Tuning photo-catalytic activities of TiO2 nanoparticles using dimethacrylate resins

Abstract

Objectives The unique photo-catalytic activities (PCAs) of titanium dioxide nanoparticles (TiO2 NPs) made them attractive in many potential applications in medical devices. The objective of this study is to optimize the benefits of PCAs of TiO2 NPs through varying chemical structures of dimethacrylate resins. Methods TiO2 NPs were functionalized to improve the PCAs and bonding to the resins. The PCAs of TiO2 NPs were evaluated using electron paramagnetic resonance (EPR) and UV-vis spectroscopy to determine the amount of the radicals generated and the energy required for their production, respectively. The beneficial effects of the radicals were assessed through: 1) the improvement of degree of vinyl conversion (DC) and 2) modification of resin hydrophilicity. One-way ANOVA with a 95% confidence interval was used to indicate the significant differences between the experimental groups. Results EPR and UV-vis results clearly showed that the functionalization of TiO2 NPs enhanced PCAs in terms of generating radicals under visible light irradiation. The presence of hydroxyl and carboxylic acid functionalities played an important role in DC enhancement and hydrophilicity modification. The DC could be increased up to 22% by adding only 0.1 wt% TiO2 NPs. Viscosity of the resins had minimal or no role in DC improvement through TiO2 NPs. In resins with abundant hydroxyl groups, radicals were more effective in making the resin more hydrophilic. Significance Knowledge learned from this study will help formulating nano-composites with optimized use of TiO2 PCAs as co-initiators for photo-polymerization, additives for making super-hydrophilic materials and/or antibacterial agents.

Biophysical characterization of functionalized titania nanoparticles and their application in dental adhesives

“…These results agree well with recent literature reports indicating that NP addition to resins significantly increase DC values [10,11].…”

“…The relative ROS intensity as a function of light irradiation time (Figure 2A) typically increased rapidly at first and then plateaued. The nonfunctionalized TiO 2 NPs (P25) reached a constant ROS intensity much faster than the functionalized NPs (AP25 and AceP25), probably due to recombination of the generated electrons and holes [10]. In the AP25 or AceP25 systems, functional groups on the surface of the NPs apparently slowed down the electron/hole recombination.…”

“…Therefore, a rougher surface may lead to increased entanglement between the resin and dentin, leading to more friction between the two components, which results in an overall improvement the bond strength. In addition, light irradiation may make nanocomposites more hydrophilic [10,52,53] which may enhance their interactions with teeth and result in a stronger bond. The two most important factors contributing to the increased mechanical strength of dental adhesives that contain functionalized TiO 2 NPs are the significantly increased DC values and the better integration of the resin nanocomposites with the dentin.…”

“…When TiO 2 NPs are irradiated with photons having energies larger than the TiO 2 bandgap (E g > 3 eV), electron/hole pairs form in the crystal lattice and different types and levels of ROS can be produced from the reactions of electron/hole pairs with the surrounding medium [4][5][6]. Because these ROS are strong oxidants, TiO 2 NPs have been used in diverse applications: selfcleaning surfaces [7,8], resin-based nanocomposites as reinforcing additives and co-initiators during photo-polymerization [9][10][11][12][13] and in the development of antibacterial medical devices [14][15][16]. There have been concerted research efforts directed toward improving the overall performance of dental materials through the selective incorporation of TiO 2 NPs into dental resins.…”

“…The strength and durability of dental adhesives are the key factors for ensuring a successful and durable dental restoration. Incorporation of functionalized TiO 2 NPs within dental adhesives may enhance the service life of dental restorations by promoting stronger bonding to human teeth [10,11].…”