Synthesis, Characterization, and Humidity Detection Properties of Nb₂O₅ Nanorods and SnO₂/Nb₂O₅ Heterostructures

Nanostructured metal oxide semiconductors are ideally suited for their integration in different devices due to their high thermal and mechanical stability, unique electronic characteristics, and low-cost fabrication. The modification of their surface allows the design of heterostructures with novel properties. In this work, we have synthesized single-crystalline niobium pentoxide (Nb₂O₅) nanorods and niobium-pentoxide-coated tin oxide (Nb₂O₅/SnO₂) heterostructures by chemical vapor deposition. HR-TEM analysis and computer simulation studies showed the low density of defects and high crystallinity of the Nb₂O₅ nanorods, which exhibited high sensitivity toward humidity at low temperatures (60 °C). The fabrication of SnO₂/Nb₂O₅ core–shell heterostructures combines the high sensitivity of Nb₂O₅ shell toward moisture with the good electrical conductivity of SnO₂. The growth of the nanoscopic Nb₂O₅ overlayer on SnO₂ nanowires introduces defects in the structure, which influence the electronic properties of the material and enable the design of more efficient humidity sensors

Additional file 1: Table S1. of Enhanced Photoelectrochemical Behavior of H-TiO2 Nanorods Hydrogenated by Controlled and Local Rapid Thermal Annealing

Donor density (Nd), flat band potential (Vfb) and depletion region width (W) of pristine TiO2 and H-TiO2 nanorods calculated from the Mott-Schottky plots. Figure S1. (a) Optical absorption spectra of pristine TiO2 and H-TiO2 nanorods. (b) Tauc plots of optical absorption curves for pristine TiO2 and H-TiO2 nanorods. Figure S2. Photoconversion efficiency of pristine TiO2 and H-TiO2 nanorods. Figure S3. The O/Ti ratio distribution along the nanorod diameter (a) pristine TiO2 and (b) H-TiO2 nanorods treated at 400 °C. The O/Ti ratio is estimated using EELS spectra taken from a cross-line shown in the TEM image. (DOCX 930 kb

Band Engineered Epitaxial 3D GaN-InGaN Core–Shell Rod Arrays as an Advanced Photoanode for Visible-Light-Driven Water Splitting

3D single-crystalline, well-aligned GaN-InGaN rod arrays are fabricated by selective area growth (SAG) metal–organic vapor phase epitaxy (MOVPE) for visible-light water splitting. Epitaxial InGaN layer grows successfully on 3D GaN rods to minimize defects within the GaN-InGaN heterojunctions. The indium concentration (In ∼ 0.30 ± 0.04) is rather homogeneous in InGaN shells along the radial and longitudinal directions. The growing strategy allows us to tune the band gap of the InGaN layer in order to match the visible absorption with the solar spectrum as well as to align the semiconductor bands close to the water redox potentials to achieve high efficiency. The relation between structure, surface, and photoelectrochemical property of GaN-InGaN is explored by transmission electron microscopy (TEM), electron energy loss spectroscopy (EELS), Auger electron spectroscopy (AES), current–voltage, and open circuit potential (OCP) measurements. The epitaxial GaN-InGaN interface, pseudomorphic InGaN thin films, homogeneous and suitable indium concentration and defined surface orientation are properties demanded for systematic study and efficient photoanodes based on III-nitride heterojunctions