Engineering the PS@MXene@Ag composite for ultrasensitive SERS-based detection of organic pollutant

By integrating the photonic nanojet effect of polystyrene microsphere (PS), the charge transfer capability of MXene nanosheets, and the electromagnetic field enhancement induced by Ag nanoparticles, the PS@MXene@Ag composite substrate exhibited outstanding SERS sensitivity. • The SERS performance of the PS@MXene@Ag substrate was evaluated using 2-mercaptopyridine as a probe molecule, achieving a detection limit as low as 1.24 × 10 −12  M, with the SERS performance factor (SPF) up to 5.0 × 10(Gueguen et al., 2000 [7] ) . In addition, the SERS substrate demonstrated satisfactory results in signal uniformity, batch-to-batch reproducibility, and long-term stability. • PS@MXene@Ag composite successfully detected thiram and methyl blue on practical sample surfaces (orange and fish), achieving satisfactory recovery rates. Surface-enhanced Raman scattering (SERS) spectroscopy has emerged as a powerful analytical technique for the sensitive detection of hazardous molecules, owing to its ultranarrow spectral linewidths and highly specific molecular fingerprinting capability. Herein, we designed a reliable SERS substrate consisting of polystyrene microspheres (PS), Ti 3 C 2 T x MXene nanosheets, and Ag nanoparticles (NPs) for the sensitive detection of various organic pollutants. By integrating the photonic nanojet effect of PS, the charge transfer capability of MXene nanosheets, and the electromagnetic field enhancement induced by Ag NPs, the PS@MXene@Ag composite substrate exhibited outstanding SERS sensitivity, along with excellent reproducibility and signal uniformity. As a result, the limit of detection (LOD) for 2-mercaptopyridine (2-Mpy) was as low as 1.24 × 10 −12  M, with the SERS performance factor (SPF) of up to 5.0 × 10 7 . Moreover, the SERS substrate maintained good stability after storage for four weeks. In addition, the PS@MXene@Ag composite was successfully applied to the detection of other organic pollutants, including thiram and methylene blue (MB). The calibration results revealed a good linear relationship between the logarithm of concentration and the corresponding SERS intensity, with correlation coefficients (R 2 ) of 0.99 and 0.98, respectively. The LODs for thiram and MB were calculated to be 1.96 × 10 −10  M and 2.33 × 10 −10  M, respectively, and satisfactory recovery rates were obtained in practical sample analyses (orange peel and fish skin). These results demonstrate that the fabricated PS@MXene@Ag SERS substrate has promising potential for the detection of organic molecular pollutants. Download: Download high-res image (129KB) Download: Download full-size image PS@MXene@Ag as a SERS-active substrate for the detection of organic pollutants.