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。     

CdSe:X/ZnS掺杂型核壳量子点的化学合成及光谱性质研究

采用绿色合成工艺,通过在核壳量子点中掺杂不同的金属离子,在水溶液中合成了CdSe∶X/ZnS掺杂型核壳量子点。并利用多种分析测试手段对合成产物的结构以及光谱性质进行了详细地研究。XRD分析表明,核壳结构的量子点的衍射峰相对内层CdSe量子点向高角度方向移动,掺杂型核壳量子点的衍射峰较未掺杂量子点有向高角度移动趋势,合成量子点的平均晶粒尺寸约为2.3nm。SEM结果表明,合成的核壳量子点近似为球形。量子点的吸收峰与体材料相比,产生明显的蓝移,表现出明显的量子限域效应。样品具有很好的亲水性,在红外光线照射下出现丁达尔效应,样品的FT-IR结果表明配体MPA成功包覆在量子点的表面。     

CdSe/ZnSe量子点的制备及电化学发光性能

利用ZnSe半导体纳米材料晶体结构与CdSe相似、带隙更宽的特点,采用水热法合成了核-壳型CdSe/ZnSe量子点。结果表明：温度在70~160℃时,ZnSe壳逐渐包裹在CdSe核上,反应时间在0~4 h时,内壳在核上是均匀包裹的,当核壳摩尔比为1∶3时,CdSe/ZnSe QDs的电化学发光性能最强,其电化学发光强度是CdSe量子点的6倍,且发光信号稳定。     

水相中CdSe与核/壳CdSe/CdS量子点的制备与发光特性研究

以巯基乙酸为稳定剂在水相中制备了CdSe与核/壳型CdSe/CdS量子点水溶胶, 用紫外-可见吸收光谱和发射光谱研究了它们的发光特性, 并且用X射线粉末衍射(XRD)、透射电镜(TEM)和X射线光电子能谱(XPS)表征了它们的结构、形貌和化学组成, 结果表明使用该方法制备的量子点分散性良好, 而且用CdS对CdSe进行表面修饰以后的发光强度明显提高, 发射光谱和吸收光谱都有红移现象, 不同粒径颗粒的吸收峰的位置也有所不同.     

在多相体系中制备核壳型CdSe/ZnS量子点

在多相体系中制得了CdSe/ZnS半导体量子点,采用X射线粉末衍射(XRD)、电子透射显微镜(TEM)等测试手段对产物进行了表征,结果表明CaSe/CdS量子点尺寸均一、形貌规则,具有立方晶体结构.初步研究了此体系的反应机理,并通过紫外-可见吸收光谱和荧光光谱对产物的光学性质进行了分析,结果表明在CASe量子点外面包覆一定厚度的ZnS壳层后,其激子发射强度和量子效率显著提高.     

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)。     

CdSe与CdSe/ZnS量子点合成及稀土掺杂

在LSS(liquid-solid-solution)多相体系中制得了CdSe、CdSe/ZnS量子点和Eu掺杂的量子点。利用TEM、XRD、PL、EDS对产物进行了表征。TEM结果显示所得的量子点形貌规则、尺寸均匀。XRD结果显示CdSe/ZnS量子点呈六方晶系。PL结果对比表明,合适厚度壳层ZnS包覆后的CdSe量子点发光效率明显提高,发光峰的半高宽有大幅度提高,并分析了所得的结果。掺杂稀土元素Eu后,CdSe(Eu)量子点在红光区域产生了新的发光峰;而CdSe(Eu)/ZnS量子点在红光区域内没有出现发光峰,并阐明了这种现象的原因。     

CdSe量子点的制备及荧光性能改善

主要讨论了CdSe量子点的制备及荧光性能的改善.采用水相合成方法制备了CdSe量子点,并用X射线粉末衍射仪对所合成的量子点进行表征,用荧光分光光度计研究了量子点的荧光性质.结果表明,采用样品处理温度的调节和ZnS壳层的包覆能在一定程度上改善CdSe量子点的荧光性能.     

水相合成CdTe量子点及其性能表征

以NaTeO3为碲源,巯基乙酸(TGA)为稳定剂,合成CdTe量子点。研究Cd2+的浓度、Cd2+-TGA前驱体室温静置时间对CdTe量子点荧光光谱、荧光量子效率的影响,并用X射线粉末衍射仪和透射电子显微镜对其结晶性能、结构以及形貌进行表征。实验表明,所制备的CdTe量子点具有闪锌矿结构和球形形貌。且在Cd2+-TGA前驱体室温静置50min后参与回流,Cd2+浓度为0.00067mol/L时,荧光量子效率最高可达48.4%。     

水溶性量子点制备条件的优化及表面修饰

以L-半胱氨酸为稳定剂在水溶液中合成CdSe纳米粒子,研究了水浴时间、水浴温度、不同L-半胱氨酸/Cd/Se比例、pH值等因素对其荧光光谱的影响,确定了最佳的合成方案.用CdS对其表面进行修饰,采用透射电镜、X射线衍射、光谱法等表征了Cdse/CdS核壳结构颗粒的形成,结果表明该纳米粒子发光强度明显高于单一的CdSe量子点,光谱峰位置有所红移;合成条件会显著影响CASe/CAS核壳结构量子点的荧光性能.     

One-pot synthesis of highly luminescent CdTe quantum dots by microwave irradiation reduction and their Hg2+-sensitive properties

A facile one-pot microwave irradiation reduction route has been developed for the synthesis of highly luminescent CdTe quantum dots using Na₂TeO₃ as the Te source in an aqueous environment. The synthesis parameters of this simple and rapid approach, including the reaction temperature and time, the pH of the reaction solution and the molar ratio of the 3-mercaptopropionic acid (MPA) stabilizer to Cd²⁺, have considerable influence on the particle size and photoluminescence quantum yield of the CdTe quantum dots. The photoluminescence quantum yield of CdTe quantum dots prepared using relatively short reaction times (10–40 min) reached 40%–60% (emission peaks at 550–640 nm). Furthermore, the resulting products could be used as fluorescent probes to detect Hg²⁺ ions in aqueous media. The response was linearly proportional to the concentration of Hg²⁺ ion in the range 8.0×10⁻⁹ mol/L to 2.0×10⁻⁶ mol/L with a detection limit of 2.7×10⁻⁹ mol/L. Electronic Supplementary Material  Supplementary material is available for this article at and is accessible for authorized users.     

Recombination dynamics in CdTe/CdSe type-II quantum dots

Recombination dynamics in CdTe/CdSe core-shell type-II quantum dots (QDs) has been investigated by time-resolved photoluminescence (PL) spectroscopy. A very long PL decay time of several hundred nanoseconds has been found at low temperature, which can be rationalized by the spatially separated electrons and holes occurring in a type-II heterostructure. For the temperature dependence of the radiative lifetime, the linewidth and the peak energy of PL spectra show that the recombination of carriers is dominated by delocalized excitons at temperatures below 150?K, while the mixture of delocalized excitons, electrons and holes overwhelms the process at higher temperature. The binding energy of delocalized excitons obtained from the temperature dependence of the non-radiative lifetime is consistent with the theoretical value. The energy dependence of lifetime measurements reveals a third power relationship between the radiative lifetime and the radius of QDs, the light of which can be shed by the quantum confinement effect. In addition, the radiative decay rate is found to be proportional to the square root of excitation power, arising from the change of wavefunction overlap of electrons and holes due to the band bending effect, which is an inherent character of a type-II band alignment.     

Synthesis of highly luminescent CdTe/ZnO core/shell quantum dots in aqueous solution

The synthesis and photoluminescence (PL) properties of aqueous CdTe/ZnO core/shell quantum dots (QDs) have been investigated by using thiolglycolic acid as a capping reagent. The highlighted contribution of the present study was CdTe QDs coated with a ZnO shell by controlling the hydrolysis process of Zn(OAc)₂. The QDs benefitted from overcoming the high lattice mismatch between CdTe and ZnO. The PL peak wavelength of the CdTe/ZnO QDs with high PL quantum yields up to 88% was located in a range between 547 and 596 nm by adjusting the size of CdTe cores and the thickness of ZnO shells. The results of X-ray diffraction analysis and transmission electron microscopy observation indicate that the dot-shaped CdTe/ZnO QDs (566 nm) with an average size of 2.2 nm in diameter belong to the cubic CdTe crystal structure. Due to the passivation of surface defects, it is found that the luminescence decay curves accord with a biexponential decay model of exciton and trap radiation behavior. The average PL lifetimes of CdTe (571 nm) and CdTe/ZnO (596 nm) QDs at room temperature are 27.3 and 35.1 ns, respectively.     

Sequential synthesis of type II colloidal CdTe/CdSe core-shell nanocrystals

Colloidal type II CdTe/CdSe nanocrystals were synthesized by sequential addition of a tri-n-octylphosphine telluride (TOPTe)/TOP solution and several shell-precursor solutions to a CdO/TOP solution; the shell-precursor solutions consisted of CdO and TOPSe in TOP. For the growth of the CdTe core, the TOPTe/TOP solution was swiftly added to the CdO/TOP solution at a higher temperature (300 degrees C) than the growth temperature (250 degrees C). For the growth of the CdSe shell, in contrast, the CdO/TOPSe/TOP solution was slowly added to the CdTe/TOP solution at a lower temperature than the growth temperature (200-240 degrees C). The temporal evolution of the optical properties of the growing core-shell nanocrystals was monitored in detail. During the growth of the CdSe shell, the core-shell nanocrystals exhibited interesting changes in photoluminescence (PL) properties. The highest PL efficiency (approximately 38 %) was detected from core-shell nanocrystals with a CdSe shell thickness of 0.4-0.5 nm (indicated by TEM); the formation of the first monolayer is proposed. Our synthetic approach is well suited to a practical realization of engineering materials with bandgaps in the near-IR and IR spectral ranges.     

One-step synthesis of water-soluble ZnSe quantum dots via microwave irradiation

A facile strategy has been developed for the synthesis of glutathione-capped ZnSe quantum dots (QDs) in aqueous media. The reaction was carried out in air atmosphere with a single step by using Na₂SeO₃, a stable and commercial Se source, to replace the commonly adopted NaHSe or H₂Se. Moreover, microwave irradiation improved the photoluminescence quantum yield (PLQY) as well as lowered the trap emission of as-prepared ZnSe QDs. The obtained QDs performed strong band-edge luminescence (PLQY reached 18%), narrow size distribution (full width at half maximum was 26-30 nm) and weak trap emission without post-treatments. The results of transmission electron microscopy and X-ray diffraction demonstrated the small particle size (2-3 nm), good monodispersity and ZnSe(S) alloyed structure of as-prepared QDs. The experimental variables including precursors and stabilizer amounts as well as pH value had significant influence on the PL properties of the ZnSe QDs.     

Aqueous synthesis of highly monodispersed thiol-capped CdTe quantum dots through electrochemical approach

A facile green approach has been developed to control the growth regime in the aqueous synthesis of CdTe semiconductor Quantum dots (QDs) via the electrochemistry method. The Low growth temperature and slow injection of Te precursors are used to prolong the diffusion controlled stage and thus suppress Ostwald ripening during nanocrystal growth. The experimental results showed that a low concentration of Te precursor would definitely influence the growth procedure. The narrow absorption peaks in the UV-visible absorption spectra, as well as transmission electron microscopy images indicated that the as-prepared CdTe QDs had a good monodispersity. The high-resolution transmission electron microscopy (HRTEM) images and powder X-ray diffraction (XRD) pattern suggested that the as-prepared QDs have high crystallinity and cubic structure. The QDs exhibited high fluorescence QYs about 50% and the best of QY 67% without any postpreparative treatment over a broad spectral range of 516-609 nm, which could be further broadened by long-term refluxing. The current work suggested that electrochemical method was an attractive approach to the synthesis of high-quality II-VI semiconductor QDs at a large scale.     

Highly luminescent CdSe/ZnSe core-shell quantum dots of one-pot preparation in octadecene

CdSe/ZnSe core-shell quantum dots were synthesized using a new one-pot procedure where the core was prepared in octadecene. A ZnSe shell around a CdSe nanoparticle was formed by the reaction of selenium-richness on the surfaces of CdSe nanoparticles with Zn2+ from the injected zinc stearate precursor. The optical properties, luminescence kinetics, and the effect of shell thickness of as-prepared QDs were studied, which verifies the high quality of the resulting QDs. The new approach is effective not only for preparing core/shell QDs, but also for reducing the complexity of synthesis, toxicity, and reagent cost.     

Low temperature synthesis of colloidal CdSe quantum dots

In this study, the CdSe nanocrystals were prepared in phenyl ether and octyl amine to investigate the variations of their size, bandgap energy, and photoluminescence with growth time and temperature. The sizes of the CdSe nanocrystals were measured using High Resolution Transmission Electron Microscopy (HRTEM), and found to be nearly monodisperse for relatively low growth temperature, 130 degrees C. Their optic properties were characterized by photoluminescence measurements, which showed that the colors of the nanocrystals could be controlled. The bandgap energies of the nanocrystals were calculated theoretically and found to be in accord with quantum confinement theory. This synthetic method requires only a cheap solvent and offers good reproducibility at a lower price.     

Aqueous synthesis of CdSe and CdSe/CdS quantum dots with controllable introduction of Se and S sources

A new and convenient route is developed to synthesize CdSe and core–shell CdSe/CdS quantum dots (QDs) in aqueous solution. CdSe QDs are prepared by introducing H₂Se gas into the aqueous medium containing Cd²⁺ ions. The synthesized CdSe QDs are further capped with CdS to form core–shell CdSe/CdS QDs by reacting with H₂S gas. The gaseous precursors, H₂Se and H₂S, are generated on-line by reducing SeO₃ ^2? with NaBH₄ and the reaction between Na₂S and H₂SO₄, and introduced sequentially into the solution to form CdSe and CdSe/CdS QDs, respectively. The synthesized water-soluble CdSe and CdSe/CdS QDs possess high quantum yield (3 and 20 %) and narrow full-width-at-half-maximum (43 and 38 nm). The synthesis process is easily reproducible with simple apparatus and low-toxic chemicals. The relatively standard deviation of maxima fluorescence intensity is only 2.1 % (n = 7) for CdSe and 3.6 % (n = 7) for CdSe/CdS QDs. This developed route is simple, environmentally friendly and can be readily extended to the large-scale aqueous synthesis of QDs.     

One-step and rapid synthesis of high quality alloyed quantum dots (CdSe-CdS) in aqueous phase by microwave irradiation with controllable temperature

In this paper, we presented a seed-mediated approach for rapid synthesis of high quality alloyed quantum dots (CdSe-CdS) in aqueous phase by microwave irradiation with controllable temperature in 1 h. In the synthesis, CdSe seeds were first formed by the reaction of NaHSe and Cd²⁺, and then alloyed quantum dots (CdSe-CdS) were rapidly produced by releasing of sulfide ions from 3-mercaptopropionic acid as sulfide source with microwave irradiation. The alloyed quantum dots synthesized had good optical properties, the quantum yield was up to 25%, and the full width at half maximum of the emission spectrum peak was about 28 nm. The as-prepared alloyed CdSe-CdS QDs were characterized by XRD, XPS and ICP-AES in order to explore the structure and component of the alloyed nanocrystals and the reaction mechanism. We speculate that the alloyed CdSe-CdS quantum dots may exist a gradient internal structure according to our preliminary results.