Vertically aligned ZnO nanorods (NRs) on aluminum-doped zinc oxide (AZO) substrates were fabricated by a single-step aqueous solution method at low temperature. In order to optimize optical quality, the effects of annealing on optical and structural properties were investigated by scanning electron microscopy, X-ray diffraction, photoluminescence (PL), and Raman spectroscopy. We found that the annealing temperature strongly affects both the near-band-edge (NBE) and visible (defect-related) emissions. The best characteristics have been obtained by employing annealing at 400°C in air for 2 h, bringing about a sharp and intense NBE emission. The defect-related recombinations were also suppressed effectively. However, the enhancement decreases with higher annealing temperature and prolonged annealing. PL study indicates that the NBE emission is dominated by radiative recombination associated with hydrogen donors. Thus, the enhancement of NBE is due to the activation of radiative recombinations associated with hydrogen donors. On the other hand, the reduction of visible emission is mainly attributed to the annihilation of OH groups. Our results provide insight to comprehend annealing effects and an effective way to improve optical properties of low-temperature-grown ZnO NRs for future facile device applications.

Photoluminescent zero-dimensional (0D) quantum dots (QDs) derived from transition metal dichalcogenides, particularly molybdenum disulfide, are presently i

We report the facile and economic preparation of two-dimensional (2D) and 0D MoSe₂ nanostructures based on systematic and non-toxic top-down strategies. We demonstrate the intrinsic peroxidase-like activity of these MoSe₂ nanostructures. The catalytic processes begin with facilitated decomposition of H₂O₂ by using MoSe₂ nanostructures as peroxidase mimetics. In turn, a large amount of generated radicals oxidizes 3,3,5,5-tetramethylbenzidine (TMB) to produce a visible color reaction. The enzymatic kinetics of our MoSe₂ nanostructures complies with typical Michaelis–Menten theory. Catalytic kinetics study reveals a ping–pong mechanism. Moreover, the primary radical responsible for the oxidation of TMB was identified to be Ȯ₂⁻ by active species-trapping experiments. Based on the peroxidase mimicking property, we developed a new colorimetric method for H₂O₂ detection by using 2D and 0D MoSe₂ nanostructures. It is shown that the colorimetric sensing capability of our MoSe₂ catalysts is comparable to other 2D materials-based colorimetric platforms. For instance, the linear range of H₂O₂ detection is between 10 and 250 μM by using 2D functionalized MoSe₂ nanosheets as an artificial enzyme. Our work develops a systematic approach to use 2D materials to construct novel enzyme-free mimetic for a visual assay of H₂O₂, which has promising prospects in medical diagnosis and food security monitoring.