No abstract

Iron pyrite (FeS2) nanostructures are of considerable interest for photovoltaic applications due to improved material quality compared to their bulk counterpart. As an abundant and nontoxic semiconductor, FeS2 nanomaterials offer great opportunities for low-cost and green photovoltaic technology. This paper describes the fabrication of FeS2 nanowire arrays via sulfurization of iron oxide nanotubes at relatively low temperatures. A facile synthesis of ordered iron oxide nanotubes was achieved through anodization of iron foils. Characterization of the iron sulfide nanowires indicates that pyrite structures were formed. A prototype FeS2 nanowire photoconductor demonstrates very high responsivity (>3.0 A/W). The presented method can be further explored to fabricate various FeS2 nanostructures, such as nanoparticles, nanoflowers, and nanoplates.

Synthesis of GaN nanowires via metal-assisted photochemical electroless etching.

The achievement of H 2 detection, up to 25 ppm, at room temperature using sulfur-treated, platinum (Pt)-decorated porous GaN is reported in this study. This achievement is attributed to the large lateral pore size, Pt catalyst, and surface treatment using organic sulfide. The performance of H 2 -gas sensors is studied as a function of the operating temperature by providing an adsorption activation energy of 22 meV at 30 ppm H 2 , confirming the higher sensitivity of the sulfide-treated Pt–porous GaN sensor. Furthermore, the sensing response of the sulfide-treated Pt–porous GaN gas sensor increases with the increase in porosity (surface-to-volume ratio) and pore radii. Using the Knudsen diffusion–surface reaction equation, the H 2 gas concentration profile is simulated and fitted within the porous GaN layer, revealing that H 2 diffusion is limited by small pore radii because of its low diffusion rate. The simulated gas sensor responses to H 2 versus the pore diameter show the same trend as observed for the experimental data. The sulfide-treated Pt–porous GaN sensor achieves ultrasensitive H 2 detection at room temperature for 125 nm pore radii.