One-Pot Synthesis of Biocompatible CdSe/CdS Quantum Dots and Their Applications as Fluorescent Biological Labels

We developed a novel one-pot polyol approach for the synthesis of biocompatible CdSe quantum dots (QDs) using poly(acrylic acid) (PAA) as a capping ligand at 240°C. The morphological and structural characterization confirmed the formation of biocompatible and monodisperse CdSe QDs with several nanometers in size. The encapsulation of CdS thin layers on the surface of CdSe QDs (CdSe/CdS core–shell QDs) was used for passivating the defect emission (650 nm) and enhancing the fluorescent quantum yields up to 30% of band-to-band emission (530–600 nm). Moreover, the PL emission peak of CdSe/CdS core–shell QDs could be tuned from 530 to 600 nm by the size of CdSe core. The as-prepared CdSe/CdS core–shell QDs with small size, well water solubility, good monodispersity, and bright PL emission showed high performance as fluorescent cell labels in vitro. The viability of QDs-labeled 293T cells was evaluated using a 3-(4,5-dimethylthiazol)-2-diphenyltertrazolium bromide (MTT) assay. The results showed the satisfactory (>80%) biocompatibility of as-synthesized PAA-capped QDs at the Cd concentration of 15 μg/ml.     

Photoluminescence of CdTe quantum dots ligated with caprylic acid synthesized at low temperature

Photoluminescent semiconductor nanocrystals or quantum dots (QDs) are usually produced using expensive ligands and solvents at high temperature above 280°C to ensure high-quality optical properties, particularly the photoluminescence of QDs. The reproducibility of highly stable photoluminescence in QD preparation, in most cases, varies depending on many effects, such as the ligand used and temperature. Here a facile preparation of photoluminescent semiconductor CdTe nanocrystals or quantum dots (QDs) is conducted in the presence of caprylic acid at moderate temperatures between 80–140°C, which are much lower than the high temperatures used in conventional organic-phase preparation of CdTe QDs. The results show that the optical properties of CdTe QDs depend considerably on the reaction time, temperature and ligand used.     

Photoluminescence enhancement of quantum dots on Ag nanoneedles

ABSTRACT: Noble-metal nanostructure allows us to tune optical and electrical properties, which has high utility for real-world application. We studied surface plasmon induced emission of semiconductor quantum dots (QDs) on engineered metallic nanostructures. Highly passive organic ZnS capped CdSe QDs were spin coated on poly-(methyl methacrylate) (PMMA) covered Ag films which brought QDs near to metallic surface. We obtained the enhanced electromagnetic field and reduced fluorescence lifetimes from CdSe/ZnS quantum dots (QDs) due to the strong coupling of emitters wave function with the Ag plasmon resonance. Observed changes include a six-fold increase in the fluorescence intensity and striking reduction in fluorescence lifetimes of CdSe/ZnS QDs on rough Ag nanoneedle compared to the case of smooth surfaces. The advantages of using those nanocomposites are expected for high efficiency light-emitting diodes, platform fabrication of biological and environmental monitoring, and high contrast imaging.     

Fast access to core/shell/shell CdTe/CdSe/ZnO quantum dots via magnetic hyperthermia method

The intrinsic low quantum yield (QY) of type II core shell quantum dots (QDs) composes the limitation for these heterostructured nanomaterials to be used in practical application. Herein, magnetic hyperthermia method is employed to intensify reaction process and facilely synthesize CdTe/CdSe heterostructured QDs with improved optical performance for the first time. The QY of the type II QDs is increased to 49% by further growing an inert ZnO layer. The type I interface between CdSe and ZnO helps confine electrons to the inner structure of the QDs, thus improving the QY. The successful preparation and performance enhancement of the CdTe/CdSe type II QDs via magnetic hyperthermia method demonstrate the great potential of this method for the preparation of other materials. Besides, the red‐emission QDs are used as conversion materials in white light emitting diodes to reveal their promising application in practical illumination. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2614–2621, 2016     

The growth of CdSe quantum dots on a single wall carbon nanotubes template without organic solvent and surfactant

A conventional synthesis of Cadmium selenide (CdSe) quantum dots (QDs) usually employs toxic organic solvents, and the synthesized CdSe QDs must be modified for dispersion in an aqueous solution. This modification often limits the application of CdSe QDs in biomedical fields. In this study, a simple method was developed to synthesize CdSe QDs on single wall carbon nanotubes (SWCNTs) employing the SWCNTs as a template to prevent the aggregation of the CdSe QDs in an aqueous solution without the addition of any organic reagent.Our newly developed synthetic procedure included the formation of SWCNTs with carboxyl groups (SWCNT-COOHs) followed by mixing these with the precursors of Cd and Se to obtain SWCNT-CdSe QDs. The resulting SWCNT-CdSe QDs were analyzed using spectrophotometry, transmission electron microscopy (TEM) and X-ray diffraction (XRD).Results showed that CdSe nanocrystals with a zinc blend structure could be synthesized on the SWCNT-COOHs. The average crystal size of the synthesized CdSe QDs was approximately 3 nm. The blue-shift of CdSe QDs powerfully emitted light at 550 nm as compared to the bulk CdSe at 730 nm. These CdSe QDs were synthesized in an aqueous environment without using toxic surfactants and are expected to have great potential as bio-labeling contrast agents in the future.     

CdSe量子点标记免疫球蛋白及光谱性质研究

以巯基乙酸为稳定剂合成了CdSe量子点,利用X-射线粉末衍射(XRD)和透射电镜(TEM)对量子点结构进行了表征,粒径约为5 nm。以碳二亚胺为缩合剂将量子点与免疫球蛋白共价连接,光谱实验结果表明CdSe量子点与免疫球蛋白有效结合,其荧光发射峰发生了红移,而半峰宽和发射强度没有明显变化。     

Nanotetrapods: quantum dot hybrid for bulk heterojunction solar cells

Hybrid thin film solar cell based on all-inorganic nanoparticles is a new member in the family of photovoltaic devices. In this work, a novel and performance-efficient inorganic hybrid nanostructure with continuous charge transportation and collection channels is demonstrated by introducing CdTe nanotetropods (NTs) and CdSe quantum dots (QDs). Hybrid morphology is characterized, demonstrating an interpenetration and compacted contact of NTs and QDs. Electrical measurements show enhanced charge transfer at the hybrid bulk heterojunction interface of NTs and QDs after ligand exchange which accordingly improves the performance of solar cells. Photovoltaic and light response tests exhibit a combined optic-electric contribution from both CdTe NTs and CdSe QDs through a formation of interpercolation in morphology as well as a type II energy level distribution. The NT and QD hybrid bulk heterojunction is applicable and promising in other highly efficient photovoltaic materials such as PbS QDs.     

CdSe量子点的合成及其对潜指纹的荧光显现研究

以水热法在水相中直接合成了巯基乙酸修饰的CdSe量子点,并将合成的CdSe量子点进行表征、纯化。在波长365nm紫外光的激发下,CdSe量子点发射出明亮的黄绿色荧光,荧光发射峰约位于528nm,将得到的CdSe量子点纳米发光材料应用于非渗透性客体上潜指纹的荧光标记成像研究,发现CdSe量子点溶液显现的手印纹线流畅,显现细节特征明显,呈现明亮的黄绿色荧光指纹,具有很高的实用价值和鉴定价值。     

谷氨酰胺为稳定剂制备硒化镉纳米晶及光谱性质研究

以谷氨酰胺(Gln)为稳定剂合成了硒化镉纳米晶,利用X-射线粉末衍射(XRD)和透射电镜(TEM)对纳米晶结构进行了表征,粒径约为20 nm。通过紫外-可见吸收光谱、激发光谱与发射光谱研究了纳米晶光谱特性。实验结果表明,反应温度过高、反应时间过长都会破坏谷氨酰胺(Gln)的稳定作用,使CdSe聚集,影响其荧光性质。而聚乙二醇(PEG)的加入会使纳米晶的荧光发射明显加强,而且发射峰峰形尖锐。     

PS/PMMA-CdSe/ZnS Quantum Dots Hybrid Nanofibers for VOCs Sensors

Hybrid nanofibers containing CdSe/ZnS quantum dots have been produced by electrospinning of hybrid latexes to characterize the electro-optical behavior of this novel luminescent sensing material. The latexes are synthesized by seeded semi-batch emulsion polymerization yielding cross-linked core-shell PS/QDs/PMMA particles with efficiently encapsulated quantum dots guaranteeing a good optical stability. Addition of polyvinyl alcohol (PVA) or polyethylene oxide (PEO) to the latexes is necessary to produce polymeric dispersions suitable for electrospinning manufacture of the nanometric fibers. The optimized polymeric dispersions are successfully electrospun obtaining fluorescent nanofibers in both cases. The hybrid nanofibers are sensitive to selected solvents (acetone, methanol and THF) and present positive response making them good candidates for the production of VOC sensors.     

CdSe/SiO_2荧光微球的制备及其荧光性能(英文)

利用Stber法制备了CdSe/SiO2荧光微球。用透射电子显微镜,共聚焦显微镜和X射线衍射测试荧光微球的形貌和晶体结构;用荧光光谱表征荧光微球的荧光性能;用动态-静态激光散射仪表征荧光微球的尺寸分布。结果表明:CdSe量子点被包裹在SiO2微球内,并形成了具有良好荧光性能的CdSe/SiO2荧光微球,其荧光性能与合成工艺条件有着显著的相关性。     

Surface plasmon enhanced energy transfer in metal-semiconductor hybrid nanostructures

We report a type of hybrid nanostructures composed of ZnO nanoparticles, CdSe/ZnS core/shell quantum dots (QDs), and Ag nanoprisms. With ultraviolet light illumination, the energy absorbed by ZnO nanoparticles was transferred to the CdSe/ZnS core/shell QDs inducing a photoluminescence (PL) emission. To enhance the PL emission, Ag nanoprisms were doped in the ZnO nanoparticles and the QDs. Enhanced energy transfer from the ZnO nanoparticles to the QDs via the surface plasmon effect of the Ag nanoprisms was also demonstrated. The PL emission dependence was investigated as a function of the doped Ag nanoprism concentration and a 7.4 times PL enhancement was obtained at an Ag nanoprism concentration of 5 × 10(-8) M.     

CdSe∶Mn量子点的制备及其光致发光特性研究

采用低温水热法,以柠檬酸为配位稳定剂制备了Mn2＋掺杂的CdSe量子点。用紫外吸收光谱、荧光发射光谱、X射线衍射（XRD）、透射电镜（TEM）等进行了表征。研究了Mn2＋掺杂浓度对量子点的结构及其光致发光性能的影响。光致发光光谱表明,当粒子尺寸为3 nm时,在580 nm处出现了属于Mn2＋的4T1-6A1跃迁的特征发射峰。当激发波长为480 nm时,在630 nm处出现了CdSe的表面缺陷发射峰。随着Mn2＋的掺杂浓度增大,CdSe∶Mn表面陷阱态发射峰位置没有显著红移。TEM分析结果显示,CdSe∶Mn量子点为单分散的,尺寸约为5 nm的圆形纳米粒子。当Mn2＋离子掺杂浓度不大于5%时,Mn2＋取代表面晶格中的Cd2＋离子位置形成辐射性表面缺陷,产生表面陷阱态发射。吸收光谱显示,随着量子点变小,吸收带边发生蓝移,显示明显的量子尺寸效应。     

硒化镉量子点的二氧化硅包覆

将油溶性、单分散、高荧光强度的CdSe荧光纳米晶用Stber方法成功地制备了SiO2包覆的荧光纳米晶,包覆后的纳米晶在水中和醇中有良好的溶解性,具有非常好的化学稳定性。SiO2包覆后的纳米晶也具有较强的荧光特性。..     

Fabrication of surface‐modified CdSe quantum dots by self‐assembly of a functionalizable comb polymer

A facile approach is proposed for the fabrication of surface‐modified CdSe quantum dots (QDs) with compatibility with various media and better dispersibility by self‐assembly of a functionalizable comb polymer. The comb polymer was prepared from the reaction between the acyl chloride groups in poly(acryloyl chloride) and the hydroxyl groups in 1‐octadecanol. With the combination of the compatibility and entanglement of the aliphatic chain in 1‐octadecanol and similar aliphatic chain in oleic acid ligand of QDs, the comb polymer could cap on the QDs and thus endow them with functional groups. The structure of such a polymer was investigated using Fourier transform infrared spectroscopy. According to the reactivity of remaining acyl chloride groups in the comb polymer, the polymer ligands could be tailored to be various structures, and then lipophilic, hydrophilic and functional QDs were obtained. The fluorescence properties of the surface‐modified QDs were investigated, and the morphologies and dispersions of different kinds of surface‐modified QDs were characterized using transmission electron microscopy. Finally, homogeneous and stable dispersions of QDs in various media could be realized by adjusting the structure of the comb polymer. Copyright © 2010 Society of Chemical Industry     

Chitosan/P3HT biohybrid films as polymer matrices for the in-situ synthesis of CdSe quantum dots. Experimental and theoretical studies

Biohybrid nanocomposite films were obtained through a simple two-step methodology. Films of chitosan/poly(3-hexylthiophene) (CS/P3HT) were used as polymer matrices for the in-situ synthesis and stabilization of CdSe quantum dots. The biohybrid materials were characterized by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), Raman spectroscopy, UV–visible spectroscopy, thermogravimetric analysis (TGA), field emission scanning electron microscope (FESEM), high-resolution transmission electron microscopy (HRTEM), and photoluminescence spectroscopy (PL). The effects of the P3HT composition on the properties of the QDs in the films were analyzed. The results confirmed that CS/P3HT films provided an adequately confining matrix for the growth of CdSe QDs with a fairly uniform size and revealed that the interactions between the CdSe nanoparticles and the CS/P3HT matrix mainly involved the  OH and  NH₂ groups. The optical band gaps of the biohybrid nanocomposite films were estimated. The results of photoluminescence revealed that a charge transfer phenomenon occurred in the polymer system. Finally, theoretical analyses suggest that the CdSe QDs would be preferentially located onto the chitosan domains.     

Preparation and characterization of silicone resin nanocomposite containing CdSe/ZnS quantum dots

We report the preparation of the core/shell cadmium selenide/Zinc sulfide quantum dots (CdSe/ZnS QDs)‐silicone resin nanocomposite through the solution‐mixing method, followed by thermal hydrosilylation. After dispersing QDs into Dow Corning two‐component silicone resins (OE6630A and OE6630B at 1:4 mixing ratio by weight), the resins were cured at 150°C for 1.5 h to produce QD‐silicone resin nanocomposites. The curing behavior of the silicone resins resulting from the thermal hydrosilylation was studied using differential scanning calorimetry (DSC). The properties of the QD‐silicone resin nanocomposites were investigated by ultraviolet–visible (UV–vis), fluorescence, confocal laser scanning microscopy (CLSM), atomic force microscopy (AFM), and thermogravimetric analysis (TGA) measurements. The QDs that contain trioctylamine (TOA) as the original ligand can poison the Pt catalyst in the resins and inhibit the curing process by increasing the exothermic peak temperature, at which a lower heat of hydrosilylation is observed. Incorporating a small amount of CdSe/ZnS QDs (0.1 wt%) can greatly improve the thermal stability of the silicone resins. Moreover, CdSe/ZnS QDs tend to form clusters that are relatively homogeneously distributed in a cured silicone resin, offering good optical properties of 11.2 lm W⁻¹ luminous efficiency and 14.6% photoluminescence conversion efficiency (PCE) in light emitting device (LED) test. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Understanding the atomic and electronic structures origin of defect luminescence of CdSe quantum dots in glass matrix

Well-defined density functional theory (DFT) calculations are performed as the first exploratory study for the atomic and electronic mechanism of defect mediated morphology and optical properties of Cd_nSe_n (n = 3, 10, 13, and 33) quantum dots (QDs) in inorganic amorphous matrix. The intrinsic defects of pristine CdSe QDs, and the interfacial defects between the QDs and surrounding amorphous matrix, were systematically studied. The calculated electronic structure suggested that the pristine CdSe QDs capped by the structural modifiers or non-bridging oxygen in the amorphous matrix gave rise to the structure reconstruction and paired defect states at the edge of the valence and conduction bands. The orbital analysis elucidated that the redistribution of the majority of HOMO and LUMO electron density was localized over the bonds formed by capping atoms and QDs. These changes in the electronic structures were further demonstrated by CdSe QDs embedded sodium silicate glasses. It turned out that Se atoms at QDs/glass interface were much more active than those found on the surface of organically passivated CdSe QDs. The results serve as a new paradigm in materials research to explore structural origins of defect emission from QDs and a new strategy to develop glasses containing QDs with high photoluminescence quantum efficiency.     

巯基乙酸稳定的CdSe/ZnS核壳结构量子点的制备与表征

用非均相成核原理,在水溶液中制备CdSe/ZnS核壳结构量子点,并研究合成工艺,包括前驱物的滴加方式和用量、CdSe核的水浴反应时间、CdSe与ZnS的摩尔比等因素对CdSe/ZnS核壳结构量子点荧光性能的影响.用透射电子显微镜和x射线衍射仪测试核壳结构量子点的形貌和结构.用紫外吸收光谱与荧光光谱表征CdSe/ZnS核壳结构量子点的荧光性能.结果表明:ZnS壳层在CdSe核量子点表面外延生长,形成了核壳结构;CdSe/ZnS核壳结构量子点的荧光性能明显高于单一的CdSe量子点;合成的工艺条件会显著影响CdSe/ZnS核壳结构量子点的荧光性能.     

Shell-Controlled Photoluminescence in CdSe/CNT Nanohybrids

A new type of nanohybrids containing carbon nanotubes (CNTs) and CdSe quantum dots (QDs) was prepared using an electrostatic self-assembly method. The CdSe QDs were capped by various mercaptocarboxylic acids, including thioglycolic acid (TGA), dihydrolipoic acid (DHLA) and mercaptoundecanoic acid (MUA), which provide shell thicknesses of ~5.2, 10.6 and 15.2 Å, respectively. The surface-modified CdSe QDs are then self-assembled onto aridine orange-modified CNTs via electrostatic interaction to give CdSe/CNT nanohybrids. The photoluminescence (PL) efficiencies of the obtained nanohybrids increase significantly with the increase of the shell thickness, which is attributed to a distance-dependent photo-induced charge-transfer mechanism. This work demonstrates a simple mean for fine tuning the PL properties of the CdSe/CNT nanohybrids and gains new insights to the photo-induced charge transfer in such nanostructures.