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Showing posts from July, 2012

High efficiency graphene solar cells

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Graphene Graphene is a sheet of carbon atoms arranged in a honeycomb-like lattice just one atom thick, having a number of unique electronic and mechanical properties. This is because of the fact that electrons whiz through graphene at extremely high speeds, behaving like "Dirac" particles with little resistance. Graphene is also transparent to light due to its Dirac electrons and can absorb light of any color. Solar cells Researchers so far have made solar cells from graphene but the power conversion efficiency is quite low at around 1.9%. But researchers at the University of Florida in Gainesville have succeeded in fabricating the most efficient graphene-based solar cells ever by adding an organic dopant to the graphene layer in the devices. The power conversion efficiency of the new solar cells reaches nearly 9%, compared to just fewer than 2% for cells that use undoped graphene. Structure These cells are made of graphene sheet doped with the organic compound (trifluorometh

Nanogenerator

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Pyroelectric effect A lot of heat energy is lost to the environment by various devices ranging from computers to cars to long-distance electric transmission lines. Heat can be converted to electricity using the pyroelectric effect. This effect was first observed by the Greek philosopher Theophrastus when a gemstone tourmaline produced static electricity and attracted bits of straw when heated. This is because heating and cooling rearrange the molecular structure of certain materials, including tourmaline, and create an imbalance of electrons which result in the generation of electric current. Nanogenerator A device called pyroelectric nanogenerator has been designed to harvest waste heat to produce electricity by researchers of Georgia Tech. The research group applied this ancient principle to make a nanogenerator (NG) that could take advantage of time-dependent temperature change of a heat source to generate electricity. Researchers used nanowires out of zinc oxide in an array of sho

Nanotechnology in food and beverage packaging

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There has been a great progress in the field of packaging nanotechnology which impacts every field of science as well as in our daily life. The nanoscale materials play a very important role in the packaging of electronic and photonic devices to packaging of health products to food. Nanotechnology in packaging Nanotechnology is taking food and beverage packaging technologies to new heights. Applications in nano-enabled packaging include development of improved tastes, color, flavor, texture and consistency of foodstuffs, increased absorption and bio-availability of nutrients and health supplements, new food packaging materials with improved mechanical, barrier and antimicrobial properties, and nano-sensors for traceability and monitoring the condition of food during transport and storage. Among active technologies in the current market, oxygen scavenger, moisture absorbers and barrier packaging represent more than 80% of marketed technologies. Foe example, a “nano-film” that when appli

Nonconductors conduct current at nanoscale

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Nonconductors Conductors effectively transmit electricity, and insulators or dielectrics do not, unless they are subjected to extremely high voltage leading to dielectric breakdown due to extreme heating and damage. Nano level phenomenon Researchers at University of Michigan have discovered that at the nano scale nonconductors can allow electric current to pass non destructively through a sliver of glass, which is not usually a conductor. At nano scale dielectric is made exceedingly thin to achieve the breakdown with modest voltages that even batteries can supply as heat is dissipated extraordinarily quickly. Researchers call these conducting nano scale dielectric slivers as liquid glass electrodes. These electrodes are fabricated with a femto second laser that emits light pulses only quadrillionths of a second long. Integral glass electrodes These devices need a power source to operate, and mostly rely on wires to route the power, but it is often difficult to insert wires into the tin

Nano-heterojunctions for solar cells

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Solar cell solar cells tap sunlight and converts into electricity. Worldwide, the contribution of solar electricity is higher due to many installed solar modules. Both the potential and gap in solar energy utilization by solar  cells are enormous. Semiconductors serve as the light absorber to convert photons into electron-hole pairs, and the internal electric field. The fundamental processes in solar cells are light absorption and charge separation. Lifetime of minority carrier and carrier  mobility are  critical for high efficiency. The record  efficiencies of commercial-size cells range between 12% and 20%. The current best efficiency of inorganic single-junction solar cells is 20-25% and it is almost saturated during the last decade. Inorganic solar cells Solution-processed inorganic solar cells based on colloidal semiconducting quantum dots and nanocrystals show much promise because they can absorb light over a wide spectrum of wavelengths thanks to the fact that the bandgaps in qu

Nanoscale dielectrics

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Scientists have manipulating materials such as nanoparticles, single molecules and atoms, in their natural environment by using new generation microscopes to explore the morphology of nanoscale objects. But there are still major hurdles to overcome in measuring the mechanical, chemical, electrical and thermal properties that make each object unique. Scientists working with biological complexes at the nanoscale use chemical labeling by incorporating a visible substance, such as fluorescent dye, into the target object to detect its presence and physical distribution often giving misleading results. Dielectrics Dielectric materials of nanoscale dimensions have aroused considerable interest. For examples in the semiconductor industry the thickness of gate oxide dielectric material is reaching nanoscale dimensions and the high energy density capacitor industry is currently considering dielectric composites with a polymer host matrix filled with inorganic dielectric nanoparticles or polariza