Plasmonic chitosan cross-linked dialdehyde chitosan aerogels as 3D surface-enhanced Raman scattering substrates for sensitive and reliable detection

Surface Enhanced Raman Scattering (SERS) has the advantages of non-destructive detection and high sensitivity, however, low hotspots utilisation and inhomogeneous distribution limit its application. In response to the problem of underutilization of hotspots in most SERS substrates, a crosslinking of chitosan with dialdehyde chitosan aerogels loaded with Ag NPs (CDSA) as SERS substrates with chitosan (CS) as the main body and dialdehyde chitosan (DACS) as the reducing and cross-linking agent were prepared. Unlike other 3D structures such as hydrogels, CDSA can capture probe molecules in a much shorter period of time and enhance SERS signals by collapse. The SERS performance of CDSA was evaluated by rhodamine 6 G (R6G) and methylene blue (MB), indicating that the CDSA substrate has good stability (90 days), repeatability (RSD=4.15 %) and reproducibility (RSD=4.86 %). The enhancement factors (EFs) was 1.3×10⁸ for R6G and 9.2×10⁷ for MB. Both gas sample and liquid sample were detected to evaluate the performances of CDSA in practical application. 4-Aminothiophenol (4-ATP) was utilized to test the efficacy of CDSA on gas-phase to-be-tested substances and the limit of detection (LOD) was 0.59 mg/L. The tests performed on sildenafil (SD) in real samples showed recoveries ranging from 97.5 % to 103.4 % with a LOD of 0.055 mg/L. It was indicated that the CDSA substrate could serves as a satisfactory SERS sensor for sensitive and rapid detection for both gas phase and liquid samples.