Concurrent enhancement in the H2 and UV sensing properties of ZnO nanostructures through discontinuous lattice coating of La3+via partial p–n junction formation

Abstract

The development of multifunctional sensors with surface-modified one-dimensional ZnO nanostructures has attracted significant scientific interest due to their versatility. Herein, we present a simple hydrothermal route to coat lanthanum (La³⁺) ions onto the surface lattice of ZnO nanorods (La-coated ZNRs). The as-prepared ZnO nanorods (ZNRs) without La³⁺ ion coating were also synthesized under the same conditions for comparison. Each sample was then fabricated as a multisensor with interdigitated electrodes, and their H₂ gas and UV sensing properties were systematically studied. Thus, the La-coated ZNR-based multisensor exhibited remarkable H₂ sensing and efficient UV detection properties when compared to that of the as-prepared ZNRs. An ultra-high H₂ response of 63.8% was achieved even at a low detection level (ppm) with an ultra-fast response (15 s) and recovery time (9 s). Also, excellent UV sensing properties were observed with a high switch ratio (I_photo/I_dark) of 256.3. Moreover, the present multisensor was also revealed to exhibit superb sensitivity, stability, repeatability and selectivity towards H₂ gas and UV light. This outstanding enhancement in the multisensing measurements of La-coated ZNR-based multisensors can be ascribed to their high oxygen vacancies, and the formation of partial p–n junctions on their discontinuous surface lattices. Furthermore, this sensor was also utilized for the simultaneous detection of UV light and H₂ gas in a single measurement. The prominent feature of the incorporation of La³⁺ ions into ZNRs is the improvement in efficient multisensors, but, in addition, this combination can be highly useful for H₂ storage materials.