Room temperature NO2 gas sensor based on stain-etched porous silicon: Towards a low-cost gas sensor integrated on silicon

High-performance PANI sensor on silicon nanowire arrays for sub-ppb NH3 detection

For industrial production and disease diagnosis, real-time detection of low concentrations of NH3 is crucial, necessitating a gas-sensitive sensor compatible with integrated processes and exhibiting excellent performance. Herein, we employed wet etching and rapid in-situ polymerization on silicon nanowire substrates to grow polyaniline fibers, thereby fabricating NH3 gas sensors with p-p heterojunction and three-dimensional network structures. Characterization and gas sensing performance testing were conducted. The results demonstrate the outstanding NH3 detection capabilities of the sensor, providing stable responses down to concentrations as low as 1 ppb, which indicates its LOD is one to two orders of magnitude lower than current similar products. It also exhibits verified selectivity and long-term reliability. The excellent sensing performance is attributed to the high surface area from the silicon nanowire structure and efficient synergy of p-p heterojunction. Additionally, the influence of doping types of the substrates and annealing process were explored. This work serves as a reference for the design of silicon-based gas sensors with high sensitivity, low detection limits, and extended operational lifetimes, suitable for deployment in commercial integrated monitoring systems.

TiO2 nanorods decorated Si nanowire hierarchical structures for UV light activated photocatalytic application

Water remediation techniques like photolysis have recently piqued the interest of many researchers due to water contamination resulting from heavy industrialization and urbanization. In the current work, as-synthesized TiO2 nanorod decorated vertically aligned silicon nanowire (SiNW) leads to a hierarchical morphological structure formation. The photocatalytic nature of the fabricated SiNW/TiO2 nanoheterojunction is examined by the dye degradation of textile pollutants like methylene blue (MB), rhodamine B (RhB), and eosin B (EB). The catalytic dye degradation investigations revealed that 4 h hydrothermal synthesis of TiO2 on the surface of SiNW (ST4) exhibited excellent catalytic behaviour. In the presence of H2O2 and UV irradiation, the ST4 nanoheterostructure can degrade 98.89% of the model pollutant methylene blue (MB) in 15 min, demonstrating remarkable photocatalytic performance. The direct Z-scheme heterojunction exhibited by the SiNW/TiO2 structure facilitates a more efficient charge transfer mechanism with higher reducing and oxidizing ability leading to enhanced photocatalytic behaviour. The degradation pathway examined by LC-MS studies demonstrated the complete breakdown of the organic MB dye molecules ultimately mineralizing into CO2, H2O, and other inorganic substances. The photocatalyst ST4 exhibited excellent reusability and stability after multiple cycles of dye degradation enabling its use in practical water purification purposes.