Zinc oxide/silver nanoarrays as reusable SERS substrates with controllable 'hot-spots' for highly reproducible molecular sensing

Hypothesis: The reproducible surface enhanced Raman scattering (SERS)-based sensing of an analyte relies on high quality SERS substrates that offer uniformity over large areas. Uniform ZnO nanoarrays are expected to offer an appropriate platform for SERS sensing. Moreover, since ZnO has good photocatalytic properties, controllable decoration of silver nanoparticles on ZnO nanoarrays may offer an additional opportunity to clean up SERS substrates after each sensing event. Experiments: This study employs a facile soft chemical synthesis strategy to fabricate Raman-active and recyclable ZnO/Ag nanorod arrays as reproducible SERS substrates. Arrays of ZnO nanorods were synthesized using hydrothermal method, which was followed by controllable decoration of ZnO with silver nanoparticles (AgNPs) using an electroless plating technique. Findings: The uniform density of SERS-active 'hot-spots' on ZnO nanoarrays could be controlled on a large 1 x 1 cm(2) substrate. These ZnO/Ag nanoarrays showed high reproducibility (0.132 RSD) towards acquiring SERS spectra of rhodamine B (RB) at 30 random locations on a single substrate. The photocatalytic nature of ZnO/Ag semiconductor/metal hybrid endowed these substrates with reusability characteristics. By controlling metal loading on a semiconductor surface, photocatalytic activity and high SERS performance can be integrated within a single package to obtain high quality, reproducible, stable and recyclable SERS substrates. (C) 2014 Elsevier Inc. All rights reserved.