Practical gas sensing application requires sensors to quantify target analytes with high sensitivity and reproducibility. However, conventional surface enhanced Raman scattering (SERS) sensor lacks reproducibility and quantification arising from variations of "hot spot" distribution and measurement conditions. Here, a ratio-dependent SERS sensor was developed for quantitative label-free gas sensing. Au@Ag-Au nanoparticles (NPs) were filtered onto anodic aluminum oxide (AAO) forming Au@Ag-Au@AAO SERS substrate. 4-MBA was encapsulated in the gap of Au@Ag-Au and served as the internal standard (IS) to calibrate SERS signal fluctuation for improved quantification ability. Combined with headspace sampling method, SO 2 residue in traditional Chinese medicine (TCM) can be extracted and captured on the immediate vicinity of Au@Ag-Au surface. The intensity ratio I 613 cm −1 /I 1078 cm −1 showed excellent linearity within the range of 0.5 mg/kg-500 mg/kg, demonstrating superior quantification performance for SO 2 detection. Signals for concentration as low as 0.05 mg/kg of SO 2 could be effectively collected, much lower than the strictest limit 10 mg/kg in Chinese Pharmacopoeia. Combined with a handheld Raman spectrometer, handy and quantitative TCM quality evaluation in aspect of SO 2 residue was realized. This ratiometric SERS sensor functioned well in rapid on-site SO 2 quantification, exhibiting excellent sensitivity and simple operability.
Yangjie Chen,Juan Hao,Zhihang Yin,Qinghui Wang,Youting Zhou,Lingpu Jia,Huiming Li,Wenlong Liao,Kunping Liu
Internal standard molecule 4-mercaptobenzoic acid (4-MBA) embedded Au core-Ag shell nanorods (Au-MBA@Ag NRs) were prepared by a seed-mediated growth method, then loaded on octahedral MIL-88B-NH2 to obtain a novel ratiometric SERS substrate of Au-MBA@Ag NRs/PSS/MIL-88B-NH2 (AMAPM) for detecting rhodamine 6G (R6G) in chili powder. The porous structure and excellent adsorption ability of MIL-88B-NH2, allowed for increased loading of Au-MBA@Ag NRs, thereby shortening the distance between adsorbed R6G and the “hot spot” resulting from local surface plasmon resonance (LSPR) of Au-MBA@Ag NRs. Based on the SERS characteristic peak ratio of R6G to 4-MBA, the ratiometric SERS substrate displayed improved accuracy and excellent performance for R6G detection, with a wide linear range of 5–320 nM and a low detection limit of 2.29 nM as well as fine stability, reproducibility and specificity. The proposed ratiometric SERS substrate offered a simple, fast and sensitive sensing strategy for R6G detection in chili powder, which demonstrated potential applications in food safety and the analysis of trace analytes in complex matrices.
Zhihui Wu,Da-Wen Sun,Hongbin Pu,Qingyi Wei,Xuanran Lin
Mycotoxin B1 (AFB1) contamination in agricultural products pose a deadly danger to animal and human health and its rapid and reliable detection is thus very important. Herein, a ratiometric surface-enhanced Raman scattering (SERS) aptasensor for AFB1 detection was developed, in which 1,2-bis(4-pyridyl) ethylene (BPE) was used to trigger the assembly of Au nanoparticle dimers (AuNP dimers) and form intensive SERS “hot spots”, and MXenes nanosheets could load aptamer-modified AuNP dimers due to the hydrogen bonding and the chelation between the phosphate groups of aptamers and the Ti ion of MXenes. With the presence of AFB1 preferentially binding to AFB1 aptamer, AuNP dimers were separated from MXenes nanosheets, leading to a decrease in SERS intensity. Regression analysis in the range from 0.001 to 100 ng·mL −1 showed the limit of detection (LOD) being 0.6 pg·mL −1 in standard solution, indicating that the great prospects of the AuNP dimers/MXenes SERS substrate for detecting AFB1.
危险品化学品经营许可证（带存储）