Effect of ammonia on morphology, wettability and photoresponse of ZnO nanorods grown by hydrothermal method

Abstract ZnO nanorods were prepared on glass at the temperature of 95° using a hydrothermal method. Microstructure, surface morphology, optical properties, wettability and UV photoreponse of the ZnO nanorods were measured by X-ray diffractometry, scanning electron microscopy, UV–vis spectrophotometer, laser micro-Raman spectrometer, home-made water contact angle apparatus and interactive source meter instrument. The results indicate that the ZnO nanorods appear hexagonal wurtzite structure with a preferred orientation along c -axis. The surface morphology changes from flat hexagonal crystallographic plane to tapered tip, which may be attributed to a dynamic equilibrium between ZnO formation and dissolution. Shift of the absorption edge could be attributed to synergy of the surface morphology and Burstein-Moss effect. The intensity ratio of the visible emission to the UV emission decreases with increasing ammonia additive. Enhanced hydrophobicity and the light-induced reversible wettability of the samples could be attributed to the decrease of surface area fraction of solid and interspaces between ZnO nanorods. The sample with ammonia additive of 2.4 mL has the faster photoresponse, which could be attributed to decrease of the structural point defects.