三元荆棘状Zn1-xCdxO纳米结构及其光致发光特性

以锌粉(zn)、镉粉(cd)为源材料,金(Au)做催化剂,采用热蒸发法,在硅(si)衬底上制备出掺Cd摩尔分数为6.7%的三元荆棘状Zn1-xCdxO单晶纳米结构.荆棘状纳米结构样品的主干直径均一,约为100 nm.主干两侧刺的直径和长度分别约为10和100 nm.由于Cd替位原子对ZnO带隙的调节作用,样品的近带边(NBE)紫外(UV)发射从3.37 ev红移到3.13 eV.结果表明,氧气(O2)分压是形成荆棘状Zn1-xCdxO纳米结构的重要条件.     

配位-均匀沉淀法合成Cd(OH)2和CdO纳米带

以硝酸镉为前驱物、氨水(25-28 wt%)为沉淀剂,在无模板的条件下,采用配位-均匀沉淀法成功地合成了Cd(OH)2纳米带。将Cd(OH)2纳米带在350℃下煅烧4 h得到形貌相似的CdO半导体纳米材料。X-射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)、电子衍射(SAED)等测试结果表明,所制备的Cd(OH)2纳米带是由尺寸约25 nm的Cd(OH)2纳米粒子组成,其宽度为100-200 nm、长度达1.5 um、厚度约为30 nm;Cd(OH)2为六方晶系结构;CdO纳米带由更小的CdO纳米粒子组成,CdO为面心立方晶型。本文还初步探讨了Cd(OH)2纳米带的形成过程。     

新型半导体可见光催化剂纳米锰酸钇

采用聚丙烯酰胺凝胶法制备了锰酸钇(YMnO3)纳米颗粒,并运用X射线衍射、扫描电镜和紫外可见漫反射光谱对样品进行了表征.结果表明,制得的YMnO3纳米晶主要为六方钙钛矿结构,兼有少许的正交钙钛矿结构,且颗粒粒度均匀、形貌规整、呈类球形,平均颗粒尺寸约为45 nm.另外,测得YMnO3纳米颗粒的光学带隙值为1.31 eV...     

Co掺杂ZnO纳米棒的水热法制备及其光致发光性能

以Zn(NO3)2·6H2O 和Co(NO3)2·6H2O为原料, 通过水热法在较低温度下制备了纯ZnO和Co掺杂的ZnO(ZnO:Co)纳米棒. 利用XRD、EDS、TEM和HRTEM对样品进行了表征, 结合光致发光(PL)谱研究了样品的PL性能. 结果表明, 水热法制备纯ZnO和ZnO:Co纳米棒均具有较好的结晶度. Co2+是以替代的形式进入ZnO晶格, 掺入量为2%(原子分数)左右. 纯的ZnO纳米棒平均直径约为20 nm, 平均长度约为180 nm; 掺杂样品的平均直径值约为15 nm, 平均长度约为200 nm左右; Co掺杂轻微地影响ZnO纳米棒的生长. 另外, Co掺杂能够调整ZnO纳米棒的能带结构、提高表面态含量, 进而使得ZnO:Co纳米棒的紫外发光峰位红移, 可见光发光能力增强.     

荆棘状羟基磷灰石棒的电化学法制备及性能表征

先后在低浓度和高浓度的钙、磷电解液中,采用两步电化学沉积法在纯钛金属表面制备了荆棘状羟基磷灰石棒(THA)。微观结构分析表明,THA的主干是由HA单晶构成,直径为100~200 nm,叉刺为HA多晶结构,直径为10~50 nm,它们在钛金属表面构成了具有两重微纳形貌的多孔涂层。溶解性实验与接触角测试结果表明,与单纯的HA棒涂层相比,这种THA涂层具有较高的钙离子释放速度和优异的表面润湿性。     

梯型多孔g-C3N4/Zn0.2Cd0.8S-DETA复合材料的合成及其高效稳定光催化产氢性能（英文）

近年来,化石燃料燃烧导致的环境污染问题和能源危机越来越严重.在众多解决方案中,光催化产氢由于其可持续性以及无污染等特点而受到广泛关注.然而,由于许多半导体光催化剂性能不理想,光催化水分解研究进程缓慢.本研究采用水热法成功制备了梯型Pg-C3N4/Zn0.2Cd0.8S-DETA复合材料用于光催化产氢.DETA(二亚乙基三胺)作为一种有机分子插入在Zn0.2Cd0.8S的层中构成有机-无机杂化材料.采用X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线光电子能谱(XPS)、紫外-可见光漫反射光谱(UV-vis)以及光电流研究了所制备样品的结构、形貌、元素组成以及光电特征,并提出了可能的光催化机制.XRD和XPS结果表明Pg-C3N4和Zn0.2Cd0.8S-DETA复合在一起而不是机械混合.通过TEM可以看出Pg-C3N4是一种带有很多孔洞的纳米片,而Zn0.2Cd0.8S-DETA类似于纳米花瓣,在Pg-C3N4/Zn0.2Cd0.8S-DETA复合材料中Pg-C3N4表面充满了Zn0.2Cd0.8S-DETA纳米花瓣.经过元素分析得知所合成的复合材料没有杂质元素.UV-vis表明Pg-C3N4和Zn0.2Cd0.8S-DETA具有良好的吸收带边以及带隙,分别为2.83 eV和2.48 eV.光电流和PL显示15%Pg-C3N4/Zn0.2Cd0.8S-DETA具有很高的载流子分离及传输效率.光催化性能测试显示15%Pg-C3N4/Zn0.2Cd0.8S-DETA具有很好的产氢活性,为6.69 mmol g^-1 h^-1,分别是Pg-C3N4和Zn0.2Cd0.8S-DETA的16.73和1.44倍.在经过七次循环实验后15%Pg-C3N4/Zn0.2Cd0.8S-DETA仍保持很优异的活性,说明它具有很好的稳定性.通过高分辨XPS中各元素结合能的变化可以看出构成异质结之后电子的流向,从而看出光催化可能的机制为梯形.光照射之后,Pg-C3N4和Zn0.2Cd0.8S-DETA中产生电子-空穴对,电子迁移到导带并在价带留下空穴.当Pg-C3N4与Zn0.2Cd0.8S-DETA复合之后,在它们的接触处会形成内部电场,Zn0.2Cd0.8S-DETA导带上的电子和Pg-C3N4价带上的空穴会在内部电场作用下复合.Zn0.2Cd0.8S-DETA价带上的空穴和Pg-C3N4上的电子分别参与氧化还原反应.梯形机制促使电子和空穴在空间上分离,从而具有强氧化还原性.梯形异质结的形成加快了15%Pg-C3N4/Zn0.2Cd0.8S-DETA复合材料中电子-空穴对的分离效率,并减少了电子-空穴对的复合,从而使其具有很优异的光催化性能和稳定性.     

层间距为1.44 nm层状氢氧化苯甲酸锌剥离重组行为研究

层间距为1.44 nm层状氢氧化苯甲酸锌在乙醇、正丙醇、正丁醇介质中可剥离成其基本组成单元纳米层. 用TG-DTA、XRD、SEM、TEM和元素分析等手段研究了剥离的纳米层重组得到样品的结构特征、形貌和化学组成. 结果表明: 水热合成样品和剥离的纳米层重组样品具有相同的层状结构, 它们的化学组成分别为Zn(OH)1.12(C6H5COO)0.88和Zn(OH)1.1(C6H5COO)0.9. 水热合成的纤维状粒子剥离重组后改变成为像纳米带和纳米花粒子形貌.     

静电纺丝技术制备LaCrO4和LaCrO3纳米带及其光催化性质

采用溶胶-凝胶法结合静电纺丝技术制备了PVP/[La(NO3)3|Cr(NO3)3]复合纳米带, 经热处理后得到LaCrO4纳米带和LaCrO3纳米带. 采用TG-DTA, XRD, SEM和EDS等测试手段对样品进行了表征. 结果表明, PVP/[La(NO3)3-Cr(NO3)3]复合纳米带表面光滑, 宽度为(9.1±1.9) μm, 厚度约385 nm; 经600 ℃焙烧后得到单斜独居石型LaCrO4纳米带, 宽度为(2.5±0.5) μm, 厚度约100 nm; 当焙烧温度为650~800 ℃时得到LaCrO3多孔纳米带, 属正交晶系, Pbnm空间群, 经650 ℃焙烧后得到的LaCrO3纳米带呈多孔结构, 带宽为(2.4±0.5) μm, 厚度约90 nm; 经800 ℃焙烧后得到的LaCrO3纳米带部分破碎形成LaCrO3纳米粒子, LaCrO3纳米带宽度约(1.3±0.4) μm, 厚度约90 nm, LaCrO3纳米粒子粒径约80 nm. 以罗丹明B为目标降解物, 研究了不同焙烧温度下产物的光催化性能, 其中800 ℃焙烧后得到的样品在紫外光照射下对罗丹明B的降解效果最好, 光照200 min后罗丹明B的降解率为94.6%.     

聚丙烯酰胺凝胶法合成TbFeO3 纳米颗粒及其可见光催化活性

采用聚丙烯酰胺凝胶法制备了TbFeO3纳米颗粒, 研究了不同络合剂对样品的纯度、 颗粒尺寸及形貌的影响. XRD分析结果表明, 以酒石酸、 柠檬酸或乙二胺四乙酸(EDTA)为络合剂, 在650 ℃下烧结均可制备出单相TbFeO3纳米颗粒, 但产物的平均粒径不同; 而采用乙酸或草酸为络合剂则难以制得纯相样品. SEM观测结果表明, 以酒石酸为络合剂制备的颗粒细小, 均匀、 形貌规整、 呈球状, 平均粒径约为50 nm; 以柠檬酸为络合剂制备的颗粒主要以近球形为主, 颗粒的尺寸分布相对较宽, 平均粒径约为100 nm; 以EDTA为络合剂制备的颗粒主要呈椭球状, 颗粒尺寸较均匀, 但颗粒间存在不同程度的黏连现象, 平均粒径约为110 nm. 这3种样品的BET比表面积分别为15.4, 8.3和6.8 m2/g. 紫外-可见漫反射吸收光谱研究表明, TbFeO3纳米颗粒的带隙为1.95~1.98 eV. 分别以甲基橙(MO)、 罗丹明B(RhB)、 亚甲基蓝(MB)、 酸性品红(AF)和刚果红(CR)5种有机染料为目标降解物, 考察了TbFeO3颗粒的光催化活性. 结果表明, 在可见光辐照下颗粒表现出良好的光催化活性, 其中, 以酒石酸为络合剂制备的样品光催化效果最好.     

静电纺丝技术制备Gd_3Ga_5O_(12)∶Eu~(3+)多孔发光纳米带

采用静电纺丝技术制备了PVP/[Gd(NO3)3+Ga(NO3)3+Eu(NO3)3]复合纳米带,将其进行热处理,得到了Gd3Ga5O12∶Eu3+(简称GGG∶Eu3+)多孔发光纳米带.采用XRD,SEM,TEM,TG-DTA,FTIR和荧光光谱等技术对样品进行了表征.PVP/[Gd(NO3)3+Ga(NO3)3+Eu(NO3)3]复合纳米带为非晶态,经800℃焙烧8h后,获得了单相石榴石型的GGG∶Eu3+纳米带,属于立方晶系,空间群为Ia3d.复合纳米带表面光滑,尺寸均一,平均宽度约10μm,厚度约为100nm,彼此没有交联;经800℃焙烧后GGG∶Eu3+多孔纳米带平均宽度约2.5μm,厚度30nm,长度大于500μm,呈多孔网状多晶结构.当焙烧温度高于700℃时,复合纳米带中DMF、有机物和硝酸盐分解挥发完全,总失重率为93.1%.焙烧温度为800℃时,生成了纯净的无机氧化物.在254nm的紫外光激发下,GGG∶Eu3+纳米带发射出主峰位于591nm的明亮红光,属于Eu3+的5D0→7F1跃迁.对GGG∶Eu3+纳米带形成机理进行了讨论.     

Controlled growth of two-dimensional and one-dimensional ZnO nanostructures on indium tin oxide coated glass by direct electrodeposition

A simple electrochemical deposition technique is used to deposit ZnO nanostructures with diverse morphology directly on ITO-coated glass substrates at 70 degrees C. The concentration of the Zn(NO 3) 2.6H 2O electrolyte is important to controlling the dimensionality of the nanostructures, with formation of one-dimensional (1D) nanospikes and nanopillars (with 50-500 nm diameter) below 0.01 M and of two-dimensional (2D) nanowalls and nanodisks (with 50-100 nm wall/disk thickness) above 0.05 M. Glancing-incidence X-ray diffraction study shows their wurtzite structure and confirms the change in the preferred crystal plane orientation with the dimensionality of ZnO nanostructures. UV-vis spectroscopy reveals a higher transmittance from 2D nanostructures than from 1D nanostructures and their optical direct band gaps estimated to be 3.12-3.27 eV. Depth-profiling X-ray photoemission studies show the presence of Zn(OH) 2 outer layers on the ZnO nanostructures, with a higher Zn(OH) 2 moiety for 2D nanostructures relative to 1D nanostructures. Furthermore, a substantial quantity of Cl (provided by the KCl supporting electrolyte) is detected throughout the 2D nanostructures only. The photoemission data therefore affirm our proposed growth mechanism that involves capping of the preferred [0001] growth direction by Cl (-) ions under fast hydroxylation kinetics condition as observed at a higher Zn(NO 3) 2.6H 2O electrolyte concentration.     

Metal-dependent self-assembly of a microbial surfactant

Small-angle neutron scattering (SANS), cryogenic transmission electron microscopy (cryo-TEM), and dynamic light scattering (DLS) were used to study the metal-dependent phase behavior of microbially produced surfactants-marinobactins B, D, and E (MB, MD, and ME). Marinobactins A-E are siderophores that facilitate Fe(III) acquisition by the source bacterium through the coordination of Fe(III) by the peptidic headgroup. All of the marinobactins have the same six amino acid headgroup but differ in the length and saturation of the monoalkyl fatty acid tail. Fe(III) coordinated to ME (Fe(III)-ME) was found to form micelles with a diameter of approximately 3.5 nm that underwent a supramolecular transformation to produce a monodisperse population of vesicles with an average diameter ranging from approximately 90 to 190 nm upon addition of Cd(II), Zn(II), or La(III). SANS profiles of the transition-metal-induced phase exhibit a Bragg peak at QB approximately 0.11-0.12 A-1 and were fit to a SANS model for multilamellar vesicles that have an interbilayer repeat distance of 2pi/QB approximately 5.6-5.0 nm. Cryo-TEM images of the Zn(II)-induced phase reveals the presence of approximately 100 nm diameter approximately spherical aggregates of uniform electron density. The temperature dependence of the Zn(II)-induced transformation was also investigated as a function of the length and degree of unsaturation of the Fe(III)-marinobactin fatty acid tail. The Cd(II)-, Zn(II)-, and La(III)-induced phase changes have features that are similar to those of the previously reported Fe(III)-induced micelle-to-vesicle transition, and this observation has opened questions regarding the role that Cd(II) and Zn(II) may play in bacterial iron uptake.     

Electrochemical synthesis of gallium nanowires and macroporous structures in an ionic liquid

The electrochemical synthesis of gallium nanostructures in an ionic liquid is presented. Gallium nanowires and macroporous structures were synthesized by the template-assisted electrodeposition in the ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide ([Py(1,4)]TFSA) containing GaCl(3) as the precursor. Track-etched polycarbonate membranes with an average pore diameter of 90 nm and a thickness of 21 μm were used as templates for the nanowire synthesis. Ga nanowires with a length of more than 4 μm and an average diameter corresponding to that of the template's pores were easily obtained by this method. Macroporous structures with an average pore diameter of 600 nm were obtained by the electrochemical deposition of Ga inside polystyrene colloidal crystal templates and the subsequent removal of the template by THF. The macroporous deposit showed a granular morphology with smallest grain sizes of about 40 nm and light reflections. The nanostructures of Ga were characterized by HR-SEM and EDX analysis.     

A vapor-solid strategy to silica sheathed metal nanostructures and microstructures via reactions of metal chlorides with silicon

A facile vapor-solid strategy has been developed to prepare silica-sheathed metal micro/nanostructures with controllable shapes. As examples, silica-sheathed nickel nanowires (diameter approximately 50 nm), microcubes (edge length 1-3 microm), nanocubes (edge length approximately 200 nm) with an epitaxial tail (diameter<100 nm), and 1D assembly structures of nanoparticles (particle diameter<100 nm) as well as silica-sheathed cobalt and copper micro/nanostructures are synthesized. The possible reaction and growth mechanisms of Ni/SiO2 structures are discussed. The method is expected to be applied to a wider range of metals.     

Photocatalytic intercalated material based on HLaNb_2O_7 as host and Cd_(0.8)Zn_(0.2)S as guest

A novel photocatalytic material (Pt,Cd0.8Zn0.2S)/HLaNb2O7 was fabricated by successive intercalation and exchange reactions. The (Pt,Cd0.8Zn0.2S)/HLaNb2O7 possessed a gallery height less than 0.5 nm and showed a broad absorption with wavelength over 370―500 nm. Using (Pt,Cd0.8Zn0.2S)/HLaNb2O7 as catalyst, the photocatalytic H2 evolution was more than 160 cm3·h-1·g-1 in the presence of Na2S as a sacrificial agent under irradiation with wavelength more than 290 nm from a 100-W mercury lamp. Furthermore, the catalyst showed photocatalytic activity even under visible light irradiation.     

Highly luminescent CdSe/Cd(x)Zn(1-x)S quantum dots coated with thickness-controlled SiO2 shell through silanization

A silanization technique of hydrophobic quantum dots (QDs) was applied to SiO(2)-coated CdSe/Cd(x)Zn(1-x)S QDs to precisely control the SiO(2) shell thickness and retain the original high photoluminescence (PL) properties of the QDs. Hydrophobic CdSe/Cd(x)Zn(1-x)S core-shell QDs with PL peak wavelengths of 600 and 652 nm were prepared by a facile organic route by using oleic acid (OA) as a capping agent. The QDs were silanized by using partially hydrolyzed tetraethyl orthosilicate by replacing surface OA. These silanized QDs were subsequently encapsulated in a SiO(2) shell by a reverse micelles synthesis. The silanization plays an important role for the QDs to be coated with a homogeneous SiO(2) shell and retain a high PL efficiency in water. Transmission electron microscopy observation shows that the shells are 1-9 nm with final particle sizes of 10-25 nm, depending on the initial QD size. In the case of short reaction time (6 h), the QDs were coated with a very thin SiO(2) layer because no visible SiO(2) shell was observed but transferred into the water phase. The silica coating does not change the PL peak wavelength of the QDs. The full width at half-maximum of PL was decreased 4 nm after coating for QDs emitting at both 600 and 652 nm. The PL efficiency of the SiO(2)-coated is up to 40%, mainly determined by the initial PL efficiency of the underlying CdSe/Cd(x)Zn(1-x)S QDs.     

Cd(II) sensing in water using novel aromatic iminodiacetate based fluorescent chemosensors

[structure: see text]. Compounds 1 and 2 were designed as fluorescent chemosensors for Cd(II). For both, a selective determination of Cd(II) over Zn(II) was achieved. The fluorescence emission of both was pH-independent and switched off between pH 3-11 in 100% water. Whereas the recognition of Cd(II) at pH 7.4 gave rise to the formation of charge-transfer complexes (exciplexes) for both (lambdamax ca. 500 and 506 nm, respectively), the recognition of Zn(II) only switched on the (monomeric) anthracene emission of 2, while for 1 it was red-shifted (lambdamax = 468 nm).     

Composition/structural evolution and optical properties of ZnO/Zn nanoparticles by laser ablation in liquid media

We present composition-controlled synthesis of ZnO-Zn composite nanoparticles by laser ablation of a zinc metal target in pure water or in aqueous solution of sodium dodecyl sulfate (SDS). By SDS concentration, composition and size of the nanoparticles can be controlled in a wide range. Relative amounts of the components Zn and ZnO, the particle size, and the microstructure can evolve with SDS concentration in solution. High SDS concentration corresponds to high relative amount of Zn nanoparticles existing as the core in the core/shell nanostructures, whereas low SDS concentration leads to high ZnO amount. This was explained by a dynamic mechanism on the basis of the competition between aqueous oxidation and SDS capping protection. Correspondingly, optical absorption spectra evolve from the excitonic peak of ZnO (about 350 nm) to the Zn surface plasmon resonance (about 242 nm) with rise of SDS concentration. A blue (about 450 nm) photoluminescence was observed in the obtained ZnO nanoparticles, which was attributed to existence of interstitial zinc in ZnO lattices. This study has revealed that laser ablation of active metal in liquid media is an appropriate method to synthesize a series of metal oxide semiconductor-metal composite nanoparticles with controlled composition and size.     

Photoluminescence and Raman scattering from catalytically grown Zn(x)Cd(1-x)Se alloy nanowires

Zn(x)Cd(1-x)Se alloy nanowires, with composition x = 0, 0.2, 0.5, 0.7, and 1, have been successfully synthesized by a chemical vapor deposition (CVD) method assisted with laser ablation. The as-synthesized alloy nanowires, 60-150 nm in diameter and several tens of micrometers in length, complied with a typical vapor-liquid-solid (VLS) growth mechanism. The Zn(x)Cd(1-x)Se nanowires are single crystalline revealed from high-resolution transmission electron microscopic (HRTEM) images, selected area electron diffraction (SAED) patterns, and X-ray diffraction (XRD) measurement. Compositions of the alloy nanowires can be adjusted by varying the precursor ratios of the laser ablated target and the CVD deposition temperature. Crystalline structures of the Zn(x)Cd(1-x)Se nanowires are hexagonal wurtzite at x = 0, 0.2, and 0.5 with the [0 1 -1 0] growth direction and zinc blende at x = 0.7 and 1 with the [1 -1 1] growth direction. Energy gaps of the Zn(x)Cd(1-x)Se nanowires, determined from micro-photoluminescence (PL) measurements, change nonlinearly as a quadratic function of x with a bowing parameter of approximately 0.45 eV. Strong PL from the Zn(x)Cd(1-x)Se nanowires can be tuned from red (712 nm) to blue (463 nm) with x varying from 0 to 1 and has demonstrated that the alloy nanowires have potential applications in optical and sensory nanotechnology. Micro-Raman shifts of the longitudinal optical (LO) phonon mode observed in the Zn(x)Cd(1-x)Se nanowires show a one-mode behavior pattern following the prediction of a modified random element isodisplacement (MREI) model.     

Large scale synthesis of stable tricolor Zn(1-x)Cd(x)Se core/multishell nanocrystals via a facile phosphine-free colloidal method

Here we report a new "green" method to synthesize Zn(1-x)Cd(x)Se (x = 0-1) and stable red-green-blue tricolor Zn(1-x)Cd(x)Se core/shell nanocrystals using only low cost, phosphine-free and environmentally friendly reagents. The first excitonic absorption peak and photoluminescence (PL) position of the Zn(1-x)Cd(x)Se nanocrystals (the value of x is in the range 0.005-0.2) can be fixed to any position in the range 456-540 nm. There is no red or blue shift in the entire reaction process. Three similar sizes of alloyed Zn(1-x)Cd(x)Se nanocrystals with blue, green, and yellow emissions were successfully selected as cores to synthesize high quality blue, green, and red core/shell nanocrystal emitters. For the synthesis of core/shell nanocrystals with a high quantum yield (QY) and stability, the selection of shell materials has been proven to be very important. Therefore, alternative protocols have been used to optimize thick shell growth. ZnSe/ZnSe(x)S(1-x) and CdS/Zn(1-x)Cd(x)S have been found as an excellent middle multishell to overcoat between the alloyed Zn(1-x)Cd(x)Se core and ZnS outshell. The QYs of the as-synthesized core/shell alloyed Zn(1-x)Cd(x)Se nanocrystals can reach 40-75%. The Cd content is reduced to less than 0.1% for Zn(1 -x)Cd(x)Se core/shell nanocrystals with emissions in the range 456-540 nm. More than 15 g of high quality Zn(1-x)Cd(x)Se core/shell nanocrystals were prepared successfully in a large scale, one-pot reaction. Importantly, the emissions of such thick multishell nanocrystals are not susceptible to ligand loss and stability in various physiological conditions.