A few hundreds nanometer-sized mesoporous silica and alumina spheres were synthesized in organic solvents. The impacts of ammonia, N, N-dimethylformamide (DMF) and stirring speed were also investigated.
A novel process for synthesizing nano-ceramics powders, named mechanical & therm al activation processing, is discussed in the present paper. It is a processing based on thermal activation in liquid phase (molten ...A novel process for synthesizing nano-ceramics powders, named mechanical & therm al activation processing, is discussed in the present paper. It is a processing based on thermal activation in liquid phase (molten salt) after mechanical activ ation. The nanometer-sized TiC particles (15-20nm) have been synthesized by the method, and analyzed by X-ray diffraction (XRD), transmission electron microscop e (TEM), scanning electron microscopy (SEM) and energy dispersion X-ray (EDX) sp ectroscopy. An interface interaction between liquid (molten salt) and solid (fin al product particles) phases plays a dominating role for the control of product particles size. The mechanism for the formation of nanometer-sized TiC particles has been discussed.展开更多
Novel nanometer-sized ScAlMgO4:Eu3+ phosphors were successfully synthesized by the citric acid complexation method.The mean particle size of the obtained powders was within the range of 100~150 nm according to the ...Novel nanometer-sized ScAlMgO4:Eu3+ phosphors were successfully synthesized by the citric acid complexation method.The mean particle size of the obtained powders was within the range of 100~150 nm according to the SEM patterns.In ScAlMgO4:Eu3+ showed strong characteristic red emission,of which the maximum emission peak was located at 629 nm for ultraviolet(UV) excitation.The dependence of photoluminescence intensity on Eu3+ concentration was also studied in detail,and the emission intensity of Sc1-xEuxAlMgO4 was about 10% at optimized Eu3+ concentration.Furthermore,the luminescence decay measurements showed that the lifetimes of Eu3+ were in the range of millisecond.The obtained ScAlMgO4:Eu3+ phosphors with nanometer size and excellent luminescence efficiency would be potential red phosphors in plasma display panels.展开更多
Nanometer-sized SnO_(2) particles were prepared by a sol-gel method using inorganic salt as a precursor material. Its crystallization was investigated by means of TG-DTA,IR absorption spectra, X-ray diffractometry and...Nanometer-sized SnO_(2) particles were prepared by a sol-gel method using inorganic salt as a precursor material. Its crystallization was investigated by means of TG-DTA,IR absorption spectra, X-ray diffractometry and TEM as well as its resistivity change and the gas sensitivity varied with temperature were measured in various reducing gas. The results indicate that well-crystallized nano-sized SnO_(2)with size around 15nm can be obtained at annealing temperature 600℃. The activation energy for the growth of nano-SnO_(2) was calculated to be 26.55kJ.mol^(-1) when the annealing temperature was higher than 500℃. The measurements also show that there is a peculiar resistance change varied with temperature for nano SnO_(2).It has relevance to the increase in surface adsorbed oxygen. The selective detectivities to C_(4)H_(10) and petrol can be increased when ruthenium ion was doped in nano SnO_(2)as a catalyst and so do the gas sensitivity to CO,CH_(4),H_(2) etc. when rhodium ion was doped in.The detection to the several reducing gas can be realized when the temperature ranged from 260℃ to 400℃.展开更多
Described here are the fabrication and characterization of carbon fiber cylinder ultramicroelectrodes with cylinder length of less than 100 am, total tip diameter of several hundreds nanometers. The electrodes have be...Described here are the fabrication and characterization of carbon fiber cylinder ultramicroelectrodes with cylinder length of less than 100 am, total tip diameter of several hundreds nanometers. The electrodes have been fabricated by direct etching of carbon fiber using an ion beam thinner. Optical microscopy, scanning electron microscopy (SEM), cyclic voltammetry have been employed to characterize those electrodes. The experimental results obtained indicate the electrodes can be used for in vivo detection of neurotransmitters such as dopamine, 5—hydroxytryptamine in a single cell.展开更多
In this paper, a two-dimensional nanometer scale tip-plate discharge model has been employed to study nanoscale electrical discharge in atmospheric conditions. The field strength dis- tributions in a nanometer scale t...In this paper, a two-dimensional nanometer scale tip-plate discharge model has been employed to study nanoscale electrical discharge in atmospheric conditions. The field strength dis- tributions in a nanometer scale tip-to-plate electrode arrangement were calculated using the finite element analysis (FEA) method, and the influences of applied voltage amplitude and frequency as well as gas gap distance on the variation of effective discharge range (EDR) on the plate were also investigated and discussed. The simulation results show that the probe with a wide tip will cause a larger effective discharge range on the plate; the field strength in the gap is notably higher than that induced by the sharp tip probe; the effective discharge range will increase linearly with the rise of excitation voltage, and decrease nonlinearly with the rise of gap length. In addition, probe dimension, especially the width/height ratio, affects the effective discharge range in different manners. With the width/height ratio rising from 1 : 1 to 1 : 10, the effective discharge range will maintain stable when the excitation voltage is around 50 V. This will increase when the excitation voltage gets higher and decrease as the excitation voltage gets lower. Fhrthermore, when the gap length is 5 nm and the excitation voltage is below 20 V, the diameter of EDR in our simulation is about 150 nm, which is consistent with the experiment results reported by other research groups. Our work provides a preliminary understanding of nanometer scale discharges and establishes a predictive structure-behavior relationship.展开更多
The chemical equilibrium and reaction kinetic behavior in the synthesis of polyoxymethylene dimethyl ethers (DMMn) were investigated over sulfated titania in order to reveal the decisive factor controlling the react...The chemical equilibrium and reaction kinetic behavior in the synthesis of polyoxymethylene dimethyl ethers (DMMn) were investigated over sulfated titania in order to reveal the decisive factor controlling the reaction. The results showed that the molar ratio of adjacent DMMn products in equilibrium solution had the same value, which depended absolutely on the reaction temperature. Meanwhile, the reactions had the same DMMn products distributions under varied reaction conditions. The equilibrium constants of the related step-wise reactions for DMMn formation were equal, which were calculated based on the bulk compositions of the reaction solution. And thus, the selectivity to DMMn was mainly controlled by the chemical equilibrium, i.e., thermodynamic control. In brief, the present results provide some guidance for future synthesis of DMMn.展开更多
Doping amine functional groups into SiO2/TiO2 films for enhancing the decomposition of formaldehyde has been investigated using the modified sol-gel method to prepare organic-inorganic hybrid photocatalysts via the co...Doping amine functional groups into SiO2/TiO2 films for enhancing the decomposition of formaldehyde has been investigated using the modified sol-gel method to prepare organic-inorganic hybrid photocatalysts via the co-condensation reaction of methyltrimethoxysilane (MTMOS) and amine functional groups, n-(2-Aminoethyl)-3-aminopropyl-trimethoxysilane (AEAPTMS) and 3-aminopropyl-trimethoxysilane (APTMS) were selected to study the effect of amine functional groups on the enhancement of formaldehyde adsorption and degradation under a UV irradiation process. Physicocbemical properties of prepared photocatalysts were characterized with nitrogen adsorption-desorption isotherms measurement, X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy. The results indicated that the APTMS/SiO2/TiO2 film demonstrated a degradation efficiency of 79% superior to those of SiO2/TrO2 and AEAPTMS/SiO2/TiO2 films due to the synergetic effect of adsorption and photocatalytic properties. The APTMS/SiO2/TiO2 film can be recycled with about 7% decreasing of degradation efficiency after seven cycles.展开更多
Yellowish nitrogen-doped titania was produced through sol-gel method in mild condition, with the elemental nitrogen derived from aqua ammonia. The titania catalysts were characterized using XRD, BET, TEM, XPS, and UV-...Yellowish nitrogen-doped titania was produced through sol-gel method in mild condition, with the elemental nitrogen derived from aqua ammonia. The titania catalysts were characterized using XRD, BET, TEM, XPS, and UV-Vis diffuse reflectance spectrophotometer, and their photocatalytic activities were evaluated under UV and visible light, respec tively. The XRD results showed that all titania catalysts were anatase. More significantly, the crystallite size of nitrogen-doped titania increased with an increase in N/Ti proportion, and the doping of nitrogen could extend the absorption shoulder into the visible-light region, thus it possessed a higher visible-light activity illustrated by decolorization of methyl orange (65.3%) under the irradiation of visible light, whereas pure titania showed little of such kind of visible light activity. The UV-light activity of nitrogen-doped titania catalysts was worse than that of pure titania and Degussa P25. In the range of N/Ti proportion of 4-10 mol%, the activity of nitrogen-doped titania weakened appreciably in the visible-light region as the N/Ti proportion increased, whereas a reverse relationship existed under the irradiation of UV light.展开更多
The 12-molybdosphoric acid mixed with titania (MPA-TiO2) was found to be a novel and efficient catalyst for the synthesis of diphenyl carbonate (DPC) via transesterification of dimethyl carbonate (DMC) and pheno...The 12-molybdosphoric acid mixed with titania (MPA-TiO2) was found to be a novel and efficient catalyst for the synthesis of diphenyl carbonate (DPC) via transesterification of dimethyl carbonate (DMC) and phenol. The X-ray diffraction (XRD) and infrared (IR) techniques were employed to characterize the prepared catalysts. The effect of the weight ratio of the 12-molybdosphoric acid to titania on the transesterification was investigated. A 13.1% yield of DPC and an 11.6% yield of methyl phenyl carbonate (MPC) were obtained over MPA-TiO2 with the weight ratio of MPA to TiO2 as 5:1.展开更多
Transition metal-doping could effectively extend the light response range of TiO _2 photocatalysts from the ultraviolet(UV)to the visible region.Co-doped brookite titanium dioxide(Co–TiO_2)photocatalysts were synthes...Transition metal-doping could effectively extend the light response range of TiO _2 photocatalysts from the ultraviolet(UV)to the visible region.Co-doped brookite titanium dioxide(Co–TiO_2)photocatalysts were synthesized via the hydrothermal method with titanium tetrachloride as the raw material and cobalt chloride hexahydrate as the dopant.The prepared Co–TiO_2 photocatalysts were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),Raman spectroscopy,X-ray photoelectron spectroscopy(XPS)and UV–Vis diffuse reflectance spectroscopy(UV–Vis DRS).The photocatalytic activities of Co–TiO _2 photocatalysts were evaluated by photocatalytic degradation of isopropanol alcohol(IPA),a typical volatile organic compound(VOC),under visible light.The influences ofdifferent Co doping rates,initial concentrations of IPA gas and the amounts of photocatalyst addition were also studied.At the same time,the enhancement mechanism ofcobalt ions as a trap for photogenerated holes was discussed.Thus,we found the optimum doping rate,initial concentration of IPA gas and amount of photocatalyst to add.The results show that the mesoporous Co–TiO _2 photocatalysts possess smaller size particles,larger specific surface area,lower forbidden bandgap energy(Eg)and better photocatalytic activity than pure brookite TiO _2.When the doping of Co was 7% by mass,the initial concentration ofIPA gas was 1.0×10^(-6 )mol/L and the addition of Co–TiO_2 photocatalysts was 50 mg,the best photocatalytic activity was achieved.Furthermore,the degradation rate ofIPA was up to 91%,which shows great potential for waste water treatment.展开更多
The nanoscale titania coated silica was prepared via a two-step precipitating approach, where the nanoscale silica nuclei were first prepared by passing an aqueous solution of sodium silicate through an ion-exchange r...The nanoscale titania coated silica was prepared via a two-step precipitating approach, where the nanoscale silica nuclei were first prepared by passing an aqueous solution of sodium silicate through an ion-exchange resin bed, then coated with the precipitation from hydrolyzed butyl titanate in an ethanol-hexane mixture at a low pH value in the presence of poly(ethylene oxide) polyamine salt(PPA) at a high temperature of 90 ℃. In the second-step precipitating process, the spontaneously precipitated titania shell on the silica nuclei was stabilized in the suspension solution with the help of the adsorption of PPA on the particles. A possible precipitating mechanism was suggested. Furthermore, the amorphous titania shell could undergo crystallization from the amorphous to the anatase structure at a high temperature of 650 ℃, and a further phase transition from the anatase to the rutile structure in the different sintering processes at a rising temperature of 750 ℃.展开更多
Nanostructured pure-Ti O_2 and Cu3%-Ti O_2 were successfully synthesized via co-precipitation method. The X-ray diffraction(XRD) result proves that the synthesized sample were predominantly in anatase phase with size ...Nanostructured pure-Ti O_2 and Cu3%-Ti O_2 were successfully synthesized via co-precipitation method. The X-ray diffraction(XRD) result proves that the synthesized sample were predominantly in anatase phase with size in the range of 8~16 nm, which are in good agreement with the transmission electron microscopy data. Owing to doping of copper, not only did the thermal stability of the Ti O_2 decrease, but also a significant decrease in its particle size and a shift of the adsorption edge to a higher wavelength region appear. The activity of both pure-Ti O_2 and Cu3%-doped Ti O_2 was tested to study their ability to decolorize congo red(CR) dye in aqueous solution. We observed that the CR dye was decolorized faster by Cu3%-Ti O_2 than pure-Ti O_2. Results of this study demonstrate a potential application of the synthesized sample for decolorizing dye pollutants from aqueous waste.展开更多
Paratungstate-loaded titania catalysts were prepared %via% the addition of a series of aqueous solutions of paratungstate(denoted as W_ 7) into an isopropanol solution of Ti[OCH(CH_ 3)_ 2]_ 4 by means of the sol-gel m...Paratungstate-loaded titania catalysts were prepared %via% the addition of a series of aqueous solutions of paratungstate(denoted as W_ 7) into an isopropanol solution of Ti[OCH(CH_ 3)_ 2]_ 4 by means of the sol-gel method. The catalysts were characterized by EDX, BET, FTIR, UV-Vis DRS, XRD and the results indicate that such paratungstate-loaded catalysts maintained their heptatungstate structure in the anatase titania matrix up to 400 ℃. The catalysts were tested for the heterogeneous photodegradation of chlorobenzene in aqueous media and showed a better catalytic activity than P-25 TiO_ 2 because paratungstate can prevent the recombination of the holes and electrons produced during irradiation. Moreover, the paratungstate-loaded titania catalysts can resist the disaggregation during the photoirradiation and can be easily recycled from the aqueous suspensions after reactions.展开更多
Well-organized mesoporous titania particles and thin films were successfully synthesized by using tetrabutyl titanate as the inorganic precursor and triblock copolymer (Pluronic P123) as the template via evaporation...Well-organized mesoporous titania particles and thin films were successfully synthesized by using tetrabutyl titanate as the inorganic precursor and triblock copolymer (Pluronic P123) as the template via evaporationinduced self-assembly process. The resulting materials were characterized by high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD). Fourier-transform infrared spectroscopy (FT-IR),Brunauer-Emmett-Teller (BET) and atomic force microscopy (AFM). Macro shape of mesoporous titania would greatly influence the mesostructure of materials, and the probable reasons were also discussed.展开更多
基金the National Natural Science Foundation of China(Grant No. 29873012, 29925309) and National Ed-ucation Ministry.
文摘A few hundreds nanometer-sized mesoporous silica and alumina spheres were synthesized in organic solvents. The impacts of ammonia, N, N-dimethylformamide (DMF) and stirring speed were also investigated.
基金The project was supported by China Postdoctoral Science Foundation(No.2003034452)National Natural Science Foundation of China(No.50371027).
文摘A novel process for synthesizing nano-ceramics powders, named mechanical & therm al activation processing, is discussed in the present paper. It is a processing based on thermal activation in liquid phase (molten salt) after mechanical activ ation. The nanometer-sized TiC particles (15-20nm) have been synthesized by the method, and analyzed by X-ray diffraction (XRD), transmission electron microscop e (TEM), scanning electron microscopy (SEM) and energy dispersion X-ray (EDX) sp ectroscopy. An interface interaction between liquid (molten salt) and solid (fin al product particles) phases plays a dominating role for the control of product particles size. The mechanism for the formation of nanometer-sized TiC particles has been discussed.
基金supported by the Natual Science Foundation of Fujian Province (2006H0041)
文摘Novel nanometer-sized ScAlMgO4:Eu3+ phosphors were successfully synthesized by the citric acid complexation method.The mean particle size of the obtained powders was within the range of 100~150 nm according to the SEM patterns.In ScAlMgO4:Eu3+ showed strong characteristic red emission,of which the maximum emission peak was located at 629 nm for ultraviolet(UV) excitation.The dependence of photoluminescence intensity on Eu3+ concentration was also studied in detail,and the emission intensity of Sc1-xEuxAlMgO4 was about 10% at optimized Eu3+ concentration.Furthermore,the luminescence decay measurements showed that the lifetimes of Eu3+ were in the range of millisecond.The obtained ScAlMgO4:Eu3+ phosphors with nanometer size and excellent luminescence efficiency would be potential red phosphors in plasma display panels.
文摘Nanometer-sized SnO_(2) particles were prepared by a sol-gel method using inorganic salt as a precursor material. Its crystallization was investigated by means of TG-DTA,IR absorption spectra, X-ray diffractometry and TEM as well as its resistivity change and the gas sensitivity varied with temperature were measured in various reducing gas. The results indicate that well-crystallized nano-sized SnO_(2)with size around 15nm can be obtained at annealing temperature 600℃. The activation energy for the growth of nano-SnO_(2) was calculated to be 26.55kJ.mol^(-1) when the annealing temperature was higher than 500℃. The measurements also show that there is a peculiar resistance change varied with temperature for nano SnO_(2).It has relevance to the increase in surface adsorbed oxygen. The selective detectivities to C_(4)H_(10) and petrol can be increased when ruthenium ion was doped in nano SnO_(2)as a catalyst and so do the gas sensitivity to CO,CH_(4),H_(2) etc. when rhodium ion was doped in.The detection to the several reducing gas can be realized when the temperature ranged from 260℃ to 400℃.
基金This project was supported by the National Science Foundation of China and Doctoral Programme from State Education Commission Foundation of China
文摘Described here are the fabrication and characterization of carbon fiber cylinder ultramicroelectrodes with cylinder length of less than 100 am, total tip diameter of several hundreds nanometers. The electrodes have been fabricated by direct etching of carbon fiber using an ion beam thinner. Optical microscopy, scanning electron microscopy (SEM), cyclic voltammetry have been employed to characterize those electrodes. The experimental results obtained indicate the electrodes can be used for in vivo detection of neurotransmitters such as dopamine, 5—hydroxytryptamine in a single cell.
基金supported in part by External Cooperation Program of Chinese Academy of Sciences(No.GJHZ1218)National Natural Science Foundation of China(No.61004133)SSSTC JRP awards 2011(IZLCZ2 138953)
文摘In this paper, a two-dimensional nanometer scale tip-plate discharge model has been employed to study nanoscale electrical discharge in atmospheric conditions. The field strength dis- tributions in a nanometer scale tip-to-plate electrode arrangement were calculated using the finite element analysis (FEA) method, and the influences of applied voltage amplitude and frequency as well as gas gap distance on the variation of effective discharge range (EDR) on the plate were also investigated and discussed. The simulation results show that the probe with a wide tip will cause a larger effective discharge range on the plate; the field strength in the gap is notably higher than that induced by the sharp tip probe; the effective discharge range will increase linearly with the rise of excitation voltage, and decrease nonlinearly with the rise of gap length. In addition, probe dimension, especially the width/height ratio, affects the effective discharge range in different manners. With the width/height ratio rising from 1 : 1 to 1 : 10, the effective discharge range will maintain stable when the excitation voltage is around 50 V. This will increase when the excitation voltage gets higher and decrease as the excitation voltage gets lower. Fhrthermore, when the gap length is 5 nm and the excitation voltage is below 20 V, the diameter of EDR in our simulation is about 150 nm, which is consistent with the experiment results reported by other research groups. Our work provides a preliminary understanding of nanometer scale discharges and establishes a predictive structure-behavior relationship.
基金supported by the National Natural Science Foundation of China(NSFC,No.21203220 and 21133011)China Postdoctoral Science Foundation(No.2014M551674)+1 种基金Jiangsu Planned Projects for Postdoctoral Research Funds(No.1302070C)the National Basic Research Program of China(973 Program,No.2011CB201404)
文摘The chemical equilibrium and reaction kinetic behavior in the synthesis of polyoxymethylene dimethyl ethers (DMMn) were investigated over sulfated titania in order to reveal the decisive factor controlling the reaction. The results showed that the molar ratio of adjacent DMMn products in equilibrium solution had the same value, which depended absolutely on the reaction temperature. Meanwhile, the reactions had the same DMMn products distributions under varied reaction conditions. The equilibrium constants of the related step-wise reactions for DMMn formation were equal, which were calculated based on the bulk compositions of the reaction solution. And thus, the selectivity to DMMn was mainly controlled by the chemical equilibrium, i.e., thermodynamic control. In brief, the present results provide some guidance for future synthesis of DMMn.
基金supported by the Royal Golden Jubilee of Thailand Research Fundthe Department of Chemical Engineering at King Mongkut’s University of Technology Thonburi
文摘Doping amine functional groups into SiO2/TiO2 films for enhancing the decomposition of formaldehyde has been investigated using the modified sol-gel method to prepare organic-inorganic hybrid photocatalysts via the co-condensation reaction of methyltrimethoxysilane (MTMOS) and amine functional groups, n-(2-Aminoethyl)-3-aminopropyl-trimethoxysilane (AEAPTMS) and 3-aminopropyl-trimethoxysilane (APTMS) were selected to study the effect of amine functional groups on the enhancement of formaldehyde adsorption and degradation under a UV irradiation process. Physicocbemical properties of prepared photocatalysts were characterized with nitrogen adsorption-desorption isotherms measurement, X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy. The results indicated that the APTMS/SiO2/TiO2 film demonstrated a degradation efficiency of 79% superior to those of SiO2/TrO2 and AEAPTMS/SiO2/TiO2 films due to the synergetic effect of adsorption and photocatalytic properties. The APTMS/SiO2/TiO2 film can be recycled with about 7% decreasing of degradation efficiency after seven cycles.
基金the Open Fund of the Key Laboratory of Enhanced Heat and Energy Conservation of Chinese Ministry of Education, South China University of Technology.
文摘Yellowish nitrogen-doped titania was produced through sol-gel method in mild condition, with the elemental nitrogen derived from aqua ammonia. The titania catalysts were characterized using XRD, BET, TEM, XPS, and UV-Vis diffuse reflectance spectrophotometer, and their photocatalytic activities were evaluated under UV and visible light, respec tively. The XRD results showed that all titania catalysts were anatase. More significantly, the crystallite size of nitrogen-doped titania increased with an increase in N/Ti proportion, and the doping of nitrogen could extend the absorption shoulder into the visible-light region, thus it possessed a higher visible-light activity illustrated by decolorization of methyl orange (65.3%) under the irradiation of visible light, whereas pure titania showed little of such kind of visible light activity. The UV-light activity of nitrogen-doped titania catalysts was worse than that of pure titania and Degussa P25. In the range of N/Ti proportion of 4-10 mol%, the activity of nitrogen-doped titania weakened appreciably in the visible-light region as the N/Ti proportion increased, whereas a reverse relationship existed under the irradiation of UV light.
文摘The 12-molybdosphoric acid mixed with titania (MPA-TiO2) was found to be a novel and efficient catalyst for the synthesis of diphenyl carbonate (DPC) via transesterification of dimethyl carbonate (DMC) and phenol. The X-ray diffraction (XRD) and infrared (IR) techniques were employed to characterize the prepared catalysts. The effect of the weight ratio of the 12-molybdosphoric acid to titania on the transesterification was investigated. A 13.1% yield of DPC and an 11.6% yield of methyl phenyl carbonate (MPC) were obtained over MPA-TiO2 with the weight ratio of MPA to TiO2 as 5:1.
基金supported by the National Key Basic Research and Development Program of China ("973" program,nos. 2012CB720100 and 2014CB239300)the National Natural Science Foundation of China (nos.21406164 and 21466035)+1 种基金the Science and Technology Innovation Guide Funds of Civil Aviation Administration of China (MHRD20140209)the Fundamental Research Funds for the Central Universities (no.3122016L016)
文摘Transition metal-doping could effectively extend the light response range of TiO _2 photocatalysts from the ultraviolet(UV)to the visible region.Co-doped brookite titanium dioxide(Co–TiO_2)photocatalysts were synthesized via the hydrothermal method with titanium tetrachloride as the raw material and cobalt chloride hexahydrate as the dopant.The prepared Co–TiO_2 photocatalysts were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),Raman spectroscopy,X-ray photoelectron spectroscopy(XPS)and UV–Vis diffuse reflectance spectroscopy(UV–Vis DRS).The photocatalytic activities of Co–TiO _2 photocatalysts were evaluated by photocatalytic degradation of isopropanol alcohol(IPA),a typical volatile organic compound(VOC),under visible light.The influences ofdifferent Co doping rates,initial concentrations of IPA gas and the amounts of photocatalyst addition were also studied.At the same time,the enhancement mechanism ofcobalt ions as a trap for photogenerated holes was discussed.Thus,we found the optimum doping rate,initial concentration of IPA gas and amount of photocatalyst to add.The results show that the mesoporous Co–TiO _2 photocatalysts possess smaller size particles,larger specific surface area,lower forbidden bandgap energy(Eg)and better photocatalytic activity than pure brookite TiO _2.When the doping of Co was 7% by mass,the initial concentration ofIPA gas was 1.0×10^(-6 )mol/L and the addition of Co–TiO_2 photocatalysts was 50 mg,the best photocatalytic activity was achieved.Furthermore,the degradation rate ofIPA was up to 91%,which shows great potential for waste water treatment.
基金Supported by the State Key L aboratory of Shanghai Institute of Ceram ics and State Key L aboratory of Surface Physicsin China
文摘The nanoscale titania coated silica was prepared via a two-step precipitating approach, where the nanoscale silica nuclei were first prepared by passing an aqueous solution of sodium silicate through an ion-exchange resin bed, then coated with the precipitation from hydrolyzed butyl titanate in an ethanol-hexane mixture at a low pH value in the presence of poly(ethylene oxide) polyamine salt(PPA) at a high temperature of 90 ℃. In the second-step precipitating process, the spontaneously precipitated titania shell on the silica nuclei was stabilized in the suspension solution with the help of the adsorption of PPA on the particles. A possible precipitating mechanism was suggested. Furthermore, the amorphous titania shell could undergo crystallization from the amorphous to the anatase structure at a high temperature of 650 ℃, and a further phase transition from the anatase to the rutile structure in the different sintering processes at a rising temperature of 750 ℃.
文摘Nanostructured pure-Ti O_2 and Cu3%-Ti O_2 were successfully synthesized via co-precipitation method. The X-ray diffraction(XRD) result proves that the synthesized sample were predominantly in anatase phase with size in the range of 8~16 nm, which are in good agreement with the transmission electron microscopy data. Owing to doping of copper, not only did the thermal stability of the Ti O_2 decrease, but also a significant decrease in its particle size and a shift of the adsorption edge to a higher wavelength region appear. The activity of both pure-Ti O_2 and Cu3%-doped Ti O_2 was tested to study their ability to decolorize congo red(CR) dye in aqueous solution. We observed that the CR dye was decolorized faster by Cu3%-Ti O_2 than pure-Ti O_2. Results of this study demonstrate a potential application of the synthesized sample for decolorizing dye pollutants from aqueous waste.
文摘Paratungstate-loaded titania catalysts were prepared %via% the addition of a series of aqueous solutions of paratungstate(denoted as W_ 7) into an isopropanol solution of Ti[OCH(CH_ 3)_ 2]_ 4 by means of the sol-gel method. The catalysts were characterized by EDX, BET, FTIR, UV-Vis DRS, XRD and the results indicate that such paratungstate-loaded catalysts maintained their heptatungstate structure in the anatase titania matrix up to 400 ℃. The catalysts were tested for the heterogeneous photodegradation of chlorobenzene in aqueous media and showed a better catalytic activity than P-25 TiO_ 2 because paratungstate can prevent the recombination of the holes and electrons produced during irradiation. Moreover, the paratungstate-loaded titania catalysts can resist the disaggregation during the photoirradiation and can be easily recycled from the aqueous suspensions after reactions.
文摘Well-organized mesoporous titania particles and thin films were successfully synthesized by using tetrabutyl titanate as the inorganic precursor and triblock copolymer (Pluronic P123) as the template via evaporationinduced self-assembly process. The resulting materials were characterized by high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD). Fourier-transform infrared spectroscopy (FT-IR),Brunauer-Emmett-Teller (BET) and atomic force microscopy (AFM). Macro shape of mesoporous titania would greatly influence the mesostructure of materials, and the probable reasons were also discussed.