Wide-Field Digital Surface-Enhanced Raman Scattering: Quantitative Single-Molecule Detection with High Sensitivity and Throughput.

Due to its exceptionally high sensitivity and specificity, surface-enhanced Raman scattering (SERS) is widely employed in diverse fields, including biomedicine, environmental monitoring, and food safety. Nonetheless, the lack of reproducibility and substrate uniformity has seriously hindered its application in quantitative detection, particularly at low analyte concentrations. Recently, the concept of digitization has been integrated into SERS, enabling quantitative and sensitive detection with promising applications (Bi et al. Nature2024, 628, 771-775). In this work, we further developed a wide-field digital SERS (WidiSERS) by employing wide-field microscopy for high throughput. Protein assembled gold nanorod dimers are used for largely enhancing the Raman signals. Reproducible quantification of a wide range of target molecules at extremely low concentrations is achievable through single-molecule measurements. Trace-level quantification of ciprofloxacin in a complex milk environment and phenylalanine in cell culture medium was also achieved, verifying the practicability and accuracy of this method. Meanwhile, the gold nanorod dimer substrate is both simple to prepare and reusable after UV/ozone cleaning. WidiSERS is expected to emerge as a preferred method for ultrafast and effective detection across various fields.