In this work, we report the feasibility of the silver nanowire (AgNW) foils as highly-sensitive, reproducible and facile detection tools for surface-enhanced Raman spectroscopy (SERS) applications. These flexible and free-standing AgNW foils, fabricated by vacuum filtration method following a modified polyol synthesis of AgNWs, are adequately structured for both biological specimen filtering and trace amount of molecule detection simultaneously. The compatibility of AgNW foil in SERS is investigated by using a Raman active molecule of different steric volumes across the filter cross-section. We have shown that AgNW foils exhibit extremely strong SERS activity with detection limit up to 10-9 M of crystal violet (CV) molecule with 20% variation over ~cm2, revealing reliable homogeneity of the acquired signal. While naturally occurring polyvinylpyrrolidone (PVP) layer during polyol synthesis contribute to controlled aggregation, oxidation prevention, and size - shape control purposes, it also creates a major challenge for obtaining enormous enhancement factors. However, controlled thickness of aluminum oxide (Al2O3) coating on PVP@AgNW foils affords to achieve higher enhancement factors than the uncoated ones. What is interesting is that the maximum intensity is achieved from two cycles of Al2O3 deposited on AgNW foils. This is attributed to the two different origins: first, a higher adsorption affinity of CV molecules to Al2O3 layer than PVP layer; second, tunneling barrier formation against quantum tunneling effects.
Absorption of the light by a solar cell can be improved significantly by light trapping structures formed on the front
surface of the device. In particular, thin crystalline and amorphous solar cells are expected to benefit from the improved
light absorption in a region closer to the surface of the cell. Recently, we have shown that vertically aligned silicon (Si)
nanowires formed on flat (100) Si wafer surface by metal assisted etching can effectively be used for this purpose. In this
paper we present demonstration of nanowire application to industrial size solar cell system and a comparison between
flat and pyramid textured Si wafers. Standard procedures were followed to fabricate solar cells with and without Si
nanowire process on mirror like and pyramid textured Si wafers. The dependence of the solar cell parameters on the
process parameters was studied systematically. Reflection spectra showed successful light trapping behavior on the
surface of the cells. In all samples, we have obtained excellent current-voltage (I-V) characteristics with high fill factors.
However, the efficiency of the cells was found to decrease with the etch duration. This can be attributed to the increased
recombination along the nanowires or increased surface area due to the roughening of the surface after etching process.
Zinc oxide nanowire networks are attractive as alternatives to organic and amorphous semiconductors due to their wide bandgap, flexibility and transparency. We demonstrate the fabrication of thin film transistors (TFT)s which utilize ZnO nanowires as the semiconducting channel. These thin film transistors can be transparent and flexible and processed at low temperatures on to a variety of substrates. The nanowire networks are created using a simple contact transfer method that is easily scalable. Apparent nanowire network mobility values can be as high as 3.8 cm2/Vs (effective thin film mobility: 0.03 cm2/Vs) in devices with 20μm channel lengths and ON/OFF ratios of up to 104.
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