In situ photochemical formation of defect-related fluorescent ZrO2 nanoparticles in solution and within UV-cured EA/TPGDA coatings

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In this study, in situ photochemical synthesis of tetragonal-ZrO2 nanoparticles (t-ZrO2 NPs) was performed both in N,N-dimethyl formamide/water solution and within an epoxy diacrylate/tripropylene glycol diacrylate polymer matrix. The photoreduction of ZrCl4 to t-ZrO2 NPs was conducted, and upon UV irradiation, ZrCl4 undergoes photochemical decomposition facilitated by radicals generated from Irgacure 2959. These radicals promote Zr–Cl bond cleavage followed by hydrolysis and oxidation, leading to the formation of Zr–O–Zr linkages and, ultimately, ZrO2 NPs. The formation of ZrO2 NPs was confirmed by the appearance of a defect-related absorption band in the UV–Vis spectrum, accompanied by enhanced fluorescence emission arising from oxygen vacancies and Zr³+ centers. Thermogravimetric analysis was used to determine the thermal properties, and photopolymerization kinetics were studied using photo-differential scanning calorimetry, and the rate of polymerization and double bond conversions (DBC%) were calculated. Among all samples, the formulation containing 4 wt% ZrCl4 (A4) showed the highest polymerization efficiency, with a DBC of 81%. Crystallographic properties and surface morphology were evaluated by X-ray diffraction and FE-SEM analysis, respectively. Formulation A2 resulted in the most hydrophilic surface. Efficient photocatalytic degradation of methylene blue dye was achieved with 98% degradation in a solution containing t-ZrO2 NPs.