TiO compact layer induced charge transfer enhancement in a three-dimensional TiO-Ag array SERS substrate for quantitative and multiplex analysis.

A highly sensitive and uniform surface-enhanced Raman scattering (SERS) substrate is the guarantee for reliable quantitative analysis. Herein, a three-dimensional TiO-Ag SERS substrate was prepared by growing a TiO nanorods (NRs) array on a TiO compact layer (c-TiO), followed by modification with Ag nanoparticles (AgNPs). The synergy between the c-TiO, semiconductor TiO NRs and the plasmonic AgNPs collaboratively endowed it with high sensitivity, in which c-TiO effectively blocked the recombination of electrons and holes, and the charge transfer enhancement contributed 10-fold improvement over that without the c-TiO substrate. Besides the high sensitivity, the TiO-Ag hybrid array SERS substrate also showed quantitative and multi-component detecting capability. The limit of detection (LOD) for crystal violet (CV) was determined to be 10 M even with a portable Raman instrument. The TiO-Ag composite structure was extended to detect organic pesticides (thiram, triazophos and fonofos), and the LODs for thiram, triazophos and fonofos were measured to be 10 M, 10 M and 10 M, respectively. In addition, the realistic simulation detecting pesticide residues for a real sample of dendrobium was demonstrated. The sensitive, quantitative and multiplex analysis of the TiO-Ag hybrid array substrate indicated its great potential in the rapid detection of pesticide residues in real samples.