Aqueous-phase reactions between carbonyls and reduced nitrogen compounds play a considerable role in the formation of secondary organic aerosols and brown carbon in the atmosphere.However,the reported reaction rate co...Aqueous-phase reactions between carbonyls and reduced nitrogen compounds play a considerable role in the formation of secondary organic aerosols and brown carbon in the atmosphere.However,the reported reaction rate constants for these reactions have largely been limited to bulk aqueous-phase simulations,which may not accurately represent the real state of atmospheric cloud droplets.We employed an integration of optical tweezers and Raman spectroscopy to manipulate and analyze simulated cloud droplets(size range8000-10,000 nm),comprising a mixture of glyoxal and ammonium sulfate.This approach enabled us to delve into the intricate realm of their reaction kinetics at individual droplet level mimicking cloud droplets.Raman spectroscopy provided high temporal resolution(20 s)measurements of the changes in the amount of nitrogen-containing organics(or NOCs as represented by the C-N bond)within the droplets.The results indicate that the reaction follows first-order kinetics throughout the monitoring over 80-400 min.The average reaction rate constant for the formation of NOCs within the single droplet was determined to be(6.77±0.98)×10^(-5)s^(-1),up to three orders of magnitude higher than those through the bulk aqueous-phase simulations,especially at lower p H levels.Additionally,the reaction rate constant in single droplet increases with increasing p H,consistent with the trend previously reported for the bulk aqueous-phase simulations.The results highlight the difference of the reaction rate constant between bulk aqueous-phase and droplets,which would improve our understanding on the formation and impacts of secondary organic aerosols and brown carbon in atmospheric aqueous phase.展开更多
The construction of an acid resistant catalyst for synthesis of γ-valerolactone from levulinic acid in aqueous media is an important but highly challenging goal.Herein,an efficient Co@NCNT-800(after 800℃ pyrolysis) ...The construction of an acid resistant catalyst for synthesis of γ-valerolactone from levulinic acid in aqueous media is an important but highly challenging goal.Herein,an efficient Co@NCNT-800(after 800℃ pyrolysis) catalyst was constructed by confining Co in N-doped carbon nano-tubes(NCNT) from low cost materials by a facile strategy.Combined with the characterization results and control experiments,the in situ formed Co and Co-Ox, but not Co-Nx, proved to be the main synergistic active sites of the catalyst.It was also found that Co species are completely isolated within the bamboo-like NCNT,which could protect the metal nanoparticles from agglomeration and leaching in the strong acid reaction system.The γ-valerolactone yield of no less than 99.9% can be obtained under a relatively mild condition,and the catalytic performance has not been significantly reduced within five cycles.Therefore,this work may pave a way for the design of robust non-noble catalyst,and has potential for the production of γ-valerolactone from biomass in large-scale industries.展开更多
Organosulfate (OSA) nanoparticles,as secondary organic aerosol (SOA) compositions,are ubiquitous in urban and rural environments.Hence,we systemically investigated the mechanisms and kinetics of aqueous-phase reaction...Organosulfate (OSA) nanoparticles,as secondary organic aerosol (SOA) compositions,are ubiquitous in urban and rural environments.Hence,we systemically investigated the mechanisms and kinetics of aqueous-phase reactions of 1-butanol/1-decanol (BOL/DOL) and their roles in the formation of OSA nanoparticles by using quantum chemical and kinetic calculations.The mechanism results show that the aqueous-phase reactions of BOL/DOL start from initial protonation at alcoholic OH^(-)groups to form carbenium ions (CBs),which engage in the subsequent esterification or oligomerization reactions to form OSAs/organosulfites (OSIs) or dimers.The kinetic results reveal that dehydration to form CBs for BOL and DOL reaction systems is the rate-limiting step.Subsequently,about 18%of CBs occur via oligomerization to dimers,which are difficult to further oligomerize because all reactive sites are occupied.The rate constant of BOL reaction system is one order of magnitude larger than that of DOL reaction system,implying that relative short-chain alcohols are more prone to contribute OSAs/OSIs than long-chain alcohols.Our results reveal that typical long-chain alcohols contribute SOA formation via esterification rather than oligomerization because OSA/OSI produced by esterification engages in nanoparticle growth through enhancing hygroscopicity.展开更多
The challenge for single-atom catalysts in various C-C cross coupling reaction exists in the development of solid supporting materials.It has been desired tofind a supporting material designed in molecular level to an...The challenge for single-atom catalysts in various C-C cross coupling reaction exists in the development of solid supporting materials.It has been desired tofind a supporting material designed in molecular level to anchor a single-atom catalyst and provide high degree of dispersion and substrate access in aqueous media.Here,we prepared discrete cages of metal-organic polyhedra anchoring single Pd atom(MOP-BPY(Pd))and successfully performed a Suzuki-Miyaura cross coupling reaction with various substrates in aqueous media.It was revealed that each tetrahedral cage of MOP-BPY(Pd)has 4.5 Pd atoms on average and retained its high degree of dispersion up to 3 months in water.The coupling efficiencies of the Suzuki-Miyaura cross coupling reaction exhibited more than 90.0%for various substrates we have tested in the aqueous media,which is superior to those of the molecular Pd complex and metal-organic framework(MOF)anchoring Pd atoms.Moreover,MOP-BPY(Pd)was successfully recovered and recycled without performance degradation.展开更多
To investigate formation mechanisms of secondary organic carbon（SOC） in Eastern China,measurements were conducted in an urban site in Shanghai in the summer of 2015. A period of high O3 concentrations（daily peak 〉...To investigate formation mechanisms of secondary organic carbon（SOC） in Eastern China,measurements were conducted in an urban site in Shanghai in the summer of 2015. A period of high O3 concentrations（daily peak 〉 120 ppb） was observed, during which daily maximum SOC concentrations exceeding 9.0 μg/（C·m^3）. Diurnal variations of SOC concentration and SOC/organic carbon（OC） ratio exhibited both daytime and nighttime peaks. The SOC concentrations correlated well with Ox（= O3＋ NO2） and relative humidity in the daytime and nighttime, respectively, suggesting that secondary organic aerosol formation in Shanghai is driven by both photochemical production and aqueous phase reactions. Single particle mass spectrometry was used to examine the formation pathways of SOC. Along with the daytime increase of SOC, the number fraction of elemental carbon（EC） particles coated with OC quickly increased from 38.1% to 61.9% in the size range of 250–2000 nm, which was likely due to gas-to-particle partitioning of photochemically generated semi-volatile organic compounds onto EC particles. In the nighttime, particles rich in OC components were highly hygroscopic, and number fraction of these particles correlated well with relative humidity and SOC/OC nocturnal peaks. Meanwhile, as an aqueous-phase SOC tracer, particles that contained oxalate-Fe（III） complex also peaked at night. These observations suggested that aqueous-phase processes had an important contribution to the SOC nighttime formation. The influence of aerosol acidity on SOC formation was studied by both bulk and single particle level measurements, suggesting that the aqueous-phase formation of SOC was enhanced by particle acidity.展开更多
A field experiment was conducted in an intensive fog event between November 5 and November 8, 2009, in a heavily SO2-polluted area in North China Plain （NCP）, to measure SO2 and other air pollutants, liquid water co...A field experiment was conducted in an intensive fog event between November 5 and November 8, 2009, in a heavily SO2-polluted area in North China Plain （NCP）, to measure SO2 and other air pollutants, liquid water content （LWC） of fog droplets, and other basic meteorological parameters. During the fog period, the concentrations of SO2 showed large variability, which was closely related to the LWC in the fog droplets. The averaged concentration of SO2 during non-fog periods was about 25 ppbv, while during the fog period, it rapidly reduced to about 4-7 ppbv. Such large reduction of SO2 suggested that a majority of SO2 （about 70%-80%） had reverted from gas to aqueous phase on account of the high solubility of SO2 in water in the fog droplets. However, the calculated gas to aqueous phase conversion was largely underestimated by merely using the Henry＇s Law constant of SO2, thus suggesting that aqueous reaction of SO2 in fog droplets might play some important role in enhancing the solubility of SO2. To simplify the phenomenon, an ＂effective solubility coefficient＂ is proposed in this study. This variability of SO2 measurement during the extensive fog event provides direct evidence of oxidation of SO2 in fog droplets, thus providing important implications for better understanding of the acidity in clouds, precipitation, and fogs in NCP, now a central environmental focus in China due to its rapid economic development.展开更多
基金supported by the National Natural Science Foundation of China(Nos.42222705,42377097,and 22361162668)the National Key Research and Development Program of China(No.2022YFC3701101)+1 种基金the Youth Innovation Promotion Association CAS(No.2021354)Guangdong Foundation for Program of Science and Technology Research(No.2023B1212060049)。
文摘Aqueous-phase reactions between carbonyls and reduced nitrogen compounds play a considerable role in the formation of secondary organic aerosols and brown carbon in the atmosphere.However,the reported reaction rate constants for these reactions have largely been limited to bulk aqueous-phase simulations,which may not accurately represent the real state of atmospheric cloud droplets.We employed an integration of optical tweezers and Raman spectroscopy to manipulate and analyze simulated cloud droplets(size range8000-10,000 nm),comprising a mixture of glyoxal and ammonium sulfate.This approach enabled us to delve into the intricate realm of their reaction kinetics at individual droplet level mimicking cloud droplets.Raman spectroscopy provided high temporal resolution(20 s)measurements of the changes in the amount of nitrogen-containing organics(or NOCs as represented by the C-N bond)within the droplets.The results indicate that the reaction follows first-order kinetics throughout the monitoring over 80-400 min.The average reaction rate constant for the formation of NOCs within the single droplet was determined to be(6.77±0.98)×10^(-5)s^(-1),up to three orders of magnitude higher than those through the bulk aqueous-phase simulations,especially at lower p H levels.Additionally,the reaction rate constant in single droplet increases with increasing p H,consistent with the trend previously reported for the bulk aqueous-phase simulations.The results highlight the difference of the reaction rate constant between bulk aqueous-phase and droplets,which would improve our understanding on the formation and impacts of secondary organic aerosols and brown carbon in atmospheric aqueous phase.
基金the funding supported by the National Natural Science Foundation of China (21406103)Support plan for Excellent Youth Innovation Team in Shandong Colleges and Universities (2020KJC012)the Foundation of Liaocheng University (318011702)。
文摘The construction of an acid resistant catalyst for synthesis of γ-valerolactone from levulinic acid in aqueous media is an important but highly challenging goal.Herein,an efficient Co@NCNT-800(after 800℃ pyrolysis) catalyst was constructed by confining Co in N-doped carbon nano-tubes(NCNT) from low cost materials by a facile strategy.Combined with the characterization results and control experiments,the in situ formed Co and Co-Ox, but not Co-Nx, proved to be the main synergistic active sites of the catalyst.It was also found that Co species are completely isolated within the bamboo-like NCNT,which could protect the metal nanoparticles from agglomeration and leaching in the strong acid reaction system.The γ-valerolactone yield of no less than 99.9% can be obtained under a relatively mild condition,and the catalytic performance has not been significantly reduced within five cycles.Therefore,this work may pave a way for the design of robust non-noble catalyst,and has potential for the production of γ-valerolactone from biomass in large-scale industries.
基金financially supported by the Natural Science Foundation of Guangdong Province,China (No.2019B151502064)the National Natural Science Foundation of China (Nos.42077189 and 4201001008)+2 种基金the Local Innovative and Research Teams Project of Guangdong Pearl River Talents Program (No.2017BT01Z032)the Innovation Team Project of Guangdong Provincial Department of Education(No.2017KCXTD012)the Science and Technology Key Project of Guangdong Province,China (No.2019B110206002)。
文摘Organosulfate (OSA) nanoparticles,as secondary organic aerosol (SOA) compositions,are ubiquitous in urban and rural environments.Hence,we systemically investigated the mechanisms and kinetics of aqueous-phase reactions of 1-butanol/1-decanol (BOL/DOL) and their roles in the formation of OSA nanoparticles by using quantum chemical and kinetic calculations.The mechanism results show that the aqueous-phase reactions of BOL/DOL start from initial protonation at alcoholic OH^(-)groups to form carbenium ions (CBs),which engage in the subsequent esterification or oligomerization reactions to form OSAs/organosulfites (OSIs) or dimers.The kinetic results reveal that dehydration to form CBs for BOL and DOL reaction systems is the rate-limiting step.Subsequently,about 18%of CBs occur via oligomerization to dimers,which are difficult to further oligomerize because all reactive sites are occupied.The rate constant of BOL reaction system is one order of magnitude larger than that of DOL reaction system,implying that relative short-chain alcohols are more prone to contribute OSAs/OSIs than long-chain alcohols.Our results reveal that typical long-chain alcohols contribute SOA formation via esterification rather than oligomerization because OSA/OSI produced by esterification engages in nanoparticle growth through enhancing hygroscopicity.
基金the Basic Science Research Program(No.NRF-2019R1A2C4069764)by Convergent Technology R&D Program for Hum an Augm entation(No.2019M3C1B8077549)through the National Research Foundation of Korea(NRF)funded by Ministry of Science and ICT.
文摘The challenge for single-atom catalysts in various C-C cross coupling reaction exists in the development of solid supporting materials.It has been desired tofind a supporting material designed in molecular level to anchor a single-atom catalyst and provide high degree of dispersion and substrate access in aqueous media.Here,we prepared discrete cages of metal-organic polyhedra anchoring single Pd atom(MOP-BPY(Pd))and successfully performed a Suzuki-Miyaura cross coupling reaction with various substrates in aqueous media.It was revealed that each tetrahedral cage of MOP-BPY(Pd)has 4.5 Pd atoms on average and retained its high degree of dispersion up to 3 months in water.The coupling efficiencies of the Suzuki-Miyaura cross coupling reaction exhibited more than 90.0%for various substrates we have tested in the aqueous media,which is superior to those of the molecular Pd complex and metal-organic framework(MOF)anchoring Pd atoms.Moreover,MOP-BPY(Pd)was successfully recovered and recycled without performance degradation.
基金supported by the National Natural Science Foundation of China(Nos.91544224,21507010,41775150)the Ministry of Science&Technology of China(No.2012YQ220113-4)the Changjiang Scholars program of the Chinese Ministry of Education
文摘To investigate formation mechanisms of secondary organic carbon（SOC） in Eastern China,measurements were conducted in an urban site in Shanghai in the summer of 2015. A period of high O3 concentrations（daily peak 〉 120 ppb） was observed, during which daily maximum SOC concentrations exceeding 9.0 μg/（C·m^3）. Diurnal variations of SOC concentration and SOC/organic carbon（OC） ratio exhibited both daytime and nighttime peaks. The SOC concentrations correlated well with Ox（= O3＋ NO2） and relative humidity in the daytime and nighttime, respectively, suggesting that secondary organic aerosol formation in Shanghai is driven by both photochemical production and aqueous phase reactions. Single particle mass spectrometry was used to examine the formation pathways of SOC. Along with the daytime increase of SOC, the number fraction of elemental carbon（EC） particles coated with OC quickly increased from 38.1% to 61.9% in the size range of 250–2000 nm, which was likely due to gas-to-particle partitioning of photochemically generated semi-volatile organic compounds onto EC particles. In the nighttime, particles rich in OC components were highly hygroscopic, and number fraction of these particles correlated well with relative humidity and SOC/OC nocturnal peaks. Meanwhile, as an aqueous-phase SOC tracer, particles that contained oxalate-Fe（III） complex also peaked at night. These observations suggested that aqueous-phase processes had an important contribution to the SOC nighttime formation. The influence of aerosol acidity on SOC formation was studied by both bulk and single particle level measurements, suggesting that the aqueous-phase formation of SOC was enhanced by particle acidity.
基金supported by Basic Research Fund of CAMS(Chinese Academy of Meteorological Science)(2008Z011)National Natural Science Foundation of China(NSFC) under Grant Nos.40905060 and 41275168+1 种基金The National Basic Research Program of China(2006CB403701)Science and Technology Administration of China under Grant No.2006BAC12B00
文摘A field experiment was conducted in an intensive fog event between November 5 and November 8, 2009, in a heavily SO2-polluted area in North China Plain （NCP）, to measure SO2 and other air pollutants, liquid water content （LWC） of fog droplets, and other basic meteorological parameters. During the fog period, the concentrations of SO2 showed large variability, which was closely related to the LWC in the fog droplets. The averaged concentration of SO2 during non-fog periods was about 25 ppbv, while during the fog period, it rapidly reduced to about 4-7 ppbv. Such large reduction of SO2 suggested that a majority of SO2 （about 70%-80%） had reverted from gas to aqueous phase on account of the high solubility of SO2 in water in the fog droplets. However, the calculated gas to aqueous phase conversion was largely underestimated by merely using the Henry＇s Law constant of SO2, thus suggesting that aqueous reaction of SO2 in fog droplets might play some important role in enhancing the solubility of SO2. To simplify the phenomenon, an ＂effective solubility coefficient＂ is proposed in this study. This variability of SO2 measurement during the extensive fog event provides direct evidence of oxidation of SO2 in fog droplets, thus providing important implications for better understanding of the acidity in clouds, precipitation, and fogs in NCP, now a central environmental focus in China due to its rapid economic development.
