TiO2 compact layer induced charge transfer enhancement in a three-dimensional TiO2-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 TiO2-Ag SERS substrate was prepared by growing a TiO2 nanorods (NRs) array on a TiO2 compact layer (c-TiO2), followed by modification with Ag nanoparticles (AgNPs). The synergy between the c-TiO2, semiconductor TiO2 NRs and the plasmonic AgNPs collaboratively endowed it with high sensitivity, in which c-TiO2 effectively blocked the recombination of electrons and holes, and the charge transfer enhancement contributed 10-fold improvement over that without the c-TiO2 substrate. Besides the high sensitivity, the TiO2-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 TiO2-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 TiO2-Ag hybrid array substrate indicated its great potential in the rapid detection of pesticide residues in real samples.

Automated summary

A highly sensitive and uniform surface-enhanced Raman scattering (SERS) substrate was developed by growing a TiO2 nanorods (NRs) array on a TiO2 compact layer, followed by modification with Ag nanoparticles. The synergistic effect of the c-TiO2, semiconductor TiO2 NRs, and plasmonic AgNPs contributed to its high sensitivity, with a 10-fold improvement compared to substrates without c-TiO2. The TiO2-Ag hybrid array substrate demonstrated quantitative and multi-component detecting capability, with detection limits of 10(-9) M for crystal violet and 10(-7) M for thiram, triazophos, and fonofos. Realistic simulation detecting pesticide residues in a sample of dendrobium was also demonstrated.