Improved Charge Transfer Contribution by Cosputtering Ag and ZnO.

Bingbing Han,Xiangxin Xue,Eungyeong Park,Sila Jin,Shuang Guo,Young Mee Jung,Lei Chen

doi:10.3390/nano10081455

Abstract

A two-dimensional polystyrene microsphere array cosputtered with Ag and ZnO was designed for evaluating surface-enhanced Raman scattering (SERS) activity. The surface plasmon resonance (SPR) and SERS properties were significantly changed by the introduction of ZnO into the Ag film. By increasing the Ag sputtering power, a redshift of the SPR peak was obtained. Moreover, improved SERS activity occurred because of the electromagnetic (EM) contribution from the increasing Ag content and the charge transfer (CT) contribution from the introduction of ZnO. More importantly, the Hall effect was employed to evaluate the carrier density effect on the SERS contribution of the Ag/ZnO film. The increase in the carrier density as the Ag sputtering power increased indicated an increasing number of free electrons stored in the Ag/ZnO film, which was accompanied by improved EM and CT contributions.

Highlights

With the development of nanoscience and laser technology, numerous development opportunities exist for surface-enhanced Raman scattering (SERS) in interface and surface investigations and life science applications [1,2,3,4]
mercaptobenzoic acid (MBA), which was selected as a probe molecule, was dissolved in absolute ethanol at a concentration of 10−3 M, and the Ag/ZnO-coated PS arrays were immersed in the MBA solution for 1 h to obtain SERS spectra
The observed SERS enhancement of MBA on the Ag/ZnO films was due to the increase in free electrons, which was caused by the increase in Ag content

Summary

Introduction

With the development of nanoscience and laser technology, numerous development opportunities exist for surface-enhanced Raman scattering (SERS) in interface and surface investigations and life science applications [1,2,3,4]. Au, Ag, Cu, and a few transition metals are widely used as SERS-active substrates that provide higher SPR with laser excitation [9,10]. Finding a suitable method to conduct in-depth research on the characteristics and essence of the two SERS enhancement mechanisms is necessary. Multimaterial composites, such as metal/semiconductor composites or inorganic hybrid nanostructures, were developed as SERS-active substrates that exhibited excellent SERS properties. The preparation of metal-semiconductor SERS-active substrates with high sensitivity and controllability has attracted great attention. The design and manufacture of Ag-ZnO composite materials as SERS-reinforced substrates with simple and controlled metal SPR is very important. The CT process on Ag/ZnO-4-mercaptobenzoic acid (MBA) was studied to evaluate the contributions of the as-prepared material to SERS enhancement

Chemicals

Results and Discussion

Conclusions