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Large-scale synthesis of nanomaterials

Nano rods and wires
The synthesis of new nanomaterials made of particles, rods and wires is among the most active areas of research in science due to the unique properties of these materials compared to conventional materials made from micron sized particles. Large scale synthesis is a problem faced by the academic research labs. Researchers of Virginia Commonwealth University have used a simple, commercial microwave oven (by microwave irradiation) to develop a new method for the synthesis of nanomaterials that can control the dimensions and properties of nano rods and wires since microwave heating can provide significant enhancement in reaction rates. It is considered to e a fast and easy way to create highly versatile, tailored nanorods and nanowires. They can be used in medical applications, drug delivery, sensors, communications and optical devices.
Organic ligand-capped titanium dioxide (TiO2) nanocrystals
The traditional method of single phase preparation of titanium dioxide nanocrystals involves high reaction temperature, long reaction time, and difficulties to prepare with small sizes. This is difficult to do in large scale synthesis at labs.This problem has been overcome by Chineese researchers. Their process has the features of mild reaction conditions and is a simpler and easier with a shorter preparation period, thereby facilitating large scale production. According to the researchers the manufacturing method comprises the steps of using methyl titanate, ethyl titanate, n-propyl titanate, iso-propyl titanate, butyl titanate or titanium tetrachloride as a titanium source, and with capping by oleic acid or an organic capping agent. Reaction of the titanium source in an organic non-polar solvent with an aqueous alkaline substance solution in the interface at a temperature range of 25 to 280 degree. C. for 0.5 to 240 hrs produces a transparent sol containing titanium dioxide nanocrystals having particle diameters of 1-20 nm.Thus with the advantage of two-phase preparing method, a solution of titanium source in an organic non-polar solvent is reacted with an aqueous alkaline substance solution under an ambient pressure or a high pressure, titanium dioxide nanocrystals form nuclei and grow at the interface, while they are capped with the organic capping agent. The resultant titanium dioxide nanocrystals can be dispersed stably in an organic non-polar solvent.
In the metal oxides that are widely used in different areas, zinc oxide powders are important material for applications due to their unique optical, electrical, dermatological and antibacterial properties. Synthesis approaches of nano-ZnO are mainly divided into three kinds: the solid, the solution and the vapor phase methods. A direct precipitation reaction method which belongs to the solution phase method between zinc chloride and sodium carbonate anhydrous is given below. Zinc chloride(ZnCl2, purity 98.0% of chemical grade), sodium carbonate anhydrous(Na2CO3, purity 99.8%) and Ethanol absolute(CH3CH2OH, purity 99.7%) of analytical grade are used in the synthesis. Surfactant and 106 binder are used.The preparation of nano-ZnO according to the literature is done by direct precipitation method. ZnCl2 and Na2CO3 are dissolved in water and then the Na2CO3 solution is dropped into ZnCl2 solution, and this results in precipitation. This is then treated with ultrasonic vibration and aged for several hours. In order to remove salt, as-burnt powders are filtered and rinsed in distilled water and ethanol. Finally, the precursor is dried in oven at 80 deg.C for 4 h, and thermal treatment is done at 450 deg.C for 3 h to get nano-ZnO.

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