Development of a simple SERS substrate for the detection of pollutants and nanoplastics

This study investigates the development and characterisation of Ag- and Au-coated silicon filter substrates developed for surface-enhanced Raman spectroscopy (SERS) applications. Silver nanoparticles were synthesised by immersing silicon filters in an AgNO₃ solution, with the immersion time playing a crucial role in nanoparticle distribution and SERS efficiency. The highest performance was observed at an immersion time of 30-60 min and allowed the detection of 4-mercaptobenzoic acid (4-MBA) at nanomolar concentrations. To improve stability and tunability, gold was sputtered onto the Ag-coated substrates. Optimal performance was achieved with 6 min of Au sputtering, which allowed picomolar sensitivity for 4-MBA and micromolar detection of melamine. These substrates were further tested for the detection of polystyrene (PS) and polyethylene (PE) nanoplastic particles by Raman mapping with particles down to 50 nm. The successful identification showed great potential for the micro-Raman analysis of nanomaterials. The results emphasise the high sensitivity, versatility and ease of production of the SERS substrates and highlight their potential for applications in environmental and food monitoring, especially for the detection of nanoplastics.