Type-II ZnO nanorod-SnO2 nanoparticle heterostructures: characterization of structural, optical and photocatalytic properties.

In this work we report, for the first time, on the preparation of ZnO nanorod-SnO2 nanoparticle (ZnO NR-SnO2 NP) heterostructures by a simple two-step thermal evaporation approach. Systematical characterization of the product reveals that the rutile SnO2 NPs, with a diameter of about 20 nm, are uniformly and tightly decorated on the entire ZnO NRs. Photoluminescence (PL) investigation on the ZnO NR-SnO2 NP heterostructures shows that they exhibit a significantly decreased UV emission compared with the bare ZnO NRs, revealing an efficient charge separation arising from the type-II band alignment. Enlightened by this merit, photocatalytic behavior of the synthesized heterostructures is studied, which shows a remarkably enhanced photodegradation performance of rhodamine B (RhB) in contrast to the pure ZnO NRs. We also carry out the stability test of the ZnO NR-SnO2 NP heterostructures and the result indicates an extremely high adhesion nature between the ZnO NR and the coated SnO2 NPs. This advantage endowed with the thermal evaporation approach can lead to an efficient spatial charge separation between the ZnO NR and the SnO2 NPs and thus effectively minimize the charge recombination along three-dimensional heterointerfaces, which makes such ZnO NR-SnO2 NP architectures highly promising for a wide range of photovoltaic and photocatalytic applications.