Ultrasensitive and recyclable superstructure of Au SiO2@Ag wire for surface-enhanced Raman scattering detection of thiocyanate in urine and human serum

Abstract

Thiocyanate level in the human system can serve as a biomarker to distinguish smokers from non-smokers. Thiocyanate is a potential goitrogen, thus an accurate determination may help to identify lactating mothers with high thiocyanate dosage, thereby preventing the transport of excess SCN^- to infants. Surface-enhanced Raman spectroscopy has become a versatile and reliable technique to detect SCN^- in different media. However, the conventional surface-enhanced Raman scattering (SERS) substrates used to detect SCN^- are often discarded after use. The frequent disposal of such metal nanoparticles is detrimental to the environment and makes the SERS-based detection of SCN^- uneconomical. In this study, we present fabrication of a new, ultrasensitive and recyclable SERS substrate, based on an AuSiO₂@Ag wire (W) superstructure, to detect SCN^- in different media. The hierarchical AuSiO₂@AgW substrate was obtained by forming nano-sized patches of SiO₂ on micron-sized AgW and anchoring 30 nm-sized gold nanoparticles on the patches with mercaptopropyltrimethoxysilane. This ultrasensitive substrate could detect SCN^- at a low concentration of 0.001 μM in water, and 0.01 μM in urine and human serum. In addition, a facile procedure to regenerate and recycle the SCN^- bound AuSiO₂@AgW platform in different media has been demonstrated. The insight gained in the present study can serve as a promising and powerful method for fabrication of active and recyclable substrates for SERS-based detection of SCN^-.