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Carbonaceous and Polysaccharide-Based Nanomaterials: Synthesis and Their Importance in Environmental Applications
Published in Surender Kumar Sharma, Nanohybrids in Environmental & Biomedical Applications, 2019
Jaise Mariya George, Ragam N. Priyanka, Beena Mathew
The generation of oxidative stress mediated by ROS formation induce the toxicity through free-radical mechanisms. The formation of highly reactive and short lived species cause difficulties in elucidating the proper mechanism of toxicity induced by nanoparticles. The direct isolation of ROS, with a short life of about 10−9 seconds is difficult without derivatization for structural identification. Commonly ESR spin trapping techniques are used to identify the formation of ROS from chemical reactions. The schematic representation (Figure 13.9) gives the idea about the toxicity generated by nanoparticles.
Antibacterial properties of Cu-doped TiO2 prepared by chemical and heat treatment of Ti metal
Published in Journal of Asian Ceramic Societies, 2021
Kanae Suzuki, Taishi Yokoi, Misato Iwatsu, Maiko Furuya, Kotone Yokota, Takayuki Mokudai, Hiroyasu Kanetaka, Masakazu Kawashita
Reactive oxygen species and free radicals are highly reactive, and it is difficult to measure them directly at around 25°C. Therefore, we measured these chemical species by electron spin resonance (ESR) using a spin trapping method. DMPO was used as a spin trapping agent. These adducts were measured using an ESR spectrometer (JES-FA-100, JEOL Ltd., Tokyo, Japan). The measurement conditions were as follows: microwave power, 4.0 mW; microwave frequency, 9428.954 MHz; magnetic width, 0.1 mT; field sweep width, ± 5 mT; field modulation, 100 kHz; modulation width, 0.1 mT; time constant, 0.03 s; and sweep time, 0.1 min. The samples were placed in a 24-well plate and 500 mm3 of DMPO solution (300 mol/m3) was added. The samples immersed in the DMPO solution were irradiated with visible light for 30 min under the same conditions as in the antibacterial property test using LED lighting. Subsequently, 200 mm3 of the DMPO solution, in which the sample was immersed, was removed and the reactive oxygen species were measured using the ESR spectrometer. We used TEMPOL to quantify the hydroxyl radicals. A control ESR spectrum was obtained from a solution without sample immersion and visible light irradiation.
Investigating the photocatalytic degradation property of Pt, Pd and Ni nanoparticles-loaded TiO2 nanotubes powder prepared via rapid breakdown anodization
Published in Environmental Technology, 2018
T. Manovah David, P. Wilson, R. Mahesh, S. Dhanavel, Shamima Hussain, S. Jacob Melvin Boby, A. Stephen, C. Ramesh, P. Sagayaraj
The Pt–TiO2 NTs are identified to possess better photocatalytic activity compared to the other samples under study; therefore, the hydroxyl radical EPR spectra of pristine TiO2 NTs and Pt–TiO2 NTs under UV light are compared to understand the process as illustrated in Figure 10. The spin trapping agent in the process is 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), an efficient method to trap ˙OH [17]. Notably, the 1:2:2:1 signature spectrum of DMPO-˙OH is stronger for pristine TiO2 NTs than Pt–TiO2 NTs. It is evident that the e− transfer from CB of TiO2 to Fermi level of Pt. This interaction shifts the Fermi level of Pt closer to that of the CB of TiO2, resulting in larger negative levels [58]. The phenomenon becomes beneficial as an excess of e− is available for interaction with the MB, thus degrading it at a faster rate.
Synthesis of nanocrystalline bismuth oxide and its visible photocatalytic activity in the degradation of an organic dye
Published in Inorganic and Nano-Metal Chemistry, 2018
Saranya Ramachandran, Arumugam Sivasamy
The in-situ generation of OH radicals in the reaction solution when the Bi2O3 catalyst is irradiated with visible light was investigated by EPR spectroscopy. In order to carry out this analysis, the highly reactive OH radicals, their lifetime must be increased. This is brought about by the use of DMPO (5,5-Dimethyl-1-pyrroline-N-Oxide), a spin trapping agent, was would trap the generated OH radicals so that they may be detected and analyzed. The obtained spectrum after 20 minutes of visible light irradiation is shown in Figure 7. Results show the formation of a quartet of 1:2:2:1 intensity ratio which is characteristic of the DMPO trapped OH radical. EPR analysis thus authenticates the formation of OH radicals in solution when the prepared Bi2O3 material is irradiated with visible light.