Occurrence and distribution of hydroxylated isoprenoid glycerol dialkyl glycerol tetraethers(OH-GDGTs) in the Han River system, South Korea

We investigated the occurrence and distribution of terrestrial-derived hydroxylated isoprenoid glycerol dialkyl glycerol tetraethers(OH-GDGTs) in the Han River system and their potential impact on the application of the ring index of OH-GDGTs(RI-OH) as a sea surface temperature(SST) proxy in the eastern Yellow Sea. Thereby, we analyzed various samples collected along the Han River and from its surrounding areas(South Korea, n = 34). The OHGDGTs were found in all samples investigated. OH-GDGT-0 was the dominant OH-GDGT component in the estuary and marine samples while OH-GDGT-2 was generally dominant in the soils, the lake sediments and the river suspended particulate matter(SPM). Our results thus suggests a possible warm bias of the RI-OH-derived summer SSTs in the coastal zone to which a large amount of terrestrial organic matter is being supplied. Further studies are necessary to better assess the applicability of the RI-OH proxy in the eastern Yellow Sea.

Model Study on a Submerged Catalysis/Membrane Filtration System for Phenol Hydroxylation Catalyzed by TS-1

This ranearch is focused on the, develonment of a simnle design model of the submerged catalysis/membrane filtration （catalysis/MF） system for phenol hydroxylation over TS-1 based on the material balance of the phenol under steady state and the reported kinetic studies. Based on the developed model, the theoretical phenol Conversions at steady state could be calculated using the kinetic parameters obtained from the previous batch experiments. The theoretical conversions are in good agreement with the experimental data obtained in the submerged catalysis/MF system within relative error of ±5%. The model can be used to determine the optimal experimental conditions to carry out the phenol hydroxylation over TS-1 in the submerged catalysis/MF system.

Determination of hydroxyl radicals in TiO2/Ti photoelectrocatalytic oxidation system using Fe（phen）3^2＋ spectrophotometry

A new method of determining the cumulate concentration of hydroxyl radicals in the TiO2/Ti photoelectrocatalytic（PEC） oxidation system was established by o-phenanthroline-Fe（Ⅱ）（Fe（phen）3^2＋） spectrophotometry and using anion exchange membrane. Fe （phen）3^2＋ can be oxidized to o-phenanthroline-Fe（Ⅲ）（Fe（phen）3^3＋） by strong oxidization of hydroxyl radicals（·OH）. Then the cumulate concentration of hydroxyl radicals can be calculated through determining the change of the Fe（phen）3^3＋ absorbency at 509 nm. In addition, the research results showed the production rate of hydroxyl radicals was affected obviously by pH of solution, the cumulate concentration of hydroxyl radicals was the largest at nearby the initial pH 6.3 （isoelectric point）, and the change direction of pH after illumination tended to nearby isoelectric point.

Introducing hydroxyl groups to tailor the d-band center of Ir atom through side anchoring for boosted ORR and HER

Tuning the coordination atoms of central metal is an effective means to improve the electrocatalytic activity of atomic catalysts.Herein,iridium(Ir) is proposed to be asymmetrically anchored by sp-N and pyridinic N of hydrogen-substituted graphdiyne(HsGDY),and coordinated with OH as an Ir atomic catalyst(Ir_(1)-N-HsGDY).The electron structures,especially the d-band center of Ir atom,are optimized by these specific coordination atoms.Thus,the as-synthesized Ir_(1)-N-HsGDY exhibits excellent electrocatalytic performances for oxygen reduction and hydrogen evolution reactions in both acidic and alkaline media.Benefiting from the unique structure of HsGDY,IrN_(2)(OH)_(3) has been developed and demonstrated to act as the active site in these electrochemical reactions.All those indicate the fresh role of the sp-N in graphdiyne in producing a new anchor way and contributing to promote the electrocatalytic activity,showing a new strategy to design novel electrochemical catalysts.

Modified electronic structure and enhanced hydroxyl adsorption make quaternary Pt-based nanosheets efficient anode electrocatalysts for formic acid-/alcohol-air fuel cells

Surface/interface engineering of a multimetallic nanostructure with diverse electrocatalytic properties for direct liquid fuel cells is desirable yet challenging.Herein,using visible light,a class of quaternary Pt_(1)Ag_(0.1)Bi_(0.16)Te_(0.29)ultrathin nanosheets is fabricated and used as high-performance anode electrocatalysts for formic acid-/alcohol-air fuel cells.The modified electronic structure of Pt,enhanced hydroxyl adsorption,and abundant exterior defects afford Pt_(1)Ag_(0.1)Bi_(0.16)Te_(0.29)/C high intrinsic anodic electrocatalytic activity to boost the power densities of direct formic acid-/methanol-/ethanol-/ethylene glycol-/glycerol-air fuel cells,and the corresponding peak power density of Pt_(1)Ag_(0.1)Bi_(0.16)Te_(0.29)/C is respectively 129.7,142.3,105.4,124.3,and 128.0 mW cm^(-2),considerably outperforming Pt/C.Operando in situ Fourier transform infrared reflection spectroscopy reveals that formic acid oxidation on Pt_(1)Ag_(0.1)Bi_(0.16)Te_(0.29)/C occurs via a CO_(2)-free direct pathway.Density functional theory calculations show that the presence of Ag,Bi,and Te in Pt_(1)Ag_(0.1)Bi_(0.16)Te_(0.29)suppresses CO^(*)formation while optimizing dehydrogenation steps and synergistic effect and modified Pt effectively enhance H_(2)O dissociation to improve electrocatalytic performance.This synthesis strategy can be extended to 43 other types of ultrathin multimetallic nanosheets(from ternary to octonary nanosheets),and efficiently capture precious metals(i.e.,Pd,Pt,Rh,Ru,Au,and Ag)from different water sources.

Internal Polarization Field Induced Hydroxyl Spillover Effect for Industrial Water Splitting Electrolyzers

The formation of multiple oxygen intermediates supporting efficient oxygen evolution reaction(OER)are affinitive with hydroxyl adsorption.However,ability of the catalyst to capture hydroxyl and maintain the continuous supply at active sits remains a tremendous challenge.Herein,an affordable Ni2P/FeP2 heterostructure is presented to form the internal polarization field(IPF),arising hydroxyl spillover(HOSo)during OER.Facilitated by IPF,the oriented HOSo from FeP2 to Ni2P can activate the Ni site with a new hydroxyl transmission channel and build the optimized reaction path of oxygen intermediates for lower adsorption energy,boosting the OER activity(242 mV vs.RHE at 100 mA cm-2)for least 100 h.More interestingly,for the anion exchange membrane water electrolyzer(AEMWE)with low concentration electrolyte,the advantage of HOSo effect is significantly amplified,delivering 1 A cm^(-2)at a low cell voltage of 1.88 V with excellent stability for over 50 h.

Detection of Oxidants Such as Hydroxyl Radicals and Chlorine Electrogenerated on a BDD Electrode by Simple Methods

The aim of this work is to detect electrogenerated hydroxyl radicals and chlorine by simple and less expensive methods. Preparative electrolyses of perchloric acid (HClO4) and sodium chloride (NaCl) were performed on a boron-doped diamond (BDD) electrode. The hydroxyl radicals were quantified indirectly by assaying the samples from the HClO4 (0.1 M) electrolysis with a 10−4 M potassium permanganate solution. The investigations showed that the amount of hydroxyl radicals depends on the concentration of HClO4 and the current density. As for chlorine, a qualitative determination was carried out. A mixture of the electrolyte solution of HClO4 (0.1 M) + NaI (0.2 M) + 2 mL of hexane, taken in this order, leads to a purplish-pink coloration attesting to the presence of Cl2. The same test was carried out with NaBr and NaI giving pale and very pale pink colourations, respectively, showing that the intensity of the colouration depends on the strength of the oxidant present. In addition, oxidants were detected during the electrooxidation of metronidazole (MNZ). The results showed the participation of electrogenerated hydroxyl radicals. The generation of chlorine has also been proven. Furthermore, the degradation leads to a chemical oxygen demand (COD) removal rate of 83.48% and the process is diffusion-controlled.

Selective oxidative dehydrogenation of ethane to ethylene over a hydroxylated boron nitride catalyst

Boron nitride containing hydroxyl groups efficiently catalysed oxidative dehydrogenation of ethane to ethylene,offering rather high selectivity（95%） but only small amount of CO2 formation（0.4%） at a given ethane conversion of 11%.Even at high conversion level of 63%,the selectivity of ethylene retained at 80%,which is competitive with the energy-demanding industrialized steam cracking route.A long-term test for 200 h resulted in stable conversion and product selectivity,showing the excellent catalytic stability.Both experimental and computational studies have identified that the hydrogen abstraction of B-OH groups by molecular oxygen dynamically generated the active sites and triggered ethane dehydrogenation.

Flow Cytometric Evidence for Hydroxyl Radical-induced Apoptosis in Tobacco Protoplasts

Protoplasts prepared from tobacco (Nicotiana tabacum L., cultivar BY-2) suspension cells have similar morphological characteristics to those in animal cells. The hallmarks of apoptosis such as condensation and peripheral distribution of nuclei, TUNEL positive reaction, and DNA ladders were observed when tobacco protoplasts were treated with the hydroxyl radical generating system (1.0 mmol/L FeSO4/0.5 mmol/L H2O2). In animals, the loss of transmembrane potential (DeltaPsi(m)) and the exposure of phospholipid phosphatidylserine (PS) are believed to be the main apoptosis events. To test whether these significant processes take place in plants, flow cytometry was used to detect annexin V binding and changes in DeltaPsi(m). Results showed that the PS turned out from inner membrane and DeltaPsi(m) gradually decreased during the apoptosis. All these apoptotic characteristics proved that hydroxyl radicals can cause typical programmed cell death (PCD) in tobacco protoplasts and this design can be served as an effective experiment system to explore the mechanism of plant apoptosis.

Solubility and phase diagrams of hydroxyl manganese chloride

In the course of the basic research on the ammonia-evaporation reaction of manganese monoxide （MnO）, hydroxyl manganese chloride （Mn2（OH）3Cl） was found. The solubility and phase diagrams of the hydroxyl manganese chloride were investigated. The aqueous thermostat and vibrating bed were used to determine the solubility of hydroxyl manganese chloride in water, ammonium chloride and manganese chloride system, and the phase diagrams of multicomponent system were drawn. The research results indicate that hydroxyl manganese chloride has been produced in laboratory and is in favor of the solid-liquid separation at high temperature.

Comparison of hydroxyl radical-scavenging abilities between white rot fungus Lentinula edodes and five mildews on lignocellulose substance

The hydroxyl radical（-OH）-scavenging ability of culture filtrates from submerged culture of Lentinula edodes AX3 and five mildews on lignocellulose substance was analysed. Only L. edodes AX3 showed significant -OH-scavenging ability which reached 52.2% at about the 48th hour. All mildews could hardly scavenge -OH under the experimental conditions. -OH-scavenging ability is considered related to the mode and ability of lignocellulose degradation of a strain. The degradation or bioconversion products might be the substance base for.this effect.

Hydroxylation Polymorphisms of S─mephenytoin aDebrisoquin in Native Normal Chinese Zhuang MinorityVolunteers

S─mephenytoin and debrisoquin hydroxylation abilities were investigated in 118 normal Chinese Zhuang minority volunteers after co─administration po 100 mg racemic mephenytoin(MP)and 10 mg debrisoquin (DB). The ratio between S─and R─enantiomers of mephenytoin in urinewas determined by implication of GC─NPD and used as the measure of the drug hydroxylation. 2 ofthe 118 subjects had S/R ratios greater than 1.0 and were poor hydroxylators of S─mephenytoin. The frequency of S─mephenytoin poor metabolizers (PM) was 10.2%. No PM of debrisoquin was found in the volunteers. It indicated that there was no relationship between S─mephenytoin P(4′)─ hydroxylation and debrisoquin 4─hydroxylation polymorphisms in Chinese Zhuang Minority population. In addition, 16 of the 118 volunteers(4 PMs and 12 EMs of S-mephenytoin) were se─lected to conduct the elimination kinetic studies of racemic mephenytoin and debrisoquin in urine. The pharmacokinetic parameters of S─, R─mephenytoin, DB and 4─OH─DB were calculated.

Exchange Reaction Between Selenite and Hydroxyl Ion of Variable Charge Soil Surfaces: I. Electrolyte Species and pH Effects

Hydroxyl release of red soil and latosol surfaces was quantitatively measuredusing a self-made constant pH automated titration instrument, to study the changes of hydroxylrelease with different added selenite amounts and pH levels, and to study the effects ofelectrolytes on hydroxyl release. Hydroxyl release increased with the selenite concentration, with arapid increase at a low selenite concentration while slowing down at a high concentration. The pHwhere maximum of hydroxyl release appeared was not constant, shifting to a lower valus withincreasing selenite concentration. Hydroxyl release decreased with increasing electrolyteconcentration, and the decrease was very rapid at a low electrolyte concentration but slow at a highelectrolyte concentration. For NaClO_4, NaCl and Na_2SO_4, hydroxyl release was in the order ofNaClO_4 > NaCl >> Na_2SO_4, and the difference was very significant. But for NaCl, KCl and CaCl_2,the order of hydroxyl release was NaCl > KCl > CaCl_2, and the difference was smaller. The amount ofhydroxyl release from Xuwen latosol was greater than that from Jinxian red soil. Hydroxyl releaseexisted in a wider range of pH with Xuwen latosol than with Jinxian red soil, due to theirdifference in soil properties. However, both soils had similar curves of hydroxyl release,indicating the common characteristics of variable charge soils.

Hydroxylation of Benzene with Hydrogen Peroxide over Highly Efficient Molybdovanadophosphoric Heteropoly Acid Catalysts

Keggin type molybdovanadophosphoric heteropoly acids, H3＋nPMo12-nVnO40（n=1-3）, were prepared by a novel environmentally benign method, and their catalytic performances were evaluated via hydroxylation of benzene to phenol with hydrogen peroxide as oxidant in a mixed solvent of glacial acetic acid and acetonitrile. Various reaction parameters, such as reaction time, reaction temperature, ratio of benzene to hydrogen peroxide, concentration of aqueous hydrogen peroxide, ratio of glacial acetic acid to acetonitrile in solvent and catalyst con- centration, were changed to obtain an optimal reaction conditions. H3＋nPMo12-nVnO40（n=1-3） are revealed to be highly efficient catalyst for hydroxylation of benzene. In case of H5PMo10V2O40, a conversion of benzene of 34.5% with the selectivity of phenol of 100% can be obtained at the optimal reaction conditions.

Determination of atmospheric hydroxyl radical by HPLC coupled with electrochemical detection

The hydroxyl radical （·OH） plays a central role in the oxidation and removal of many atmospheric compounds. Measurement of atmospheric ·OH is very difficult because of its high reactivity and low atmospheric abundance. In this article, a simple and highly sensitive method, high performance liquid chromatography coupled with coulometric detection （HPLC-CD）, was developed to determine ·OH indirectly by determining its reaction products with salicylic acid （SAL）, 2,3-dihydroxybenzoic acid （2,3-DHBA）, and 2,5-dihydroxybenzoic acid （2,5-DHBA）. Under the optimum conditions for its determination, 2,3-DHBA and 2,5-DHBA could be well separated and the detection limits for 2,3-DHBA were 3 ×10^-10 mol/L and for 2,5-DHBA were 1.5 ×10^-10 mol/L, which were lower than most previous reports. This method was also applied to measure atmospheric hydroxyl radical levels and demonstrated the feasibility in clean and polluted air.

Singlet oxygen synergistic surface-adsorbed hydroxyl radicals for phenol degradation in CoP catalytic photo-Fenton

In recent years,there have been numerous studies on Fenton or Fenton-like reactions mediated by nonfree radicals such as singlet oxygen(1O_(2));however,there are few studies on the synergistic effect of 1O_(2) and free radicals on the degradation of organic molecules,such as phenol in Fenton reaction.In this study,a cocatalyst,CoP,commonly used in photocatalysis was synthesized using a simple two-step method,and a CoP/Fe^(2+)/AM1.5 system was constructed by introducing Fe^(2+)and simulated sunlight(AM1.5)irradiation.The newly constructed CoP/Fe^(2+)/AM1.5 system could effectively degrade various organic pollutants,including dyes,phenols,and antibiotics.Radical quenching experiments and electron paramagnetic resonance detection confirmed that there were three reactive oxygen species(ROS)in the CoP/Fe^(2+)/AM1.5 system,including·OH_(ads),·O_(2)^(-),and 1O_(2).Further,combined with the liquid chromatogram of phenol,its intermediate products,and the fluorescence diagram of o-hydroxybenzoic acid,it can be concluded that a synergistic effect exists between 1O_(2) and the surface-adsorbed·OH_(ads) in the CoP/Fe^(2+)/AM1.5 system.The controllable formation of surface 1O_(2) and·OH_(ads) was achieved through the oxidation(Co^(3+))and reduction(Pδ−)centers exposed on the CoP surface,and the synergistic effect between them results in phenol’s hydroxylation,ring-opening,and degradation.The study of this new mechanism provides a new perspective for revealing the surface interface reaction between ROS and organic pollutants.

Facile synthesis of Fe-containing graphitic carbon nitride materials and their catalytic application in direct hydroxylation of benzene to phenol

Fe-containing graphitic carbon nitride（Fe-g-C3N4） materials were synthesized via one-step pyroly-sis of FeCl3 and dicyandiamide. The physicochemical properties of the synthesized Fe-g-C3N4 sam-ples were characterized by N2 adsorption-desorption, X-ray diffraction, thermal gravimetric, Fourier transform infrared, UV-vis diffuse reflectance, X-ray photoelectron spectroscopy, and transmission electron microscopy. The Fe cations were anchored by nitrogen-rich g-C3N4, whereas the graphitic structures of g-C3N4 were retained after the introduction of Fe. As heterogeneous catalysts, Fe-g-C3 N4 exhibited good catalytic activity in the direct hydroxylation of benzene to phenol with H2O2, affording a maximum yield of phenol of up to 17.5%. Compared with other Fe- and V-containing g-C3N4 materials, Fe-g-C3N4 features a more convenient preparation procedure and higher catalytic productivity of phenol.

Hydroxyl radicals-mediated oxidative cleavage of the glycosidic bond in cellobiose by copper catalysts and its application to low-temperature depolymerization of cellulose

As the most abundant source of biomass in nature for sustainable production of fuels and chemicals,efficient depolymerization of cellulose under mild conditions,due to the difficulty in selective cleavage of itsβ-1,4-glycosidic bonds,still remains challenging.Here,we report a novel method for oxidative cleavage of the glycosidic bonds by free radicals.Probed by the cellobiose reaction,it was found that·OH radicals,generated from the decomposition of H2O2 catalyzed by CuSO4 or CuO/SiO2,were efficient for selective conversion of cellobiose to glucose and gluconic acid at a low temperature of 333 K,and their selectivities reached 30.0%and 34.6%,respectively,at 23.4%cellobiose conversion.Other radicals,such as·SO4?,also exhibited high efficacy in the cellobiose reaction.Mechanistic studies suggest that the oxidative cleavage of theβ-1,4-glycosidic bond by the free radicals involve formation of the carbon radical intermediate via abstraction of the H atom dominantly at the C1 position.Following this oxidative mechanism,treatment of microcrystalline cellulose with·OH by impregnation with H2O2 and CuSO4 catalyst at 343 K led to significant enhancement in its hydrolysis efficiency.These results demonstrate the effectiveness of this new method in the oxidative cleavage of glycosidic bonds,and its viability for the efficient depolymerization of cellulose at low temperatures,which can be further improved,for example,by exploring new free radicals and optimizing their reactivity and selectivity.

Exchange Reaction Between Selenite and Hydroxyl Ion of Variable Charge Soil Surfaces: Ⅱ. Kinetics of Hydroxyl Release

A self-made constant pH automated titration instrument was used to study thekinetics of hydroxyl release during selenite reacting with variable charge soils. The rate ofhydroxyl release was very rapid at the first several minutes, then gradually slowed down, and atlast did not change any more. The experimental data was well fitted by the Langmuir kineticequation, arid with increasing selenite concentration or decreasing solution pH, the reaction lastedlonger, the maximum of hydroxyl release (x_m) increased, and the binding constant (k) decreased.The time of hydroxyl release with Xuwen latosol was much longer than that with Jinxian red soil.

Mesoporous polyoxometalate-based ionic hybrid as a highly effective heterogeneous catalyst for direct hydroxylation of benzene to phenol

Self‐assembled mesoporous polyoxometalate‐based ionic hybrid catalyst,[PxyDim]2.5PMoV2,was prepared by combining p‐xylene‐tethered diimidazole ionic liquid[PxyDim]Cl2with Keggin‐structured V‐substituted polyoxometalate H5PMo10V2O40.The obtained hybrid was shown to be a mesostructured and hydrophobic material with good thermal stability.In the H2O2‐based hydroxylation of benzene to phenol,the hybrid showed extraordinary catalytic activity and rate,and quite stable reusability.The unique hydrophobic properties and mesoporous structure of the hybrid were responsible for its excellent catalytic performance.