Stencil-patterned AuNPs@PMMA spherical-cavity substrates for ultrasensitive SERS detection

Surface-enhanced Raman scattering (SERS) was extensively employed in the domains of target analysis and detection owing to its benefits of high sensitivity and nondestructive detection. In this study, polystyrene (PS) microspheres served as templates. PS microspheres were systematically assembled on silicon wafer surfaces using air-liquid interfacial self-assembly. Subsequently, a PMMA-anisole solution was spin-coated to fill the interstices of the microspheres. Following the removal of the templates using cyclohexane ultrasonication method, gold nanoparticles were deposited onto the substrates utilizing the three-phase self-assembly procedure to construct the AuNPs@PMMA sphere-cavity array substrate. When the PMMA-anisole solution concentration was 1%, the spinning speed was 5500   r/min, and the annealing temperature was 120 °C, the most regular nanostructure of the spherical cavity substrate was achieved. The Raman activity of the fabricated substrates was investigated with the selection of Rhodamine (R6G), Crystal Violet (CV) and Aspartame (APM) as target molecules. The experimental results indicated that AuNPs@PMMA sphere-cavity array substrate exhibiting high sensitivity, excellent uniformity, and stability, and the detection limits for R6G and CV were 10 -11   M and 10 -10   M, respectively. In addition, the substrate achieved a low detection limit of 0.0313   g/L for aspartame (APM), demonstrating the potential application of the substrate in food safety testing.