SUNLIGHT TO GENERATE SUPER-GREEN FUEL

In continuation with the previous article, in a breathtaking invention by the four chemists at the University of Rochester, hydrogen, which is considered to be the environmental friendly fuel in future, is thought to be produced from water using sunlight. It is also considered to be an alternative fuel source and that’s why people are trying to synthesize hydrogen through various means. In past researchers have devised many ways to produce this future fuel, but not in an environmental friendly way. This time around, they have successfully solved this problem.

"People have used sunlight to derive hydrogen from water before, but the trick is making the whole process efficient enough to be useful", commented Kara Bren, professor in the Department of Chemistry.

Bren and the rest of the Rochester team—Professor of Chemistry Richard Eisenberg, and Associate Professors of Chemistry Todd Krauss, and Patrick Holland—will be working on artificial photosynthesis, which uses sunlight to carry out chemical processes much as plants do. But people have also tried out this process; what makes the Rochester approach different from previous attempts to use sunlight to produce hydrogen from water, is that the device they are preparing is divided into three steps. Each step can be modulated, manipulated and optimized according to our need far more easily than other methods.

FIRST STEP

It uses visible light to create free electrons. A complex natural molecule called a chromophore that plants use to absorb sunlight will be re-engineered to efficiently generate reducing electrons.

SECOND STEP

In the next stage a membrane will be suffused with carbon nanotubes to act as molecular wires so small that they are only one-millionth the thickness of a human hair. To prevent the chromophores from re-absorbing the electrons, the nanotube membrane channels take the electrons away from the chromophores and push toward the third section.

THIRD STEP

In the third module, catalysts put the electrons to work forming hydrogen from water. The hydrogen can then be used in fuel cells in cars, homes, or power plants of the future.

By separating the first and third modules with the nanotube membrane, the chemists hope to isolate the process of gathering sunlight from the process of generating hydrogen. This isolation will allow the team to maximize the system's light-harvesting abilities without altering its hydrogen-generation abilities, and vice versa. Bren says this is a distinct advantage over other systems that have integrated designs because in those designs a change that enhances one trait may degrade another unpredictably and unacceptably.

NOW NANOSTRUCTURE MAKES IDEAL BATTERY

Since two decades, the whole world is concentrating on the pollution and its irreversible impact on the environmental balance. One of the prime factors that spur the environmental degradation is the pollution, created due to produce electricity. Again nanotechnology with all its uniqueness in its ability to solve any kind of technical problem comes up with a method in which environmentally friendly battery could be made by the nanostructure of algae.

Gustav Nystrom( a doctoral student in nanotechnology) who is in the team of Uppasala University in Sweden opined that the distinctive cellulose nanostructure of algae can serve as an effective coating substrate for use in environmentally friendly batteries.

According to the researchers, the algae have a special cellulose structure characterized by a very large surface area and they have coated this structure with a layer of conducting polymer. The battery almost weighs nothing and that has set new charge-time and capacity records for polymer-cellulose-based batteries.

Pharmaceutical applications of the cellulose from Cladophora algae have been explored for a number of years. This type of cellulose has a unique nanostructure, entirely different from that of terrestrial plants, that has been shown to function well as a thickening agent for pharmaceutical preparations and as a binder in foodstuffs. It is because of this huge surface area that the possibility of energy-storage applications has been raised.

This type of research creates new possibilities for large-scale production of environmentally friendly, cost-effective, lightweight energy storage systems.

INTEGRATION OF NANOWIRES WITH CMOS SEMICONDUCTOR CHIPS

For fabrication of CMOS semiconductor chips optolithographic process has widely been used since the dawn of fabrication. It has proved its worth over the years and successfully outsmarts the other technologies which have been used in the silicon based industry.

Present CMOS chip fabrication process can go further down may be to 10 nm. To fabricate CMOS chips of such a size range with such high precision and accuracy call for expensive equipments. The best way to go further down is to deviate from optolithographic process to self aligning nano elements called nanowires or nanotubes. Semiconductor industry is not ready to abruptly dump the lithography based equipment for nanowire based process due to cost and strategic reasons.

That’s why researchers are working out a smooth transition from the present CMOS to nano-element based by initially combining both methods and use much of the present technologies for some time at least in moving over to a totally different process.

Silicon, being abundant and most affordable metal will stay during the transition. So the challenge for the nano-technology researchers is to commercialize their Nano technology idea by effectively using present CMOS process, Silicon and its friends.

Few breakthrough in this direction from researchers around the world were noticed:

France based nano technology researcher Leti got step closer to integrating Silcon nanowires into traditional CMOS semiconductor chip making process.

Leti researchers have created silicon nanowire at temperature of 400˚C by using a copper-based catalyst using a method different from normal. The highlight of the research is that they could generate nano devices at low temperature of 400˚C which is far less than what others are achieved. Most of Silicon based nanowires were made in the temperature of 600˚C to 1000˚C inside a furnace. Another highlight is that researchers have created nanowires on oxidized metals.

Achieving at temperature convenient for making CMOS semiconductor chips and on oxide material brings Leti close to integrating nanowires on CMOS semiconductor chip. In this way future System-on-Chip (SoC) can house sensors and other nanotechnology based components mainly the Optoelectronic devices.

University of California, Berkeley has put on its website a report of its research work of growing Au-catalyzed vapor-liquid-solid nanowire via metal-organic chemical vapor deposition. It state "The nanoneedles grow on GaAs, silicon and sapphire substrates and exhibit bright room-temperature photoluminescence. The growths are conducted at 380 to 420 °C, making the process ideal for silicon-CMOS integration".

In another development researchers at Stanford University have developed method of stacking and crystalline semiconductor layers that sets the potential for three-dimensional microchips.

Due to their high surface-to-volume ratio, nanowires are highly suitable for the electrical detection of chemical or biological substances, converting solar to electrical energy and in developing high energy storing batteries. The immediate applications of nanowire integrated CMOS chips are in health, environment and solar energy conversion. Consequently energy generation will become far easier.