Studying the interaction between CdTe quantum dots and Nile blue by absorption,fluorescence and resonance Rayleigh scattering spectra

Thioglycolic acid (TGA) capped CdTe quantum dots (QDs) with the diameter of 2–3 nm were synthesized. The interaction between CdTe QDs and Nile blue (NB) was investigated by ultraviolet–visible (UV–vis) absorption, resonance Rayleigh scattering (RRS) and fluorescence spectroscopy. UV–vis absorption spectrum of CdTe QDs and NB obviously changed, showing that CdTe QDs could associate with NB to form a new complex. At pH 6.8, NB effectively quenched the fluorescence of CdTe QDs. It was proved that the fluorescence quenching of CdTe QDs by NB was mainly result of the formation of CdTe QDs–NB complex, electrostatic attraction and hydrophobic forces played a major role in stabilizing the complex. The binding molar ratio of CdTe QDs and NB was 5:1 by a mole-ratio method. The interaction between CdTe QDs and NB lead to the remarkable enhancement of RRS and the enchantments were in proportional to the concentration of NB in a certain range. The mechanism of the interaction between CdTe QDs and NB, reasons for the enhancement of RRS intensity were also discussed. The obtained results suggested the more satisfactory mechanism for the interaction between CdTe QDs and NB.     

配体对CdTe量子点与BSA的选择性相互作用的影响

以巯基乙酸(TGA)、巯基丙酸(MPA)、巯基甘油(TG)、L-半胱氨酸(L-cys)和谷胱甘肽(GSH)等5种巯基分子为稳定剂, 水相合成了5种CdTe量子点. 以牛血清白蛋白(BSA)作为靶分子, 通过吸收光谱、荧光光谱和时间分辨荧光动力学等手段研究了各种配体分子稳定的CdTe量子点与BSA的直接相互作用. 结果表明, 5种量子点均能有效猝灭BSA的荧光, 其猝灭程度按配体次序为GSH>L-cys>TGA>TG>MPA; 而BSA对不同配体稳定的CdTe量子点的荧光光谱的影响则具有明显的选择性. BSA对TGA-CdTe和MPA-CdTe量子点的荧光先敏化增强而后猝灭下降; L-cys分子由于同时具有氨基和羧基而与BSA的相互作用较强, 因此BSA能显著猝灭L-cys-CdTe量子点的荧光; 而BSA对TG-CdTe量子点的荧光猝灭程度较小; GSH分子的空间效应使GSH-CdTe量子点的荧光被BSA猝灭的程度最小. 吸收光谱和时间分辨荧光动力学研究表明, 5种量子点与BSA之间的相互作用均为静态过程. 探讨了量子点的配体分子结构与蛋白质的相互作用机理.     

Spectroscopic studies on the interaction between CdTe nanoparticles and lysozyme

Nanoparticles of cadmium telluride (CdTe) coated with thioglycolic acid (TGA) were prepared in the water phase. The interaction between CdTe nanoparticles (NPs) and lysozyme (Lyz) was investigated by fluorescence and circular dichroism (CD) spectroscopy at pH 7.40. It was proved that the fluorescence quenching of Lyz by CdTe NPs was mainly a result of the formation of CdTe-Lyz complex. By the fluorescence quenching results, the Stern-Volmer quenching constant (K(SV)), binding constant (Ka) and binding sites (n) were calculated. The binding distance (r) between Lyz (the donor) and CdTe NPs (the acceptor) was obtained according to fluorescence resonance energy transfer (FRET). Gradual addition of CdTe NPs to the solution of Lyz led to a marked increase in fluorescence polarization (P) of Lyz, which indicated that CdTe NPs were located in a restricted environment of Lyz. The effect of CdTe NPs on the conformation of Lyz has been analyzed by means of synchronous fluorescence spectra and CD spectra, which provided the evidence that the secondary structure of Lyz has been changed by the interaction of CdTe NPs with Lyz.     

量子点-卟啉纳米复合体系在肿瘤细胞成像中的应用

本文合成了高荧光量子产率、单分散性好的水溶性CdTe量子点(quantum dots,QDs),并与α,β,γ,δ-四(1-甲基吡啶嗡-4-基)卟吩对甲苯磺酸盐(TMPyP)组装成QDs-TMPyP纳米复合物,研究了该复合物检测DNA的机理以及肿瘤细胞成像。结果显示,QDs-TMPyP纳米复合物通过光致电子转移机制检测DNA,当CdTe QDs和CdTe QDs-TMPyP浓度低于1.0μmol/L时,HeLa肿瘤细胞存活率达92%以上,表现出低的细胞毒性。0.2μmol/L CdTe QDs-TMPyP作用于肿瘤细胞时,细胞生长状态良好,对细胞内能谱分析发现细胞内含有Cd和Te原子。CdTe QDs-TMPyP复合物比CdTe QDs更易被HeLa细胞摄取,利用量子点荧光成功实现了细胞核内成像,为宫颈癌细胞药物输送和细胞成像的深入研究打下基础。     

CdTe纳米荧光探针的合成及其与DNA的相互作用

以巯基丙酸(RSH)为稳定剂,采用水相法合成了功能性CdTe纳米晶,并通过X射线衍射(XRD)和透射电镜(TEM)对其粒度和形貌进行表征。建立了一种以水溶性CdTe量子点作为荧光探针测定DNA的方法,当DNA浓度为0.2~40μmol.dm-3时,荧光强度与DNA浓度呈良好的线性关系,检测限为80nmol.dm-3,11次重复测定含有5.6μmol.dm-3的小牛胸ctDNA得到的相对标准偏差为3.4%。考察了CdTe量子点浓度、pH值、温度及作用时间等因素对DNA荧光强度的影响。研究发现CdTe纳米粒子与DNA之间存在强烈的相互作用,量子点的荧光猝灭与DNA浓度呈线性关系;作用机理研究表明,CdTe纳米粒子与DNA之间存在静电相互作用,且DNA对CdTe纳米粒子的猝灭为动态猝灭过程。     

Transferring CdTe Nanoparticles from Liquid Phase to Polyvinylpyrrolidone Nanofibers by Electrospinning and Detecting Its Photoluminesccnce Property

The major aim of this work was to synthesize thio-stabilized CdTe nanoparticles（NPs） in an aqueous solution, which was then enwrapped with cetyltrimethylammonium bromide（CTAB）, and finally transferred to the polyvinylpyrrolidone（PVP） matrix by electrospinning. The PVP nanofibers containing CdTe NPs were characterized by scanning electron microscopy（SEM） and transmission electron microscopy（TEM）, to observe the morphology of the nanofibers and the distribution of CdTe NPs. The selective area electronic diffraction（SAED） pattern verified that CdTe NPs were cubic lattice. The photoluminescence（PL） spectrum indicated that CdTe NPs existed in an optical style in PVP nanofibers. Moreover, X-ray photoelectron spectra（XPS） revealed that thiol-stabilized CdTe NPs were enwrapped by CTAB, and PVP acted as a dispersant in the process of electrospinning.     

Transferring CdTe Nanoparticles from Liquid Phase to Polyvinylpyrrolidone Nanofibers by Electrospinning and Detecting Its Photoluminescence Property

The major aim of this work was to synthesize thio-stabilized CdTe nanoparticles(NPs) in an aqueous solution,which was then enwrapped with cetyltrimethylammonium bromide(CTAB),and finally transferred to the polyvinylpyrrolidone(PVP) matrix by electrospinning,The PVP nanofibers containing CdTe NPs were characterized by scanning electron microscopy(SEM) and transmission electron microscopy(TEM),to observe the morphology of the nanofibers and the distribution of CdTe NPs,The selective area electronic diffraction(SAED) pattern verified that CdTe NPs were cubic lattice,The photoluminescence(PL) spectrum indicated that CdTe NPs existed in an optical style in PVP nanofibers,Moreover,X-ray photoelectron spectra(XPS) revealed that thiol-stabilized CdTe NPs were enwrapped by CTAB,and PVP acted as a dispersant in the process of electrospinning.     

Synthesis of CdTe/SiO_2 Composites and Their Fluorescence Properties

Thioglycolic acid(TGA)-stabilized CdTe nanocrystals(NCs) were prepared with sodium tellurite as tellurium source,which avoids the cumbersome processes associated with H2Te or NaHTe sources.Fluorescent CdTe/SiO2 composites were synthesized by a sol-gel method without the exchange of surface ligands.The phase structure of CdTe NCs was investigated by X-ray diffractometry.For comparison,some characterizations were done for both the CdTe NCs and the composites.CdTe NCs and CdTe/SiO2 composites were characterize...     

Facile synthesis of nanocrystal encoded fluorescent silica microspheres

Monodisperse CdTe composite microspheres with a spherical shape were prepared using organosilane chemicals in aqueous solution. CdTe nanocrystals (NCs) were loaded into the matrix of silica microspheres during the formation of composite microspheres. Detailed characterization of the CdTe composite microspheres by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and spectrofluorimeter was performed to elucidate the morphology and fluorescence of the composite microspheres. In contrast to CdTe NCs in aqueous solution, CdTe NCs in the composite microspheres revealed high stability and fluorescence due to the confined effects of silica matrix. In addition, multicolored CdTe QDs were encoded into the microspheres at precise ratios.     

水相中CdTe纳米晶的制备及其光学性质

用不同稳定剂(巯基乙酸(TGA)、巯基丙酸(MPA)、L-半胱氨酸(L-Cys)、3-巯基-1,2-丙二醇(TG))在水相中制备了CdTe纳米晶, 并用透射电子显微镜(TEM)、X射线光电子能谱(XPS)和X射线粉末衍射(XRD)等技术对其进行了表征. 研究了不同水相合成条件对CdTe纳米晶光学性质的影响, 结果表明, n(Cd):n(Te)、溶液pH值、回流时间以及稳定剂的性质, 对纳米晶的光学性质具有显著影响. 制得的CdTe纳米晶发射峰窄且对称(半高全宽达38 nm), 用不同稳定剂制备的纳米晶发光量子效率有所不同, 用不同的激发波长对纳米晶进行激发时, 发射峰并未表现出明显的移动.     

Study the damage of DNA molecules induced by three kinds of aqueous nanoparticles

In this paper, the interaction of DNA molecules with aqueous CdTe quantum dots (CdTe QDs), CdTe/SiO₂ composite nanoparticles (CdTe/SiO₂ NPs), and Mn-doped ZnSe quantum dots (Mn:ZnSe d-dots) was studied with ethidium bromide as a probe. The purpose of this work was to study the damage of DNA molecules induced by these three kinds of water-soluble nanoparticles. It was found that ionic strength, pH value and UV irradiation influenced the PL emission properties of CdTe QDs, CdTe/SiO₂ NPs and Mn:ZnSe d-dots, and also influenced the interaction of DNA molecules with them. Among the three kinds of nanoparticles, DNA molecules were most easily damaged by CdTe QDs whether in the dark or under UV irradiation. The CdTe/SiO₂ NPs led to much less DNA damage when compared with CdTe QDs, as a silica overcoating layer could isolate the QDs from the external environment. Mn:ZnSe d-dots as a new class of non-cadmium doped QDs demonstrated almost no damage for DNA molecules, which have great potentials as fluorescent labels in the applications of biomedical assays, imaging of cells and tissues, even in vivo investigations.     

基于L-半胱氨酸/CdTe量子点修饰电极的电化学传感器的制备及其对Pb~(2+)的检测

成功制备了由L-半胱氨酸和CdTe量子点作为修饰材料的电化学传感器并用于水体中Pb~(2+)的检测。巯基丙酸修饰的CdTe量子点通过水相合成,表面含有大量羧基,与L-半胱氨酸表面的氨基形成酰胺键,修饰于金电极表面。通过荧光分光光度计、透射电子显微镜、红外光谱、X射线衍射对L-Cys/CdTe QDs复合材料进行表征。采用循环伏安法(CV)研究了L-Cys/CdTe QDs修饰成分在金电极上的电化学性能及CdTe量子点的最佳自组装时间。采用差分脉冲溶出伏安法(DPSV)研究了铅离子在修饰电极上的电化学行为。在优化实验条件下,Pb~(2+)浓度在1.0×10~(-6)~1.0×10~(-2) mol/L范围内与其峰电流呈良好的线性关系,相关系数(r2)为0.993 8,检出限(3σ,n=5)为4.0×10~(-7) mol/L。该传感器具有良好的重现性和稳定性,有望用于实际水样中铅离子的检测。     

聚合物主体中纳米CdTe的光致发光与电致发光性质

利用紫外和荧光光谱技术研究了共轭聚合物PPE4+分别在溶液和薄膜中与纳晶CdTe间的能量传递现象。通过静电层层组装技术制备了混杂有纳晶CdTe的PPE4+薄膜发光二极管,并测试了其电致发光性质。结果表明在溶液和薄膜中共轭聚合物PPE4+与纳晶CdTe间均能发生有效的能量转移,而共轭聚合物PPE4+在能量传递过程中起到分子天线的作用。     

水相合成CdX (X＝Te, Te/CdS, Te/ZnS)红色量子点及毒性效应

分别以巯基乙酸(Mercaptoacetic Acid, MA)、还原型谷胱甘肽(Glutathione, GSH)为稳定剂在水相中直接合成了巯基乙酸CdTe (CdTe-MA)、红色巯基乙酸CdTe/CdS (CdTe/CdS-MA)、巯基乙酸CdTe/ZnS (CdTe/ZnS-MA)及谷胱甘肽CdTe (CdTe-GSH)量子点. 其中, CdTe-GSH量子点的量子产率可达47.3%. 体外溶血实验证实CdTe/ZnS-MA和CdTe-GSH量子点的溶血率较CdTe-MA和CdTe/CdS-MA低, 浓度为0.05 mmol/L的量子点溶血率＜5%, 达到了生物医用材料的要求. 活体实验证实: 通过尾静脉方式把量子点注入小鼠体内后, 荧光显微镜观察发现高剂量的量子点(0.4 mmol/10 g)在体内主要在心、肝、脾、肾组织中分布较多, 且引起不同程度的组织病变.     

Highly efficient size separation of CdTe quantum dots by capillary gel electrophoresis using polymer solution as sieving medium

In this paper, we present a new method for highly efficient size separation of water-soluble CdTe quantum dots (QDs) based on CGE using polymer solution as sieving medium. CdTe QDs were synthesized in aqueous phase by a chemical route with mercaptopropionic acid as a ligand. In the alkaline solution, CdTe QDs possess negative charges and migrate to the anode in the electric field. In linear polyacrylamide sieving medium, the migration time of CdTe QDs was increased with the size of CdTe QDs. The effects of some factors, such as types, concentrations, and pH of sieving media, on the separation of CdTe QDs were investigated systematically. Highly efficient separation of CdTe QDs was obtained in linear polyacrylamide sieving medium, and collection of fractions was automatically accomplished by CGE technique. Our preliminary results show that CGE technique is an efficient tool for characterization and size-dependent separation of water-soluble nanoparticles. In addition, the fraction collection in CGE may be useful in certain special applications such as fabrication of nanodevices in the future.     

利用水相合成的CdTe纳米晶构建超晶格结构研究--纳米晶聚集体的调控

用巯基丙酸作稳定剂,在水溶液中制备了CdTe纳米晶.通过加入Cd2+、聚丙烯酸(PAA)以及长期放置分别得到了CdTe纳米晶的聚集体,改变Cd2+浓度或PAA加入量可以调控聚集体的尺寸.过量的Cd2+加速了聚集体的形成,通过与纳米晶表面羧酸根的静电相互作用,Cd2+成为连接不同CdTe纳米晶的“桥梁”.PAA链上大量的羧基与CdTe纳米晶有较强的配位相互作用,可以诱导纳米晶聚集.新制CdTe纳米晶在长期放置时,表面的羧基与Cd2+的相互作用导致纳米晶逐渐聚集.在聚集过程中纳米晶表面结构得到改善,并引起荧光增强.这些结果表明通过控制各种聚集条件,可以得到不同尺寸的聚集体.     

Electrostatic and covalent interactions in CdTe nanocrystalline assemblies

This paper focuses on the interactions between cysteamine-stabilized CdTe nanocrystals [CdTe(CA) NCs] and thioglycolic-acid-stabilized CdTe nanocrystals [CdTe(TGA) NCs]. These interactions were examined by the absorption, continuous, and time-resolved photoluminescence (PL) spectra of the electrostatically mixed and the covalently linked NCs assemblies comprised of the oppositely surface charged CdTe(CA) and CdTe(TGA) NCs and by a comparison with those of the corresponding pristine NCs. The CdTe(CA)-CdTe(TGA) coupling is dictated by the surfactant spacer, ranging between 0.93 and 1.14 nm and by electrostatic and covalent interactions, enabling a F?rster resonance energy transfer (FRET) process among the NCs. The results revealed an excellent spectral overlap between the emission of the CdTe(TGA) NCs and the absorption of the CdTe(CA) NCs as well as a PL spectral red shift on the formation of electrostatic and covalent interactions. Furthermore, the measurements showed a lifetime ranging between 1.2 and 3 ns for the electrostatically mixed and the covalently linked assemblies, shorter than those of the pristine CdTe(CA) NCs and CdTe(TGA) NCs, both of which measured as approximately 5.5 ns. When CdTe(TGA) NCs performed as the most efficient donors, FRET rates of 10(10)-10(11) s(-1) were calculated for the electrostatically mixed NCs or covalently linked NCs.     

Amphiphilic ABC triblock copolymer-assisted synthesis of core/shell structured CdTe nanowires

A new type of amphiphilic ABC triblock copolymer, poly(acrylic acid)(33)-poly(styrene)(47)-poly(ethylene oxide)(113) (PAA(33)-PS(47)-PEO(113)), was designed to assist the synthesis of core/shell structured CdTe nanowires via a one-step synthetic route. The PAA block was adopted to capture cadmium ions as the precursor of CdTe. Due to the bivalent coordination of Cd(2+), the copolymer in dioxane/H(2)O formed micelles with Cd(2+)-polychelate cores. Then CdTe nanocrystals were obtained within the micelles after introduction of NaHTe into the micelle solution. Transmission electron microscopy experiments revealed that the CdTe nanocrystals obtained simultaneously formed "pearl-necklace" aggregates in solution possibly driven by dipole interactions between neighboring particles, and then single crystalline CdTe nanowires upon reflux. Accompanying this morphology change, a phase transition from cubic zinc blende to wurtzite structure was observed by selected-area electron diffraction. The aggregation of the PS block in dioxane with a certain amount of H(2)O enabled the PS blocks to form a densely packed shell on the CdTe nanowires whose typical size is 700-800 nm in length and 15-20 nm in width. The third block of PEO was employed to render the finally formed CdTe nanowires dispersibility.     

Optical absorption and valence band photoemission from uncapped CdTe nanocrystals

CdTe nanocrystals have been successfully fabricated by a mechanical alloying process. X-ray diffraction (XRD) patterns demonstrate that a single-phase CdTe compound with a zinc blende structure has been formed after ball milling elemental Cd and Te mixture powders for 27 h. The large broadening effect for the width of the {111} diffraction peak of uncapped CdTe nanocrystals on smaller size was observed in slowly scanned XRD patterns. The X-ray photoelectron spectrum was used to study the surface of the uncapped CdTe nanocrystals within both core level and valence band regions. The presence of tellurium oxide film on the surface of the uncapped CdTe nanocrystals has been detected in the X-ray photoelectron spectrum of the Te 3d core level, which was comparable to the observed amorphous oxide thin layer on the surface of uncapped CdTe nanocrystals in a high resolution transmission electron microscopy (HRTEM) image. The energy of the valence band maximum for uncapped CdTe powders blue shifts to the higher energy side with smaller particle sizes. In UV-visible optical absorption spectra of the suspension solution containing uncapped CdTe nanocrystals, the absorption peaks were locating within the ultraviolet region, which shifted toward the higher energy side with prolonged ball milling time. Both blue shifts of valence band maximum energy and absorption peaks with decreasing particle size provide a unique pathway to reveal the quantum confinement effect of uncapped CdTe nanocrystals.     

基于水溶性CdTe量子点-绿原酸-血管紧张素Ⅰ 相互作用的荧光可逆调控

在水相中合成了巯基丙酸(MPA)包覆的CdTe量子点(QDs), 采用透射电子显微镜和原子力显微镜对其进行表征. 利用荧光光谱、紫外-可见吸收光谱和红外光谱研究了CdTe QDs与绿原酸(CHA)的相互作用. 结果表明, CHA可显著猝灭CdTe QDs的荧光, 在一定的浓度范围内, 荧光猝灭值与CHA的浓度呈现一定的线性关系. 推断其主要猝灭机理为动态猝灭, 并实现了荧光光谱法测定CHA. 向CdTe QDs-CHA体系中加入血管紧张素Ⅰ(AngⅠ)后, CdTe QDs荧光在一定浓度范围内逐渐恢复, 从而实现了CdTe QDs的荧光可逆调控. CdTe QDs荧光的猝灭与恢复过程对于荧光传感的设计以及荧光可逆调控机理的研究具有指导意义.