聚3-甲基噻吩及聚3-己基噻吩修饰钛酸盐纳米管的光电化学性能研究

采用水热法制备了钛酸盐纳米管, 并将钛酸盐纳米管制备成纳米结构电极进行光电化学研究. 钛酸盐纳米管产生阳极光电流, 具有n-型半导体特性. 结果表明, 聚3-甲基噻吩[poly(3-methylthiophene), PMeT]、聚3-己基噻吩[poly(3-hexylthiophene), P3HT]修饰钛酸盐纳米管后产生的光电流均较纯钛酸盐纳米管的光电流高, 且使产生光电流的波长向长波区移动. 钛酸盐纳米管/PMeT、钛酸盐纳米管/P3HT的光电转换效率分别达11.40%, 0.91%(未校正光子损失). 钛酸盐纳米管/PMeT的光电转换效率较钛酸盐纳米管/P3HT的光电转换效率高10.5%. 钛酸盐纳米管/PMeT、钛酸盐纳米管/P3HT中存在p-n异质结, 在一定条件下p-n异质结的存在有利于光生电子/空穴的分离.     

盐酸后处理对水热合成纳米钛酸盐形貌及光限幅效应的影响

采用碱性水热合成法制备纳米钛酸盐, 研究盐酸后处理对纳米钛酸盐-二氧化钛形貌及光限幅效应的影响. 采用X射线衍射分析仪、透射电子显微镜和扫描电子显微镜对样品的晶型转变及形貌演变进行表征, 通过紫外-可见光谱与开孔Z扫描激光测试技术, 研究样品的线性光学与非线性光学效应. 结果表明, 当酸处理浓度介于0.10-0.55 mol·L^-1范围时, 水热产物由钛酸盐转变为钛酸盐/二氧化钛混合物; 当酸处理浓度高于0.78mol·L^-1时, 钛酸盐近乎完全转变为金红石型二氧化钛. 在酸处理过程中, 纳米钛酸盐晶型转变速率与盐酸的浓度直接相关. 随着盐酸浓度的增加, 钛酸盐体系中逐步分离出游离的TiO₆八面体, 进而发生TiO₆八面体重组, 使水热产物由钛酸盐纳米管转变成二氧化钛纳米片和纳米颗粒. 当盐酸浓度为0.55 mol·L^-1时, 样品表现出最强的光限幅效应.     

纳米结构钛酸盐电极快速测定水体COD

分析了纳米结构钛酸盐电极快速测定COD的基本原理及COD标准物质定值方法。通过对纳米结构钛酸盐表征分析,钠型钛酸盐电极具有较高的灵敏度,外加0.7 V工作电位,测定COD溶液标准物质的线性相关系数大于0.995,误差在±8%以内;与国标方法比较,测量同一水样的误差在±15%以内。纳米结构钛酸盐电极可用于测量水体COD。     

钛酸盐纳米管的制备及光电性能研究

采用水热法制备了钛酸盐纳米管, 并用TEM、XRD、XPS对其进行了表征. 纳米管管径在5~30 nm之间, 管长约为0.1~1 μm, 具有不同于锐钛矿型的钛酸盐结构, 分子组成可能是Na4－xHxTi2O5. 将钛酸盐纳米管制备成纳米管结构电极, 并进行了光电化学研究. 钛酸盐纳米管产生阳极光电流, 具有n型半导体特性.     

卟啉敏化的钛酸盐纳米管的可见光催化活性

制备了四碘化5,10,15,20-四(对-N,N,N三甲基苯胺基)卟啉敏化的钛酸盐纳米管(TAPPI-TNTs),并利用甲基橙(MO)作为模型污染物考察了其可见光催化活性。结果表明,TAPPI-TNTs是一个高效的可见光催化剂,在其催化作用下,可见光照射1 h后,甲基橙的降解率为89%。与此相反,纯钛酸盐纳米管并不具有可见光催化活性。此外,TAPPI-TNTs的稳定性较高,可以多次循环使用,在第五次循环中,甲基橙的降解率仍可达到50%以上。这可能是由于带正电荷的卟啉与带负电荷的钛酸盐纳米管之间存在着较强的静电吸引作用,卟啉紧密地吸附在钛酸盐纳米管上,导致卟啉的光激发电子易于向钛酸盐纳米管转移,从而使钛酸盐纳米管得到了有效敏化。     

规则结构钛酸盐自组装聚集体的制备

在水热条件下, 采用不同的钛源, 通过控制溶液碱度和冷却温度等反应条件, 利用无模板自组装技术, 在钛酸盐薄膜表面及溶液相中制备了鸟巢状和绒球状钛酸盐纳米带自组装聚集体以及海胆状钛酸盐纳米管自组装聚集体. 通过引入碳酸钠模板, 制备出形貌新颖的钛酸钠-碳酸钠香蒲状自组装聚集体复合材料. 初步研究了纳米自组装聚集体的形成机理, 认为其形成经历了一维纳米结构(纳米带或纳米管)的生长和一维纳米结构的自组装2个过程.     

不同TiO2原料制备一维钛酸盐纳米材料

以不同二氧化钛为原料, 用水热法制备一维钛酸盐纳米材料. 原料一次粒径和晶体结构对一维纳米钛酸盐的形貌和结构的影响很大. 原料的一次粒径越小, 反应过程中产物的形貌和晶相转变越快; 纯锐钛矿相有利于钛酸盐纳米管的形成, 而少量金红石相则有利于纳米管向纳米线的进一步转变和晶相转变.     

Ag/AgNO3修饰钛酸盐纳米管薄膜的制备及性能

采用水热法合成了钛酸盐纳米管薄膜,通过光催化还原反应将Ag/AgNO3纳米粒子负载其上,制得Ag/AgNO3修饰钛酸盐纳米管薄膜,并对其形貌、结构和化学组成进行了表征.Ag/AgNO3修饰后钛酸盐纳米管薄膜的性能发生了明显变化,不仅展示出光致变色的性能,而且光催化活性得到显著提高,此外,纳米管表面产生出的活泼自由基协同具有强氧化能力的Ag+能有效抑制或杀灭细菌,使薄膜具有优异的抗菌性能.     

钛酸钠一维纳米结构的构筑

以锐钛矿TiO₂为起始原料,通过水热法制备了钛酸盐纳米棒,对合成不同长度和宽度的钛酸盐纳米棒的影响和控制条件进行了研究。用X射线衍射(XRD)和扫描电子显微镜(SEM)对纳米棒的形貌和结构进行了表征。结果表明水热温度和处理时间能对纳米棒的形貌和结构进行有效的控制,得到理想的钛酸盐的结构。在更高的温度下(200 ℃),钛酸盐纳米管将更快的转化为纳米棒,而随着处理时间的延长,其形貌结构发生有规律的变化。在96 h处理时间后纳米棒束的宽度为50 nm到1 μm,长度可以达到几十微米。对后处理中酸洗对产物的形貌和晶体结构的影响也进行了对比研究,发现在酸洗之前钛酸盐纳米棒结构就已经形成,但是酸洗能使产物的晶体结构产生变化,同时使纳米棒的表面形貌更加光滑规整。最后对比研究原料和产物的紫外-可见吸收光谱,发现纳米管/棒在250至350 nm处有宽带隙吸收。     

多壁碳纳米管-钛酸盐纳米管复合纳米材料的制备及其生物电化学性能

以TiO2纳米颗粒为前体,采用碱性水热法制备出钛酸盐纳米管(TNTs)与多壁碳纳米管(MWCNTs)的复合纳米材料(MWCNT-TNT);借助透射电子显微镜、傅立叶变换红外光谱仪和X射线衍射仪分析了纳米材料的结构、组成和形貌.将辣根过氧化酶,室温离子液体,Nafion和复合纳米材料共同修饰在电极表面组成酶电极,利用循环伏安法研究了该酶电极的电化学性能.结果表明,TiO2纳米颗粒完全转化为钛酸盐纳米管并且很好的与MWCNTs结合在一起;复合材料修饰酶电极的循环伏安行为明显优于TNTs修饰酶电极,表明引入MWCNTs可改善钛酸盐纳米材料的导电性以及电化学性能.     

Large-scale synthesis of sodium and potassium titanate nanobelts

A low-temperature solution-based synthetic method was developed for the large-scale synthesis of one-dimensional nanostructures of alkali titanates. Two kinds of highly pure ribbonlike titanates were synthesized successfully in gram quantities without introducing any templates or catalysts. The structure and composition of the titanates were characterized by XRD, HRTEM, and EDX. The chemical and physical properties were preliminarily characterized, and some distinctive properties were observed.     

Synthesis of classes of ternary metal oxide nanostructures

Nanoscale structures, such as nanoparticles, nanorods, nanowires, nanocubes, and nanotubes, have attracted extensive synthetic attention as a result of their novel size-dependent properties. Ideally, the net result of nanoscale synthesis is the production of structures that achieve monodispersity, stability, and crystallinity with a predictable morphology. Many of the synthetic methods used to attain these goals have been based on principles derived from semiconductor technology, solid state chemistry, and molecular inorganic cluster chemistry. We describe a number of advances that have been made in the reproducible synthesis of various ternary oxide nanomaterials, including alkaline earth metal titanates, alkali metal titanates, bismuth ferrites, ABO(4)-type oxides, as well as miscellaneous classes of ternary metal oxides.     

Variations on the theme of closest packing: The structural chemistry of barium titanate compounds

The crystal structures of most barium titanates can be described as hexagonal closest packings consisting of atoms of Ba and O and of vacancies between them. The pseudohexagonal cell constants of these compounds are close to the ideal hexagonal values. The most common stacking is the six-layer sequence (hcc)₂. The mean diameter of a closest packed particle in these packings is 2.85 Å, while the mean thickness of a layer is 2.33 Å. The recognition of this closest packing principle has been helpful in the solution of many of the crystal structures of this group. With the exception of BaTi₄O₉, all the barium titanates which are usually classified as tunnel structures or Wadsley-Andersson phases can be described as cubic closest packings. The deviations of the pseudocubic phases from the ideal cubic values are larger than in the pseudohexagonal cases. A few of the barium titanates are related to the so-called 3.0-Å phases based on the rutile-type octahedral chain. These structures are characterized by having two almost closest packed corrugated layers at right angles to each other. The structures of a number of compounds in which the Ti⁴⁺ atoms are replaced partly by Ti³⁺, Al, Pt⁴⁺, or Li are based on principles similar to those of the barium titanates proper. The mean TiO distances in the coordination octahedra of the barium titanates depend strongly on the distortions of the octahedra.     

Room temperature synthesis of protonated layered titanate sheets using peroxo titanium carbonate complex solution

We report the synthesis of peroxo titanium carbonate complex solution as a novel water-soluble precursor for the direct synthesis of layered protonated titanate at room temperature. The synthesized titanates showed excellent removal capacity for Pb(2+) and methylene blue. Based on experimental observations, a probable mechanism for the formation of protonated layered dititanate sheets is also discussed.     

氮磷配位的钛酸酯络合物的X射线光电子能谱研究

制备了单烷基羧酸型和磺酸型钛酸酯氮配位与磷配位的配合物.用XPS法证明有N→Ti或P→Ti配位键生成,并从化学位移量推测了键的强度,磺酸型较羧酸型易配位,羟基取代胺的氮配体配位较容易发生;磷配位由于存在Ti→P的反馈作用,使化学位移不如氮配位明显.此外,异丙基钛酸酯与乙醇胺的反应物,证明分子内有N→Ti配位键生成.     

1,4 polymerization of isoprene by titanate catalyst systems

Titanates are versatile in the 1,4 polymerization of isoprene. The (R′O)₄Ti/RAlCl₂ catalyst gives either cis- or trans-1,4-polyisoprene, depending on the nature of both the titanate and the solvent. Primary titanates give cis-1,4-polyisoprene in both aliphatic and aromatic solvents. Secondary titanates give cis-polyisoprene in aliphatic solvents, and trans-1,4-polyisoprene in aromatic solvents. Tertiary titanates give trans-polyisoprene in both aliphatic and aromatic solvents. A mechanism is postulated which takes into consideration the role of the solvent. ESR studies of the various titanate–RAlCl₂ catalysts were made; the paramagnetic structures are related to polymerization mechanisms.     

Synthesis and properties of Sc- and Mg-doped bismuth titanates with the pyrochlore structure

Scandium(Magnesium)-containing bismuth titanates with the pyrochlore structure have been synthesized for the first time. Their homogeneity range has been determined by means of X-ray diffraction analysis and scanning electronic microscopy. Scandium and magnesium distribution over the cationic positions has been studied. Electrophysical properties of single-phase compounds have been studied. The total conductivity of the compounds is a function of magnesium (scandium) and bismuth concentrations.     

Structure, reactivity, photoactivity and stability of Ti-O based materials: a theoretical comparison

Ti-O based materials have attracted great attention recently for their potential applications in clean energy generation and environment remediation. To screen Ti-O based materials for specific applications, the atomic-level understanding of the subtle discrepancy of their properties is of paramount importance. In this regard, the density functional theory computations have been performed to systematically compare the physicochemical properties of three selected Ti-O based materials: anatase titanium dioxides, sodium trititanates and sodium hexatitanates. Due to their structure discrepancy, sodium trititanates show the highest chemical reactivity. However, titanium dioxides are found to be the most photoactive materials. The reactivity and photoactivity of sodium hexatitanates fall between those of titanium dioxide and sodium trititanates. In the meantime, our energetic analysis also confirms that the thermal stabilities of Ti-O based materials are strongly dependent on the acid-base conditions. Titanium dioxides are preferred under acidic conditions, while titanates are more stable in basic solutions.     

Adsorption of 137Cs on titanium ferrocyanide and transformation of the sorbent to lithium titanate: a new method for long term immobilization of 137Cs

Dynamic adsorption of radiocesium on titanium ferrocyanide grains from reactor coolant simulating solution containing salts at moderate concentrations has been investigated. Effective decontamination of the neutral solutions has been achieved, in the amounts of a more than 20 thousand bed volumes. After adsorption the titanium ferrocyanide was transferred to titanates and calcined at 900 °C. The leaching test of the obtained lithium titanates indicates that the loaded adsorbent can serve as an effective primary barrier in nuclear waste repositories.     

ChemInform Abstract: On the Crystal Energy and Structure of A2TinO2n+1 (A: Li,Na, K) Titanates by DFT Calculations and Neutron Diffraction.

The formation energies of the title alkali layered titanates (n = 3, 4, 6) are determined by DFT calculations for different monoclinic structure configurations.