Optofluidic SERS based on Ag nanocubes with high sensitivity for detecting prevalent water pollutant

• Na Ran, Xing Wang, Yuan Gan, and Jie Zhang
• received 03/25/2024; accepted 04/13/2024; posted 04/16/2024; Doc. ID 524709
• Abstract: To enhance the integration and practical applicability of the Raman detection system, silver nanocubes (Ag NCs) were synthesized using a polyol method. A liquid-liquid interface approach was employed to transfer a monolayer of Ag NCs "film" onto a silicon wafer substrate, resulting in the fabrication of a highly sensitive and uniform surface enhanced Raman scattering (SERS) substrate denoted as "Ag@SiO2". The electromagnetic field distribution of various dimers on the Ag@SiO2 was analyzed using finite difference time domain (FDTD) software. The results reveal that the electromagnetic enhancement effect is most pronounced in cube-cube dimers, indicating that Ag NCs exhibit superior localized surface plasmon resonance (LSPR) response due to their well-defined geometric regularity and sharp geometric angles. For Rhodamine 6G (R6G) probe molecules, the Ag@SiO2 shows ultra-high sensitivity, with the limit of detection (LOD) of 10^−12 mol/L, and the enhancement factor (EF) can reach 1.4×10^10. The relative standard deviation (RSD) at the main characteristic peaks is below 10%, demonstrating good consistency in substrate performance. In addition, the Ag@SiO2 modified with hexanethiol exhibits high sensitivity, uniformity, and repeatability in detecting for pyrene, with the LOD of 10^−8 mol/L and a minimum RSD of 6.09% at the main characteristic peak, effective recognition capabilities for pyrene and anthracene in mixed solutions. Finally, chemisorption and physisorption strategies were prepared in microfluidic channels and experimentally compares, and a real-time detection of pyrene solutions can also be achieved. This method can achieve rapid detection and precise differentiation of polycyclic aromatic hydrocarbons in water pollutant.