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...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.展开更多
The paper explores the evolution of thermal behavior of the material by studying the variations in thermal diffusivity using the single beam thermal lens(TL) technique. For this purpose, the decomposition of Cu(OH)_(2...The paper explores the evolution of thermal behavior of the material by studying the variations in thermal diffusivity using the single beam thermal lens(TL) technique. For this purpose, the decomposition of Cu(OH)_(2) into CuO is studied in a time range up to 120 h, by subjecting the sample to morphological, structural, and spectroscopic characterizations. The time evolution of thermal diffusivity can be divided into three regions for demonstrating the dynamics of the reaction. When the reaction is complete, the thermal diffusivity is also found to be saturated. In addition to the morphological modifications,from rods to flakes, the variations in the amount of hydroxyl group are attributed to be responsible for the enhancement of base fluid's thermal diffusivity by 165%. Thus the study unveils the role of hydroxyl groups in the thermal behavior of CuO.展开更多
Selective oxidation of glycerol provides a feasible route towards the sustainable synthesis of high value-added chemicals.Herein,the hydroxyapatite(HAP)supported palladium(Pd)species were fabricated by impregnation an...Selective oxidation of glycerol provides a feasible route towards the sustainable synthesis of high value-added chemicals.Herein,the hydroxyapatite(HAP)supported palladium(Pd)species were fabricated by impregnation and subsequent calcination.The as-obtained heterogeneous Pd catalyst afforded not only excellent selectivity to glyceric acid(GLA)up to 90%with 59%conversion of glycerol but also good recyclability by using molecular oxygen as an oxidant under mild conditions.The characterization of catalysts indicated that both the surface basicity and Pd sites on the catalyst played a crucial role in promoting glycerol oxidation.Notably,it demonstrated that the presence of the vicinal hydroxyl group of glycerol molecule can assist the oxidation reaction via forming a coordination between the vicinal hydroxyl group and Ca^(2+) sites on HAP-derived catalysts.In this catalytic process,the secondary hydroxyl of glycerol kept untouched and the primary hydroxyl of glycerol was converted into carboxyl group,while the Pd species acted as active centers for cooperatively promoting the subsequent oxidation to generate GLA.Additionally,this catalytic system can be extended widely for the oxidative conversion of other vicinal diols into the corresponding a-hydroxycarboxylic acids selectively.Isotope labeling experiment using H_(2)^(18)O confirmed that H_(2)O not only acted as solvent but also was involved in the catalytic cycles.On the basis of the results,a possible reaction mechanism has been proposed.The HAP-supported Pd catalytic system has been shown to serve as an effective approach for the upgrading of bio-derived vicinal diols to high value-added chemicals.展开更多
Compound 2 with 14β-hydroxyl group was successfully converted into its epimerized α-counterpart via oxidation - reduction.The elimination product (6) was auto-oxidized to epoxide 8,even in the solid
Many primary,secondary,tertiary alcohols,and phenolic hydroxyl groups were effectively converted to their corresponding trimethylsilyl ethers using hexamethyldisilazane in the presence of catalytic amounts of tribromo...Many primary,secondary,tertiary alcohols,and phenolic hydroxyl groups were effectively converted to their corresponding trimethylsilyl ethers using hexamethyldisilazane in the presence of catalytic amounts of tribromoisocyanuric acid and DABCO-bromine under mild conditions at room temperature with short reaction times in good to excellent yields.Excellent chemoselective silylation of hydroxyl groups in the presence of other functional groups were also observed.展开更多
We have investigated the stability, geometrical structure, electronic properties and vibrational spectra of different isomers of hydroxylate (5, 0) zigzag carbon nanotube (CNT) with 60 C atoms and 10 hydrogen (C60H10)...We have investigated the stability, geometrical structure, electronic properties and vibrational spectra of different isomers of hydroxylate (5, 0) zigzag carbon nanotube (CNT) with 60 C atoms and 10 hydrogen (C60H10) by using all-electron density-functional-theory (DFT) methods. Stable arrangements of these molecules were found by means of full geometry optimizations using B3LYP/6-31G(d) level of theory. From symmetrical point of view, four isomers of HO-C60H10 are possible when -OH bonds to the surface. We observed that the molecular properties strongly depend on the position of bonded hydroxyl group on the surface of CNT.展开更多
New electron donors with hydroxyl groups were synthesized and characterized spectroscopically. Their redox potentials were determined with cyclic voltammetry, and the comparison with BEDT-TTF [Bis(ethylenedithio)tetra...New electron donors with hydroxyl groups were synthesized and characterized spectroscopically. Their redox potentials were determined with cyclic voltammetry, and the comparison with BEDT-TTF [Bis(ethylenedithio)tetrathiafulvalene] in this aspect was made. These results indicated that the new electron donors had similar electron-donating capabilities as BEDT-TTF.展开更多
Trimethylchlorosilane was used as a stereoselective reagent to determine the e or aorientation of 3-hydroxyl group of some steroids by chemical ionization mass spectrometry.
The minerals of chevkinite group were commonly considered to be anhydrous minerals. The infrared absorption spectrum of natural nonmetamict chevkinite-(Ce) from the aegirine-alkali granite, Mianning, Sichuan Province,...The minerals of chevkinite group were commonly considered to be anhydrous minerals. The infrared absorption spectrum of natural nonmetamict chevkinite-(Ce) from the aegirine-alkali granite, Mianning, Sichuan Province, China, exhibited two broad peaks in the 3600–2800 cm–1 region owing to the OH stretching. The corresponding H2O content required for the charge balance in formula was 1.27%. The O-H ··· O bond lengths maight cover from 0.2658 to 0.2794 nm by the correlated OH stretching energies. An electrostatic charge bal- ance for chevkinite-(Ce) based on the assigned site-population from chemical data was calculated without the hydrogen contribution. The resulting empirical bond-valence sum on O6, O8, O2, O3, O5, and O4 ranged from 1.73 to 1.95 vu. The partial substitution of O by OH may occur in four atom sites: O6, O2, O4, and O5. The small differences in the bond-valence sums between the supposed donors and acceptors may mean a mixed donor/acceptor role of the involved oxygen atoms. The IR spectral features between 3394 and 3035 cm–1 consisted of various hydrous species at different structural sites and orientations. The OH groups in the chevkinite-(Ce) appeared to be involved in local charge imbalance in the structure and to be present when the mineral crystallized hydrothermally.展开更多
Quaternary phosphonium salts (QPS) with reactive groups used as antibacterial agents are promising which could be covalently linked to inert polymer surfaces by in situ polymerization. In this work, two kinds of quate...Quaternary phosphonium salts (QPS) with reactive groups used as antibacterial agents are promising which could be covalently linked to inert polymer surfaces by in situ polymerization. In this work, two kinds of quaternary phosphonium salts with hydroxyl groups were synthesized successfully. Characterization of these two quaternary phosphonium salts was performed by the Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance (NMR) spectrometry. The thermal stability and antibacterial activity of antibacterial agents were also investigated by using thermo-gravimetric analysis, differential scanning calorimetry (TG-DSC) and agar diffusion method. The test results showed that these two QPS exhibited good thermal stability and excellent antibacterial activity against both bacteria: Staphylococcus aureus and Escherichia coli.展开更多
The effect of exogenous hydroxyl,carboxyl groups and/or Sn^(2+) on pyrolysis reactions of poly(L-lactide)(PLLA)was investigated by thermogravimetric analysis(TGA).The activation energy(fa)of pyrolysis reactions was es...The effect of exogenous hydroxyl,carboxyl groups and/or Sn^(2+) on pyrolysis reactions of poly(L-lactide)(PLLA)was investigated by thermogravimetric analysis(TGA).The activation energy(fa)of pyrolysis reactions was estimated by the Kissinger-Akahira-Sunose method.The kinetic models were also explored by the Malek method,and the random degradation behavior was determined by comparing the plots of ln{-ln[1-(1-w)05]}versus 1/7for experimental data from TGA with model reactions.The pyrolysis reaction rate of PLLA was affected slightly by exogenous hydroxyl and carboxyl groups at lower levels of Sn with 65-70 mg·kg^(-1)but increased appreciably in the presence of extraneous Sn^(2+),-COOH/Sn^(2+),or-OH/Sn^(2+).The Ea values for the pyrolysis reactions of the PLLAs that provided lactide were different under the catalysis of Sn2+in different chemical environments because Sn^(2+) can form the new Sn-carboxylate and Sn-alkoxide with exogenous carboxyl and hydroxyl groups,which were different in steric hindrance for the formation of activated complex between Sn^(2+) and PLLA.Under the catalysis of Sn^(2+),a lactide molecule can be directly eliminated selectively at a random position of PLLA molecular chains,and the molecular chain of PLLA cannot change two PLLA fragments at the elimination site of lactide.However,it was regenerated into a new PLLA molecule with the molecular weight reduced by 144 g·mol^(-1).展开更多
Rare earth(Y, La and Nd) doped TiO2 thin films were prepared on glass slides by sol-gel method. The photocatalytic decomposition of methylene blue in aqueous solution was used as a probe reaction to evaluate their pho...Rare earth(Y, La and Nd) doped TiO2 thin films were prepared on glass slides by sol-gel method. The photocatalytic decomposition of methylene blue in aqueous solution was used as a probe reaction to evaluate their photocatalytic activities. The effects of hydroxyl groups on hydrophilic and photocatalytic activities were investigated by means of techniques such as X-ray diffraction(XRD), atomic force microscopy(AFM), Fourier transform infrared(FTIR), optical contact angle, UV-Visible spectroscopy and VIS spectroscopy. The results showed that an appropriate doping of rare earth could cause the TiO2 lattice distortion, inhibited phase transition from anatase to rutile, accelerated surface hydroxylation and produced more hydroxyl groups, which resulted in a denser surface and smaller grains(40–60 nm), and a significant improvement in the hydrophilicity and photoreactivity of TiO2 thin films. The optimal content of rare earth was between 0.1 wt.% and 0.3 wt.%. Moreover, the modification mechanism of rare earth doping was also discussed.展开更多
An important field in carbohydrate chemistry is to look for regioselective re-actions of saccharides to simplify the chemical synthesis of oligosaccharides. Oneof such efforts nowadays is directed to the convenient pr...An important field in carbohydrate chemistry is to look for regioselective re-actions of saccharides to simplify the chemical synthesis of oligosaccharides. Oneof such efforts nowadays is directed to the convenient preparation of protected D-展开更多
基金supported by the National Natural Science Foundation of China(22172090,21790051)the National Key Research and Development Project of China(2022YFA1204500,2022YFA1204501)+2 种基金the Natural Science Foundation of Shan-dong Province(ZR2021MB015)the Open Funds of the State Key Laboratory of Electroanalytical Chemistry(SKLEAC202202)the Young Scholars Program of Shandong University。
文摘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.
文摘The paper explores the evolution of thermal behavior of the material by studying the variations in thermal diffusivity using the single beam thermal lens(TL) technique. For this purpose, the decomposition of Cu(OH)_(2) into CuO is studied in a time range up to 120 h, by subjecting the sample to morphological, structural, and spectroscopic characterizations. The time evolution of thermal diffusivity can be divided into three regions for demonstrating the dynamics of the reaction. When the reaction is complete, the thermal diffusivity is also found to be saturated. In addition to the morphological modifications,from rods to flakes, the variations in the amount of hydroxyl group are attributed to be responsible for the enhancement of base fluid's thermal diffusivity by 165%. Thus the study unveils the role of hydroxyl groups in the thermal behavior of CuO.
基金support from the National Natural Science Foundation of China(21773061,21978095)Innovation Program of Shanghai Municipal Education Commission(15ZZ031)the Fundamental Research Funds for the Central Universities。
文摘Selective oxidation of glycerol provides a feasible route towards the sustainable synthesis of high value-added chemicals.Herein,the hydroxyapatite(HAP)supported palladium(Pd)species were fabricated by impregnation and subsequent calcination.The as-obtained heterogeneous Pd catalyst afforded not only excellent selectivity to glyceric acid(GLA)up to 90%with 59%conversion of glycerol but also good recyclability by using molecular oxygen as an oxidant under mild conditions.The characterization of catalysts indicated that both the surface basicity and Pd sites on the catalyst played a crucial role in promoting glycerol oxidation.Notably,it demonstrated that the presence of the vicinal hydroxyl group of glycerol molecule can assist the oxidation reaction via forming a coordination between the vicinal hydroxyl group and Ca^(2+) sites on HAP-derived catalysts.In this catalytic process,the secondary hydroxyl of glycerol kept untouched and the primary hydroxyl of glycerol was converted into carboxyl group,while the Pd species acted as active centers for cooperatively promoting the subsequent oxidation to generate GLA.Additionally,this catalytic system can be extended widely for the oxidative conversion of other vicinal diols into the corresponding a-hydroxycarboxylic acids selectively.Isotope labeling experiment using H_(2)^(18)O confirmed that H_(2)O not only acted as solvent but also was involved in the catalytic cycles.On the basis of the results,a possible reaction mechanism has been proposed.The HAP-supported Pd catalytic system has been shown to serve as an effective approach for the upgrading of bio-derived vicinal diols to high value-added chemicals.
文摘Compound 2 with 14β-hydroxyl group was successfully converted into its epimerized α-counterpart via oxidation - reduction.The elimination product (6) was auto-oxidized to epoxide 8,even in the solid
基金Supported by Bu-Ali Sina University Research Council.
文摘Many primary,secondary,tertiary alcohols,and phenolic hydroxyl groups were effectively converted to their corresponding trimethylsilyl ethers using hexamethyldisilazane in the presence of catalytic amounts of tribromoisocyanuric acid and DABCO-bromine under mild conditions at room temperature with short reaction times in good to excellent yields.Excellent chemoselective silylation of hydroxyl groups in the presence of other functional groups were also observed.
文摘We have investigated the stability, geometrical structure, electronic properties and vibrational spectra of different isomers of hydroxylate (5, 0) zigzag carbon nanotube (CNT) with 60 C atoms and 10 hydrogen (C60H10) by using all-electron density-functional-theory (DFT) methods. Stable arrangements of these molecules were found by means of full geometry optimizations using B3LYP/6-31G(d) level of theory. From symmetrical point of view, four isomers of HO-C60H10 are possible when -OH bonds to the surface. We observed that the molecular properties strongly depend on the position of bonded hydroxyl group on the surface of CNT.
基金the Chinese Academy of Sciences(KJ951-A1-501-03)
文摘New electron donors with hydroxyl groups were synthesized and characterized spectroscopically. Their redox potentials were determined with cyclic voltammetry, and the comparison with BEDT-TTF [Bis(ethylenedithio)tetrathiafulvalene] in this aspect was made. These results indicated that the new electron donors had similar electron-donating capabilities as BEDT-TTF.
文摘Trimethylchlorosilane was used as a stereoselective reagent to determine the e or aorientation of 3-hydroxyl group of some steroids by chemical ionization mass spectrometry.
基金the National Natural Science Foundation of China (40572029)
文摘The minerals of chevkinite group were commonly considered to be anhydrous minerals. The infrared absorption spectrum of natural nonmetamict chevkinite-(Ce) from the aegirine-alkali granite, Mianning, Sichuan Province, China, exhibited two broad peaks in the 3600–2800 cm–1 region owing to the OH stretching. The corresponding H2O content required for the charge balance in formula was 1.27%. The O-H ··· O bond lengths maight cover from 0.2658 to 0.2794 nm by the correlated OH stretching energies. An electrostatic charge bal- ance for chevkinite-(Ce) based on the assigned site-population from chemical data was calculated without the hydrogen contribution. The resulting empirical bond-valence sum on O6, O8, O2, O3, O5, and O4 ranged from 1.73 to 1.95 vu. The partial substitution of O by OH may occur in four atom sites: O6, O2, O4, and O5. The small differences in the bond-valence sums between the supposed donors and acceptors may mean a mixed donor/acceptor role of the involved oxygen atoms. The IR spectral features between 3394 and 3035 cm–1 consisted of various hydrous species at different structural sites and orientations. The OH groups in the chevkinite-(Ce) appeared to be involved in local charge imbalance in the structure and to be present when the mineral crystallized hydrothermally.
文摘Quaternary phosphonium salts (QPS) with reactive groups used as antibacterial agents are promising which could be covalently linked to inert polymer surfaces by in situ polymerization. In this work, two kinds of quaternary phosphonium salts with hydroxyl groups were synthesized successfully. Characterization of these two quaternary phosphonium salts was performed by the Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance (NMR) spectrometry. The thermal stability and antibacterial activity of antibacterial agents were also investigated by using thermo-gravimetric analysis, differential scanning calorimetry (TG-DSC) and agar diffusion method. The test results showed that these two QPS exhibited good thermal stability and excellent antibacterial activity against both bacteria: Staphylococcus aureus and Escherichia coli.
基金the National Key Research and Development Program of China(No.2016YFB0302500)the National Natural Science Foundation of China(Nos.51873209,51873210,51773194 and 51973219)Jilin Scientific and Technological Development Program,China(No.20200403022SF).
文摘The effect of exogenous hydroxyl,carboxyl groups and/or Sn^(2+) on pyrolysis reactions of poly(L-lactide)(PLLA)was investigated by thermogravimetric analysis(TGA).The activation energy(fa)of pyrolysis reactions was estimated by the Kissinger-Akahira-Sunose method.The kinetic models were also explored by the Malek method,and the random degradation behavior was determined by comparing the plots of ln{-ln[1-(1-w)05]}versus 1/7for experimental data from TGA with model reactions.The pyrolysis reaction rate of PLLA was affected slightly by exogenous hydroxyl and carboxyl groups at lower levels of Sn with 65-70 mg·kg^(-1)but increased appreciably in the presence of extraneous Sn^(2+),-COOH/Sn^(2+),or-OH/Sn^(2+).The Ea values for the pyrolysis reactions of the PLLAs that provided lactide were different under the catalysis of Sn2+in different chemical environments because Sn^(2+) can form the new Sn-carboxylate and Sn-alkoxide with exogenous carboxyl and hydroxyl groups,which were different in steric hindrance for the formation of activated complex between Sn^(2+) and PLLA.Under the catalysis of Sn^(2+),a lactide molecule can be directly eliminated selectively at a random position of PLLA molecular chains,and the molecular chain of PLLA cannot change two PLLA fragments at the elimination site of lactide.However,it was regenerated into a new PLLA molecule with the molecular weight reduced by 144 g·mol^(-1).
基金Project supported by the National Natural Science Foundation of China(51162022,21201098)Jiangxi Provincial Education Department(GJJ14126)
文摘Rare earth(Y, La and Nd) doped TiO2 thin films were prepared on glass slides by sol-gel method. The photocatalytic decomposition of methylene blue in aqueous solution was used as a probe reaction to evaluate their photocatalytic activities. The effects of hydroxyl groups on hydrophilic and photocatalytic activities were investigated by means of techniques such as X-ray diffraction(XRD), atomic force microscopy(AFM), Fourier transform infrared(FTIR), optical contact angle, UV-Visible spectroscopy and VIS spectroscopy. The results showed that an appropriate doping of rare earth could cause the TiO2 lattice distortion, inhibited phase transition from anatase to rutile, accelerated surface hydroxylation and produced more hydroxyl groups, which resulted in a denser surface and smaller grains(40–60 nm), and a significant improvement in the hydrophilicity and photoreactivity of TiO2 thin films. The optimal content of rare earth was between 0.1 wt.% and 0.3 wt.%. Moreover, the modification mechanism of rare earth doping was also discussed.
基金Project supported by the State Science and Technology Commission of China.
文摘An important field in carbohydrate chemistry is to look for regioselective re-actions of saccharides to simplify the chemical synthesis of oligosaccharides. Oneof such efforts nowadays is directed to the convenient preparation of protected D-
