title: Tuning photo-catalytic activities of TiO2 nanoparticles using dimethacrylate resins.
abstract: OBJECTIVE
  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 0.1wt% 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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Dr Anthony Volpe Research Center, American Dental Association Foundation, Gaithersburg, MD 20899, USA. Electronic address: jsun@nist.gov.
authors.forename: Jirun
authors.initials: J
authors.lastname: Sun
authors.affiliation: Polymeric Materials Group, Materials and Structural Systems Division, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA.
authors.forename: Stephanie S
authors.initials: SS
authors.lastname: Watson
authors.affiliation: Dr Anthony Volpe Research Center, American Dental Association Foundation, Gaithersburg, MD 20899, USA.
authors.forename: David A
authors.initials: DA
authors.lastname: Allsopp
authors.affiliation: Polymeric Materials Group, Materials and Structural Systems Division, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA.
authors.forename: Debbie
authors.initials: D
authors.lastname: Stanley
authors.affiliation: Dr Anthony Volpe Research Center, American Dental Association Foundation, Gaithersburg, MD 20899, USA.
authors.forename: Drago
authors.initials: D
authors.lastname: Skrtic
mesh_terms: D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry*; D003764:Dental Materials / Q000737:chemistry*; D003799:Dental Stress Analysis; D004578:Electron Spin Resonance Spectroscopy; D055115:Light-Curing of Dental Adhesives; D008422:Materials Testing; D053768:Metal Nanoparticles / Q000737:chemistry*; D008689:Methacrylates / Q000737:chemistry; D015394:Molecular Structure; D018583:Pliability; D011092:Polyethylene Glycols / Q000737:chemistry; D058105:Polymerization; D011109:Polymethacrylic Acids / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry*; D017155:Wettability
chemical_list: D003188:Composite Resins; D003764:Dental Materials; D008689:Methacrylates; D011109:Polymethacrylic Acids; C020946:triethylene glycol dimethacrylate; C009495:titanium dioxide; D011092:Polyethylene Glycols; C074277:ethoxylated bis-phenol A dimethacrylate; D017438:Bisphenol A-Glycidyl Methacrylate; C005044:hydroxyethyl methacrylate; D014025:Titanium
keywords: Dental resins; Dimethacrylates; Free radical; Nano-composites; Photo-catalytic activities; Titanium dioxide nanoparticles; Wettability