半导体纳米颗粒/金属-有机骨架复合光催化体系中的位置效应（英文）

本文采用超快瞬态吸收光谱技术研究了"半导体/金属-有机骨架(MOF)"复合体系中的位置效应.半导体TiO_2纳米颗粒被嵌入或担载于一种典型的MOF材料Cu_3(BTC)_2.通过实时跟踪这两个复合体系中的电子动力学行为,发现半导体与MOF之间形成的界面态可作为高效的电子转移纽带,其效率与二组份的相对位置密切相关,从而导致这两个复合体系光催化CO_2还原的性能差异.本文对"半导体/MOF"复合体系中界面电子转移行为和效应的机理进行了解读,为基于MOF材料的光电化学应用提供了有益的设计思路.     

金属有机框架材料UiO-66-NH2中的铜离子掺杂位置效应及相关动力学研究

本文通过调控合成构建了两种类型的铜离子掺杂金属有机框架(MOF)材料UiO-66-NH₂：一种是Cu²⁺离子浸渍在MOF孔隙中所形成的Cu@UiO-66-NH₂，另一种则是Cu²⁺离子部分取代Zr-O团簇中的Zr⁴⁺离子所形成的双金属中心Cu-UiO-66-NH₂. 超快光谱与动力学表征表明：与未掺杂的MOF相比，这两个铜离子掺杂的MOF体系均促进了与LCCT态相关的弛豫动力学，其促进程度的顺序为Cu-UiO-66-NH₂>Cu@UiO-66-NH₂UiO-66-NH₂；这与它们在可见光光催化析氢活性测试中所观察到的趋势一致. 该工作揭示了Zr基MOF体系中的铜离子掺杂位置效应及相关动力学，表明可在类似MOF体系中通过合理设计金属掺杂的具体位置来促进光致电荷分离、抑制有害的电荷复合，有利于提高MOF体系的光催化性能.     

飞秒瞬态吸收技术研究有机/无机异质结的超快电荷转移过程

本文检测SQ02在氯苯溶液、Al₂O₃薄膜和TiO₂薄膜中的弛豫过程,从而探究SQ02在单分散态和聚集态下的光物理性质以及相应过程中界面电荷转移过程.实验数据表明,单分散态下SQ02 的寿命约为2 ns,但是,在Al₂O₃薄膜中显著减小到21 ps.电子从激发态SQ02转移到TiO₂薄膜的时间约为2.6 ps,摄入电子量约为89.1%,与基于SQ02的染料敏化太阳能电池光电效应的效率相匹配.此外,一些染料和其他染料一起嵌入纳米晶薄膜中的弛豫时间可达到60 ps.由于其远离TiO₂界面,因此不参与界面电荷转移.     

电迁移对Ni/Sn3.0Ag0.5Cu/Au/Pd/Ni-P倒装焊点界面反应的影响

本文研究了150 ℃, 1.0× 10⁴ A/cm²条件下电迁移对Ni/Sn3.0Ag0.5Cu/Au/Pd/Ni-P倒装焊点界面反应的影响. 回流后在solder/Ni和solder/Ni-P的界面上均形成(Cu,Ni)₆Sn₅类型金属间化合物. 时效过程中两端界面化合物都随时间延长而增厚, 且化合物类型都由(Cu,Ni)₆Sn₅转变为(Ni,Cu)₃Sn₄. 电迁移过程中电子的流动方向对Ni-P层的消耗起着决定性作用. 当电子从基板端流向芯片端时, 电迁移促进了Ni-P层的消耗, 600 h后阴极端Ni-P层全部转变为Ni₂SnP层. 阴极界面处由于Ni₂SnP层的存在, 使界面Cu-Sn-Ni三元金属间化合物发生电迁移脱落溶解, 而且由于Ni₂SnP层与Cu焊盘的结合力较差, 在Ni₂SnP/Cu界面处会形成裂纹. 当电子从芯片端流向基板端时, 阳极端Ni-P层并没有发生明显的消耗. 电流拥挤效应导致了阴极芯片端Ni层和Cu焊盘均发生了局部快速溶解, 溶解到钎料中的Cu和Ni原子沿电子运动的方向往阳极运动并在钎料中形成了大量的化合物颗粒. 电迁移过程中(Au,Pd,Ni)Sn₄的聚集具有方向性, 即(Au,Pd,Ni)Sn₄因电流作用而在阳极界面处聚集.     

半导体材料AAl2C4(A=Zn, Cd, Hg; C=S, Se)的电子结构和光学性质

采用基于密度泛函理论的第一性原理方法, 对具有缺陷型黄铜矿结构的半导体材料A^ⅡAl₂C₄^Ⅵ(A=Zn, Cd, Hg; C =S, Se)的构型和电子结构进行研究, 并系统考察了各晶体的光学性质. 对于线性光学性质, 五种晶体在红外区和部分可见光区具有良好的透光性能, 其中HgAl₂S₄和HgAl₂Se₄晶体具有适中的双折射率. 在非线性光学性质方面, 该类晶体倍频效应较强, 理论预测得到的二阶静态倍频系数均较大(>20 pm/V). 体系的倍频效应主要来源于价带顶附近以S/Se 价p轨道为主要成分的能带向含有较多Al/Hg 价p成分的空带之间的跃迁. 通过与已商业化的AgGaC₂晶体光学性质的对比, 结果表明HgAl₂S₄和HgAl₂Se₄是一类性能优良的红外非线性光学晶体材料.     

钙钛矿晶体的电荷复合动力学研究

本文利用紫外吸收光谱和稳态荧光光谱技术结合理论模型，研究了钙钛矿材料CH₃NH₃PbI₃晶体在光激发过程中的电荷复合动力学行为，进而获得晶体的扩散长度. 电荷载体的扩散长度是判断光电材料的重要参数. 研究通过合成两种不同缺陷态浓度的CH₃NH₃PbI₃晶体，测量这两种晶体在0.019∽4.268 μJ/cm²的激光激发下的时间分辨荧光光谱，利用动力学模型对光谱进行拟合，可以获得每个晶体的掺杂浓度，空穴浓度以及电荷复合参数. 将这些参数结合已有公式，最终可获得每个晶体的电荷载体的扩散长度.     

FePc与TiO2(110)及C60界面电子结构研究

基于C₆₀受体和有机分子给体的太阳能电池是目前非常重要的一个研究热点, 利用同步辐射真空紫外光电子能谱(SRUPS) 技术研究了酞菁铁(FePc)与TiO₂(110)及C₆₀的界面电子结构, 以及FePc与C₆₀分子混合薄膜的电子结构. SRUPS价带谱显示, FePc沉积在化学计量比与还原态两种不同的TiO₂(110)表面时, FePc分子的HOMO能级均随FePc厚度的变化发生了移动, 而在化学计量比的TiO₂(110)表面位移较大, 同时发生界面能带弯曲, 说明存在从有机层向衬底的电子转移. 在FePc/C₆₀和C₆₀/FePc界面形成过程中, FePc与C₆₀分子的最高占据分子轨道(HOMO)位移大小基本相同. 由界面能级排列发现, 在FePc与C₆₀的混合薄膜中, FePc分子的HOMO与C₆₀分子的最高占据分子轨道能级差较大, 这有利于提高器件开路电压, 改善器件性能.     

二价金属元素掺杂对LiCoO2体系电子输运性质的影响

为了解释Ca掺杂与Mg掺杂在影响锂离子二次电池正极材料LiCoO₂体系电子输运性质方面的不同效应，采用基于密度泛函理论的第一性原理方法研究了该体系的电子结构.计算结果表明，虽然在LiCoO₂体系中用Ca或Mg替代Co都会在费米能级附近产生部分占据的受主带，但两者对应的电子态都具有明显的局域化特征；此外，与Mg掺杂体系明显不同的是，Ca掺杂体系的受主带与价带之间存在清晰的带隙.这一带隙的存在正是Ca掺杂不能明显提高LiCoO₂体系电导率的主要原因.此外，Ca²⁺与Mg²⁺离子半径的较大差别也是造成这两个掺杂体系的电导率存在明显差异的一个重要因素.     

二维GaTe/Bi2Se3异质结：一类有潜力的Z型光解水催化剂

本文基于第一性原理方法，计算了二维GaTe/Bi₂Se₃异质结的电子结构、界面电荷转移、静电势分布、吸收光谱及光催化性质. 计算结果表明异质结是一个小能隙的准直接半导体，能有效捕获太阳光. 由于相对较强的界面內建极化电场和带边轻微弯曲，导致异质结中的光生电子和空穴分别有效分离在GaTe单层和Bi₂Se₃薄片上，可用于析氢和产氧. 这些理论计算结果意味着二维GaTe/Bi₂Se₃异质结是一类有潜力的Z型太阳能全解水催化剂.     

窄谱带绿色有机电致发光器件

以Tb³⁺:水杨酸(Tb³⁺:(SA)₃)为空穴传输层兼发光层、高荧光材料Alq₃为电子传输层,得到了窄谱带的绿色有机薄膜电致发光双层结构器件.实验证实,双层器件的电致发光是电荷载流子隧穿内界面(Tb³⁺:(SA)₃/Alq₃)之后分别在两有机层内的复合发光,是两有机层本征发光的叠加.其光谱随着电子传输层厚度而改变,因而减少电子传输层厚度能得到亮度高、稳     

Bifunctional photocatalysis of TiO2/Cu2O composite under visible light: Ti in organic pollutant degradation and water splitting

Photocatalytic experiment results under visible light demonstrate that both TiO₂ and Cu₂O have low activity for brilliant red X-3B degradation and neither can produce H₂ from water splitting. In comparison, TiO₂/Cu₂O composite can do the both efficiently. Further investigation shows that the formation of Ti³⁺ under visible light has great contribution. The mechanism of photocatalytic reaction is proposed based on energy band theory and experimental results. The photogenerated electrons from Cu₂O were captured by Ti⁴⁺ ions in TiO₂ and Ti⁴⁺ ions were further reduced to Ti³⁺ ions. Thus, the photogenerated electrons were stored in Ti³⁺ ions as the form of energy. These electrons trapped in Ti³⁺ can be released if a suitable electron acceptor is present. So, the electrons can be transferred to the interface between the composite and solution to participate in photocatalytic reaction. XPS spectra of TiO₂/Cu₂O composite before and after visible light irradiation were carried out and provided evidence for the presence of Ti³⁺. The image of high-resolution transmission electron microscopy demonstrates that TiO₂ combines with Cu₂O tightly. So, the photogenerated electrons can be transferred from Cu₂O to TiO₂.     

Epitaxial growth defects and interfacial structures of Cu deposited on TiO2

Epitaxial growth defects and the interfacial structure between vapor deposited Cu and TiO₂(110) have been studied by combined high-resolution electron microscopy (HREM) and image simulations. The Cu film was found to grow epitaxially with an orientation given by Cu(111)//TiO₂(110) and Cu110//TiO₂ [001]. With this relationship, there exist two equivalent domain orientations which are rotated with respect to each other by 180°. Localized misfit dislocations have not been detected, but {111} stacking faults and microtwins were observed which may occur as a result of 3-D island coalescence. HREM observations and image simulations have been used to study the interface atomic structure. The dominant interfacial structure has a stoichiometric (110) TiO₂ surface with bridging rows of O atoms and occasionally, an interfacial structure having a reduced (110) TiO₂ surface terminated by both Ti and O atoms has been observed locally.     

Dense coating of surface mounted CuBTC Metal-Organic Framework nanostructures on silk fibers, prepared by layer-by-layer method under ultrasound irradiation with antibacterial activity

The growth of Cu₃(BTC)₂ (BTC = 1,3,5-benzenetricarboxylate), also known as CuBTC and HKUST-1, Metal-Organic Framework (MOF) nanostructures on silk fibers were achieved by layer-by-layer technique in alternating bath of Cu(OAc)₂·2H₂O and H₃BTC solutions under ultrasound irradiation. The effect of pH, reaction time, ultrasound irradiation and sequential dipping steps in growth of the CuBTC Metal-Organic Framework nanostructures has been studied. These systems depicted a decrease in the size accompanying a decrease in the sequential dipping steps. In addition, dense coating of silk fibers with CuBTC MOF results in decrease the emission intensity of silk fibers. The silk fibers containing CuBTC Metal-Organic Framework exhibited high antibacterial activity against Escherichia coli and Staphylococcus aureus. The samples were characterized with powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) spectra and scanning electron microscopy (SEM). XRD analyses indicated that the prepared CuBTC MOF nanostructures on silk fibers were crystalline.     

乙醇在TiO2(110)表面光催化解离的动力学和超快电子动态学 (cited: 2)

采用实时双光子光电子能谱和时间分辨双光子光电子能谱技术分别研究了乙醇在该表面光催化解离的动力学和超快电子动态学过程. 通过测量与乙醇光催化解离相关的电子激发态随时间的演化,发现这个反应满足分型动力学. 乙醇在还原性TiO₂(110)上的光催化解离比在氧化性表面快,这归结于缺陷的存在降低了反应能垒. 这样一个反应的加速过程很可能是与缺陷电子相关的. 通过干涉双脉冲相关的测量,得到了乙醇-TiO₂界面电子激发态的超快动态学. 与甲醇的情况类似,这个电子激发态的寿命为24 fs. 激发态的出现为TiO₂和它周围环境的电子转移提供了一个通道.     

Investigation of polymer/inorganic hybrid photovoltaic device using quantum dots as the interface modifier

CdS quantum dots (QDs) were introduced as an interface modifier in the poly(3-hexylthiophene) (P3HT)/TiO₂ nanorod arrays hybrid photovoltaic device. The presence of CdS QDs interlayer was found to provide enhanced light absorption, increased interfacial recombination resistance at the P3HT/TiO₂ interfaces, thus leading to a lower recombination rate of the electrons due to the stepwise structure of band edge in P3HT/CdS/TiO₂, which accounts for the observed enhanced photocurrent and photovoltage of the hybrid solar cells. The optimized performance was achieved in P3HT/CdS/TiO₂ hybrid solar cells after deposition of CdS QDs for 10 cycles, with a power conversion efficiency of 0.57 %, which is nearly ten times higher than that of P3HT/TiO₂. The findings indicate that inorganic semiconductor quantum dots provide effective means to improve the performance of polymer/TiO₂ hybrid solar cells.     

“In situ” XPS study of band structures at Cu2O/TiO2 heterojunctions interface

In an attempt to investigate influence of the defects on electronic structure of Cu₂O/TiO₂ heterojunctions, thin Cu₂O layers were successively deposited on TiO₂ that has different levels of defect concentrations, and the resultant band bending and offset characteristics were studied by in situ X-ray photoelectron spectroscopy (XPS). The TiO₂ substrates with defects were prepared by Ar⁺ sputtering, followed by annealing at different temperatures in oxygen atmosphere. Presence of the defects in TiO₂ surface dramatically influences on the band bending and band offset at the interface: more defects are on TiO₂ surface, less band bending are at the interface, inducing smaller conduction band offsets. On the reduced TiO₂ surface, Cu₂O was disproportionately decomposed to form CuO and Cu.     

甲醇在二氧化钛上的光化学性质与表面结构的相关性

通过双光子光电子的方法探测了TiO₂(011)-(2×1) 和TiO₂(110)-(1×1)表面的光催化氧化甲醇的性质. 在吸附了甲醇的二氧化钛(011)和(110)界面处探测到了一个费米能级以上2.5 eV的电子激发态,该电子激发态可作为测试二氧化钛界面还原性的探针使用. 利用此探针在甲醇/TiO₂(011)-(2×1)和甲醇/TiO₂(110)-(1×1)界面探测到了一个随光照时间的电子激发态信号变化,这一变化可以归于光催化生成的表面羟基对界面还原性的影响. 由此得出的光催化氧化甲醇的速率TiO₂(110)-(1×1)比TiO₂(011)-(2×1)快了大约11.4倍. 这可能由于表面原子结构排布的原因不同. 本工作不仅介绍了一个利用双光子光电子能谱探测到的甲醇/TiO₂界面电子结构的细节特征,还揭示了表面结构对二氧化钛光反应性质的重要影响.     

Reaction of SO2 with Cu/TiO2(1 1 0): Effects of size and metal-oxide interactions in the chemical activation of Cu nanoparticles

The reaction of SO₂ with stoichiometric TiO₂(1 1 0), partially reduced TiO_2 − x(1 1 0) and Cu/TiO₂(1 1 0) was investigated using synchrotron based X-ray photoemission spectroscopy. SO₂ adsorbs on perfect TiO₂(1 1 0) forming SO₄ species at room temperature, while SO₂ dissociatively adsorbs on partially reduced TiO_2 − x(1 1 0) forming SO₄, SO₃ as well as two sulfide species. SO₂ exposure to Cu particles supported on perfect TiO₂(1 1 0) can lead to the formation of SO₄, SO₃ and sulfide species. When depositing Cu on SO₄/TiO₂(1 1 0) at room temperature, the dissociation efficiency of Cu atoms is much higher than that of Cu deposited on TiO₂(1 1 0) prior to SO₂ dosing. The post-deposited Cu atoms can efficiently contact and react with SO₄ species before they form Cu-Cu bonds and big clusters. Small Cu nanoparticles supported on TiO₂(1 1 0) are more reactive towards SO₂ than surfaces of bulk copper. The chemical reactivity of the Cu/TiO₂(1 1 0) system increases with Cu coverage until reaching a maximum at θ_Cu = 0.5-0.8 ML. After this point, an increase in Cu coverage leads to the formation of big Cu particles and the reactivity of the system decrease to that typical of bulk Cu. A comparison with results for SO₂/Cu/MgO(0 0 1) indicates that the effects of size and metal ↔ oxide interactions are important for the chemical activation of Cu nanoparticles on titania.     

Synthesis of compositionally controllable Cu<Subscript>2</Subscript>(Sn<Subscript>1−x</Subscript>Ge<Subscript>x</Subscript>)S<Subscript>3</Subscript> nanocrystals with tunable band gaps

In this work, we show that compositionally controlled Cu₂(Sn_1–xGe_x)S₃ nanocrystals can be successfully synthesized by the hot-injection method through careful tuning the Ge/(Sn+Ge) precursor ratio. The band gaps of the resultant nanocrystals are demonstrated to be linearly tuned from 1.45 to 2.33 eV by adjusting the composition parameter x of the Ge/(Sn+Ge) ratio from 0.0 to 1.0. The crystalline structures of the resultant NCs have been studied by the X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), select area electron diffraction (SAED), and Raman spectroscopy. A ligand exchange procedure is further performed to replace the native ligands on the surface of the NCs with sulfur ions. The photoresponsive behavior indicates the potential use of as-prepared Cu₂(Sn_1–xGe_x)S₃ nanocrystals in solar energy conversion systems. The synthesis of compositionally controlled Cu₂(Sn_1–xGe_x)S₃ nanocrystals reported herein provides a way for probing the effect of Ge inclusion in the Cu-Sn-S system thin films.     

Evaluation of exchange interaction in binuclear copper(II) chelates of amide-based cyclophanes

Temperature dependence of the electron paramagnetic resonance (EPR) spectra of binuclear Cu(II) complexes with amide-based cyclophanes, Cu₂(bis-EDTAPDN), Cu₂(bis-EDTANAP) and Cu₂(bis-EDTABPE), in 60% methanol (pH ca. 10) has been studied at a frequency of 9.43 GHz in the temperature range of 77–4.2 K; the cyclophanes are macrocyclic compounds in which four amide bonds link two ethylenediaminetetraacetate (EDTA) units and two units of the aromatic diamine 1,4-phenylenediamine (DPN), 1,5-diaminonaphthalene (NAP) or bis(4-aminophenyl) ether (BPE). Exchange integrals found from the EPR measurements are ca. 70–105 cm^?1, 22 cm^?1 andJ ≤ 0, for Cu₂(bis-EDTAPDN), Cu₂(bis-EDTANAP) and Cu₂(bis-EDTABPE), respectively; the sign ofJ is defined to be positive for antiferromagnetic interaction. The variation of exchange interactions in these compounds is related to the nature of the bridging organic groups.