Luminescent ZnO nanoparticles photoinitiators modified by 2-hydroxyethyl methacrylate to improve photo-curing depth and dispersibility

Abstract

ZnO nanoparticles (NPs) can be used as down-conversion luminescent NPs to assist photo-curing to achieve larger photo-curing depths, in which the luminescence and dispersibility were the pivotal factors. Here, a modification method combining 2-hydroxypropyl methacrylate (HEMA) and ZnO NPs using toluene diisocyanate (TDI) as a bridge was proposed. The Fourier transform infrared spectroscopy, X-ray diffraction, and Energy dispersive spectroscopy showed that the modification was successful. Then, the ratio of ZnO NPs, TDI, and HEMA was optimized and the best optimal ratio of ZnO: TDI: HEMA = 1:3:7.5 was obtained. The analysis of Malvern particle sizes exhibited the particle size changed from agglomerated 592.5 nm to modified 189.9 nm. And 10 times luminescent intensity was proved by the photoluminescence spectroscopy. In addition, the Fourier transform infrared spectroscopy, energy dispersive spectroscopy, and thermal gravimetric results confirmed the best grafting degree of 49.77%. The photo-curable samples that added with 0.35 wt% particles obtained the largest photo-curing depth, and the photo-curing depth of modified ZnO NPs was 19.2 mm, which was 4 mm larger than unmodified ZnO NPs. The modification had no effect on the properties of photo-curing films, and the scanning electron microscopy testified the better dispersibility of modified ZnO NPs. This study provided a new method that can improve luminescence and dispersibility at the same time. It helped the luminescent nanoparticle photoinitiators obtain larger photo-curing depths.