CdTe,核 壳型CdTe/CdS及CdTe/ZnS量子点的合成及表征

在水相中制备了半导体CdTe纳米晶,核 壳型CdTe/CdS和CdTe/ZnS纳米晶（即量子点;QDs）.利用扫描隧道显微镜（STM）和荧光光谱(FS)对合成的纳米晶量子点进行了研究,并且根据FS的数据进行了量子效率的计算.STM的结果表明合成的量子点直径约为3 nm并且分布良好.为了提高量子效率,对Cd2+浓度和Cd2+∶S2－比例等反应条件进行了研究,结果表明随着回流时间的增加,核 壳型量子点CdTe/CdS的量子效率总体上呈下降趋势.CdTe/CdS在pH8.5,Cd2+∶S2－=10∶1（摩尔比）时可获得80.0%的最大量子效率.同时制备了核 壳型量子点CdTe/ZnS,其最大发射波长由551 nm（CdTe）红移到635 nm（CdTe/ZnS）表明量子点的尺寸在增长,但是量子效率下降到14.4%. 当前研究的量子点可适用于生物标记,生物成像,以及基于共振能量转移的生物传感研究.     

锰掺杂硫化锌量子点磷光探针对蜂蜜中四环素类抗生素残留的高灵敏检测

通过水合法合成了L-半胱氨酸修饰的锰掺杂硫化锌量子点(Mn∶ZnS QDs)。利用四环素类抗生素(Tetracyclines,TCs)对锰掺杂硫化锌量子点磷光激发光的內滤效应建立蜂蜜中TCs残留的快速、高灵敏检测方法。TCs在Mn∶ZnS QDs磷光最佳激发波长289 nm处有较强的紫外吸收,当Mn∶ZnS QDs体系中存在TCs时,激发光一定程度地被TCs吸收,磷光信号减弱。本研究以强力霉素(Doxycycline,DTC)为代表,建立Mn∶ZnS QDs磷光信号与DTC浓度的线性关系,进而实现对DTC的定量检测。结果表明,在优化条件下,Mn∶ZnS QDs磷光信号减小值的自然对数与DTC浓度在0.05～150μmol·L^-1范围内呈良好的线性关系,线性方程为lnP₀/P=0.01758C(DTC)+0.01351(R²=0.999),检出限为0.009 7μmol·L^-1。同时,对实际样品蜂蜜做了加标回收率实验,回收率为92.4%～110%。本研究建立的Mn∶ZnS QDs磷光探针用于TCs残留...     

Surface Molecular Imprinting on Silica-Coated CdTe Quantum Dots for Selective and Sensitive Fluorescence Detection of p-aminophenol in Water

In this paper, a selective and sensitive sensor for the determination of p-aminophenol (PAP) was developed by grafting molecularly imprinted polymers (MIPs) on the surface of silica-coated CdTe quantum dots (CdTe@SiO₂@MIPs). The obtained CdTe@SiO₂@MIPs were characterized by X-ray powder diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy and fluorescence spectroscopy. The fluorescence intensity of CdTe@SiO₂@MIPs was more strongly quenched by PAP than that of the structural analogues of PAP. Under the optimal conditions, the fluorescence intensity of the CdTe@SiO₂@MIPs decreased sensitively with the increase of PAP concentration in the range of 0.05–50 μM. The limit of detection was 0.02 μM (3σ/K _sv). The sensor was successfully used to determine PAP in tap and lake water samples, and the average recoveries of PAP at various spiking levels ranged from 97.33 % to 103.3 % with relative standard deviations below 20 %.     

基于MPA包覆的Mn掺杂ZnS量子点/米托蒽醌复合体系对DNA的检测

利用3-羟基丙酸(MPA)包覆的Mn掺杂Zn S量子点与盐酸米托蒽醌(MTX)构建了一种可简单测定DNA的磷光复合体系。该体系以MTX作为良好的电子受体,通过光诱导电子转移(PIET)原理猝灭Mn掺杂Zn S量子点的室温磷光(RTP)。当体系中加入DNA后,DNA通过静电和嵌插作用与MTX结合,形成更稳定的复合物,并使MTX从Mn掺杂Zn S量子点表面脱离,Mn掺杂Zn S量子点的RTP恢复,从而实现了对DNA的痕量检测。该体系检测DNA的线性范围为0.1~20 mg·L~(-1),检出限为0.07 mg·L~(-1)。该方法可有效避免其他共存物质的干扰并可应用于实际生物样品中DNA含量的快捷测定。     

Interaction of Folic Acid with Mn2+ Doped CdTe/ZnS Quantum Dots: In Situ Detection of Folic Acid

To utilize the nanomaterials as an effective carrier for the drug delivery applications, it is important to study the interaction between nanomaterials and drug or biomolecules. In this study GSH functionalized Mn²⁺-doped CdTe/ZnS QDs has been utilized as a model nanomaterial due to its high luminescence property. Folic acid (FA) gradually quenches the FL of GSH functionalized Mn²⁺???doped CdTe/ZnS QDs. The Stern-Volmer quenching constant (K_sv), binding constant (K_s) and effective quenching constant (Ka) for the FA-QDs system is calculated to be 1.32?×?10⁵ M^?1, 1.92?×?10⁵ and 0.27?×?10⁵ M^?1, respectively under optimized condition (Temp. 300 K, pH 8.0, incubation time 40 min.). The effects of temperature, pH, and incubation time on FA-QDs system have also been studied. Statistical analysis of the quenched FL intensity versus FA concentration revealed a linear range from 1?×?10^?7 to 5.0?×?10^?5 for FA detection. The LOD of the current nano-sensor for FA was calculated to be 0.2 μM. The effect of common interfering metal ions and other relevant biomolecules on the detection of FA (12.0 μM) have also been investigated. L-cysteine and glutathione displayed moderate effect on FA detection. Similarly, the common metal ions (Na⁺, K⁺, Ca²⁺ and Mg²⁺) produced minute interference while Zn²⁺ Cu²⁺ and Fe³⁺ exert moderate interference. Toxic metal ions (Hg²⁺ and Pb²⁺) produced severe interferences in FA detection.

Graphical abstract

GSH-Mn²⁺ CdTe/ZnS QDs based Fluorescence Nanosensor for Folic acid

     

Highly Sensitive and Selective Detection of Amoxicillin Using Carbon Quantum Dots Derived from Beet

In the present work, we synthesized the carbon quantum dots (CQDs) by one step hydrothermal method using the dried beet powder as the carbon source without additional chemical reagents and functionalization. The as-prepared CQDs are quasi-spherical carbon nanoparticles with diameters of 4–8 nm as well as surface functional groups such as carboxyl and hydroxyl groups, and exhibit good water-solubility, biocompatibility, and strong fluorescence. It is confirmed that amoxicillin (AMO) could enhance the fluorescent intensity of CQDs, the I/I₀ showed a linear correlation between the intensity of fluorescence and the concentration of AMO in a broad range. These superior properties render a potential application of the CQDs in biomedical.     

CdSe/CdS/ZnS量子点光纤的增益研究

采用油相法合成了CdSe/CdS/ZnS量子点,相对于CdSe量子点,其吸收光谱、发射光谱均发生了红移。利用COMSOL Multiphysics软件模拟CdSe/CdS/ZnS量子点光纤和甲苯光纤的电场分布,结果表明CdSe/CdS/ZnS量子点光纤的电场强度高于甲苯光纤。采用中心波长为532 nm的稳态半导体激光器作为光源,对甲苯光纤、CdSe/ZnS量子点光纤、CdSe/CdS/ZnS量子点光纤进行电压信号测试,发现CdSe/ZnS量子点光纤和CdSe/CdS/ZnS量子点光纤的电压信号值相对于甲苯光纤电压信号值分别增强了6.28 mV和18.43 mV,表明双壳型量子点光纤的增益高于单壳型量子点。     

Fluorescent Recognition of Potassium and Calcium Ions Using Functionalised CdSe / ZnS Quantum Dots

Schiff base receptor 1a has been synthesised and attached to the surface of preformed CdSe/ZnS Quantum Dots (QDs) to form QD-conjugate 2a. While 1a was determined to be selective for Mg²⁺, 2a demonstrated selectivity for both K⁺ and Ca²⁺ when tested against a range of physiologically and environmentally relevant cations by changes in the fluorescence spectra. Thus, the nanoparticle surface functions as a scaffold for the organisation of receptors enabling semi-selective binding. The fluorescence response was shown to be linear between 15–50?μM for K⁺ and 2–35?μM for Ca²⁺. It was also demonstrated that 2a could measure both K⁺ and / or Ca²⁺ in solutions containing both ions.     

Interaction of CdTe Quantum Dots with 2,2-Diphenyl-1-Picrylhydrazyl Free Radical: A Spectroscopic, Fluorimetric and Kinetic Study

The interaction of 2,2-diphenyl-1-picrylhydrazyl (DPPH^●) free radical with thiol-capped CdTe quantum dots (QDs) has been studied by UV–vis spectroscopy, steady state and time resolved fluorescence measurements. Addition of DPPH^● radical to CdTe QDs resulted in fluorescence quenching. The interaction occurs through static quenching as this was confirmed by fluorescence lifetime measurements. Time course absorption studies indicates that DPPH^● may be reduced by interaction with QDs to the substituted hydrazine form (2,2-diphenyl-1-picrylhydrazine) DPPH-H. The mechanism of fluorescence quenching of CdTe QDs by DPPH^● is proposed.     

Effect of Electrical Field on Colloidal CdSe/ZnS Quantum Dots

We fabricate the hybrid films of colloidal CdSe/ZnS quantum dots (QDs) and poly(9-vinylcarbazole) (PVK) sandwiched between two electrodes. The voltage and temperature dependences of the electroluminescence (EL) are measured. The quantum-confined Stark effect of colloidal QDs is clearly observed. To explore the mechanism in the QD EL, hybrid films are fabricated with different concentrations of colloidal QDs. Electrons and holes are proposed to be separately transported in QDs and PVK, respectively.     

CdSe/ZnSe/ZnS多壳层结构量子点的制备与表征

展示了一种简捷的多壳层量子点合成路线。在含有过量Se源的CdSe体系中直接注入Zn源,"一步法"合成了CdSe/ZnSe量子点;进一步以CdSe/ZnSe为"核",表面外延生长ZnS壳层制备了核/壳/壳结构CdSe/ZnSe/ZnS量子点。相对于以往报道的多壳层结构量子点的制备方法,该方法通过减少壳层的生长步骤有效地简化了实验操作,缩短了实验周期,同时减少对原料的损耗。对量子点进行高温退火处理,能够大幅提高CdSe/ZnSe/ZnS量子点的发光量子产率。透射电镜、XRD以及光谱研究表明:所制备的量子点接近球形,核与壳层纳米晶均为闪锌矿结构,最终获得的CdSe/ZnSe/ZnS量子点的光致发光量子产率达到53％。为了实现量子点的表面生物功能化,通过巯基酸进行了表面配体交换修饰,使量子点表面具有水溶性的羧基功能团,并且能够维持较高的光致发光量子产率。     

Study on the Interaction of the CpG Alternating DNA with CdTe Quantum Dots

A novel sensitive method for detection of DNA methylation was developed with thioglycollic acid (TGA)-capped CdTe quantum dots (QDs) as fluorescence probes. Recognition of methylated DNA sites would be useful strategy due to the important roles of methylation in disease occurrence and developmental processes. DNA methylation occurs most often at cytosine-guanine sites (CpG dinucleotides) of gene promoters. The QDs significantly interacted with hybridized unmethylated and methylated DNA. The interaction of CpG rich methylated and unmethylated DNA hybrid with quantum dots as an optical probe has been investigated by fluorescence spectroscopy and electrophoresis assay. The fluorescence intensity of QDs was highly dependent to unmethylated and methylated DNA. Specific site of CpG islands of Adenomatous polyposis coli (APC), a well-studied tumor suppressor gene, was used as the detection target. Under optimum conditions, upon the addition of unmethylated dsDNA, the fluorescence intensity increased in linear range from 1.0?×?10^??10 to 1.0?×?10^??6M with detection limit of 6.2?×?10^??11 M and on the other hand, the intensity of QDs showed no changes with addition of methylated dsDNA. We also demonstrated that the unmethylated and methylated DNA and QDs complexes showed different mobility in electrophoresis assay. This easy and reliable method could distinguish between methylated and unmethylated DNA sequences.     

ZnCuInS/ZnSe/ZnS量子点发光光谱特性的研究

ZnCuInS/ZnSe/ZnS量子点是一种无毒,无重金属的“绿色”半导体纳米材料。在研究中,制备了三种尺寸的ZnCuInS/ZnSe/ZnS核壳量子点,其直径分别为3.3,2.7,2.3 nm。通过测量不同尺寸的ZnCuInS/ZnSe/ZnS量子点的光致发光光谱,其发射峰值波长随尺寸的减小而蓝移。其吸收峰值波长和发射峰值波长分别是510,611(3.3 nm),483,583(2.7 nm)以及447,545 nm(2.3 nm)。ZnCuInS/ZnSe/ZnS量子点具有显著的尺寸依赖效应。ZnCuInS/ZnSe/ZnS量子点的斯托克斯位移分别为398 meV(3.3 nm),436 meV(2.7 nm)以及498 meV(2.3 nm),这样大的斯托克斯位移证明,ZnCuInS/ZnSe/ZnS量子点的发光机制与缺陷能级有关。同时,对直径为3.3 nm的ZnCuInS/ZnSe/ZnS量子点进行了温度依赖的光致发光光谱的测量,当温度为15～90 ℃时,该量子点发射峰值波长随温度的升高而红移,发光强度随温度的升高而降低,说明ZnCuInS/ZnSe/ZnS量子点是以导带能级与缺陷能级之间跃迁为主的复合发光。     

不同巯基试剂修饰的CdTe量子点与BSA相互作用研究

修饰试剂对量子点的合成、性质具有重要的影响,但目前有关修饰试剂对量子点与蛋白质间相互作用的影响尚不清楚。采用紫外-可见吸收光谱、荧光光谱及红外光谱研究了3种巯基化合物(巯基乙酸,TGA;L-半胱氨酸,L-Cys;还原型谷胱甘肽,GSH)修饰的CdTe量子点与牛血清白蛋白(BSA)的相互作用。通过Stern-Volmer方程对数据进行了分析,得到了不同CdTe量子点与BSA相互作用过程的ΔHθ,ΔGθ和ΔSθ,并比较了CdTe量子点的不同修饰剂对BSA荧光猝灭的影响。研究结果表明,3种修饰试剂包覆的CdTe量子点与BSA的相互作用均为静态猝灭过程,猝灭常数KSV(L-Cys)KSV(TGA)≈KSV(GSH);TGA和L-Cys修饰的CdTe量子点与BSA的结合力主要为疏水作用力,而GSH修饰的量子点与其结合力既有氢键作用力又有疏水作用力;这些结果说明量子点与BSA的作用过程与量子点表面修饰试剂的类型有关。     

HgTe/CdS/ZnS多壳层量子点的制备与表征

采用一种简单的方法合成HgTe/CdS/ZnS多壳层量子点。首先,以1-硫代甘油为稳定剂,在水相溶液中制备出HgTe核量子点;然后,采用外延生长法依次在HgTe核量子点表面包覆CdS和ZnS壳层,合成出最终具有稳定近红外发光的HgTe/CdS/ZnS多壳层量子点。该合成方法仅需3个步骤,具有操作简单、成本低廉的优点。实验结果显示,当反应温度为90 ℃、反应溶液pH为11.0、反应加热回流时间为4 min时,HgTe/CdS/ZnS多壳层量子点具有最高荧光量子产率36%。     

ZnCuInS/ZnS量子点光致发光温度依赖性研究

ZnCuInS/ZnS量子点是一种无重金属"绿色"半导体纳米材料。制备出了直径为2.9nm的ZnCuInS/ZnS核壳量子点。从ZnCuInS/ZnS量子点的吸收及光致发光光谱中可以看到,量子点的斯托克斯位移为410meV。这样大的斯托克斯位移表明,ZnCuInS/ZnS量子点的复合机制与缺陷能级有关。研究并计算了在辐射及非辐射驰豫过程的(Huang-Rhys)因子及平均声子能量。结果表明在50~373K范围内,能量带隙的变化以及光致发光光谱的增宽是分别由光从能带边缘向缺陷能级跃迁及载流子声子耦合导致的。     

ZnCuInS/ZnS量子点与Poly-TPD补偿发光光谱的研究

ZnCuInS/ZnS量子点是一种无重金属、“绿色”半导体纳米材料。在研究中,制备出尺寸为3.2 nm的ZnCuInS/ZnS核壳量子点,并说明它是施主-受主对复合发光。通过测量ZnCuInS/ZnS量子点的光致发光光谱,其发射峰值波长为620 nm、半宽度是95 nm的红光。同时,还制备出Poly-TPD有机薄膜,其发光光谱是峰值波长为480 nm的蓝光。所以,ZnCuInS/ZnS量子点和Poly-TPD发光颜色具有互补性。在ZnCuInS/ZnS量子点薄膜层上包覆一层poly-TPD薄膜后,二者发光颜色互补。在恰当的偏置电压下,可以得到较好的白光光谱。计算表明,其色坐标是(0.336,0.339),颜色指数是92。     

单质碘对水溶性CdTe量子点的荧光猝灭研究

合成了不同尺寸的、巯基丙酸和半胱氨酸修饰的水溶性CdTe量子点,并研究了I2与CdTe量子点的相互作用,实验发现I2能够明显猝灭CdTe量子点的荧光,且猝灭程度与量子点的修饰剂有关,没有表现出明显的尺寸依赖效应。