Metal Assisted Nanowire Growth for Silicon Nanowire/Amorphous Silicon Composite Solar Cell

Solar cells are photovoltaic devices that convert the energy of light to electricity by the photovoltaic effect. Crystalline silicon-based solar cells are the most dominant solar cells in the market today due to the high efficiency and relatively low cost. However, the cost of such solar cell is still high due to the large amount of material that is consumed in fabricating such a device. Polycrystalline/amorphous thin films and nanomaterial technologies have emerged to reduce the high cost of c-Si based solar cells and increase the efficiency. In this research, we combined these two technologies to propose and fabricate silicon nanowires (SiNWs)/amorphous Silicon (a-Si) composite solar cell structure at low temperatures using heavily doped polycrystalline silicon/glass as a substrate. Silicon Nanowire (SiNW) is one of the promising 1D semiconductor nanomaterial which has recently attracted significant attention due to its potential applications in many fields, including photovoltaic (PV) solar cells. SiNW is a term that is used widely to describe a rod with a diameter of between 1 to 100 nm and length of several microns. The vertical array geometry of such a device has great advantages in increasing the efficiency of solar cells due to its high light absorption and efficient light scattering. Replacing the silicon with polycrystalline silicon that was fabricated on glass substrate by means of aluminum induced crystallization method of amorphous silicon is considered a significant step in reducing the cost since glass is a cheaper material. In this research, heavily doped polycrystalline (p+ polySi/ITO/glass) silicon film was fabricated successfully by the means of aluminum induced crystallization of a-Si on ITO/glass substrate. Raman spectroscope, optical microscope, Hall Effect measurement, and SEM were used for the characterizing the (p+ polySi/ITO/glass). P-type SiNW were grown successfully in the PECVD system on silicon, a-Si/ITO/glass, and p+ polySi/ITO/glass substrates using Au nanoparticles as a catalyst at temperatures between (310 ˚C and 346 ˚C). It is to be noted that this temperature range is still lower than the eutectic temperature of Au-Si (363 ˚C). SEM and TEM systems were used to characterize the SiNW on c-Si and p+ polySi/ITO/glass substrates

Diffusive Dynamics of Biological Macromolecules in the Cytoplasm of Live Bacteria

Bacteria are small organisms that play important roles in our bodies and in maintaining our surrounding environment. However, bacterial infections are considered as one of the health diseases that threatens the lives of humans. Resistance of bacteria to antibiotics has made treating bacterial infections more challenging. With the emergence of many developed optical techniques, it has become possible to study various biological mechanisms of molecules inside these small organisms with high resolution and precise localization. In this research, single particle tracking photoactivation localization microscopy (sptPALM) technique was used to investigate the dynamics of fluorescent histonelike nucleoid-structuring proteins (H-NS) in live E. coli bacteria at normal conditions and different environmental conditions. It was found that the distribution of the diffusion coefficients of H-NS proteins was a power law. Moreover, the distribution of displacements of H-NS proteins followed a Pearson Type VII distribution rather than other distributions. Furthermore, the viscoelasticity of the bacterial cytoplasm was measured experimentally by calculating the complex modulus of the cytoplasm as a function of frequency. Accordingly, a transition was observed in the viscoelasticity of bacterial cytoplasm from a glass-like structure into liquid-like structure in the frequency domain. Moreover, the diffusive dynamics of H-NS proteins were probed in different lengths of bacterial cell. It was found that the diffusions of H-NS proteins became faster as the lengths of the bacterial cells increased. In this work, the effect of Ag+ ions on the diffusive dynamics of H-NS proteins in live bacterial cells were studied. The diffusions of H-NS proteins in live bacteria increased as the treatment time with Ag+ ions increased. In vitro technique, electrophoretic mobility shift assay (EMSA), was done to understand the reasons behind the faster motions of H-NS proteins upon the treatment with Ag+ ions. The result of this technique showed that Ag+ ions affected the binding of H-NS proteins to the DNA and made it weaker. Furthermore, the isothermal titration calorimetry technique was used to probe the direct interaction between the DNA and Ag+ ions. Bent DNA molecules were used to study the effect of Ag+ ions on the double-stranded DNA. The results showed that Ag+ ions interacted with DNA and caused a dehybridization of the double-stranded DNA into single-stranded DNA. Lastly, the effect of temperature stress on the diffusive dynamics of free cytoplasmic particles and binding proteins (H-NS) proteins in live and dead cells using (sptPALM) technique was studied. It was found that the diffusive dynamics of H-NS proteins became faster as the temperatures increased from 21 to 37 °C. Importantly, it was found that the non-thermal energy (ATP) contributed to the changes in the diffusion of H-NS proteins rather than the thermal energy in dead and live bacterial cells. Different results with the effect of temperature stress on the diffusive dynamics of free cytoplasmic particles were observed. It was found that the diffusion of the cytoplasmic particles became slower as the temperature increased from 21 to 37 °C, suggesting the effect of temperature on the viscosity of the bacterial cytoplasm