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1.
研究了用一步水热法制备的不同形貌的钛酸铋(Bi4Ti3O12, BIT)粒子的光学和可见光催化性能, 并对其晶体结构和微观结构用X射线衍射(XRD)、场发射扫描电子显微镜(FESEM)、透射电子显微镜(TEM)和高分辨透射电子显微镜(HRTEM)等手段进行了表征. XRD结果表明, 所制备的BIT 样品为层状钙钛矿结构. FESEM结果表明, 通过控制水热过程的反应参数可以得到不同形貌的纳米粒子. 紫外-可见漫反射光谱(UV-Vis DRS)表明BIT 样品的带隙能约为2.88-2.93 eV. 利用可见光(λ>420 nm)照射下的甲基橙(MO)降解实验评价了BIT 样品的光催化性能. 结果表明, BIT 的光催化活性比掺氮TiO2 (N-TiO2)高得多. 研究了形貌对BIT 光催化性能的影响. 所制备的BIT纳米带光催化效率最高, 经可见光照射360 min, 甲基橙溶液的降解率可达到95.0%. 相似文献
2.
通过可控水热法,制备出层状、花形和棒状钛酸铋(Bi4Ti3O12,BIT)纳米结构。通过X射线衍射(XRD)和场发射扫描电子显微镜(FESEM)观测其结构和形貌特征。XRD图显示,所制备的样品为层状钙钛矿结构。FESEM结果表明,通过控制水热过程的反应参数可以得到不同形貌的纳米粉体。紫外-可见漫反射光谱(UV-Vis DRS)表明BIT样品的带隙能约为2.63~2.95 eV。利用可见光(λ>420 nm)照射下的甲基橙降解实验评价了BIT样品的光催化性能。结果表明,BIT的光催化活性比掺氮TiO2(N-TiO2)高得多。所制备的层状BIT纳米结构光催化效率最高,经可见光照射360 min,甲基橙溶液的降解率可达95.0%。同时还研究了结构和形貌对不同条件下制备的BIT样品光催化活性的影响。 相似文献
3.
通过无模板、无助剂的可控水热法, 制备出球形、花形和线状钒酸铋(BiVO4), 研究了其光学和可见光催化性能. 通过X射线衍射(XRD)和透射电镜(TEM)观测其结构和形貌特征. XRD谱线显示, 所制备的样品为单斜晶体结构. TEM结果表明, 通过控制水热过程的反应参数可以得到不同形貌的纳米粉体. 基于不同条件下制备的样品的微结构分析, 提出了这些不同形貌的形成机制. 紫外-可见漫反射光谱(UV-Vis DRS)表明BiVO4样品的带隙能约为2.19-2.33 eV. 利用可见光(λ>420 nm)照射下的罗丹明B(RhB)降解实验评价了BiVO4样品的光催化性能. 结果表明, BiVO4的光催化活性比商用TiO2催化剂P25 和掺氮TiO2 (N-TiO2)高得多. 所制备的球形BiVO4光催化效率最高, 经可见光照射180 min, RhB溶液的降解率可达100%. 系统地研究了结构和形貌对不同pH值下制备的BiVO4样品光催化活性的影响. 相似文献
4.
用电化学方法制备Ag3PO4/Ni薄膜,以扫描电子显微镜(SEM)、X射线衍射(XRD)和紫外-可见漫反射光谱(UV-Vis DRS)对薄膜的表面形貌、晶相结构、光谱特性及能带结构进行了表征,以罗丹明B为模拟污染物对薄膜的光催化活性和稳定性进行了测定,采用向溶液中加入活性物种捕获剂的方法对薄膜光催化降解机理进行了探索.结果表明:最佳工艺下制备的Ag3PO4/Ni薄膜具有致密的层状表面结构,是由多晶纳米颗粒构成的薄膜.薄膜具有较高的光催化活性和突出的光催化稳定性,可见光下催化作用60 min,薄膜光催化罗丹明B的降解率是多孔P25 TiO2/ITO纳米薄膜(自制)的2.3倍;在保持薄膜光催化活性基本不变的前提下可循环使用6次.给出了可见光下薄膜光催化降解罗丹明B的反应机理. 相似文献
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在二甲基甲酰胺溶液中, 通过简单的沉淀法制备了纳米Ag2CO3和碳纳米管(CNT)的复合物. 用X射线衍射(XRD)、傅里叶变换红外(FTIR)光谱、扫描电镜(SEM)和紫外-可见(UV-Vis)漫反射光谱(DRS)表征了所制备的Ag2CO3/CNT复合物, 通过在可见光下降解甲基橙(MO)检测了样品的光催化活性. 结果表明, 纳米Ag2CO3颗粒与CNT结合良好. CNT的含量为1.5% (w)的Ag2CO3/1.5% CNT复合物活性最高, 经过60 min 的降解, 甲基橙的降解率达到93%. 与纯相纳米Ag2CO3比较, CNT的加入还提高了Ag2CO3的稳定性, 经过三次循环降解, Ag2CO3/1.5% CNT复合物还能降解81%的甲基橙, 而纳米Ag2CO3只能降解59.5%的甲基橙. 其活性和稳定性提高的原因是由于CNT的高导电性, 它不仅促进了电子-空穴对的分离, 还能快速转移产生的光生电子. 相似文献
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用水热法制备掺镁钛酸钡(Ba1-xMgxTiO3(x=0,0.10,0.20,0.30,0.40),BMT)纳米粉体。运用X射线衍射仪(XRD)、场发射扫描电子显微镜(FESEM)、透射电子显微镜(TEM)、紫外可见漫反射光谱技术(DRS)等手段对样品进行了表征,并在可见光照射下于溶液中考察了其光催化降解甲基橙反应活性。结果表明,通过控制氢氧根浓度可以得到不同形貌的纳米粉体。基于不同条件下制备的样品的微结构分析,提出了这些不同形貌的形成机制。制备出的BMT材料的带隙能约为2.61 eV。光催化反应结果表明BMT的光催化活性比掺氮TiO2高得多。OH-浓度为8 mol·L-1时制备的BMT纳米棒光催化效率最高,经可见光照射360 min,浓度为0.01 mmol·L-1甲基橙溶液的降解率可达到93.0%,且循环使用4次后,其光催化活性并没有明显降低,表明BMT是一种稳定有效的可见光催化剂. 相似文献
7.
研究了用一步水热法制备的掺镧钛酸铋(Bi3.25La0.75Ti3O12, BLT)纳米线的光学和可见光催化性能, 并对其晶体结构和微观结构用X射线衍射(XRD)、透射电子显微镜(TEM)和高分辨透射电子显微镜(HRTEM)等手段进行了表征. 结果表明, 制备的纳米线为纯相的Bi3.25La0.75Ti3O12, 平均直径约为25 nm. 室温光致发光谱(PL)显示BLT纳米线在433和565 nm附近有较强的发射峰, 分别对应激子发射和表面缺陷发光. 紫外-可见漫反射光谱(UV-Vis DRS)表明BLT样品的带隙能约为2.07 eV. 利用可见光(λ>420 nm)照射下的甲基橙降解实验评价了BLT样品的光催化性能. 结果表明, BLT的光催化活性比商用TiO2催化剂P25、掺氮TiO2和纯相钛酸铋(Bi4Ti3O12, BIT)高得多. BLT光催化剂具有更高催化活性的原因是La3+离子掺杂拓展了BIT对可见光的吸收范围, 同时抑制了BIT的光生电子-空穴的复合. 相似文献
8.
为了用BiOBr提高TiO2的光催化活性,人们做了大量的研究。然而,大多数工作合成的都是粉体结构,难以回收且易造成二次污染。本文通过静电纺丝技术结合溶剂热法制备了柔性的BiOBr/TiO2/PAN 纳米纤维膜,因其独特的自支撑膜结构,使问题得到解决。通过 SEM、TEM、XPS 、XRD和BET等对其结构和形貌进行表征,使用 UV-Vis DRS、EIS和i-t对其光电性能进行分析。结果表明,与单独的TiO2/PAN相比,在可见光照射下,BiOBr/TiO2/PAN 纳米纤维膜对盐酸四环素(TCH)降解的光催化活性增强,在140min内降解效率达到72.97%;5次循环实验中,催化剂的催化性能趋于稳定,循环后的XRD和SEM表明催化剂形貌和晶体结构没有发生改变,表现出优异的耐久性。 相似文献
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原位碳、氮共掺杂二氧化钛空心球的制备与可见光光催化性能 总被引:3,自引:0,他引:3
在H2O2-HF 的乙醇-水混合溶液中, 通过水热处理碳氮化钛(TiCN)制备了碳、氮共掺杂TiO2 空心球(CNTH). 用X 射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)、X 射线光电子能谱(XPS)和紫外-可见(UV-Vis)吸收光谱表征了所制备的样品. 在可见光(λ≥400 nm)照射下, 通过降解甲基蓝检测了碳、氮共掺杂TiO2空心球的光催化活性. 结果表明, 源于TiCN中的部分碳和氮原子原位掺入了TiO2的晶格中, 部分碳掺入TiO2点阵的间隙中. 该材料在整个可见光区展示了增强的可见光吸收, 其带边明显红移. 光催化研究表明在强可见光吸收和独特的空心球结构的协同作用下, 碳、氮共掺杂TiO2空心球展示了比P25更高的可见光光催化活性. 相似文献
11.
H. Schumann 《Angewandte Chemie (International ed. in English)》1969,8(12):937-950
The preparation, properties, and reactions of the compounds named in the title are described, with particular reference to the possible participation of (p→d)π components in the bonding between the group IVB and the group VB elements. 相似文献
12.
Dr. Wenlong Yang Dr. Jorge H. S. K. Monteiro Prof. Ana de Bettencourt‐Dias Prof. Vincent J. Catalano Prof. Wesley A. Chalifoux 《Angewandte Chemie (International ed. in English)》2016,55(35):10427-10430
The design of a relatively simple and efficient method to extend the π‐conjugation of readily available aromatics in one‐dimension is of significant value. In this paper, pyrenes, peropyrenes, and teropyrenes were synthesized through a double or quadruple benzannulation reaction of alkynes promoted by Brønsted acid. This novel method does not involve cyclodehydrogenation (oxidative aryl–aryl coupling) to arrive at the newly incorporated large arene moieties. All of the target compounds were synthesized in moderate to good yields and were fully characterized with the structures unambiguously confirmed by X‐ray crystallography. As expected, photophysical characterization clearly shows increasing red‐shifts as a function of extended conjugation within the fused ring systems. 相似文献
13.
C. Peter Sebastian Constanze Fehse J. Paul Attfield Sudhindra Rayaprol Rainer Pöttgen 《Journal of solid state chemistry》2006,179(8):2376-2385
The rare earth-silver-stannides YAgSn, TmAgSn, and LuAgSn were synthesized from the elements by arc-melting and subsequent annealing. The three stannides were investigated by X-ray powder and single-crystal diffraction: NdPtSb type, P63mc, Z=2, a=468.3(1), pm, wR2=0.0343, 353 F2 values, 12 variables for YAgSn, and ZrNiAl type, P6¯2 m, a=726.4(2), , wR2=0.0399, 659 F2 values, 15 variables for TmAgSn, and a=723.8(2), , wR2=0.0674, 364 F2 values, 15 variables for LuAgSn. Besides conventional laboratory X-ray data with monochromatized Mo radiation, the structures were also refined on the basis of synchrotron data with , in order to clarify the silver-tin ordering more precisely. YAgSn has puckered, two-dimensional [AgSn] networks with Ag-Sn distances of 278 pm, while the [AgSn] networks of TmAgSn and LuAgSn are three-dimensional with Ag-Sn distances of 279 and 284 pm for LuAgSn. Susceptibility measurements indicate Pauli paramagnetism for YAgSn and LuAgSn. TmAgSn is a Curie-Weiss paramagnet with an experimental magnetic moment of 7.2 μB/Tm. No magnetic ordering is evident down to 2 K. The local environments of the tin sites in these compounds were characterized by 119Sn Mössbauer spectroscopy and solid-state NMR (in YAgSn and LuAgSn), confirming the tin site multiplicities proposed from the structure solutions and the absence of Sn/Ag site disordering. Mössbauer quadrupolar splittings were found in good agreement with calculated electric field gradients predicted quantum chemically by the WIEN2k code. Furthermore, an excellent correlation was found between experimental 119Sn nuclear magnetic shielding anisotropies (determined via MAS-NMR) and calculated electric field gradients. Electronic structure calculations predict metallic properties with strong Ag-Sn bonds and also significant Ag-Ag bonding in LuAgSn. 相似文献
14.
Wenlong Yang Jorge H. S. K. Monteiro Ana deBettencourt‐Dias Vincent J. Catalano Wesley A. Chalifoux 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2016,128(35):10583-10586
The design of a relatively simple and efficient method to extend the π‐conjugation of readily available aromatics in one‐dimension is of significant value. In this paper, pyrenes, peropyrenes, and teropyrenes were synthesized through a double or quadruple benzannulation reaction of alkynes promoted by Brønsted acid. This novel method does not involve cyclodehydrogenation (oxidative aryl–aryl coupling) to arrive at the newly incorporated large arene moieties. All of the target compounds were synthesized in moderate to good yields and were fully characterized with the structures unambiguously confirmed by X‐ray crystallography. As expected, photophysical characterization clearly shows increasing red‐shifts as a function of extended conjugation within the fused ring systems. 相似文献
15.
Piers WE Bourke SC Conroy KD 《Angewandte Chemie (International ed. in English)》2005,44(32):5016-5036
Boron cations are elusive and highly electrophilic species that play a key role in the chemistry of boron. Despite early interest in the chemistry of boron cations, until recently they have largely remained chemical curiosities. However, hints at harnessing their potential as potent electrophiles have begun to appear and developments in weakly coordinating anion technology suggest that this is an area of research that is ripe for exploration. It has been nearly 20 years since the last major review on boron cations; herein we summarize the progress in the area since that time. 相似文献
16.
A systematic quantum chemical investigation of mono-, di-, and triaminoborane, -alane, -gallane, and -indane is carried out to determine quantitatively the effects of pi bonding and negative hyperconjugation on structures, energetics, and rotational barriers in these systems. Pi bonding plays a significant role in the aminoborane compounds, but becomes rapidly less significant in the aminoalanes, -gallanes, and -indanes. For each main-group metal X investigated, X-N rotational barriers are found to be essentially equal depending only on the number of remaining in-plane amino groups. The contribution of negative hyperconjugation to reducing rotational barriers, as assessed from natural bond orbital (NBO) delocalization energies, is independent of the pyramidalization of the out-of-plane amino group, and is also dependent only on the number of rotated groups. Optimized tris[bis(trimethylsilyl)amino]-substituted structures of boron, aluminum, gallium, and indium are found to compare quite well with available experimental structural data, and exhibit X-N torsion angles that are independent of the central metal atom. 相似文献
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A new protocol for the Ullmann-type arylation process of different aromatic heterocycles without any transition-metal catalyst, implying the use of a combination of an excess of potassium hydroxide and dimethyl sulfoxide, is described. The reaction can be performed between a broad range of starting nucleophiles including phenol, alcohols, amines, nitrogen-containing five-membered systems such as pyrazoles, imidazoles, and indoles, and amides with haloarenes, iodide and bromide derivatives giving the best results, the possible pathway involving the in situ generation of the corresponding benzyne intermediate. When the reaction was performed with 2-iodoaniline and either carboxamides or isothiocyanato derivatives, the corresponding benzoazole derivatives were obtained. 相似文献
19.
布兰顿首先将“规范”当作人类活动的核心特征,并以实用主义的方式回答了规范的性质问题;然后再由规范引出推论作为语言意义的根据,并澄清了实质推论的基础地位;接着又进一步,细致解析了推论的实际运作机制,将推论落实于社会交往的过程之中,认为社会交往本质上是不同成员之间的道义计分;最后,在推论主义框架下解释了真、表象语汇的必要性,并对语言与世界的关系做出了推论主义的说明。他的哲学体系由规范、推论、交往、世界四个维度组成。它们层层递进,形成了一个具有严密内在结构的有机整体。原本分散甚至对立的论题,在此得到整合。 相似文献
20.
Rolf W. Saalfrank Norbert Löw Bernhard Demleitner Dietmar Stalke Markus Teichert 《Chemistry (Weinheim an der Bergstrasse, Germany)》1998,4(7):1305-1311
Efficacious metal control of self-assembly of dialkylketipinate dianions leads to completely different supramolecular assemblies. The structures of grid 1 , double-decker 2 , triple-decker 3 , and metalla-spherand 4 were characterized by X-ray crystallographic analyses or by NMR spectroscopy. 相似文献