PHEMA polymer brush/Ag nanoparticle hybrids for SERS analytics: characterization and performance as versatile sensing...

Surface plasmon resonance technology has shown broad applicability in different fields of molecular sensing. In particular, sensor arrays based on noble metal nanoparticles (NPs) have been demonstrated to be powerful tools for trace detection in food industry, environmental chemistry and Cultural Heritage conservation. The increasing demand for sustainable, uniform and flexible plasmonic platforms has led to introduce metal NPs into polymeric brushes, opening new perspectives for composite nanostructured materials and offering enhanced stabilization of NPs along with a defined spatial distribution.

In this study, we report on the synthesis and characterization of a hybrid sensor system, comprising functionalized AgNPs anchored within a 2-hydroxyethyl methacrylate (PHEMA) polymeric brush, obtained through atom transfer radical polymerization. This polymer-based platform offers versatile applications - from sampling to detection - by leveraging the unique optoelectronic properties of a gel-brush network to achieve robust Surface Enhanced Raman Spectroscopy (SERS) performances. Different synthetic pathways were explored - occasionally using Triethylen Glycol Dimethacrylate as a crosslinker and varying the AgNO₃ reduction protocol. Six different substrates, with thickness ranging from 0.1 to 1 μm and NPs size between 20 and 200 nm were obtained and completely characterized through microscopic and spectroscopic analyses. SERS performances were tested for probe molecules (Rhodamine 6G, Malachite Green, Alizarin and Ochratoxin A), demonstrating the sensor potentiality for a low-concentration analyte detection across diverse matrices (down to 10^-9 M), underscoring its applicability in a wide range of fields.

The PHEMA brush architecture offers enhanced control over SERS and acts as a stabilizer towards NPs, distinguishing it from traditional colloidal systems. The introduction of a new synthetic route for NPs reduction inside the polymer matrix - obtained by combining established methodologies for colloidal Ag preparation, - ensures an hybrid structure which is inherently compatible with other analytical techniques. These features significantly broadens the polymer-based system application scope and positions it as a flexible, multifunctional sensing interface.