A new strategy for improving quantitative detection of SERS: Using CH3NH3PbBr3 as a substrate to narrow the FWHM of adsorbed molecular spectrum

Spectra in surface-enhanced Raman scattering (SERS) are always accompanied by a continuous emission known as “background”, which complicates the analysis with a poor signal-to-noise ratio (SNR), especially for qualitative and quantitative detection. Here, the SERS profile of the CH 3 NH 3 PbBr 3 substrate displays high similarity with the bulk Raman spectra, and its FWHM   is exceeding narrow. The significantly increased SNR of the probe molecules indicates that the substrate helps to improve the quantitative analysis capability of the SERS technology and alleviate the background-related problems. For the CH 3 NH 3 PbBr 3 substrate, good linearity (R 2  = 0.9591) in the range of 1.0 × 10 -7  − 1.0 × 10 -3   mol/L was obtained and the limit of detection (LOD) is 7.88 × 10 -6   mol/L. The reason for this excellent performance is that the introduction of organic molecules splits the 3D CH 3 NH 3 PbBr 3 substrate to form a 2D perovskite that fixes the molecular orientation through chemical interactions. The CH 3 NH 3 PbBr 3 has the advantage of maintaining the conformation and orientation consistency of adsorbed molecules. Meanwhile, compared with the commonly used noble metal (Au, Ag) and semiconductor (ZnO, TiO 2 ) SERS substrates, the CH 3 NH 3 PbBr 3 substrate has obvious superiorities in both spectral peak intensity and peak shape. Furthermore, the CH 3 NH 3 PbBr 3 substrate possesses specific recognition ability that has the same enhancement effect for a series of pyridine-containing probe molecules. Finally, the enhancement mechanism is discussed according to the CT contribution. As a promising substrate for SERS technology, CH 3 NH 3 PbBr 3 will provide more possibilities for quantitative and multiplex detection in the future.