Improved Surface-Enhanced Raman Scattering Properties of ZrO2 Nanoparticles by Zn Doping

In this study, ZrO2 and Zn–ZrO2 nanoparticles (NPs) with a series of Zn ion doping amounts were synthesized by the sol-gel process and utilized as substrates for surface-enhanced Raman scattering (SERS). After absorbing the probing molecule 4–mercaptobenzoic acid, the SERS signal intensities of Zn–ZrO2 NPs were all greater than that of the pure ZrO2. The 1% Zn doping concentration ZrO2 NPs exhibited the highest SERS enhancement, with an enhancement factor (EF) value of up to 104. X-ray diffraction, X-ray photoelectron spectroscopy, Ultraviolet (UV) photoelectron spectrometer, UV–vis spectroscopy, Transmission Electron Microscope (TEM), and Raman spectroscopy were used to characterize the properties of Zn–ZrO2 NPs and explore the mechanisms behind the SERS phenomenon. The charge transfer (CT) process is considered to be responsible for the SERS performance of 4–MBA adsorbed on Zn–ZrO2. The results of this study demonstrate that an appropriate doping ratio of Zn ions can promote the charge transfer process between ZrO2 NPs and probe molecules and significantly improve the SERS properties of ZrO2 substrates.