chemical vapor deposition employing a mixture of acetylene and hydrogen. These nano-ropes will be in the form of self-assembled, stranded of carbon nano-fibers aligned perpendicular to the substrate.
A carbon nano-fiber, particularly twisted carbon nano-fiber such as a carbon nano-coil, carbon nano-twist or carbon nano-rope is produced by means of a catalyst by CVD method using carbon-containing gas as a raw material and a catalyst comprising one or more components selected from the group consisting of Cr, Mn, Fe, Co, Ni and oxide thereof and one or more components selected from the group consisting of Cu, Al, Si, Ti, V, Nb, Mo, Hf, Ta, W and oxide thereof.
Application
A nano-rope made of a single type of specially chosen molecule will be very strong. A cable or rope can be assembled with incredible tensile strength with correctly-aligned nanotubes. A nanotube rope of one centimeter diameter can support the weight of one human being and weighs just 10 milligrams per kilometer.It is lightweight and invisible and can be used to create a series of invisible ropes in architecture.
Nanotubes are very interesting objects for channeling research. A beam can be trapped in a single nanotube cylinder of 1 nm diameter or in a rope consisting of many nanotubes. Also particle beam of very small cross-section is just emerging as a beam instrument and is found useful in many accelerator applications including biological and medical ones. A typical nano-rope consisting of 100-1000 nanotubes would be a source that gives an emittance of the nano-beam of the order of 0.001p nm horizontally and vertically, factor of 10000 down from the figure potentially achievable with a traditional amorphous source.
Polypyrrole nanowires formed by polymerization of pyrrole on a DNA template self-assemble into rope-like structures. These ‘nanoropes’ may be quite smooth (diameters 5–30 nm) or may show frayed ends where individual strands are visible. Nanoropes are conductive and adhere more weakly to hydrophobic surfaces prepared by silanization of SiO2 than to the clean oxide; this effect can be used to aid the combing of the nanoropes across microelectrode devices for electrical characterization
Researchers in China have demonstrated that an effective design of single-walled carbon nanotubes (SWCNTs) can be used to convert the surface energy of liquids into electricity. The surface-energy generator's mechanism works due to the unique channels among individual SWCNTs, in which a continuous, steady flux of liquid forms and the flow of liquid inside the carbon nanotube channels is driven by surface tension.
Nanorope device
Nanorope device
SWCNT 'rope' of approximately 25 mm length and 0.6 mm diameter is made by aligning individual nanotubes. The researchers connected this nanorope to electrodes of aluminum film and suspended this structure on a glass slide. This device was then placed into a beaker partially filled with ethanol, with an angle between the SWNT rope and the ethanol level. When the ethanol level reaches the SWCNT rope, the voltage begins to increase. This increase is almost linear from zero to 200 µV for the first 240 seconds, then the voltage saturates gradually at 219 µV where is remains constant over 6 hours. Researchers found that the voltage can remain constant as long as the ethanol level is contacting the SWCNT rope.
This concept can be used to design self-powered devices at the nanoscale. Its advantages are high power output (up to about 1800 pW per device), low inner resistance (tens to hundreds of Ohm), stability (the polar liquid can be used like fuel), and no moving parts. It is easy to integrate with other low-energy-cost electronic devices and power them. Furthermore, the generators can be connected in serial and parallel to get higher output.
11/19/10
Carbon nanotubes hold great promise due to their extraordinary properties. Carbon nanotubes come in many different forms and purities. They range from flexible, thin, few-walled or single-walled nanotubes (SWNTs) to rigid, long, thick, multi-walled nanotubes (MWNTs), with a spectrum of characteristics and properties in-between. Carbon nanotubes can be one, two or more tubular fullerenes nested inside one another and due to the perfection of their sidewalls, these endotopic structures also form ropes.
There are currently at least five methods for producing carbon nanotubes: (1) Chemical Vapor Deposition (CVD), (2) arc discharge, (3) laser ablation, (4) HIPCO, and (5) surface mediated growth of vertically-aligned tubes by Plasma Enhanced Chemical Vapor Deposition (PECVD).
Properties
High Electrical Conductivity
Carbon nanotubes are the best conductors of electricity of any organic molecule ever discovered with a current carrying capacity per unit area that is 100 times greater than copper. Varying structures of carbon nanotubes can be defined by two indices, typically labeled n and m which specify uniquely the chirality by the ordered pair (n,m). Electronically, carbon nanotubes can be either semiconducting or metallic, depending on the value of (n-m).Tubes in which (n-m) is either zero or a multiple of 3, have electrons in their conduction bands at room temperature, conduct electricity very well, and are called metallic nanotubes. All other structures produce nanotubes that are true semiconductors, with a band gap typically between 0.5 and 3.5 electron-Volts. The band gap varies inversely with the diameter of the tube, and for a tube of 1 nm diameter, the band gap is about 1 eV. Their conductivity has been shown to be a function of their chirality (degree of twist), as well as their diameter.
Electron mobility
Carbon nanotube transistors can have a mobility that is 70 times higher than silicon.
High thermal conductivity
The thermal conductivity along the carbon nanotube is twice that of diamond (which was the best thermal conductor until the discovery of CNTs) and has a thermal conductivity of about 3000 Watts per meter-degree Kelvin. Thermal conductivity is very high along its axis because vibrations of the carbon atoms propagate easily down the tube.
Very high mechanical strength
The tensile strength of carbon nanotubes is 100 times greater than steel, but CNTs are less dense than aluminum. Nanotubes are the stiffest, strongest, and toughest molecule known, Young's modulus is up to 1.4 TPa and tensile strength is well above 100 GPa,
11/19/10 0
11/18/10
There are literally hundreds of different carbon nanotube structures. These structures can be identified by assuming the carbon nanotube as a sheet of graphene wrapped into a seamless cylinder. But, there are many ways to do this and the cylinder can have a wide range of dimensions.
classification scheme
After the discovery of fullerene nanotubes, a classification scheme was devised to describe the different conformations of graphene cylinders. This classification scheme uses an ordered pair of numbers, (n,m), and is based upon the diagram of graphene.
Each carbon atom in the graphene sheet is bonded to three other carbon atoms, forming a Y-shaped vertex of carbon-carbon bonds. In order to make a seamless graphene tube of a uniform diameter, the graphene sheet must be wraped in a way that permits every carbon atom in the cylinder to be bonded to three other carbon atoms where the sheet joins to itself. The number of ways this wrapping can be achieved is countable according to the numbering scheme followed. The unit vectors of the 2-dimensional graphene lattice are given as a1 and a2. Each vertex that could possibly join to the origin during a wrapping operation is labeled with an ordered pair wherein the first number of the pair is the distance (in lattice repeat units) of the vertex from the origin along a1, and the second number is the distance of the vertex from the origin along a2. For example a graphene sheet can be wrapped so that the vertex labeled (10,5) lands on top of the origin and this is classified as the (10,5) tube. In the (10,5) tube, the carbon hexagons appear to "spiral" around the tube's axis.
Conformations
The spiraling is sometimes referred to as the chirality of the tube, and the chirality is uniquely specified by the ordered pair (n,m). As do all chiral structures (such as wood screws, for example), the tubes have a "handedness". An (i,j) tube is the mirror image of a (j,i) tube, but is otherwise identical. There are two classes of nanotube conformations that are sometimes called "achiral" because their structure is completely symmetric, and the carbon hexagons do not spiral about the tube axis, but lie in lines exactly parallel to the axis. These two highly-symmetric conformations are the (n,0) (which are exactly the same as (0,n) tubes) and the (n,n) tubes. The (n, 0) tubes are often called "zig-zag" tubes since, if the tube is cut so that the open end has carbon atoms in a regular zig-zag pattern. Likewise the (n,n) tubes are sometimes referred to as armchair tubes because the carbon atoms at the cut end are in a pattern with two up, two down, and then two up again, which is reminiscent of the seat and arms of an armchair.
In production of nanotubes, there is a minimum size for the graphene sheet cylinder, which is believed to be a (4,4) tube.
11/18/10 0
Regenerative medicine, novel therapies for cancer and development of powerful diagnostic tools is the aim of future nano medical research.
Future possibilities
Regenerative medicines for reversal and prevention of paralysis and blindness through regeneration of spinal cord and retina, curing stroke dysfunction through neuron repair, new cartilage development, bone fracture repair, formation of new teeth and curing of Parkinson’s and Alzheimer’s diseases are some of the future possibilities.
Developments for blood vessel growth
Researchers at Northwestern University have developed a novel nanostructure that promotes blood vessel growth. This will be very useful for healing wounds and could become an important tool in regenerative medicine and cancer treatment, where new blood vessel formation is critical. The nanofiber's basic building block is a peptide amphiphile that has a hydrocarbon chain on one end and a polypeptide designed to bind heparin on the other. Heparin, a biopolymer that binds to angiogenic growth factors, is used to nucleate the self-assembly of nanostructures from designed peptide amphiphile molecules. In the presence of heparin, these chain like molecules assemble into cylindrical fibers with the hydrocarbon chains at the core and the peptide-heparin complex at the surface. When added with nanogram amounts of angiogenic, growth factors are known to interact with heparin and the nanostructures stimulate extensive new blood vessel formation in vivo. Researchers think that the defined shape and surface of nanostructure account for its remarkable angiogenic properties.
11/17/10
Nanomaterials and nanotechnology have been widely applied in the last decade. As nanoparticles become more and more popular, the risk of exposure from nanoparticles also increases. There is now an extensive debate about the risks and benefits of the many manufactured nanomaterials into the environment. Nanoparticles are introduced into the soil, water and environment as a result of human activities. Because of their widespread use in consumer products it is expected that nanomaterials will find their way into aquatic, terrestrial and atmosphere environments. Nanoparticles might leach into the water from landfill runoff or become airborne as part of garbage . Their fate and behavior are largely unknown.
Nanomaterials and plants
To examine the toxicity of nanotechnology on plant functions a team of researchers from China treated cells from rice plant species Arabidopsis with carbon nanotubes to assess the viability of cells, damage to DNA, and the presence of reactive oxygen species and find the effect of nanotubes on plant cells. They found an increase in levels of the reactive oxygen species, hydrogen peroxide causes oxidative stress to cells which can cause cell death with higher dose. But cells exposed to carbon particles that were not nanotubes did not suffer any ill effects. According to the researchers "The current study has provided evidence that certain carbon nanoparticles are not 100% safe and have side effects on plants, suggesting that potential risks of nanotoxicity on plants need to be assessed,"
Another research revealed that ZnO nanoparticles at certain concentrations could adsorb onto ryegrass root surface, damage root tissues, enter root cells, and inhibit seedling growth. Inhibition of root growth varied greatly among nanoparticles and plants and partially correlated to nanoparticles concentration.
Investigation on the dissolution of ZnO nanoparticles and its contribution to the phytotoxicity revealed that in the presence of ZnO nanoparticles, ryegrass biomass significantly reduced, root tips shrank, and root epidermal and cortical cells highly vacuolated or collapsed.
Magnetic nanoparticles in small concentrations had a stimulating effect on the growth of the plantlets while the enhanced concentration of aqueous ferro fluid solution induced an inhibitory effect.
Nanomaterials and plants
To examine the toxicity of nanotechnology on plant functions a team of researchers from China treated cells from rice plant species Arabidopsis with carbon nanotubes to assess the viability of cells, damage to DNA, and the presence of reactive oxygen species and find the effect of nanotubes on plant cells. They found an increase in levels of the reactive oxygen species, hydrogen peroxide causes oxidative stress to cells which can cause cell death with higher dose. But cells exposed to carbon particles that were not nanotubes did not suffer any ill effects. According to the researchers "The current study has provided evidence that certain carbon nanoparticles are not 100% safe and have side effects on plants, suggesting that potential risks of nanotoxicity on plants need to be assessed,"
Another research revealed that ZnO nanoparticles at certain concentrations could adsorb onto ryegrass root surface, damage root tissues, enter root cells, and inhibit seedling growth. Inhibition of root growth varied greatly among nanoparticles and plants and partially correlated to nanoparticles concentration.
Investigation on the dissolution of ZnO nanoparticles and its contribution to the phytotoxicity revealed that in the presence of ZnO nanoparticles, ryegrass biomass significantly reduced, root tips shrank, and root epidermal and cortical cells highly vacuolated or collapsed.
Magnetic nanoparticles in small concentrations had a stimulating effect on the growth of the plantlets while the enhanced concentration of aqueous ferro fluid solution induced an inhibitory effect.
Similarly nano alumin particles did not have a negative effect on the growth of Phaseolus vulgaris and Lolium perenne in the tested concentration range. Metal nanoparticles influence the growth of Lactuca seeds and increase the shoot/root length.
Researchers at University of Delaware, in Newark, found that pumpkin plants can take up magnetite - magnetic iron oxide - nanoparticles through their roots and that the particles are transported around the plant.
A study shows that nanoparticles are transported inside the plants and are present both in the extra cellular space and within some cells and likewise smaller Pd nanoparticles cause stress effects in leaves of a selected plant at low concentration in nutrient solution.
Certain plants take up a significant amount of magnetite nanoparticles from liquid growth medium and to accumulate them within roots and leaves particularly silver nanoparticles.
Tomato seeds exposed to CNTs germinated faster and grew into larger, heavier seedlings than other seeds.
Auburn University researchers state that tomato plants uptake the silver nanoparticles from the hydroponic solution and these silver nanoparticles led to the death of the plants. It was also found that the smaller the silver nanoparticles, the quicker the tomato plants die.
Cerium dioxide nanoparticles exposed either as aerosol or as suspension indicated that the biological barriers of plants are more resistant against nanoparticle translocation.
Scientists have also reported the first evidence that CNTs penetrate the hard outer coating of seeds, and have beneficial effects. Nanotube-exposed seeds sprouted up to two times faster than control seeds and the seedlings weighed more than twice as much as the untreated plants. Those effects may occur because nanotubes penetrate the seed coat and boost water uptake.
The phytotoxicity of nano-CeO2, nano-La2O3, nano-Gd2O3 and nano-Yb2O3 on radish, rape, tomato, lettuce, wheat, cabbage and cucumber were investigated by the Chinese researchers. They found that root growth varied greatly between different nanoparticles and plant species.
A study indicated that silver nanoparticles inhibited seed germination at lower concentrations, but showed no clear size-dependant effects, and never completely impeded germination.
Researchers at the New Jersey Institute of Technology in Newark tested and found that varying concentrations of aluminum oxide nanoparticles on hydroponically grown species cabbage, carrot, corn, cucumber and soybean resulted in a significant reduction in root growth.
It is not strange to find both positive and negative effects of nanoparticles on higher plants. It is clear that different plants have different response to the same nanoparticles. However, limited or no information is available on plant cell internalization of nanoparticles or other particles. Researches report positive or negative evidence for the toxicity of nanoparticles as it depends on their property, test organism species, and surrounding solution conditions.
Despite the scientists' observations that carbon nanotubes had toxic effects on plant cells, the use of nanotechnology in the agriculture industry still has great promise.
Researchers at University of Delaware, in Newark, found that pumpkin plants can take up magnetite - magnetic iron oxide - nanoparticles through their roots and that the particles are transported around the plant.
A study shows that nanoparticles are transported inside the plants and are present both in the extra cellular space and within some cells and likewise smaller Pd nanoparticles cause stress effects in leaves of a selected plant at low concentration in nutrient solution.
Certain plants take up a significant amount of magnetite nanoparticles from liquid growth medium and to accumulate them within roots and leaves particularly silver nanoparticles.
Tomato seeds exposed to CNTs germinated faster and grew into larger, heavier seedlings than other seeds.
Auburn University researchers state that tomato plants uptake the silver nanoparticles from the hydroponic solution and these silver nanoparticles led to the death of the plants. It was also found that the smaller the silver nanoparticles, the quicker the tomato plants die.
Cerium dioxide nanoparticles exposed either as aerosol or as suspension indicated that the biological barriers of plants are more resistant against nanoparticle translocation.
Scientists have also reported the first evidence that CNTs penetrate the hard outer coating of seeds, and have beneficial effects. Nanotube-exposed seeds sprouted up to two times faster than control seeds and the seedlings weighed more than twice as much as the untreated plants. Those effects may occur because nanotubes penetrate the seed coat and boost water uptake.
The phytotoxicity of nano-CeO2, nano-La2O3, nano-Gd2O3 and nano-Yb2O3 on radish, rape, tomato, lettuce, wheat, cabbage and cucumber were investigated by the Chinese researchers. They found that root growth varied greatly between different nanoparticles and plant species.
A study indicated that silver nanoparticles inhibited seed germination at lower concentrations, but showed no clear size-dependant effects, and never completely impeded germination.
Researchers at the New Jersey Institute of Technology in Newark tested and found that varying concentrations of aluminum oxide nanoparticles on hydroponically grown species cabbage, carrot, corn, cucumber and soybean resulted in a significant reduction in root growth.
It is not strange to find both positive and negative effects of nanoparticles on higher plants. It is clear that different plants have different response to the same nanoparticles. However, limited or no information is available on plant cell internalization of nanoparticles or other particles. Researches report positive or negative evidence for the toxicity of nanoparticles as it depends on their property, test organism species, and surrounding solution conditions.
Despite the scientists' observations that carbon nanotubes had toxic effects on plant cells, the use of nanotechnology in the agriculture industry still has great promise.
11/17/10 0
11/16/10
Low-temperature synthesis of nanocrystalline TiO2 anatase is a very big problem when using sputtering technology, CVD and other methods. For getting crystalline anatase temperature used in these synthesis methods is usually around 300°C and higher. But researchers at Vietnam have synthesised nanocrystalline TiO2 at a low-temperature of 60°C by sol-gel technique with glass and Nafion substrates to get nanocrystallline .
Titanium tetraisopropoxide (TTIP) (98%), ethanol (99.5%), HCl (37%), water and PEG 600 were used by them as the starting materials. Water and 3% of PEG 600 (av. mol wt 600) were then introduced to the mixture with vigorous stirring at 80°C to allow the formation of a stable, homogenous and transparent sol solution. Following the process, titania sol formed by this procedure was deposited on the substrates of glass and Nafion N117 membrane by spin coating. The substrates coated by titania sol were taken out and dried at 60°C in a vacuum dryer for 8 hours. PEG aided sol-gel process produced a very stable colloidal solution. The water added together with PEG in the hydrolysis mixture has some molecules associated with the PEG through hydrogen bonding. The sol particles formed by the sol-gel reaction are covered by the PEG chains to form particle-PEG complex and physical cross-linking and agglomeration of these particulate complexes leads to an inorganic polymer composite. The thin solid film of TiO2 on Nafion membrane prepared by sol-gel was identified to be single anatase phase of nanosize TiO2 particles, it is dense and appears to be well attached to the membrane.
11/16/10 0
Food fortification and modificationNanotechnology will be used to transform or manufacture food from the atom up by designing and shaping molecules and atoms. Food can be fortified with nano-encapsulated nutrients, its appearance and taste can be boosted by nano-developed colors, fat and sugar content can be removed or disabled by nano-modification, and ‘mouth feel’ can be improved. Companies are designing ‘smart’ foods that will interact with consumers to ‘personalize’ food, changing color, flavor or nutrients on demand. Food ‘fortification’ means increasing the nutritional value in a processed food, for example the inclusion of ‘medically beneficial’ nano-capsules can enable chocolate chip cookies or hot chips to be marketed as health promoting or heart cleansing food item. Color, flavor, concentration and texture of the individual’s choice can be trigger released using domestic microwave oven. Nanotechnology can also change junk foods like ice cream and chocolate and modify to reduce the amount of fats and sugars that the body can absorb suitably either by replacing some of the fats and sugars with other substances, or by using nanoparticles to prevent the body from digesting or absorbing these components of the food. Vitamin and fiber-fortified fat and sugar-blocked junk food are also to be developed as health promoting and weight reducing food. Clear, tasteless drink that contains hundreds of flavors in latent nanocapsules can be developed using nanotechnology and ‘Smart’ foods can also be developed to sense when an individual is allergic to a food’s ingredients, and block the offending ingredient.
Food Packaging
Nanocomposites can be used to act as a barrier to the entry of gases such as oxygen or carbon dioxide, restrict the entry of both liquid and vapor phase chemicals and to the migration of odor and at the same time impede absorption of flavors and vitamins by the plastic packaging material itself. This barrier behavior of nanocomposites keeps products without decay and increases shelf life. Nanocomposite packaging material reduces weight of packages and thus package cost. The enhancement of shelf life and lower package cost dominate the uses of nanotechnology in food packaging.
11/14/10
Nanosensors are inherently more sensitive than any other kind of sensor, making them a future choice where lives are at stake. In addition, their small size and potentially low cost means that they can be widely deployed.To detect very small amounts of chemical vapors carbon nanotubes, zinc oxide nanowires or palladium nanoparticles are used in nanotechnology-based sensors. These detecting elements work on the basis of changing the electrical characteristics when gas molecule strikes them. With these sensors a few gas molecules are sufficient to change the electrical properties of the sensing elements and hence the detection or monitoring is easy even with a very low concentration of chemical vapors. The goal is to make small and inexpensive sensors.
Various application of these sensors are in airport security concerns in the checking of vapors given off by explosive devices. These sensors can also be used in industrial plants to detect the release of harmful chemical vapors, leakage of hazardous chemical vapour, detection of specific gases and tracking of air pollution sources. Nanofabricated sensors are projected to reduce plant production costs since in most instances, they will be mounted on wireless packages, which eliminate wiring and cabling costs. Health, security, and environmental concerns will be major drivers for nanosensors. Security is the second driver for sensors and actuators. In the same way that nanosensors can provide ever more information on a person’s state of health, they can also provide more data to confirm a person’s identity or indicate the provenance of an object or document.
Hydrogen sensor have been developed with a layer of closely spaced palladium nanoparticles that are formed by a beading action. This works on the principle that when hydrogen is absorbed the palladium nanoparticles swell, causing short circuit between nanoparticles to lower the resistance of the palladium layer.
Sensors are made using a layer of gold nanoparticles on a polymer film for detecting volatile organic compounds (VOCs). This works on the principle that when the polymer swells in presence of VOCs, the spacing between the gold nanoparticles changes and the resistance of the gold layer changes.
Advancements in nanosensors have resulted in the invention of new-generation equipment as well as alternative technologies for detecting anthrax and other dangerous gases. Sensors using nanoporous silicon detection elements could detect chemical gas leaks or release of a toxin.
Nanotechnology Companies and their products
Company and its products
Nanomix :Carbon nanotube based sensors for detecting low levels of industrial gas. Carbon nanotube based sensors for monitoring carbon dioxide and nitric oxide levels in a patient's breath to provide a quick evaluation of their respiratory status.
Applied Nanotech: Palladium nanoparticle-based hydrogen sensor.Sensor based upon enzyme coated carbon nanotubes for analyzing chemicals in liquid samples.
Owlstone Nanotech: MEMS based sensor for detecting a wide range of gasses.
11/14/10 0
UCLA chemists report on creating a synthetic "gene" that could capture heat-trapping carbon dioxide emissions, which contribute to global warming, rising sea levels and the increased acidity of oceans. A three-dimensional, synthetic DNA-like crystal has been created by combining organic and inorganic units for codings information in a DNA-like manner by UCLA chemists. It is not so sophisticated as DNA, but it is new in the field of chemistry and materials science. The discovery could lead to cleaner energy and capture of carbon dioxide will be easy for factories and automobiles which emit highest carbon dioxide. Scientists say that the finding will be important for potentially getting to a viable carbon dioxidecapture material with ultra-high selectivity. Further they feel optimistic about the technology and feel that they could create a material that can convert carbon dioxide into a fuel, or a material that can separate carbon dioxide with greater efficiency.
Nanotechnology is employed in food science to develop several products, from how crop is grown to how food is packaged. Companies are developing and using nanomaterials that will make a difference not only in the taste of food, but also in food safety, and the health benefits. In making lightweight bottles, cartons and packaging films, nano clay composites are being used to provide an impermeable barrier to gasses such as oxygen or carbon dioxide. Storage bins are being produced using plastics embedded with silver nanoparticles to kill bacteria from any material that was previously stored in the bins, minimizing health risks from harmful bacteria. Nanoparticles are being developed to deliver vitamins or other nutrients in food and beverages without affecting the taste or appearance. These nanoparticles encapsulate the nutrients and carry them through the stomach into the bloodstream. Researchers are using silicate nanoparticles to provide a barrier to gasses, or moisture in a plastic film used for packaging to reduce food spoiling or drying out. Zinc oxide nanoparticles are incorporated into plastic packaging to arrest UV rays providing anti bacterial protection and improve the strength and stability of the plastic film.
Nanosensors are being developed to detect bacteria and other contaminates, such as salmonella at a packaging plant. This will allow for frequent testing at a much lower cost than sending samples to a lab for analysis. This point-of-packaging testing, if conducted properly, has the potential to dramatically reduce the chance of contaminated food reaching grocery store shelves. Research is also being conducted to develop nanocapsules containing nutrients that would be released when nanosensors detect a vitamin deficiency in the human body. Basically this research could result in a super vitamin storage system in the body that delivers the nutrients needed. Interactive foods have been developed for choosing the desired flavor and color. Nanocapsules that contain flavor or color enhancers are embedded in the food; inert until a hungry consumer triggers them.
Researchers are also working on pesticides encapsulated in nanoparticles that release pesticide within an insect's stomach, minimizing the contamination of plants themselves. Another development being persued is a network of nanosensors and dispensers can be used throughout a farm field to recognize when a plant needs nutrients or water, before there is any sign that the plant is deficient. The dispensers then release fertilizer, nutrients, or water as needed, optimizing the growth of each plant in the field.
11/13/10
By turning graphene into nanoribbons using V2O5 nanofibers as etching masks dramatically improves their memory storage density over silicon-based chips. By depositing V2O5 nanofibers on top of graphene and etching it with an argon ion beam, graphene nanoribbons with smoother edges of less than 20 nm wide can be produced.
Due to smoother edges, devices made from them have better performance characteristics. According to the researchers, the device produced from these graphene nanoribbons has a transition time three orders of magnitude shorter than those devices made from either carbon nanotubes or grapheme and key to the nanoribbon’s memory storage density is the small memory cell. The grapehene nanoribbons shrink these down to 10 nm scale.
They can be used as both static random access memories and nonvolatile flash memories cell for ultrahigh storage density applications and for digital logic gates
Due to smoother edges, devices made from them have better performance characteristics. According to the researchers, the device produced from these graphene nanoribbons has a transition time three orders of magnitude shorter than those devices made from either carbon nanotubes or grapheme and key to the nanoribbon’s memory storage density is the small memory cell. The grapehene nanoribbons shrink these down to 10 nm scale.
They can be used as both static random access memories and nonvolatile flash memories cell for ultrahigh storage density applications and for digital logic gates
11/13/10 0
Researchers of Oregon State University have discovered a new method to increase nanoparticle production rate to make nanotechnology products more commercially practical. This effort will make possible the production of improved sensors, medical imaging, electronics and solar energy or biomedical gadgets when the same strategy is applied to materials such as copper, zinc or tin. The production process is claimed to be more environmentally sensitive, use fewer solvents and less energy and cost. The new approach used a microreactor with new architecture that produced ‘undecagold nanoclusters’ hundreds of times faster than conventional ‘batch synthesis’ processes. Commercial production might be as simple as just grouping hundreds of these small devices together. The process has been used to create nanoparticles based on gold, but the same concept should be applicable to other materials as well, according to the scientists.
11/10/10
Nanoparticles have already became an indispensable material for industries because of their unique size dependent properties such as electrical, magnetic, mechanical, optical and chemical properties, which largely differ from those of their bulk materials. Nanoparticles have an extremely high tendency of adhesion and aggregation due to different surface structures and surface interactions. Hence it is necessary to control their dispersion/aggregation phenomena of nanoparticles in order to apply them into functional materials and products.It is still a challenging issue to control the stability of suspension with highly loaded nanoparticles or sus-pensions in organic media. Surface modification of nanoparticles is one of the mostly accepted methods to improve the dispersion stability. Surface structure can be designed based on the type of nanoparticles and the liquid media in order to modify the surface by polymeric surfactants or other modifiers to generate an effective repulsive force between nanoparticles.
The adsorption of polymeric dispersant is one of the simplest surface modification techniques to improve the dispersion stability of nanoparticles in liquid media.
Surface modification of the particle surface chemically is an also an useful technique to improve the stability of nanoparticles in various liquid media. The surface modification of nanoparticles by silane coupling agents is also useful to improve the dispersion stability in organic media.
Mechanical milling method and other physical techniques such as ultrasonic dispersion can be applied to redisperse various nanoparticle into liquid media by the simultaneous processing of the surface modification cited above and the bead milling.
On preparing nanoparticles dispersible in aqueous or high-polar solvents, a polyol method is also widely accepted by many researchers.
Based on abovementioned methods, various nanoparticles including metals, oxides, sulfides, and fluorides that are redispersible into many solvents can be synthesized by in-situ surface modification techniques.
11/10/10 0
11/9/10
Unlike typical air cleaners, nanotechnology air purifier eradicates air impurities instead of collecting them, eliminating the need to replace costly filters, and unlike commonly available ionic units, the purifier does not produce harmfully elevated ozone levels. The purifier uses nanotechnology, the same technology used to sanitize instruments and surfaces in hospitals, the air purifier being able to kill off 99% of mold spores, bacteria, pollen, and viruses. It dissolves organic vapors and gasses, such as those found in paint, insecticides, and adhesives. The integrated titanium dioxide crystals and a fluorescent bulb produce oxidizing hydroxyl radicals that destroy airborne pollutants as air is drawn into the unit.
The Filterless Nanotechnology Air Purifier is offered by Hammacher Schlemmer to improve the quality of the air in rooms and kills off the impurities in the air.
11/9/10 3
Nanotechnology Victoria (NanoVic), a company committed to the development and promotion of nanoscience in Victoria engaged Kennovations to generate concepts for fun, educational and safe objects which both utilise and promote the practical application of nanotechnology.
NanoVic decided on two concepts as their ‘mascots - ‘Eddie the Echidna’ and ‘NanoMan’. ‘Eddie the Echidna’ features quills of NiTinol Shape Memory Alloy which react to specific environmental temperature changes. In general shape memory alloy (SMA, smart metal, memory metal, memory alloy, muscle wire, smart alloy) is an alloy that "remembers" its original, cold-forged shape: returning the pre-deformed shape by heating. This material is a lightweight, solid-state alternative to conventional actuators such as hydraulic, pneumatic, and motor-based systems. Shape memory alloys have applications in industries including medical and aerospace.Nickel Titanium (also known as Nitinol) is the unique class of materials known as shape memory alloys. A thermoelastic martensitic phase transformation in the material is responsible for its extraordinary properties.
But here the incorporation of shape memory alloy acts depending on the temperature .Below 15°C the 'Eddie the Echidna' quills can be laid flat or messed about in any position, but with the application of heat over 15°C will instantly spring back into the spiked position. ‘NanoMan’ is a super-hero polyurethane key ring featuring a battery powered UV LED backpack and chest plate impregnated with UV reactive nano-polymers.
(Source:www.hotfrog.com.au/Companies/Kennovations-Ind.)
Nanoscale Physics Research Laboratory, The University of Birmingham has developed a "Nanoman". The "Nanoman" was created by focussed electron beam deposition on the tip of an STM - an illustration of 3D nanostructure fabrication with a precision of 10nm.
11/8/10
Types of nano claySigma-Aldrich produces and markets the following : Halloysite nanoclay, Nanoclay, hydrophilic bentonite, Nanoclay, surface modified containing 0.5-5 wt. % aminopropyltriethoxysilane, 15-35 wt. % octadecylamine, surface modified containing 25-30 wt. % methyl dihydroxyethyl hydrogenated tallow ammonium, surface modified containing 25-30 wt. % octadecylamine, surface modified containing 25-30 wt. % trimethyl stearyl ammonium, surface modified containing 35-45 wt. % dimethyl dialkyl (C14-C18) amine.
Applications
The demand of nano clay is very high in the high polymer composite material market. Nano clay can also be applied in various kinds of resins, painting, thermal insulation material, plastic and ceramic materials to enhance functions and value. Nano clays provide excellent heat/ sound /electricity insulation and acid-proof function. nano clays offer high strength to the finished products.
Properties:
High wear -resistant , good durability
Heat stability
Excellent flame retard property
Low viscosity, excellent dispersing, great fluidity
Control gloss effectively
11/8/10 0
Nanoclay is a surface modified montmorillonite clay, or masterbatche containing modified clay, that is utilized to make a nanocomposite.
Structure
Nanoclays are nanoparticles of layered mineral silicates. Silica is the dominant constituent of clays, with Alumina being essential, as well. Clays have a layered structure consisting of 2 types of sheets, the silica tetrahedral and alumina octahedral sheets. The silica tetrahedral sheet consists of SiO4 groups linked together to form a hexagonal network of the repeating units of composition Si4O10. The alumina sheet consists of two planes of close packed oxygen’s or hydroxyls between which octahedrally coordinated aluminum atoms are imbedded in such a position that they are equidistant from six oxygens or hydroxyls. The two tetrahedral sheets sandwich the octahedral, sharing their apex oxygens with the latter. These 3 sheets form one clay layer.
Polymer grade (PG) montmorillonites are high purity aluminosilicate minerals sometimes referred to as phyllosilicates. They are intended for use as additives to hydrophilic polymers such as polyvinylalcohols, polysaccharides and polyacrylic acids. When fully dispersed in these host polymers they create a new category of composite materials called nanocomposites.
Polymer grade (PG) montmorillonites are high purity aluminosilicate minerals sometimes referred to as phyllosilicates. They are intended for use as additives to hydrophilic polymers such as polyvinylalcohols, polysaccharides and polyacrylic acids. When fully dispersed in these host polymers they create a new category of composite materials called nanocomposites.
Nanoclay is a type of material made using nanotechnologies, it is a surface modified montmorillonite clay, or masterbatche containing modified clay that is utilized to make a nanocomposite. Nanoclays are generically referred to as "intercalates" in patent literature.
Nanoclay origin
Natural clays are most commonly formed by the in situ alteration of volcanic ash. Nanoclay is made of volcanic minerals, or smectite, structured into plates of approximately one nanometer thick but several hundred nanometers in width and length. Nanoclays are natural nanomaterials that occur in the clay fraction of soil, among which montmorillonite and allophane are the most important species. Montmorillonite is a crystalline hydrous phyllosilicate (layer silicate). Organically modified montmorillonites or ‘organoclays' were formed by intercalation of quaternary ammonium cations. Allophane is a non-crystalline aluminosilicate derived from the weathering of volcanic ash.
Depending on chemical composition and nanoparticle morphology, nanoclays are organized into several classes such as montmorillonite, bentonite, kaolinite, hectorite, and halloysite. Organically-modified nanoclays (organoclays) are an attractive class of hybrid organic-inorganic nanomaterials.
11/7/10
Nanotechnology is one of the top-ranked subjects in the academic and research fields. It offers lot of oppurtunities for higher studies, research and employment. Here is a brief list of courses offered, list of institutes, course content and oppurtunities in the field of nanoscience and technology.
Courses
Available nanotechnology courses are:
Courses
Available nanotechnology courses are:
M. Tech. degree course (two-year)M.Sc. degree course in nano sciences/ industrial nano science (two-year)
M.Tech. degree course in nano technology (Five-year integrated)
M. Tech. programme in nanotechnology (two-year full-time)
M.Tech. degree in nano medical science which is rare in India.
Institutes offering the courses
Institutes offering the courses
The Amity Institute of Nanotechnology in Noida and Jaipur (Integrated M.Tech. course in nanotechnology, M.Sc. degree course in industrial nano science)
Vellore Institute of Technology, Vellore, M. Tech. degree course in nanotechnology.
Sastra University, Thanjaur, Tamil Nadu (Integrated M.Tech. degree course in medical nanotechnology).
The National Institute of Technology (NIT), Calicut (M.Tech. in nanotechnology)
The Indian Institute of Technology, Roorkee (M. Tech. nanotechnology) (http://www.iitr.ac.in/)
The Department of Physics of Jamia Millia Islamia, New Delhi (M. Tech.in nanotechnology)
Anna University, Coimbatore, (http://www.annauniv.ac.in/) M. Tech. degree course in nanotechnology.
Department of Physics and Astrophysics, University of Delhi (http://www.du.ac.in/) M. Tech. degree course in nanoscience and nanotechnology.
Bharathiar University, Coimbatore (http://www.b-u.ac.in/) M.Sc. degree course in nano science and technology.
Periyar Maniamma University, Vallam, Thanjavur (http://www.pmu.edu/) M. Tech. degree course in nanotechnology.
SRM University, Kattamkulathur (http://www.srmuniv.ac.in/) MS degree course in nano science.
Amrita Institute of Medical Science, Kochi (http://www.amrita.edu/), M.Tech. degree course in nano medical sciences and technology.
Kalasalingam University, Anand Nagar, Krishnankoil, Virudunagar, Tamil Nadu (http://www.kalasalingam.ac.in/) M.Tech. degree course in nanotechnology.
Birla Institute of Technology, Mesra, Ranchi, ME degree course with nanotechnology as an elective subject.
Delhi University, Banaras Hindu University and Indian Institute of Science (IISc.), Bangalore, have research facilities in nanotechnology leading to Ph.D.
General curriculum
Department of Physics and Astrophysics, University of Delhi (http://www.du.ac.in/) M. Tech. degree course in nanoscience and nanotechnology.
Bharathiar University, Coimbatore (http://www.b-u.ac.in/) M.Sc. degree course in nano science and technology.
Periyar Maniamma University, Vallam, Thanjavur (http://www.pmu.edu/) M. Tech. degree course in nanotechnology.
SRM University, Kattamkulathur (http://www.srmuniv.ac.in/) MS degree course in nano science.
Amrita Institute of Medical Science, Kochi (http://www.amrita.edu/), M.Tech. degree course in nano medical sciences and technology.
Kalasalingam University, Anand Nagar, Krishnankoil, Virudunagar, Tamil Nadu (http://www.kalasalingam.ac.in/) M.Tech. degree course in nanotechnology.
Birla Institute of Technology, Mesra, Ranchi, ME degree course with nanotechnology as an elective subject.
Delhi University, Banaras Hindu University and Indian Institute of Science (IISc.), Bangalore, have research facilities in nanotechnology leading to Ph.D.
General curriculum
The curriculum deals with topics related to the fundamentals and application of the subject with a focus on emerging areas in nano science and nanotechnology. The course contents include fundamental and applied subjects such as physics of materials, thermodynamics of nano materials and systems, mechanics of finite size elements, micro-scale and nano-scale heat transfer, nano-sized structures, experimental techniques in nanotechnology and micro electro mechanical systems and a variety of elective subjects ranging from computational nanotechnology to composite materials. Laboratory courses dealing with production and applications of nano particles, nano fluids and nano composites will also be offered as part of the curriculum .
Oppurtunities
Oppurtunities
The specialisation in nanotechnology holds a very high potential for employment in research and development, academics and industries. Those who successfully complete the M. Tech. programme can go for research programmes leading to Ph.D. in nanotechnology and can find jobs as nanotechnologists, specialists or scientists. The areas where a a notechnologist can seek employment include biotechnology, agriculture, food, genetics, space research, medicine and so on. Job opportunities are also available in National Physical Laboratory, Indian Institute of Astrophysicsed and other research labs. Candidates with Ph.D. can also join as faculty members in colleges.
General eligibility
General eligibility
BE/ B. Tech. holders in relevant discipline with at least 60 per cent marks in aggregate along with a valid GATE score for admission to the M. Tech. programme in nanotechnology (http://www.nitc.ac.in/)
M.Sc. degree in physics /chemistry (with mathematics up to at least Bachelor's level) / electronics science / material science / electronic instrumentation with at least 55 per cent marks in aggregate
Bachelor's degree in electrical/ mechanical/ electronics and communication/ computer engineering / instrumentation / computer science with not less than 60 per cent marks
Degree in electrical, mechanical, electronics and communication or computer engineering or M.Sc. degree course in biotechnology, computer science, physics, chemistry, electronic science, material science, electronic instrumentation
B.Tech. or B.Sc. degree in physics, chemistry, biotechnology and electronics (http://www.amity.edu/).
Source: The Hindu, Education Plus Chennai, dt Nov 8, 2010
M.Sc. degree in physics /chemistry (with mathematics up to at least Bachelor's level) / electronics science / material science / electronic instrumentation with at least 55 per cent marks in aggregate
Bachelor's degree in electrical/ mechanical/ electronics and communication/ computer engineering / instrumentation / computer science with not less than 60 per cent marks
Degree in electrical, mechanical, electronics and communication or computer engineering or M.Sc. degree course in biotechnology, computer science, physics, chemistry, electronic science, material science, electronic instrumentation
B.Tech. or B.Sc. degree in physics, chemistry, biotechnology and electronics (http://www.amity.edu/).
Source: The Hindu, Education Plus Chennai, dt Nov 8, 2010
11/7/10 1
The largest single usage of organoclays over recent years has been in the manufacture of polymer-clay nanocomposites. These organic–inorganic hybrid materials show superior mechanical, thermal and gas-barrier properties and water treatment. Potential benefits include increased mechanical strength, decreased gas permeability, superior flame-resistance, and even enhanced transparency when dispersed nanoclay plates suppress polymer crystallization. Organoclay is used in polymer nanocomposites and in the ink formulation to adjust the consistency of printing inks. It is used to thicken the lubricating oils to produce especially high temperature resistant lubricating greases with good working stability and water resistance. In cosmetics, organoclays are used to enhance good colour retention and coverage for nail lacquers, lipsticks and eye shadows. Nanoclays are also used as rheological modifiers in paints, inks, grease and cosmetics. Nanoclays have great potential as compared to polymer and carbon nanotubes for drug delivery applications. The organoclay treatment of waste water yields superior clarity and oil and grease removal when compared to other treatments. It also removes humic acid which is one of the common contaminant in potable water. Organoclays operate via partitioning phenomena and have a synergistic effect with activated carbon and other unit processes such as reverse osmosis. Nanoclays are known to enhance properties of many polymers giving them better clarity, stiffness, thermal stability, barrier properties to moisture, solvents, vapors, gases and flavors, reduced static cling and UV transmission in film and bottles, improved chemical, flame, scratch resistance, and dimensional stability in injection molded products. The properties of polypropylene spun bond fabrics can be enhanced by inclusion of small levels of nanoclays. Nanoclay is a wide-spectrum mycotoxin binder. Nanotechnology is now being used in the animal industry to improve the natural qualities of clay, leading the way to healthier and more productive animals. Consisting of nanosize (3.5–5.0 nm) hollow spherules, allophane is a suitable support material for enzyme immobilization. Allophane is also effective at adsorbing phenolic compounds and colour from kraft mill effluents and phosphate from water and wastewater. Organoclays are also useful in pollution controlCommercial brands
Nanomer®, Sigma-Aldrich and Cloisite® are the popular nanoclays available in the market. Nanomer® is a nanoclay product developed by Nanocor/AMCOL International Corporation anomer® nanoclay, and is supplied as a free-flowing, micronized powder. When Nanomer nanoclays are dispersed in a polymer matrix, they form a near-molecular blend called a nanocomposite. Cloisite® nanoclays are produced by Southern Clay Products, Inc., of Texas, USA. Sigma-Aldrich, in collaboration with the Nanocor Corporation, offers a range of montmorillonite nanoclay products with different organic modifications optimized to be compatible with various polymer systems.
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