A facile synthesis of multifunctional ZnO/Ag sea urchin-like hybrids as highly sensitive substrates for surface-enhanced Raman detection

Abstract

ZnO/Ag sea urchin-like hybrids were prepared through the reaction of zinc salts with KOH to form ZnO particles. This was followed by the deposition of Ag nanoparticles (NPs) onto the surface of the ZnO particles. As the duration of the photochemical deposition reaction was extended from 0.5 h to 2 h then 8 h, the size of the Ag NPs increased from 11 nm to 19 nm and 29 nm, respectively. Due to their high surface-to-volume ratio, rich surface tips, and open morphology the ZnO/Ag sea urchin-like hybrids are expected to be effective as Raman substrates. Herein, it is shown that these materials possess high sensitivity and good reproducibility. After calculation, the enhancement factor values for R6G molecules on ZnO/Ag are 3 × 10⁶ for the peak at 1360 cm⁻¹ and 2.98 × 10⁶ for the peak at 1575 cm⁻¹, respectively. Additionally, the maximum value of the relative standard deviation is found to be below 0.15. It is suggested that local electric fields caused by the electron transfer between ZnO and Ag, the “echo effect” and a high aspect ratio between ZnO branches and Ag NPs all contribute to the SERS enhancement. The distinct morphology of ZnO/Ag sea urchin-like hybrids should also make them ideal substrates for the loading of various large molecules for SERS-based sensing and characterization.