Photocatalysis has emerged as an effective approach to sustainably convert biomass into value-added products.CoSe_(2)is a promising nonprecious,efficient cocatalyst for photooxidation,which can facilitate the separati...Photocatalysis has emerged as an effective approach to sustainably convert biomass into value-added products.CoSe_(2)is a promising nonprecious,efficient cocatalyst for photooxidation,which can facilitate the separation of photogenerated electron–holes,increase the reaction rates,and enhance photocatalytic efficiency.In this work,we synthesized a stable and efficient photocatalysis system of CoSe_(2)/g-C_(3)N_(4)through attaching CoSe_(2)on g-C_(3)N_(4)sheets,with a yield of 50.12%for the selective photooxidation of xylose to xylonic acid.Under light illumination,the photogenerated electrons were prone to migrating from g-C_(3)N_(4)to CoSe_(2)due to the higher work function of CoSe_(2),resulting in the accelerated separation of photogenerated electron–holes and the promoted photooxidation.Herein,this study reveals the unique function of CoSe_(2),which can significantly promote oxygen adsorption,work as an electron sink and accelerate the generation of ·O_(2)^(-),thereby improving the selectivity toward xylonic acid over other by-products.This work provides useful insights into the design of selective photocatalysts by engineering g-C_(3)N_(4)for biomass high-value utilization.展开更多
It is highly challenging to precisely compare the impacts of anthropogenic pollutants on the photooxidation of isomeric volatile organic compounds with respect to molecular compositions and particle number/mass concen...It is highly challenging to precisely compare the impacts of anthropogenic pollutants on the photooxidation of isomeric volatile organic compounds with respect to molecular compositions and particle number/mass concentrations of secondary organic aerosols(SOAs).In this study,we conducted a series of well-defined indoor chamber experiments to compare the effects of NO_(x)(NO and NO_(2))on the photooxidation of isomeric monoterpenes ofβ-pinene and limonene.For the photooxidation ofβ-pinene with NO_(x),the increase of the initial concentrations of NO([NO]_(0))shows a monotonous suppression of the particle mass concentration,whereas the increase of[NO_(2)]_(0) shows a monotonous enhancement of the particle mass concentration.For the photooxidation of limonene with NO_(x),the increase of[NO]_(0) exhibits a monotonous suppression of the particle mass concentration,whereas the increase of[NO_(2)]_(0) shows a parabolic trend of the particle mass concentration.Utilizing a newly developed vacuum ultraviolet free electron laser(VUV-FEL),the online threshold photoionization mass spectrometry reveals a series of novel compounds at molecular weight(MW)=232 and 306 for theβ-pinene+NO_(x) system and MW=187,261,280,and 306 for the limonene+NO_(x) system.The molecular structures and formation pathways of these species were inferred,which led to the prediction of the diversity and difference of SOA products(i.e.,ester and peroxide accretion products)formed from different monoterpene precursors.To improve the predictions of future air quality,it is recommended that climate models should incorporate the NO_(x)-driven diurnal photooxidation of monoterpenes for SOA formation mechanisms.展开更多
Direct conversion of methane into C1 oxygenates under mild condition with high selectivity is a desired goal in the field of energy and chemistry.But it still remains a great challenge due to the intrinsic inertness o...Direct conversion of methane into C1 oxygenates under mild condition with high selectivity is a desired goal in the field of energy and chemistry.But it still remains a great challenge due to the intrinsic inertness of methane originating from strong C-H bonds(104 kcal/mol),low solubility in the solvent,and poor selectivity.Herein,we present a direct single-step conversion of methane to formic acid(HCOOH)using molecular oxygen(O_(2)) as the oxidant under gentle conditions on a decatungstate-doped porous cerium metal-organic framework(Ce-MOF),W_(10)@Ce-bpdc.The HCOOH yield of W_(10)@Ce-bpdc-2 was 155μmol/gcatat room temperature in 12 h.The process and mechanism of conversion of methane to HCOOH was revealed by spectroscopic characteristics and controlled experiments.In the presence of light,O_(2)was converted to H_(2)O_(2)by catalyst and then to·OH radicals in solution,which interact with methane and undergo intermediates to produce HCOOH.Our experiment provides a new way to catalyze methane in combination with MOF and polyoxometalates(POMs).展开更多
Elucidating the effects of anthropogenic pollutants on the photooxidation of biogenic volatile organic compounds is crucial to understanding the fundamental mechanisms of secondary organic aerosol(SOA)formation.Here,t...Elucidating the effects of anthropogenic pollutants on the photooxidation of biogenic volatile organic compounds is crucial to understanding the fundamental mechanisms of secondary organic aerosol(SOA)formation.Here,the impacts of NO_(2)and SO_(2)on SOA formation from the photooxidation of a representative monoterpene,β-pinene,were investigated by a number of laboratory studies.The results indicated NO_(2)enhanced the SOA mass concentrations and particle number concentrations under both low and highβ-pinene conditions.This could be rationalized that the increased O_(3)concentrations upon the NO_(x)photolysis was helpful for the generation of more amounts of O_(3)-oxidized products,which accelerated the SOA nucleation and growth.Combing with NO_(2),the promotion of the SOA yield by SO_(2)was mainly reflected in the increase of mass concentration,which might be due to the elimination of the newly formed particles by the initially formed particles.The observed low oxidation degree of SOA might be attributed to the fast growth of SOA,resulting in the uptake of less oxygenated gas-phase species onto the particle phase.The present findings have important implications for SOA formation affected by anthropogenic–biogenic interactions in the ambient atmosphere.展开更多
In this study,diodo boron dipyrromethene(BODIPY)is employed a8 the energy donor and 3,4,9,10-perylene tetracarboxylic dianhydride(PDA)as the energy acceptor,enabling the synthesis of two new compounds:a BODIPY-perylen...In this study,diodo boron dipyrromethene(BODIPY)is employed a8 the energy donor and 3,4,9,10-perylene tetracarboxylic dianhydride(PDA)as the energy acceptor,enabling the synthesis of two new compounds:a BODIPY-perylene dyad named P1,and a triad named P2.To investigate the impact of the energy donor on the photophysical processes of the system,P1 comprises one diodo-BODIPY unit and one PDA unit,whereas P2 contains two diodo-BODIPY moieties and one PDA unit.Due to the good spectral complementarity between diiodo-BODIPY and PDA,these two compounds exhibit excellent light-harvesting capabilities in the 400-620 nm range.Steady-state fluorescence spectra demonstrate that when preferentially exciting the diodo-BODIPY moiety,it can effectively transfer energy to PDA;when selectively exciting the PDA moiety,quenching of PDA fluorescence is observed in both P1 and P2.Nanosecond transient absorption results show that both compounds can efficiently generate triplet excited states,which are located on the PDA part.The lifetimes of the triplet states for these two compounds are 103 and 89μs,respectively,significantly longer than that of diiodo-BODIPY.The results from the photooxidation experiments reveal that both P1 and P2 demonstrate good photostability and photooxidation capabilities,with P2 showing superior photooxidative efficiency.The photooxidation rate constant for P2 is 1.3 times that of P1,and its singlet oxygen quantum yield is 1.6 times that of P1.The results obtained here offer valuable insights for designing new photosensitizers.展开更多
Benzaldehyde(BnCHO)is a key component in dye production and a fundamental substance in the fine chemical sector,especially for making medicines and flavorings.Under ambient conditions,the synthesis of BnCHO through th...Benzaldehyde(BnCHO)is a key component in dye production and a fundamental substance in the fine chemical sector,especially for making medicines and flavorings.Under ambient conditions,the synthesis of BnCHO through the photo-oxidation of benzyl alcohol(BnOH)demonstrates significant application potential in fine chemical synthesis.Herein,we anchored different metal cations(M=Fe,Co,Cu,and Zn)into monolacunary polyoxometalate(POM)[SiW_(11)O_(39)]^(8-)(SiW)to form single-metal substituted-POMs(MSiWs).Furthermore,we have successfully dispersed these POMs uniformly onto polymeric carbon nitride nanosheets(CN).For BnOH photooxidation without adding extra oxidants such as H_(2)O_(2),the FeSiW/CN-7 exhibited excellent photocatalytic performance with the conversion of BnOH nearly 69.17%and a BnCHO yield of 532.13 mmol·g^(-1)within 12 h.The photo-oxidation performance of BnOH is 76 and 5 times higher than that of single CN and FeSiW,respectively.This catalytic system can maintain a high catalytic efficiency after 5 cycles,indicating that FeSiW/CN possesses high catalytic stability.The results suggest that the designed POM-based single-atom catalyst FeSiW/CN is a promising candidate for the preparation of BnCHO through photooxidation under mild conditions.展开更多
Thirty genotypes from rice germplasm were identified under photooxidation and shading condition and divided into four basic types : (1) cultivars tolerant to both photooxidation and shading, (2) cultivars tolerant to...Thirty genotypes from rice germplasm were identified under photooxidation and shading condition and divided into four basic types : (1) cultivars tolerant to both photooxidation and shading, (2) cultivars tolerant to photooxidation but sensitive to shading, (3) cultivars tolerant to shading but sensitive to photooxidation, and (4) cultivars sensitive to photooxidation and shading. A comparative study of photosynthetic characteristics of a cultivar (cv. Wuyujing 3) that is tolerant and a cultivar (cv. Xiangxian) that is sensitive to both photoinhibition and shading showed that the photochemical efficiency of PSⅡ ( F v/F m ) and the content of PSⅡ_D1 protein in the tolerant cultivar “Wuyujing 3” decreased less under photoinhibition conditions as compared with “Xiangxian”. Under photooxidation conditions, superoxide dismutase was induced rapidly to a higher level and the active oxygen O - built up to a lower level in “Wuyujing 3” than in “Xiangxian”. At the same time, the photosynthetic rate decreased by 23% in “Wuyujing 3” vs. 64% in “Xiangxian”. Shading (20% natural light) during the booting stage caused only small decreases (7%-13%) in RuBisCO activity and the photosynthetic rate in “Wuyujing 3” but showed marked decreases (57%-64%) in “Xiangxian” which corresponded to the decreases in grain yield in the two cultivars (38% and 73%, respectively). The correlation analysis showed that the tolerance to photooxidation is mainly related to PSⅡ_D1 and that to shading is mainly related to RuBisCO activity. This study provided a simple and effective screening method and physiological basis for crop breeding in enhancing tolerance to both high and low radiation.展开更多
Using various high-yield rices (Oryza sativa L.) such as japonica cultivar 9516, two parental line hybrid rice between subspecies with more japonica element Peiai 64/E32, Liangyoupeijiu (Peiai 64/9311), and indica hyb...Using various high-yield rices (Oryza sativa L.) such as japonica cultivar 9516, two parental line hybrid rice between subspecies with more japonica element Peiai 64/E32, Liangyoupeijiu (Peiai 64/9311), and indica hybrid rices X07S/Zihui 100, Gangyou 881, Shanyou 63 as the materials, the characteristics of chlorophyll fluorescence and membrane-lipid peroxidation of detached leaves at booting stage under photooxidation conditions were studied. In comparison with indica hybrid rice, after the photooxidation treatment, the primary photochemical efficiency of PS II (F-v/F-m), quantum yield of linear electron transport of PS II (Phi(PSII)) and photochemical quenching coefficient (qP) in japonica cultivar and hybrid rice with japonica decreased less. This indicated that high-yield rice with japonica was able to maintain higher capability of light energy conversion, resulting in the alleviation of photoinhibition. Meanwhile, the higher activities of protective enzymes such as superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) led to the less accumulation of endogenous active oxygen (O-(2)(radical anion), H2O2) and less content of the malondialdehyde (MDA) and the less decline of chlorophyll and protein contents, indicating a stronger tolerance to photooxidation. The changes in contents of chlorophyll and protein among various nee cultivars during photooxidation treatment were consistent with the decline of chlorophyll content from heading stage to maturation stage under natural conditions. Statistical analysis showed that there was a significant correlation between the indexes of tolerance to photooxidation and the rate of seed setting, implying that the cultivar tolerated to photooxidation had higher resistance to early aging of leaf. These results suggested that from a view of superhigh-yield breeding, considering both the utilization of heterosis and the resistance to early aging of leaf, introduction of japonica element tolerating to photooxidation into the rice sterile line (maternal plant) is a breeding strategy worthy to pay great attention to.展开更多
The switch from C-3 to CAM pathway was induced by water stress in a C-3/CAM intermediate plant Sedum spectabile Boreau. Typical CAM criteria were observed upon 15 d of withholding water. Leaf delta(13)C value (-%) and...The switch from C-3 to CAM pathway was induced by water stress in a C-3/CAM intermediate plant Sedum spectabile Boreau. Typical CAM criteria were observed upon 15 d of withholding water. Leaf delta(13)C value (-%) and water content showed a linear correlation fashion. Chlorophyll fluorescence parameters and antioxidative capacity were altered by water stress. Phi(PSII) and q(P) were reduced by 50% and 34% of the control, respectively, while NPQ rose ca. 180%. SOD activity and ability to scavenge DPPH. free radical went down but membrane permeability changed slightly. However, when an additional photooxidation by MV with high PPFD was carried out with leaf discs from watered (C-3 mode) and drought plants (CAM mode), q(P) and Phi(PSII) in leaves at induced CAM mode stage continuously decreased to a very low level. High 1 - q(P) value (0.86) and 1 - q(P)/NPQ ratio (>1) indicated the presence of high reduction state and unbalance of light energy budget. Together with the marked loss of membrane integral, it was evidenced that photooxidative damage was more serious in the induced CAM mode than in the C-3 mode. No advantage of photooxidation tolerance was found at the induced CAM expression stage of the facultative CAM plant, as compared with its C-3 mode stage, and also with the constitutive CAM plants reported previously. The differences in photooxidation sensitivity between the inducible CAM expressing plant and the constitutive CAM plant were discussed.展开更多
Hydroxyl radical （.OH）-initiated photooxidation reaction of toluene was carried out in a self-made smog chamber. Four individual seed aerosols such as ammonium sulfate, ammonium nitrate, sodium silicate and calcium ...Hydroxyl radical （.OH）-initiated photooxidation reaction of toluene was carried out in a self-made smog chamber. Four individual seed aerosols such as ammonium sulfate, ammonium nitrate, sodium silicate and calcium chloride, were introduced into the chamber to assess their influence on the growth of secondary organic aerosols （SOA）. It was found that the low concentration of seed aerosols might lead to high concentration of SOA particles. Seed aerosols would promote rates of SOA formation at the start of the reaction and inhibit its formation rate with prolonging the reaction time. In the case of ca. 9000 pt/cm^3 seed aerosol load, the addition of sodium silicate induced a same effect on the SOA formation as ammonium nitrate. The influence of the four individual seed aerosols on the generation of SOA decreased in the order of calcium chloride〉sodium silicate and ammonium nitrate〉ammonium sulfate.展开更多
Using six high yield varieties from different ecological districts in China the parameters of Chl fluorescence, the performance of membrane lipid peroxidation and the reduction of Chl content in flag leaf under natura...Using six high yield varieties from different ecological districts in China the parameters of Chl fluorescence, the performance of membrane lipid peroxidation and the reduction of Chl content in flag leaf under natural condition at the later developmental stages (from heading stage to mature stage). The results showed that Fv/Fm , decreased gradually, the excessive light energy led to the accumulation of active oxygen O2-, H2O2 and the product of membrane-lipid peroxidation, MDA, which resulted in the reduction of Chl content and early aging due to photooxidation during the course of senescence of flag leaf. This phenomenon varied obviously in rice varieties. When comparina japonica tolerant to photooxidation, Fv/Fm in indica shanyou 63 susceptible to photoxidation decreased significantly. An increase of active oxygen and a sharp drop of Chl content, resulted in 'yellowish' early aging and influenced filling and setting of rice grain. The mechanism on early aging in indica was related to light and temperature conditions in filling stages. On a fine day (above 251), PS Ⅱ reaction center exhibited a dynamic change on revisable inactivation. Under strong midday light, PS Ⅱ function in indica exhibited obvious down-regulation and photoinhibition; Under strong light with low temperature, PS Ⅱ resulted in photodamage, showing early aging, which were related to the degradation of PSⅡ - D1 Protein and the inhibition of the endogenous protecting system such as Xanthophyll cycle and the enzymes of scavenging active oxygen. The results suggested that for a view of high-yield breeding, on the basis of a good type-plant, giving consideration to the utilization of heterosis and resistance to early aging, selecting japonica or a sterile line with japonice genotype as maternal was a breeding strategy worthy of being paid more attention.展开更多
Smog chamber experiments were conducted to investigate the hygroscopicity of particles generated from photooxidation of α-pinene/NOx with different sulfate seed aerosols or oxidation conditions. Hygroscopicity of par...Smog chamber experiments were conducted to investigate the hygroscopicity of particles generated from photooxidation of α-pinene/NOx with different sulfate seed aerosols or oxidation conditions. Hygroscopicity of particles was measured by a tandem differential mobility analyzer （TDMA） in terms of hygroscopic growth factor （Gf）, with a relative humidity of 85%. With sulfate seed aerosols present, Gf of the aerosols decreased very fast before notable secondary organic aerosols （SOA） formation was observed, indicating a heterogeneous process between inorganic seeds and organic products might take place as soon as oxidation begins, rather than only happening after gas-aerosol partition of organic products starts. The final SOA-coated sulfate particles had similar or lower Gf than seed-free SOA. The hygroscopicity of the final particles was not dependent on the thickness but on the hygroscopicity properties of the SOA, which were influenced by the initial sulfate seed particles. In the two designed aging processes, Gf of the particles increased more significantly with introduction of OH radical than with ozone. However, the hygroscopicity of SOA was very low even after a long time of aging, implying that either SOA aging in the chamber was very slow or the Gf of SOA did not change significantly in aging. Using an aerosol composition speciation monitor （ACSM） and matrix factorization （PMF） method, two factors for the components of SOA were identified, but the correlation between SOA hygroscopicity and the proportion of the more highly oxidized factor could be either positive or negative depending on the speciation of seed aerosols present.展开更多
Under simulated atmospheric condition, photoomdation for HCFC-22 + H2O2, HCFC-22 + H2O2+O2, HFC-134A + H2O2 and HFC-134A + H2O2+ O2 systems were studied.H2O2 was irradiated by low pressure mercury lamp and produced OH...Under simulated atmospheric condition, photoomdation for HCFC-22 + H2O2, HCFC-22 + H2O2+O2, HFC-134A + H2O2 and HFC-134A + H2O2+ O2 systems were studied.H2O2 was irradiated by low pressure mercury lamp and produced OH radicals. The OH radicals can initiate photooxidation of HCFC-22 and 134A. The products of photooxidation were determined by a Fourier Transform infrared Spectroscopy with a 20ml long path cell. The products were COF2,CO2, HCI, H2O and HF for HCFC-22 + H2O2 system, HO, CO2, HCI and HF for HCFC-22 +H2O2 +O2 system, HCOF, CF3OOCF3,CO2, H2O and HF for HFC-134A +H2O2 system, HCOF, CO2, H2O, and HF for HFC-134A + H2O2+ O2 system. Based on those results, the mechanisms of photooxidation were suggested.展开更多
Photooxidation reaction of toluene in smog chamber systems was initiated by the UV radiation of tolucne/CH5ONO/NOx mixtures. The products of the photooxidation reaction of toluene and its subsequent reactions were ana...Photooxidation reaction of toluene in smog chamber systems was initiated by the UV radiation of tolucne/CH5ONO/NOx mixtures. The products of the photooxidation reaction of toluene and its subsequent reactions were analyzed directly utilizing Fourier transform infrared spectrometer （FTIR）. Detailed assignments to FTIR spectrum of gas-phase products were given. The information of some important functional groups in the products, such as, carbonyl groups （C-O）, hydroxyl groups （-OH）, carboxylic acid （- COOH）, C-C bonding, N O bonding and C-H bonding （C H）, was got from this analysis. These results were compared to those analyzed by aerosol time of flight mass spectrometer （ATOFMS）. It was found that there are some differcnccs between FTIR analysis of gas-phase products and that of particle-phase, for example, the products with carbonyl groups, which were connected to unsaturated chemical bonds, was relatively higher in the gas phase, while kctoncs, aldehydes, carboxylic acid and organonitrates were the dominant functional groups in the aerosol-phase reaction products. The possible reaction pathways of some important products in the gas phase were also discussed.展开更多
Copper phthalocyanine was selected as the photosensitizer to sensitize TiO2 in this experiment with furfural as the target pollutant. The composite catalysts（TiO2/CuPC） obtained showed a great activity under a xenon...Copper phthalocyanine was selected as the photosensitizer to sensitize TiO2 in this experiment with furfural as the target pollutant. The composite catalysts（TiO2/CuPC） obtained showed a great activity under a xenon lamp. By experiments, the optimal preparation conditions of the composite catalysts were set as follows ： the CuPC loading mass fraction was 1.5%, the mass fraction of acetylacetone was 0. 3% , and the stirring time was 10 h. UV-Vis diffuse reflectance spectra, XRD, and BET were used to characterize the properties of the composite catalysts, which showed that after loading CuPC on TiO2, the composite catalyst retained the same crystal structure as pure TiO2 and the wavelength range of its absorption spectrum was broadened to 600-700 nm while its surface area was smaller than that of the pure TiO2. Under the optimal conditions, 20 mg/L furfural solution was degraded by nearly 90% and TOC by about 70%. When the catalyst was reused 6 times, the activity of the catalyst was still retained by about 75%.展开更多
The effects of accelerated photooxidation on the molecular weight and thermal and mechanical properties of Cast PHBV and PHBV/Cloisite 30B(3 wt%)bionanocomposites are investigated herein.Through size exclusion chromat...The effects of accelerated photooxidation on the molecular weight and thermal and mechanical properties of Cast PHBV and PHBV/Cloisite 30B(3 wt%)bionanocomposites are investigated herein.Through size exclusion chromatography(SEC)analysis,a significant decrease in both weight and number average molecular weights was observed for all irradiated samples over time,resulting from the chain scission mechanism.Differential scanning calorimetry(DSC)data indicated a decrease in degree of crystallinity and melting temperature after UV exposure,with the appearance of double melting peaks related to the changes in the crystal structure of PHBV.Thermal stability,tensile and thermo-mechanical properties were also reduced consecutively in photooxidation,being more pronounced for Cast PHBV.This study shows that the incorporation of Cloisite 30B in PHBV provides a better resistance to photooxidation in comparison with the neat polymer.展开更多
The gas-phase organic compounds resulting from OH-initiated photooxidation of isoprene have been investigated on-line by VUV photoiortization mass spectrometry based on synchrotron radiation for the first time. The ph...The gas-phase organic compounds resulting from OH-initiated photooxidation of isoprene have been investigated on-line by VUV photoiortization mass spectrometry based on synchrotron radiation for the first time. The photoionization efficiency curves of the corresponding gaseous products as well as the chosen standards have been deduced by gating the interested peaks in the photoionization mass spectra while scanning the photon energy simultaneously, which permits the identification of the pivotal gaseous products of the photooxidation of isoprene, such as formaldehyde （10.84 eV）, formic acid （11.38 eV）, acetone （9.68 eV）, glyoxal （9.84 eV）, acetic acid （10.75 eV）, methacrolein （9.91 eV）, and methyl vinyl ketone （9.66 eV）. Proposed reaction mechanisms leading to the formation of these key products were discussed, which were completely consistent with the previous works of different groups. The capability of synchrotron radiation photoionization mass spectrometry to directly identify the chemical composition of the gaseous products in a simulation chamber has been demonstrated, and its potential application in related studies of atmospheric oxidation of ambient volatile organic compounds is anticipated.展开更多
The secondary organic aerosol(SOA)formation mechanism and physicochemical properties can highly be influenced by relative humidity(RH)and NOx concentration.In this study,we performed a laboratory investigation of the ...The secondary organic aerosol(SOA)formation mechanism and physicochemical properties can highly be influenced by relative humidity(RH)and NOx concentration.In this study,we performed a laboratory investigation of the SOA formation from toluene/OH photooxidation system in the presence or absence of NOx in dry and wet conditions.The chemical composition of toluene-derived SOA was measured using Aerodyne high-resolution timeof-flight aerosol mass spectrometer(HR-ToF-AMS).It was found that the mass concentration of toluene decreased with increasing RH and NOx concentration.However,the change of SOA chemistry composition(f_(44),O/C)with increased RH was not consistent in the condition with or without NOx.The light absorption and mass absorption coefficient(MAC)of the toluene-derived SOA only increased with RH in the presence of NOx.In contrast,MAC is invariant with RH in the absence of NOx.HR-ToF-AMS results showed that,in the presence of NOx,the increased nitro-aromatic compounds and N/C ratio concurrently caused the increase of SOA light absorption and O/C in wet conditions,respectively.The relative intensity of CHON and CHOxN family to the total nitrogen-containing organic compounds(NOCs)increased with the increasing RH,and be the major components of NOCs in wet condition.This work revealed a synergy effect of NOx and RH on SOA formation from toluene photooxidation.展开更多
Mercury is a globally distributed, environmental contaminant. Quantifying the retention and loss of mercury is integral for predicting mercury-sensitive ecosystems. There is little information on how dissolved organic...Mercury is a globally distributed, environmental contaminant. Quantifying the retention and loss of mercury is integral for predicting mercury-sensitive ecosystems. There is little information on how dissolved organic carbon（DOC） concentrations and particulates affect mercury photoreaction kinetics in freshwater lakes. To address this knowledge gap,samples were collected from ten lakes in Kejimkujik National Park, Nova Scotia（DOC： 2.6–15.4 mg/L）. Filtered（0.2 μm） and unfiltered samples were analysed for gross photoreduction, gross photooxidation, and net reduction rates of mercury using pseudo first-order curves. Unfiltered samples had higher concentrations（p = 0.04） of photoreducible divalent mercury（Hg（II）RED）（mean of 754 ± 253 pg/L） than filtered samples（mean of 482 ± 206 pg/L）;however, gross photoreduction and photooxidation rate constants were not significantly different in filtered or unfiltered samples in early summer. DOC was not significantly related to gross photoreduction rate constants in filtered（R2= 0.43; p = 0.08） and unfiltered（R2= 0.02; p = 0.71） samples; DOC was also not significantly related to gross photooxidation rate constants in filtered or unfiltered samples. However, DOC was significantly negatively related with Hg（Ⅱ）RED in unfiltered（R2= 0.53; p = 0.04）, but not in filtered samples（R2= 0.04;p = 0.60）. These trends indicate that DOC is a factor in determining dissolved mercury photoreduction rates and particles partially control available Hg（Ⅱ）RED in lake water. This research also demonstrates that within these lakes gross photoreduction and photooxidation processes are close to being in balance. Changes to catchment inputs of particulate matter and DOC may alter mercury retention in these lakes and could partially explain observed increases of mercury accumulation in biota.展开更多
Methyl-hydroxy-cyclohexadienyl radicals(OTAs)are the key products of the photooxidation of toluene,with implications for the fate of toluene.Hence,we investigated the photooxidation mechanisms and kinetics of three ma...Methyl-hydroxy-cyclohexadienyl radicals(OTAs)are the key products of the photooxidation of toluene,with implications for the fate of toluene.Hence,we investigated the photooxidation mechanisms and kinetics of three main OTAs(o-OTA,m-OTA,and p-OTA)with NO_(2)using quantum chemical calculations as well as the fate of OTAs under the different concentration ratios of NO_(2)and O_(2).The mechanism results show that the pathway of Habstraction by NO_(2)to anti-HONO(anti-H-abstraction)is more favorable than the syn-Habstraction pathway,because the strong interaction between OTAs and NO_(2)is formed in the transition states of the anti-H-abstraction pathways.The branching ratios of the antiH-abstraction pathways are more than 99%in the temperature range of 216-298 K.The total rate constant of the OTA-NO_(2)reaction is 9.9×10^(-12)cm^(3)/(molecule·sec)at 298 K,which is contributed about 90%by o-OTA+NO_(2),and the main products are o-cresol and anti-HONO.The half-lives of the OTA-NO_(2)reaction in some polluted areas of China are 35 times longer than those of the OTA-O_(2)reaction.In the atmosphere,the NO_(2^(-))and O_(2^(-))initiated reactions of OTAs have the same ability to form cresols as[NO_(2)]is up to 142.1 ppmV,which is impossible to achieve.It implies that under the experimental condition,the[NO_(2)]/[O_(2)]should be controlled to be less than 7.8×10^(-5)to simulate real atmospheric oxidation of toluene.Our results reveal that for the photooxidation of toluene,the yield of cresol is not affected by the concentration of NO_(2)under the atmospheric environment.展开更多
基金financial support by National Key Research and Development Project(Grant No.2023YFE0109600)Guangzhou Key Research and Development Program(Grant No.2023B03J1330)+5 种基金National Program for Support of Topnotch Young Professionals(Grant No.x2qsA4210090)Guangzhou Basic and Applied Basic Research Foundation(Grant No.2024A04J3413)National Natural Science Foundation of China(Grant No.32201499)State Key Laboratory of Pulp and Paper Engineering(Grant Nos.2023PY01 and 202215)Guangdong Basic and Applied Basic Research Foundation(Grant Nos.2023A1515012519 and 2023B1515040013)China Postdoctoral Science Foundation(Grant No.2023M732021).
文摘Photocatalysis has emerged as an effective approach to sustainably convert biomass into value-added products.CoSe_(2)is a promising nonprecious,efficient cocatalyst for photooxidation,which can facilitate the separation of photogenerated electron–holes,increase the reaction rates,and enhance photocatalytic efficiency.In this work,we synthesized a stable and efficient photocatalysis system of CoSe_(2)/g-C_(3)N_(4)through attaching CoSe_(2)on g-C_(3)N_(4)sheets,with a yield of 50.12%for the selective photooxidation of xylose to xylonic acid.Under light illumination,the photogenerated electrons were prone to migrating from g-C_(3)N_(4)to CoSe_(2)due to the higher work function of CoSe_(2),resulting in the accelerated separation of photogenerated electron–holes and the promoted photooxidation.Herein,this study reveals the unique function of CoSe_(2),which can significantly promote oxygen adsorption,work as an electron sink and accelerate the generation of ·O_(2)^(-),thereby improving the selectivity toward xylonic acid over other by-products.This work provides useful insights into the design of selective photocatalysts by engineering g-C_(3)N_(4)for biomass high-value utilization.
基金supported by the National Natural Science Foundation of China(Nos.22125303,92361302,92061203,22103082,22273101,22288201,and 21327901)the National Key Research and Development Program of China(No.2021YFA1400501)+3 种基金the Innovation Program for Quantum Science and Technology(No.2021ZD0303304)Dalian Institute of Chemical Physics(No.DICPI202437)Chinese Academy of Sciences(No.GJJSTD20220001)the International Partnership Program of CAS(No.121421KYSB20170012)。
文摘It is highly challenging to precisely compare the impacts of anthropogenic pollutants on the photooxidation of isomeric volatile organic compounds with respect to molecular compositions and particle number/mass concentrations of secondary organic aerosols(SOAs).In this study,we conducted a series of well-defined indoor chamber experiments to compare the effects of NO_(x)(NO and NO_(2))on the photooxidation of isomeric monoterpenes ofβ-pinene and limonene.For the photooxidation ofβ-pinene with NO_(x),the increase of the initial concentrations of NO([NO]_(0))shows a monotonous suppression of the particle mass concentration,whereas the increase of[NO_(2)]_(0) shows a monotonous enhancement of the particle mass concentration.For the photooxidation of limonene with NO_(x),the increase of[NO]_(0) exhibits a monotonous suppression of the particle mass concentration,whereas the increase of[NO_(2)]_(0) shows a parabolic trend of the particle mass concentration.Utilizing a newly developed vacuum ultraviolet free electron laser(VUV-FEL),the online threshold photoionization mass spectrometry reveals a series of novel compounds at molecular weight(MW)=232 and 306 for theβ-pinene+NO_(x) system and MW=187,261,280,and 306 for the limonene+NO_(x) system.The molecular structures and formation pathways of these species were inferred,which led to the prediction of the diversity and difference of SOA products(i.e.,ester and peroxide accretion products)formed from different monoterpene precursors.To improve the predictions of future air quality,it is recommended that climate models should incorporate the NO_(x)-driven diurnal photooxidation of monoterpenes for SOA formation mechanisms.
基金supported by the National Natural Science Foundation of China (Nos. 92261118, 92161103, 22071180)。
文摘Direct conversion of methane into C1 oxygenates under mild condition with high selectivity is a desired goal in the field of energy and chemistry.But it still remains a great challenge due to the intrinsic inertness of methane originating from strong C-H bonds(104 kcal/mol),low solubility in the solvent,and poor selectivity.Herein,we present a direct single-step conversion of methane to formic acid(HCOOH)using molecular oxygen(O_(2)) as the oxidant under gentle conditions on a decatungstate-doped porous cerium metal-organic framework(Ce-MOF),W_(10)@Ce-bpdc.The HCOOH yield of W_(10)@Ce-bpdc-2 was 155μmol/gcatat room temperature in 12 h.The process and mechanism of conversion of methane to HCOOH was revealed by spectroscopic characteristics and controlled experiments.In the presence of light,O_(2)was converted to H_(2)O_(2)by catalyst and then to·OH radicals in solution,which interact with methane and undergo intermediates to produce HCOOH.Our experiment provides a new way to catalyze methane in combination with MOF and polyoxometalates(POMs).
基金National Natural Science Foundation of China (Nos.22125303,92061203,and 22288201)the National Key Research and Development Program of China (No.2021YFA1400501)+3 种基金Innovation Program for Quantum Science and Technology (No.2021ZD0303304)Dalian Institute of Chemical Physics (No.DICP DCLS201702)Chinese Academy of Sciences (No.GJJSTD20220001)K.C.Wong Education Foundation (No.GJTD-2018-06)。
文摘Elucidating the effects of anthropogenic pollutants on the photooxidation of biogenic volatile organic compounds is crucial to understanding the fundamental mechanisms of secondary organic aerosol(SOA)formation.Here,the impacts of NO_(2)and SO_(2)on SOA formation from the photooxidation of a representative monoterpene,β-pinene,were investigated by a number of laboratory studies.The results indicated NO_(2)enhanced the SOA mass concentrations and particle number concentrations under both low and highβ-pinene conditions.This could be rationalized that the increased O_(3)concentrations upon the NO_(x)photolysis was helpful for the generation of more amounts of O_(3)-oxidized products,which accelerated the SOA nucleation and growth.Combing with NO_(2),the promotion of the SOA yield by SO_(2)was mainly reflected in the increase of mass concentration,which might be due to the elimination of the newly formed particles by the initially formed particles.The observed low oxidation degree of SOA might be attributed to the fast growth of SOA,resulting in the uptake of less oxygenated gas-phase species onto the particle phase.The present findings have important implications for SOA formation affected by anthropogenic–biogenic interactions in the ambient atmosphere.
基金supported by the Research Project for Outstanding Young People in Universities of Anhui Province(No.2023AH030099)the China Postdoctoral Science Foundation(No.2023M733378)+3 种基金the National Natural Science Foundation of China(No.21702042,No.22305059,No.22103010)the National University Students'Innovation and Entrepreneurship Training Program(No.202311059024)the Anhui Provincial Natural Science Foundation(No.2308085QB59)the Anhui Provincial Excellent Scientific Research and Innovation Team(No.2022AH010096).
文摘In this study,diodo boron dipyrromethene(BODIPY)is employed a8 the energy donor and 3,4,9,10-perylene tetracarboxylic dianhydride(PDA)as the energy acceptor,enabling the synthesis of two new compounds:a BODIPY-perylene dyad named P1,and a triad named P2.To investigate the impact of the energy donor on the photophysical processes of the system,P1 comprises one diodo-BODIPY unit and one PDA unit,whereas P2 contains two diodo-BODIPY moieties and one PDA unit.Due to the good spectral complementarity between diiodo-BODIPY and PDA,these two compounds exhibit excellent light-harvesting capabilities in the 400-620 nm range.Steady-state fluorescence spectra demonstrate that when preferentially exciting the diodo-BODIPY moiety,it can effectively transfer energy to PDA;when selectively exciting the PDA moiety,quenching of PDA fluorescence is observed in both P1 and P2.Nanosecond transient absorption results show that both compounds can efficiently generate triplet excited states,which are located on the PDA part.The lifetimes of the triplet states for these two compounds are 103 and 89μs,respectively,significantly longer than that of diiodo-BODIPY.The results from the photooxidation experiments reveal that both P1 and P2 demonstrate good photostability and photooxidation capabilities,with P2 showing superior photooxidative efficiency.The photooxidation rate constant for P2 is 1.3 times that of P1,and its singlet oxygen quantum yield is 1.6 times that of P1.The results obtained here offer valuable insights for designing new photosensitizers.
基金supported by National Natural Science Foundation of China(22071180)
文摘Benzaldehyde(BnCHO)is a key component in dye production and a fundamental substance in the fine chemical sector,especially for making medicines and flavorings.Under ambient conditions,the synthesis of BnCHO through the photo-oxidation of benzyl alcohol(BnOH)demonstrates significant application potential in fine chemical synthesis.Herein,we anchored different metal cations(M=Fe,Co,Cu,and Zn)into monolacunary polyoxometalate(POM)[SiW_(11)O_(39)]^(8-)(SiW)to form single-metal substituted-POMs(MSiWs).Furthermore,we have successfully dispersed these POMs uniformly onto polymeric carbon nitride nanosheets(CN).For BnOH photooxidation without adding extra oxidants such as H_(2)O_(2),the FeSiW/CN-7 exhibited excellent photocatalytic performance with the conversion of BnOH nearly 69.17%and a BnCHO yield of 532.13 mmol·g^(-1)within 12 h.The photo-oxidation performance of BnOH is 76 and 5 times higher than that of single CN and FeSiW,respectively.This catalytic system can maintain a high catalytic efficiency after 5 cycles,indicating that FeSiW/CN possesses high catalytic stability.The results suggest that the designed POM-based single-atom catalyst FeSiW/CN is a promising candidate for the preparation of BnCHO through photooxidation under mild conditions.
文摘Thirty genotypes from rice germplasm were identified under photooxidation and shading condition and divided into four basic types : (1) cultivars tolerant to both photooxidation and shading, (2) cultivars tolerant to photooxidation but sensitive to shading, (3) cultivars tolerant to shading but sensitive to photooxidation, and (4) cultivars sensitive to photooxidation and shading. A comparative study of photosynthetic characteristics of a cultivar (cv. Wuyujing 3) that is tolerant and a cultivar (cv. Xiangxian) that is sensitive to both photoinhibition and shading showed that the photochemical efficiency of PSⅡ ( F v/F m ) and the content of PSⅡ_D1 protein in the tolerant cultivar “Wuyujing 3” decreased less under photoinhibition conditions as compared with “Xiangxian”. Under photooxidation conditions, superoxide dismutase was induced rapidly to a higher level and the active oxygen O - built up to a lower level in “Wuyujing 3” than in “Xiangxian”. At the same time, the photosynthetic rate decreased by 23% in “Wuyujing 3” vs. 64% in “Xiangxian”. Shading (20% natural light) during the booting stage caused only small decreases (7%-13%) in RuBisCO activity and the photosynthetic rate in “Wuyujing 3” but showed marked decreases (57%-64%) in “Xiangxian” which corresponded to the decreases in grain yield in the two cultivars (38% and 73%, respectively). The correlation analysis showed that the tolerance to photooxidation is mainly related to PSⅡ_D1 and that to shading is mainly related to RuBisCO activity. This study provided a simple and effective screening method and physiological basis for crop breeding in enhancing tolerance to both high and low radiation.
文摘Using various high-yield rices (Oryza sativa L.) such as japonica cultivar 9516, two parental line hybrid rice between subspecies with more japonica element Peiai 64/E32, Liangyoupeijiu (Peiai 64/9311), and indica hybrid rices X07S/Zihui 100, Gangyou 881, Shanyou 63 as the materials, the characteristics of chlorophyll fluorescence and membrane-lipid peroxidation of detached leaves at booting stage under photooxidation conditions were studied. In comparison with indica hybrid rice, after the photooxidation treatment, the primary photochemical efficiency of PS II (F-v/F-m), quantum yield of linear electron transport of PS II (Phi(PSII)) and photochemical quenching coefficient (qP) in japonica cultivar and hybrid rice with japonica decreased less. This indicated that high-yield rice with japonica was able to maintain higher capability of light energy conversion, resulting in the alleviation of photoinhibition. Meanwhile, the higher activities of protective enzymes such as superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) led to the less accumulation of endogenous active oxygen (O-(2)(radical anion), H2O2) and less content of the malondialdehyde (MDA) and the less decline of chlorophyll and protein contents, indicating a stronger tolerance to photooxidation. The changes in contents of chlorophyll and protein among various nee cultivars during photooxidation treatment were consistent with the decline of chlorophyll content from heading stage to maturation stage under natural conditions. Statistical analysis showed that there was a significant correlation between the indexes of tolerance to photooxidation and the rate of seed setting, implying that the cultivar tolerated to photooxidation had higher resistance to early aging of leaf. These results suggested that from a view of superhigh-yield breeding, considering both the utilization of heterosis and the resistance to early aging of leaf, introduction of japonica element tolerating to photooxidation into the rice sterile line (maternal plant) is a breeding strategy worthy to pay great attention to.
文摘The switch from C-3 to CAM pathway was induced by water stress in a C-3/CAM intermediate plant Sedum spectabile Boreau. Typical CAM criteria were observed upon 15 d of withholding water. Leaf delta(13)C value (-%) and water content showed a linear correlation fashion. Chlorophyll fluorescence parameters and antioxidative capacity were altered by water stress. Phi(PSII) and q(P) were reduced by 50% and 34% of the control, respectively, while NPQ rose ca. 180%. SOD activity and ability to scavenge DPPH. free radical went down but membrane permeability changed slightly. However, when an additional photooxidation by MV with high PPFD was carried out with leaf discs from watered (C-3 mode) and drought plants (CAM mode), q(P) and Phi(PSII) in leaves at induced CAM mode stage continuously decreased to a very low level. High 1 - q(P) value (0.86) and 1 - q(P)/NPQ ratio (>1) indicated the presence of high reduction state and unbalance of light energy budget. Together with the marked loss of membrane integral, it was evidenced that photooxidative damage was more serious in the induced CAM mode than in the C-3 mode. No advantage of photooxidation tolerance was found at the induced CAM expression stage of the facultative CAM plant, as compared with its C-3 mode stage, and also with the constitutive CAM plants reported previously. The differences in photooxidation sensitivity between the inducible CAM expressing plant and the constitutive CAM plant were discussed.
基金Project supported by the National Natural Science Foundation of China(No.20477043)the Knowledge Innovation Program of Chinese Academy of Sciences(No.KZCX2-SW-H08).*
文摘Hydroxyl radical （.OH）-initiated photooxidation reaction of toluene was carried out in a self-made smog chamber. Four individual seed aerosols such as ammonium sulfate, ammonium nitrate, sodium silicate and calcium chloride, were introduced into the chamber to assess their influence on the growth of secondary organic aerosols （SOA）. It was found that the low concentration of seed aerosols might lead to high concentration of SOA particles. Seed aerosols would promote rates of SOA formation at the start of the reaction and inhibit its formation rate with prolonging the reaction time. In the case of ca. 9000 pt/cm^3 seed aerosol load, the addition of sodium silicate induced a same effect on the SOA formation as ammonium nitrate. The influence of the four individual seed aerosols on the generation of SOA decreased in the order of calcium chloride〉sodium silicate and ammonium nitrate〉ammonium sulfate.
基金supported in part by the National Key Basic Research and Development Plan of China(G1998010100).
文摘Using six high yield varieties from different ecological districts in China the parameters of Chl fluorescence, the performance of membrane lipid peroxidation and the reduction of Chl content in flag leaf under natural condition at the later developmental stages (from heading stage to mature stage). The results showed that Fv/Fm , decreased gradually, the excessive light energy led to the accumulation of active oxygen O2-, H2O2 and the product of membrane-lipid peroxidation, MDA, which resulted in the reduction of Chl content and early aging due to photooxidation during the course of senescence of flag leaf. This phenomenon varied obviously in rice varieties. When comparina japonica tolerant to photooxidation, Fv/Fm in indica shanyou 63 susceptible to photoxidation decreased significantly. An increase of active oxygen and a sharp drop of Chl content, resulted in 'yellowish' early aging and influenced filling and setting of rice grain. The mechanism on early aging in indica was related to light and temperature conditions in filling stages. On a fine day (above 251), PS Ⅱ reaction center exhibited a dynamic change on revisable inactivation. Under strong midday light, PS Ⅱ function in indica exhibited obvious down-regulation and photoinhibition; Under strong light with low temperature, PS Ⅱ resulted in photodamage, showing early aging, which were related to the degradation of PSⅡ - D1 Protein and the inhibition of the endogenous protecting system such as Xanthophyll cycle and the enzymes of scavenging active oxygen. The results suggested that for a view of high-yield breeding, on the basis of a good type-plant, giving consideration to the utilization of heterosis and resistance to early aging, selecting japonica or a sterile line with japonice genotype as maternal was a breeding strategy worthy of being paid more attention.
基金supported by the National Natural Science Foundation of China(No.20937004,21107060,21190054)the"Strategic Priority Research Program"of the Chinese Academy of Sciences(No.XDB05010102)supported by Toyota Motor Corporation and Toyota Central Research and Development Laboratories Inc
文摘Smog chamber experiments were conducted to investigate the hygroscopicity of particles generated from photooxidation of α-pinene/NOx with different sulfate seed aerosols or oxidation conditions. Hygroscopicity of particles was measured by a tandem differential mobility analyzer （TDMA） in terms of hygroscopic growth factor （Gf）, with a relative humidity of 85%. With sulfate seed aerosols present, Gf of the aerosols decreased very fast before notable secondary organic aerosols （SOA） formation was observed, indicating a heterogeneous process between inorganic seeds and organic products might take place as soon as oxidation begins, rather than only happening after gas-aerosol partition of organic products starts. The final SOA-coated sulfate particles had similar or lower Gf than seed-free SOA. The hygroscopicity of the final particles was not dependent on the thickness but on the hygroscopicity properties of the SOA, which were influenced by the initial sulfate seed particles. In the two designed aging processes, Gf of the particles increased more significantly with introduction of OH radical than with ozone. However, the hygroscopicity of SOA was very low even after a long time of aging, implying that either SOA aging in the chamber was very slow or the Gf of SOA did not change significantly in aging. Using an aerosol composition speciation monitor （ACSM） and matrix factorization （PMF） method, two factors for the components of SOA were identified, but the correlation between SOA hygroscopicity and the proportion of the more highly oxidized factor could be either positive or negative depending on the speciation of seed aerosols present.
文摘Under simulated atmospheric condition, photoomdation for HCFC-22 + H2O2, HCFC-22 + H2O2+O2, HFC-134A + H2O2 and HFC-134A + H2O2+ O2 systems were studied.H2O2 was irradiated by low pressure mercury lamp and produced OH radicals. The OH radicals can initiate photooxidation of HCFC-22 and 134A. The products of photooxidation were determined by a Fourier Transform infrared Spectroscopy with a 20ml long path cell. The products were COF2,CO2, HCI, H2O and HF for HCFC-22 + H2O2 system, HO, CO2, HCI and HF for HCFC-22 +H2O2 +O2 system, HCOF, CF3OOCF3,CO2, H2O and HF for HFC-134A +H2O2 system, HCOF, CO2, H2O, and HF for HFC-134A + H2O2+ O2 system. Based on those results, the mechanisms of photooxidation were suggested.
基金The National Natural Science Foundation of China (No. 20477043), the Knowledge Innovation Foundation of Chinese Academy ofSciences (No. KJCX2-SW-H08) and the National Synchrotron Graduation Innovation Foundation of Ministry of Education of China (Hefei)
文摘Photooxidation reaction of toluene in smog chamber systems was initiated by the UV radiation of tolucne/CH5ONO/NOx mixtures. The products of the photooxidation reaction of toluene and its subsequent reactions were analyzed directly utilizing Fourier transform infrared spectrometer （FTIR）. Detailed assignments to FTIR spectrum of gas-phase products were given. The information of some important functional groups in the products, such as, carbonyl groups （C-O）, hydroxyl groups （-OH）, carboxylic acid （- COOH）, C-C bonding, N O bonding and C-H bonding （C H）, was got from this analysis. These results were compared to those analyzed by aerosol time of flight mass spectrometer （ATOFMS）. It was found that there are some differcnccs between FTIR analysis of gas-phase products and that of particle-phase, for example, the products with carbonyl groups, which were connected to unsaturated chemical bonds, was relatively higher in the gas phase, while kctoncs, aldehydes, carboxylic acid and organonitrates were the dominant functional groups in the aerosol-phase reaction products. The possible reaction pathways of some important products in the gas phase were also discussed.
基金Jilin Scientific Research Committee Foundation(No 20010422)
文摘Copper phthalocyanine was selected as the photosensitizer to sensitize TiO2 in this experiment with furfural as the target pollutant. The composite catalysts（TiO2/CuPC） obtained showed a great activity under a xenon lamp. By experiments, the optimal preparation conditions of the composite catalysts were set as follows ： the CuPC loading mass fraction was 1.5%, the mass fraction of acetylacetone was 0. 3% , and the stirring time was 10 h. UV-Vis diffuse reflectance spectra, XRD, and BET were used to characterize the properties of the composite catalysts, which showed that after loading CuPC on TiO2, the composite catalyst retained the same crystal structure as pure TiO2 and the wavelength range of its absorption spectrum was broadened to 600-700 nm while its surface area was smaller than that of the pure TiO2. Under the optimal conditions, 20 mg/L furfural solution was degraded by nearly 90% and TOC by about 70%. When the catalyst was reused 6 times, the activity of the catalyst was still retained by about 75%.
文摘The effects of accelerated photooxidation on the molecular weight and thermal and mechanical properties of Cast PHBV and PHBV/Cloisite 30B(3 wt%)bionanocomposites are investigated herein.Through size exclusion chromatography(SEC)analysis,a significant decrease in both weight and number average molecular weights was observed for all irradiated samples over time,resulting from the chain scission mechanism.Differential scanning calorimetry(DSC)data indicated a decrease in degree of crystallinity and melting temperature after UV exposure,with the appearance of double melting peaks related to the changes in the crystal structure of PHBV.Thermal stability,tensile and thermo-mechanical properties were also reduced consecutively in photooxidation,being more pronounced for Cast PHBV.This study shows that the incorporation of Cloisite 30B in PHBV provides a better resistance to photooxidation in comparison with the neat polymer.
基金supported by the National Natural Science Foundation of China (No. 10979061,40975080)the Knowledge Innovation Foundation of Chinese Academy of Sciences (No. KJCX2-YW-N24)+1 种基金the Open Research Fund of Key Laboratory of Atmospheric Composition and Optical Radiation,Chinese Academy of Sciences (No. JJ10-04)the foundation of director of Anhui Institute of Optics and Fine Mechanics (No. Y03AG31147)
文摘The gas-phase organic compounds resulting from OH-initiated photooxidation of isoprene have been investigated on-line by VUV photoiortization mass spectrometry based on synchrotron radiation for the first time. The photoionization efficiency curves of the corresponding gaseous products as well as the chosen standards have been deduced by gating the interested peaks in the photoionization mass spectra while scanning the photon energy simultaneously, which permits the identification of the pivotal gaseous products of the photooxidation of isoprene, such as formaldehyde （10.84 eV）, formic acid （11.38 eV）, acetone （9.68 eV）, glyoxal （9.84 eV）, acetic acid （10.75 eV）, methacrolein （9.91 eV）, and methyl vinyl ketone （9.66 eV）. Proposed reaction mechanisms leading to the formation of these key products were discussed, which were completely consistent with the previous works of different groups. The capability of synchrotron radiation photoionization mass spectrometry to directly identify the chemical composition of the gaseous products in a simulation chamber has been demonstrated, and its potential application in related studies of atmospheric oxidation of ambient volatile organic compounds is anticipated.
基金financially supported by National Key R&D Plan programs(No.2017YFC0212703)the National Natural Science Foundation of China(Nos.41773117,42005088)+2 种基金the China Postdoctoral Science Foundation(No.2019M661427)Fundamental Research Funds for the Central Universities,Director’s Fund of Key Laboratory of Geographic Information Science(Ministry of Education),East China Normal University(No.KLGIS2021C02)ECNU Happiness Flower Program
文摘The secondary organic aerosol(SOA)formation mechanism and physicochemical properties can highly be influenced by relative humidity(RH)and NOx concentration.In this study,we performed a laboratory investigation of the SOA formation from toluene/OH photooxidation system in the presence or absence of NOx in dry and wet conditions.The chemical composition of toluene-derived SOA was measured using Aerodyne high-resolution timeof-flight aerosol mass spectrometer(HR-ToF-AMS).It was found that the mass concentration of toluene decreased with increasing RH and NOx concentration.However,the change of SOA chemistry composition(f_(44),O/C)with increased RH was not consistent in the condition with or without NOx.The light absorption and mass absorption coefficient(MAC)of the toluene-derived SOA only increased with RH in the presence of NOx.In contrast,MAC is invariant with RH in the absence of NOx.HR-ToF-AMS results showed that,in the presence of NOx,the increased nitro-aromatic compounds and N/C ratio concurrently caused the increase of SOA light absorption and O/C in wet conditions,respectively.The relative intensity of CHON and CHOxN family to the total nitrogen-containing organic compounds(NOCs)increased with the increasing RH,and be the major components of NOCs in wet condition.This work revealed a synergy effect of NOx and RH on SOA formation from toluene photooxidation.
基金funded by NSERC (CGS-M scholarship to E.V. and discovery grant (Grant# 341960-2013) to N.O.)the Canada Research Chairs Program (Grant# 950-203477 to N.O.)the Canada Foundation for Innovation (Grant# 203477 to N.O.)
文摘Mercury is a globally distributed, environmental contaminant. Quantifying the retention and loss of mercury is integral for predicting mercury-sensitive ecosystems. There is little information on how dissolved organic carbon（DOC） concentrations and particulates affect mercury photoreaction kinetics in freshwater lakes. To address this knowledge gap,samples were collected from ten lakes in Kejimkujik National Park, Nova Scotia（DOC： 2.6–15.4 mg/L）. Filtered（0.2 μm） and unfiltered samples were analysed for gross photoreduction, gross photooxidation, and net reduction rates of mercury using pseudo first-order curves. Unfiltered samples had higher concentrations（p = 0.04） of photoreducible divalent mercury（Hg（II）RED）（mean of 754 ± 253 pg/L） than filtered samples（mean of 482 ± 206 pg/L）;however, gross photoreduction and photooxidation rate constants were not significantly different in filtered or unfiltered samples in early summer. DOC was not significantly related to gross photoreduction rate constants in filtered（R2= 0.43; p = 0.08） and unfiltered（R2= 0.02; p = 0.71） samples; DOC was also not significantly related to gross photooxidation rate constants in filtered or unfiltered samples. However, DOC was significantly negatively related with Hg（Ⅱ）RED in unfiltered（R2= 0.53; p = 0.04）, but not in filtered samples（R2= 0.04;p = 0.60）. These trends indicate that DOC is a factor in determining dissolved mercury photoreduction rates and particles partially control available Hg（Ⅱ）RED in lake water. This research also demonstrates that within these lakes gross photoreduction and photooxidation processes are close to being in balance. Changes to catchment inputs of particulate matter and DOC may alter mercury retention in these lakes and could partially explain observed increases of mercury accumulation in biota.
基金financially supported by Local Innovative and Research Teams Project of Guangdong Pearl River Talents Program(No.2017BT01Z032)Natural Science Foundation of Guangdong Province,China(No.2019B151502064)+1 种基金National Natural Science Foundation of China(Nos.42077189 and 4201001008)Innovation Team Project of Guangdong Provincial Department of Education(No.2017KCXTD012)
文摘Methyl-hydroxy-cyclohexadienyl radicals(OTAs)are the key products of the photooxidation of toluene,with implications for the fate of toluene.Hence,we investigated the photooxidation mechanisms and kinetics of three main OTAs(o-OTA,m-OTA,and p-OTA)with NO_(2)using quantum chemical calculations as well as the fate of OTAs under the different concentration ratios of NO_(2)and O_(2).The mechanism results show that the pathway of Habstraction by NO_(2)to anti-HONO(anti-H-abstraction)is more favorable than the syn-Habstraction pathway,because the strong interaction between OTAs and NO_(2)is formed in the transition states of the anti-H-abstraction pathways.The branching ratios of the antiH-abstraction pathways are more than 99%in the temperature range of 216-298 K.The total rate constant of the OTA-NO_(2)reaction is 9.9×10^(-12)cm^(3)/(molecule·sec)at 298 K,which is contributed about 90%by o-OTA+NO_(2),and the main products are o-cresol and anti-HONO.The half-lives of the OTA-NO_(2)reaction in some polluted areas of China are 35 times longer than those of the OTA-O_(2)reaction.In the atmosphere,the NO_(2^(-))and O_(2^(-))initiated reactions of OTAs have the same ability to form cresols as[NO_(2)]is up to 142.1 ppmV,which is impossible to achieve.It implies that under the experimental condition,the[NO_(2)]/[O_(2)]should be controlled to be less than 7.8×10^(-5)to simulate real atmospheric oxidation of toluene.Our results reveal that for the photooxidation of toluene,the yield of cresol is not affected by the concentration of NO_(2)under the atmospheric environment.
