Low-temperature photoluminescence behaviour of Ag decorated ZnO Nanorods

The Ag nanoparticles decorated ZnO nanorods (Ag:ZnO) were prepared by irradiating the precursor solution with ultra-violet radiation for two irradiation times (6 and 17 h). Structural and microstructural studies were done by X-ray diffraction and transmission electron microscopy, respectively. Optical properties were studied by UV-Vis spectroscopy at room temperature (300 K) and photoluminescence (PL) spectroscopy at low-temperature in the temperature range from 5 to 300 K. The Ag:ZnO nanorods possessed the wurtzite structure of ZnO along with the cubic fcc phase of Ag nanoparticles. Average size of Ag nanoparticles in Ag:ZnO nanorods prepared with 6 and 17 h of UV irradiation time was 4 and 16 nm, respectively. The 4 nm Ag nanoparticles had played a crucial role for enhanced PL emission (in the UV region) in the Ag:ZnO nanorods at 60 K. In the case of 16 nm sized Ag nanoparticles, violet emission has been enhanced about 3.5 times compared to that of pure ZnO nanorods and 4 nm-Ag:ZnO nanorods at 5 K. Thermal activation energy of 4 nm-Ag:ZnO and 16 nm-Ag:ZnO nanorods was found to be 0.6 and 0.7 meV, respectively, at low temperature region (5 to 60 K).