Spatial separation of photogenerated electron-hole pairs in solution-grown ZnO tandem n-p core-shell nanowire arrays toward highly sensitive photoelectrochemical detection of hydrogen peroxide

A facile solution process based on polyethylene glycol (PEG)-assisted secondary growth has been demonstrated for the epitaxial growth of a Sb-doped ZnO thin layer on ZnO nanowire arrays. The resultant ZnO@Sb-doped ZnO core-shell nanowires present a perfect single-crystal feature whereas structural deformation commonly existing in Sb-doped ZnO is greatly suppressed due to the confined thickness and the effect of PEG. Mott-Schottky analysis indicates that the formation of tandem n-p homojunctions at the coaxial interface is derived from the n-type conduction of the primary ZnO and the p-type conduction of the Sb-doped ZnO. By implementation of the core-shell nanowire arrays as electrodes for photoelectrochemical detection of the hole scavenger hydrogen peroxide (H2O2), a significantly enhanced photocurrent response toward different concentrations of H2O2 is obtained. The high sensitivity is ascribed to the efficient spatial separation of photogenerated electron-hole pairs facilitated by the built-in electric field in the n-p homojunction region, the lattice matching homojunction interface and the confined shell thickness for hole transport.