三维网状Dy3+:YVO4/TiO2复合纤维的制备及光催化产氢性能

以电纺TiO₂纳米纤维为基质, 柠檬酸为软模板, 采用一步水热法制备了具有三维立体网状结构的稀土Dy ³⁺掺杂YVO₄/TiO₂复合纤维. 通过X射线衍射、 扫描电子显微镜、 X射线光电子能谱、 N₂吸附-脱附、 紫外-可见漫反射光谱及荧光光谱等手段对材料的组成、 表面形貌和性能进行表征, 以光分解水产氢实验考察其光催化活性. 结果表明, Dy ³⁺∶YVO₄纳米枝与TiO₂纳米纤维相互交联构筑的纳米纤维网具有大比表面积, 可提供更多活性位点, 改善了多相光催化反应的传递过程; 稀土Dy ³⁺掺杂的YVO₄与TiO₂复合形成异质结相互促进, 在拓宽光谱响应范围、 提高太阳光利用率的同时使光生电子-空穴对得到较好分离, 从而提高了样品的光催化活性. 模拟太阳光照射下, Dy ³⁺∶YVO₄/TiO₂复合纤维光催化产氢速率达到8.63 mmol· h ^-1·g ^-1, 是纯TiO₂纳米纤维的10倍.     

Ru(bpy)2(NCS)2染料敏化CdS/Zn2+TiO2复合半导体纳米多孔膜的光电化学

采用水热法合成了Zn²⁺离子掺杂的TiO₂纳米粒子[Zn²⁺掺杂量0.5%(物质的量的比)],并用光电化学方法研究了经Ru(bpy)₂(NCS)₂(bpy=2,2′bipyridine₄,4′dicarboxylicacid)分别敏化的掺杂Zn²⁺的TiO₂电极(简写为Zn²⁺-TiO₂)和CdS/Zn²⁺-TiO₂复合半导体纳米多孔膜电极的光电化学行为.实验证明Ru(bpy)₂(NCS)₂敏化CdS/Zn²⁺-TiO₂复合半导体纳米多孔膜电极比单独敏化Zn²⁺-TiO₂电极的光电转换效率高,且敏化Zn²⁺TiO₂电极和敏化CdS/Zn²⁺TiO₂复合半导体纳米多孔膜电极比Zn²⁺-TiO₂电极的光电流产生的起始波长都向长波方向移动.在360600nm范围内,Ru(bpy)₂(NCS)₂敏化CdS/Zn²⁺-TiO₂复合半导体纳米多孔膜电极光电转换效率最好.     

硫化镉晶体结构形态对乙醇光催化脱氢活性的影响

有关醇类水溶液光催化贮能脱氢反应研究大多集中在提高半导体TiO₂和CdS表面修饰组分的光催化活性^[1～3]及考察TiO₂半导体晶体结构与光催化性能的关系上^[4,5],CdS半导体晶体结构形态对光催化性能的影响尚未见报道.本文在这方面进行了一些有益的研究.     

锚定在中空碳纳米笼上的Fe掺杂Co3O4用于高效电催化析氧(英文)

本研究采用[Fe(CN)₆]^3-阴离子交换2-甲基咪唑再于空气气氛下退火衍生的策略,制备了一种负载在氮掺杂中空纳米笼碳骨架上的Fe掺杂Co₃O₄电催化剂(Fe-Co₃O₄/NC),用于电催化OER。XRD和HRTEM表征证实了Fe掺人Co₃O₄的晶格中。XPS表征明确了Fe引入后Co价态升高,这是基于Co²⁺/Co³⁺和Fe³⁺的价电子构型诱导的电子由Co²⁺/Co³⁺向Fe³⁺的转移,这会促使Co位点在OER过程中衍生为CoOOH活性物种,作为真正的电催化活性中心,这也被OER稳定性测试后的HRTEM和XPS表征所证实。电化学性能测试显示,该电催化剂的OER过电位仅有275 mV且能够在100 mA/cm²的电流密度下稳定维持20 h,兼具优异的电催化活性和稳...     

Lu(La)2O3微米晶中提高Bi3+离子下转换蓝光发光性能的研究

采用尿素沉淀法制备一系列Bi³⁺/La³⁺共掺Lu₂O₃和Bi³⁺/Lu³⁺共掺La₂O₃微米晶。在掺杂Bi³⁺离子的Lu₂O₃微米晶中,C₂位点的Bi³⁺离子可以将吸收的能量转移给S₆位点的Bi³⁺离子。同时,在Lu₂O₃:1%Bi³⁺,0～5%(摩尔分数,下同)La³⁺微米晶中,372和337 nm(C₂和S₆位点的Bi³⁺离子)紫外光的激发下,Bi³⁺离子的发射峰强度随着La³⁺离子掺杂浓度的增加而增加,掺杂5%La³⁺时与不掺杂La     

亚晶格能量团簇构建及晶场调控对四方LiYF4:RE上转换发光机制的影响研究

四方LiYF₄是一种与六方NaYF₄相当的稀土上转换发光基质材料,由于相对优异的短波上转换发光特性,近年受到业界的相当关注,但对产生这一优异特性的原因还未见报道.经研究发现,四方LiYF₄具有六边环状亚晶格结构,每5个间距小于0.4 nm的近邻三价阳离子形成一个团簇,稀土离子间的能量传递容易在团簇内或六边形环内环绕传递.基于它的这一亚晶格结构特征,本工作通过引入不同量敏化剂Yb³⁺和掺杂离子Sc³⁺和Hf⁴⁺,考察不同激活离子Er³⁺、Ho³⁺和Tm³⁺与敏化离子Yb³⁺构建亚晶格能量团簇以及异质离子Sc³⁺和Hf⁴⁺掺杂晶场调控对稀土离子上转换发光性能的影响机制.发现不同稀土离子与Yb³⁺存在不同的能级匹配,导致不同概率的无辐射交叉弛豫行为,当引入适量的Yb³⁺时,可分别构建1Er-2Yb、1Ho-2Yb和1Tm-4Yb亚晶格能量团簇,实现最佳的上转换发光性能;当6 mol% Sc³⁺和4 mol% Hf⁴⁺引入时,可有效调控晶场的不对称性;掺杂后,5个近邻三价离子的团簇结构中,只有3个近邻Yb³⁺离子,无法同时实现Er³⁺离子的⁴F_5/2和Sc³⁺的²G_7/2或Hf⁴⁺的⁴F_5/2^o激发态的双光子合作上转换电子布居,导致Sc³⁺或Hf⁴⁺成为荧光猝灭中心,Sc³⁺掺杂晶场调控最大仅提升50%的荧光强度,Hf⁴⁺掺杂没有提升反而降低Er³⁺离子的上转换发光强度,不同于它们掺杂六方NaYF₄：Er/Yb那样扮演储能离子角色,显著提升Er³⁺离子的短波上转换发光强度.本研究揭示了在六边环状亚晶格基质结构中不同稀土离子与敏化剂Yb³⁺的敏化上转换发光机制,以及基质结构特征对掺杂晶场调控行为的影响机制,可为设计和制备高性能上转换发光材料提供借鉴.     

水杨酸盐敏化BaF2∶Tb3+纳米粒子中的Tb3+离子发光

采用水热法制备了均匀、单分散的BaF₂∶Tb³⁺纳米粒子,并采用离子交换法制备了水杨酸钠敏化的BaF₂∶Tb³⁺纳米粒子(SS-BaF₂∶Tb³⁺)。 系统地研究了样品的结构、形貌和光致发光性质。 结果表明,监测Tb³⁺离子在547 nm的⁵D₄→⁷F₅跃迁,SS-BaF₂∶Tb³⁺纳米粒子获得了从200 nm到385 nm波长范围宽的激发带;激发SS的π-π^*电子跃迁吸收,由于SS到Tb³⁺的能量传递(“天线效应”),SS-BaF₂∶Tb³⁺纳米粒子产生了增强的Tb³⁺离子绿光发射;敏化纳米粒子中Tb³⁺离子光致发光寿命比未敏化纳米粒子中Tb³⁺离子寿命长。     

离子掺杂改性纳米TiO_2光催化剂的研究进展

以纳米TiO2为代表的纳米半导体光催化材料是目前研究的热点。纳米TiO2为宽禁带半导体,需紫外光激发;而且,产生的光生电子-空穴对极易复合,限制了其实际应用。将纳米TiO2进行离子掺杂改性是解决上述问题的有效途径。目前离子掺杂改性纳米TiO2光催化剂的研究进展表明,采用两种离子共掺杂改性纳米TiO2时,离子之间会产生协...     

低量La3+掺杂S-TiO2光催化剂的制备、表征及其光催化活性

采用溶胶-凝胶-浸渍法制备了La³⁺/S-TiO₂纳米光催化剂,通过XRD、BET、XPS、UV-Vis等手段进行了表征.以甲基橙溶液为光催化降解反应的模型化合物,考察了光催化剂的活性,探讨了低量La³⁺掺杂对TiO₂纳米粒子光催化活性的影响机制.实验结果表明:S改性TiO₂后明显提高了TiO₂纳米粒子的光催化活性,而La³⁺掺杂S-TiO₂后,进一步提高了TiO₂纳米粒子的光催化活性,La³⁺的最佳掺杂量(相对于TiO₂的质量分数)为0.369%;La³⁺/S-TiO₂(ω(La³⁺)=0.369%)为纳米光催化剂时,甲基橙的脱色率达到92.4%(光照120min);XRD和BET分析表明,低量La³⁺掺杂抑制了TiO₂由锐钛矿向金红石的转变,阻碍了TiO₂晶粒的生长,提高了TiO₂的比表面积;XPS分析表明,S、La³⁺掺杂可以导致粉体的表面羟基含量增加,掺杂S以S⁶⁺形式置换TiO₂晶格中的Ti⁴⁺;UV-Vis分析表明,光催化剂La³⁺/S-TiO₂比纯TiO₂具有较强的紫外光吸收性能.与纯TiO₂相比,La³⁺掺杂TiO₂纳米粒子光催化氧化活性的提高应归因于La³⁺掺杂增加了表面羟基含量,增大了比表面积,增强了样品表面的紫外光吸收能力.     

Cs2ZnCl4∶Ce3+,Mn2+的合成及其多模发光性能

近年来,低维无铅金属卤化物由于其独特的光学性质、低毒性和优异的环境稳定性等优点受到了广泛关注。采用水热法成功制备Cs₂ZnCl₄∶Ce³⁺、Cs₂ZnCl₄∶Mn²⁺以及Cs₂ZnCl₄∶Ce³⁺,Mn²⁺等微米晶,并利用X射线衍射仪、荧光光谱仪等表征手段对其物相和发光特性进行了系统性研究。研究结果表明,Cs₂ZnCl₄微米晶为正交相零维结构,其发射光谱依赖于掺杂离子的激发波长,例如,Ce³⁺离子掺杂的Cs₂ZnCl₄微米晶在254nm的激发条件下,其发射光谱峰位位于350nm,对应于Ce³⁺离子4f-5d的跃迁;Mn²⁺离子掺杂的Cs₂ZnCl₄微米晶在361nm的激发条件...     

Electrospinning Synthesis and Photoluminescence Properties of SnO2：xEu3＋ Nanofibers

NnO2：xEu3＋（x=O, 1%, 3%, 5%, molar fraction） fibers were synthesized by electrospinning technology. The size of the as-prepared fibers is relatively uniform and the average diameter is about 200 nm with a large draw ratio. The as-prepared Eu3＋ doped SnO2 nanofibers have a rutile structure and consist of crystallitc grains with an average size of about 10 nm. A slight red shift of the A1gand Bag vibration modes and an additional peak at 288 nm were observed in the Raman spectra of the nanofibers. The energies of bandgaps of the SnO2 nanofiber with Eu doping of 1% and 3% are 2.64 eV, and the energy of bandgap is 2.94 eV with Eu doping of 5%（molar fraction）. There is only orange emission（5D0→7F1 magnetic dipole transition） for Eu doped SnO2 nanofibers, and no red emission could be observed. The orange emission upon indirect excitation splits into three peaks and the peak intensity at the excitation wavelength of 275 nm is higher than that at the excitation wavelength of 488 nm.     

六核簇离子Te64+和P64-的电子结构与化学键

本文用EHMO法计算六核簇离子Te₆⁴⁺和P₆^4-的电子结构。分析与它们相同构型的棱柱烷C₆H₆和苯在成键性质上的差异。结果表明,这两簇离子的多余价电子填充到能级略高于自由原子p轨道的弱反键分子轨道。     

Effect of Zn2+ Ions on Upconversion Emission of Er3+ in Zn/Er:LiNbO3 Crystal

The effect of Zn2+ ions codoped on the upconversion emission of Er3+ ions in Er:LiNbO3 crystal under different excitation wavelength was reported.The upconversion emission spectra of Zn/Er:LiNbO3 follo...     

CuInS_2/ZnS量子点的微波水热合成与表征——推荐一个研究型综合实验

介绍一个研究型综合实验——简易微波水热合成CuInS_2/ZnS复合量子点及其表征。实验通过Cu~(2+)、In~(3+)、Zn~(2+)和S~(2-)离子为原料,以谷胱甘肽作为稳定剂,两步微波水热合成水溶性的CuInS_2/ZnS复合量子点。用X射线衍射法和透射电镜表征它的结构和形貌,用紫外-可见光吸收、荧光光谱、荧光寿命和荧光照片等表征光学性质,并探究温度、时间、成份对荧光性质的影响。通过该实验的设计与实施培养学生科学研究的方法和思维能力。     

Influence of the size of doping ion on phase stability and oxygen permeability of SrCo0.8Fe0.2O3−δ oxide

The compounds of SrCo_0.8Fe_0.2O_3−δ (SCF) doped with Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺, Ti⁴⁺ and Zr⁴⁺ are synthesized by conventional solid-state reaction. The phase stabilities and oxygen permeabilites of these synthesized oxides are investigated. It is found that the doping Mg²⁺, Ca²⁺, Sr²⁺ and Ba²⁺ totally dissolve into the SCF unit cell, while SrTiO₃ and SrZrO₃ phases form when SCF is doped with Ti⁴⁺ and Zr⁴⁺, respectively. A possible mechanism of the doping behavior is proposed to interpret the structure transformation of the SCF unit cell. Phase stability increases directly with the size of the doping ion when SCF is doped with the ions in the same group. However, the influence of the size of the doping ion on the oxygen permeation behavior is negligible for the membranes doped with the ions in the same group.     

铁氰根桥联的一维链状大环配位聚合物的合成及结构

配位聚合物的合成、结构和性质研究近年来引起了人们极大的兴趣 ,已成为配位化学最活跃的研究领域之一 .由于 [Fe( CN) 6 ]3- 和 [Fe( CN) 6 ]4- 离子本身具有丰富的配位特性 ,可与金属离子及其配合物形成一维链状、二维网状和三维立体结构的配位聚合物 [1～ 5] ,铁氰根和亚铁氰根桥联的配位聚合物的研究成为其中的研究热点之一 .此外 ,铁氰根和亚铁氰根桥联的配位聚合物具有较高的铁磁相变温度[6～ 8] ,是一类具有较好应用前景的分子磁体 .但是 ,以金属大环配合物作为结构单元与 [Fe( CN) 6 ]3-和 [Fe( CN) 6 ]4-离子形成的配位聚合物…     

Inorganic cluster syntheses of TM2+-doped quantum dots (CdSe, CdS, CdSe/CdS): physical property dependence on dopant locale

A series of colloidal transition-metal-doped chalcogenide semiconductor nanocrystals (TM2+:CdSe, TM2+:CdS, etc.) has been prepared by thermal decomposition of inorganic cluster precursors. It is shown through extensive spectroscopic and structural characterization that the nanocrystals prepared following literature procedures for synthesis of TM2+:CdSe nanocrystals actually possess an unintended CdSe/TM2+:CdS core/shell morphology. The conditions required for successful formation of TM2+:CdSe and TM2+:CdS by cluster decomposition have been determined. Magneto-optical and photoluminescence spectroscopic results for this series of doped nanocrystals reveal major physical consequences of dopant localization within the shell and demonstrate the capacity to engineer dopant-carrier exchange interactions via core/shell doping strategies. The results presented here illustrate some of the remarkable and unexpected complexities that can arise in nanocrystal doping chemistries and emphasize the need for meticulous characterization to avoid false positives.     

A Gaussian-2 ab initio study of [C2H5S] ions: III. H2 and CH4 eliminations from CH3CHSH and CH3SCH2

Gaussian-2 ab initio calculations were performed to examine the six modes of unimolecular dissociation of cis-CH₃CHSH⁺ (1⁺), trans-CH₃CHSH⁺ (2⁺), and CH₃SCH₂⁺ (3⁺): 1⁺→CH₃⁺+trans-HCSH (1); 1⁺→CH₃+trans-HCSH⁺ (2); 1⁺→CH₄+HCS⁺ (3); 1⁺→H₂+c-CH₂CHS⁺ (4); 2⁺→H₂+CH₃CS⁺ (5); and 3⁺→H₂+c-CH₂CHS⁺ (6). Reactions (1) and (2) have endothermicities of 584 and 496 kJ mol⁻¹, respectively. Loss of CH₄ from 1⁺ (reaction (3)) proceeds through proton transfer from the S atom to the methyl group, followed by cleavage of the C–C bond. The reaction pathway has an energy barrier of 292 kJ mol⁻¹ and a transition state with a wide spectrum of nonclassical structures. Reaction (4) has a critical energy of 296 kJ mol⁻¹ and it also proceeds through the same proton transfer step as reaction (3), followed by elimination of H_2. Formation of CH₃CS⁺ from 2⁺ (reaction (5)) by loss of H₂ proceeds through protonation of the methine (CH) group, followed by dissociation of the H₂ moiety. Its energy barrier is 276 kJ mol⁻¹. On both the MP2/6-31G* and QCISD/6-31G* potential-energy surfaces, the H₂ 1,1-elimination from 3⁺ (reaction (6)) proceeds via a nonclassical intermediate resembling c-CH₃SCH₂⁺ and has a critical energy of 269 kJ mol⁻¹.     

铕(Ⅲ)激活的磷酸镧发光性质研究

LaPO₄:Eu³⁺的发射光谱包含较强的Eu³⁺⁵D_o→⁷F₁跃迁发射和较弱的⁶D₁→⁷F₁跃迁发射。主发射峰583nm,对应于Eu³⁺5D_o→⁷F₁跃迁.通过对Eu³⁺的两种跃迁发射强度及荧光寿命和Eu³⁺浓度关系的测定和理论分析,探讨了发光中心Eu³⁺离子同的交叉弛豫和能量迁移机理。     

Preparation of Novel Ultrathin Co doped MoS2 Nanosheets Piezocatalyst for Fast Simultaneous Decomposition of Cr(Ⅵ) and MB in Dark

Ultrathin Co doped MoS2 nanosheets(NSs) with thickness of 3.2 nm was used to simultaneously decompose Cr(Ⅵ) and MB in dark through ultrasonic vibration-assisted piezocatalytic effect. The significantly enhanced piezocatalytic performance of Co doped MoS2 NSs was found in comparison to the pristine MoS2 NSs. The high piezocatalytic activity of Co doped MoS2 NSs may originate from the large amount of charge carriers due to Co doping. The efficient separation of electron-hole pairs under spontaneous polarization were also investigated ill detail, which is responsible for reduction of Cr(Ⅵ) and oxidation of methylene blue(MB). The active species trapping experiments demonstrate that e and ·O2^- are main active substances for Cr(Ⅵ) reduction, while h+,·OH, and ·O2^- participate in MB degradation.