Role of Fe Doping in Tuning the Band Gap of TiO_2 for the Photo-Oxidation-Induced Cytotoxicity Paradigm

摘要

UV-light-induced electron-hole (e-/h~+) pair generation with free radical production in TiO_2-based nanoparticles is a major conceptual paradigm for biological injury. However, to- date, this hypothesis has been difficult to experimentally verify due to the high energy of UV light that is intrinsically highly toxic to biological systems. Here, a versatile flame spray pyrolysis (FSP) synthetic process has been exploited to synthesize a library of iron-doped (0-10 wt%) TiO_2 nanoparticles. These particles have been tested for photoactivation-mediated cytotoxicity using near-visible light exposure. The reduction in TiO_2 band gap energy with incremental levels of Fe loading maintained the nanopartide crystalline structure in spite of homogeneous Fe distribution (demonstrated by XRD, HRTEM, SAED, EFTEM, and EELS). Photochemical studies showed that band gap energy was reciprocally tuned proportional to the Fe content The photo-oxidation capability of Fe-doped TiO_2 was found to increase during near-visible light exposure. Use of a macrophage cell line to evaluate cytotoxic and ROS production showed increased oxidant injury and cell death in parallel with a decrease in band gap energy. These findings demonstrate the importance of band gap energy in the phototoxic response of the cell to TiO_2 nanoparticles and reflect the potential of this material to generate adverse effects in humans and the environment during high-intensity light exposure.