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。     

水溶性CdSe/CdS量子点的合成及其与牛血清蛋白的共轭作用

用巯基乙酸(TGA)作为稳定剂，合成了水溶性的CdSe和核壳结构的CdSe/CdS半导体量子点。吸收光谱和荧光光谱研究表明，核壳结构的CdSe/CdS半导体量子点比单一的CdSe量子点具有更优异的发光特性。用TEM、电子衍射(ED)和XPS分别表征了CdSe和CdSe/CdS纳米微粒的结构、形貌及分散性。红外光谱和核磁共振谱证实了巯基乙酸分子中的硫原子和氧原子与纳米微粒表面的金属离子发生了配位作用。在pH值为7.4的条件下，将合成的CdSe和CdSe/CdS量子点直接与牛血清白蛋白(BSA)相互作用。实验发现，两种量子点均对BSA的荧光产生较强的静态猝灭作用；而BSA对两种量子点的荧光则具有显著的荧光增敏作用，存在BSA时CdSe/CdS量子点的荧光增强是不存在BSA时体系荧光强度的3倍。     

水溶性CdSe/CdS核壳纳米粒子制备的影响因素及其对CdSe/CdS光谱特性的影响

以半胱氨酸镉配合物为前体, 在水溶液中合成CdSe纳米粒子, 以CdS对其表面进行修饰, 得到具有核壳结构的CdSe/CdS 纳米粒子. 采用XRD, TEM表征其结构及形貌; 以荧光光谱研究了时间、pH值、壳量、壳前体加入方式、稳定剂用量等因素对CdSe/CdS光谱特性的影响.     

聚合物为模板制备CdS, ZnS及其掺杂纳米材料

以聚苯乙烯-马来酸酐为模板,合成了CdS,CdS︰Mn,ZnS,ZnS︰Mn及ZnS︰Tb纳米微粒.紫外吸收光谱表明所得微粒尺寸均匀,TEM结果显示CdS纳米微粒的尺寸为2.5 nm.从荧光光谱观察到掺杂离子的特征发射峰,证实了基质到掺杂离子的能量传递.通过红外光谱研究了聚合物与金属离子的键合作用,金属离子首先与聚合物的羧基配位,生成硫化物纳米微粒后,聚合物又包覆在纳米微粒的表面形成保护层.     

硫脲表面修饰的ZnS∶Cd纳米晶的合成及表征

采用硫脲做为表面修饰剂,合成了硫脲表面修饰的掺杂Cd2 的ZnS纳米晶(ZnS∶Cd/SC(NH2)2),用X射线粉末衍射、透射电子显微镜、红外光谱以及荧光光谱等手段进行了表征.实验结果表明,Cd2 掺入了ZnS纳米晶中,硫脲分子中的S原子与该纳米晶表面的金属离子存在配位作用,ZnS∶Cd/SC(NH2)2纳米晶为分散性较好、平均粒径7 nm的球形粒子且具有良好的荧光性质.     

光谱法研究CdSe/CdS/ZnS量子点与壳聚糖的复合

通过CdSe/CdS/ZnS量子点与壳聚糖之间的静电作用,用共混法制备了壳聚糖-CdSe/CdS/ZnS复合物.用荧光光谱、紫外-可见光谱、红外光谱对所得的壳聚糖-CdSe/CdS/ZnS复合物进行了表征.研究结果表明:壳聚糖-CdSe/CdS/ZnS复合物具有良好的光学性能.     

光度法研究L-半胱氨酸修饰的ZnS纳米粒子与牛血红蛋白的作用

L-半胱氨酸;ZnS纳米粒子;牛血红蛋白;紫外光谱;荧光光谱;FTIR-ATR     

表面修饰CdS和(CdS)ZnS纳米晶的性能研究

在水相中合成了CdS纳米微粒,以ZnS对其进行表面修饰,得到具有核壳结构的(CdS)ZnS水溶性纳米晶。采用红外光谱、X射线衍射(XRD)、透射电镜(TEM)表征其粒度和形貌,紫外-可见吸收光谱(UV)、荧光光谱表征其光学特性。制得的CdS近似呈球形,直径为8nm;CdS纳米颗粒表面经ZnS修饰后,其荧光发射峰强度显著增强,表面态发射减弱。     

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.     

硫脲表面修饰的ZnS:Cd纳米晶的合成及表征

采用硫脲做为表面修饰剂，合成了硫脲表面修饰的掺杂Cd^2＋的ZnS纳米晶（ZnS：CA／SC（NH2）2），用X射线粉末衍射、透射电子显微镜、红外光谱以及荧光光谱等手段进行了表征．实验结果表明，CA抖掺入了ZnS纳米晶中，硫脲分子中的S原子与该纳米晶表面的金属离子存在配位作用，ZnS：CA／SC（NH2）2纳米晶为分散性较好、平均粒径7nm的球形粒子且具有良好的荧光性质．     

Sol-Gel Synthesis of Hybrid Organic-Inorganic Monoliths Doped with Colloidal CdSe/ZnS Core-Shell Nanocrystals

Colloidal CdSe/ZnS core-shell nanocrystals, with a narrow size distribution, were dispersed in a hybrid sol resulting from the hydrolysis of tetraethylorthosilicate and 3-glycidoxypropyltrimethoxysilane (GLYMO). In order to reduce the gelation time and the exposure of the nanoparticles to air, several catalysts of the GLYMO epoxy ring opening were employed for the sol preparation, such as imidazole, methyl-imidazole, pyridine, benzylamine, propylamine. The role of the various catalysts was monitored by optical absorption measurements in the near infrared region, by observing the evolution of the epoxy bands. Imidazole was found to provide the fastest gelation and the best results in terms of bubble disappearance from the gel structure. The variation in the optical properties of the semiconductor nanoparticles embedded in the matrix was monitored as a function of the gelation time and was compared to the optical absorption and photoluminescence spectra of the nanoparticles dissolved in a chloroform solution. A decrease in the gelation-time results in a closer resemblance between the optical properties of the CdSe/ZnS doped monoliths and those of the particles dissolved in the solvent, before incorporation in the matrix. The photoluminescence of the CdSe/ZnS nanocrystals is not bleached after they are trapped in the glassy matrix.     

核-壳结构CdSe/ZnS量子点的制备、硫醇修饰及其光学性能

采用高温有机相包覆技术制备了CdSe/ZnS核壳结构量子点材料,考察了包覆量对量子点材料的光学性能的影响,研究了含脂肪链和芳香基的双硫醇分子1,4-苯二甲硫醇和1,8-辛二硫醇对于具有核-壳结构的CdSe/ZnS量子点材料的修饰作用,考察了修饰作用对于量子点的量子效率和荧光强度等光学性能的影响.实验结果表明:随着硫化锌包覆量的增加,量子点的量子效率及其荧光发射强度明显提高;硫醇的修饰能显著增强量子点的发光强度,随着硫醇浓度的增加,其发光性能增强,但是达到一定程度后,光学性能基本不随硫醇浓度的变化而变化.根据固体核磁共振等实验结果推测:硫醇分子可能部分替代了量子点体系中的正三辛基氧膦配体,稳定了量子点体系,对量子点起修饰保护作用,从而提高了量子点的光学性能.     

核壳结构CdS/ZnS纳米微粒的制备与光学特性

CdS and CdS/ZnS core-shell structure nano particles were synthesized in micro emulsion, and characterized by X-ray diffraction(XRD), transmission electron microscopy (TEM), UV absorption spectra and PL. The average diameter of CdS was about 3.3 nm, and CdS/ZnS core-shell structure was confirmed by XRD and UV. Considering the optical properties of CdS/ZnS core-shell structure nanoparticles which have different ZnS shell thickness, the UV absorption edge of CdS/ZnS becomes as lightred-shift with the thickness of ZnS layer increasing, and the absorption of shortwave band is strongly enhanced at the same time. The PL spectra indicate that ZnS shell layer can greatly eliminate surface defects of CdS nanoparticles and make its band-edge directed recombination increased, and the luminous efficiency of CdS is improved greatly when it has appropriate shell thickness.     

Crafting Core/Graded Shell–Shell Quantum Dots with Suppressed Re‐absorption and Tunable Stokes Shift as High Optical Gain Materials

The key to utilizing quantum dots (QDs) as lasing media is to effectively reduce non‐radiative processes, such as Auger recombination and surface trapping. A robust strategy to craft a set of CdSe/Cd_1?xZn_xSe_1?yS_y/ZnS core/graded shell–shell QDs with suppressed re‐absorption, reduced Auger recombination rate, and tunable Stokes shift is presented. In sharp contrast to conventional CdSe/ZnS QDs, which have a large energy level mismatch between CdSe and ZnS and thus show strong re‐absorption and a constrained Stokes shift, the as‐synthesized CdSe/Cd_1?xZn_xSe_1?yS_y/ZnS QDs exhibited the suppressed re‐absorption of CdSe core and tunable Stokes shift as a direct consequence of the delocalization of the electron wavefunction over the entire QD. Such Stokes shift‐engineered QDs with suppressed re‐absorption may represent an important class of building blocks for use in lasers, light emitting diodes, solar concentrators, and parity‐time symmetry materials and devices.     

Synthesis and characterization of photoluminescent In-doped CdSe nanoparticles

Indium-doped CdSe nanoparticles have been synthesized and characterized. Their light absorption, photoluminescence, and structure are similar to undoped CdSe nanoparticles. The greater part of the In associated with the nanoparticles is removed when the nanoparticles undergo ligand exchange by pyridine. As observed with undoped nanoparticles, a ZnS capping layer on the indium-doped nanoparticles results in enhanced nanocrystal photoluminescence. Also, the ZnS cap enhances the retention of In by the nanoparticles. Elemental analysis shows ligand exchange causes CdSe to be lost and capping with ZnS results in the loss of Se. We conclude that In-doped nanoparticles have most of the In on their surface, capping helps the nanoparticles retain the In, and they do not have altered electronic properties.     

Optical properties of CdSe and CdSe/ZnS quantum dots dispersed in solvents of different polarity

Original organic capping TOPO/TOP groups of CdSe and CdSe/ZnS quantum dots (QDs), from mother solution were replaced with 2_mercaptoethanol, which was chosen as model compound, in order to achieve water solubility. Obtained water dispersions of CdSe and CdSe/ZnS QDs were characterized by UV/VIS absorption and luminescence techniques. Luminescence measurements revealed that bare cores are very sensitive to surface capping, transfer into water diminished emission intensity. Core/shell, CdSe/ZnS, QDs are much more resistant to changes of the capping and solvent, and significant part of emission intensity was preserved in water. The article is published in the original.     

Aqueous synthesis of glutathione-capped CdTe/CdS/ZnS and CdTe/CdSe/ZnS core/shell/shell nanocrystal heterostructures

Here we demonstrate the aqueous synthesis of colloidal nanocrystal heterostructures consisting of the CdTe core encapsulated by CdS/ZnS or CdSe/ZnS shells using glutathione (GSH), a tripeptide, as the capping ligand. The inner CdTe/CdS and CdTe/CdSe heterostructures have type-I, quasi-type-II, or type-II band offsets depending on the core size and shell thickness, and the outer CdS/ZnS and CdSe/ZnS structures have type-I band offsets. The emission maxima of the assembled heterostructures were found to be dependent on the CdTe core size, with a wider range of spectral tunability observed for the smaller cores. Because of encapsulation effects, the formation of successive shells resulted in a considerable increase in the photoluminescence quantum yield; however, identifying optimal shell thicknesses was required to achieve the maximum quantum yield. Photoluminescence lifetime measurements revealed that the decrease in the quantum yield of thick-shell nanocrystals was caused by a substantial decrease in the radiative rate constant. By tuning the diameter of the core and the thickness of each shell, a broad range of high quantum yield (up to 45%) nanocrystal heterostructures with emission ranging from visible to NIR wavelengths (500-730 nm) were obtained. This versatile route to engineering the optical properties of nanocrystal heterostructures will provide new opportunities for applications in bioimaging and biolabeling.     

用CdSe/ZnS量子点提高体异质结有机太阳电池的效率

通过掺杂吸收光谱在可见光波段的量子点可提高聚合物对可见光的吸收,因此掺杂CdSe/ZnS核-壳结构量子点(CQDs)能提高聚(3-己基噻吩):[6,6]-苯基-C61-丁酸甲酯(P3HT:PCBM)体异质结太阳电池的能量转换效率.本文研究了CdSe/ZnS量子点在P3HT:PCBM中的不同掺杂比例及其表面配体对太阳电池光伏性能的影响,优化器件ITO(氧化铟锡)/PEDOT:PSS(聚(3,4-乙撑二氧噻吩:聚苯乙烯磺酸)/P3HT:PCBM:(CdSe/ZnS)/Al的能量转换效率达到了3.99%,与相同条件下没有掺杂量子点的参考器件ITO/PEDOT:PSS/P3HT:PCBM/Al相比,其能量转换效率提高了45.1%.