圆偏振光诱导CdTe量子点再生长及其对光致发光的影响

实验研究了以3-巯基丙酸为配体合成的水溶性CdTe量子点经过非偏振光与圆偏振光照射处理后, 量子点的再生长变化规律。采用光致发光谱、紫外-可见吸收光谱、透射电子显微镜与X射线衍射等表征手段分析表明: 非偏振光会促进CdTe量子点的光氧化, 导致量子点尺寸缩小, 荧光发光峰位蓝移, 且发光效率降低; 而圆偏振光增强了配体的光氧化, 在量子点表面形成CdS层, 导致量子点尺寸进一步增大, 荧光发光峰红移, 且发光效率提升。进一步讨论了CdTe量子点与配体之间的键合作用, 相关光化学反应机制及其对量子点光致发光性质的影响。     

水溶性Cu∶CdTe/CdS核壳量子点的合成、表征及细胞毒性检测

采用水相法合成了Cu掺杂CdTe量子点,并用CdS壳层进行包覆,得到了Cu∶CdTe/CdS核壳结构量子点。采用荧光发射光谱(FL)、紫外可见吸收光谱(UV-Vis)、透射电镜(TEM)以及能谱仪(EDS)等手段对CdTe量子点和Cu∶CdTe/CdS核壳量子点进行了表征。研究了不同Cu掺杂浓度、CdS壳层生长时间以及Cd/硫脲物质的量比对Cu∶CdTe掺杂量子点光学性能的影响,并采用人成骨肉瘤细胞(MG-63细胞)对样品做了细胞毒性分析。研究结果表明:通过掺杂和包壳的步骤,合成的Cu∶CdTe/CdS核壳量子点在CdTe量子点的基础上实现了荧光发射红移,荧光强度提高,以及细胞毒性降低。     

Interaction of porphyrins with CdTe quantum dots

Porphyrins may be used as photosensitizers for photodynamic therapy, photocatalysts for organic pollutant dissociation, agents for medical imaging and diagnostics, applications in luminescence and electronics. The detection of porphyrins is significantly important and here the interaction of protoporphyrin-IX (PPIX) with CdTe quantum dots was studied. It was observed that the luminescence of CdTe quantum dots was quenched dramatically in the presence of PPIX. When CdTe quantum dots were embedded into silica layers, almost no quenching by PPIX was observed. This indicates that PPIX may interact and alter CdTe quantum dots and thus quench their luminescence. The oxidation of the stabilizers such as thioglycolic acid (TGA) as well as the nanoparticles by the singlet oxygen generated from PPIX is most likely responsible for the luminescence quenching. The quenching of quantum dot luminescence by porphyrins may provide a new method for photosensitizer detection.     

Fe3O4/CdTe磁性荧光纳米复合物的逐步杂凝聚法合成及其表征

采用逐步杂凝聚法合成了Fe3O4/CdTe磁性荧光纳米复合物.以化学共沉淀法制备Fe3O4纳米颗粒,经油酸修饰后分散在表面活性剂中形成磁流体.CdTe量子点以巯基乙酸为稳定剂制得.最后以聚乙烯亚胺(PEI)为联接剂,成功制备了Fe3 O4 /CdTe磁性荧光双功能纳米复合物颗粒.该复合物颗粒平均尺寸为(30±5)nm,荧光产率为0.186,饱和磁化强度为15.745emu/g,该纳米粒子既具有优异的荧光特性,也具有较强的超顺磁性.     

Intracellular delivery of quantum dots tagged antisense oligodeoxynucleotides by functionalized multiwalled carbon nanotubes

With the goal of identifying an improved delivery scheme for intracellular tracking and anticancer therapy, we explored a novel double functionalization of a carbon nanotube delivery system containing antisense oligodeoxynucleotides (ASODNs) as a therapeutic gene and CdTe quantum dots as fluorescent labeling probes via electrostatically layer-by-layer assembling. This is the first time that we used mercaptoacetic acid-capped CdTe quantum dots as fluorescent labeling probes for clearly tracking the intracellular transport and evaluating delivery efficiency of ASODNs by functionalized multiwalled carbon nanotubes (MWNTs).     

Evolution of luminescence properties of CdTe quantum dots in liquid/solid environment

We studied the luminescence behavior of different sized CdTe quantum dots (QDs) dispersed in liquid solution, close-packed films and layer-by-layer assembled films respectively. The changes of emission color from CdTe QDs in water droplets during the evaporation of solvent have been observed. The quenching of the emission from small dots accompanied by the enhancement of the emission from large dots indicate that Forster resonance energy transfer processes occur from donors (small dots) to acceptors (large dot) for CdTe QDs system. Excitation (PLE) spectra confirm that the changes of the luminescence were attributed to the resonance energy transfer between small and larger dots in a mixed QD system.     

Fabrication of dumbbell-like CdTe/Au nanohybrids

Dumbbell-like CdTe/Au nanohybrids were synthesized by assembly of CdTe quantum dots with the assistance of AuCl₄⁻ in aqueous solution. The products were characterized by TEM and SEM techniques. The images reveal that dumbbell-like nanostructures with uniform size were well formed. The dumbbell-like nanostructures were further characterized by HRTEM and EDX spectrum. The results indicate that the as-prepared dumbbell-like nanostructures were composed of CdTe quantum dots and Au nanoparticles. The effect of HAuCl₄ concentration on the morphology of the products was also investigated, which shows that the morphology of the products evolved from sheaf-like nanostructures to rod-like nanostructures and finally dumbbell-like nanostructures as the HAuCl₄ concentration increased. Based on the above results, a possible mechanism for the formation of dumbbell-like CdTe/Au nanohybrids is proposed.     

Heterostructures with CdTe/ZnTe quantum dots for single photon emitters grown by molecular beam epitaxy

We report on the molecular beam epitaxy (MBE) of heterostructures with CdTe/ZnTe quantum dots (QDs) with relatively low surface density, which could be used as single-photon emitters. The QDs were formed on the surface of a 3.1- to 4.5-monolayer-thick two-dimensional strained CdTe layer by depositing amorphous Te layer and its fast thermal desorption. Subsequent thermal annealing of the surface with QDs in the absence of external Te flux led to strong broadening and short-wavelength shift of the QD photoluminescence (PL) peak. Measurement of the micro-PL spectra of individual CdTe/ZnTe quantum dots in fabricated mesastructures with a diameter of 200—1000 nm allowed estimation of the QD surface density as ~10¹⁰ cm^–2.     

Monolithic ZnTe-based pillar microcavities containing CdTe quantum dots

Micropillars of different diameters have been prepared by focused ion beam milling out of a planar ZnTe-based cavity. The monolithic epitaxial structure, deposited on a GaAs substrate, contains CdTe quantum dots embedded in a ZnTe λ-cavity delimited by two distributed Bragg reflectors (DBRs). The high refractive index material of the DBR structure is ZnTe, while for the low index material a short-period triple MgTe/ZnTe/MgSe superlattice is used. The CdTe quantum dots are formed by a novel Zn-induced formation process and are investigated by scanning transmission electron microscopy. Micro-photoluminescence measurements show discrete optical modes for the pillars, in good agreement with calculations based on a vectorial transfer matrix method. The measured quality factor reaches a value of 3100.     

稳定剂对水相制备CdTe量子点的荧光性能和细胞毒性影响研究

用巯基乙酸(TGA)、半胱氨酸(L-Cys)和谷胱甘肽(GSH)这三种巯基稳定剂在水相中制备了CdTe量子点(QDs).红外光谱(FTIR)分析结果表明,三种稳定剂都成功地利用Cd2+与巯基之间的配位与QDs相结合并起到保护及稳定的作用.利用荧光光谱对不同QDs的荧光性能进行了研究,结果表明当采用GSH作为稳定剂时,QDs的生长速率较快,且最大发射波长能够达到约680nm;L-Cys-CdTe的生长速率次之,也能生成具有较大发射波长的QDs;TGA-CdTe的生长速率最慢,且最大发射波长只能达到约620nm,但是其荧光强度较高,适于制备对荧光强度要求较高的QDs.通过MTT(噻唑蓝)比色法对细胞存活率进行测定,同时利用显微镜对细胞形貌进行观察,结果表明各量子点都具有一定的细胞毒性,但TGA-QDs对细胞的伤害作用更大,以20μg/mL的浓度对细胞培养24h后,细胞存活率只有52.6%.     

Electronic energy transfer between long-range resonance states of 3-mercaptopropionic acid capped CdTe quantum dots in aqueous media

We demonstrate electronic energy transfer between resonance states of 2 and 2.8?nm CdTe quantum dots in aqueous media using steady-state photoluminescence spectroscopy without using any external linker molecule. With increasing concentration of larger dots, there is subsequent quenching of luminescence in smaller dots accompanied by the enhancement of luminescence in larger dots. Our experimental evidence suggests that there is long-range resonance energy transfer among electronic excitations, specifically from the electronically confined states of the smaller dots to the higher excited states of the larger dots.     

A one-pot aqueous synthesis of high-luminescent thiol-capped CdTe and its bioapplication

Our study described a synthesis of thiol-capped high-luminescent (quantum yield as high as 80%) CdTe quantum dots (QDs) with a facile method in aqueous phase. The fluorescence of the as-prepared CdTe QDs could be tuned from 500 nm to 650 nm. More importantly, after beta-actin conjugation, the CdTe QDs were successfully conjugated with live cells to observe their configurations, demonstrating their potentially broad application as biolabels. The crystal structure, morphology and optical property of the products were investigated by X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM) and fluorescence spectrophotometer.     

Preparation and characterization of highly luminescent water-soluble CdTe quantum dots as optical temperature probes

Highly luminescent water-soluble CdTe quantum dots were synthesized with an electrogenerated precursor. The size, morphology, optical properties as well as fluorescence stability were characterized by transmission electron microscope, high-resolution transmission electron microscope, powder X-ray diffraction, UV-vis-NIR spectrophotometer, and fluorescence spectrophotometer. The results show that the CdTe QDs with diameter ranging from 2.0 nm to 3.5 nm have good crystallizability, high quantum yield and favorable fluorescence stability. Moreover, the CdTe QDs demonstrate temperature-dependent reversible PL intensity variations at moderate temperatures above room temperature. It is also found that the QDs with different sizes possess different sensitivity to the temperature. All the studies indicate that the CdTe QDs are expected to be promising candidates for a variety of biological and biomedical applications.     

Ultrafast synthesis of CdTe/ZnSe semiconductor QDs by microwave method and investigation of structural,optical, and photocatalytic properties of CdTe/ZnSe QDs

Journal of Materials Science: Materials in Electronics - CdTe/ZnSe semiconductor quantum dots were synthesized by the ultrafast microwave method in an aqueous solution. X-ray diffraction results...     

Hyperbranched CdTe nanostructures via a self-assembly route: optical properties

In this work, we report a luminescent nanobundle structure formed by a hierarchical self-assembly process of thioglycolic acid (TGA)-capped CdTe quantum dots (QDs). The luminescence intensity of CdTe nanostructures is high enough to get a clear one-photon excitation confocal image. High contrast two-photon excitation confocal images suggest that the nonlinear properties of pristine QDs are well inherited by the formed CdTe nanostructures. The controllability of the structures and inheritance of the optical properties of the building units make the self-assembled nanostructures new generation materials.     

CdTe量子点的微波合成及其在双光子显微成像中的应用

采用微波辐射加热的方法,以亚碲酸钠(Na2TeO3)作碲源,以谷胱甘肽(GSH)作稳定剂,在水相中合成出高质量的CdTe量子点。所合成量子点的发射波长从515～630nm可调,荧光量子产率(PLQYs)最高达95%。利用X射线粉末衍射(XRD)、高分辨透射电镜(HRTEM)、紫外-可见吸收光谱(UV-Vis)和荧光发射光谱(PL)等技术表征产物的物相结构和光学性质。用双光子激发荧光法研究CdTe量子点的双光子吸收性质。用双光子激发荧光成像技术,以发红光的CdTe量子点作为双光子荧光探针成功标记了人肺腺癌细胞(A549)。     

Photoluminescence waveguiding in CdSe and CdTe QDs-PMMA nanocomposite films

In this paper, active planar waveguides based on the incorporation of CdSe and CdTe nanocrystal quantum dots in a polymer matrix are demonstrated. In the case of doping the polymer with both types of quantum dots, the nanocomposite film guides both emitted colors, green (550?nm, CdTe) and orange (600?nm, CdSe). The optical pumping laser can be coupled not only with a standard end-fire coupling system, but also directing the beam to the surface of the sample, indicating a good absorption cross-section and waveguide properties. To achieve these results, a study of the nanocomposite optical properties as a function of the nanocrystal concentration is presented and the optimum conditions are found for waveguiding.     

Layer-by-layer assembly of multicolored semiconductor quantum dots towards efficient blue, green, red and full color optical films

Multicolored semiconductor quantum dots have shown great promise for construction of miniaturized light-emitting diodes with compact size, low weight and cost, and high luminescent efficiency. The unique size-dependent luminescent property of quantum dots offers the feasibility of constructing single-color or full-color output light-emitting diodes with one type of material. In this paper, we have demonstrated the facile fabrication of blue-, green-, red-?and full-color-emitting semiconductor quantum dot optical films via a layer-by-layer assembly technique. The optical films were constructed by alternative deposition of different colored quantum dots with a series of oppositely charged species, in particular, the new use of cationic starch on glass substrates. Semiconductor ZnSe quantum dots exhibiting blue emission were deposited for fabrication of blue-emitting optical films, while semiconductor CdTe quantum dots with green and red emission were utilized for construction of green-?and red-emitting optical films. The assembly of integrated blue, green and red semiconductor quantum dots resulted in full-color-emitting optical films. The luminescent optical films showed very bright emitting colors under UV irradiation, and displayed dense, smooth and efficient luminous features, showing brighter luminescence in comparison with their corresponding quantum dot aqueous colloid solutions. The assembled optical films provide the prospect of miniaturized light-emitting-diode applications.     

Hydrothermal synthesis for high-quality CdTe quantum dots capped by cysteamine

We present a facile hydrothermal approach to synthesize high-quality cysteamine (CA)-capped CdTe quantum dots (QDs). Oil bath heating and vigorous stirring were used to obtain better heat transfer and more homogenous solutions during the synthesis process. By this approach, the quantum yield (QY) of the resultant QDs can reach as high as 19.7%, which is the best reported data for CA-stabilized CdTe QDs. The synthesis process is under a high concentration of the precursor (> 10 mM), suggesting the potential of this route to be used in mass production of CA-capped CdTe QDs. Moreover, the pH-dependent optical properties of CA-capped CdTe QDs were also investigated.