Preparation and characterization of visible-light-driven TiO2 photocatalyst Co-doped with nitrogen and erbium

A series of nitrogen and erbium co-doped TiO2 photocatalyst was prepared by sol-hydrothermal method. The structure and properties of the photocatalyst were characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) method, X-ray photoelectron spectroscopy (XPS), and UV-vis diffuse reflectance spectra (DRS). The XRD and BET results showed that co-doping inhibited the increase of crystallite size and enlarged specific surface areas. XPS spectroscopy indicated nitrogen atoms were incorporated into TiO2 lattice, and erbium atoms mostly existed in the forms of Er2O3. A shift of the absorption edge to the lower energy and four absorption bands located at 654, 544, 524 and 489 nm attributed to the 4f transitions of 4I15/2 --> 4F2/9, 4I15/2 --> 4S3/2, 4I15/2 --> 2H11/2, 4I15/2 --> 4F7/2 of Er3+ were observed using DRS spectroscopy. The catalytic efficency was evaluated by the photocatalytic degradation of methyl orange (MO) under visible light irradiation. The results showed that the photocatalytic performance of the co-doped TiO2 was related with the hydrothermal temperature and the molar ratio of N/Ti, and they showed higher acitivites than pure TiO2. Results determined by fluorescence technique revealed that irradiation (lambda > 400 nm) of TiO2 photocatalyst dispersed in MO solution induces the generation of the highly active hydroxyl radicals (OH). It indicated the photocatalytic activities of TiO2 photocatalyst were correlation with the formation rate of hydroxyl radicals (OH) and other active oxygen species.     

Photoinduced hydroxyl radical and photocatalytic activity of samarium-doped TiO(2) nanocrystalline

Sm(3+)-doped TiO(2) nanocrystalline has been prepared by sol-gel auto-combustion technique and characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) method, and also UV-vis diffuse reflectance spectroscopy (DRS). These Sm(3+)-doped TiO(2) samples were tested for methylene blue (MB) decomposition and *OH radical formation. The analysis of *OH radical formation on the sample surface under UV irradiation was performed by fluorescence technique with using terephthalic acid, which readily reacted with *OH radical to produce highly fluorescent product, 2-hydroxyterephthalic acid. It was observed that the presence of Sm(3+) ion as a dopant significantly enhanced the photocatalytic activity for MB degradation under UV light irradiation because both the larger specific surface area and the greater the formation rate of *OH radical were simultaneously obtained for Sm(3+)-doped TiO(2) nanocrystalline. The adsorption experimental demonstrated that Sm(3+)-TiO(2) had a higher MB adsorption capacity than undoped TiO(2) and the adsorption capacity of MB increased with the increase of samarium ion content. The results also indicated that the greater the formation rate of *OH radical was, the higher photocatalytic activity was achieved. In this study, the optimum amount of Sm(3+) doping was 0.5 mol%, at which the recombination of photo-induced electrons and holes could be effectively inhibited, the highest formation rate of *OH radicals was, and thereby the highest photocatalytic activity was achieved.     

The properties of upconversion luminescence on YAIO3:Er(3+) nanophosphors with different Er(3+) concentrations

We report the properties of upconversion luminescence on Yttrium aluminum perovoskite (YAIO3) doped with trivalent erbium at concentrations of 1, 2, 3, 5 and 7 mol%. The samples were synthesized by solvo-thermal reaction method and the XRD patterns conforms that the YAP:Er(3+) nanophosphors have orthorhombic phase. Efficient green and red upconversion (UC) emission of YAP:Er(3+) nanophosphors was measured under the excitation of 975 nm continuous wave diode laser, and its dynamics and pump power dependence were investigated. As concentration of Er(3+) ion increased from 1 to 7 mol%, the red UC emission increased more rapidly. It is attributed to the energy transfer (4I(11/2) --> 4I(15/2):4I(13/2) --> 4F(9/2)) and to the cross relaxation (4S(3/2) --> 4I(9/2):4I(15/2) --> 4I(13/2)) between Er(3+) ions. In this case, the green and red emissions were yielding from quadratic to linear. These conclusions obtained are confirmed by theoretical investigations based on steady-state rate equations.     

Photocatalytic degradation of monocrotophos pesticide--an endocrine disruptor by magnesium doped titania

Mg-doped TiO(2) with different Mg concentrations were prepared using sol-gel method and characterized by XRD, UV-visible, XPS, SEM and FT-IR. The XRD results revealed that Mg(2+) goes into the TiO(2) lattice. SEM images of the doped and pure TiO(2) indicated that there is a smaller particle size for the doped catalyst compared to that of the pure TiO(2). UV-visible absorption spectra indicated that upon doping with Mg(2+) ion, the catalyst exhibits absorption in visible region. FT-IR and XPS spectra demonstrated that the presence of Mg(2+) ion in the TiO(2) lattice as substitutional dopant. Photocatalytic activity of doped TiO(2) has been evaluated by degradation of the monocrotophos (MCP) pesticide. The effect of solution pH, catalyst dosage and initial concentration of MCP on the photocatalytic activity of Mg-doped TiO(2) with different loadings was studied. It was observed that the rate of degradation of MCP over Mg-doped TiO(2) is better than Pure TiO(2) and Degussa P-25.     

Effect of collector speed and flow rate on morphology of Er doped TiO2 nanofibers

The 0.5 mol% Er3+ doped TiO2 (Er(3+)-TiO2) nanofibers were synthesized by a sol-gel derived electrospinning and subsequent calcination for 3 h at 500 degrees C in air. The calcined fibers were examined to evaluate the effect of collector speed and flow rate on morphology of the fibers. The dynamic viscosity and surface tension of precursor solution were 34 cP and 22.7 mN/m, respectively. The Er(3+)-TiO2 nanofibers were electrospun horizontally on the drum rotated at 100-500 rpm and flow rate of 0.2-0.5 mL/h under a DC voltage of 10 kV. The grounded collector is a stainless mandrel placed 12 cm away from the tip of the needle. Beads were observed for the nanofibers prepared at flow rates from 0.2 mL/h to 0.5 mL/h when the collector speed was 100 rpm. The nanofibers increased in diameter slightly from 150 nm to 190 nm as the flow rate was raised from 0.2 mLh to 0.5 mL/h. No beads were found at the collector speed of above 300 rpm when the flow rate was 0.2 mL/h. The optimized flow rate and collector speed of the nanofibers were determined to be in the range of 0.2-0.3 mL/h and 300-400 rpm, respectively. Uniform, smooth and continuous fibers with diameters of 150 to 170 nm were detected. Crystallite size determined by the Scherrer formula was about 6 nm. It can be concluded that the collector speed and the flow rate are influential on the morphology of the Er(3+)-TiO2 nanofibers. The Er(3+)-TiO2 nanofibers, prepared at 0.2 mL/h and 300 rpm, had typical absorption peaks located at 490, 523 and 654 nm, corresponding to the transitions from 4I15/2 to 4F7/2, 2H11/2 and 4F9/2, respectively. The Er(3+)-TiO2 nanofibers showed enhanced photoresponses under visible light.     

WO_3-TiO_2纳米材料的制备及其光催化性能

采用溶胶-凝胶法制备WO3-TiO2纳米复合材料,并用透射电镜和X射线衍射对所制备材料进行表征和分析。以WO3-TiO2纳米材料为光催化剂对甲基橙进行光催化降解处理,研究WO3的掺杂量、煅烧温度、光照时间等因素对甲基橙降解率的影响。结果表明:在紫外灯照射下,使用w(WO3)=3%、550℃下煅烧得到的WO3-TiO2纳米复合粉体0.02 g,甲基橙溶液20 mL(ρ=5 mg/L,pH=4),光催化3 h后,甲基橙降解率达到94.93%。     

Photodegradation of methyl orange by photocatalyst of CNTs/P-TiO(2) under UV and visible-light irradiation

A novel nanoscale photocatalyst CNTs/P-TiO(2) was successfully prepared by hydrothermal method. The morphology and the physicochemical properties of the prepared samples were investigated using TEM, XPS, XRD, BET, FTIR, TG-DSC and UV-vis DRS spectroscopy. The photocatalytic activity was evaluated by degradation of methyl orange (MO) dye. The results demonstrated that CNTs/P-TiO(2) nanoparticles could effectively photodegrade MO not only under UV irradiation but also under visible-light (VL) irradiation. The MO degradation performance on CNTs/P-TiO(2) was superior to that of the commercial P25. The optimal mass ratio of CNTs to P-TiO(2) in the nanocomposite catalyst was 5:100. The synergetic effect was discussed in terms of different roles played by phosphorus doping and introducing CNTs into the composite catalysts.     

(Bi, C and N) codoped TiO2 nanoparticles

Bi, C and N codoped TiO2 photocatalysts were prepared by doping TiO2 with BiCl3 and KSCN in a sol-gel process (denoted as (Bi,SCN)-TiO2). The catalyst samples were then characterized by XRD, TEM, diffuse reflectance spectra (DRS), XPS, FT-IR and N2 sorption. Bi, C and N elements were detected both by XPS and elemental analysis, while S element was not found, suggesting that SCN- group may have decomposed during the sol-gel process. The effects of the doping on the properties and photocatalytic activity of the TiO2 were investigated. It was found that the cation and the anion affected the properties of TiO2 differently. The optical absorption onset of TiO2 red shifted in the presence of Bi3+, while long tail occurred in the presence of SCN-. The order of photoreactivity for TiO2 samples was as follow: (Bi,SCN)-TiO2>Bi-TiO2>undoped TiO2>p25 TiO2, whatever under UV or visible light illumination. The high photoreactivity of the doped TiO2 was also discussed.     

A visible light response TiO2 photocatalyst realized by cationic S-doping and its application for phenol degradation

S-doped TiO2 photocatalyst with high visible light activity was prepared by acid catalyzed hydrolysis method using thiourea (TU) as sulfur source. The catalyst was characterized by DRS, XPS, XRD, FTIR, SEM and N2 adsorption. It was found that cation S6+ was homogeneously incorporated into the bulk phase of TiO2 and substitutes for some of the lattice titanium (Ti4+). Doped S can form a new band above the valence band and narrow the band-gap of the photocatalyst, giving rise to a second absorption edge in the visible light region. The activity of the catalyst was examined by photodegradation of phenol in aqueous solution under both artificial visible light and solar light irradiation. The activity of catalyst was found to be dependent on the doping amount of S and the maximum activity was observed when the catalyst was obtained by calcinated at 600 degrees C with the mass ratio of TU/TiO2=1. Too much of new-generated band-gap structures due to higher S-doping could act as recombination centers for electron-hole pairs. Catalyst with optimum S-doping exhibited the highest activity under both artificial light and solar irradiation for phenol degradation. In addition, doped S also beneficial for the better dispersion, large S(BET) and phase transformation retardation of TiO2.     

Catalytic wet air oxidation of phenol over CeO2-TiO2 catalyst in the batch reactor and the packed-bed reactor

CeO2-TiO2 catalysts are prepared by coprecipitation method, and the activity and stability in the catalytic wet air oxidation (CWAO) of phenol are investigated in a batch reactor and packed-bed reactor. CeO2-TiO2 mixed oxides show the higher activity than pure CeO2 and TiO2, and CeO2-TiO2 1/1 catalyst displays the highest activity in the CWAO of phenol. In a batch reactor, COD and TOC removals are about 100% and 77% after 120 min in the CWAO of phenol over CeO2-TiO2 1/1 catalyst at reaction temperature of 150 degrees C, the total pressure of 3 MPa, phenol concentration of 1000 mg/L, and catalyst dosage of 4 g/L. In a packed-bed reactor using CeO2-TiO2 1/1 particle catalyst, over 91% COD and 80% TOC removals are obtained at the reaction temperature of 140 degrees C, the air total pressure of 3.5 MPa, the phenol concentration of 1000 mg/L for 100 h continue reaction. Leaching of metal ions of CeO2-TiO2 1/1 particle catalyst is very low during the continuous reaction. CeO2-TiO2 1/1 catalyst exhibits the excellent activity and stability in the CWAO of phenol.     

Absorption and emission cross sections of Er(3+) in Al(2)O(3) waveguides

Al(2)O(3) slab waveguide films were doped with erbium using ion implantation to a peak concentration of 1.5 at. %. Prism coupling measurements show absorption caused by (4)I (15/2) ?(4)I (13/2) intra-4f transitions in Er(3+) with a maximum at 1.530 mum of 8 dB/cm. The Er(3+) absorption cross section is determined as a function of wavelength. We used the McCumber theory to derive the emission cross section spectrum from the absorption results, which we then compared with the Er(3+) photoluminescence spectrum. The peak absorption and emission cross sections are found to be 6 x 10(-21) cm(-2). The results are used to predict the optical gain performance of an Er-doped Al(2)O(3) optical amplifier that operates around 1.5 mum.     

Photocatalytic degradation of Direct Red 23 dye using UV/TiO2: Effect of operational parameters

In this study, the photocatalytic degradation of Direct Red 23 (Scarlet F-4BS) was investigated in UV/TiO2 system. The effect of catalyst loading and pH on the reaction rate was ascertained and optimum conditions for maximum degradation were determined. The results obtained showed that acidic pH is proper for the photocatalytic removal of Direct Red 23. In addition, the effects of several cations (Cu2+, Al3+, Cr3+, and Sn4+) and anions (BiO3(-), SO4(2-), and CN(-)) and C2H5OH were examined in this photocatalytic process. On the order hand, three types of catalysts (Fe2O3, SnO2, and ZnO) were compared with TiO2. After 90 min reaction, the relative decomposition order established was UV/TiO2>UV/SnO2>UV/Fe2O3>UV/ZnO.     

超临界流体干燥法制备TiO2/ Fe2O3 和TiO2/ Fe2O3/ SiO2 复合纳米粒子及光催化性能

以TiCl₄ 、Fe (NO₃ )₃·9H₂O 和Na₂SiO₃19H₂O 为原料, 采用溶胶凝胶法结合超临界流体干燥法(SCFD)制备了纳米级TiO₂/ Fe₂O₃ 和TiO₂/ Fe₂O₃/ SiO₂ 复合光催化剂。以光催化降解苯酚对所得催化剂的催化活性进行了评价。结果表明, 纳米TiO₂/ Fe₂O₃ 复合粒子与单组分TiO₂ 比较, 复合粒子光催化活性高于单组分的TiO₂, 6h 苯酚降解率高达95.9 %。SiO₂ 的加入可以抑制纳米粒子粒径的长大和晶相的转变, 增强TiO₂ 纳米粒子的热稳定性。复合光催化剂中Fe₂O₃ 最佳掺入量为0.06 %, SiO₂ 最佳掺入量为10 %(摩尔分数) 。并用XRD、TEM 和FTIR 等手段进行了表征。TiO₂ 以锐钛矿型形式存在, SiO₂ 以无定性形式存在。比较了不同制备方法制得的TiO₂/ Fe₂O₃ 复合光催化剂, 得出超临界干燥法制备的光催化剂具有粒径小、比表面积大、分散性好、光催化活性高等特点。采用超临界流体干燥可直接得锐钛型纳米复合光催化剂。     

Synthesis and characterization of Zr4+, La3+ and Ce3+ doped mesoporous TiO2: evaluation of their photocatalytic activity

Sol-gel method was used to synthesize Zr(4+), La(3+) and Ce(3+) doped mesoporous TiO(2) materials with different weight percentage (0.5, 1.0, 2.0 and 3.0 wt%) using triblock copolymer as the structure directing template in ethanol/water medium. Characterization revealed the isomorphic substitution of Zr(4+) ion into the lattice of TiO(2), and surface binding nature of La(3+) and Ce(3+) ions on mesoporous TiO(2). Microscopic examination confirmed the surface adsorption of foreign ion which could alter the particle morphology. The size of the particles was less than 20 nm. Photocatalytic activity of metal ions doped mesoporous TiO(2) was evaluated using aqueous alachlor as a model pollutant. It was found that 1 wt% Ce(3+) doped mesoporous TiO(2) exhibited higher activity than pure and other metal ions doped mesoporous TiO(2). The change of oxidation state of Ce(3+) is suggested to be the cause for enhanced photocatalytic activity.     

TiO_2-Al_2O_3负载型催化剂的制备及其光催化性能

以钛酸四丁酯和氢氧化钠为反应物,采用两步水热法制备TiO2纳米线,并将其原位负载于Al2O3载体上,研究它们对甲基橙的光催化降解性能。结果表明,锐钛矿相TiO2主要呈纳米线和八面体状负载在Al2O3载体上,当TiO2负载质量分数为30%,焙烧温度为400℃,催化剂用量为1.332 0 g/L时,TiO2-Al2O3负载型催化剂光催化降解甲基橙的性能最佳,光照5 h后,甲基橙在紫外和太阳光下的降解率分别达到58.9%和55.6%。相同实验条件下,TiO2-Al2O3负载型催化剂对甲基橙的降解率比单纯TiO2提高了35.1%。     

掺铒铋基玻璃的荧光俘获和浓度猝灭效应研究

用高温熔融法制备了系列掺铒铋硼锗酸盐玻璃,测试分析了不同铒离子掺杂浓度下玻璃样品的吸收光谱和荧光光谱.结果显示,掺铒铋硼锗酸盐玻璃中存在着强烈的荧光俘获和浓度猝灭效应.随着铒离子掺杂浓度的增加,1.53 μm波段荧光谱展宽,1 560 nm波长处荧光次峰相对增强.对此用一个等效的四能级模型予以了定性分析.同时,随着铒离子掺杂浓度的增加,4I13/2能级荧光寿命和1.53 μm波段荧光强度呈现出先增加后减小趋势.依据Dexter能量转移理论,计算了该玻璃系统中铒离子发生浓度猝灭的临界距离R0及相互作用参数CEr-Er,并与其它玻璃基质进行了比较.     

Fluorescence dynamics and rate equation analysis in Er3+ and Yb3+ doped double tungstates

The fluorescence dynamics in Er3+ and Yb3+ doped KGd(WO4)2 and KY(WO4)2 has been investigated. Lifetimes have been measured for the Yb (2F(5/2)), Er (4I(13/2)), and Er (4S(3/2)) levels around 1, 1.5, and 0.55 microm, respectively. The Yb (2F(5/2)) lifetimes show a decreasing trend toward the limiting Er (4I(11/2)) lifetime with increasing Er-to-Yb concentration ratio, whereas the Er (4I(13/2)) lifetimes are mostly unaffected by the doping concentrations. A rate equation analysis has been performed to explain the observed behavior and gain is calculated for a continuous-wave laser at 1.53 microm to find the optimum doping concentrations for high gain.     

Study on photocatalytic performance and degradation kinetics of X-3B with lanthanide-modified titanium dioxide under solar and UV illumination

The present work was focused on photocatalytic oxidation of the model molecule reactive brilliant X-3B by lanthanide-modified TiO(2) samples under artificial solar and UV irradiation. Experimental results showed that the TiO(2) samples doping with lanthanide (Ce and Gd) could greatly enhance the activity of pure TiO(2), and could extend the absorption range to visible region. The optimum doping amount was 0.2 and 0.5at.% for Ce- and Gd-doped TiO(2) particles, respectively. The degradation kinetics of X-3B on Ce-doped TiO(2), Gd-doped TiO(2), and pure TiO(2) were studied as well. The results exhibited that the degradation of X-3B on all the samples were in accordance with the first-order model. The trend of apparent reaction rate constants k(app) was as follows, Gd-doped TiO(2)>Ce-doped TiO(2)>pure TiO(2), under solar illumination. Scatchard plot analysis was used to evaluate the adsorption phenomena of as-prepared samples, and it indicated that lanthanide doping can improve the efficiency of interfacial adsorption of TiO(2) samples. The trend was the same as that of photocatalytic activity.     

湿法碳氮硫共掺杂TiO2的制备及其光催化活性

以全硫碳酸铵为掺杂剂,采用湿法由硫酸钛出发制得碳氮硫共掺杂TiO2,通过XRD和XPS对掺杂TiO2进行了表征,并对掺杂TiO2的光催化活性进行了考察。结果表明,微波辅助加热制备的掺杂TiO2中,C元素部分替位取代了TiO2晶格中的Ti 4+;N元素以两种掺杂形式存在,即进入TiO2晶格替位取代O2-产生掺杂和通过化学吸附进入晶格间隙产生掺杂;S元素主要提供S 2p形成S6+取代Ti 4+进入晶格进行掺杂;以甲基橙溶液为对象进行光催化降解,当掺杂量α为1.6、500℃焙烧2h时,掺杂TiO2表现出较高的可见光催化活性,光照70min使浓度为20mg/L的甲基橙溶液的降解率达到99.64%,明显提高了纳米TiO2的光催化活性。     

Preparation of re-usable photocatalytic filter for degradation of Malachite Green dye under UV and vis-irradiation

Sn(4+) doped and undoped nano-TiO(2) particles easily dispersed in water were synthesized without using organic solvent by hydrothermal process. Nanostructure-TiO(2) based thin films were prepared on flyswatter substrate, made with stainless steel, by dip-coating technique. The structure, surface and optical properties of the particles and thin films were characterized by element analysis and XRD, BET, SEM and UV/vis/NIR techniques. The photocatalytic performance of the films were tested for degradation of Malachite Green dye in solution under UV and vis-lights. The results showed that the coated flyswatter has a very high photocatalytic performance for the photodegradation of Malachite Green irradiated with UV and vis-lights. The results also proved that the hydrothermally synthesized nano-TiO(2) particles are fully anatase crystalline form and are easily dispersed in water, the coated surfaces are hydrophilic, and the doping of transition metal ion efficiently improved the degradation performance of TiO(2)-coated flyswatter. The photocatalytic performances determined at both irradiation conditions were very good and were almost similar to each other for Sn(4+) doped TiO(2)-coated flyswatter and it can be repeatedly used with increasing photocatalytic activity compared to undoped TiO(2)-coated flyswatter.