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Degradation Pathways of Various Plastics
Published in Hyunjung Kim, Microplastics, 2023
Hyunjung Kim, Sadia Ilyas, Gukhwa Hwang
Singlet oxygen can be formed by energy transfer from the excited triplet state of phenyl groups, from CTCs and impurities (internal impurities; modified groups, external impurities; added groups) or external impurities (added compounds) to molecular oxygen.
Optical Nanosensors
Published in Vinod Kumar Khanna, Nanosensors, 2021
The NP sensors based on this design include ions (H+, Ca2+, Mg2+, Zn2+, Fe3+, and K+), radicals (•OH radical), small molecules (O2, singlet oxygen, hydrogen peroxide, H2O2), etc. Singlet oxygen is the lowest excited state of the dioxygen molecule, which is less stable than the normal triplet oxygen. Its lifetime in solution is in the microsecond range (3 μs in water to about 700 μs in deuterated benzene, C6D6). It undergoes several reactions with organic molecules (the ene reaction and the Diels–Alder reaction).
The Ubiquitous Lead—Biological Effects, Toxicity, and Management
Published in Debasis Bagchi, Manashi Bagchi, Metal Toxicology Handbook, 2020
Sreejayan Nair, Debasis Bagchi
Molecular oxygen is a biradical, as its outermost shell contains two unpaired electrons in different orbitals. Because these two electrons are of similar spin and are in two different shells, the oxygen molecule is largely resistant to reduction. Any agent that reduces oxygen should provide a single electron in the opposite spin. This spin and orbital restriction can be countered by transition metal ions such as iron that can undergo redox reaction. A single electron reduction of molecular oxygen thus leads to the production of singlet oxygen. Singlet oxygen can accept another electron to form hydrogen peroxide, and hydrogen peroxide undergoes the classical Fenton reaction to produce hydroxyl radical. Singlet oxygen, hydrogen peroxide, and hydroxyl radicals (collectively referred to as reactive oxygen species) can oxidize biomolecules (proteins and carbohydrates), peroxidize lipid molecules (lipid peroxidation), crosslink DNA, and cause proinflammatory gene expression. Collectively this event is called “oxidative stress.”
An experimental investigation on the influence of storage container on the development of oxidised products in biofuel
Published in Biofuels, 2023
Paweł Grabowski, Magdalena Szostek
The peroxide anion is important in the process of reducing oxygen to generate other reactive oxygen species, such as hydrogen peroxide, the hydroxyl radical, and singlet oxygen. From the disproportionation of the peroxide anion, hydrogen peroxide is formed, which is a less reactive oxidant than peroxide. Superoxide dismutase catalyzes the dismutation of superoxide anions to hydrogen peroxide and oxygen. Hydroxyl radicals are formed from the radiolysis of water or the decomposition of hydrogen peroxide by ultraviolet (UV) light, catalase, or peroxidase. The reaction of a superoxide anion and hydrogen peroxide in the presence of transition metals produces a very reactive hydroxyl radical and singlet oxygen in the Haber-Weiss reaction. Singlet oxygen is most often produced by photosensitization reactions. A photosensitizer such as chlorophyll absorbs light energy and transfers it to triplet oxygen to form singlet oxygen. Peroxide radicals react with other peroxide radicals and produce singlet oxygen (Russell mechanism) [16].
Metallo-phthalocyanines containing triazole substituents: Synthesis, spectroscopic and photophysicochemical properties
Published in Journal of Coordination Chemistry, 2022
Ümit Demirbaş, Dilek Öztürk, Hakkı Türker Akçay, Mahmut Durmuş, Emre Menteşe, Halit Kantekin
The photodynamic therapy involves singlet oxygen species. Singlet oxygen is produced by energy transfer between the triplet state of a photosensitizer and ground state of molecular oxygen [34]. Singlet oxygen quantum yields (ΦΔ) of 4–6 were calculated by using 1,3-diphenylisobenzofuran (DPBF) as a singlet oxygen quencher. While there was no spectral change in the Q band of phthalocyanines during the measurement, the absorption band of DPBF at 417 nm decreased with light radiation. The changes of absorption spectra of 4–6 during determination of the singlet oxygen quantum yields are shown in Figure 4 and calculated results are given in Table 1. Phthalocyanine 6 showed the highest singlet oxygen quantum yield due to the d10 configuration of zinc(II). This value is higher than singlet oxygen quantum yield of Std-ZnPc. Compound 5 exhibited the lowest singlet oxygen quantum yield and 4 showed moderate singlet oxygen quantum yield. Thus 6 is suitable for PDT applications.
Intrinsic catalytic activity of rhodium nanoparticles with respect to reactive oxygen species scavenging: implication for diminishing cytotoxicity
Published in Journal of Environmental Science and Health, Part C, 2018
Gao-Juan Cao, Yingmei Chen, Xiaohe Chen, Peilin Weng, Rong-Guang Lin
Singlet oxygen (1O2), a mild yet efficient oxidant, is correlated strongly to many oxidation reactions with undesirable consequences. It is meaningful to exploit effective 1O2 scavenger. Here, we selected TEMP as a spin trap for characterization of 1O2. TEMP itself is ESR-silent, but it can specifically capture 1O2 to yield a nitroxide radical, TEMPONE, which characteristically have three lines with equal intensities. To confirm the 1O2 scavenging by Rh NPs, we used TiO2 and ZnO NPs as photosensitizes for the generation of 1O2 (Figure 4). A well-known 1O2 scavenger, NaN3, was also employed to test the scavenging effects under these experimental conditions. Rh NPs inhibited the generation of singlet oxygen in concentration-dependent fashion under neutral condition.