Highly sensitively detecting tetramethylthiuram disulfide based on synergistic contribution of metal and semiconductor in stable Ag/TiO2 core-shell SERS substrates

In this study, we successfully constructed Ag/TiO2 core-shell nanoparticles through an easy wet chemistry method for SERS study. Compared to Ag cores, the Ag/TiO2 core-shell nanoparticles presented higher SERS sensitivity, owing to a synergistic SERS enhancement arising from electromagnetic field effect of Ag cores and chemical enhancement of TiO2 shells. Furthermore, uniform TiO2 shells were able to effectively protect the internal Ag cores against destruction in external environment and thus storage stability of Ag/TiO2 nanoparticles was prominently improved. The as prepared Ag/TiO2 core-shell nanoparticles were applied to quantitatively sense tetramethylthiuram disulfide (TMTD) in solution using a portable Raman spectrometer. The results showed that the SERS intensity of 563 cm−1 assigned to S-S stretching mode had a good linear relationship with the concentration of TMTD with the correlation coefficient (R2) of as high as 0.99 and the detection limit of as low as 1.15 × 10−10 M. Consequently, the prepared Ag/TiO2 nanoparticles present specially advantage of quantifying S-S groups by SERS, because the TiO2 shell could act as a spacer between Ag cores and TMTD molecules and keep the S-S bonds intact.