FeNi nanoparticles cooperate with single-atom sites to drive non-radical fenton-like catalysis: Dominant singlet oxygen and electron transfer pathways for efficient wastewater purification

Synergistic dual-metal site Ni6MnO8 boosting regulated singlet oxygen and electron transfer pathways via persulfate activation for effective bisphenol A degradation.

Enhancement of peroxymonosulfate activation by humic acid-modified sludge biochar: Role of singlet oxygen and electron transfer pathway

Rose bengal (RB)-photosensitized protein crosslinking has been proposed for several applications in the eye. This study identifies oxygen-dependent and oxygen-independent mechanistic pathways in cornea for RB-photosensitized crosslinking to enhance its efficiency for ocular treatments. Rabbit corneas ex vivo were stained with 1 mM RB and irradiated at 532 nm. RB photobleaching, measured by spectrophotometry and linear tensile strength testing, were performed with and without oxygen present. The effects of sodium azide, D2O, arginine, and ascorbate were used to discriminate between mechanisms involving energy transfer (forming singlet oxygen) and electron transfer (forming radical ions). The influence of corneal depth on RB photobleaching was determined using inclined corneal incisions. RB photobleaching was greater in the presence than the absence of oxygen, enhanced by D2O and partially inhibited by azide, indicating a singlet oxygen pathway. Photobleaching without oxygen was enhanced by arginine and ascorbate and accompanied by a shift in the absorption to shorter wavelengths, suggesting that electron transfer initiates RB photodecomposition. The RB-photosensitized tensile strength increase in air was enhanced by D2O and inhibited by azide. In an O2-free environment, arginine was required for an increase in tensile strength, which matched that attained by irradiation in air without arginine, suggesting an efficient electron transfer pathway. Rapid photobleaching was observed below 80 to 120 μm only when arginine was present. These results indicate that RB photosensitizes crosslinking in cornea by both singlet oxygen and electron transfer mechanisms and that adding enhancers may increase the efficiency of this treatment.

Synergizing electron transfer with singlet oxygen to expedite refractory contaminant mineralization in peroxymonosulfate based heterogeneous oxidation system

Efficient peroxymonosulfate activation catalyzed by thiophene S and pyridinic N on ZIF-8-derived S, N co-doped carbon for 4-chlorophenol degradation: Performance and non-radical pathway mechanism

Efficient degradation of acetaminophen by activated peroxymonosulfate using Mn/C composites: Performance and mechanism

In situ N-doping engineered biochar catalysts for oxidation degradation of sulfadiazine via nonradical pathways: Singlet oxygen and electron transfer

Improving the non-free radical activated peroxymonosulfate capability of sludge biochar through sacrificial template method: Efficacy and mechanism evaluation

Highly-efficient peroxydisulfate activation by polyaniline-polypyrrole copolymers derived pyrolytic carbon for 2,4-dichlorophenol removal in water: Coupling mechanism of singlet oxygen and electron transfer

Activation of peroxydisulfate by alkali-activated algal biochar for the enhancement of enrofloxacin degradation in water: Role of singlet oxygen and electron transfer pathway

We describe a strategy by which reactive binding of a weakly bound, 'dynamically docked (DD)' complex without a known structure can be strengthened electrostatically through optimized placement of surface charges, and discuss its use in modulating complex formation between myoglobin (Mb) and cytochrome b(5) (b(5)). The strategy employs paired Brownian dynamics (BD) simulations, one which monitors overall binding, the other reactive binding, to examine [X --> K] mutations on the surface of the partners, with a focus on single and multiple [D/E --> K] charge reversal mutations. This procedure has been applied to the [Mb, b(5)] complex, indicating mutations of Mb residues D44, D60, and E85 to be the most promising, with combinations of these showing a nonlinear enhancement of reactive binding. A novel method of displaying BD profiles shows that the 'hits' of b(5) on the surfaces of Mb(WT), Mb(D44K/D60K), and Mb(D44K/D60K/E85K) progressively coalesce into two 'clusters': a 'diffuse' cluster of hits that are distributed over the Mb surface and have negligible electrostatic binding energy and a 'reactive' cluster of hits with considerable stability that are localized near its heme edge, with short Fe-Fe distances favorable to electron transfer (ET). Thus, binding and reactivity progressively become correlated by the mutations. This finding relates to recent proposals that complex formation is a two-step process, proceeding through the formation of a weakly bound encounter complex to a well-defined bound complex. The design procedure has been tested through measurements of photoinitiated ET between the Zn-substituted forms of Mb(WT), Mb(D44K/D60K), and Mb(D44K/D60K/E85K) and Fe(3+)b(5). Both mutants convert the complex from the DD regime exhibited by Mb(WT), in which the transient complex is in fast kinetic exchange with its partners, k(off) >> k(et), to the slow-exchange regime, k(et) >> k(off), and both mutants exhibit rapid intracomplex ET from the triplet excited state to Fe(3+)b(5) (rate constant, k(et) approximately 10(6) s(-1)). The affinity constants of the mutant Mbs cannot be derived through conventional analysis procedures because intracomplex singlet ET quenching causes the triplet-ground absorbance difference to progressively decrease during a titration, but this effect has been incorporated into a new procedure for computing binding constants. Most importantly, these measurements reveal the presence of fast photoinduced singlet ET across the protein-protein interface, (1)k(et) approximately 2 x 10(8) s(-1).

Fe-N co-doped highly graphitized biochar for peroxymonosulfate activation toward the degradation of persistent organic pollutants: Critical roles of singlet oxygen and electron transfer.

Some time ago, Schenck and Gollnick (1958) observed that ascaridole formation by hydroxy-anthraquinone-photosensitized oxygenation of α - terpinene, now recognized as a (4+2)-cycloaddition of singlet oxygen to the cyclic 1,3-diene system, was dependent on the number as well as on the positions of the OH groups in the anthraquinone moiety. Since naturally occurring quinones carrying hydroxy groups such as hypericin (for a recent review, see Duran and Song, 1986), cercosporin and dohistromin (Youngman and Elstner, 1984) are of importance in many biochemical processes, for example in photodynamic actions, it appears to be interesting to study the capability of model compounds such as anthraquinone and a series of its hydroxy derivatives as sensitizers of Type II (singlet oxygen) and Type I ((1) H-atom induced, and (2) electron transfer induced) photooxygenation reactions. Since the methods available for distinguishing between singlet oxygen and electron transfer induced oxygenation reactions have their severe drawbacks (Davidson et al., 1987), our approach is to apply simple, chemically well-defined systems which may be able to give a clear-cut answer with regard to the mechanisms involved. These results may be useful to photobiologists for their studies on phtooxygenations that proceed in the rather complicated biological systems. Although our only recently commenced studies on Type I and Type II photooxygenations sensitized by hydroxy-anthraquinones are far from being complete, first conclusions may be drawn from the following results.

Photosensitized oxygenation reactions of 1,3-dithianes through cooperative single electron transfer pathway and singlet oxygen pathway

Fullerene C60 supported on silica and γ-alumina (2% w/w C60/SiO2 and C60/Al2O3) sensitizes the photooxidation of ­alkenes via singlet oxygen and/or electron transfer mechanism, depending on the solvent and the substrate.