CdTe,核 壳型CdTe/CdS及CdTe/ZnS量子点的合成及表征

在水相中制备了半导体CdTe纳米晶,核 壳型CdTe/CdS和CdTe/ZnS纳米晶（即量子点;QDs）.利用扫描隧道显微镜（STM）和荧光光谱(FS)对合成的纳米晶量子点进行了研究,并且根据FS的数据进行了量子效率的计算.STM的结果表明合成的量子点直径约为3 nm并且分布良好.为了提高量子效率,对Cd2+浓度和Cd2+∶S2－比例等反应条件进行了研究,结果表明随着回流时间的增加,核 壳型量子点CdTe/CdS的量子效率总体上呈下降趋势.CdTe/CdS在pH8.5,Cd2+∶S2－=10∶1（摩尔比）时可获得80.0%的最大量子效率.同时制备了核 壳型量子点CdTe/ZnS,其最大发射波长由551 nm（CdTe）红移到635 nm（CdTe/ZnS）表明量子点的尺寸在增长,但是量子效率下降到14.4%. 当前研究的量子点可适用于生物标记,生物成像,以及基于共振能量转移的生物传感研究.     

水溶性CdTe/CdS纳米晶表面SiO2壳层的反相胶束法包覆

"提出了一种水相中制备CdTe/CdS核壳结构纳米粒子的方法.用Te粉作为碲源,用Na2S作为硫源,在50 ℃下制备了CdTe/CdS核壳结构纳米粒子. 用紫外可见吸收光谱和荧光光谱分析了CdS壳层对CdTe核的影响. 随CdS壳层厚度的增加,紫外可见吸收光谱和荧光光谱均发生了红移. CdS壳层厚度较薄时,CdTe/CdS纳米晶的荧光强度较CdTe纳米粒子有显著提高;而CdS壳层厚度较厚时,CdTe/CdS纳米晶的荧光强度会逐渐降低. 用反相胶束法在CdTe/CdS核壳结构纳米粒子的表面包被一层SiO2,     

低强度飞秒激光激发下CdTe和CdTe/CdS核壳量子点的荧光上转换研究

利用400 nm和800 nm不同波长的低强度飞秒激光,对CdTe和CdTe/CdS核壳量子点溶胶进行激发,研究其稳态和时间分辨荧光性质.800 nm飞秒激光激发下,CdTe和CdTe/CdS核壳量子点产生上转换发光现象,上转换荧光峰与400 nm激发下的荧光峰相比蓝移最多达15 nm,而且蓝移值与荧光量子产率有关.变功率激发确认激发光功率与上转换荧光强度间满足二次方关系,时间分辨荧光的研究表明荧光动力学曲线服从双e指数衰减.提出表面态辅助的双光子吸收模型是低激发强度上转换发光的主要机理.CdTe和CdT 关键词： CdTe量子点 CdTe/CdS核壳量子点 时间分辨荧光 上转换荧光     

CdTe∶Eu量子点的合成及其光学性能研究

采用1-十八烯作为高温反应溶剂,利用氯化铕和磷酸三丁酯制备铕前驱体。分别采用正三辛基膦和碲粉制备的碲前驱体,以及油胺和二水乙酸镉制备的镉前驱体,在200℃合成Eu掺杂Cd Te量子点。实验发现随着反应溶液中Eu的含量上升,Cd Te量子点的荧光峰发生显著红移,但Eu的含量过高则会导致量子点的荧光强度下降。     

巯基琥珀酸包被的CdTe量子点的制备及其在细胞标记中的应用

以巯基琥珀酸(MSA)作为稳定剂,在水溶液中合成稳定的CdTe纳米量子点,用紫外-可见荧光分光光度和荧光光谱方法研究了CdTe量子点的发光特性.并将其与鼠抗人AFP抗体连接制备水溶性CdTe-AFP复合物探针,对人肝癌细胞进行标记和成像.结果表明所制备的CdTe-AFP复合物探针对人肝癌细胞成像清晰,在生物医学领域具有重要的应用价值.     

碲化镉量子点/聚吡咯纳米复合物的发光性质研究

通过原位种子聚合构筑了碲化镉量子点(CdTe QDs)/聚吡咯(PPy)纳米复合物。利用透射电镜、红外光谱及荧光发射光谱对其形貌、结构、光致发光性质进行了测试分析。研究结果表明, 复合物中CdTe量子点结晶良好。复合物中两组分间能级耦合相互作用使量子点表面陷阱态钝化, 从而导致对应CdTe量子点带间跃迁的410 nm发光峰的出现, 显示了复合物作为光电器件材料的潜在应用价值。     

微波辅助表面修饰：大范围可控调节CdTe纳米粒子发光光谱

利用微波辅助合成方法简单快捷地调节水溶液中CdTe纳米晶的发光性质，使其发光光谱可以覆盖整个可见光区，甚至部分扩展到近红外(537～680 nm)．这种光谱调控的原因可能是由于CdTe纳米晶表面形成了核壳结构以及纳米粒子之间形成复杂的纳米组合体．     

微波辐射法制备水溶性CdTe量子点及其光谱学研究

用半胱胺作为稳定剂,采用微波辐射加热的方法快速合成了水溶性的CdTe量子点。吸收光谱和荧光光谱表明所合成的量子点具有优异的发光性能。透射电子显微镜(TEM)和X射线粉末衍射(XRD)表征了量子点的结构和粒径分布。通过荧光发射光谱研究了反应温度、加热时间和配体浓度对量子点晶体生长速度的影响。反应温度提高或稳定剂半胱胺的浓度减小,纳米晶体的生长速度加快。在一定温度下,随着反应时间的延长,量子点发射波长发生红移。与传统的水相回流方法相比微波加热制备水溶性的CdTe量子点具有反应速度快、得到的量子点尺寸分布均匀、半峰宽较窄和量子产率较高等特点。     

水溶性CdTe纳米晶的制备和发光性质的研究

在水相中以巯基乙酸作为稳定剂制备了CdTe纳米晶,用X射线粉末衍射和X射线光电子能谱对其进行了表征,用荧光光谱研究了CdTe纳米晶的生长过程,结果表明,随着回流时间的增加,CdTe半导体纳米晶的粒径和半高全宽逐渐变大,纳米晶的荧光颜色也从绿色逐渐过渡到红色.     

以巯基丙酸为稳定剂的水溶性CdTe量子点的水热合成及表征

以巯基丙酸(MPA)为稳定剂,采用水热合成方法在160 ℃下合成水溶性CdTe量子点。研究了不同反应时间及反应前驱体溶液的不同pH值对合成的CdTe量子点光学性质的影响。结果表明:所制得的CdTe量子点的荧光发射波长在510~661 nm范围内连续可调,并且CdTe量子点的光学性质强烈地依赖于反应前驱体溶液的pH值,最佳pH值为9。透射电子显微镜和X射线衍射分析表明所制备的CdTe量子点的形状接近于球形,粒径分布较均匀。与回流方法制备的水溶性量子点相比,高温条件下的水热合成方法简单,反应时间短,CdTe量子点生长速度快,100 min就可生长到3.5 nm,并且所制得的CdTe量子点荧光强度高,稳定性好,荧光量子产率也较高,最高可达44.6%。     

Studies of the surface structures formed by the alternated electrodeposition of Cd and Te on the low-index planes of Au: II. STM studies

Scanning tunneling microscopy (STM) studies of the alternated deposition of Te and Cd atomic layers on the low-index planes of Au are presented here. These investigations were designed to gain an understanding of the surface chemistry involved in the deposition of CdTe by electrochemical atomic layer epitaxy (ECALE). ECALE is the electrochemical analog of atomic layer epitaxy (ALE). In the present study, the structures formed by the alternated electrodeposition of Te and Cd atomic layers, at underpotential, were examined by STM on the low-index planes of Au.

Deposition of atomic layers of each element were achieved by underpotential deposition (UPD). Studies of the UPD of Cd by STM were not performed due to Cd's instability in aqueous solutions after withdrawal from solution and loss of potential control. Studies of Te UPD were performed, however, since Te is stable in aqueous media without potential control. Ordered Te structures were observed using STM on all three Au low-index planes. Atomic resolution imaging of Cd UPD on Te atomic layers proved more difficult than imaging simple Te deposits, however, ordered CdTe structures were observed on each Au plane. Higher bias voltages were generally required to image the CdTe deposits. On Au(100) the CdTe deposit appears to adopt a structure equivalent to a (100) slice of bulk CdTe (zinc blende), but contracted 10% due to the lattice missmatch on the Au surfaces. Similar structures were observed on the other two low index planes, as well; although Cd-Cd distances were closer to those found in bulk CdTe.     

Synthesis and characterization of brightly photoluminescent CdTe nanocrystals

A new synthesis procedure for the preparation of spherical shaped CdTe nanocrystals (NCs) is presented, exhibiting bright luminescence with exceptionally high quantum efficiency (up to 85%). The growth of these NCs occurs in a non-coordinating solvent, octadecene, with the addition of oleic acid/tri-octylphosphine stabilizers, CdO as a precursor for the Cd monomers and additional Cd metal particles as a supplementary Cd reservoir source. The dependence of the crystalline quality and the optical properties of the CdTe NCs, on the initial Cd:Te precursors’ molar ratio, and the reaction duration were investigated. It was demonstrated that the NCs’ properties improved significantly as the initial Cd:Te molar ratios are increased. The obtained NCs’ properties were correlated with measurements of the Cd⁰ concentration in Cd metal particles, CdTe NCs and in Cd monomer solutions.     

The role of potassium tellurite as tellurium source in mercaptoacetic acid-capped CdTe nanoparticles

Water-soluble CdTe nanoparticles were synthesized in aqueous solution with the assistance of mercaptoacetic acid (MAA) molecules by wet chemical route and microwave-assisted method. A series of cadmium telluride (CdTe) nanoparticles capped with a bifunctional molecule, which contains both thiols and carboxylic acid groups were prepared using different pH values and using potassium tellurite as tellurium source. Thiol-capped nanocrystals of CdTe can be isolated as powders using 2-propanol. The synthesized thiol-capped CdTe were characterized with EDAX, TEM, Raman, FT–IR, UV–Visible absorption, fluorescence spectroscopy and X-ray diffraction (XRD) for the particle size determination and to understand their optical properties. The particles crystallize predominantly in cubic phase with narrow photoluminescence emission. Potassium tellurite as source of tellurium improves the photoluminescence efficiency and also avoids the cumbersome processes associated with H₂Te or NaHTe sources.     

金属离子修饰的ZnS/PAMAM纳米复合材料的荧光性能研究

用荧光分光光度法研究了Zn2+,Mn2+,Cd2+,Na+,K+,Ag+,Cu2+和Pb2+等金属离子修饰的ZnS/PAMAM树形分子纳米复合材料的荧光发射性能。结果表明：不同金属离子修饰效果不同。Zn2+,Mn2+和Cd2+修饰后,ZnS/PAMAM树形分子纳米复合材料的荧光发射强度有不同程度提高;Ag+,Cu2+和Pb2+的修饰对荧光有不同程度的猝灭作用;而Na+和K+的修饰对荧光发射无明显影响。与修饰前相比,Cd2+离子修饰的ZnS/PAMAM树形分子纳米复合材料标记的潜指纹发射的蓝色荧光更加明亮,与背景反差更加明显。这对提高潜指纹的显现精度和准确率有很好的借鉴价值。     

InGaN蓝光与CdTe纳米晶基白光LED

报道了倒装焊InGaN蓝光LED与黄光CdTe纳米晶的复合结构。利用蓝光作为CdTe纳米晶的激发源,通过光的下转换机制,将部分蓝光转化为黄光,复合发射出白光。室温下正向驱动电流为10mA时,发光色品坐标为x=0.29,y=0.30。实验表明,该复合结构白光LED的一大优点在于,复合光的色品坐标几乎不随正向驱动电流大小变化,颜色稳定。     

Studies of the structures formed by the alternated electrodeposition of atomic layers of Cd and Te on the low-index planes of Au: I. LEED and Auger studies

We present here a low energy electron diffraction (LEED) and Auger electron spectroscopy (AES) study of the surface chemistry resulting from electrodeposition of two monolayers of CdTe on the low-index planes of Au by electrochemical atomic layer epitaxy (ECALE). ECALE is the electrochemical analog of atomic layer epitaxy (ALE). In the present study, well-ordered monolayers of CdTe were formed by the alternated electrodeposition of atomic layers of Cd and Te, at underpotential, on all three Au planes. Deposition of the first monolayer of CdTe was performed by depositing Te either oxidatively at underpotential or reductively at underpotential, followed by reductive Cd underpotential deposition (UPD). The structures formed were the same in both cases: Au(100)( , Au(110)(2 × 3)-CdTe, and

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. Varying the initial coverage of Te did not change the resulting CdTe structure, although the higher coverages of Te showed sharper LEED patterns and no emersed oxygen. Deposition of Cd as the first atomic layer followed by oxidative Te UPD resulted in the same structures as those found when Te was used for the first atomic layer. Optimal CdTe monolayers were formed on surfaces where the first atomic layer deposited was homogeneously distributed and of the correct coverage. The correct initial coverage is determined by the coverage needed to complete the subsequently formed CdTe monolayer. On Au(100), an initial coverage of 0.5 appears to be optimal in order to form the Au(100)( . Deposition of a second CdTe monolayer onto the first resulted in structures similar to the first monolayer, but with increased diffuse intensity in the resulting LEED patterns under the conditions used.     

高组分稀磁半导体Cd1-xMnxTe/CdTe超晶格的荧光谱研究

报道用分子束外延(MBE)技术生长的x=0.4,0.8的高组分稀磁半导体Cd1-xMnxTe/CdTe超晶格低温和室温荧光谱研究结果.基态激子跃迁能级荧光谱实验结果显示高组分超晶格中具有高量子效率和高质量光发射.对激子能级随温度的变化进行了详细研究,给出激子跃迁能量的温度系数.激子能级线型的展宽随温度变化关系可用激子-纵向光学声子耦合模型解释.与光调制反射谱实验结果进行了比较.     

Study of influence of metal ions on CdTe/H2O2 chemiluminescence

Water-soluble CdTe nanocrystals (NCs) were synthesized and applied to study the effect of metal ions on chemiluminescence (CL) of the CdTe/H₂O₂ system. The effects of experimental factors, such as pH, particle sizes of CdTe and reagent concentration, on kinetics curve and CL intensity of the CdTe/H₂O₂ system were examined. The results showed that under the optimal conditions Ba²⁺, Ca²⁺, Fe²⁺, Pb²⁺ and Cu²⁺ enhanced the CL intensity, and Cr³⁺, Ni²⁺, Zn²⁺ and Ag⁺ inhibited the CL intensity.     

One-pot synthesis of oleic acid-capped cadmium chalcogenides (CdE: E = Se,Te) nano-crystals

Surface-capped CdSe and CdTe nano-crystals (NCs) have been synthesized using cadmium acetate, oleic acid and respective tri-octylphosphine chalcogenide (TOPE; E = Se/Te) in diphenyl ether (DPE). Well-dispersed CdSe particles showed two absorption bands at the region of 431–34 and 458–60 nm in optical absorption study. A band-edge emission resulted at 515 nm with an excitation energy of 400 nm, in its photoluminescence (PL) spectrum. Similarly, UV–visible absorption study of CdTe revealed an absorption band at <700 nm. The broadened X-ray diffraction (XRD) pattern showed that at higher reaction temperature cubic CdSe but hexagonal CdTe can be obtained with crystallite size of <10 nm. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed that agglomerated particles are of spherical nature. The inter-planar spacing in CdTe was measured to be 0.406 nm, a characteristic of (100) lattice plane in hexagonal CdTe. X-ray photoelectron spectroscopy (XPS) showed that CdSe NCs have better air stability stable than CdTe. Presence of organic moiety around the semiconductor particles was confirmed by infra-red (IR) spectroscopy.     

Synthesis of AS1411-Aptamer-Conjugated CdTe Quantum Dots with High Fluorescence Strength for Probe Labeling Tumor Cells

In this paper, we report microwave-assisted, one-stage synthesis of high-quality functionalized water-soluble cadmium telluride (CdTe) quantum dots (QDs). By selecting sodium tellurite as the Te source, cadmium chloride as the Cd source, mercaptosuccinic acid (MSA) as the capping agent, and a borate-acetic acid buffer solution with a pH range of 5–8, CdTe nanocrystals with four colors (blue to orange) were conveniently prepared at 100 °C under microwave irradiation in less than one hour (reaction time: 10–60 min). The influence of parameters such as the pH, Cd:Te molar ratio, and reaction time on the emission range and quantum yield percentage (QY%) was investigated. The structures and compositions of the prepared CdTe QDs were characterized by transmission electron microscopy, energy-dispersive X-ray spectroscopy, selective area electron diffraction, and X-ray powder diffraction experiments. The formation mechanism of the QDs is discussed in this paper. Furthermore, AS1141-aptamer-conjugated CdTe QDs in the U87MG glioblastoma cell line were assessed with a fluorescence microscope. The obtained results showed that the best conditions for obtaining a high QY of approximately 87 % are a pH of 6, a Cd:Te molar ratio of 5:1, and a 30-min reaction time at 100 °C under microwave irradiation. The results showed that AS1141-aptamer-conjugated CdTe QDs could enter tumor cells efficiently. It could be concluded that a facile high-fluorescence-strength QD conjugated with a DNA aptamer, AS1411, which can recognize the extracellular matrix protein nucleolin, can specifically target U87MG human glioblastoma cells. The qualified AS1411-aptamer-conjugated QDs prepared in this study showed excellent capabilities as nanoprobes for cancer targeting and molecular imaging.