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.     

CdTe纳米晶及层状纳米晶薄膜的生长及其光荧光性质

用湿化学法在水溶液中合成了单分散的、大小尺寸可控的、巯基包裹的胶体CdTe纳米晶体,并利用CdTe纳米晶体和双功能分子poly（diallyldimethylammonium chloride）（PDDA）在Si衬底表面自组织生长了有序的层状纳米晶薄膜,荧光光谱研究了层状纳米晶体之间的共振能量迁移过程.结果表明：层状自组织生长的样品中纳米晶粒的间隔几乎一样,表明它们是有序排列的;而用直接干燥形成的样品中,小尺寸和大尺寸的纳米晶体之间间隔较短,发生荧光共振能量迁移,较小尺寸的纳米晶粒荧光峰（即波长较短处的晶 关键词： CdTe纳米晶体 量子限制效应 共振能量迁移     

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.     

二氧化钛胶体及其自组装薄膜的光谱分析

水解钛酸四丁酯制备了二氧化钛胶体;采用静电自组装技术制备了聚电解质与二氧化钛胶体的复合薄膜;采用吸收光谱和荧光光谱对二氧化钛胶体及其复合薄膜进行了表征。吸收光谱显示,胶体的吸收带边蓝移,显示出量子尺寸效应,胶体的荧光光谱出现了多个发光带,最短发光波长位于371nm,发光主要集中在蓝光区域内;在252nm光源激发下。复合薄膜的发射谱带具有二氧化钛水溶胶的发射谱带的特征,荧光发射主要来源于二氧化钛,聚电解质的引入对复合薄膜的光致发光特性有一定影响。     

CdSe:Nd纳米晶及CdSe:Nd@SiO2核壳结构的合成及发光性能

利用有机相法合成Nd³⁺掺杂CdSe纳米晶（CdSe∶Nd）,通过X射线粉末衍射（XRD）、透射电镜（TEM）、紫外吸收光光谱及荧光光谱表征,证明Nd³⁺已经成功掺入到CdSe的晶格中。与纯CdSe纳米晶相比,CdSe∶Nd纳米晶的结构仍为立方晶型,且形貌近似球形,均匀分散,粒径约为2~4 nm。紫外吸收峰和荧光发射峰都发生红移,而且掺杂后的CdSe∶Nd纳米晶量子产率也提高,这可能是由于掺杂Nd³⁺引入了新的杂质能级,带隙减小。为了实现CdSe∶Nd纳米晶的可加工性和功能性,通过微乳法合成SiO₂壳包覆的CdSe∶Nd纳米球（CdSe∶Nd@SiO₂纳米球）,CdSe∶Nd@SiO₂纳米球呈均匀球形,直径约为100~115 nm,并且包壳后的CdSe∶Nd@SiO₂纳米球发射峰（581 nm）与CdSe∶Nd纳米晶（598 nm）相比,发光强度提高且发射峰蓝移,蓝移约为17 nm,可能是因为SiO₂壳可以减少纳米晶表面的非辐射跃迁以及改善表面缺陷导致的。     

多层纳米Au/DPO薄膜的荧光特性

在低压直流溅射沉积的纳米Au薄膜表面喷涂有机固体晶体2,5-二苯基恶唑（DPO）,制成具有（Au+DPO）单元结构的多层纳米薄膜。利用XRD表征多层纳米薄膜的晶体结构,通过SEM表征各层薄膜的表面形貌,并测试了多层纳米薄膜的紫外荧光特性。与纯DPO薄膜相比,多层纳米薄膜的紫外荧光峰出现了5 nm的蓝移,而且DPO荧光峰形貌发生改变。在多层膜中,DPO薄膜的荧光强度与薄膜层数成反比关系,而纳米Au膜的荧光强度与薄膜层数成正比关系。SEM与XRD测试结果表明,多层薄膜中的DPO薄膜随着薄膜层数的增加逐渐成为无定型结构。DPO薄膜与纳米Au膜相互作用,导致其晶体结构异于单层薄膜,进而改变了其荧光特性。     

ZnO纳米晶/巯基乙酸复合膜的荧光特性

用自组装方法将巯基乙酸(MPA)与ZnO纳米晶薄膜(ZDF)通过共价键偶联到一起,形成纳米晶／巯基乙酸复合膜(ZDF／MPA)。采用发光光谱和XPS电子能谱技术,研究了ZDF／MPA的荧光特性以及它们之间的能量传递机制。研究发现ZDF／MPA中ZnO自由激子发光和束缚激子发光强度随着巯基乙酸的浓度增大而分别呈现不同的非线性减弱关系,当巯基乙酸达到一定的浓度量时,ZnO荧光完全消失。研究表明：ZnO纳米薄膜与MPA之间能够发生成键作用,并且在成键之后发生了能量传递。     

单晶硅表面有机硅烷/Ag2O纳米微粒复合自组装膜的制备和表征

利用分子自组装成膜技术 ,在单晶硅表面制备了有机硅烷 /Ag2 O纳米微粒复合膜 .应用接触角测定仪、原子力显微镜和X射线光电子能谱仪分析表征了薄膜的组成和结构 .结果表明 ,通过硅烷偶联剂 3 氨丙基 三乙氧基硅烷在单晶硅基底表面的成功组装 ,获得了较为均匀的硅烷化表面 ,而Ag2 O纳米微粒可在硅烷化表面成功地进行组装 ,并呈亚单层排布     

过渡金属硫化物纳米晶的溶剂热合成与表征

以硝酸钴（Co(NO3)2•6H2O）、硝酸铁（Fe(NO3)3•6H2O）和硫脲为原料,在同一混合溶剂（乙二醇和水）中通过控制两种溶剂的比例（1:2; 4:1）,利用溶剂热法在180℃分别恒温制备了硫化钴（CoS1.097）和硫化铁（Fe3S4）两种纳米晶。用X-射线衍射（XRD）、透射电镜（TEM）对样品组成、粒径和表面形貌进行了表征,荧光光谱对其荧光性质进行了测量。结果表明,所得样品分别为六方相的CoS1.097和立方相的Fe3S4纳米粉末。在此基础上,对影响两种纳米晶形成的主要因素进行了初步的分析和讨论。     

核-壳结构ZnS:Tb/CdS纳米晶的电致发光

利用微乳液方法合成出粒径为4nm的核．壳结构ZnS：Tb／CdS纳米晶。用XRD、TEM及荧光光谱等手段对合成的纳米晶的结构、形态和光学特性分别进行了表征。将ZnS：Tb／CdS纳米晶制作成有机-无机杂化结构电致发光器件,其结构为ITO／poly（3,4-ethylene dioxythiophene）：poly（styrene sulfonate）（PEDOT-PSS）（70nm）／poly（vinyleobarzale）（PVK）（100nm）／ZnS：Tb／CdS纳米晶（120nm）／2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline（BCP）（30nm）／LiF（1．0nm）／Al（100nm）。当驱动电压为13V时,可以测到Tb^3＋离子的两个特征峰。在电致发光光谱中未测到聚合物PVK的发光,说明电子和空穴是在纳米晶层上复合的。当驱动电压为25V时,得到器件的最大亮度为19cd／m^2。     

Size-dependent photo-induced shift of the first exciton band in CdTe quantum dots in glass prepared by a two-stage heat-treatment process

CdTe nanocrystals were grown from commercially available RG850 Schott filter glass by two-step heat-treatment process which almost doubles the particle to matrix volume fraction. A calculation shows that a quantized-state effective mass model in the strong confinement regime might be used to deduce the average radius for the nanocrystals larger than 2 nm in radius from the energetic position of the first exciton peak in optical absorption spectrum. Size-induced shift of ∼360 meV in the first exciton peak position was observed. The steady state photoluminescence spectra exhibit a broad band red shifted relative to the first exciton band, which indicates the existence of shallow trap states. The non-linear optical properties of CdTe nanocrystals were studied by room temperature resonant photoabsorption spectroscopy. The differential absorption spectra had three-lobed structure whose size-dependent evolution was explained by bleaching of the absorption, red shift and broadening in the Gaussian absorption band used to fit the first exciton peak. A maximum red shift of 2.32 meV for the average nanocrystal radius of 4.65 nm was estimated by fitting the photomodulation spectra with a combination of first and second derivative Gaussian absorption bands. We presume that the red shift is induced by the electric field of trapped charges in surface states. Internal electric field strengths of 23 and 65 kV/cm were predicted for the average nanocrystal radii of 3.95 and 4.65 nm, respectively, with the help of second-order perturbation theory in the strong confinement limit.     

纳米ZnO微晶的合成及其发光特性

以醋酸锌和尿素为主要原料,利用沉淀-水热法一步合成了纳米ZnO微晶。用XRD,TEM,FTIR等测试技术及光致发光光谱(PL)对纳米ZnO微晶进行了表征,并对其发光特性进行了分析。研究表明：该合成方法操作简单,得到的纳米ZnO颗粒基本无团聚,结晶性较好,平均粒径约为17.2 nm,并在500～750 nm范围内出现宽的PL峰, 呈现出纳米材料的发光特征。     

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%。     

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.     

Effect of branching of tetrapod-shaped CdTe/CdSe nanocrystal heterostructures on their luminescence

We have studied the CdTe/CdSe tetrapod-shaped nanocrystal heterostructures with the use of photoluminescence spectra measurements and time-correlated single photon counting technique. The tetrapods were grown to have CdTe arms with different thickness of the CdSe shell. We have observed non-exponential photoluminescence decay of excited tetrapod-nanocrystals and proposed kinetic theory based on the branched crystal morphology and on the assumption about a potential barrier in the junction point of tetrapod. Analysis of studied nanocrystal behavior gives an evidence for tetrapods to behave as four weakly connected quantum wells. This interesting effect might find applications in nanoelectronics.     

One-step synthesis of CdTe branched nanowires and nanorod arrays

Single crystalline CdTe branched nanowires and well-aligned nanorod arrays were simultaneously synthesized by a simple chemical vapor deposition (CVD) technique. X-ray diffraction (XRD), scanning electronic microscopy (SEM), transmission electronic microscopy (TEM) and selected area electronic diffraction (SAED) were used to study the crystalline structure, composition and morphology of different samples. Vapor-liquid-solid (VLS) and vapor-solid (VS) processes were proposed for the formation of the CdTe branched nanowires and nanorod arrays, respectively. As-grown CdTe nanorod arrays show a strong red emission band centered at about 620 nm, which can be well fitted by two Gaussian curves centered at 610 nm and 635 nm, respectively.     

Gd2O3:Eu纳米晶的制备及其光谱性质研究

以EDTA为络合剂，聚乙二醇为有机分散剂，用络合溶胶—凝胶法制备出Gd2O3:Eu纳米晶。用XRD，SEM，X—射线能量色散谱仪(EDS)，荧光分光光度计等分析手段对Gd2O3:Eu的纳米晶结构、形貌、组分的均匀性以及发光特性进行了研究。结果表明：EDTA—M凝胶仅在800℃焙烧即可得到颗粒细小、组分均匀、纯立方相的Gd2O3:Eu纳米晶，颗粒基本呈球形，粒径为30nm左右。对样品的激发光谱、发射光谱测定表明：Gd2O3:Eu纳米晶在269nm光激发下发红光，发射光谱谱峰在611nm，与体材料基本相同；激发光谱中电荷迁移带(CTB)明显红移，从体材料的255nm移至269nm，移动了约14nm；猝灭浓度从体材料的6％提高到8％。     

Synthesis and optical characterization of nanocrystalline CdTe thin films

From several years the study of binary compounds has been intensified in order to find new materials for solar photocells. The development of thin film solar cells is an active area of research at this time. Much attention has been paid to the development of low cost, high efficiency thin film solar cells. CdTe is one of the suitable candidates for the production of thin film solar cells due to its ideal band gap, high absorption coefficient. The present work deals with thickness dependent study of CdTe thin films. Nanocrystalline CdTe bulk powder was synthesized by wet chemical route at pH≈11.2 using cadmium chloride and potassium telluride as starting materials. The product sample was characterized by transmission electron microscope, X-ray diffraction and scanning electron microscope. The structural characteristics studied by X-ray diffraction showed that the films are polycrystalline in nature. CdTe thin films with thickness 40, 60, 80 and 100 nm were prepared on glass substrates by using thermal evaporation onto glass substrate under a vacuum of 10⁻⁶ Torr. The optical constants (absorption coefficient, optical band gap, refractive index, extinction coefficient, real and imaginary part of dielectric constant) of CdTe thin films was studied as a function of photon energy in the wavelength region 400–2000 nm. Analysis of the optical absorption data shows that the rule of direct transitions predominates. It has been found that the absorption coefficient, refractive index (n) and extinction coefficient (k) decreases while the values of optical band gap increase with an increase in thickness from 40 to 100 nm, which can be explained qualitatively by a thickness dependence of the grain size through decrease in grain boundary barrier height with grain size.     

Influence of different stabilizers on the optical and nonlinear optical properties of CdTe nanoparticles

CdTe semiconductor nanocrystals were synthesized with three different stabilizers: Mercaptoacetic Acid (MAA), Mercaptopropionic Acid (MPA) and 2-Mercaptoethanol (ME) at pH ≈ 11.2 by wet chemical route using potassium tellurite and cadmium chloride as starting materials. The effect of capping agent on the preparation of these samples was evaluated using UV-Visible absorption and photoluminescence analysis. With the same reaction time but with different stabilizers, nanocrystals of different diameters were obtained. The average full width at half maximum of the photoluminescence spectra was about 69 nm which indicates that the monodispersity was quite good. The particle size was calculated by Debye-Scherrer equation from XRD data. Further characterization studies such as FT-IR and optical nonlinearity studies on the samples were carried out and the results are discussed.     

荧光光谱法研究Eu~(3+)在拟薄水铝石纳米胶粒表面的吸附

拟薄水铝石作为前驱体,加入胶溶剂HNO3调节pH 2.0得到胶粒大小～60 nm的稳定胶体.将Eu(NO3)2溶液加入拟薄水铝石胶体,Eu3+在静电引力作用下在拟薄水铝石胶粒表面发生化学吸附.荧光光谱检测结果表明,Eu3+592 nm发射峰强度I592随AlOOH:Eu(NO3)3物质的量之比RBoe/Re的增大而降低.由发射峰强度I592计算出Eu3+在拟薄水铝石胶粒表面吸附率R随RBoe/Re增大而增大,当RBoe/Re=4时,吸附率可达53.0%.Eu3+在拟薄水铝石胶粒表面的吸附密度D也随RBoe/Re的增大呈上升趋势,且吸附曲线随RBoe/Re0分为初始阶段、平缓阶段和饱和阶段.