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Photocatalytic hydrogen generation of Pt-Sr(Zr1-xYx)O3-δ-TiO2 heterojunction under the irradiation of simulated sunlight
Jianhui YAN, Qiang LIU, Luxiong GUAN, Feng LIANG, Haojie GU
Front Chem Chin. 2009, 4 (2): 121-126.
https://doi.org/10.1007/s11458-009-0026-7
The Pt-Sr(Zr1-xYx)O3-δ-TiO2 (Pt-SZYT) heterojunction photocatalysts were prepared by a photodeposition method. The composite particles were characterized by XRD, SEM, UV-Vis DRS, and PL techniques. Photocatalytic hydrogen generation in H2C2O4 aqueous solution under the irradiation of simulated sunlight was used as a probe reaction to evaluate the photocatalytic activity of the photocatalysts. The effects of the content of Pt loading and the concentration of oxalic acid on the photocatalytic activity of the catalyst were discussed. The continuous photocatalytic activity of the Pt-SZYT and the relationship between PL intensity and hydrogen generation were also discussed. The results show that Pt-SZYT catalysts had high photocatalytic activity of hydrogen generation. The content of Pt loading and the concentration of oxalic acid have important influence on the photocatalytic hydrogen generation. The optimal loading content of platinum was 0.90 mass%. Under this condition, the average rate of photocatalytic hydrogen generation was 1.68 mmol?h-1 when the concentration of oxalic acid was 50 mmol?L-1. The higher the photocatalytic activity, the weaker the PL intensity, which was demonstrated by the analysis of PL spectra.
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Study on thermal decomposition kinetics of N,N’-bis(5,5-dimethyl-2-phospha-2-thio-1,3-dioxan-2-yl)ethylenediamine in air
Yuanlin REN, Bowen CHENG, Jinshu ZHANG, Weimin KANG, Zhenhuan LI, Xupin ZHUANG
Front Chem Chin. 2009, 4 (2): 136-141.
https://doi.org/10.1007/s11458-009-0023-x
The thermal decomposition kinetics of the N,N¢-bis(5,5-dimethyl-2-phospha-2-thio-1,3-dioxan-2-yl)ethylenediamine (DPTDEDA) in air were studied by TG-DTG techniques. The kinetic parameters of the decomposition process for the title compound in the two main thermal decomposition steps were calculated through the Friedman and Flynn-Wall-Ozawsa (FWO) methods and the thermal decomposition mechanism of DPTDEDA was also studied with the Coats-Redfern and Achar methods. The results show that the activation energies for the two main thermal decomposition steps are 128.03 and 92.59 kJ?mol-1 with the Friedman method, and 138.75 and 106.78 kJ?mol-1 with the FWO method, respectively. Although there are two main thermal decomposition steps for DPTDEDA in air, the thermal decomposition mechanism of DPTDEDA in the two steps are the same, i.e. f(α) =3/2(1-α)4/3[(1-α)-1/3-1]-1.
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Study on the fluorescence and thermal stability of hybrid materials Eu(Phen)2Cl3/MCM-41
Liangzhun YANG, Lanfen ZHANG, Jun CHEN, Liwen REN, Yanting ZHU, Xiuying WANG, Xibin YU
Front Chem Chin. 2009, 4 (2): 149-153.
https://doi.org/10.1007/s11458-009-0035-6
A series of luminescent hybrid materials Eu(Phen)2Cl3/MCM-41 that the different assembled mass of Eu(Phen)2Cl3 included into the channels of MCM , have been synthesized by combining ultrasound technology. The properties of the hybrid materials were characterized by XRD(X-ray Diffraction), N2-adsorption-desorption, FT-IR and luminescence spectrum. The results show that the rare-earth compounds had been loaded into the holes of mesoporous material MCM-41. The luminescence intensities of the hybrid materials were improved as the increase of the loading concentration of the rare-earth complexes. The hybrid material has the maximal luminescence intensity when it reached the saturated loading concentration (7.17%). To compare with the pure rare-earth complex, the thermal stability of the hybrid materials were enhanced by about 100°C.
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Effect of sodium citrate on preparation of nano-sized cobalt particles by organic colloidal process
Huaping ZHU, Hao LI, Huiyu SONG, Shijun LIAO
Front Chem Chin. 2009, 4 (2): 154-159.
https://doi.org/10.1007/s11458-009-0022-y
Nano-sized cobalt particles with the diameter of 2 nm were prepared via an organic colloidal process with sodium formate, ethylene glycol and sodium citrate as the reducing agent, the solvent and the complexing agent, respectively. The effects of sodium citrate on the yield, crystal structure, particle size and size distribution of the prepared nano-sized cobalt particles were then investigated. The results show that the average particle diameter decreases from 200 nm to 2 nm when the molar ratio of sodium citrate to cobalt chloride changes from 0 to 6. Furthermore, sodium citrate plays a crucial role in the controlling of size distribution of the nano-sized particles. The size distribution of the particle without sodium citrate addition is in range from tens of nanometers to 300 or 400 nm, while that with sodium citrate addition is limited in the range of (2±0.25) nm. Moreover, it is found that the addition of sodium citrate as a complex agent could decrease the yield of the nano-sized cobalt particle.
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Study on the preparation and adsorption thermodynamics of chitosan microsphere resins
Lina YU, Dongfeng WANG, Weisheng HU, Haiyan LI, Minmin TANG
Front Chem Chin. 2009, 4 (2): 160-167.
https://doi.org/10.1007/s11458-009-0029-4
The aim of this research is to study the thermodynamic behavior of resins of chitosan microspheres (RCM) in adsorbing Cu2+, so that the theoretical basis of the application of RCM to eliminate metal ions in wastewater or fruit and vegetable juice can be obtained. First, RCM were prepared from chitosan as a raw material by using reverse phase suspension cross-linking polymerization, and some physicochemical properties of RCM were characterized. Second, the adsorption behavior of Cu2+ onto RCM was investigated by the batch method. The results show that the diameter of the microspheres was relatively uniform and the surface of microspheres was compacted with pores. The physical properties of the RCM were as follows: water content 51.982%, skeletal density 1.212 g?cm-3, pileup density 0.862 g?mL-1, porosity was in 0.554 and crosslinking degree was in 13.581%. The saturated adsorption capacity of RCM for Cu2+ was 0.993 mmol?g-1. At the same time, the results also indicated that the adsorption of RCM for Cu2+ followed the Langmuir isotherm equation: Ce/Q=11.614+ 1.0075Ce at 313 K and the adsorption appeared to be of the monomolecular type. The adsorption was found through thermodynamic study to be a spontaneous endothermic process of increased entropy. The adsorption potential decreased gradually as Cu2+ concentration increased at the same temperature and it increased as temperature increased at the same initial concentration of Cu2+.
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Synthesis and mesomorphism of mixed ether-ester tail triphenylene discotic liquid crystals with long alkyloxy peripheral chains
Biqin WANG, Caiyan GAO, Keqing ZHAO, Ping HU
Front Chem Chin. 2009, 4 (2): 177-185.
https://doi.org/10.1007/s11458-009-0012-0
Symmetrical and asymmetrical triphenylene discotic liquid crystals with two kinds of different peripheral chains, sym-TP(OC11H23)3(O2CR)3 and asym-TP(OC11H23)3(O2CR)3, (R= CH2OC2H5, CH2OC3H7, CH2OC4H9, CH2OC5H11, C3H7, C4H9, C5H11, C6H13, C7H15) were synthesized. Their thermotropic liquid crystalline properties were studied by polarizing optical microscopy (POM) and differential scanning calorimetry (DSC). The results showed that the asymmetrical compounds had higher melting and clearing points than that of their corresponding symmetrical compounds. For the same series of compounds, TP(OC11H23)3(O2CR)3, their melting points decrease and clearing points increase gradually with the lengthening of ester chains. Most of the b-oxygen containing esters of triphenylene derivatives, TP(OC11H23)3(O2CR)3, (R=CH2OC2H5, CH2OC3H7, CH2OC4H9, CH2OC5H11), symmetrically or asymmetrically attached on triphenylene cores, have higher melting and clearing points than those of triphenylene derivatives, TP(OC11H23)3(O2CR)3, (R=C4H9, C5H11, C6H13, C7H15), with the same length of peripheral chains. The triphenylene derivatives with longer peripheral chains have shown mesophase at room temperature.
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The design, synthesis of amide KARI inhibitors and their biological activities
Baolei WANG, Yi MA, Yonghong LI, Suhua WANG, Zhengming LI
Front Chem Chin. 2009, 4 (2): 186-190.
https://doi.org/10.1007/s11458-009-0021-z
Ketol-acid reductoisomerase(KARI) is a promising target for the design of herbicides yet there are only few reports on the molecular design of KARI inhibitors. In this paper, based on the reported 0.165 nm high resolution crystal structure of the spinach KARI complex, 279 molecules with low binding energy toward KARI were obtained from an MDL/ACD 3D database search using the program DOCK 4.0. According to the structural information of 279 molecules provided, some amide compounds have been designed and synthesized. The bioassay results show that most of these amides had inhibitory activity to rice KARI at a test concentration of 200 μg/mL. Among which eight amides, compounds 1 and 6 show 57.4% and 48.1% inhibitory activity to KARI. The herbicidal activities of these amides were further investigated on di-cotyledonous rape (Brassica campestris) and mono-cotyledonous barnyardgrass (Echinochloa crusgalli). Compounds 1 and 6 were more favorable than others and showed 52.0% and 72.6% inhibitory activity on rape root at 100 μg/mL concentration, respectively. These amides could be further optimized for finding more potent candidates.
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Synthesis, characterization, and gas permeation properties of 6FDA-2,6-DAT/mPDA copolyimides
Lina WANG, Yiming CAO, Meiqing ZHOU, Xiaozhi QIU, Quan YUAN
Front Chem Chin. 2009, 4 (2): 215-221.
https://doi.org/10.1007/s11458-009-0028-5
The goal of this work is to explore new polyimide materials that exhibit both high permeability and high selectivity for specific gases. Copolyimides offer the possibility of preparing membranes with gas permeabilities and selectivities not obtainable with homopolyimides. A series of novel fluorinated copolyimides were synthesized with various diamine compositions by chemical imidization in a two-pot procedure. Polyamic acids were prepared by stoichiometric addition of solid dianhydride in portions to the diamine(s). The gas permeation behavior of 2,2’-bis(3,4’-dicarboxyphenyl) hexafluoropropane dianhydride(6FDA)-2,6-diamine toluene (2,6-DAT)/ 1,3-phenylenediamine (mPDA) polyimides was investigated. The physical properties of the copolyimides were characterized by IR, DSC and TGA. The glass transition temperature increased with increase in 2,6-DAT content. All the copolyimides were soluble in most of the common solvents. The gas permeability coefficients decreased with increasing mPDA content. However, the permselectivity of gas pairs such as H2/N2, O2/N2, and CO2/CH4 was enhanced with the incorporation of mPDA moiety. The permeability coefficients of H2, O2, N2, CO2 and CH4 were found to decrease with the increasing order of kinetic diameters of the penetrant gases. 6FDA-2,6-DAT/mPDA (3∶1) copolyimide and 6FDA-2,6-DAT polyimide had high separation properties for H2/N2, O2/N2, CO2/CH4. Their H2, O2 and CO2 permeability coefficients were 64.99 Barrer, 5.22 Barrer, 23.87 Barrer and 81.96 Barrer, 8.83 Barrer, 39.59 Barrer, respectively, at 35°C and 0.2 MPa (1 Barrer=10-10 cm3 (STP)?cm?cm-2?s-1?cmHg-1) and their ideal permselectivities of H2/N2, O2/N2 and CO2/CH4 were 69.61, 6.09, 63.92 and 53.45, 5.76, 57.41, respectively. Moreover, all of the copolyimides studied in this work exhibited similar performance, lying on or above the existing upper bound trade-off lines between permselectivity and permeability. They may be utilized for commercial gas separation membrane materials.
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Studies on the particle size control of gelatin microspheres
Ruixue SUN, Jingjing SHI, Yanchuan GUO, Lijuan CHEN
Front Chem Chin. 2009, 4 (2): 222-228.
https://doi.org/10.1007/s11458-009-0031-x
A series of gelatin microspheres (GMs) were prepared through emulsification-coacervation method in water-in-oil (w/o) emulsions. The influence of preparation parameters on particle size, surface morphology, and dispersion of GMs was examined. The studied preparation parameters include concentration of gelatin solutions, concentration of the emulsifier, w/o ratio, emulsifying time, stirring speed, and so on. The surface morphology, dispersion, and particle sizes of GMs were determined by the scanning electron microscopy (SEM), SemAfore 4 Demo software, and particle size distribution graphic charts. The experimental results indicated that increasing the concentration of gelatin solution would increase the particle size of GMs. When the solution concentration increased from 0.050 to 0.200 g/mL gradually, the particle size increased correspondingly. The relationship between the two quantities was linear. On the contrary, increasing the concentration of the emulsifier would decrease the particle size of GMs. Furthermore, the particle size reduced quickly at initial time and slowed down latterly. With the increase of emulsifier concentration from 0 to 0.020 g/mL, the mean diameters of GMs decreased from 17.32 to 5.38 μm. However, the particle size dwindled slowly when emulsifier concentration was higher than 0.020 g/mL. The excellent result was obtained with the condition of 0.050 g/mL of emulsifier concentration, 0.100 g/mL of gelatin solution concentration, 1/5 of w/o ratio, 10 min of emulsifying time, and 900 r/min of the stirring speed. The GMs prepared at this condition had the smallest sizes, the narrowest size distribution, the best spherical shape, and fluidity. The w/o ratio has the same influence on particle size of GMs as that of gelatin solution concentration. With the increase of w/o ratio, the average particle sizes increased linearly, and the surface of microspheres become smoother as well. It is supposed that w/o ratio can be used to change the diameters and surface morphologies of GMs. The emulsifying time has little influence on the mean diameters of GMs, but it affects the dispersion of GMs apparently. When the emulsifying time was shorter than 5 min, the GMs had bad dispersion. After increasing the emulsifying time to 13 min, the dispersion of GMs changed greatly, whereas the dispersion of GMs became bad again when the emulsifying time was longer than 13 min. According to the experimental results, 13 min was considered to be the best emulsifying time. The stirring speed has the similar influence on GMs’ morphologies as that of emulsifying time. Slow stirring rate made large size distribution and bad spherical shape of GMs; excessive stirring speed results in aggregation among GMs likewise. The smaller size distribution and better spherical shape of GMs were observed under the stirring rate between 500 and 1500 r/min by SEM. In conclusion, increasing the concentration of gelatin solution or w/o ratio would increase the particle sizes of GMs, increasing the concentration of the emulsifier would decrease the sizes of GMs at proper emulsifying time, and stirring speed would get the best spherical shape of GMs. These are the basic laws governing the design and manufacture of the GMs.
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