TiO(2) compact layer induced charge transfer enhancement in a three-dimensional TiO(2)–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(2)–Ag SERS substrate was prepared by growing a TiO(2) nanorods (NRs) array on a TiO(2) compact layer (c-TiO(2)), followed by modification with Ag nanoparticles (AgNPs). The synergy between the c-TiO(2), semiconductor TiO(2) NRs and the plasmonic AgNPs collaboratively endowed it with high sensitivity, in which c-TiO(2) effectively blocked the recombination of electrons and holes, and the charge transfer enhancement contributed 10-fold improvement over that without the c-TiO(2) substrate. Besides the high sensitivity, the TiO(2)–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(−9) M even with a portable Raman instrument. The TiO(2)–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(−7) M, 10(−7) M and 10(−6) 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(2)–Ag hybrid array substrate indicated its great potential in the rapid detection of pesticide residues in real samples.