分子识别作用下光催化降解偶氮染料酸性红B

以250 W金属卤化物灯(λ365 nm)为光源,二氧化钛为催化剂,研究了经分子识别作用后的酸性红B光催化降解行为,考察了影响光催化降解的条件因素。研究结果表明:对于20 mg/L的酸性红B,经β-环糊精分子识别后酸性红B的光催化降解效率可以提高24%;β-环糊精浓度、pH值和TiO2剂量对酸性红B的光催化降解速率有明显的影响。分子识别作用下酸性红B光催化降解的增强效应主要源于β-环糊精能有效促进酸性红B在TiO2表面的吸附。     

V掺杂TiO2纳米粒子的制备及其光催化研究

溶胶-凝胶法制备5at.％V掺杂的TiO2和纯TiO2,然后在500℃煅烧6 h。 XRD谱图显示,样品均是锐钛矿型TiO2,还有一些无定型成分,平均晶粒大小分别为6.8 nm和9.7 nm。 TEM照片显示的纳米粒子大小分别在8.0-18.7 nm和21.6-30.2 nm范围内,比XRD计算结果大,这是因为样品未能充分分散所造成。 EDS谱图显示V的掺杂量是6.5at.％,红外光谱也证实V元素的存在。拉曼光谱表明, V元素均匀地分散在TiO2中。 Rh. B的光催化降解实验表明, V掺杂TiO2的光催化效率比纯TiO2低,这是由于较高的掺杂浓度导致电子-空穴复合中心增加,从而降低光催化效率。     

Photoelectrochemical study of oxygen deficient TiO2 nanowire arrays with CdS quantum dot sensitization

Oxygen-deficient TiO(2) nanowires show substantially increased donor density due to an increase in oxygen vacancies introduced intentionally by thermal treatment in ammonia, vacuum, or hydrogen. By coupling oxygen-deficient TiO(2) nanowires with CdS quantum dots, a significant enhancement in their photoactivities was observed in the entire wavelength region from 350 to 550 nm. These new nanocomposites hold great promise for solar hydrogen generation.     

Visible-light-induced photoelectrochemical behaviors of Fe-modified TiO2 nanotube arrays

Fe-modified TiO(2) nanotube arrays (TiO(2) NTs) were prepared by annealing amorphous TiO(2) NTs whose surface was covered with Fe(3+) by a dip-coating procedure, and characterized by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and UV-visible reflectance spectroscopy. The photoelectrochemical properties were evaluated by the photocurrent response and photoelectrocatalytic (PEC) degradation of methylene orange (MO) and 4-chlorophenol in water under visible-light irradiation (λ > 420 nm). The results showed that a Fe-modified TiO(2) NTs electrode exhibited a larger photocurrent response and higher PEC activity for the degradation of organic pollutants than a pure TiO(2) NTs electrode. At a bias potential of 0.4 V, the photocurrent response of a 0.5 M Fe-modified TiO(2) NTs electrode exceeded that of a pure TiO(2) NTs electrode by a factor of about 10, and the PEC degradation rates of MO and 4-chlorophenol on a 0.5 M Fe-modified TiO(2) NTs electrode exceeded those on a pure TiO(2) NTs electrode by a factor of about 2.5. The larger photocurrent response and higher PEC activity of Fe-modified TiO(2) NTs could be attributed to the enhancement of separation of charge-carriers at the external electric field and the extension of the light response range of TiO(2) to the visible-light region with the narrowing of the band gap.     

Reduced charge recombination in a co-sensitized quantum dot solar cell with two different sizes of CdSe quantum dot

An efficient photoelectrode is fabricated by sequentially assembling 2.5 nm and 3.5 nm CdSe quantum dots (QDs) onto a TiO2 film. As revealed by UV-vis absorption spectroscopy, two sizes of CdSe QD can be effectively adsorbed on the TiO2 film. With a broader light absorption range and better coverage of CdSe QDs on the TiO2 film, a power conversion efficiency of 1.26% has been achieved for the TiO2/CdSe QD (2.5 nm)/CdSe QD (3.5 nm) cell under the illumination of one Sun (AM 1.5G, 100 mW cm(-2)). Electrochemical impedance spectroscopy shows that the electron lifetime for the device based on TiO2/CdSe QD (2.5 nm)/CdSe QD (3.5 nm) is longer than that for devices based on TiO2/CdSe QD (2.5 nm) and TiO2/CdSe QD (3.5 nm), indicating that the charge recombination at the interface is reduced by sensitizing with two kinds of CdSe QDs.     

木质素/TiO2复合纳米颗粒的制备及其防晒应用

采用一步水热酯化反应将不同来源的木质素紧密包覆在二氧化钛表面,得到木质素改性二氧化钛复合纳米颗粒。DLS分析显示经木质素包覆改性后,二氧化钛粒径增大8～12 nm;TG分析测得复合纳米颗粒中木质素包覆量(质量分数)为7.6%～9.0%;TEM及XPS测试结果证实:木质素的羧基与二氧化钛表面羟基之间发生了酯化反应,从而使木质素紧密包覆在二氧化钛表面。在此基础上,将木质素改性二氧化钛复合纳米颗粒作为唯一防晒组分制备了防晒霜,测定了防晒指数SPF值并与只含二氧化钛的防晒霜进行了性能对比。结果显示:添加质量分数为10%和20%的溶剂型木质素改性二氧化钛后防晒霜的SPF值分别为43.88和72.83,明显高于添加二氧化钛的防晒霜,且肤感更优,达到日常防晒的要求。在此基础上探讨了木质素改性强化二氧化钛紫外防护性能的机理。     

TiO_2/SiO_2复合纳米纤维的GQDs改性及其对甲醛的可见光催化降解性能

采用静电纺丝法合成了TiO_2/SiO_2柔性复合纳米纤维膜,而后对其进行石墨烯量子点(GQDs)改性,制备了GQDs/TiO_2-SiO_2复合纳米纤维,其中GQDs用水热法合成。用X射线衍射仪(XRD)、电子万能材料试验机、扫描电子显微镜(SEM)、紫外-可见分光光度计(UV-Vis)对其物相组成、力学性能、微观形貌以及光催化性能进行了表征。结果表明:尺寸在7 nm~15 nm之间的GQDs松散沉积在直径为200 nm~400 nm的TiO_2/SiO_2纳米纤维上,纤维连续性好,复合薄膜有较好的力学性能;TiO_2的结晶较好,为锐钛矿相;GQDs复合后将TiO_2的本征吸收从390 nm左右延伸到了420 nm左右,拓宽了TiO_2的吸收范围。在可见光催化降解中,初始浓度为0.32 mg/m~3的甲醛气体110 min后的降解效率达到70%。     

激光闪光光解技术研究Pt^4＋掺杂提高TiO2光催化活性机制

通过用纳秒激光直接激发Pt^4＋掺杂的TiO2透明溶胶体系，研究了440nm处O^-吸收光谱的衰减过程．O^-是被捕获的正空穴的信号，是光催化反应过程中产生OH^＊自由基的决定影响因素．OH^＊浓度和衰减速度决定了光催化反应的效率．研究表明，O^-的寿命可以长达几十微秒．利用纳秒激光闪光光解的研究结果阐明了Pt^4＋掺杂显著提高TiO2光催化活性的机制．     

Nanostructure control of graphene-composited TiO2 by a one-step solvothermal approach for high performance dye-sensitized solar cells

We present a one-step solvothermal approach to prepare uniform graphene-TiO(2) nanocomposites with delicately controlled TiO(2) nanostructures, including ultra-small 2 nm nanoparticles, 12 nm nanoparticles and nanorods. Using three composites as photoanode materials, the effect of nanostructure of graphene-composited TiO(2) on the performance of dye-sensitized solar cells was investigated, and results showed that the ultra-small 2 nm TiO(2)-graphene composite based photoanode exhibited the highest power conversion efficiency of 7.25%.     

掺氮TiO_2的制备与光谱分析

用硫酸钛与氨水反应得到TiO2前体,煅烧后制得掺氮TiO2粉体,研究了不同温度和加热时间下掺氮TiO2的XPS、FTIR和紫外可见光谱,结果表明,掺氮TiO2在400℃下加热1 h,所得粉体是锐钛矿相结构,与未掺杂TiO2相比,吸收边红移22 nm,对400~510 nm的可见光有一定的吸收率。氮的掺杂不仅使TiO2带隙变小,而且有助于氧空位的形成。     

光子晶体光局域效应提高TiO_2吸光率的应用及规律研究进展

半导体TiO_2只能吸收波长小于387 nm的紫外光,实际应用受到限制,近年来出现的新型材料——光子晶体在提高光吸收率方面引起研究者的兴趣。综述利用光子晶体提高TiO_2光吸收率的研究进展,重点阐述光子晶体在太阳能电池、光催化降解有机物和光解水制氢领域的应用,介绍当前探究光子晶体提高光吸收率的规律。总体来说,光子晶体提高光收率效果显著,但对其规律的认识不足,了解光子晶体的应用进展和规律研究现状,对高效光催化剂的制备具有重要意义。     

LDO负载纳米二氧化钛复合物的制备及其光催化性能研究

以碳酸根型镁铝层状双氢氧化物(LDH)为载体,采用溶胶-凝胶法利用酞酸丁酯水解负载纳米TiO2于LDH片层获得TiO2/LDH前驱体,通过低温焙烧前驱体获得纳米二氧化钛/层状双金属氧化物复合物(TiO2/LDO).以亚甲基蓝溶液模拟染料污染物,在波长291 nm紫外光条件下测定吸光度,评价了光催化剂不同投加量,体系pH值以及光照时间条件下对亚甲基蓝降解率的影响,研究了TiO2/LDO的光催化性能.结果表明:通过溶胶-凝胶法可以获得高分散纳米级(<10 nm)TiO2负载型TiO2/LDH复合物,TiO2/LDH中TiO2负载率达8.01wt%(质量分数);TiO2/LDO的光催化性能较纯LDO高,TiO2负载于LDO层板对亚甲基蓝具有协同催化作用;在pH值为9的80 mL亚甲基蓝溶液(浓度为5 mg/L)中投入0.20 g TiO2/LDO,催化反应8 h后降解率高达81.7%,TiO2/LDO对亚甲基蓝溶液的光催化反应符合一级动力学方程.     

两种合成方式对制备纳米二氧化钛粉体的影响

以钛酸四丁酯为原料,分别通过溶胶-凝胶法和硬脂酸凝胶法制得TiO2前驱体,在450℃煅烧后分别得到粒径在42.4,9.4 nm的混晶纳米TiO2。运用XRD和TEM等方法对TiO2进行表征,探讨了两种合成方式对纳米TiO2粒径大小及TiO2晶型转变温度的影响。结果表明,以硬脂酸凝胶法合成的纳米TiO2纯度高、粒径小,且晶型转变温度低,这是由于晶粒细化后晶型转变温度降低的缘故。     

介孔TiO_2中空微球的制备及其光催化性能研究

采用双模板辅助,在水热条件下制备出TiO_2@C复合微球,高温煅烧除去模板后得到介孔TiO_2中空微球。利用XRD、SEM、TEM和氮气吸脱-脱附仪对所制备样品的晶体结构、形貌及孔结构进行表征。所制备的介孔TiO_2中空微球属于锐钛矿型,是由大量直径为15.31 nm的介孔初级微球堆积而成,整体微球直径约为360 nm,加入葡萄糖作为模板剂能使孔道结构变得有序。以罗丹明B为模拟污染物,探讨了介孔TiO_2中空微球光催化降解罗丹明B的性能。结果表明,在20 W紫外光照射下,50 mg介孔TiO_2中空微球在30 min内可使初始质量浓度为10 mg/L的罗丹明B完全降解,重复使用11次,在50 min时的降解率仍可达89.5%。     

二氧化钛包裹碘单质(I_2/TiO_2)制备及其光催化降解苯酚

采用水热法,以Ti(SO4)2为钛源,KIO3为掺碘剂制备了具有高可见光活性,高稳定性的二氧化钛包裹碘单质(I2/TiO2)光催化剂.利用X射线光电子能谱(XPS)、X射线晶体粉末衍射(XRD)、透射电子显微镜(TEM)和紫外可见漫反射光谱(DRS)等表征手段对样品进行表征.结果表明,I2/TiO2中除含有锐钛矿相二氧化钛外、还含有碘单质和碘酸;I2/TiO2粒径大小为45 nm左右;在波长384 nm至700 nm范围内,该催化剂有强烈的吸收.探讨了该催化剂的形成过程和可见光催化机理.以苯酚降解反应为探针,测定了I2/TiO2光催化活性.结果显示:在全谱光源照射下I2/TiO2活性略高于P25,在可见光范围内其活性是P25的3倍多.确定了降解苯酚的最佳条件:全谱光源照射,投加量为0.5 g/L,苯酚浓度大于10 mg/L,溶液pH为3.2.I2/TiO2重复使用4次后,催化活性没有明显下降.     

Effect of surface microstructure of TiO₂ film from micro-arc oxidation on its photocatalytic activity: a HRTEM study

Photocatalysis is a reaction that happens on the surface of catalysts around only several atomic layers. Therefore, the microstructure beneath the surface plays a key role for the improvement of photocatalytic property. In this paper, the microstructural variation of the TiO(2) film from micro-arc oxidation (MAO) was characterized by using a high resolution transmission electron microscopy (HRTEM), and the relationship between microstructures and photocatalytic activity was studied. The results revealed that: 1) The microstructural variation from the surface to the interior in the as-prepared film is as follows: an amorphous layer with thickness around 10-20 nm, an intermediate zone consisting of amorphous, anatase and few rutile TiO(2) phases with grain size about 12 nm, then the main structure consisting of anatase and few rutile TiO(2) phases with grain size around 20 nm. This variation was formed due to temperature gradient during MAO. 2) When the TiO(2) film was annealed at 450 °C for 12 h, the amorphous layer disappeared and crystallized into fine anatase grains, and, simultaneously, the grain size in the intermediate layer grew obviously from 12 nm into 18 nm, and the interior portion from 20 nm into 30 nm. 3) The photocatalysis experiments exhibited that photocatalytic activity of the post-annealed TiO(2) film was enhanced to more than twice that of the as-prepared TiO(2) film. Therefore, we propose that the crystallization of amorphous phase beneath the surface plays a key role for the improvement of its photocatalytic property.     

Preparation of TiO2-Pt hybrid nanofibers and their application for sensitive hydrazine detection

The TiO2-Pt hybrid nanofibers with an average dia. 72.6 nm were fabricated by electrospinning poly(vinylpyrrolidone)-ethanol solution containing platinum acetate and titanium tetraisopropoxide, followed by calcination in air at 500 °C for 3 h. High resolution TEM showed that Pt nanoparticles with an average diameter of ～2 nm were well dispersed in the anatase TiO2 nanofibers. Compared to pristine TiO2 nanofibers (average dia. 67.7 nm), the incorporation of Pt nanoparticles into TiO2 nanofibers can greatly enhance the oxidation of hydrazine in neutral solution. The amperometric hydrazine sensor, using the as-prepared TiO2-Pt hybrid nanofibers as the electrochemical catalyst, shows a wide linear range (up to 1.03 mM), a good limit of detection (0.142 μM), and a high sensitivity of 44.42 μA mM(-1) cm(-2). In addition, the excellent anti-interference property, free of matrix effect from real water samples and good reproducibility make the developed hydrazine sensor promising for real applications.     

Novel hollow mesoporous 1D TiO2 nanofibers as photovoltaic and photocatalytic materials

Hollow mesoporous one dimensional (1D) TiO(2) nanofibers are successfully prepared by co-axial electrospinning of a titanium tetraisopropoxide (TTIP) solution with two immiscible polymers; polyethylene oxide (PEO) and polyvinylpyrrolidone (PVP) using a core-shell spinneret, followed by annealing at 450 °C. The annealed mesoporous TiO(2) nanofibers are found to having a hollow structure with an average diameter of 130 nm. Measurements using the Brunauer-Emmett-Teller (BET) method reveal that hollow mesoporous TiO(2) nanofibers possess a high surface area of 118 m(2) g(-1) with two types of mesopores; 3.2 nm and 5.4 nm that resulted from gaseous removal of PEO and PVP respectively during annealing. With hollow mesoporous TiO(2) nanofibers as the photoelectrode in dye sensitized solar cells (DSSC), the solar-to-current conversion efficiency (η) and short circuit current (J(sc)) are measured as 5.6% and 10.38 mA cm(-2) respectively, which are higher than those of DSSC made using regular TiO(2) nanofibers under identical conditions (η = 4.2%, J(sc) = 8.99 mA cm(-2)). The improvement in the conversion efficiency is mainly attributed to the higher surface area and mesoporous TiO(2) nanostructure. It facilitates the adsorption of more dye molecules and also promotes the incident photon to electron conversion. Hollow mesoporous TiO(2) nanofibers with close packing of grains and crystals intergrown with each other demonstrate faster electron diffusion, and longer electron recombination time than regular TiO(2) nanofibers as well as P25 nanoparticles. The surface effect of hollow mesoporous TiO(2) nanofibers as a photocatalyst for the degradation of rhodamine dye was also investigated. The kinetic study shows that the hollow mesoporous surface of the TiO(2) nanofibers influenced its interactions with the dye, and resulted in an increased catalytic activity over P25 TiO(2) nanocatalysts.     

静电纺丝制备TiO2纳米纤维的光催化性能

纳米TiO2材料在光催化、抗菌等方面有着广泛应用。采用尺寸为20～30nm的TiO2颗粒与聚乙烯吡咯烷酮（PVP）的醇溶液混合制得纺丝液,通过静电纺丝技术与烧结工艺,制得TiO2纳米纤维。采用能谱仪、X射线衍射、扫描电子显微镜和投射电子显微镜等分析手段对样品进行了表征,与采用溶胶–凝胶结合静电纺丝技术得到的TiO2纳米纤维进行了形貌对比,并通过亚甲基蓝降解实验研究其光催化性能。结果表明：以TiO2纳米颗粒为原料通过静电纺丝技术制备的TiO2纳米纤维,主要为多晶相的锐钛矿结构,直径为150～250 nm,长度大于20μm,与溶胶–凝胶结合静电纺丝技术制得的TiO2纳米纤维相比,直径分布更为均匀。在紫外光照射90min时,对浓度为4mg/L的亚甲基蓝溶液的分解率为72%,具有较好的光催化效率。     

不同粒径二氧化钛对顺丁橡胶/二氧化钛复合材料性能的影响

分别采用7 种不同粒径的二氧化钛制备了顺丁橡胶/二氧化钛复合材料,通过核磁共振交联密度仪、橡胶加工分析仪等研究了二氧化钛的粒径对其硫化特性、交联密度、物理机械性能和动态力学性能的影响。结果表明,在顺丁橡胶中填充纳米级二氧化钛后,复合材料的正硫化时间比填充微米级二氧化钛者明显延长,且前者的拉伸强度可达到纯顺丁橡胶的6 倍; 当二氧化钛的粒径为20 nm 和50 nm时,顺丁橡胶/二氧化钛复合材料的损耗因子、储能模量和损耗模量要远大于填充微米级填料者,且呈现出明显的Payne 效应。