Nanotechnolgy topics widely discussed in 2010

Nanotechnology applications are wide and range from computer memory storage to sunscreens since nanomaterials currently in existence exhibit various physical, chemical, mechanical, optical, magnetic and biological properties, as well as different internal/external structures. Because scientists and researches in this new field have very diverse backgrounds, and are working on different applications, new discoveries emerge in the field of nanotechnology.

There has been a variety of hot topics discussed and reported in the media in the year 2010 ranging from cleaning up drinking water, simplifying transistors, improving energy storage, upgrading the manufacture of dye-sensitized solar cells and finding a better way to make gold nanoparticles. Few among the most important topics discussed are outlined below.

1. Arsenic removal using nanotechnology

Arsenic in drinking water is a huge problem in many areas of South Asia and the western US. The elevated level of drinking-water arsenic has seen massive epidemics of arsenic poisoning in recent years. Arsenic can be removed from drinking water by using activated carbon or precipitating it out with iron minerals, such as iron oxides such as magnetite (Fe3O4) nanocrystals. However, such particles cannot be used in large water bodies such as rivers or other environments where water flows, because of their small size and the fact that magnetite rapidly oxidises when exposed to the atmosphere.

Researchers in Korea have recently overcome the latter problem by combining iron oxides with carbon and carbon nanotubes, and graphene-based materials such as graphene oxide. The magnetite-RGO composite can be dispersed in water and after adsorbtion of arsenic, it can quickly be removed using a permanent hand-held magnet (with a strength of 20 mT) within a fraction of a minute.

2. Nanowire for Junctionless transistors

Transistors are made so tiny to reduce the size of sub assemblies of electronic systems and make smaller and smaller devices, but it is difficult to create high-quality junctions. In particular, it is very difficult to change the doping concentration of a material over distances shorter than about 10 nm. Researchers in Ireland have succeeded in making the first junctionless transistor having nearly "ideal" electrical properties. It could potentially operate faster and use less power than any conventional transistor on the market today. The device consists of a silicon nanowire in which current flow is perfectly controlled by a silicon gate that is separated from the nanowire by a thin insulating layer. The entire silicon nanowire is heavily n-doped, making it an excellent conductor. However, the gate is p-doped and its presence has the effect of depleting the number of electrons in the region of the nanowire under the gate.
The device also has near-ideal electrical properties and behaves like the most perfect of transistors without suffering from current leakage like conventional devices and operates faster and using less energy.

3. Nanotechnology for supercapacitors

Graphene has, of course, made headlines throughout the scientific world because of the awarding of the Nobel Prize in Physics to two researchers at the University of Manchester in England who pioneered a way of isolating graphene by repeatedly cleaving graphite with adhesive tape. For years researchers have held out hope that graphene would be the material to pick up the mantle in the electronics industry when silicon hits its limits as the material of choice for making devices smaller, faster and cheaper.

A team of researchers at Georgia Institute of Technology claims to have made a significant advance in that area by developing a technique for creating nanometer-scale graphene ribbons without rough edges.Researchers in the US have made a graphene-based supercapacitor that can store as much energy as nickel metal hydride batteries but which can be charged or discharged in just seconds or minutes. The new device provides a specific energy density of 85.6 Wh/kg of electrode weight at room temperature and 136 Wh/kg at 80 °C. These are the highest ever energy values reported for electric double layer super capacitors based on nano-carbon materials. The new device has electrodes made of graphene mixed with 5wt% Super P (an acetylene black that acts as a conductive additive) and 10wt% PTFE binder. This new technology makes for an energy storage device that stores nearly as much energy as in a battery but which can be recharged in seconds or minutes.

4. Quick synthesis of stable gold nanoparticles

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.

Green principles can be applied to exploit greener nano-synthesis with the intention of producing risk-free nanoscale gold particles and to obtain phytochemically-derived reducing agents for the generation and stabilization of gold nanoparticles under nontoxic conditions, reduce the complexity of current methodologies and enhance their efficiency.

Quick synthesis

Researchers at the Norwegian University of Science and Technology (NTNU) have recently developed a new environmentally friendly route for synthesizing gold nanoparticles (AuNPs) in one step at room temperature. The product is highly stable, non-toxic, biocompatible, water-soluble, monodispersed and size-controllable. The gold particles are made in just a few minutes by simply adding sodium hydroxide to the reaction mixture. The chemical acts as an initiator for the reduction of HAuCl4 in aqueous solution in the presence of polyvinylpyrrolidone without the use of any reducing agent. To control the size of the AuNPs, the researchers simply adjust the PVP/HAuCl4 ratio. The PVP-stabilized AuNPs demonstrate remarkable in vitro stability in a wide range of ionic strength (0–30 M), temperature (4–100 °C), pH (4.4–13.5), various buffer solutions and physiological conditions. The generation of PVP-stabilized AuNPs has been found to be non-toxic as assessed through MTT (3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide) assays.

Also, the production strategy features several green concepts: the choice of friendly solvent, the selection of friendly benign and non-toxic reducing and capping agents, the one-step reaction at room temperature and a reaction time of just a few minutes.

5. Nanocages

Biomedical engineers have developed techniques to deliver tiny amounts of medicines like anticancer drugs to a specific target directly to a location in the body affected by say tumors, for example. Most of their work involves nanocapsules or hollow structures which carry the payload of medicines, the delivery of which can be controlled from outside the body.

Like many nanoparticles, quantum dots can be conjugated to antibodies, ligands or other targeting moieties to mediate specific interactions with cancer cells. Gold nanoparticles when irradiated with near-infrared light are capable of destroying tumors and particularly gold nanoshells are used to deliver little amount of heat to breast tumor cells already treated with radiation, boosting the destroying capacity of both therapies. The action is that nanoshells increase perfusion of tumors with oxygen and also focally disrupts the blood supply to tumors, both of which enhance the effectiveness of radiation. Nanoshells reduce the population of stem cells dramatically which were left without destroying by radiation alone. Gold nanoparticles and quantum dots are used to diagnose and treat cancer.

Nanocages

The nanocages are cubes of gold nanoparticles having sides of about 50 nm made with holes at each corner made using silver particles as a mold. The holes are plugged with strands of a smart polymer. When the strands are heated they collapse, opening the holes and allowing the drug inside nanocage to escape at the target. The polymer strands are heated using near-infrared rays from outside the body. Near-infrared wavelength rays are not greatly absorbed by the unaffected body tissues as they penetrate a couple of inches inside the body, but they are absorbed by nanogage made of gold.

6. Nanophobia

Nanophobia is the fear that nanomaterials used in one way or other can harm the body. This is based on the fear that as tiny nanoparticles can travel through tissue along blood vessels in the human body. If the nanoparticles are indestructible and accumulate in the organs and are not metabolized the organs may fail.

One school of scientists and consumer advocates claim that many industries are making nanotech products by adopting nanotechnology ahead of proper studies that have not yet proved whether regular ingestion, inhalation or dermal penetration of nanoparticles constitute a health or environmental hazard or not.

Nanotechnology incorporated products are already in the market and people are already exposed to nanoparticles. For example stoves and toaster ovens emit ultrafine particles of 2 to 30 nanometers size and researchers reporte that long-term contact with such appliances could constitute a large exposure to the nanoparticles.

There are products like nano pants, stain-resistant chinos and jeans whose fabric contain nano-sized whiskers that repel oil and dirt, and nanocycles made from carbon nanotubes that are stronger and lighter than standard steel bicycles, lotions and creams which use nanocomponents that may create a more cosmetically elegant effect.

In beauty products, dynamic nanoparticles could pose risks to the skin or, if they penetrate the skin, to other parts of the body. The personal care products that contain nano-size components constitute a health hazard, as it is also reported that exposure to nanoparticles such as titanium dioxide cause damage to the organs of laboratory animals and human cell cultures.

This being an argument, no rigorous clinical trials have been published showing that cosmetics with nanocomponents caused health problems as it is very difficult to get anything through the skin which is an very effective barrier.