Assembly engineering of Ag@ZnO hierarchical nanorod arrays as a pathway for highly reproducible surface-enhanced Raman spectroscopy applications

Abstract

Semiconductor-based surface-enhanced Raman spectroscopy (SERS) substrates with high stability and reproducibility are an important analytical tool in the field of SERS. However, compared with metal substrates, even though semiconductor SERS substrates are cheaper but the progress in SERS enhancement is limited by their insufficient performance. Conventional SERS chips costly and are produced by complicated fabrication methods, while the sample handling processes are not biocompatible and efficient. To address the aforementioned challenges, large-area hexagonal-wrapped ZnO nanorod (ZnO NR) arrays incorporating Ag nanoparticles (Ag NPs) have been employed resulting in efficient SERS-active platforms. This study presents a new design pathway to fabricate highly sensitive and homogeneous SERS substrates that are simple and cost-effective with no aggregations on the surface. This method provides not only ultrasensitive target detection with highly reproducible and uniform SERS signals but also has a self-cleaning capability and reactivating SERS-behaviour under UV light irradiation. We found significantly strong and uniform SERS signal enhancement in the detection of R6G up to ∼4.2 × 107 due to the charge-transfer process between Ag NPs, ZnO NRs, and analyte molecules based on the participation of “hot electrons,” engineering nanogaps of Ag NPs, which may be attributed to the matching of the surface plasmon wavelength resonance with the laser excitation wavelength of 532 nm. Ag NPs assembled onto ZnO NRs may also serve as SERS active platforms for promising applications in chemical and biomedical detection.