Sustainable LSPR-based platform for trace-detection of analytes in complex matrices

In the last decades, several colorimetric sensor arrays have emerged as low-cost optoelectronic devices for the detection of various compounds. Among these, a class of sensors based on noble metal nanoparticles (NPs) has recently gained great interest. Gold and silver NPs, functionalized with specific receptors, have demonstrated to be powerful tools for trace detection of analytes of interest in various fields, including the food industry, environmental chemistry, and cultural heritage conservation.1 These sensors exploit Localised Surface Plasmon Resonance (LSPR), offering remarkable advantages for analyte detection at exceptionally low concentrations. The mechanism behind these sensors relies on variations in the LSPR through NPs aggregation occurring upon the presence of the analyte, resulting in a shift of the plasmonic absorption and the corresponding colour change. Another application of NPs, still based on LSPR and well-developed for trace-detection, is Surface Enhanced Raman Scattering (SERS) spectroscopy, consisting of the great amplification of the Raman signal of analytes in proximity to the metal NP. SERS is a powerful analytical technique that provides detailed information about the chemical composition of materials. It has applications in the conservation of cultural heritage objects, and has been already employed for the identification of molecule-specific fingerprint signals in a wide range of applications. The need for sustainable, uniform and flexible SERS platforms 2 has led to introducing metal NPs into polymeric brushes, opening new perspectives for composite nanostructured materials featuring unique mechanical, electrical and optoelectrical properties. Additionally, the gel-brush network has demonstrated to stabilise the NPs and induce their uniform spatial distribution.3 We report here on the synthesis and characterization of a new sustainable sensor made of properly functionalized silver nanoparticles (AgNPs) fixed on a polymeric substrate, to be used both as a sampling device and detection system. Different synthetic pathways were experimented, while the substrates were characterised through microscopic and spectroscopic techniques. The SERS performances were tested for probe molecules, which showed a potential for low concentration detection, potentially applicable on analytes of interest for different matrices.