Ag@SiO2 nanocube loaded miniaturized filter paper as a hybrid flexible plasmonic SERS substrate for trace melamine detection

Abstract

A robust flexible paper-plasmonic hybrid SERS substrate is reported by exploiting the intrinsic properties of filter paper and anisotropic Ag@SiO₂ nanocubes. The fibrous structure of paper promotes the assemblage of sharp-edged nanostructures which significantly improved the SERS activity. An inexpensive sensing platform with reasonable distribution and interparticle spacing of nanocubes was obtained by filtering Ag@SiO₂ through a miniaturized filter paper. The thin silica shell improved the stability and interparticle spacing of silver nanocubes in the sensing platform, rendering enhanced SERS activity through the plasmon-coupling effect as compared to a conventional rigid substrate. Assessment of the analytical performance of the substrate for melamine quantification showed a good linearity (R² = 0.9948) up to 1 mg L⁻¹ with a limit of detection of 0.06 mg L⁻¹. The detection limit in liquid milk was down to 0.17 mg L⁻¹, which is below the permissible residue limit signifying adequate sensitivity for real sample analysis with less sample treatment.