单分散CdS纳米晶/PNIPAM复合水凝胶的制备及其温敏荧光特性

采用液体-固体-溶液法(LSS)制备单分散CdS纳米晶;通过自由基聚合制备单分散CdS纳米晶/聚N-异丙基丙烯酰胺(CdS/PNIPAM)复合温敏水凝胶.采用HRTEM、XRD、FTIR、DSC、PL等对CdS纳米晶、CdS/PNIPAM温敏复合凝胶的微观结构与性能进行了表征,变温荧光光谱研究了温度对凝胶荧光性能的影响.结果表明,CdS纳米晶粒径约为2.8 nm,单分散性良好;复合凝胶的荧光发射强度与环境温度存在一定的关联性,且呈可逆性.     

溶剂热法合成CdS纳米晶及其光学性质研究

以硫脲和醋酸镉为原料,采用溶剂热法在不同的反应介质和温度下合成了CdS纳米晶,比较了单胺与双胺对合成CdS纳米晶形貌的影响。采用透射电镜(TEM)、X射线粉末衍射仪(XRD)和荧光分光光度计(PL)对合成的CdS纳米晶结构和光学性能进行表征。结果表明:反应温度和反应介质对其形貌有影响,在双胺的条件下,60℃时合成了纯相的六方相CdS纳米棒;双胺条件下更易生成纳米棒,且高温下晶体的结晶性更好。PL分析表明,水(溶剂)热法制备的CdS的荧光光谱图与大多数CdS类似,均在440~480 nm和550 nm处存在发射峰,但较宽的发射峰蓝移说明材料的光学性质受到材料形貌和制备方法的影响。     

绿色合成CdSe及制备CdSe-聚氨酯纳米复合发光材料

通过一步法绿色合成了CdSe-聚氨酯(CdSe-PU)纳米复合发光材料.在N2保护下,将单质硒(Se)溶于蓖麻油,以蓖麻油酸作为氧化镉(CdO)的配体,合成硒化镉(CdSe)纳米晶.将聚丙二醇2000和异佛尔酮二异氰酸酯(IPDI)合成的预聚体,加入含CdSe纳米晶的蓖麻油溶液,通过交联作用得到CdSe-PU纳米复合发光材料.采用紫外-可见分光光度计(UV-Vis)、荧光光谱仪(PL)、傅里叶红外光谱仪(FT-IR)、热重分析仪(TGA)、透射电子显微镜(TEM)对CdSe纳米晶和聚氨酯复合材料的结构和性能进行了表征.结果表明:此方法合成的CdSe纳米晶性能良好,能在聚氨酯纳米复合材料中均匀分散且性能稳定,CdSe-PU纳米复合材料耐热性有所提高.     

微波水热法制备CdS单分散纳米球及其形貌控制

采用微波水热法,以醋酸镉(Cd(CH3COO)2.2H2O)为镉源,硫脲(CS(NH2)2)为硫源,制备出了具有单分散球形形貌的CdS纳米晶。应用X射线衍射仪(XRD)、场发射扫描电子显微镜(FE-SEM)、能量色散谱仪(EDS)、高分辨透射电子显微镜(HR-TEM)、紫外可见吸收光谱(UV-Vis)等测试手段对样品的物相、形貌、元素组分及吸光性能进行了表征,并以罗丹明B溶液的降解脱色反应来考察了其的光催化活性。结果表明:随着S/Cd物质的量比(nS/nCd)逐渐增大,产物会出现由刺球链状向分散球形过渡的规律性变化。在一定的nS/nCd比的条件下可以合成出大小均匀、分散性较好的六方相CdS纳米球。样品对可见光有较强吸收,存在着一定的红移现象。在可见光照射下,硫化镉单分散纳米球具有更高的光催化活性。     

纳米晶CuLa3Se5微波溶剂热合成及结构研究

采用微波溶剂热法合成纳米晶CuLa3Se5,具有快速,节能、纯度高、粒度小(平均粒径为20～30 nm)等优点.通过X射线粉末衍射(XRD)、透射电子显微镜(TEM)、扫描电镜能谱分析(EDS)和X射线光电子能谱(XPS)等手段表征其组成.讨论了微波溶剂热合成纳米晶的机制.漫反射紫外-可见吸收光谱(UV-Vis)表明标题化合物禁带宽度为2.27 eV,具有优良的半导体性能.     

表面修饰CdTe量子点的合成及其光学特性

在水相中合成高发光性能的CdTe量子点,研究以巯基乙酸(TGA)为稳定剂对CdTe表面进行修饰,制备在水中分散性良好的纳米晶,通过对CdTe量子点合成反应条件的摸索,掌握了其合成的反应规律.同时用紫外分光光度计、荧光分光光度计和透射电子显微镜对其进行了表征.结果表明,回流时间、n(Cd²⁺):n(HTe^-)、反应物浓度、TGA用量、反应体系pH值,对纳米晶的光学性质具有显著影响.回流2 h制得的CdTe纳米粒子直径约为5 nm,其发射峰窄且对称,表现出良好稳定的光学性质.     

闪锌矿结构CdS纳米晶的制备

以3-巯基丙酸为硫源, 采用水热法制备了尺寸小于10 nm、具有强光致荧光的闪锌矿型立方CdS半导体纳米晶. 用EDS能谱、透射电镜(TEM)、高分辨透射电镜(HRTEM)和XRD对晶体的化学成分、大小及结构进行了表征, 并分析了影响纳米晶尺寸的因素, 研究了闪锌矿型硫化镉纳米晶的荧光激发与发射谱.     

无膦方法合成高质量CdSe纳米晶及其光学性质

以合成的十碳酸镉作为Cd前驱体, 十八烯作为单质硒溶剂, 并添加十八胺作为活性剂, 在无三丁基膦或三辛基膦参与的条件下, 以较低温度制备了具有闪锌矿结构的高质量的CdSe纳米晶. 利用吸收光谱、荧光光谱(PL)、X射线衍射(XRD)、透射电镜(TEM)对不同反应时间得到的CdSe纳米晶进行形貌和光谱性质表征. 实验结果表明, 采用该无膦法只需调控反应时间就可得到粒径均一、分散性好的CdSe纳米晶, 其荧光波长可覆盖470-630 nm的可见光区, 而荧光峰半高宽则始终保持在24-30 nm之间并具有较高的荧光量子产率(535 nm处大于60%). 最后, 对CdSe纳米晶量子产率随反应时间变化的原因进行了分析.     

以含铬类水滑石型层状化合物为模板制备硫化物半导体纳米晶

采用类水滑石型混合金属氢氧化物(CdCr-LDH和ZnCdCr-LDH)为前驱体, 通过气-固反应方法, 制备了根植于层状氢氧化物层板中的硫化镉纳米晶和硫化镉/硫化锌复合纳米晶, 通过改变前驱体(CdCr-LDH)中镉和铬的摩尔比可以调控硫化镉纳米晶的粒径.     

高质量尺寸可调CuFeS2纳米晶的合成与光电性质

制备了单分散性良好且尺寸可调的具有荧光性质的CuFeS2纳米晶,利用紫外-可见吸收光谱(UVVis)、荧光光谱、透射电子显微镜(TEM)、X射线粉末衍射(XRD)、元素分析和光电流测试等技术对其组分和结构进行了表征,分析了CuFeS2纳米晶尺寸变化对吸收光谱和光电响应行为的影响规律.随着CuFeS2纳米晶尺寸增大,其吸收峰位表现出符合量子尺寸效应的相应红移;具有荧光性质的CuFeS2纳米晶可控制备预示其在生物医学成像和光电器件等领域具有应用前景.     

Enhanced optical properties of graphene oxide-Au nanocrystal composites

A simple strategy based on electrostatic interactions was utilized to assemble Au nanocrystals of various morphologies onto graphene oxide (GO). This method allows deposition of metal nanocrystals of different shapes onto GO. The linear and nonlinear optical properties of GO-Au nanocrystal composites have been examined. The extinction spectra of Au nanocrystals became broadened and red-shifted from the visible to the near IR upon formation of GO-Au nanocrystal composites. A more than 4-fold increase in two-photon excitation emission intensity was observed from the GO-Au nanocrystal composites compared to pure Au nanocrystals. The SERS signals of the composites were found to be strongly dependent on the morphology of Au nanocrystals, with SERS enhancement factors ranging from 9 to 20.     

Preparation of Organic Nanoparticle Colloids by Laser Ablation and Their Nonlinear Optical Properties

Suspension of micrometer-sized 1,4-bis(4-methylstyryl)benzene(p-MSB) was converted into colloidal nanocrystal solution by irradiation with an femtosecond laser(800 nm, 1 kHz). The prepared nanocrystals were rectangular with ca. 100 nm in size. The same crystal structure as that of bulk crystals was confirmed by X-ray diffraction measurement. UV-Vis spectra and emission spectra of the nanoparticle dispersions in dichloromethane(poor solvent) were examined. The nanocrystal exhibits large quantum yield(89%). The nonlinear optical properties of the nanocrystals were further studied by Z-scan technique with femtosecond laser duration of 120 fs at a wavelength of 800 nm. The results show that the nanocrystals exhibit strong nonlinear absorption.     

Multifunctional particles: Magnetic nanocrystals and gold nanorods coated with fluorescent dye-doped silica shells

Multifunctional colloidal core-shell nanoparticles of magnetic nanocrystals (of iron oxide or FePt) or gold nanorods encapsulated in silica shells doped with the fluorescent dye, Tris(2,2′-bipyridyl)dichlororuthenium(II) hexahydrate (Rubpy) were synthesized. The as-prepared magnetic nanocrystals are initially hydrophobic and were coated with silica using a microemulsion approach, while the as-prepared gold nanorods are hydrophilic and were coated with silica using a Stöber type of process. Each approach yielded monodisperse nanoparticles with uniform fluorescent dye-doped silica shells. These colloidal heterostructures have the potential to be used as dual-purpose tags—exhibiting a fluorescent signal that could be combined with either dark-field optical contrast (in the case of the gold nanorods), or enhanced contrast in magnetic resonance images (in the case of magnetic nanocrystal cores). The optical and magnetic properties of the fluorescent silica-coated gold nanorods and magnetic nanocrystals are reported.     

CdS量子点的一步法合成及量子产率

以油酸为配体,十八烯为溶剂,采用一步法合成了CdS量子点,研究了反应温度、反应时间和Cd/S的摩尔比对量子点光谱性能的影响.X射线衍射(XRD)和高分辨透射电镜(HRTEM)测试结果表明,所获得的CdS量子点为立方闪锌矿结构,且尺寸分布均一,结晶度高,其较强的带边发光、尖锐的紫外吸收峰以及狭窄的荧光发射峰进一步表明量子...     

Exciton interactions in CdS nanocrystal aggregates in reverse micelle

Here we report the formation and spectroscopic properties of cadmium sulfide (CdS) nanocrystal systems: individual nanocrystal and CdS aggregates. The optical absorption and luminescence spectra of the aggregated CdS nanocrystals and individual nanocrystal show exciton aggregate and individual exciton characteristics. Although it is not Bose-Einstein condensation, such aggregated quantum dots (QDs) seem to supply us opportunity to study the interactions and condensation of excitons in multi-QDs system, not in the separated QDs system.     

Synthesis of highly luminescent glasses incorporating cdte nanocrystals through sol-gel processing

Highly photoluminescent glass was prepared by embedding water-soluble nanocrystals in a glass matrix using a novel sol-gel process. Thiol-stabilized CdTe nanocrystals and aminopropyltrimethoxysilane were found to be the best combination in the preparation. The synthesis process had to be optimized to avoid nanocrystal agglomeration. The nanocrystals thus embedded in the glass matrix did not show any deterioration of the surface condition. The obtained glass combines excellent optical properties of nanocrystals with the high stability of glass; it emits light of various colors with narrow emission spectra and high photoluminescent efficiency (41%).     

Colloidal transition-metal-doped ZnO quantum dots

Methods for introducing new magnetic, optical, electronic, photophysical, or photochemical properties to semiconductor nanocrystals are attracting intense applications-oriented interest. In this communication, we report the preparation and electronic absorption spectroscopy of colloidal ZnO DMS-QDs. Our synthetic procedure involves modification of literature methods known to yield highly crystalline and relatively monodisperse nanocrystals of pure ZnO to allow introduction of transition-metal dopants. We use ligand-field electronic absorption spectroscopy as a dopant-specific optical probe to monitor dopant incorporation during nanocrystal growth and to verify internal substitutional doping in Co2+:ZnO and Ni2+:ZnO DMS-QDs. To the best of our knowledge, these are the first free-standing oxide DMS-QDs reported. The synthesis of colloidal oxide DMS-QDs introduces a new category of magnetic semiconductor materials available for detailed physical study and application in nanotechnology.     

Controlled synthesis of semiconductor nanostructures in the liquid phase

The microstructure (composition, size and shape etc.) of semiconductor nanocrystals determine the electronic density of states of semiconductor nanomaterials and ultimately determine their optical and electrical properties. Semiconductor nanocrystal advanced structures, such as hybrid nanostructures and nanocrystal superlattices, not only integrate the function of individual nanocrystals, but also brings the materials collective and synchronic properties. How to control the monodispersity, composition and structure of as-prepared semiconductor nanocrystals during their syntheses, as well as their furthermore assembly, has been a hot research area in this decade. This critical review focuses on the development of synthetic and assembly methods (techniques) of semiconductor nanocrystals processed in the liquid phase. Emphasis is on the synthesis methodology, microstructure related properties of semiconductor nanocrystals, and their applications (243 references).     

Bioactivation and cell targeting of semiconductor CdSe/ZnS nanocrystals with phytochelatin-related peptides

Synthetic phytochelatin-related peptides are used as an organic coat on the surface of colloidal CdSe/ZnS semiconductor nanocrystals synthesized from hydrophobic coordinating trioctyl phosphine oxide (TOPO) solvents. The peptides are designed to bind to the nanocrystals via a C-terminal adhesive domain. This adhesive domain, composed of multiple repeats of cysteines pairs flanked by hydrophobic 3-cyclohexylalanines, is followed by a flexible hydrophilic linker domain to which various bio-affinity tags can be attached. This surface coating chemistry results in small, buffer soluble, monodisperse peptide-coated nanoparticles with high colloidal stability and ensemble photophysical properties similar to those of TOPO-coated nanocrystals. Various peptide coatings are used to modulate the nanocrystal surface properties and to bioactivate the nanoparticles. CdSe/ZnS nanocrystals coated with biotinylated peptides efficiently bind to streptavidin and are specifically targeted to GPI-anchored avidin-CD14 chimeric proteins expressed on the membranes of live HeLa cells. This peptide coating surface chemistry provides a novel approach for the production of biocompatible photoluminescent nanocrystal probes.