Fe3+掺杂纳米TiO2的表征及其光催化性能的研究

[目的]提高TiO2的可见光响应和光催化活性.[方法]采用溶胶凝胶法制备掺铁纳米TiO2粉体,进而研究掺铁TiO2的光催化活性.[结果]450 ℃煅烧后掺铁TiO2出现了很明显的TiO2特征衍射峰,且峰形尖锐,结晶良好,均没有出现铁的掺杂新相.随着掺铁量的提高,TiO2的粒径逐渐减小,当掺杂量为0.4%时,TiO2的粒径最小,减少至纯TiO2的45%.掺铁抑制了锐钛矿向金红石矿的转变.随着焙烧温度的升高,TiO2的粒径逐渐增大.用溶胶-凝胶法制备的TiO2均为纳米级,基本成球形颗粒.纯TiO2粒子分布不是很均匀,团聚现象明显;掺铁TiO2颗粒分布均匀,没有明显的团聚现象;掺铁使TiO2在紫外灯和太阳光下的降解性能都有着不同程度的提高.[结论]溶胶-凝胶法制备的掺铁纳米TiO2细化了晶体晶粒,抑制了锐钛矿向金红石矿的转变.     

银掺杂二氧化钛及其光催化性能研究

采用溶胶-凝胶法制备银掺杂二氧化钛光催化剂,通过XRD、SEM、FT-IR、TG-DSC 和UV-Vis等技术对其进行表征.以甲基橙为模拟污染物,考察催化剂的光催化活性,探讨煅烧温度和银掺杂量对光催化效率的影响.实验结果表明：银掺杂二氧化钛提高了二氧化钛在紫外光和可见光下的光催化活性;当Ag掺杂量为1.00%、煅烧温度为450℃、催化剂用量为0.05 g时,银掺杂二氧化钛光催化剂在可见光条件下降解4 h 后,降解率达到92.57%,是纯二氧化钛的4.51倍;紫外光条件下降解2 h达到84.54%,是纯二氧化钛的2.27倍.     

可见光下掺N附Ag纳米TiO_2的光催化降解甲基橙

采用溶胶–凝胶法制备纯TiO_2和掺氮TiO_2纳米颗粒(N-TiO_2),然后通过光催化还原在其表面附Ag,得到表面附Ag的纳米TiO_2(即Ag/TiO_2)和掺N附Ag纳米TiO_2(即Ag/N-TiO_2),利用X射线衍射(XRD)、场发射扫描电镜(FE-SEM)、光致发光光谱仪(photoluminescence spectroscopy,PL)、X射线光电子能谱(XPS)以及紫外可见漫反射光谱分析(UV-VIS DRS)对TiO_2及其掺杂改性后的组成和结构、光吸收性能以及可见光下对甲基橙溶液的光催化活性等进行表征。结果表明,所有样品均为锐钛矿型,Ag/TiO_2的平均晶粒度为20.4 nm;N以替代型N-Ti-O、间隙型Ti-O-N(或氧化态Ti-O-N-O)的形式存在于晶格中,银以Ag0形式附着在TiO_2表面;N掺杂抑制TiO_2晶粒的生长,并抑制光生电子与空穴的复合,从而促进TiO_2对可见光的吸收;表面附Ag对TiO_2晶格没有明显影响,但在450~580 nm可见光区产生强烈的表面等离子吸收带并延长至近红外区。TiO_2及其掺杂改性后对甲基橙的光催化效果为Ag/N-TiO_2Ag/TiO_2N-TiO_2TiO_2(或Degussa P25),Ag/N-TiO_2在可见光下对甲基橙(p H=3)进行光催化降解,150 min时降解率达到95%。     

Er3+∶YAlO3/Fe掺杂TiO2复合物的制备及光催化活性研究

对TiO2半导体材料进行改性,分别通过溶胶凝胶、超声波分散和溶液沸腾的方法合成了Er3+∶YAlO3/Fe掺杂TiO2复合物光催化剂,并且采用XRD和SEM进行表征,研究了各种因素在太阳光照射下降解酸性红B的催化活性,也考察了Er3+∶YAlO3的包覆量、Er3+∶YAlO3/Fe掺杂TiO2的量、太阳光照射时间、酸性红B的初始浓度和氯化钠浓度等其降解过程用UV-Vis光谱进行检测。实验结果表明,加入上转光剂之后降解率大幅度增加,改性后的光催化剂可以有效地降解染料废水。     

铈掺杂TiO2光催化降解甲基橙的研究

采用溶胶-凝胶法制备纯的及掺杂不同量Ce的TiO2纳米粒子,利用UV-Vis漫反射光谱及XRD等对所制备样品进行表征和解释,以高压汞灯为光源,甲基橙水溶液的脱色为模型反应,研究了CeO2/TiO2的光催化降解反应活性.实验发现掺杂Ce的TiO2纳米粒子反射光谱特性向可见光方向红移到了500 nm;掺杂Ce的TiO2纳米粒子比纯的TiO2纳米粒子对光的吸收率高、吸收能力强;掺杂的Ce4+仅有少量进入TiO2晶格中,而大部分的Ce4+没有进入TiO2晶格中,而是以小团簇的CeO2形态均匀地分散在TiO2纳米粒子中或者是覆盖在其表面上,说明掺杂Ce能提高TiO2光催化反应活性,且掺杂Ce量有最佳值.实验结果表明在TiO2中掺杂Ce的摩尔百分含量为2%,甲基橙起始浓度为20 mg·L-1,CeO2/TiO2用量为0.400 g,双氧水用量为5.88 mmol·L-1,pH值为6.4时,光照8 h,甲基橙的脱色率可达96.8%.     

Ag^＋掺杂TiO2纳米粉体制备及光催化性能研究

以钛酸四丁酯为原料,利用溶胶凝胶法制备Ag 掺杂TiO2纳米粉体,采用正交实验考察了掺杂量、浓硝酸、冰醋酸、煅烧温度等因素对其制备的影响,从而确定制备工艺最佳条件.通过XRD、TEM、TG-DSC等测试技术对掺杂纳米TiO2粉体进行表征.最佳工艺条件为:掺Ag 量0.5 %(摩尔分数),冰醋酸1mL,浓硝酸0.2mL,煅烧温度450℃,制得颗粒粒径为12.16nm.以甲基橙为降解物,通过自制光催化反应装置,研究了光催化剂的活性,结果表明:Ag 掺杂制备的TiO2纳米粉体具有较高的光催化活性,试验条件下Ag 掺杂TiO2纳米粉体最高降解率为79.38%.     

Fe^3＋／Ce^3＋掺杂纳米TiO2的制备及光催化性能研究

采用溶胶-凝胶法制备了不同粒径的纯纳米TiO2和掺杂Fe^3＋和Ce^3＋的纳米TiO2。样品的X射线衍射（XRD）和透射电镜（TEM）表征说明：在相同的制备条件下，掺杂可以减小粒子粒径，掺Fe^3＋和Ce^3＋可以抑制晶相转变。光催化降解NO2的结果表明，在相同的制备方法和掺杂量的条件下合成的光催化剂对亚硝酸盐的降解率由高到低的顺序为：掺铁TiO2〉掺铈TiO2〉TiO2。     

镧、银离子掺杂对TiO_2光催化活性的影响

以钛酸四丁酯为原料,采用溶胶-凝胶法制备了纯的TiO2纳米粒子和掺杂镧、银离子并且浓度分别为2%,5%的TiO2纳米粒子。利用XRD和UV-VIS对其进行表征,且在日光条件下,以甲基橙的光催化降解为模型反应,考察了纯的TiO2纳米粒子及不同镧、银离子掺杂浓度下的TiO2纳米粒子光催化活性。结果表明,在掺杂镧、银离子后,TiO2的本征吸收光谱比未经掺杂的出现不同程度的红移,在氧化剂的协同作用下使得甲基橙的降解效率有明显提高。     

钇掺杂TiO2/膨润土纳米复合光催化剂的性能研究

以膨润土为载体,钛酸四丁酯和氯化钇为原料,采用溶胶-凝胶法制备钇掺杂TiO2/膨润土纳米复合光催化剂,运用X射线衍射(XRD)、差热-热重(DTA-TG)和红外光谱(IR)对纳米复合光催化剂进行了表征,在太阳光照射下,通过染料酸性红B的降解反应,考察其光催化活性。实验结果表明:钇掺杂TiO2已进入膨润土层间,经500℃热处理后,在膨润土表面有锐钛矿型TiO2生成,并结合牢固;适量的钇掺杂降低了TiO2粒子的粒径,显著提高了光催化降解有机物的活性;随着光照时间的延长,染料酸性红B的特征峰510nm强度逐渐减弱,2h后彻底消失,酸性红B的去除率达97.38%。     

掺杂镨的纳米二氧化钛光催化降解2,4-二硝基苯酚的研究

以钛酸丁酯为原料,用溶胶-凝胶(Sol-gel)法制备了掺杂镨的纳米TiO2粉末.采用X光衍射仪对粉体的物相进行了表征.样品经500℃焙烧2h后,0.5%(摩尔分数,下同)Pr3+-TiO2纳米粉末为单一的锐钛型结构.通过粉体对2,4-二硝基苯酚的降解情况对其光催化活性进行了测试,结果表明与纯TiO2相比,Pr3+-TiO2的光催化活性有较大提高,当Pr3+的掺入量为0.5%时催化活性最高.以高压汞灯为光源,2,4-二硝基苯酚的初始浓度为50mg·L-1、催化剂0.5%Pr3+-TiO2投加量为1.0 g·L-1时,2,4-二硝基苯酚的光催化降解效果最好.     

金属离子掺杂对离子液辅助制备纳米TiO_2性能的影响

以过渡金属(Cr、Fe、Ni和Zn)掺杂为手段,以溶胶凝胶为制备方法,以离子液2—羟基咪唑甲酸盐为微观结构调控试剂,制备了TiO_2纳米粒子。将样品备好后,在500℃的条件下进行煅烧处理,用BET、XRD、DRS等手段进行结构表征,以酸性蓝92为模拟污染物对其光催化性能进行测定。研究结果表明,经过渡金属掺杂后的TiO_2纳米颗粒比纯TiO_2具有更高的比表面积和更小的粒径尺寸。过渡金属的掺杂使TiO_2的吸收光谱向可见光的方向移动。在紫外灯照射下,水溶液中酸性蓝92的光降解结果为:过渡金属离子的存在使TiO_2纳米颗粒的光催化活性得到了明显增强。     

Can lanthanum doping enhance catalytic performance of silver in direct propylene epoxidation over NaMoAg/SiO_2?

In the attempt to reduce surface free energy of silica to improve interaction of silica with silver, silica was doped by different amounts of low surface energy lanthanum, La_2O_3, through impregnation. The doped and undoped silica were used as supports for preparation of Na/Ag/Mo/La_2O_3-SiO_2 catalysts. Catalytic performances of the catalysts were evaluated in direct epoxidation of propylene(DPO) using molecular oxygen under atmospheric pressure and without adding hydrogen. Adding 5 wt%La to the Na/Ag/Mo/SiO_2 catalyst improves both the catalysts electivity in DPO and its stability over 20h of time-on-stream.The characterization results show that La_2O_3 species interact strongly with silver particles on the silica surface which result in significant improvement in the dispersion profile of silver and marked decrease in the size of silver nanoparticles(AgNPs). The estimated mean diameter of AgNPs is ca. 4.0 nm in Na/Ag/Mo/5 wt%La_2O_3-SiO_2, which is smaller than that(53.9 nm) found in Na/Ag/SiO_2. The presence of subnanometer AgNPs on Ag/La_2O_3-SiO_2 prior addition of MoO_3 and NaCl to the sample can enhance the mutual electronic synergism between Ag, MoO_3 and Na for selective production of propylene oxide.     

Role of Reactive Oxygen Species in Determining Nitrification Inhibition by Metallic/Oxide Nanoparticles

The toxicity of several metallic/oxide nanoparticles (TiO2, CuO, ZnO, and Ag) to nitrifying bacteria was evaluated individually or in combination in batch studies. Except for the mixture of ZnO and Ag, the mixture inhibition of nanoparticles was roughly the sum of individual inhibition among the nanoparticles studied. Although there was no inhibitory effect of TiO2 nanoparticles under ambient light or dark conditions, nitrification inhibition was significantly increased when TiO2 nanoparticles were exposed to ultraviolet (UV) for 30 min. Under UV exposure, both TiO2 nanoparticles (anatase) and bulk amorphous TiO2 generated the same amount of reactive oxygen species (ROS) in the bacterial cell although TiO2 nanoparticles were more toxic than the bulk counterpart. While the inhibition was well correlated to intracellular ROS concentration, the ROS correlations were different for the different forms of TiO2 or for the different nanoparticles (e.g., Ag versus TiO2). ROS is therefore not a good chemical marker to indicate the toxicity of common metallic/oxide nanoparticles.     

Study of erbium (Ⅲ) doped titanium dioxide nanoparticles by photoacoustic spectroscopy

Nanocrystalline titania as photocatalyst has attracted considerable attention for its potential use in environmental cleaning.Recently,lanthanide ions doped titania samples have been shown to increase the photocatalytic efficiency of selected reactions.In this work,TiO2 nanoparticles doped with Er3+ were prepared via an ultrasonic assisted sol-gel method.The optical properties of the samples were determined by photoacoustic(PA) spectroscopy.It was found that the absorption edge shifted to lower wavelength w...     

Photoluminescence Characteristics of Gd2Mo3O9 ： Eu Phosphor Particles by Solid State Reaction Method

Eu^3＋-doped Gd2Mo3O9 was prepared by solid-state reaction method using Na2CO3 as flux and characterized by powder X-ray diffractometry. According to X-ray diffraction, this material belonged to a tetragonal system with space group I41/α. The effects of flux content and sintering temperature on the luminescent properties were investigated with the emission and excitation spectra. The results showed that flux content and sintering temperature had effects on the luminescent properties, the optimized flux content and the best temperature was 3 % and 800 ℃ respectively. The excitation and emission spectra also showed that this phosphor could be effectively excited by C-T band （280 nm）, ultraviolet light 395 nm and blue light 465 nm. The wavelengths at 395 and 465 nm were nicely fitting in with the widely applied output wavelengths of ultraviolet or blue LED chips. Integrated emission intensity of Gd2Mo3O9 ： Eu was twice higher than that of Y2O2S ： Eu^3 ＋ under 395 nm excitation. The Eu^3＋ doped Gd2Mo309 phosphor may be a better candidate in solid-state lighting applications.     

Luminescence properties of Eu3＋ and Ho3＋ in SreTiO4

Eu3+ and Ho3+ doped Sr2TiO4 were synthesized by using solid-state reactions. Samples sintered at 1300 oC for 6 h could be indexed to Sr2TiO4 with a single phase. Eu3+ in Sr2TiO4 emitted orange light under the excitation at 365 nm in a broad band which was coupled well with the strongest emission of high pressure mercury vapor lamps. Ho3+ in Sr2TiO4 emitted yellow light under blue excitation from 450 to 460 nm which agreed well with the emission of blue InGaN-based light-emitting diodes. The present results indicated that Sr2TiO4 was a promising host for high pressure mercury vapor lamps or white light-emitting diodes.     

Synergistic Effect of N and Ni2+ on Nanotitania in Photocatalytic Reduction of CO2

Nitrogen and nickel codoped nanotitania (N-Ni/TiO2) photocatalysts for producing methanol by photocatalytic reduction of CO2 were prepared by an improved sol-gol method. The catalysts were characterized by XRD, HRTEM, DES, FTIR, TG-DSC, and UV-Vis, respectively. The experimental results indicated that nano-N-Ni/TiO2 had better properties than the pure nanotitania (TiO2), N doped titania (N/TiO2), and Ni2+ doped titania (Ni/TiO2), considering their performance of photoresponse and photocatalytic reduction of CO2. The methanol yield could reach 482.0μmol/g-cat under optimal conditions. Additionally, the synergetic effect of N and Ni2+ on nano-TiO2 in photocatalytic reduction of CO2 was explained, and the mechanism of photocatalytic reduction CO2 on N-Ni/TiO2 catalyst was proposed.