铁掺杂TiO_2微米带的制备及其光催化性能

采用模板法与溶胶-凝胶法结合,以脱脂棉为模板制备了掺杂Fe3+的TiO2微米带光催化材料.并利用红外光谱(FTIR)、扫描电镜(SEM)、透射电镜(TEM)、X射线衍射(XRD)对掺杂不同比例Fe3+产物的表面形貌及晶型进行了表征.以甲基橙的脱色降解为模式反应,考察了样品的光催化性能.结果表明:以脱脂棉为模板在酸性条件下制备出了宽度5～8μm,厚度约100～500nm的TiO2带状体,此条件下生成的纳米TiO2晶体晶粒直径大小10～30nm,长度100～500nm,呈棒状.且得出当Fe3+掺杂量为0.04%时光催化效果最优,20min对甲基橙的催化效率为91%.     

Ag修饰的Fe_3O_4/TiO_2复合磁性纳米纤维的制备及光催化性能

通过静电纺丝法制备了含有Fe3O4纳米粒子的TiO2纳米纤维,采用水热法对该纤维表面进行纳米Ag修饰,制备出具有较强磁性和较好光催化性能的复合纤维.采用X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)和紫外-可见光谱(UV-Vis)等对样品的结构和形貌进行表征,并以罗丹明B(Rh B)水溶液降解为模型反应,考察样品在紫外光照射下的光催化性能.结果表明,所制备的TiO2为锐钛矿结构,Fe3O4纳米粒子均匀分布在TiO2纤维中,Ag纳米颗粒比较均匀地分散在磁性TiO2纤维表面.经过纳米Ag修饰后,材料的光吸收能力大为增强,吸收带红移并扩展到可见光区.在紫外光照射40 min后,合成样品对Rh B的降解率达到99.5%.此外,Fe3O4纳米粒子的存在使该材料具有较强的磁性,可通过外加磁场将其分离回收.     

层状纳米光催化复合材料H0.8Fe0.8Ti1.2O4/TiO2的合成及性质

用固相合成法制备出K0.8Fe0.8Ti1.2O4,并用离子交换反应制备出H0.8Fe0.8Ti1.2O4;通过C3H7NH2层间膨胀,TiO2粒子的插入和紫外光分解等反应,合成出一种新的层状光催化纳米复合材料-H0.8Fe0.8Ti1.2O4/TiO2.X射线衍射和漫反射等表征结果表明 该样品的层间高度为0.47nm,禁带能隙为2.18和2.88eV.用(>400 nm的光照射30 min,0.4 g样品可使甲基橙溶液(20 mg/L)的降解率达到22.1%.而同样条件下标准TiO2(P-25)仅为6.2%,表明所研制的层状纳米复合材料具有较高的光催化活性.     

聚吡咯敏化磁载TiO_2光催化剂的制备及性能研究

以自制锰锌铁氧体为磁基体,采用乳液分散和原位聚合相结合的方法成功制得了聚吡咯(PPy)敏化磁载TiO2光催化剂(PPy-TiO2/M-Mn0.4Zn0.6Fe2O4),运用傅里叶变换红外光谱(FT-IR)、X射线衍射(XRD)对催化剂的结构进行分析表征,以甲基橙为模拟降解物,对比了不同光照条件下PPy敏化前后TiO2的光响应特性及催化性能,应用重量分析法考察了催化剂的磁回收特性。结果表明:经PPy敏化处理后,PPy-TiO2/M-Mn0.4Zn0.6Fe2O4的光催化响应范围拓宽到435nm,在自然光照射90min后,经PPy敏化的PPy-TiO2/M-Mn0.4Zn0.6Fe2O4对甲基橙的降解率较纯TiO2高29.0%。催化剂经5次使用后,回收率仍可达97%以上,具有良好的回收特性。     

Fe3+掺杂TiO2光催化纤维材料的制备及表征

以棉花纤维为模板制备了一系列Fe3+掺杂的、具有中空纤维结构的TiO2光催化材料(Fe3+/TiO2), 利用热重分析(TG)、扫描电子显微镜(SEM)、X射线衍射(XRD)、zeta电位、红外光谱(IR)和紫外-可见光谱(UV-Vis)等技术对其形貌、晶体结构及表面结构、光吸收特性等进行了表征. 以亚甲基蓝(MB)溶液的脱色降解为模型反应, 考察了不同Fe3+掺杂量的样品在太阳光下的光催化性能. 结果表明, 用模板法制备的Fe3+/TiO2中空纤维结构材料表面存在大量纳米微粒(平均尺寸约12 nm); Fe3+可能均匀分散于锐钛矿结构的TiO2中, 部分取代Ti4+的晶格位置, 既拓宽了TiO2的光谱响应范围, 又形成了TiO2晶体结构的缺陷, 使其表面带负电荷. 在太阳光条件下, 该纤维结构材料较纯TiO2对MB溶液具有更好的光催化脱色降解效果, 且Fe3+的掺入量显著影响该纤维材料的催化性能; 当Fe3+掺杂量为0.15%(w), 在500 ℃焙烧2 h所得中空纤维材料的催化性能最好, 2 h即可使MB溶液的脱色降解率达93%; 重复使用5次仍可使MB溶液的脱色降解率保持在90%以上, 且该催化剂材料易于离心分离去除. 因此, 以该模板合成法, 通过Fe3+的掺杂有望使TiO2成为一种低或无能耗、高活性的绿色环保型催化材料.     

纳米Fe_3O_4及钴离子掺杂Fe_3O_4:有机碱共沉淀制备和磁性质

以有机碱四甲基氢氧化铵(TMAH)为沉淀剂合成了纳米Fe3O4和Co2+掺杂的纳米Fe3O4粒子。分别讨论了碱用量,铁盐溶液浓度,反应温度,有机碱及PEG-4000的分散性等因素对纳米Fe3O4的形貌影响。结果表明,所合成的纳米Fe3O4为30nm左右的反尖晶石型面心立方结构,有机碱除了起沉淀剂作用,还能够提高纳米Fe3O4的分散性。本文还讨论了不同Co2+掺入量的纳米Fe3O4粒子的磁性质,结果表明Co2+掺杂的纳米Fe3O4粒子的矫顽力在不同掺入量的下有较大的改变。当Co2+掺入量为10.0%时,纳米Fe3O4的矫顽力达到最大值,为1628Oe。     

光催化活性二氧化钛溶胶的低温制备与表征

以钛酸丁酯为原料,在70 ℃制备了具有光催化活性的TiO2溶胶.用X射线衍射仪(XRD)和透射电子显微镜(TEM)表征了溶胶结构;用紫外-可见分光光度计研究了TiO2溶胶对甲基橙的吸附和光催化降解性能.XRD图谱表明TiO2溶胶粒子的一次粒径约4 nm,晶型主要为锐钛矿型,并含有少量结晶不完善的板钛矿型;TEM图像表明溶胶中TiO2粒子分散良好,二次粒径约10 nm.吸附实验表明TiO2溶胶使甲基橙溶液褪色约17%;光催化实验表明TiO2溶胶光催化性能优异,自然光催化降解甲基橙溶液(10 mg/L),16min后甲基橙浓度几乎降为0.     

硼硫共掺杂TiO2的光催化性能及掺杂机理

采用水热法制备了硼硫共掺杂的TiO2光催化剂(TiO2-B-S),并用其光催化降解甲基橙.结果表明,在240℃下水热反应12h时制得的TiO2-B-S具有较高的催化活性,紫外光照射50min和太阳光照射230min时对甲基橙的降解率分别达99.8%和81%.X射线粉末衍射、紫外-可见漫反射光谱和X射线光电子能谱等研究表明,TiO2-B-S为锐钛矿晶型,硫硼掺杂能抑制TiO2粒径的生长;TiO2-B-S同时具有较高的紫外光和可见光活性的原因可能是掺杂的硼以B3 进入晶格中,导致TiO2晶格畸变,带隙变窄.掺杂的硼和硫还提高了TiO2的表面酸度和对可见光的吸收.     

La3+-SiO2掺杂纳米TiO2的合成及其光催化降解甲基橙的研究

以三嵌段非离子表面活性剂P123为模板,采用水热法合成了La3+-SiO2掺杂纳米TiO2,通过X射线衍射(XRD)、红外光谱(FT-IR)、紫外-可见漫反射吸收光谱(DRS)等手段,考察了La3+-SiO2掺杂纳米TiO2的结构与光学特性.实验结果表明,La3+和SiO2掺杂使TiO2的晶粒在生长过程中受到阻碍.Ti-O-Si键和Ti-O-La键的形成抑制了金红石相的形成和晶粒长大,提高了TiO2的热稳定性,有利于获得高纯度锐钛矿相纳米TiO2.La3+-SiO2掺杂将TiO2的光响应范围拓宽至可见光区,提高了纳米TiO2的光催化性能.与纯纳米TiO2相比,La3+-SiO2掺杂纳米TiO2光催化降解甲基橙的性能显著提高.     

碳纳米管/TiO_2复合材料的制备及表征研究

采用溶胶-凝胶法和水热合成法,制备出碳纳米管/TiO2(CNTs/TiO2)复合材料。通过X-射线衍射仪(XRD)、扫描电子显微镜(SEM),紫外-可见漫反射光谱(UV-Vis),荧光光谱(LS)检测CNTs/TiO2的晶型及形貌。结果表明:锐钛矿相TiO2纳米颗粒负载在碳纳米管的管壁上,CNTs/TiO2在紫外-可见光波长范围均有较好的吸收性能。在灭菌灯照射下,以甲基橙溶液为降解目标,CNTs/TiO2复合材料对甲基橙溶液的降解有高的光催化活性,180 min内降解率达到85%以上。     

Facile synthesis of ZnS-AgInS2 solid solution nanoparticles for a color-adjustable luminophore

Nanoparticles of ZnS-AgInS2 solid solution (ZAIS) were synthesized by the thermal decomposition of (AgIn)xZn2(1-x)(S2CN(C2H5)2)4 precursors in a hot oleylamine solution. X-ray powder diffraction analyses revealed that the resulting nanoparticle powders were not a mixture of ZnS and AgInS2 but a ZnS-AgInS2 solid solution in which the fraction of ZnS was enlarged with a decrease in the value of x, that is, an increase in the content of Zn2+ in the precursors used. The energy gap of ZAIS nanoparticles could be controlled by the composition of solid solution. Intense emission was observed at room temperature, regardless of the kind of the particles, the peak wavelength of PL being blue-shifted from 720 to 540 nm with a decrease in the value of x. The highest quantum yield of ca. 24% was obtained for nanoparticles prepared with x = 0.86, which was much higher than the quantum yields reported for I-III-VI2-based semiconductor nanoparticles, such as CuInS2 and ZnS-CuInS2 solid solution.     

Preparation of Y2O3:Eu3+ nanoparticles in reverse micellar systems and their photoluminescence properties

Y2O3:Eu3+ phosphor nanoparticles (4-8 nm in size) with spherical morphology and narrow size distribution were obtained by calcination of composite Y-Eu hydroxide nanoparticles, which were prepared in sodium bis(2-ethylhexyl)sulfosuccinate (AOT)/isooctane or polyethylene glycol mono-4-nonylphenyl ether (NP-5)/cyclohexane reverse micellar systems. This was achieved by the incorporation of the Y-Eu hydroxide nanoparticles into polyurea (PUA) via in situ polymerization of hexamethylene diisocyanate (HDI) in the reverse micellar solution and subsequent calcination of the resulting PUA materials. The emission intensity of the Y2O3:Eu3+ nanoparticles, prepared in the AOT/isooctane system, was significantly lower than that of the micrometer-size particles prepared in a homogeneous aqueous solution, since the calcined nanoparticles contained Na2SO4 impurity derived from the remaining AOT surfactant. The nanoparticles prepared in the NP-5/cyclohexane system, in contrast, showed higher emission intensity compared to the nanoparticles prepared in the AOT/isooctane system and longer luminescence lifetime compared to the micrometer-size particles prepared in the homogeneous aqueous solution. The photoluminescence intensity of Y2O3:Eu3+, prepared via the proposed process was found to decrease with decreasing the particle size.     

Mechanism of laser-induced size-reduction of gold nanoparticles as studied by nanosecond transient absorption spectroscopy

Gold nanoparticles with an average diameter of approximately 8 nm (Au approximately 15,000) were irradiated with a tightly focused pulse laser at 355 nm in an aqueous solution of sodium dodecyl sulfate (SDS). Transient absorption spectra of the solution were measured at 25-100 ns after the laser irradiation. The observed transient absorption around 720 nm is assignable to the 2p <-- 1s transition of solvated electrons produced via multiple ionization of the gold nanoparticles. The nascent charge state of the gold nanoparticles was estimated from the transient absorbance. The dependence of the charge state on the SDS concentration shows a gradual increase from approximately +60 to approximately +70 in the 2 x 10(-4) to 3 x 10(-4) M range and an abrupt increase up to approximately +710 at the critical micelle concentration (CMC) of SDS, 8 x 10(-3) M. TEM measurements after laser irradiation reveal that the gold nanoparticles fragment into Au(approximately 1000) at a SDS concentration of 3 x 10(-4) M, whereas they are significantly dissociated into Au(approximately 100) above the CMC. The observed correlation between the nascent charge states and the extent of size reduction of the gold nanoparticles after the laser treatment indicates that the size reduction is caused by the Coulomb explosion of the highly charged gold nanoparticles. The mechanism of laser-induced size reduction is quantitatively discussed based on the liquid drop model.     

水杨酸盐敏化BaF2∶Tb3+纳米粒子中的Tb3+离子发光

采用水热法制备了均匀、单分散的BaF₂∶Tb³⁺纳米粒子,并采用离子交换法制备了水杨酸钠敏化的BaF₂∶Tb³⁺纳米粒子(SS-BaF₂∶Tb³⁺)。 系统地研究了样品的结构、形貌和光致发光性质。 结果表明,监测Tb³⁺离子在547 nm的⁵D₄→⁷F₅跃迁,SS-BaF₂∶Tb³⁺纳米粒子获得了从200 nm到385 nm波长范围宽的激发带;激发SS的π-π^*电子跃迁吸收,由于SS到Tb³⁺的能量传递(“天线效应”),SS-BaF₂∶Tb³⁺纳米粒子产生了增强的Tb³⁺离子绿光发射;敏化纳米粒子中Tb³⁺离子光致发光寿命比未敏化纳米粒子中Tb³⁺离子寿命长。     

Ag_核Au_壳金属复合纳米粒子的制备及表面增强拉曼光谱研究

在已制备好的Ag纳米粒子表面,通过化学还原的方法沉积生长Au包裹层,制备了粒子尺寸为50-70nm的Ag核Au壳复合纳米粒子.通过改变AuCl₄^-量,使Ag_100-xAu_x中Au的含量由x=0变为x=30.用UV-Vis吸收光谱和透射电子显微镜(TEM)对该结构纳米粒子进行了表征,并以对巯基苯胺(PATP)为探针分子进行表面增强拉曼光谱(SERS)研究.表面拉曼光谱表明,该结构的纳米粒子具有比Ag更强的SERS活性,随着Au:Ag比例的逐渐增加,其活性呈现先增大后减小的趋势,其最大增强约为Ag纳米粒子的10倍.     

TiO2与ZnO复合纳米结构电极的光电化学研究

利用尿素加压共沉淀法以Ti(SO4)2与Zn(NO3)2为原料制备了TiO2-ZnO复合纳米粒子, 其纳米结构电极的光电化学研究结果表明, 反应物摩尔比为3∶1, 于530 ℃煅烧制备的复合纳米结构电极的光电转换效率最高. 对吸附染料RuL2(SCN)2∶2TBA的纳米结构TiO2和各种复合纳米粒子的纳米结构电极进行光电研究的结果表明, 染料对各纳米结构电极都起到了敏化作用, 其中也是由反应物摩尔比为3∶1, 于530 ℃煅烧制备的纳米结构电极的光电转换效率最高. 对聚3-甲基噻吩修饰的纳米结构TiO2和摩尔比为3∶1, 于530 ℃煅烧的复合纳米粒子构成的纳米结构电极进行光电性能研究, 结果表明, 聚3-甲基噻吩与半导体纳米粒子之间存在p-n结, 在一定条件下p-n结的存在有利于光生电子/空穴的分离, 从而提高了光电转化效率.     

Fe3O4 and gamma-Fe2O3 nanoparticles for the adsorption of Co2+ from aqueous solution

The adsorption of Co2+ ions from nitrate solutions using iron oxide nanoparticles of magnetite (Fe3O4) and maghemite (gamma-Fe2O3) has been studied. The adsorption of Co2+ ions on the surface of the particles was investigated under different conditions of oxide content, contact time, solution pH, and initial Co2+ ion concentration. It has been found that the equilibrium can be attained in less than 5 min. The maximum loading capacity of Fe3O4 and gamma-Fe2O3 nanoparticles is 5.8 x 10(-5) and 3.7 x 10(-5) mol m(-2), respectively, which are much higher than the previously studied, iron oxides and conventional ion exchange resins. Co2+ ions were also recovered by dilute nitric acid from the loaded gamma-Fe2O3 and Fe3O4 with an efficiency of 86 and 30%, respectively. That has been explained by the different mechanisms by including both the surface and structural loadings of Co2+ ions. The surface adsorption of Co2+ on Fe3O4 and gamma-Fe2O3 nanoparticles has been found to have the same mechanism of ion exchange reaction between Co2+ in the solution and proton bonded on the particle surface. The conditional equilibrium constants of surface adsorption of Co2+ on Fe3O4 and gamma-Fe2O3 nanoparticles have been determined to be log K=-3.3+/-0.3 and -3.1+/-0.2, respectively. The structural loading of Co2+ ions into Fe3O4 lattice has been found to be the ion exchange reaction between Co2+ and Fe2+ while that into gamma-Fe2O3 lattice to fill its vacancy. The effect of temperature on the adsorption of Co2+ was also investigated, and the value of enthalpy change was determined to be 19 kJ mol(-1).     

Preparation of ZnSe Nanoparticles via Low‐Temperature Solid Phase Process

ZnSe nanoparticles were prepared from ZnCl₂, Se and KBH₄ in the presence of cetyltrimethyl ammonium bromide (CTAB) through a room temperature solid phase process. The products were characterized with x‐ray diffraction (XRD), transmission electron microscope (TEM), and energy dispersive analysis of x‐ray (EDAX). The results show that the cubic zincblende phase ZnSe nanoparticles can be obtained using this simple method. The size of nanoparticles was evaluated to be from 8 to 30 nm.     

Luminescence behavior of Eu3+ doped LaF3 nanoparticles

Europium-doped LaF3 nanoparticles have been prepared by the ionic reaction in the ethanol at 60 degrees C. From the XRD pattern of nanoparticles and the emission spectra of Eu3+ ions, it has been concluded that the Eu3+ ions could easily substitute the La3+ sites and the solid solution La(1-x)Eu(x)F3 can be synthesized. Due to very low phonon energies of LaF3 matrix, the 5D1 emission of Eu3+ ions in La(1-x)Eu(x)F3 nanoparticles can be observed at room temperature when doping concentration of Eu3+ ions is lower than 30 mol%. The quenching process of 5D1 emission can be attributed to cross-relaxation. Since clusters of Eu3+ ions and resonance energy transfer only occurs within one particle due to the hindrance by the particle boundary, the concentration quenching resulted from resonance energy transfer between neighboring Eu3+ ions occurs at higher Eu3+ concentrations in the Eu3+ doped LaF3 nanoparticles.     

Micelle directed synthesis of polyoxometalate nanoparticles and their improved catalytic activity for the aerobic oxidation of sulfides

Micelle directed polyoxometalate nanoparticles were synthesized by depositing H3+xPVxMo12-xO40 (x = 0, 2) by precipitation on micelles prepared from cesium dodecyl sulfate. The cryo-TEM image showed particles of about approximately 10 nm roughly consistent with the particle size computed from an idealized model. HRTEM coupled with EELS imaging to map the distribution of the elements also supported the formation of micelle directed polyoxometalate nanoparticles. In the aerobic oxidation of various sulfides to sulfoxides and sulfones, the clustered polyoxometalate assemblies supported on hydrophilic silica showed significantly higher catalytic activity versus that of nonclustered assemblies.