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1.
利用飞秒瞬态吸收光谱和基于飞秒荧光上转换技术的飞秒时间分辨荧光动力学对T4有机染料敏化的Al 2O 3薄膜和TiO 2薄膜中的激发态过程进行了研究。对这两种敏化薄膜中的荧光动力学进行了多指数拟合。所得到T4染料敏化TiO 2薄膜中的电子注入效率为93%。此外,通过静态非均匀电子耦合模型拟合,得到T4敏化TiO 2薄膜中的电子转移速率为1.17 ps -1。 相似文献
2.
用Gaussian09程序包的密度泛函理论DFT方法,在BP86/6-311++g(d,p)水平上对O 2, TiO和TiO 2 分子进行了优化.得到该系列分子的基态电子态分别为:O 2(X 3Σ g), TiO(X 3Π g), TiO 2(X 1 A 1), TiO 2分子的稳定构型为C 2v构型. 用Murrell-Sorbie势能函数对TiO和O 2分子的扫描势能点进行拟合, 其扫描点都与四参数Murrell-Sorbie函数拟合曲线符合得很好,在此基础上推导出它们的光谱数据和力常数. 用多体项展开理论导出TiO 2分子的全空间解析势能函数,在固定键角∠OTiO=110.5° 的情况下, R Ti-O = 0.1652 nm处存在一个深度为15.09 eV的势阱, 表明在该处易形成稳定的TiO 2分子.
关键词:
TiO
2和TiO 2')" href="#">O 2和TiO 2
密度泛函理论
势能函数 相似文献
3.
采用基于密度泛函理论的平面波超软赝势方法研究了 纯的和不同高氧空位浓度金红石型TiO 2-x ( x=0, 0.083, 0.125, 0.167, 0.25)超胞的能带结构分布、态密度分布.同时, 采用局域密度近似+ U方法调准了带隙.结果表明, 高氧空位浓度越高, 金红石型TiO 2的最小带隙越变窄、电子有效质量越减小, 自由电子浓度越高, 电子迁移率越低、电导率越低.计算结果与实验结果的变化趋势相符合.
关键词:
高氧空位
2')" href="#">金红石型TiO 2
电导率
第一性原理 相似文献
4.
本文采用基于周期性密度泛函理论研究了Cu/N表面沉积共掺杂对锐钛矿相TiO2(001)面的修饰作用.计算了Cu在不同位置掺杂TiO2(101)面和(001)面的形成能,并在此基础上计算N不同位置掺杂TiO2(001)面及Cu/TiO2(001)面的形成能,通过形成能的比较获得了表面共掺杂的最优化结构.在此基础上计算了最稳定结构的能带结构及态密度,并与S单掺杂TiO2(001)面最稳定结构进行了对比.通过对结果的分析发现:Cu/N在(001)表面的沉积共掺杂有效降低了TiO2的禁带宽度,并在表面形成CuO2相,更利于提高其光催化活性. 相似文献
5.
We investigated the effects of using different thicknesses of pure and vanadium-doped thin films of TiO_2 as the electron transport layer in the inverted configuration of organic photovoltaic cells based on poly(3-hexylthiophene) P3HT:[6-6] phenyl-(6) butyric acid methyl ester(PCBM). 1% vanadium-doped TiO_2nanoparticles were synthesized via the solvothermal method. Crystalline structure, morphology, and optical properties of pure and vanadium-doped TiO_2 thin films were studied by different techniques such as x-ray diffraction, scanning electron microscopy, transmittance electron microscopy, and UV–visible transmission spectrum. The doctor blade method which is compatible with roll-2-roll printing was used for deposition of pure and vanadium-doped TiO_2 thin films with thicknesses of 30 nm and 60 nm. The final results revealed that the best thickness of TiO_2 thin films for our fabricated cells was 30 nm. The cell with vanadium-doped TiO_2 thin film showed slightly higher power conversion efficiency and great J_(sc) of 10.7 mA/cm~2 compared with its pure counterpart. In the cells using 60 nm pure and vanadium-doped TiO_2 layers, the cell using the doped layer showed much higher efficiency. It is remarkable that the external quantum efficiency of vanadium-doped TiO_2 thin film was better in all wavelengths. 相似文献
6.
在室温条件下,利用超声波辐照方法合成了一系列具有大比表面积的介孔结构TiO 2光催化剂。应用N 2-物理吸附、X射线粉末衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)等手段对合成的样品进行了表征。考察了超声波强度、发射时间对TiO 2的结晶度、比表面积、孔体积、孔径等物理结构的影响,并提出了超声波辐照下TiO 2的介孔结构的形成机理。以λ=365 nm的紫外光为光源,评价了该系列催化剂光催化降解染料甲基橙的性能。结果表明超声波功率的增加将增加TiO 2的结晶度和孔径,并使其晶粒发生细化,提高催化剂的分散性。声化学合成的样品具有较高的光催化活性,其主要原因是超声波辐照方法合成的TiO 2具有较高的结晶度和较大的比表面积和孔体积。 相似文献
7.
本文采用第一性原理中基于密度泛函理论(DFT)的广义梯度近似(GGA)方法, 设计了一种新的(TiO 2) 12 量子环结构, 研究了它的几何结构、平均结合能及电子云分布等属性. 在此新型结构的基础上, 分别采用过渡金属化合物MoS 2, MoSe 2, MoTe 2, WS 2, WSe 2和WTe 2进行掺杂, 并分析了掺杂后体系的几何结构及电子属性(如平均结合能、能级结构、HOMO-LUMO轨道电子云密度分布和电子态密度等). 计算结果表明: (TiO 2) 12量子环直径为1.059 nm, 呈中心对称分布, 且所有原子组成一个二维平面结构, 使其几何结构比较稳定, 另外该量子环HOMO-LUMO轨道电子云分布均匀, 且能隙为3.17 eV, 与半导体材料TiO 2晶体的能隙的实验值(3.2 eV)非常接近. 掺杂后量子环的能隙均大幅减小, 其中WTe 2的掺杂结果能隙最小, 仅为0.61 eV, MoTe 2的掺杂结果能隙最大, 为1.16 eV, 也比掺杂前减小约2.0 eV. 其他掺杂结果的能隙都在1 eV左右, 变化不大. 这个能隙的TiO 2可以利用大部分的太阳光能, 使TiO 2具有更为广泛的应用. 相似文献
8.
Recently, the high pressure study on the TiO_2 nanomaterials has attracted considerable attention due to the typical crystal structure and the fascinating properties of TiO_2 with nanoscale sizes. In this paper, we briefly review the recent progress in the high pressure phase transitions of TiO_2 nanomaterials. We discuss the size effects and morphology effects on the high pressure phase transitions of TiO_2 nanomaterials with different particle sizes, morphologies, and microstructures. Several typical pressure-induced structural phase transitions in TiO_2 nanomaterials are presented, including size-dependent phase transition selectivity in nanoparticles, morphology-tuned phase transition in nanowires, nanosheets,and nanoporous materials, and pressure-induced amorphization(PIA) and polyamorphism in ultrafine nanoparticles and TiO_2-B nanoribbons. Various TiO_2 nanostructural materials with high pressure structures are prepared successfully by high pressure treatment of the corresponding crystal nanomaterials, such as amorphous TiO_2 nanoribbons, α-PbO_2-type TiO_2 nanowires, nanosheets, and nanoporous materials. These studies suggest that the high pressure phase transitions of TiO_2 nanomaterials depend on the nanosize, morphology, interface energy, and microstructure. The diversity of high pressure behaviors of TiO_2 nanomaterials provides a new insight into the properties of nanomaterials, and paves a way for preparing new nanomaterials with novel high pressure structures and properties for various applications. 相似文献
9.
The morphology and chemical characteristics of the surface and the interface of TiO 2–muscovite nanocomposites were studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Our results clearly showed that TiO 2 grains formed on the TiO 2 thin film surface, whereas the presence of TiO 2 grains on the interface between TiO 2 thin films and the muscovite substrates was not obvious. While euhedral rutile grains were found in samples doped with Zn ions, none were found in samples doped with Sn ions. The XPS results showed that cations present in the muscovite substrates diffused into the TiO 2 thin films. Etching measurements revealed that diffusion abilities of cation impurities varied: Si and Al diffused more easily than K. The observed differences in chemical composition and oxidation of the elements, especially on the surface and the subsurface, may influence the different crystallization behaviors of elements in TiO 2 thin films and the different active degree of elements diffusing from muscovite substrates. 相似文献
10.
为了研究锌卟啉/TiO 2复合光催化剂的光催化效率及电子转移问题, 本文采用溶胶凝胶法制备了锌卟啉/TiO 2的混合光催化材料, 并利用紫外可见光谱、电子顺磁共振谱对锌卟啉/TiO 2复合光催化剂进行了表征与分析. 采用溶胶凝胶法制备了锌卟啉-TiO 2的混合光催化材料, 通过比较纯P25型TiO 2和掺入质量比分别为0.2%, 0.5%, 0.9%锌卟啉敏化剂的锌卟啉/TiO 2混合光催化材料的紫外可见光谱图可知, 加入适量锌卟啉敏化剂可提高TiO 2对甲基橙溶液的降解效率, 过多的掺入锌卟啉敏化剂会导致TiO 2表面被敏化剂覆盖, 从而影响了其对光子的吸收, 降低TiO 2的光催化效率, 降低TiO 2的光降解率, 甚至低于纯TiO 2的光降解率. 应用电子顺磁共振技术对锌卟啉敏化TiO 2光催化剂的光催化机理进行了合理的解释, 当使用紫外可见光源对粉末样品进行辐照时, 锌卟啉受光辐照产生的激发态电子促进具有强氧化性的Ti 3+和超氧根自由基的生成, 从而有效的促进了光生空穴-电子对的分离, 提高了TiO 2的光催化性能. 相似文献
11.
采用密度泛函理论(DFT)体系广义梯度近似(GGA)第一性原理平面波超软赝势方法,分析锐钛矿型TiO 2(101)表面吸附NO 2分子光学气敏传感的微观机理.结果表明:Cu和Cr原子易于掺入TiO 2(101)表面,掺杂表面能稳定地吸附NO 2分子且吸附后光学性质发生显著变化.表面吸附NO 2分子后,Cu掺杂TiO 2(101)表面对分子的吸附能最大,吸附后结构更稳定,分子与表面的距离最短.通过分析差分电荷密度和电荷布居数发现,NO 2分子与基底表面间发生电荷转移,转移电子数目:Cu掺杂表面 > Cr掺杂表面 > 无掺杂表面.对比吸收光谱和反射光谱发现,在Cu掺杂表面吸附分子后,光学性质变化最明显,说明表面与吸附分子间氧化还原能力是决定光学气敏传感性能的核心因素.在过渡金属中,Cu与Cr都有4s价电子结构,其4s电子降低了材料表面氧空位的氧化性,增加了其还原性.对于氧化性气体,可以提升表面与分子的氧化还原作用,而Cu的4s电子更加活泼,从而光学气敏传感特性更加明显.因此,Cu掺杂的TiO 2对氧化性气体是一种较好的光学气敏传感材料. 相似文献
12.
An inverted structure of polymer solar cells based on Poly(3-hexylthiophene)(P3HT):[6-6] Phenyl-(6) butyric acid methyl ester(PCBM) with using thin films of TiO_2 nanotubes and nanoparticles as an efficient cathode buffer layer is developed. A total of three cells employing TiO_2 thin films with different thickness values are fabricated. Two cells use layers of TiO_2 nanotubes prepared via self-organized electrochemical-anodizing leading to thickness values of 203 and 423.7 nm, while the other cell uses only a simple sol–gel synthesized TiO_2 thin film of nanoparticles with a thickness of 100 nm as electron transport layer. Experimental results demonstrate that TiO_2 nanotubes with these thickness values are inefficient as the power conversion efficiency of the cell using 100-nm TiO_2 thin film is 1.55%, which is more than the best power conversion efficiency of other cells. This can be a result of the weakness of the electrochemical anodizing method to grow nanotubes with lower thickness values. In fact as the TiO_2 nanotubes grow in length the series resistance(Rs) between the active polymer layer and electron transport layer increases, meanwhile the fill factor of cells falls dramatically which finally downgrades the power conversion efficiency of the cells as the fill factor falls. 相似文献
13.
By means of X-ray diffraction, BET nitrogen adsorption, UV-Vis-NIR transmission spectroscopy, transmission electron microscope, scanning electron microscope, X-ray photoelectron spectroscopy and photodegradation of methylene blue, effects of Ag doping on the microstructure and photocatalytic activity of TiO 2 films prepared by sol–gel method were studied. It is found that with a suitable amount (2–4 mol%), the Ag dopant increases the photocatalytic activity of TiO 2 films. The mechanism can be attributed to that (1) anatase grain sizes decrease with Ag doping and the specific surface areas of doped TiO 2 films increase, the charge transfer in TiO 2 films is promoted; (2) by enhancing the electron–hole pairs separation and inhibiting their recombination, the Ag dopant enhances the charge pair separation efficiency for doped TiO 2 films. 相似文献
14.
In an attempt to identify the fundamental processes that influence ion transport through metallic surface layers, we have studied the transmission of O + ions through discontinuous Au films adsorbed on TiO 2(110). A low energy (< 10 eV) O + ion beam is generated via electron stimulated desorption when an Au-dosed TiO 2(110) substrate is bombarded with a focused 250 eV electron beam. Low energy ion scattering data indicate that Au evaporated under ultrahigh vacuum conditions at 300 K forms three-dimensional clusters on TiO 2(110). As the Au coverage increases, the formation of Au clusters on TiO 2(110) blocks a fraction of the TiO 2 surface and the O + yield is attenuated. However, for high coverages (≥30% Au covered substrate) the O + signal decreases at a faster rate than the TiO 2 open area fraction. We attribute the attenuation of the O + yield for high Au coverages mainly to blocking of O + by Au clusters, to deflection of trajectories by the image force between ions and Au clusters, and to charge transfer between desorbing O + and neighboring Au clusters. 相似文献
15.
在实验上, W掺杂量在0.02083–0.04167的范围内时, 有关掺杂体系的电导率影响的研究有两种相悖的结论. 为解决这个问题, 本文采用第一性原理平面波模守恒赝势方法, 首先构建了两种Ti 0.97917W 0.02083O 2 和Ti 0.95833W 0.04167O 2 超胞模型, 分别对这两种模型进行了几何结构优化、能带结构分布和态密度分布计算. 同时还计算了掺杂体系的电子浓度、有效质量、迁移率和电导率. 计算结果表明, 在电子自旋极化或电子非自旋极化的条件下, W掺杂浓度越大、掺杂体系的电子浓度越大、有效质量越小、迁移率越小、电导率越大、导电性能越强. 由电离能和Bohr半径分析进一步证实了Ti 0.95833W 0.04167O 2 超胞的导电性能优于Ti 0.97917W 0.02083O 2 超胞. 为了研究掺杂体系的结构稳定性和形成能, 又分别构建了Ti 0.96875W 0.03125O 2, Ti 0.9375W 0.0625O 2两种超胞模型, 几何结构优化后进行了计算, 结果表明, 在电子自旋极化或电子非自旋极化的条件下, 在W掺杂量为0.02083–0.04167的范围内, W掺杂浓度越大、掺杂体系的总能量越高、稳定性越差、 形成能越大、掺杂越困难. 将掺杂体系的晶格常数与纯的锐钛矿TiO 2相比较, 发现沿a轴方向的晶格常数变大、沿c轴方向的晶格常数变小、掺杂体系的体积变大, 计算结果与实验结果相符合. 在电子自旋极化的条件下, 掺杂体系形成了半金属化的室温铁磁性稀磁半导体. 相似文献
16.
通过水解TiCl 4制备了锐钛矿结构TiO 2纳米粒子, 并用时间分辨荧光光谱研究了5(6)CFL(5(6)-Carboxyfluorescein, 简称5(6)CFL)染料敏化TiO 2纳米粒子体系的光致电子转移动力学. 5(6)CFL染料敏化TiO 2纳米粒子能形成电荷转移复合物, 这归因于染料分子的激发电子态波函数Ψ(D *)与电荷分离态波函数Ψ(D + +e -)之间的耦合作用. 当激发5(6)CFL染料敏化TiO 2纳米粒子体系时, 电子以两种不同方式注入TiO 2纳米粒子导带: 第一, 通过5(6)CFL染料分子的激发态注入; 第二, 从电荷转移复合物(5(6)CFL/TiO 2)直接注入. 时间分辨荧光光谱表明, 在水溶液中纯5(6)CFL染料的荧光以寿命为τ 1=41 ps (74.4%) 和τ 2=3.22 ns (25.6%) 的双e指数衰减, 而5(6)CFL染料敏化TiO 2纳米粒子体系的荧光分别以时间常数为τ 1=44 ps (90.4%), τ 2=478 ps (8.6%) 和τ 3=2.41 ns (1.0%) 的三e指数衰减. 本文的研究工作能够为染料敏化太阳能电池的光致电子转移机理提供有价值的参考. 相似文献
17.
采用基于密度泛函理论加U的计算方法,研究了Ce和O空位单(共)掺杂锐钛矿相TiO_2的电子结构和光吸收性质.计算结果表明,Ce和O空位共掺杂TiO_2的带隙中出现了杂质能级,且带隙窄化为2.67 eV,明显比纯TiO_2和Ce,O空位单掺杂TiO_2的要小,因而可提高TiO_2对可见光的响应能力,使TiO_2的光吸收范围增加.光吸收谱显示,掺杂后TiO_2的光吸收边发生了显著红移;在400.0—677.1 nm的可见光区,共掺杂体系的光吸收强度显著高于纯TiO_2和Ce单掺杂TiO_2,而略低于O空位单掺杂TiO_2.此外,Ce掺杂TiO_2中引入O空位后,TiO_2的导带边从-0.27 eV变化为-0.32 eV,这表明TiO_2的导带边的还原能力得到了加强.计算结果为Ce和O空位共掺杂TiO_2在可见光光解水方面的进一步研究提供了有力的理论依据. 相似文献
18.
在密度泛函理论的基础上,系统地研究了Cu/N(共)掺杂的TiO 2/MoS 2异质结体系的几何结构、电子结构和光学性质.计算发现,TiO 2/MoS 2异质结的带隙相比于纯的TiO 2(101)表面明显变小,Cu/N(共)掺杂TiO 2/MoS 2异质结体系的禁带宽度也明显地减小,这导致光子激发能量的降低和光吸收能力的提高.通过计算Cu/N(共)掺杂TiO 2/MoS 2的差分电荷密度,发现光生电子与空穴积累在掺杂后的TiO 2(101)表面和单层MoS 2之间,这表明掺杂杂质体系可以有效地抑制光生电子-空穴对的复合.此外,我们计算了在不同压力下TiO 2/MoS 2异质结的几何、电子和光学性质,发现适当增加压力可以有效提高异质结的光吸收性能.本文结果表明,Cu/N(共)掺杂TiO 2/MoS 2异质结和对TiO 2/MoS 2异质结加压都能有效地提高材料的光学性能. 相似文献
19.
S-doped TiO 2 (S-TiO 2) photocatalyst was synthesized by sol–gel method with tetrabutyl titanate and thiourea as precursor. S-TiO 2 was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV–vis absorption spectroscopy, transmission electron microscopy (TEM) and the photocatalytic activity was evaluated by 1-naphthol-5-sulfonic acid (L-acid) under UV, visible light and solar light radiation. The results showed that doped S could improve photoabsorption property of TiO 2 in the visible region, leading the increase in the photocatalytical activity of TiO 2. The average particle size of the S-TiO2 photocatalyst is about 10 nm. The S-TiO2-4 photocatalyst contains 100% anatase crystalline phase of TiO2. In the S-TiO2-4 photocatalyst, S does not exist independently, but is incorporated into the crystal lattice of TiO2. In the inner crystal lattice of the S-TiO2-4 photocatalyst, S as S2− replaces O in TiO2, while on the surface of crystal lattice, S exists as S4+ and S6+. The photocatalytical activity of S-TiO2-4 photocatalyst for the photodegradation of L-acid is better than that of pure TiO2. Under the same conditions, the photodegradation efficiency of L-acid for the S-TiO2-4 photocatalyst and the solar light irradiation is 85.1%, while it is only 26.4% for pure TiO2. In addition, the final products of the photocatalysis of L-acid using the S-TiO2-4 photocatalyst are not organic compounds with low molecular weight, but the inorganic compounds. 相似文献
20.
利用磁控溅射在重掺硼硅(p+-Si)衬底上分别沉积TiO2薄膜和掺硼的TiO2(Ti O2∶B)薄膜,并经过氧气氛下600℃热处理,由此形成相应的TiO2/p+-Si和TiO2∶B/p+-Si异质结。与Ti O2/p+-Si异质结器件相比,TiO2∶B/p+-Si异质结器件的电致发光有明显的增强。分析认为:TiO2∶B薄膜经过热处理后,B原子进入TiO2晶格的间隙位,引入了额外的氧空位,而氧空位是TiO2/p+-Si异质结器件电致发光的发光中心,所以上述由B掺杂引起的氧空位浓度的增加是TiO2∶B/p+-Si异质结器件电致发光增强的原因。 相似文献
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