Influence of pH on luminescence from water-soluble colloidal Mn-doped ZnSe quantum dots capped with different mercaptoacids

Water-soluble ZnSe/ZnS core–shell quantum dots with ZnSe core doped by manganese ions show different luminescence response to pH changes in aqueous solutions depending on the type of solubilizing agents (thioglycolic acid, mercaptoundecanoic acid, sodium mercaptopropylsulfonate). In the case of long-chain mercaptoundecanoic acid only excitonic emission is affected by pH changes. Short-chain thioglycolic acid brings about equal excitonic/Mn emission variations with pH, while mercaptopropylsulfonate-stabilized quantum dots are insensitive to pH. The mechanism discussed here is based on the competition between different relaxation channels for excited excitons in ZnSe: excitonic radiative recombination, energy transfer to Mn ion and the photogenerated electron trapping due to the presence of protonated carboxyl group. ZnSe:Mn/ZnS quantum dots stabilized with long-chain mercaptoacids may be used as a new type of fluorescence ratiometric pH-sensor or indicator.     

Mn掺杂ZnS量子点与孔雀石绿和隐性孔雀石绿的相互作用

研究了Mn掺杂ZnS量子点与孔雀石绿和隐性孔雀石绿的相互作用。首先采用水热法以壳聚糖为基质,利用成核掺杂原理制备量子点,然后分别采用紫外-可见吸收和荧光光谱技术研究了量子点与孔雀石绿和隐性孔雀石绿的相互作用。结果表明,向初始浓度为20 mg·L~(-1)孔雀石绿溶液中加入200 mg·L~(-1)量子点,60 min孔雀石绿的去除率约为82%,量子点可以光催化降解孔雀石绿,其反应过程符合假一级动力学的假设;量子点对隐性孔雀石绿具有荧光猝灭作用,猝灭作用为动态猝灭,相互作用力为氢键和范德华力,吉布斯自由能小于零,量子点与隐性孔雀石绿的相互作用是一个自发的过程。因此,量子点可以用于光催化降解孔雀石绿和快速无毒检测隐性孔雀石绿。     

基于Mn掺杂ZnS量子点-BSA纳米复合材料检测头孢曲松钠

以3-巯基丙酸(MPA)为稳定剂,采用水相合成法合成了具有优良光学性质的Mn掺杂ZnS量子点。该量子点在室温条件下即可发射较强的磷光信号。将量子点与牛血清蛋白(BSA)偶联后,形成了纳米复合材料。由于BSA对量子点表面缺陷进行了有效修复,量子点发出的磷光明显增强。当加入头孢曲松钠后,头孢曲松钠与BSA的相互作用使量子点的磷光被有效猝灭,该磷光猝灭量(△P)与头孢曲松钠的浓度在一定范围内呈良好的线性关系(R=0.99)。量子点与BSA偶联的最佳条件为:pH=7.4,反应温度37 ℃,反应时间40 min,BSA浓度80 mg·L^-1,量子点浓度40 mg·L^-1。反应形成新的生物纳米复合材料,作为头孢曲松钠的磷光探针,其线性范围为0~30 μmol·L^-1,相关系数R=0.99,检出限为0.14 μmol·L^-1,相对标准偏差为1.63%。     

基于CuInS2/ZnS核壳结构量子点的高光效暖白光LED

采用逐步热注射法合成了用于白光LED的CuInS₂/ZnS(CIS/ZnS)核壳结构量子点.通过调整Cu/In的比率, 在CuInS₂(CIS)量子点的基础上, 合成了发射波长在570~650 nm之间可调的CIS/ZnS量子点.与CIS量子点的低量子产率相比, 具有核壳结构的CIS/ZnS量子点的量子产率达到了78%.通过在黄光荧光粉YAG :Ce³⁺表面旋涂CIS/ZnS量子点的方式制备了暖白光LED器件.在工作电流为10 mA时, 暖白光LED的发光效率达到了244.58 lm/W.由于CIS/ZnS量子点的加入, 所制备的白光LED器件的显色指数达到86.7且发光颜色向暖色调发生了转移, 相应的色坐标为(0.340 6, 0.369 0).     

Copper- or manganese-doped ZnS quantum dots as fluorescent probes for detecting folic acid in aqueous media

3-Mercaptopropionic acid-capped core/shell ZnS:Cu/ZnS and ZnS:Mn/ZnS doped quantum dots (QDs) prepared through hydrothermal methods exhibit high photoluminescence intensity as well as good photostability. These water-dispersible nanoparticles exhibit high fluorescence sensitivity to folic acid due to the high affinity of the carboxylate groups and nitrogen atoms of folic acid towards the Zn surface atoms of the doped dots. Quenching of the fluorescence intensity of the QDs allows the detection of folic acid concentrations as low as 11 μM, thus affording a very sensitive system for the sensing of this biologically active molecule in aqueous solution. The possible quenching mechanism is discussed.     

ZnS：Mn/SiO2量子点的表面聚乙烯吡咯烷酮修饰及其应用于海水中铅离子检测

制备了二氧化硅壳层修饰的ZnS：Mn量子点,基于聚乙烯吡咯烷酮（PVP）与二氧化硅表面硅羟基的作用,在纳米复合微粒表面进行了PVP的修饰,得到了在海水中荧光性能及胶体稳定性良好的ZnS：Mn/SiO₂/PVP 量子点。在Pb²⁺对所制备纳米微粒具有荧光猝灭效应的基础上,建立了用ZnS：Mn/SiO₂/PVP 量子点作为荧光探针检测海水中微量铅离子的新方法。研究表明,量子点浓度为10^-3 mol/L时,海水中离子浓度在10~100 μmol/L范围内与ZnS：Mn/SiO₂/PVP量子点荧光猝灭强度呈良好的线性关系,相关系数为0.994 6,检出限为8×10^-7 mol/L。     

Observation of enhanced two-photon absorption in ZnS quantum dots at an ultraviolet wavelength

Two-photon absorption(2PA) in zinc sulphide(ZnS) and Mn2+-doped ZnS quantum dots is reported by the z-scan technique,with nanosecond pulsed laser radiation at 355 nm.The observed values of the 2PA cross section of all the samples are 105 times larger than that of bulk ZnS.     

Manganese Doped Zinc Sulfide Quantum Dots for Detection of Escherichia coli

A novel biocompatible chitosan passivated manganese doped zinc sulfide (Mn doped ZnS) nanophosphor has been synthesized through a simple aqueous precipitation reaction. Upon excitation with ultraviolet light, the quantum dots (QDs) emit an orange luminescence peaking at 590 nm, which is visible to the naked eye. These chitosan coated Mn doped ZnS QDs can have potential applications in bio-labeling, particularly in fluorescence-based imaging. One of the envisioned applications of these QDs is in improving the conventional, organic dye-reliant Fluorescence in situ Hybridization (FISH) technique, a widely used method for microbial detection. Here we demonstrate that the chitosan-capped Mn doped ZnS QDs are suitable for this purpose.     

ZnO/ZnS核-壳量子点的双光子吸收效应

利用飞秒激光Z-扫描与泵浦-探测技术,研究了室温下ZnO/ZnS与ZnO/ZnS/Ag核-壳胶体量子点的双光子吸收效应.研究发现:ZnO基核-壳量子点的本征双光子吸收系数比ZnO体材料增大了3个数量级;测量得到的660 nm处的ZnO/ZnS核-壳量子点双光子吸收截面约为4.3×10^-44 cm⁴·s·photon^-1,比相应的ZnS、ZnSe及 CdS量子点大2个数量级;当ZnO/ZnS核-壳量子点镶嵌了银纳米点时,非线性吸收有所增强.ZnO基复合纳米结构的双光子吸收增强可归因于量子限域与局域场效应.     

ZnS∶Cu-罗丹明B的荧光共振能量转移性质

为了解决现有的基于量子点荧光共振能量转移体系的生物毒性问题,选用无毒的ZnS∶Cu量子点与罗丹明B构建新型荧光共振能量转移体系。通过共沉淀法成功制备了形貌均一的ZnS∶Cu纳米晶量子点。在此基础上,测试了不同掺杂浓度的ZnS∶Cu量子点及罗丹明B的荧光光谱。然后,通过对ZnS∶Cu量子点的表面修饰构建了以ZnS∶Cu量子点为供体、罗丹明B为受体的荧光共振能量转移体系。实验结果表明:ZnS∶2%Cu量子点的发光光谱与罗丹明B的吸收光谱在481 nm处有较大重合,说明构建荧光共振能量转移的最佳铜掺杂摩尔分数为2%。通过计算发现以ZnS∶2%Cu量子点为供体、罗丹明B为受体的荧光共振能量转移体系的能量转移效率为25.8%。进一步实验结果表明,罗丹明B浓度也能够影响能量转移。     

Effect of the Semiconductor Quantum Dot Shell Structure on Fluorescence Quenching by Acridine Ligand

The main line of research in cancer treatment is the development of methods for early diagnosis and targeted drug delivery to cancer cells. Fluorescent semiconductor core/shell nanocrystals of quantum dots (e.g., CdSe/ZnS) conjugated with an anticancer drug, e.g., an acridine derivative, allow real-time tracking and control of the process of the drug delivery to tumors. However, linking of acridine derivatives to a quantum dot can be accompanied by quantum dot fluorescence quenching caused by electron transfer from the quantum dot to the organic molecule. In this work, it has been shown that the structure of the shell of the quantum dot plays the decisive role in the process of photoinduced charge transfer from the quantum dot to the acridine ligand, which is responsible for fluorescence quenching. It has been shown that multicomponent ZnS/CdS/ZnS shells of CdSe cores of quantum dots, which have a relatively small thickness, make it possible to significantly suppress a decrease in the quantum yield of fluorescence of quantum dots as compared to both the classical ZnS thin shell and superthick shells of the same composition. Thus, core/multicomponent shell CdSe/ZnS/CdS/ZnS quantum dots can be used as optimal fluorescent probes for the development of systems for diagnosis and treatment of cancer with the use of anticancer compounds based on acridine derivatives.     

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。     

Highly luminescent (ZnSe)ZnS core-shell quantum dots for blue to UV emission: synthesis and characterization

We synthesized nearly monodisperse bare ZnSe nanocrystallites having luminescence which ranges in wavelength from 340 to 430 nm via nucleation due to supersaturation and growth followed by size selective precipitation. Bare ZnSe dots' outermost surface is passivated with organic HDA/TOP. In order to enhance the radiative emission from the semiconductor nanocrystals, we capped the bare ZnSe quantum dots with ZnS semiconductor materials of a wider band gap and 5% of lattice mismatch and produced highly luminescent core-shell (ZnSe)ZnS quantum dots. The core-shell (ZnSe)ZnS nanocrystals show 20 times or more as greatly enhanced luminescence quantum yields as those of bare ZnSe nanocrystals. The ZnSe bare dots and the (ZnSe)ZnS core-shell dots have cubic zinc blende structures as expected from the bulk structure. The observed shapes of bare ZnSe and core-shell (ZnSe)ZnS dots are nearly spherical or ellipsoidal with the aspect ratios of 1.2 and 1.4, respectively. They are not faceted.     

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ln P 0/P=0.01758 C(DTC)+0.01351(R 2=0.999),检出限为0.0097μmol·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残留检测具有良好重复性和稳定性,可用于蜂蜜中TCs残留的快速、高灵敏检测。     

核壳型ZnS∶Cu/ZnS量子点的制备及发光性质

本文采用水相合成方法制备了ZnS∶Cu量子点并进行了ZnS壳层修饰,研究了壳层厚度对ZnS∶Cu量子点光学性质的影响,采用TEM、XRD、PL、PLE和UV-Vis等测试方法对其进行了表征。实验结果表明,合成的ZnS∶Cu/ZnS量子点为立方闪锌矿,尺寸分布均匀呈球形,分散性良好,经过壳层修饰平均粒径由2 nm增加到3.2 nm。随着ZnS壳与ZnS核量的比的增加,量子点的PLE激发峰位置和UV-Vis吸收谱线出现红移,也说明了量子点的尺寸增大,证明ZnS在ZnS∶Cu量子点的表面生长,形成了核壳结构的ZnS∶Cu/ZnS量子点。随着壳层增厚,量子点与铜离子发光中心相关的发射峰强度先增大后减小,当壳核比n_s/n_c=2.5时,发光强度达到最大。     

基于InP/ZnS核壳结构量子点的色转换层设计及制作

提出了采用环境友好型InP/ZnS核壳结构量子点材料制备匹配蓝光Micro-LED阵列的量子点色转换层以实现Micro-LED阵列器件全彩化的技术方案。通过采用倒置式量子点色转换层方案,实现了InP/ZnS量子点材料和Micro-LED阵列的非直接接触,从而可以缓解LED中热量聚集导致的量子点材料发光主波长偏移、半峰宽展宽以及发光效率衰减等问题。量子点色转换层中内嵌PDMS聚合物柔性膜层,可以消除咖啡环效应,同时,色转换层中内嵌飞秒激光图案化处理的500 nm长波通滤光膜层,可以抑制蓝光从非蓝色像素单元出射。最后,实验制备了像素单元中心间距90μm的16×16 InP/ZnS量子点色转换层。该设计可以实现基于蓝光Micro-LED阵列的全彩色Micro-LED显示器件的制备,并且该制备方法可以降低全彩色Micro-LED阵列显示器件的制备成本。     

ZnS:Ag/CdS: a new family of color-tunable quantum dots

ZnS:Ag/CdS quantum dots (QDs) have been synthesized by a reverse micelle process under ambient environment. Excited by 350?nm, the emission peak of ZnS:Ag/CdS QDs changes from 425 to 625?nm with increasing the thickness of CdS shells. Although the quantum yields of QDs decrease with CdS shells thickening, the luminescent brightness remains stable throughout. Compared with the traditional color-tunable CdSe QDs, the synthesis of ZnS:Ag/CdS QDs is less toxic and more economic. Therefore, this synthesis process can be regarded as an efficient way to fabricate a series of luminescent nanostructures for a variety of applications.     

Intermediate intensity levels during the emission intermittency of single CdSe/ZnS quantum dots

We report on an intermediate intensity level in the emission intermittency of single CdSe/ZnS core shell quantum dots, which has been overlooked in previous experiments most likely due to its low quantum efficiency. The intermediate intensity level is observed in CdSe/ZnS quantum dots of large diameter (about 5 nm diameter) and appears to be independent of the general dark state power law dynamics. The dim emission periods are found to be exponentially distributed and thus correspond to similar findings in CdSe/CdS quantum dots, where their existence has been interpreted in terms of the emission of a positively charged trion.     

CdSe/ZnS量子点在倏逝波光纤pH传感中的应用

将新型量子点荧光传感技术与光纤倏逝波传感技术相结合,发展了一种基于量子点荧光效应并结合倏逝波传导进行溶液酸碱度检测的新型传感技术,具有灵敏度高、检测速度快、便于微环境检测、可实现远程探测、实时监测和原位分析等特点。详细介绍了用于倏逝波传感的锥柱组合型光纤荧光探头的制备方法,量子点在光纤探头表面的修饰流程,光谱与强度两种光纤pH传感平台的建立,并分别从响应范围、线性度、重复性和稳定性等方面对CdSe/ZnS量子点应用于光纤pH传感进行了评价。结果表明,在pH值为2~12的范围内,CdSe/ZnS量子点的荧光光谱信号的峰位在强酸和强碱的情况下都会产生红移,且红移量随pH值的变化呈线性关系,其量子点荧光强度信号随pH值的减小呈线性降低关系,通过在强酸和强碱下交替测试的实验表明其具有较好的重复性,利用荧光强度传感平台进行实时监测的实验表明其具有较好的稳定性。因此,将CdSe/ZnS量子点用于倏逝波光纤pH传感具有可行性,在生物化学、环境监测、医学临床、食品安全等领域的pH值测量方面有着广泛的应用前景。     

Effects of ZnS:Mn/AlN multilayer structure on luminescent properties of nanostructured thin-film EL device

Effects of ZnS:Mn/AlN multilayer structure on luminescent properties of nanostructured (NS) thin-film electroluminescent (TFEL) device of which emission layer is a multilayer composed with ZnS:Mn layers and 0.7-nm-thick AlN interlayers were studied. The bandgap widening and the increased PL efficiency of Mn²⁺ 3d-3d transitions with a decrease in the ZnS:Mn single-layer thickness down to 5 nm were observed, which is ascribed to quantum confinement effects. Meanwhile, the multilayer with 2-nm-thick ZnS:Mn single-layers shows a drop of PL efficiency, indicating the presence of defective region just on AlN. The tendency of the luminous efficiency of the NS-TFEL device against the ZnS:Mn single-layer thickness is similar to the tendency found in the PL efficiency, indicating the importance of the ZnS:Mn/AlN interface for the device performance.