Here, we report an efficient and facile method for constructing plasmonic gold nanostructures with controlled morphology on a Si wafer and its use as a surface enhanced Raman scattering (SERS) reporting system for specific detection of HClO. To achieve this substrate, the core gold nanoparticles (AuNPs, ∼100 nm) with a monolayer of 4-mercaptoimidazole (MI) ligands were covalently linked to a thiol-derived Si wafer (MI-AuNPs@SH-Si). Taking advantage of the intermolecular NH···N hydrogen bond (HB) provided by the neighboring imidazole moiety, multiple satellite AuNPs (∼12 nm) decorated with both MI and a Raman reporter are assembled around the core MI-AuNPs at pH 5.0. The uniform morphology of the AuNP-based nanostructures on the Si wafer offer a high density of hot spots with good SERS performance for detecting HClO. The fast oxidation of the imidazole moieties by HClO causes HB destruction and therefore separation of the satellite AuNPs from the core AuNPs, which gives rise to SERS signal damping of the chip that is employed for HClO analysis. This simple and cost-effective method is highly selective for HClO over common interferences and several reactive oxygen/nitrogen species, and enabled rapid analysis at concentrations as low as 1.2 μmol L(-1). The present approach is applied to analyze water and human serum samples with satisfactory results.
Keywords: gold nanoparticles; hydrogen bonding; hypochlorous acid; imidazole; surface-enhanced Raman scattering.