Co-reporter:Faliang Li, Yingnan Cao, Jianghao Liu, Haijun Zhang, Shaowei Zhang
Ceramics International 2017 Volume 43, Issue 10(Volume 43, Issue 10) pp:
Publication Date(Web):1 July 2017
DOI:10.1016/j.ceramint.2017.03.080
ZrB2 and ZrB2-SiC powders were prepared by a combined sol-gel and boro/carbothermal reduction method, and their oxidation kinetics was studied by using a non-isothermal thermogravimetric technique. The results showed that the Mample power law (n=1) was the most probable mechanism function, and the incorporation of SiC into ZrB2 greatly enhance the latter's oxidation resistance. The oxidation activation energy values of phase pure ZrB2 and ZrB2-SiC powders were respectively 249 and 308 kJ/mol.
Co-reporter:Zhong Huang;Shaowei Zhang
CrystEngComm (1999-Present) 2017 vol. 19(Issue 22) pp:2971-2976
Publication Date(Web):2017/06/07
DOI:10.1039/C7CE00549K
Lanthanum oxychloride (LaOCl) microplates were synthesized via the chloride salt-assisted method using lanthanum oxide, potassium chloride and lithium chloride as the raw materials. The effects of salt type and reaction temperature on the synthesis of LaOCl were investigated in detail. The lowest synthesis temperature in the present study was 300 °C, which was much lower than that required by other methods. The thickness and width of the as-prepared LaOCl microplates were about 200–500 nm and several microns, respectively. With potassium chloride and lithium chloride as the reaction medium, the latter acted not only as the molten salt but also as the reactant in the LaOCl synthesis. The chloride salt not only significantly lowers the synthesis temperature, but also provides the good conditions for the LaOCl growth of plate-like structures.
Co-reporter:Lei Han, Faliang Li, Xiangong Deng, Junkai Wang, ... Shaowei Zhang
Journal of the European Ceramic Society 2017 Volume 37, Issue 7(Volume 37, Issue 7) pp:
Publication Date(Web):1 July 2017
DOI:10.1016/j.jeurceramsoc.2017.02.032
Hierarchically pore-structured porous diatomite ceramics containing 82.9∼84.5% porosity were successfully prepared for the first time via foam-gelcasting using diatomite powder as the main raw material. Sizes of mesopores derived from the raw material and macropores formed mainly from foaming were 0.02∼0.1 μm and 109.7∼130.5 μm, respectively. The effect of sintering temperature, additive content and solid loading of slurry on pore size and distribution, and mechanical and thermal properties of as-prepared porous ceramics were investigated. Compressive strength of as-prepared porous ceramics increased with sintering temperature, and the one containing 82.9% porosity showed the highest compressive strength of 2.1 ± 0.14 MPa. In addition, the one containing 84.5% porosity and having compressive strength of 1.1 ± 0.07 MPa showed the lowest thermal conductivity of 0.097 ± 0.001 W/(m·K) at a test temperature of 200 ̊C, suggesting that as-prepared porous ceramics could be potentially used as good thermal insulation materials.Download high-res image (182KB)Download full-size image
Co-reporter:Saisai Li, Feng Liang, Junkai Wang, Haijun Zhang, Shaowei Zhang
Advanced Powder Technology 2017 Volume 28, Issue 10(Volume 28, Issue 10) pp:
Publication Date(Web):1 October 2017
DOI:10.1016/j.apt.2017.07.017
•pH value showed an evident effect on the morphology of carbonaceous spheres (CS).•CS could be obtained when the pH value of starting solution is less than 12.•Lumpy aggregation of CS were formed when pH value was 13–14.•The CS prepared under pH 6, 9 showed good adsorption capacity for MB.Mono-dispersed carbonaceous spheres (CS) with a narrow size distribution were synthesized via hydrothermal treatment of glucose. The effects of hydrothermal temperature and time, glucose concentration and pH value of solution were investigated in detail. Structures and surface properties of as-prepared products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Induced coupled plasma emission spectroscopy (ICP), thermogravimetric analysis/differential scanning calorimetry (TG/DSC), Nitrogen adsorption/desorption and Fourier transformed infrared spectroscopy (FTIR). The results showed that the production yield of CS increased from 2.1 to 32% with increasing the temperature from 160 to 180 °C, and the average size increased from 0.23 to 0.95 μm with extending the hydrothermal time from 8 to 16 h. pH value of the starting solution showed an evident effect on the morphology of CS via affecting the decomposition products of glucose. CS could be obtained when the pH value of starting solution was less than 12, but further increasing the pH value to 13–14 led to the formation of lumpy aggregations of carbon rather than spherical CS. The CS prepared under pH 6 and 9 showed good adsorption capacity for Methylene blue (MB), which was attributed to their relatively high specific surface area.CS with size of about 1.0 μm were synthesized via a hydrothermal process using glucose as a starting material. The solution pH value showed an evident effect on the morphology of CS. Spherical CS could be obtained at pH value of solution less than 12, otherwise, lumpy aggregations of carbon rather than spherical CS were formed. In addition, CS prepared at pH 6 and 9 showed good adsorption capacity for Methylene blue (MB).Download high-res image (54KB)Download full-size image
Co-reporter:Junkai Wang, Yuanzhuo Zhang, Junyi Li, Haijun Zhang, Shupeng Song, Shaowei Zhang
Powder Technology 2017 Volume 317(Volume 317) pp:
Publication Date(Web):15 July 2017
DOI:10.1016/j.powtec.2017.05.004
•β-SiC was synthesized by a microwave reaction method using cobalt as catalyst.•The synthesis temperature was 100 °C lower than that conventional heating route.•β-SiC particulates, along with some whisker-shaped β-SiC were formed.•DFT calculation was used to study the catalytic mechanism of cobalt.•The Co/Si alloy played an important role in the SiSi bond breaking.β-SiC was synthesized by a microwave reaction method in Ar, using silicon powder and phenolic resin as raw materials, and cobalt nitrate as a catalyst precursor. The effects of temperature, time, and catalyst content on the formation of SiC were investigated. When 1.0–2.0 wt% Co was used as a catalyst, phase pure β-SiC was formed after 30 min at 1150 °C. This synthesis temperature was 100 °C lower than that required by the conventional heating route catalyzed by with the identical amounts of catalyst. When a catalyst was absent, the synthesis temperature of β-SiC was as high as 1250 °C even in the case of using microwave heating. β-SiC particulates were formed, along with some whisker-shaped β-SiC of 30–100 nm in diameter and up to 20 μm in length. Density Functional Theory (DFT) calculations suggest that under the test conditions the formation of Co/Si alloy was energetically favorable, and played an important role in the SiSi bond breaking and the subsequent SiC formation.Download high-res image (242KB)Download full-size image
Co-reporter:Xiangong Deng, Songlin Ran, Lei Han, Haijun Zhang, ... Shaowei Zhang
Journal of the European Ceramic Society 2017 Volume 37, Issue 13(Volume 37, Issue 13) pp:
Publication Date(Web):1 October 2017
DOI:10.1016/j.jeurceramsoc.2017.05.009
High-strength self-reinforced porous mullite ceramics were prepared via foam-gelcasting using mullite powder as a main raw material, AlF3·3H2O (0–8 wt%) as an additive, Isobam-104 as a dispersing and gelling agent, sodium carboxymethyl cellulose as a foam stabilizing agent, and triethanolamine lauryl sulfate as a foaming agent. The effects of AlF3·3H2O content on rheological and gelling behaviors of the slurries, and porosity and mechanical properties of self-reinforced porous mullite samples were examined. Addition of AlF3·3H2O promoted the in-situ formation of elongated mullite in the fired porous samples, which improved considerably their mechanical properties. Compressive strength and flexural strength of 67.0% porous mullite ceramics prepared with addition of 6 wt% AlF3·3H2O was as high as 41.3 and 13.9 MPa, respectively. Its hot modulus rupture (HMOR) increased initially with the testing temperature, and peaked (with a maximum value of 16.6 MPa) at 800 °C above which it started to decrease with the testing temperature. Nevertheless, it was still retained as high as 6.7 and 2.8 MPa at 1200 and 1400 °C, respectively.
Co-reporter:Junkai Wang, Xiangong Deng, Haijun Zhang, Yuanzhuo Zhang, Hongjuan Duan, Lilin Lu, Jianbo Song, Liang Tian, Shupeng Song, Shaowei Zhang
Physica E: Low-dimensional Systems and Nanostructures 2017 Volume 86() pp:24-35
Publication Date(Web):February 2017
DOI:10.1016/j.physe.2016.09.016
Carbon nanotubes (CNTs) with 40–100 nm in diameter and tens of micrometers in length were prepared via catalytic pyrolysis of phenol resin in Ar at 673–1273 K using ferric nitrate as a catalyst precursor. Structure and morphology of pyrolyzed resin were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. Ferric nitrate was transformed to Fe3O4 at 673 K, and to metallic Fe and FexC carbide at 873–1273 K. The optimal weight ratio of Fe catalyst to phenol resin for growing CNTs was 1.00 wt%, and the optimal temperature was 1073 K. In addition, use of a high pressure increased the yield of CNTs. Density functional theory (DFT) calculations suggest that Fe catalysts facilitate the CNTs growth by increasing the bond length and weakening the bond strength in C2H4 via donating electrons to the C atoms in it.
Co-reporter:Zhong Huang, Faliang Li, Chengpeng Jiao, Jianghao Liu, Juntong Huang, Lilin Lu, Haijun Zhang, Shaowei Zhang
Ceramics International 2016 Volume 42(Issue 5) pp:6221-6227
Publication Date(Web):April 2016
DOI:10.1016/j.ceramint.2016.01.004
Ultrafine powders of pyrochlore-type La2Zr2O7 were synthesized via a simple molten salt mediated process using zirconium oxide and lanthanum oxide as raw materials, and sodium chloride, potassium chloride and sodium fluoride to form a reaction medium. The effects of reaction temperature, salt/reactant ratio and salt type on the La2Zr2O7 formation were investigated. Among the three attempted salt assemblies (KCl–LiCl, Na2CO3–K2CO3, and NaCl–KCl–NaF), NaCl–KCl–NaF showed the best accelerating effect on the La2Zr2O7 formation. At a given temperature, the La2Zr2O7 content in the final products increased with the increase in the salt amount. Phase pure submicron sized La2Zr2O7 ultrafine powders were obtained after 3 h firing at 1100 °C with the salt/reactant weight ratio of 5:1 or at 1200 °C with salt/reactant weight ratio of 3:1. The synthesis temperature (1100 °C) was much lower than that required by the conventional solid-state mixing method or a wet chemical method. The “dissolution–precipitation” mechanism had dominated the synthesis process.
Co-reporter:Lilin Lu, Shaowei Zhang, Haijun Zhang, Faliang Li, Feng Liang, Yanjun Li
Ceramics International 2016 Volume 42(Issue 10) pp:11924-11929
Publication Date(Web):1 August 2016
DOI:10.1016/j.ceramint.2016.04.117
Abstract
The incorporation of Fe and Cr atoms into β-Si5AlON7 and the effects on the mechanical properties of β-Si5AlON7 were theoretically studied at the GGA-PBE/USP level of theory. The incorporation of Fe and Cr atoms shows remarkable site preferences in β-Si5AlON7. The binding energies between the incorporated Fe/Cr atoms and the parent β-Si5AlON7 are ~5.0 eV, indicating both Fe@β-Si5AlON7 and Cr@β-Si5AlON7 are thermodynamically stable. Fe incorporation at the A, B and G sites induces remarkable increase in the shear modulus and Young's modulus; all other Fe/Cr incorporated β-Si5AlON7 structures exhibit lowered shear modulus and Young's modulus than the parent β-Si5AlON7. Except CrG@β-Si5AlON7, the Poisson's ratio of β-Si5AlON7 decreases in all cases of Fe and Cr incorporation.
Co-reporter:Xiangong Deng, Junkai Wang, Jianghao Liu, Haijun Zhang, Lei Han, Shaowei Zhang
Ceramics International 2016 Volume 42(Issue 16) pp:18215-18222
Publication Date(Web):December 2016
DOI:10.1016/j.ceramint.2016.08.145
Abstract
Porous MgAl2O4 ceramics were prepared via a low cost foam-gelcasting route using MgAl2O4 powders as the main raw material, ammonium polyacrylate as a dispersant, a small amount of modified carboxymethyl cellulose as a gelling agent, and TH-IV polymer as a foaming agent. The effects of additive's content, solid loading and gelling temperature on slurry's rheological behavior were investigated, and microstructures and properties of as-prepared porous MgAl2O4 ceramics examined. Based on the results, the roles played by the foaming agent in the cases of porosity, pore structure, pore size, mechanical properties and thermal conductivity were clarified. Porosity and pore sizes of as-prepared porous MgAl2O4 ceramics increased with increasing the foaming agent from 0.05 to 0.6 vol%. Porous MgAl2O4 ceramics with porosity of 75.1% and average pore size of 266 µm exhibited a compressive strength as high as 12.5±0.8 MPa and thermal conductivity as low as 0.24 W/(m K) (at 473 K).
Co-reporter:Zhong Huang, Jianghao Liu, Xiangong Deng, Haijun Zhang, Lilin Lu, Zheng Hou, Shaowei Zhang
International Journal of Refractory Metals and Hard Materials 2016 Volume 54() pp:315-321
Publication Date(Web):January 2016
DOI:10.1016/j.ijrmhm.2015.08.011
•Phase pure Mo NPs were synthesized at as low as 650 °C by molten salt synthesis.•The formation temperature was at least 150 °C lower than that by other methods.•Mo NPs exhibited a narrow size distribution between 30 and 120 nm.•Mo dendritic rods were found for the first time.Pure molybdenum (Mo) nanoparticles (NPs) were synthesized by a novel molten salt technique using Na2MoO4 and Al as starting materials and NaCl, KCl and NaF to form a reaction medium. The effects of salt type, reaction temperature and salt to reactant ratio on the synthesis of Mo NPs were investigated in detail. Phase pure Mo NPs with a crystalline size of about 46 nm were synthesized at as low as 650 °C which was much lower than that required by other conventional reduction methods. Among the salts tested, the NaClKClNaF ternary salt showed the best accelerating effect on the low temperature Mo NPs formation, and the optimal weight ratio of salt to reactant was 1.0:1.0. The “dissolution-precipitation mechanism” played a dominant role in the molten salt synthesis of Mo NPs.Mo nanoparticles (NPs) with a grain size of 46 nm are prepared at 650 °C for 2 h by molten salt synthesis and for the first time, the temperature was at least 150 °C lower than that required by conventional hydrogen or carbothermal reduction method.
Co-reporter:Haijun Zhang;Lilin Lu;Keisuke Kawashima;Mitsutaka Okumura;Masatake Haruta;Naoki Toshima
Advanced Materials 2015 Volume 27( Issue 8) pp:1383-1388
Publication Date(Web):
DOI:10.1002/adma.201404870
Co-reporter:Chengpeng Jiao, Zili Huang, Xiaofeng Wang, Haijun Zhang, Lilin Lu and Shaowei Zhang
RSC Advances 2015 vol. 5(Issue 43) pp:34364-34371
Publication Date(Web):08 Apr 2015
DOI:10.1039/C5RA01892G
A series of poly (N-vinyl-2-pyrrolidone) stabilized colloidal Ni/Au/Co trimetallic nanoparticles (TNPs) were synthesized by co-reduction of their corresponding metal precursors via dropwise addition of NaBH4. Ultraviolet-visible spectrophotometry (UV-Vis), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), powder X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HR-TEM) combined with energy dispersive spectrometry (EDS) were used to characterize the morphology, crystalline structure and electron distribution of the as-prepared TNPs. The effects of metal composition on the size distribution and hydrogen generation from catalytic hydrolysis of alkaline NaBH4 aqueous solutions were also investigated. The results indicated that the as-prepared alloy-structured Ni45Au45Co10 TNPs showed a maximum catalytic activity of 1170 mol-H2 per h per mol-M, which is several times higher than that of the as-prepared Au, Ni or Co monometallic nanoparticles (MNPs), or Au50Ni50, Au50Co50 or Ni50Co50 bimetallic nanoparticles (BNPs). The enhanced catalytic activity of the TNPs compared with the MNPs and BNPs could be attributed to the presence of electron charge transfer effects among Au, Ni and Co atoms, which is supported by the results of X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculation. The apparent activation energy of the as-prepared Au45Ni45Co10 TNPs in hydrolysis of NaBH4 aqueous solution was determined as 18.8 kJ mol−1.
Co-reporter:Lilin Lu, Shufang Zhu, Haijun Zhang, Faliang Li and Shaowei Zhang
RSC Advances 2015 vol. 5(Issue 19) pp:14114-14122
Publication Date(Web):22 Jan 2015
DOI:10.1039/C4RA14737E
Resveratrol is an outstanding natural antioxidant which is often found in a wide variety of plant species; its antioxidative activity has been recently reported as being influenced by complexation with macromolecules such as cyclodextrins (CDs). In this work, the complexation of resveratrol with CDs and cucurbiturils (CBs) has been studied by density functional theory calculations, the equilibrium geometries and the electronic structures of the complexes are investigated at the B3LYP/6-311G(d, p) level of theory, the antioxidative capabilities of the inclusion complexes have been elucidated based on H-atom transfer (HAT), sequential proton loss electron transfer (SPLET) and single electron transfer (SET) antioxidative mechanisms. The influence of inclusion complexation on the structure and antioxidative activity of resveratrol has been investigated. Our results show that resveratrol exhibits a non-planar geometry when it is included in CDs and CBs. Complexation of resveratrol with these two macromolecules results in negligible change in frontier orbital distribution, but distinct change in orbital energies. Different inclusion complexes and inclusion modes show different influences on 4′-OH bond dissociation enthalpy (4′-OH BDE), proton affinity (PA) and the electron transfer enthalpy (ETE) of the 4′-phenolate anion, and the ionization potential (IP) of resveratrol. Compared to cyclodextrins, cucurbiturils exhibit better performance in improving the antioxidative capacity of resveratrol.
Co-reporter:Xiangong Deng, Shuang Du, Haijun Zhang, Faliang Li, Junkai Wang, Wanguo Zhao, Feng Liang, Zhong Huang, Shaowei Zhang
Ceramics International 2015 Volume 41(Issue 10) pp:14419-14426
Publication Date(Web):December 2015
DOI:10.1016/j.ceramint.2015.07.077
ZrB2–SiC composite powders were successfully synthesized via microwave-assisted boro/carbothermal reduction technique using zircon (ZrSiO4), activated carbon (C) and boron oxide (B2O3) as raw materials. They were characterized by using X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), energy-dispersive spectroscopy (EDS) and transmission electron microscopy (TEM). Thermodynamic analysis on the synthesis process was carried out, and the effects of SiC bedding powder, reaction temperature, soaking time and n(B2O3):n(ZrSiO4) molar ratio on the formation of ZrB2–SiC composite powders were examined. The results showed that phase pure ZrB2–SiC composite powders were successfully synthesized at 1573 K which was 200 K lower than that required by using the conventional boro/carbothermal reduction method. In the final composite powders, fibrous SiC phases with 0.1–0.5 μm in diameter and 1.4–4.2 μm in length were homogeneously distributed among spherical ZrB2 particles with the average size of 0.1–1 μm.
Co-reporter:Xiangong Deng, Junkai Wang, Jianghao Liu, Haijun Zhang, Faliang Li, Hongjuan Duan, Lilin Lu, Zhong Huang, Wanguo Zhao, Shaowei Zhang
Ceramics International 2015 Volume 41(Issue 7) pp:9009-9017
Publication Date(Web):August 2015
DOI:10.1016/j.ceramint.2015.03.237
Porous mullite ceramics were prepared via foam-gelcasting using industrial grade mullite powder as the main raw materials, Isobam-104 as the dispersing and gelling agent, sodium carboxymethyl cellulose as the foam stabilizing agent, and triethanolamine lauryl sulfate as the foaming agent. The effects of processing parameters such as type and amount of additive, solid loading level and gelling temperature on rheological properties and gelling behaviors of the slurries were investigated. The green samples after drying at 100 °C for 24 h were fired at 1600 °C for 2 h, and the microstructures and properties of the resultant porous ceramic samples were characterized. Based on the results, the effects of foaming agent on the porosity level, pore structure and size and mechanical properties of the as-prepared porous mullite ceramics were examined. Porosity levels and pore sizes of the as-prepared samples increased with increasing the foaming agent content up to 1.0%, above which both porosity levels and pore sizes did not change. The compressive strength and flexural strength of the as-prepared sample with porosity of 76% and average pore size of 313 μm remained as high as 15.3±0.3 MPa and 3.7±0.2 MPa, respectively, and permeability increased exponentially with increasing the porosity.
Co-reporter:Faliang Li, Fang Fu, Lilin Lu, Haijun Zhang, Shaowei Zhang
Advanced Powder Technology 2015 Volume 26(Issue 5) pp:1417-1422
Publication Date(Web):September 2015
DOI:10.1016/j.apt.2015.07.018
Highlights
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β-Sialon powders were synthesized by sol–gel and microwave carbothermal reduction.
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The formation temperature is as low as 1250 °C.
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Ultrafine β-Sialon powders were granular with primary size of 69 nm.
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The relative content of β-Sialon was predicted by BP ANNs.
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The values calculated by the ANNs matched well with the experimental ones.
Co-reporter:Lilin Lu;Shaowei Zhang;Faliang Li
Angewandte Chemie International Edition 2015 Volume 54( Issue 32) pp:9328-9332
Publication Date(Web):
DOI:10.1002/anie.201500942
Abstract
Development of highly active, low cost, ecologically friendly, and durable homogenous catalysts for hydrogen generation from hydrolysis of borohydride is one of the most desirable pathways for future hydrogen utilization. The unexpected catalytic activities of inorganic ammonium species and the corresponding mechanisms underpinning them are studied. The catalytic activities of the ammonium species are higher than or comparable to those of mostly investigated noble-metal/transition-metal catalysts (such as Pd, Pt, Ni, and Co) but are considerably cheaper, more environmentally friendly, and more readily available. Quantum chemical calculations indicate that the unique ammonium-induced reaction pathway involved with a barrierless elementary reaction at the reaction entrance and the formation of the highly active intermediate BH3 are responsible for the unexpected catalytic activities and the significantly accelerated hydrogen generation.
Co-reporter:Lilin Lu;Shaowei Zhang;Faliang Li
Angewandte Chemie 2015 Volume 127( Issue 32) pp:9460-9464
Publication Date(Web):
DOI:10.1002/ange.201500942
Abstract
Development of highly active, low cost, ecologically friendly, and durable homogenous catalysts for hydrogen generation from hydrolysis of borohydride is one of the most desirable pathways for future hydrogen utilization. The unexpected catalytic activities of inorganic ammonium species and the corresponding mechanisms underpinning them are studied. The catalytic activities of the ammonium species are higher than or comparable to those of mostly investigated noble-metal/transition-metal catalysts (such as Pd, Pt, Ni, and Co) but are considerably cheaper, more environmentally friendly, and more readily available. Quantum chemical calculations indicate that the unique ammonium-induced reaction pathway involved with a barrierless elementary reaction at the reaction entrance and the formation of the highly active intermediate BH3 are responsible for the unexpected catalytic activities and the significantly accelerated hydrogen generation.
Co-reporter:Lilin Lu, Min Qiang, Faliang Li, Haijun Zhang, Shaowei Zhang
Dyes and Pigments 2014 Volume 103() pp:175-182
Publication Date(Web):April 2014
DOI:10.1016/j.dyepig.2013.12.015
•Anthocyanidins.•Antioxidative activities.•DFT theoretical study.•Structure–activity relationship.Anthocyanidins are an important class of plant pigment, in the present work the antioxidative properties of anthocyanidins have been explored by density functional theory calculations, three main antioxidative mechanisms, which include H atom transfer (HAT), single electron transfer (SET) and sequential proton loss electron transfer (SPLET), have been investigated at B3LYP/6-311G(d,p) level of theory. The O–H bond dissociation enthalpies (BDEs), ionization potentials (IPs), electron affinities (EAs), proton affinities (PAs) and electron transfer enthalpies (ETEs) are investigated in gas phase and aqueous solution. Results show 3-OH and 4′-OH posses lower BDE as compared to other OH groups, the substituents in B-ring influence 4′-OH BDE, but exhibit negligible influence on other OH BDEs. Among all investigated anthocyanidins, pelargonidin has the highest IP and EA in gas phase, substituent in ortho position of 4′-OH leads to remarkable decrease in IP and EA. OH substituent in B-ring almost show no influence on PAs and ETEs of 3-, 5-, and 7-phenolate anions, but OCH3 substituent influence them significantly. For PAs and ETEs of 4′-phenolate anion, two types of substituents both exhibit remarkable influence. Base on the simplest anthocyanidins, pelargonidin, molecular simplification has been performed to explore the necessary pharmacophores responsible for the antioxidative activity of anthocyanidins.
Co-reporter:Haijun Zhang, Naoki Toshima, Kanako Takasaki, Mitsutaka Okumura
Journal of Alloys and Compounds 2014 Volume 586() pp:462-468
Publication Date(Web):15 February 2014
DOI:10.1016/j.jallcom.2013.10.048
•Agcore/Aushell BNPs with size of less than 2.0 nm were prepared.•No any reducing reagents and lights were used for the preparation of the BNPs.•The catalytic activity of the BNPs is about two times higher than that of Au NPs.AgAu bimetallic nanoparticles (BNPs), one of the most extensively studied bimetallic systems in the literatures, could have various structures and compositions depending on their preparation conditions. In the present work, catalytically highly active PVP-protected Agcore/Aushell BNPs of about 2.5 nm in diameter were fabricated from physical mixtures of aqueous dispersions of Au nanoparticles and Ag+ ions under dark conditions without using any reducing agents. The prepared Agcore/Aushell BNP colloidal catalysts, which possessed a high activity for aerobic glucose oxidation, were characterized by Ultraviolet–visible spectrophotometry (UV–Vis), Inductive coupled plasma emission spectrometer (ICP), Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Energy disperse spectroscopy (EDS) in High-resolution scanning transmission electron microscopy (HR-STEM). The highest activity (11,360 mol-glucose h−1 mol-metal−1) was observed for the BNPs with the Ag/Au atomic ratio of 1/9, the TOF value of which is about two times higher than that of Au nanoparticles with the particle size of 1.3 nm. The enhanced catalytic activity of the prepared Agcore/Aushell BNPs compared to Au NPs can be ascribed to the presence of negatively charged Au atoms resulted from electron donations from neighboring Ag atoms and PVP due to electronic charge transfer effects. XPS measurements as well as electronic structure calculation based on the density functional theory have revealed that the Au atoms are indeed negatively charged.The synthesis, characterization and catalytic activities for glucose oxidation of AgAu bimetallic nanoparticles (BNPs) with size of less than 2 nm are reported. The catalytic activity of Ag10Au90 BNPs was about two times higher than that of Au NPs, even the BNPs have a larger particle size than that of Au NPs.
Co-reporter:Xiaofeng Wang, Shaorui Sun, Zili Huang, Haijun Zhang, Shaowei Zhang
International Journal of Hydrogen Energy 2014 Volume 39(Issue 2) pp:905-916
Publication Date(Web):13 January 2014
DOI:10.1016/j.ijhydene.2013.10.122
•PVP-protected Au/Ni BNPs with size of 2.0 ± 0.7 nm in diameter were synthesized.•Catalytic activity of Au/Ni BNPs for hydrogen generation from NaBH4 was studied.•Catalytic activity of Au50Ni50 BNPs is 9 times higher than that of Au MNPs.•DFT and XPS proved the negatively charged Au atoms and positively charged Ni atoms.•The corresponding apparent activation energy was 30.3 kJ/mol for the Au50Ni50 BNPs.Poly(N-vinyl-2-pyrrolidone)(PVP)-protected Au/Ni bimetallic nanoparticles (BNPs) were prepared in one-vessel via chemical reduction of the corresponding ions with dropwise addition of NaBH4, and their catalytic activity in the hydrogen generation from hydrolysis of a basic NaBH4 solution was examined. The structure, particle size, and chemical composition of the resultant BNPs were characterized by Ultraviolet–visible spectrophotometry (UV–Vis), X-ray photoelectron spectroscopy (XPS), Transmission electron microscopy (TEM) and High-resolution transmission electron microscopy (HR-TEM). The effects of processing parameters such as metal composition, metal ion concentration, and mole ratio of PVP to metal ion on the hydrolysis of a basic NaBH4 solution were studied in detail. The results indicated that as-prepared Au/Ni BNPs showed a higher catalytic activity than corresponding monometallic NPs (MNPs) in the hydrogen generation from the hydrolysis reaction of a basic NaBH4 solution. Among all the MNPs and BNPs, Au/Ni BNPs with the atomic ratio of 50/50 exhibited the highest catalytic activity, showing a hydrogen generation rate as high as 2597 mL-H2 min−1 g-catalyst−1 at 30 °C, which can be ascribed to the presence of negatively charged Au atoms and positively charged Ni atoms. Based on the kinetic study of the hydrogen generation from the hydrolysis reaction of a basic NaBH4 solution over the PVP-protected Au/Ni BNPs, the corresponding apparent activation energy was determined as 30.3 kJ/mol for the BNPs with the atomic ratio of 50/50.
Co-reporter:Ying-Nan Cao;Shuang Du;Jun-Kai Wang
Journal of Sol-Gel Science and Technology 2014 Volume 72( Issue 1) pp:130-136
Publication Date(Web):2014 October
DOI:10.1007/s10971-014-3432-3
As an important ceramic possessing many excellent properties, zirconium diboride (ZrB2) has attracted considerable attention and found many ultra-high temperature applications. In this work, ZrB2 ultrafine powders were successfully synthesized by a combined one-pot sol–gel and boro/carbothermal reduction method using zirconium oxychloride, boric acid and glucose as starting materials. Pure ZrB2 was successfully synthesized at 1,500 °C for 2 h using the optimal molar ratios of n(B)/n(Zr) = 2.5 and n(C)/n(Zr) = 6.5. The as-prepared ZrB2 powders were characterized by X-ray diffraction, field-emission scanning electron microscopy, energy-dispersive spectroscopy, selected area electron diffraction and transmission electron microscopy. The grain size and the crystalline size of the as-prepared ZrB2 powders were found to be 1–2 μm and about 48 nm, respectively. Interestingly, some ZrB2 ultrafine hollow spheres (UHS) with diameters from 100 to 500 nm were also in situ formed with the ZrB2 ultrafine particles during the sol–gel and boro/carbothermal reduction process. The mechanism for the formation of these ZrB2 UHS was also proposed based on the experimental results.
Co-reporter:Haijun Zhang, Lilin Lu, Yingnan Cao, Shuang Du, Zhong Cheng, Shaowei Zhang
Materials Research Bulletin 2014 49() pp: 393-398
Publication Date(Web):
DOI:10.1016/j.materresbull.2013.09.025
Co-reporter:Lilin Lu, Shufang Zhu, Haijun Zhang, Shaowei Zhang
Computational and Theoretical Chemistry 2013 Volume 1019() pp:39-47
Publication Date(Web):1 September 2013
DOI:10.1016/j.comptc.2013.06.019
•Resveratrol.•Analogues.•Elongation of conjugated chain.•Improvement of antioxidative activities.Elongation of the conjugated chain of resveratrol has been proved to be an effective strategy to further improve its antioxidative capacity and radical scavenging ability. In this work, quantum chemical calculations based on density functional theory have been employed at B3LYP/6-311G(d,p) level of theory to study the influence of the conjugated chain length on equilibrium geometries and properties of relevant species. Our results show elongation of conjugated chain significantly decreases 4′-OH bond dissociation enthalpy (BDE), ionization potential (IP) and proton affinities (PAs) of phenolate ions in gas phase. In aqueous solution 4′-OH BDE, IP are lower as compared to that in gas phase, for PAs of phenolate ions almost no change is induced, but significant decrease in electron transfer enthalpy (ETE) is presented. These indicate that longer conjugated chain is favorable for the radical scavenging capacity and antioxidative activity. In addition, stable s-cis conformers of long chain reservatrol analogs are found to be more favorable for production of phenoxyl radicals and cation radicals as compared to trans conformers, with concomitant enhancement of the antioxidative activity.Graphical abstract
