Quantitative SERS measurements by self-assembled ultra-smooth Au nanosphere superlattice with embedded internal reference

Quantitative analysis always encounters difficulty in the field of surface-enhanced Raman spectroscopy (SERS) because of the lack of accurate and reliable analytical means. In this work, a new approach was demonstrated for the quantitative SERS measurement by self-assembled superlattice based on ultra-smooth Au nanospheres (NSs) embedded with 4-methylthiobenzoic acid (4-MBA) as the internal reference. Malachite green (MG) in water and chrysoidine in drinks with detection limit of 0.35 µM were successfully and quantitatively measured by employing Au@4-MBA@Au NSs superlattice as solid SERS substrate. Compared with conventional SERS methods, the fitting linearity of the relative SERS intensity vs. analyte concentrations has significantly improved by this new analysis means. As a result, our approach is a reliable analytical strategy to solve quantitative problems in SERS analysis, which can be easily applied for on-site detection and for preliminary monitoring of food samples.