Microplasma-printed Au-based SERS sensing platform for ultra-sensitive chemical analyte detection

Abstract

Direct and efficient fabrication of highly sensitive surface-enhanced Raman scattering (SERS) platforms is essential for Raman detection of chemicals at trace levels but remains challenging. Herein, an atmospheric-pressure microplasma printing system was developed to deposit Au or Au/SiO₂ nanoparticles on silicon wafers through in situ plasma reduction of Au³⁺, thus forming sensing platforms efficiently through digitally controlled electrode movement. The process conditions are optimized to achieve detection limits down to 10⁻¹³–10⁻¹² M for the adenine, crystal violet, and rhodamine 6G analytes. The SERS intensity also maintained a stable linear relationship with adenine concentrations from 10⁻¹² M to 10⁻⁴ M. The Au/SiO₂ platforms show improved SERS properties compared to the AuNP platforms fabricated under the same conditions. In addition to the dielectric properties of SiO₂ nanoparticles, the density and intensity of hot spots are also crucial for sensitive analyte sensing, where higher AuNP density with smaller gap spacing among particles boosts the Raman scattering. Furthermore, arbitrary patterns with complex constructs are constructed by the microplasma printing system, revealing its high flexibility in printing desired patterns. The demonstrated microplasma-printed technique opens a new avenue for the simple, direct, and efficient fabrication of ultra-sensitive SERS platforms.