The photoluminescence properties of $\mathrm{ZnO}$ nanoneedle arrays, grown on silicon substrate by electrodeposition, are studied over the temperatures from $10\mathrm{K}$ to $300\mathrm{K}$ . There exist three emission bands in ultraviolet, violet, and green regions, respectively. With increasing temperature, these bands show different temperature dependences: A normal redshift for the ultraviolet emission, $S$ -shaped shift for the violet emission, and blueshift for the green one. The origins of these three bands and their temperature-dependent shifts are explained based on defect levels (zinc interstitial and oxygen vacancy levels) and carrier localization effect at the defect levels in addition to band-gap shrinkage.

A facile route was presented for mass fabrication of porous ZnO nanoplates, with a yield of >94%, based on a solvothermal method, using ethylene glycol as the morphology director, and subsequent annealing process. The as-prepared ZnO nanoplates are composed of two terminal non-polar planes with several microns in the planar dimensions and 10–15 nm in thickness. The nanoplates are porous with a pore diameter of 5–20 nm and a high specific surface area (147 m² g⁻¹). Importantly, such ZnO nanoplates show strong and selective adsorption to cationic contaminants. Especially, they can very efficiently adsorb heavy metal cations in aqueous solution, and have an unsaturated adsorption capacity of more than 1600 mg g⁻¹ for Cu(II) ions, exhibiting a strong, structurally enhanced adsorption performance. The adsorption isotherm is subject to the Freundlich equation, in contrast to that of the commercial ZnO nanopowders, which follows a Langmuir isotherm model. This work not only demonstrates the possibility and validity of the porous ZnO nanoplates as promising adsorbents for contaminant-removal and environmental remediation, but also gives insight into understanding the adsorptive behavior of porous ZnO plates.