Surface Modification of Lanthanum Fluoride Nanoparticles with 4-(2-Pyridylazo)resorcinol

This study explores the interaction between 4-(2-pyridylazo)resorcinol (PAR) and lanthanum fluoride (LaF₃) nanoparticles in an aqueous environment. The kinetics of PAR sorption were investigated, and the sorption isotherm of PAR at 20°C was obtained. Using the adsorption model of Frumkin–Fowler–Guggenheim, the magnitude of lateral interaction energy among PAR molecules adsorbed on the LaF₃ surface and their sorption energy were calculated. Based on the sorption and spectral data, a structure for the grafted layer of PAR molecules on the surface of LaF₃ nanoparticles is proposed.