Fabrication of black phosphorous quantum dots and Ag nanoparticles co-sensitized TiO2 nanorod arrays as powerful SERS substrate

Surface enhanced Raman scattering (SERS) substrate based on plasma metal nanoparticles and non-metal quantum dots co-sensitized semiconductor has been used in limit trace detection test. In this research, BPQDs (black phosphorus quantum dots) and Ag nanoparticles co-sensitized TiO2 nanorod arrays were successfully fabricated as powerful SERS substrate. For BPQDs/Ag/TiO2, its detection limit of 4-mercaptobenzoic acid (4-MBA) molecules could achieve even at as low as 1.0 × 10−12 M, and the enhancement factor (EF) is up to 2.5 × 105, exhibiting an excellent SERS sensitivity. Furthermore, a good uniformity is also observed during the detection process, the relative standard deviation of 4-MBA Raman fingerprint peak intensity at 1587 cm−1 is only 7.3 %. Furthermore, BPQDs/Ag/TiO2 substrate is demonstrated to have good repeatability and stability. The synergistic effect of BPQDs, Ag nanoparticles and TiO2 nanorod array is mainly responsible for improved SERS activity, namely, high-density hot spot, optical capture expansion and enhanced charge transfer.