Assessment of silver-based calcium silicate hydrate as a novel SERS sensor

This study aims at synthesizing a novel Surface-Enhanced Raman Spectroscopy (SERS) sensor based on a nanostructured substrate, calcium silicate hydrate (C-S-H), the main hydration product of Portland cement. The procedure involves first the incorporation of silver within the nanostructure of the gel (C-S-Ag-H) and second the modification of the surface of pellets of the newly synthesized material by laser irradiation at 532 nm or 355 nm. The assessment of the SERS activity revealed no amplification of the organic molecule rhodamine B (RdB) signal, used as a probe, on the C-S-Ag-H before laser irradiation. However, after laser irradiation, the SERS effect was comparable to that of reference colloidal Ag nanoparticles (NPs). This SERS response is attributed to an increase in the concentration of metallic silver on the surface of the C-S-Ag-H pellets upon laser irradiation and material ablation as revealed by X-ray Photoelectron Spectroscopy (XPS). Further enhancement of the SERS signals was induced by depositing colloidal Ag NPs on the irradiated pellets, giving rise to interparticle hot spots where the electromagnetic field is further intensified.