Gum Arabic (GA) collected from Acacia senegal trees was used with polyvinyl alcohol (PVA) to prepare of a series of biodegradable membranes doped and non-doped with potassium dichromate (K 2 Cr 2 O 7 ). Adding the K 2 Cr 2 O 7 to the GA/PVA blends slightly decreased their crystallinity index (CI) by about 2 %. Increasing the PVA concentration in the chromated GA/PVA blends was responsible for increasing the CI. Adding the K 2 Cr 2 O 7 to the pure GA solution modified its differential thermal behavior whereby the exothermic reactions occurred between 321°C and 433°C were disappeared. The K 2 Cr 2 O 7 increased the heat change drastically for all the bioplastic blends with the highest increase for the pure GA. Adding K 2 Cr 2 O 7 to the pure PVA increased the nanometric particle size (NPS) significantly. Increasing the PVA concentration in a blend had a greater effect than did the K 2 Cr 2 O 7 on the NPS. The buried bioplastic membranes in the control soil had different count and species of microbial communities. The numbers of bacteria and fungi in the initial soil sample were lower than those for chromated GA membranes and were greater than those for the chromated PVA. All bacterial and fungi species had growth ability and are expected to be detoxification tools of chromium ion-doped blends of GA and PVA leading to a green environment.

This work investigates the enhanced stability of organic solar cells (OSCs) fabricated with a hybrid hole-transport layer (HTL) incorporating vanadium pentaoxide (V2O5) nanoparticles in poly­(3,4-ethylenedioxythiophene):poly­(styrenesulfonate) (PEDOT:PSS). OSCs have been fabricated in controlled and ambient atmospheric conditions by employing a pristine PEDOT:PSS HTL and its hybrid variant. Stability and degradation analyses were carried out by using photovoltaic and X-ray photoelectron spectroscopy (XPS) measurements, respectively. Normalized photovoltaic characteristics showed that OSCs with hybrid HTL outperformed the pristine device and retained their performance as compared to their pristine counterparts when the fabrication was carried out in a nitrogen-filled glovebox and devices were tested after encapsulation for 7 days. However, OSCs that were fabricated and characterized in ambient air showed severe degradation in photovoltaic performance, mainly due to a drastic decay in the short circuit current and open circuit voltage for both device variants. Further, XPS was applied to probe the stability of HTL variants under aging in ambient air. The device instability was mainly ascribed to indium diffusion from the anode into the HTL, and its concentration increased from 0.4 to 2.8% within 250 h of ambient exposure of pristine HTL, while an insignificant increase was recorded in the indium content of the hybrid HTL. This confirms the remarkable reduction in indium diffusion brought about by the presence of V2O5 nanoparticles.

We provide compelling evidence that ring formation in solutions of thiol-passivated Au nanoparticles is driven by breath figure dynamics. A method for the controlled placement of rings of nanoparticles on a solid substrate, which exploits variations in substrate wettability to fix the positions of the submicrometer water droplets formed in the breath figure process, has been developed. This is achieved by heterogeneously patterning hydrogen-terminated silicon substrates with oxide regions that act as adsorption sites for the droplets. The droplets in turn template the formation of thiol-passivated Au nanoparticle rings during spin-casting from volatile solvents.

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We report solution processable hole transport layer (HTL) for bulk heterojunction organic solar cells (BHJ OSCs) based on varied concentration of graphene oxide (GO) in aqueous suspension. The effects of varied concentration of GO at 1, 2, and 4 mg/mL on the morphological, optical, electrical, and photovoltaic properties of the OSCs have been studied. Device with the lowest concentration and least thickness of GO showed most optimized performance with a power conversion efficiency (PCE) of 2.73%, as compared to the higher concentrations, where the PCE reduced to 0.67 and 0.22% for the devices with HTL of 2 and 4 mg/mL, respectively. The remarkable reduction in the device performance at higher concentrations is mainly attributed to a drastic decrease in the short circuit current that reduced from 8.14 mA/cm2 to 2.90 and 1.10 mA/cm2 at 2 and 4 mg/mL, respectively. Similarly, the increased series resistance (R s) from 6.89 Ω/cm2 to 9.54 and 11.51 Ω/cm2 has also reduced the device performance. Optical transmittance has been decreased from more than 85% to less than 80% in the overall wavelength region at higher concentrations. Both the insulating properties of GO at higher thickness of HTL due to high concentration and inhomogeneous surface characteristics lead to a decrease in the device performance.