Solution-Based Synthesis of a CdS Nanoparticle/ZnO Nanowire Heterostructure Array

CdS nanoparticle (NP)/ZnO nanowire (NW) heterostructure arrays were fabricated by a two-step chemical solution deposition method. First, vertically aligned ZnO nanowire arrays were grown on a substrate from Zn(NO3)2 (10 mM) and an aqueous ammonia (pH ∼ 11) solution at 95 °C for 6 h. Then, CdS nanoparticles were deposited on the ZnO nanowire array in a chemical bath containing CdSO4, thiourea, and an aqueous ammonia solution (molar ratio of 1:5:500) at 60 °C. The effects of deposition reaction conditions, such as solution concentrations and deposition time, were investigated. Synthesized CdS NP/ZnO NW heterostructures were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM), and their optical absorption property was measured by light absorbance spectrometry. As the solution concentrations and deposition time increased, the sizes and density of CdS nanoparticles on the surfaces of ZnO nanowires increased and the visible-light absorption capability was improved. The CdS NP/ZnO NW heterostructure arrays presented here offer promising applications in solar-energy converting devices. The photoelectrochemical cells using CdS NP/ZnO NW heterostructure arrays as photoelectrodes showed enhanced photocurrent characteristics compared with the photoelectrode cell of a bare ZnO nanowire array.