Conjugations between Cysteamine-Stabilized CdTe Quantum Dots and Single Stranded DNA

Abstract

Cysteamine-stabilized CdTe quantum dots were used to directly conjugate with single stranded DNA through electrostatic attraction between positive amino function groups on the surface of CdTe quantum dots and negatively charged DNA. The conjugates exhibited different optical properties from that of CdTe quantum dots, for example, the fluorescence intensity was enhanced obviously with maximum emission peaks gradually red-shifting, and the conjugates were more stable. Under the optimum conditions, the fluorescence intensity was proportional to concentration of DNA over the range 0.16–0.48 µg/mL. This proposed method demonstrated a versatile tool for the fluorescence probing of target DNA and fluorescence labeling.     

Fluorescence Protection of CdTe Quantum Dots and Usages in Cellular and in vivo Imaging

The nanocomposites of poly(diallyldimethylammonium chloride) (PDADMAC) and CdTe quantum dots (QDs) (i.e., QD-PDADMAC nanocomposites) have been prepared based on electrostatic interaction. Transmission electron microscopy, Fourier transform infrared spectroscopy, and Zeta potential analysis were used to characterize the prepared QD-PDADMAC nanocomposites. It was shown that the QD-PDADMAC nanocomposites have the specific curly-shaped band-like morphology with the width of 4–8 nm and unequal length, and there are rich positive charges on the surface of the nanocomposites. The prepared QD-PDADMAC nanocomposites also had good fluorescence stability. The usage based on their good stability has also been studied by cellular and in vivo imaging. In comparison with the QDs without PDADMAC protection, the obtained QD-PDADMAC nanocomposites have better fluorescence stability and staining effect in biology imaging. After incubation for 24 h at 37°C, A549 lung cancer cells were almost not stained by QDs, similarity to the culture medium control group, and could be clearly stained by QD-PDADMAC nanocomposites. For in vivo imaging of mice by intraperitoneal injection, the fluorescence of QDs could not be seen in abdominal cavity at 30 min, and the nanocomposites' one could still be clearly observed at a longer time (1 h). Moreover, the intestine in the large area of the abdominal cavity was effectively stained.     

Investigation of ultrafast dynamics of CdTe quantum dots by femtosecond fluorescence up-conversion spectroscopy

The ultrafast carrier relaxation processes in CdTe quantum dots are investigated by femtosecond fluorescence upconversion spectroscopy.Photo-excited hole relaxing to the edge of the forbidden gap takes a maximal time of ～ 1.6 ps with exciting at 400 nm,depending on the state of the photo-excited hole.The shallow trapped states and deep trap states in the forbidden gap are confirmed for CdTe quantum dots.In addition,Auger relaxation of trapped carriers is observed to occur with a time constant of ～ 5 ps.A schematic model of photodynamics is established based on the results of the spectroscopy studies.Our work demonstrates that femtosecond fluorescence up-conversion spectroscopy is a suitable and effective tool in studying the transportation and conversion dynamics of photon energy in a nanosystem.     

近空间升华法制备CdS多晶薄膜的研究

系统地研究了近空间升华法(CSS)制备CdS薄膜沉积速率的影响因素。发现CdS薄膜的沉积速率随升华源温度的升高而增大,但随衬底温度和沉积气压的上升而下降。对所制备样品的结构、表面形貌和光谱透过率特性进行了测试,结果表明：(1)不同氧分压下沉积的CdS薄膜沿(103)晶向择优生长。CdCl₂氛围下退火后,(103)晶向的优势得到进一步加强;(2)不同氧分压制备的CdS薄膜致密且粒径均匀,晶粒的大小随着衬底温度的升高而增大,但薄膜的粗糙度也随之增大;(3)随着CdS薄膜厚度的减小,可见光中短波段的透过率有所增大,有利于提高太阳电池的短波光谱响应。并将CSS制备的CdS多晶薄膜用于CdTe太阳电池的制作,获得了10.29%的光电转换效率,初步验证了该制作工艺的可行性。     

Deep level transient spectroscopy investigation of deep levels in CdS/CdTe thin film solar cells with Te:Cu back contact

Deep levels in Cds/CdTe thin film solar cells have a potent influence on the electrical property of these devices. As an essential layer in the solar cell device structure, back contact is believed to induce some deep defects in the CdTe thin film. With the help of deep level transient spectroscopy (DLTS), we study the deep levels in CdS/CdTe thin film solar cells with Te:Cu back contact. One hole trap and one electron trap are observed. The hole trap H1, localized at E_v+0.128~eV, originates from the vacancy of Cd (V_Cd. The electron trap E1, found at E_c-0.178~eV, is considered to be correlated with the interstitial Cu_i⁼ in CdTe.     

近距离升华薄膜装置的研制及特性

详细介绍了近距离升华（CSS）薄膜装置的研制及其特性,并对利用该装置及利用射频溅射沉积的CdTe膜的结构进行了XRD分析。结果表明,CSS方法所得的CdTe膜具有较大的晶粒尺度,结晶效果更好。     

High-temperature conductivity of solid and liquid CdTe

Conductivity of CdTe single crystals fabricated in our laboratory by vertical gradient freeze method was studied at temperatures 400–1200°C. Two clear slopes are seen — 0.7 eV in the solid and 4.6 eV in the liquid. Experimental value of electrical conductivity at the melting point 10 Ω⁻¹ cm⁻¹ was observed. A model explaining the experimental data is suggested.     

半导体CdTe纳米晶的合成及其光学性能

半导体CdTe纳米晶的合成及其光学性能;CdTe;纳米晶;光学性能     

CdTe/CdS量子点的Ⅰ-Ⅱ型结构转变与荧光性质

制备了壳层厚度可以精确控制的CdTe/CdS核壳量子点, 利用紫外-可见吸收光谱、光致发光光谱、透射电镜和时间分辨光谱等技术, 分析了CdS壳层厚度对CdTe量子点的荧光量子产率和光谱结构的影响规律. 发现了不同于CdSe/CdS, CdSe/ZnS, CdTe/ZnS等核壳量子点的荧光峰展宽、大幅度红移以及荧光寿命大幅度增加现象. 根据能带的位置关系, 随着CdS厚度的增加, CdTe从Ⅰ型结构逐渐过渡到Ⅱ型核壳结构. 对于Ⅱ型CdTe/CdS核壳量子点, 不仅存在CdTe核区导带电子与价带空穴间的直接复合, 还存在CdS壳层导带电子与CdTe核价带空穴界面处的间接复合, 发光机制的变化导致荧光峰的展宽、明显红移和荧光寿命的增加. 当壳层过厚时, 壳层表面新引入的缺陷会阻碍荧光寿命和量子产率的进一步提高.     

水溶性量子点荧光探针用于帕珠沙星的含量测定

文章采用荧光光谱和紫外光谱研究了CdTe量子点(CdTe QDs)与广谱抗菌药物帕珠沙星的相互作用。结果表明,随着帕珠沙星浓度的增加,CdTe QDs荧光强度有规律的降低,但通过透射电镜图对QDs及加入帕珠沙星后的QDs进行比较,发现QDs仍然均一单分散,表明反应的作用机理可能是帕珠沙星促使QDs表面键合的有机分子发生变化,在Cd空位表现出的表面缺损上形成了碲氧复合物,致使荧光猝灭。因此该反应可作为一种新颖的快速检测帕珠沙星含量的方法。在一定条件下,帕珠沙星溶液的浓度与量子点荧光强度成线性关系,线性范围为10.0～850 μg·mL-1,相关系数r为0.995 4,检测限(S/N=3)为3.254×10-3 μg·mL-1。药物对量子点的猝灭常数为2.188×104 L·mol-1。应用到冻干粉针剂和氯化钠注射液中帕珠沙星的含量测定,所得结果与标示量一致。该方法较常用检测方法具有简便、快捷、灵敏、线性范围宽的优点,并有望进一步开展发药物体内显像及作用机理的研究。