利用离子型Cd源制备ZnSe/CdSe核-壳结构纳米晶

在有机相体系中利用ZnSe前驱体纳米晶制备过程中的富Se环境,以引入Cd2+的方式在相对温和的环境下通过控制Cd2+离子的加入量及调节反应时间,成功制备了ZnSe/CdSe核-壳复合结构纳米晶.利用X射线衍射(XRD)、透射电镜(TEM)、紫外-可见吸收光谱(UV-vis)和荧光光谱(FL)对其结构形貌以及光学性质进行表征和分析的结果表明,CdSe以外延生长的方式包覆在ZnSe纳米晶表面从而形成具有良好结晶性的核-壳复合结构,其荧光发射始终保持良好单色性,同时实现了在500～620nm可见光范围内的连续可调.     

硫脲修饰ZnSe:Cu量子点的水相合成及荧光特性

以3-巯基丙酸为稳定剂在水相中合成了Cu掺杂的ZnSe量子点(QDs), 并利用硫脲(CH₄N₂S)对其进行表面修饰, 制备出核壳结构的ZnSe:Cu/ZnS 量子点. 制得的量子点呈闪锌矿结构, 尺寸约为5 nm, 有较好的分散性, 其荧光发射峰在460 nm左右. 经CH₄N₂S修饰后, 量子点表面形成了宽禁带的ZnS包覆层, 将电子和空穴限域在了ZnSe:Cu 核内, 减少了表面发生非辐射复合的载流子, 显著提高了量子点的荧光强度. 与Na₂S、硫代乙酰胺(TAA)等常用硫源相比, 以CH₄N₂S为硫源制得的ZnSe:Cu/ZnS 量子点壳层厚度可控, 表面钝化效果更好, 显示出更佳的荧光效率和稳定性. ZnSe:Cu/ZnS 量子点经过紫外线照射后消除了表面的悬空键, 进一步提高了其量子产率, 最终获到了具有较好荧光性质的ZnSe:Cu/ZnS量子点.     

CdSe/ZnS量子点敏化太阳能电池电子注入与光伏性能表征

合成了CdSe/ZnS核壳结构量子点(QDs), 将其作为光敏剂吸附在TiO2纳米晶薄膜上, 组装成量子点敏化太阳能电池(QDSSCs), 从电子注入速率和电池性能两方面对QDSSCs进行了表征. 为了定量研究ZnS层包覆对电子注入的影响, 运用飞秒瞬态光谱技术, 测试了包覆ZnS前后, CdSe-TiO₂体系的电子注入速率. 实验测得ZnS包覆前后电子注入速率分别为7.14×10¹¹s^-1和2.38×10^-11s^-1, 可以看出包覆后电子注入速率明显降低, 仅为包覆前的1/3. 电池器件J-V性能测试表明, ZnS作为绝缘层包覆在CdSe的表面有效提高了QDSSCs的填充因子和稳定性, 但同时也导致了效率的降低. 上述结果说明了电子注入速率的降低是导致电池电流和效率下降的重要原因, 为今后优化核壳结构QDSSCs的电流和效率提供了依据.     

水溶性的CdSe/CdS/ZnS量子点的合成及表征

用L-半胱氨酸盐(Cys)作为稳定剂,合成了水溶性的双壳结构的CdSe/CdS/ZnS半导体量子点。吸收光谱和荧光光谱结果表明,双壳结构的CdSe/CdS/ZnS纳米微粒比单一的CdSe核纳米粒子和单核壳结构的CdSe/CdS纳米粒子具有更优异的发光特性。用透射电子显微镜(TEM)、ED、XRD、XPS和FTIR等方法对CdSe核和双壳层的CdSe/CdS/ZnS纳米微粒的结构、分散性及形貌分别进行了表征。     

CdTe/CdS量子点的Ⅰ-Ⅱ型结构转变与荧光性质

制备了壳层厚度可以精确控制的CdTe/CdS核壳量子点, 利用紫外-可见吸收光谱、光致发光光谱、透射电镜和时间分辨光谱等技术, 分析了CdS壳层厚度对CdTe量子点的荧光量子产率和光谱结构的影响规律. 发现了不同于CdSe/CdS, CdSe/ZnS, CdTe/ZnS等核壳量子点的荧光峰展宽、大幅度红移以及荧光寿命大幅度增加现象. 根据能带的位置关系, 随着CdS厚度的增加, CdTe从Ⅰ型结构逐渐过渡到Ⅱ型核壳结构. 对于Ⅱ型CdTe/CdS核壳量子点, 不仅存在CdTe核区导带电子与价带空穴间的直接复合, 还存在CdS壳层导带电子与CdTe核价带空穴界面处的间接复合, 发光机制的变化导致荧光峰的展宽、明显红移和荧光寿命的增加. 当壳层过厚时, 壳层表面新引入的缺陷会阻碍荧光寿命和量子产率的进一步提高.     

ZnS:Mn/ZnS量子点在DNA定量分析中的应用

以巯基乙酸为稳定剂,采用成核掺杂的方法在水溶液中一步制备得到具有核壳结构的ZnS:Mn/ZnS量子点.研究了荧光、室温磷光产生的机理.基于DNA对量子点发光的增强效应,以ZnS:Mn/ZnS量子点作为标记探针建立了测定DNA的荧光、室温磷光的分析方法.考察了量子点浓度、EDC/NHS用量和反应时间等条件对DNA测定的影...     

核壳型SAPO-34/AlPO-18分子筛的制备及生长机理

采用水热法制备了核壳型SAPO-34/AlPO-18分子筛,并运用X射线衍射、扫描电镜和超高分辨场发射扫描电镜等方法对样品进行了表征.结果表明,通过改变实验条件可有效调控壳层AlPO-18纳米晶在SAPO-34晶体表面的生长,从而得到具有不同生长区域、生长取向及紧密度的核壳型SAPO-34/AlPO-18分子筛.超高分辨场发射扫描电镜结果发现,核相SAPO-34晶体的外表面结构与壳层AlPO-18纳米晶的生长性质紧密相关,从而推测出核相晶体外表面微细结构诱导壳层分子筛生长的晶化机理.     

ZnSe:Mn/ZnSe纳米晶体中的Mn~(2+)离子扩散

以ZnSe:Mn/ZnSe纳米晶体为基础,分析了Mn~(2+)离子在纳米晶体中的扩散行为.通过电子顺磁共振(EPR)谱参数确定Mn~(2+)离子处在纳米晶体内部.考虑到合成过程,确定Mn~(2+)离子处于纳米晶体的核壳界面.通过荧光光谱来揭示不同退火温度和退火时间下的纳米晶体的光学性质.不同退火条件情况下纳米晶体中各元素的含量由电感耦合等离子体(ICP)发射光谱得到.随着退火温度的增加和退火时间的延长,相同物质的量的纳米晶体中Mn元素含量逐渐变小直到为零,Zn和Se的含量几乎不变.相同退火温度不同退火时间下的电子透射显微镜照片说明退火对纳米晶体的形貌和粒径几乎没有影响.     

核壳结构CdS/ZnS微米球表面处理与光催化制氢性能的关系

具有高活性和稳定性的半导体光催化材料是太阳能光催化制氢领域的研究热点,其中CdS胶体颗粒催化剂因其合适的禁带宽度和带边位置以及较低的原料价格而广受关注.但它在水溶液中不稳定,易受光腐蚀,因而限制了其应用.目前人们致力于用各种方法提高其稳定性,包括各种纳米结构的应用、复合其他催化剂材料以及不同晶相结构复合.ZnS是一种宽禁宽半导体,禁带宽度为3.6 eV,常被用来与CdS形成固溶体调控其能带结构,从而提高其性能和稳定性.其中核壳结构CdS/ZnS异质结具有骑跨型(I型)能带结构,具有特殊的光学和电学性质,在量子点LED和量子点生物荧光显示剂方面获得关注和应用,同时也显示了良好的光催化性能.研究人员对核壳结构CdS/ZnS异质结材料中ZnS壳层厚度对其光学性能包括荧光效率等的影响进行了研究,然而ZnS壳层厚度、颗粒尺寸及其表面处理对光催化性能影响方面的报道很少.本文发展了一种简易的两步法,制备了核壳结构CdS/ZnS微米球光催化剂.首先采用超声喷雾热分解法制备CdS微米球,然后以水浴法在CdS微米球上生长ZnS壳层.采用扫描电镜(SEM)、X射线衍射(XRD)、紫外-可见吸收光谱(UV-vis)和透射电镜(TEM)对所得样品进行了表征.SEM和TEM结果显示,所得微米球为完整包裹的球形核壳结构;XRD表征证实CdS核与ZnS壳层皆为六角相晶型;光催化性能表征结果显示,该样品的光催化制氢性能远高于单独的CdS微米球以及同法所制的ZnS微米球.通过改变前驱液浓度(Zn源浓度分别为0.2,0.3和0.5 mol/L)获得了三种不同厚度的核壳结构CdS/ZnS微米球,X射线荧光光谱结果证实了其壳层厚度成功调控.UV-vis结果发现,其吸收边由内核CdS决定,受壳层厚度的影响不大.光致荧光发射光谱分析发现,随着壳层厚度的增加,其540 nm处的CdS带边发射峰强度逐渐增大.这可能是由于ZnS壳层对CdS表面缺陷的钝化作用降低了其非辐射复合过程,从而提高了荧光发光效率.光催化制氢性能结果表明,前驱液浓度为0.3 mol/L时合成的核壳结构CdS/ZnS微米球的产氢效率最高.为了进一步提高其光催化效率,采用氮气中高温热处理、水热二次硫化法以及两者共用三种方式对性能最优的微米球进行改性,获得了三种核壳结构CdS/ZnS样品.结果发现,这些改性方法未影响其吸收边,但水热二次硫化法处理以及两者共用处理的样品在540 nm处的光致荧光发射峰强度明显高于未处理的和高温热处理的样品,证实水热二次硫化法处理可以有效地消除其表面缺陷,减少非辐射复合.XRD结果表明其晶型没有发生变化.TEM表征发现,经高温热处理后其壳层发生重结晶,形成颗粒包裹形貌,而经水热二次硫化法处理后其壳层同样发生重结晶,但包裹颗粒的尺寸明显更小.光催化性能测试表明,处理后样品的光催化性能皆优于未处理样品,其中两者共用法处理的样品产氢性能和稳定性最高.     

核壳结构CdS/ZnS微米球表面处理与光催化制氢性能的关系（英文）

具有高活性和稳定性的半导体光催化材料是太阳能光催化制氢领域的研究热点,其中CdS胶体颗粒催化剂因其合适的禁带宽度和带边位置以及较低的原料价格而广受关注.但它在水溶液中不稳定,易受光腐蚀,因而限制了其应用.目前人们致力于用各种方法提高其稳定性,包括各种纳米结构的应用、复合其他催化剂材料以及不同晶相结构复合.ZnS是一种宽禁宽半导体,禁带宽度为3.6 eV,常被用来与CdS形成固溶体调控其能带结构,从而提高其性能和稳定性.其中核壳结构CdS/ZnS异质结具有骑跨型(I型)能带结构,具有特殊的光学和电学性质,在量子点LED和量子点生物荧光显示剂方面获得关注和应用,同时也显示了良好的光催化性能.研究人员对核壳结构CdS/ZnS异质结材料中ZnS壳层厚度对其光学性能包括荧光效率等的影响进行了研究,然而ZnS壳层厚度、颗粒尺寸及其表面处理对光催化性能影响方面的报道很少.本文发展了一种简易的两步法,制备了核壳结构CdS/ZnS微米球光催化剂.首先采用超声喷雾热分解法制备CdS微米球,然后以水浴法在CdS微米球上生长ZnS壳层.采用扫描电镜(SEM)、X射线衍射(XRD)、紫外-可见吸收光谱(UV-vis)和透射电镜(TEM)对所得样品进行了表征.SEM和TEM结果显示,所得微米球为完整包裹的球形核壳结构;XRD表征证实CdS核与ZnS壳层皆为六角相晶型;光催化性能表征结果显示,该样品的光催化制氢性能远高于单独的CdS微米球以及同法所制的ZnS微米球.通过改变前驱液浓度(Zn源浓度分别为0.2,0.3和0.5 mol/L)获得了三种不同厚度的核壳结构CdS/ZnS微米球,X射线荧光光谱结果证实了其壳层厚度成功调控.UV-vis结果发现,其吸收边由内核CdS决定,受壳层厚度的影响不大.光致荧光发射光谱分析发现,随着壳层厚度的增加,其540 nm处的CdS带边发射峰强度逐渐增大.这可能是由于ZnS壳层对CdS表面缺陷的钝化作用降低了其非辐射复合过程,从而提高了荧光发光效率.光催化制氢性能结果表明,前驱液浓度为0.3 mol/L时合成的核壳结构CdS/ZnS微米球的产氢效率最高.为了进一步提高其光催化效率,采用氮气中高温热处理、水热二次硫化法以及两者共用三种方式对性能最优的微米球进行改性,获得了三种核壳结构CdS/ZnS样品.结果发现,这些改性方法未影响其吸收边,但水热二次硫化法处理以及两者共用处理的样品在540 nm处的光致荧光发射峰强度明显高于未处理的和高温热处理的样品,证实水热二次硫化法处理可以有效地消除其表面缺陷,减少非辐射复合.XRD结果表明其晶型没有发生变化.TEM表征发现,经高温热处理后其壳层发生重结晶,形成颗粒包裹形貌,而经水热二次硫化法处理后其壳层同样发生重结晶,但包裹颗粒的尺寸明显更小.光催化性能测试表明,处理后样品的光催化性能皆优于未处理样品,其中两者共用法处理的样品产氢性能和稳定性最高.     

Water-based route to colloidal Mn-doped ZnSe and core/shell ZnSe/ZnS quantum dots

Relatively monodisperse and highly luminescent Mn(2+)-doped zinc blende ZnSe nanocrystals were synthesized in aqueous solution at 100 °C using the nucleation-doping strategy. The effects of the experimental conditions and of the ligand on the synthesis of nanocrystals were investigated systematically. It was found that there were significant effects of molar ratio of precursors and heating time on the optical properties of ZnSe:Mn nanocrystals. Using 3-mercaptopropionic acid as capping ligand afforded 3.1 nm wide ZnSe:Mn quantum dots (QDs) with very low surface defect density and which exhibited the Mn(2+)-related orange luminescence. The post-preparative introduction of a ZnS shell at the surface of the Mn(2+)-doped ZnSe QDs improved their photoluminescence properties, resulting in stronger emission. A 2.5-fold increase in photoluminescence quantum yield (from 3.5 to 9%) and of Mn(2+) ion emission lifetime (from 0.62 to 1.39 ms) have been observed after surface passivation. The size and the structure of these QDs were also corroborated by using transmission electron microscopy, energy dispersive spectroscopy, and X-ray powder diffraction.     

Synthesis and characterization of high-quality ZnS, ZnS:Mn2+, and ZnS:Mn2+/ZnS (core/shell) luminescent nanocrystals

High-quality ZnS, ZnS:Mn2+, and ZnS:Mn2+/ZnS (core/shell) nanocrystals (NCs) were synthesized via a high-boiling solvent process and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), electron paramagnetic resonance (EPR), X-ray photoelectron spectroscopy (XPS), and photoluminescence (PL) spectra. The monodisperse ZnS NCs (size = 8 nm), which self-assembled into several micrometer-sized domains, were achieved by adopting poly(ethylene glycol) (PEG) in the reaction process (without using a size-selection process). The obtained ZnS:Mn2+ and ZnS:Mn2+/ZnS core/shell NCs are highly crystalline and quasimonodisperse with an average particle size of 6.1 and 8.4 nm, respectively. All of the as-formed NCs can be well dispersed in hexane to form stable and clear colloidal solutions, which show strong visible emission (blue for ZnS and red-orange for ZnS:Mn2+ and ZnS:Mn2+/ZnS) under UV excitation. The growth of a ZnS shell on ZnS:Mn2+ NCs, that is, the formation of ZnS:Mn2+/ZnS core/shell NCs, resulted in a 30% enhancement in the PL intensity with respect to that of bare ZnS:Mn2+ NCs due to the elimination of the surface defects.     

CdS:Mn nanocrystals passivated by ZnS: synthesis and luminescent properties

Synthesis and characterization of highly luminescent ZnS-passivated CdS:Mn (CdS:Mn/ZnS) core/shell structured nanocrystals are reported. Mn-doped CdS core nanocrystals are produced ranging from 1.5 to 2.3 nm in diameter with epitaxial ZnS shell of wider band gap via a reverse micelle process. UV irradiation-stimulated photo-oxidation of the ZnS shell results in formation of sulfate (ZnSO(4)) as determined by x-ray photoelectron spectroscopy, which increases the photoluminescence emission intensity and subsequent photostability. Luminescent relaxation lifetime data present two different decay components, consisting of slow decay emission from the Mn center and a fast decay emission from a defect-related center. The impact of the density of surface defect states upon the emission spectra is discussed.     

Facile route to Zn-based II-VI semiconductor spheres, hollow spheres, and core/shell nanocrystals and their optical properties

A convenient chemical conversion method that allows the direct preparation of nanocrystalline ZnE (E = O, S, Se) semiconductor spheres and hollow spheres as well as their core/shell structures is reported. By using monodisperse ZnO nanospheres as a starting reactant and in situ template, ZnS, ZnSe solid and hollow nanospheres, and ZnO/ZnS and ZnO/ZnSe core/shell nanostructures have been obtained through an ultrasound-assisted solution-phase conversion process. The formation mechanism of these nanocrystals is connected with the sonochemical effect of ultrasound irradiation. The photoluminescence and electrogenerated chemiluminescence properties of the as-prepared nanocrystals were investigated.     

On doping CdS/ZnS core/shell nanocrystals with Mn

This paper presents a mechanistic study on the doping of CdS/ZnS core/shell semiconductor nanocrystals with Mn based on a three-step synthesis, which includes host-particle synthesis, Mn-dopant growth, and ZnS-shell growth. We used a combination of electron paramagnetic resonance spectroscopy (EPR) and inductively coupled plasma atomic emission spectroscopy (ICP) to monitor Mn-doping level and growth yield during doping synthesis at both the dopant-growth and ZnS-shell-growth steps. First, our kinetic study shows that Mn adsorption onto the nanocrystal surface includes the formation of weakly and strongly bound Mn. The formation of weakly bound Mn is associated with a chemical equilibrium between adsorbed Mn species on the nanocrystal surface and free Mn species in growth solution, while the formation of strongly bound Mn exhibits first-order kinetics with an activation-energy barrier of 211 +/- 13 kJ/mol. Second, our results demonstrate that both weakly and strongly bound Mn can be removed from the surface of nanocrystals during ZnS-shell growth. The replacement of strongly bound Mn requires a higher temperature than that of weakly bound Mn. The yield of the replacement of strongly bound Mn is strongly dependent on the temperature of ZnS-shell growth. Third, our results show that the Mn-growth yield is not dependent on the size and crystal structure of nanocrystals. All together, these results suggest a mechanism in which nanocrystal doping is determined by the chemical kinetics of three activation-controlled processes: dopant adsorption, replacement, and ZnS-shell growth.     

Ag∶InP/ZnSe纳米晶的合成与生物成像

采用高温热注入法, 以P[N(CH3)2]3为磷源合成了具有近红外荧光的Ag∶InP/ZnSe纳米晶. 采用紫外|可见|近红外吸收光谱(UV|Vis|NIR)、 荧光光谱、 透射电子显微镜(TEM)、 X 射线衍射(XRD)等对产物的结构和光学性质进行了表征, 并分析了Ag掺杂浓度和温度对InP纳米晶荧光性能的影响. 通过调节Ag掺杂浓度和反应温度, 发现当Ag掺杂量为6%, 反应温度为200 ℃时, Ag∶InP纳米晶的发光效率最高. 将制备的Ag∶InP的表面包覆ZnSe, 粒子的荧光效率从原来的20%提高到45%. 将具有近红外荧光的Ag∶InP/ZnSe纳米晶应用于细胞成像, 结果表明制备的荧光纳米晶在细胞成像中清晰可见且毒性较低.     

Poly(MAA-Mn) for Triple-Layer Structure Synthesis of ZnS/ZnS:Mn/SiO2 Phosphors

Methacrylic acid (MAA) was used as a manganese carrier to prepare ZnS/MAA-Mn particles, and ZnS/ZnS:Mn phosphors were formed from ZnS/MAA-Mn by ion substitution through heat treatment. After silica coating on surface by chemical precipitation method with tetraethyl orthosilicate (TEOS), ZnS/ZnS:Mn/SiO₂ phosphors were prepared successfully as a new core/shell structure compound. The thickness of layers was controlled by adjusting concentrations of manganese (II) acetate (Mn(CH₃COO)₂) and TEOS. Structure, morphology, and composition of prepared phosphors were investigated by X-ray diffraction (XRD), transmission electron microscope (TEM), and X-ray photoelectron spectroscopy (XPS), respectively. Photoluminescence (PL) properties of ZnS with different Mn²⁺ content were analyzed by PL spectrometer. PL emission intensity and PL stability were analyzed for evaluating effects of silica coating and Mn²⁺ activator doping. As a result, the structure of two layers could be observed, and optimum composition of ZnS/ZnS:Mn/SiO₂ structure was also obtained.     

硫化锌掺锰/聚乙烯醇复合纳米纤维的制备与表征

利用静电纺丝法与气固反应相结合, 成功地制备了硫化锌掺锰/聚乙烯醇复合纳米纤维, 并对所制备的复合物进行了表征, 探讨了复合物的结构及其性能.     

Encapsulation of ZnS:Mn2+ nanocrystals with diblock copolymers

The encapsulation of the nanocrystalline manganese‐doped zinc sulfide (ZnS:Mn) in poly(styrene‐b‐2vinylpyridine) (PS‐PVP) diblock copolymers is reported. Below the critical micelle concentration in the absence of nanocrystals (NCs), inverse micelles of PS‐PVP were induced by adding ZnS:Mn NCs, the presence of which was confirmed by scanning force microscope and dynamic light scattering. In toluene, a PS‐selective solvent, the less‐soluble PVP blocks preferentially surround the ligand‐coated ZnS:Mn NCs. For PS‐PVP encapsulated ZnS:Mn NCs, the ratio of blue emission to orange emission of ZnS:Mn NCs is dependent on both the concentration of PS‐PVP and the solvent quality. The pyridine of PVP blocks form complexes with the Zn atoms via the nitrogen lone pair and thus the sulfur vacancies are passivated. As a result, the defect‐related blue emission is selectively quenched even when the micelles are not formed. As the concentration of PS‐PVP encapsulating the ZnS:Mn NCs increases, the intensity of blue emission decreases. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3227–3233, 2006     

Size- and shape-controlled synthesis of ZnSe nanocrystals using SeO2 as selenium precursor

Here we report a low-cost and "green" phosphine-free route for the size- and shape-controlled synthesis of high-quality zinc blende (cubic) ZnSe nanocrystals. To avoid the use of expensive and toxic solvents such as trioctylphosphine (TOP) or tributylphosphine (TBP), SeO(2) was dispersed in 1-octadecene (ODE) as a chalcogen precursor. It has been found that the temperature and the surface ligand influenced the nucleation, the reaction speed and the formation of different shapes. Absorption spectroscopy, fluorescence spectroscopy, powder X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used for the characterization of the as-synthesized ZnSe nanocrystals. The size-dependent photoluminescence (PL) range of the as-prepared ZnSe nanocrystals was between 390 and 450 nm, with the PL full width at half-maximum (FWHM) well controlled between 14 and 18 nm and PL quantum yields reached up to 40% at room temperature. Moreover, this new selenium precursor can be used to form tetrapod-shaped ZnSe nanocrystals when zinc acetylacetonate was introduced as the zinc precursor with a one-pot method.