Silica Nanoparticles Modified with Fluorescent Dyes as Probes for <i>in Situ</i> Characterization of Natural Rubber Coatings

In this study, we used fluorescent silica particles (SiPs) as probes to characterize the chemical stability of natural rubber (NR)-based coatings in situ without extensive sample preparation. By tuning the size, concentration, and surface charge of the SiPs and the type of solvent, we obtained two distinct NR-SiPs coatings: (1) irregular honeycomb patterns and (2) flat surfaces. Raman spectral mapping was used to investigate the chemical structure and to illustrate the spatial heterogeneity of the multiple components of the NR-SiPs coatings. The stability of the NR-SiPs coatings was assessed under fluid shear force stress and at high ionic strength conditions (NaCl, 0.85% w/v) using a perfusion chamber coupled with a confocal laser scanning microscope. By evaluating the fluorescent signal of the SiPs, we determined their distribution in the NR-based coatings and monitored their chemical stability via in situ confocal imaging. Using the fluorescent SiPs as probes, we could infer the high chemical stability of the coatings at high ionic strength and under shear stress conditions, opening new horizons for the application of NR coatings in medicine, microelectronics, and the automobile industry