十六烷基胺稳定的CdSe纳米晶体的合成与表征

用CdO通过高温化学方法制备了具有高发光特性的CdSe胶体纳米晶.通过改变配体十六烷基胺在反应体系中的含量,合成了3种不同粒径的CdSe纳米晶.利用TEM、XRD和光谱等手段对合成出来的CdSe纳米晶的形貌结构和发光特性进行了表征.结果表明,随着十六烷基胺在反应体系中量的增多,CdSe纳米晶的粒径增大.通过调整十六烷基胺在反应体系中的量可以方便地控制纳米晶的尺寸.     

特殊形貌CdSe纳米晶的制备*

CdSe纳米晶是II-VI族半导体中研究最多的材料之一,由于其发射波长随纳米晶的尺寸而改变,从而可以覆盖从绿到红的宽光谱范围,因此CdSe纳米晶可以应用于生物标记和荧光显示等领域,各种制备CdSe纳米晶的方法也应运而生。因制备方法的不同,所得CdSe纳米晶的粒径、相结构及形貌也不同,进而影响CdSe纳米晶的性质。本文归纳了7种典型的制备一些特殊形貌的CdSe纳米晶的最新方法,并对各种方法的优缺点作了简单评价。最后,对这一领域未来的研究和发展方向作了展望。     

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.     

手性化合物组合修饰剂对CdSe纳米晶荧光性能的影响及标记大肠杆菌的研究

以手性化合物L-青霉胺、D-青霉胺、L-半胱氨酸为单一修饰剂或组合成双修饰剂,合成不同修饰剂修饰的CdSe纳米晶。对最佳合成条件如配料比,反应pH值,回流温度,回流时间进行了优化,对CdSe纳米晶发光强度及稳定性进行了系统研究。结果发现双修饰剂修饰的纳米晶比单修饰剂修饰的纳米晶荧光强度高,稳定性好;双修饰剂中第二修饰剂的空间位阻小的修饰效果好;不同手性修饰剂之间能以稳定方式结合的修饰效果好。研究了CdSe纳米晶对生物大分子的识别,仅发现核酸对CdSe纳米晶有明显的作用,用CdSe纳米晶作为荧光探针对大肠杆菌进行标记。     

手性双修饰剂修饰的CdSe纳米晶的合成及选择性识别Hg(II)的研究

以手性化合物D-青霉胺和L-半胱氨酸为双修饰剂在水相中合成了CdSe纳米晶, 痕量Hg(II)对其荧光强度有明显猝灭作用,基于此建立了定量测定痕量Hg(II)的新方法.在Cd2+, HSe-, D-Pen和L-Cys摩尔比为1: 0.25: 2: 1.2, pH=7.5的条件下,合成的纳米晶具有更好的发光强度和稳定性.TEM显示CdSe纳米晶为球形颗粒,粒径约为50和80 nm.在磷酸盐缓冲溶液(pH 7.38)中,CdSe纳米晶最大荧光峰为516 nm,对Hg(II)有高选择性响应.纳米晶的相对荧光强度与Hg(II)的浓度呈良好线性关系, 检出限为40 pmol/L.本方法测定不同水样中Hg(II)的浓度,回收率为96.7%～102.5%.     

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.     

水溶性CdSe/CdS纳米晶合成条件的优化研究

以巯基乙醇为修饰剂,在水溶液中合成了稳定的CdSe/CdS纳米晶,应用单因素法和多目标单纯形法探索合成条件。通过透射电镜观察所合成的纳米晶的形貌和大小,用紫外-可见吸收光谱和荧光光谱对其光学特性进行了表征。并且以L-色氨酸荧光量子产率0.14为标准,测量了合成的CdSe/CdS纳米晶的荧光量子产率为0.37。     

不同形貌/晶型CdSe纳米材料的简易合成

以乙二胺(en)为溶剂,通过调控反应物中镉源与硒源的摩尔比得到了不同形貌与晶型的CdSe纳米材料,达到了同时调控形貌与晶型的目的.当反应物中镉源与硒源摩尔比为1:1时,得到的产物为en体系常见的六方相棒状CdSe纳米晶体;当反应物中镉源与硒源摩尔比为1:2时,得到的产物为立方相CdSe纳米颗粒.进一步研究结果表明,反应体系中Se2-离子生成的多少及速度是影响反应进程得到不同产物的关键.     

介观结构SiO2/CdO纳米复合物为前驱体原位水热合成半导体CdSe和CdS纳米晶

以高度有序的介观结构SiO₂/CdO纳米复合物为前驱体,在硒源或硫源存在的还原性条件下,利用原位水热反应,合成了介观结构SiO₂/CdSe及SiO₂/CdS纳米复合物,除去SiO₂后,得到半导体CdSe及CdS纳米晶.通过X射线衍射(XRD),高分辨率透射电镜(HRTEM),X射线能散射谱(EDX)及选区电子衍射(SAED)等手段对产物进行了组成和结构表征.结果表明,介观结构SiO₂主体材料在合成过程中起到了一定的形貌和尺寸限制作用,得到的CdSe和CdS均为直径在8 nm左右的类球形六方相纳米晶.     

不同形貌/晶型CdSe纳米材料的合成

以乙二胺(en)为溶剂, 通过调控反应物中镉源与硒源的摩尔比得到了不同形貌与晶型的CdSe纳米材料, 达到了同时调控形貌与晶型的目的. 当反应物中镉源与硒源摩尔比为1∶1时, 得到的产物为en体系常见的六方相棒状CdSe纳米晶体；当反应物中镉源与硒源摩尔比为1∶2时, 得到的产物为立方相CdSe纳米颗粒. 进一步研究结果表明, 反应体系中Se^2－离子生成的多少及速度是影响反应进程得到不同产物的关键.     

Synthesis and characterization of mondispersed CdSe nanocrystals at lower temperature

Nearly monodispersed CdSe quantum dots have been prepared by a soft solution approach using air-stable reagents at lower temperature. The temporal evolution of the absorption and room temperature photoluminescence spectra were used to follow the reaction process and to characterize the optical properties of as-prepared CdSe quantum dots. The results exhibited clear exciton peaks in absorption and bright band-edge luminescence. The structures of the CdSe nanocrystals were determined by X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). The influence of the temperature on the properties of the resultant CdSe nanocrystals was investigated. The distribution of properties within ensembles of CdSe nanocrystals was also studied. A drastic difference in the photoluminescence efficiencies of size-selected fractions was observed.     

Synthesis of mercaptoethylamine-coated CdSe/CdS nanocrystals and their use for DNA probe.

CdSe/CdS nanocrystals (NCs) have been synthesized in aqueous solution by using mercaptoethylamine as a stabilizer. The results of TEM, UV-Vis and FL spectra show that the product is of excellent crystal structure, uniform in radius, with extraordinary fluorescence characters. These CdSe/CdS NCs allow the ultrasensitive quantitative detection of DNA. Under the optimum conditions, linear relationships have been found between the relative fluorescence intensity and the DNA concentration in the ranges 0 - 10 and 10 - 100 microg mL(-1); the linear equations are DeltaF = 210 + 80.91 C and DeltaF = 946 + 10.57 C (C, microg mL(-1)), respectively. The detection limits are 0.251 and 1.920 microg mL(-1), correspondingly. The proposed method has been applied to the determination of DNA in pig liver. It is indicated that these NCs could become a newly kind of DNA probe. In addition, the mechanism of the binding reaction has also been explored. It is considered that the binding reaction is mainly due to static electricity forces.     

Preparation of CdSe/ZnSe Core-shell Nanocrystal in One-step Reaction

IntroductionSemiconductor nanocrystals show strong size-de-pendent properties when their size is similar to or smal-ler than the excition Bohr radius of the bulk materialsand quantum confinement occurs for the space-con-fined motion of the electrons and holes in the nano-re-gion of materials[1—5].Because of the excellent opticaland electronic properties,semiconductor nanocrystalsare currently being investigated as emitting materials forthin-film light-emitting devices(LED)[6,7],low-thresh-ol…     

功能性CdSe纳米晶的合成及自组装膜光致发光

以巯基丙酸(RSH)为稳定剂,采用湿化学法合成了功能性CdSe纳米晶,用XRD、TEM表征其粒度和形貌,用UV-Vis监测成核及成膜过程。结果表明：制得的CdSe近似呈球形,平均粒径为48 nm。利用静电自组装法层层组装成CdSe-PDDA复合膜,荧光测试表明：所得CdSe纳米晶自组装复合膜(CdSe-PDDA)的荧光强度随着组装层数的增加而呈线性增强,该复合膜在582 nm附近有黄绿色荧光发射。     

Synthesis and characterization of monodisperse CdSe quantum dots in different organic solvents

Nearly monodisperse CdSe quantum dots (QDs) have been prepared by a soft solution approach using air-stable reagents in different organic solvents. This scheme is a supplement to the conventional thermal decomposition of organometallic compounds at higher temperatures. CdSe nanocrystals of different sizes could be obtained by simply changing the solvent. This method is reproducible and simple and thus can be readily scaled up for industrial production. The reaction process was monitored by the temporal evolution of the UV-Vis absorption and room temperature photoluminensce spectra. The structures of the CdSe quantum dots were determined by X-ray powder diffraction (XRD) and transmission electron microscopy (TEM). The phase-transfer of oleic acid-stabilized CdSe nanocrystals into PBS buffer solutions was also studied for their potentials in biological applications. __________ Translated from Journal of Shanghai Jiaotong University, 2005, 39(1) (in Chinese)     

Preparation and characterization of polyvinyl alcohol-capped CdSe nanoparticles at room temperature

Polyvinyl alcohol (PVA)-capped CdSe nanoparticles were successfully prepared by a one-step solution growth technique at room temperature and ambient pressure. X-ray diffraction, transmission electron microscopy, infrared spectra, and X-ray photoelectron spectra were used to characterize the final product. The as-prepared CdSe nanocrystals were well dispersed and uniform in shape and the diameter of the particles was confined within 8 nm. Ultraviolet-visible absorption spectra were used to study the confined growth process of PVA-capped CdSe nanoparticles. Photoluminescence measurement showed the near band-edge luminescence of the final product.     

One‐Pot Synthesis of CdSe Quantum Dots in Aqueous Solution for Biological Labeling

The one‐pot synthesis of water‐soluble and biologically compatible yellow CdSe quantum dots (QDs) featuring the use of glutathione (GSH) as the capping and reducing agent was achieved under aqueous conditions at 150 °C. The synthesized yellow CdSe QDs with quantum yield (QY) up to 20% exhibit zinc blende cubic structure particles with an average diameter of 4‐5 nm. It was found that both molar ratio of Se/Cd and reaction time had a significant effect on size distribution of GSH‐CdSe QDs. Meanwhile, the interaction of QDs bioconjugated to bovine hemoglobin (BHb) was studied by absorption and fluorescence(FL) spectra. With addition of BHb, the FL intensity of CdSe QDs largely quenched due to the static mechanism. The linear range is 5.0 × 10^?8 mol/L to 3.0 × 10^?6 mol/L, and the correlation coefficient is 0.9991, suggesting that could be used as a probe to label biological molecules and bacterial cells.     

Preparation and application of L-cysteine-modified CdSe/CdS core/shell nanocrystals as a novel fluorescence probe for detection of nucleic acid

The water-soluble L-cysteine-modified CdSe/CdS core/shell nanocrystals (expressed as CdSe/CdS/Cys nanocrystals) have been synthesized in aqueous by using L-cysteine as stabilizer. The size, shape, component and spectral property of CdSe/CdS/Cys nanocrystals were characterized by high-resolution transmission electron microscope (HRTEM), energy dispersive X-ray fluorescence (EDX), infrared spectrum (IR) and photoluminescence (PL). The results showed that the spherical CdSe/CdS/Cys nanocrystals with an average diameter of 2.3 nm have favorable fluorescent property, theirs photostability and fluorescence intensity are enhanced greatly after overcoating with CdS. The cysteine modified on the surface of core/shell CdSe/CdS nanocrystals renders the nanocrystals water-soluble and biocompatible. Based on the fluorescence quenching of the nanocrystals in the presence of calf thymus deoxyribonucleic acid (ct-DNA), a fluorescence quenching method has been developed for the determination of ct-DNA by using the nanocrystals as a novel fluorescence probe. The pH value of the system was selected at pH 7.4, with excitation and emission wavelength at 380 and 522 nm, respectively. Under the optimal conditions, the fluorescence quenching intensity of the system is linear with the concentration of ct-DNA in the range of 0.1-3.5 microg/mL (r=0.9987). The detection limit is 0.06 microg/mL. And two synthetic samples were analyzed satisfactorily.     

Synthesis and Characterization of CdSe Nanocrystals Capped by CdS

CdSe semiconductor nanocrystals capped by CdS were synthesized in the aqueous solution with 2-mercaptoethanol as the stabilizer. The CdS capping with a higher band-gap than that of the core crystallite has successfully eliminated the surface traps. Optical absorption and fluorescence emission spectra were used to probe the effect of CdS passivation on the electronic structure of the nanocrystals. The composite CdSe/CdS nanocrystals exhibit strong, narrow(FWHM≤40 nm) and stable band-edge photoluminescence. X-ray powder diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy were used to analyze the composite nanocrystals and determine their average size, size distribution, shape, internal structure and elemental composition.