Host-molecule-coated quantum dots as fluorescent sensors

“Host” molecules, containing a binding site that is highly specific for an analyte “guest,” are used as sensors to register analyte binding through a variety of mechanisms such as colorimetric, fluorescent, or electrochemical signals. There is increasing interest in the host–guest chemistry on the surface of quantum dots (QDs) and in the changes that it produces in the luminescent properties of QDs. The bulk of this study focuses on those QDs with bound host molecules (crown ether, cyclodextrin, calixarene, and porphyrin) and the selectivity they display toward metal ions and small organic molecules.     

FRET-based modified graphene quantum dots for direct trypsin quantification in urine

A versatile nanoprobe was developed for trypsin quantification with fluorescence resonance energy transfer (FRET). Here, fluorescence graphene quantum dot is utilized as a donor while a well-designed coumarin derivative, CMR2, as an acceptor. Moreover, bovine serum albumin (BSA), as a protein model, is not only served as a linker for the FRET pair, but also a fluorescence enhancer of the quantum dots and CMR2. In the presence of trypsin, the FRET system would be destroyed when the BSA is digested by trypsin. Thus, the emission peak of the donor is regenerated and the ratio of emission peak of donor/emission peak of acceptor increased. By the ratiometric measurement of these two emission peaks, trypsin content could be determined. The detection limit of trypsin was found to be 0.7 μg/mL, which is 0.008-fold of the average trypsin level in acute pancreatitis patient's urine suggesting a high potential for fast and low cost clinical screening.     

Synthesis of surface-modified quantum dots

The review discusses the main methods used to obtain surface-modified quantum dots, specifically silicon, heavy metal chalcogenide and pnictide semiconductor nanoparticles. Examples of transformation processes of the grafted layer are considered. The importance of surface modification of A^IIB^VI- and A^IIIB^V-type semiconductor nanoparticles for the practical application of quantum dots is shown. It was determined that the most promising areas of their practical application are biology, medicine, and pharmacology. Special attention is paid to the hydrophilization of quantum dots, because only these materials can be used in biomedical applications. Modification of the quantum dot surface with amino acids is considered.

     

Microparticle ratiometric oxygen sensors utilizing near-infrared emitting quantum dots

Luminescent sensors incorporating two luminophores, an indicator and a reference, offer many advantages over intensity measurements from sensors made with one indicator dye. Quantum dots have yet to be widely employed as insensitive reference luminophores in such systems. This work describes the use of near-infrared emitting quantum dots in conjunction with a long-lifetime platinum(II) porphyrin phosphor in a microsphere-based, ratiometric oxygen sensor. The process for self-assembly of the nanocomposite system was developed, and the response and photostability of the prototypes were investigated. Results indicate the sensors possess excellent sensitivity (K(SV) = 0.00826 μM(-1)) at oxygen concentrations below 300 μM and were resistant to photobleaching. The sensor luminophores displayed minimal spectral overlap and little interference from excitation light, preventing the need for optical filters. A reversible photoenhancement of the quantum dot signal was also observed when exposed for extended periods of time. This work demonstrates the advantages of incorporating long-wavelength quantum dots into ratiometric intensity sensing schemes and highlights some key limitations that must be considered in their use.     

Highly sensitive FRET-based fluorescence immunoassay for aflatoxin B1 using cadmium telluride quantum dots

We report on a competitive immunoassay for the determination of aflatoxin B1 using fluorescence resonance energy transfer (FRET) from anti-aflatoxin B1 antibody (immobilized on the shell of CdTe quantum dots) to Rhodamine 123 (Rho 123-labeled aflatoxin B1 bound to albumin). The highly specific immunoreaction between the antibody against aflatoxin B1 on the QDs and the labeled-aflatoxin B1 brings the Rho 123 fluorophore (acting as the acceptor) and the QDs (acting as the donor) in close spatial proximity and causes FRET to occur upon photoexcitation of the QDs. In the absence of unlabeled aflatoxin B1, the antigen-antibody complex is stable, and strong emission resulting from the FRET from QDs to labeled aflatoxin B1 is observed. In the presence of aflatoxin B1, it will compete with the labeled aflatoxin B1-albumin complex for binding to the antibody-QDs conjugate so that FRET will be increasingly suppressed. The reduction in the fluorescence intensity of the acceptor correlates well with the concentration of aflatoxin B1. The feasibility of the method was established by the detection of aflatoxin B1 in spiked human serum. There is a linear relationship between the increased fluorescence intensity of Rho 123 with increasing concentration of aflatoxin B1 in spike human serum, over the range of 0.1–0.6 μmol·mL^?1. The limit of detection is 2?×?10^?11 M. This homogeneous competitive detection scheme is simple, rapid and efficient, and does not require excessive washing and separation steps.

Synthesis of carbohydrate-conjugated nanoparticles and quantum dots

Nanoparticle-based probes are emerging as alternatives to molecular probes due to their various advantages, such as bright and tunable optical property, enhanced chemical and photochemical stability, and ease of introduction of multifunctionality. This work presents a simple and general approach for functionalizing various nanoparticle systems for use as glycobiological probes. Silica-coated nanoparticles of Ag, Fe3O4, and ZnS-CdSe were synthesized and functionalized with dextran. The resulting 10-40-nm-sized particles were robust, water-soluble, colloidally stable, and biochemically active.     

双量子点纳米复合物NO比率荧光探针的合成与应用

通过静电吸附作用,合成了CdSe@SiO_2-CdTe双量子点的纳米复合物.一氧化氮(NO)与CdTe量子点表面Cd离子结合形成Cd-NO复合物,引起CdTe量子点荧光猝灭,而不影响CdSe量子点的荧光.当NO浓度在0.1~2.2μmol/L之间变化时,该探针荧光强度比值I_(603)/I_(532)符合线性关系(R=-0.995 4),从而实现对NO的定量检测.     

CdTe/CdSe核壳量子点的合成及其在指纹显现中的应用

以CdCl2和Te粉为原料,在水相中合成了CdTe量子点核;通过外延生长在CdTe量子点核上包覆一层CdSe量子点,得到具有良好荧光性能的CdTe/CdSe核壳量子点;采用X射线衍射仪、透射电镜、高分辨透射电镜分析了不同反应条件下合成的CdTe/CdSe核壳量子点的晶体结构和微观结构,并对其进行了荧光光谱等测试和指纹显现分析.结果表明,合成的CdTe和CdTe/CdSe量子点粒径在3～5nm之间,粒径分布窄,水分散性良好;可以通过控制反应时间和Te/Se比等得到在500～700nm显示荧光发射峰的CdTe/CdSe核壳量子点.此外,核壳CdTe/CdSe量子点可以有效地和指纹物质结合,可应用于对铝合金油潜指纹的鉴别.     

Synthesis of L-tyrosine-capped ZnSe quantum dots and its application to hypochlorite determination in water

In this study, a new sensitised spectrofluorometric method was presented as a probe sensor for hypochlorite analysis in oral and tap water samples. By capping L-tyrosine (Tyr) on ZnSe nanoparticles, stable quantum dots (QDs) were obtained. In comparison with Tyr, the fluorescence (FL) emission of Tyr-capped ZnSe is enhanced and shifted to greater wavelength, which causes to enhance the sensitivity for the determination of hypochlorite. Based on the FL quenching of the Tyr-capped ZnSe QDs, hypochlorite concentration was detected at buffering pH of 7 in the range of 5.15 × 10^?5?2.57 × 10^?2 g L^?1. Relative standard deviation and detection limit were found to be 0.83% and 2.06 × 10^?5 g L^?1, respectively. In comparison with the other methods of hypochlorite determination, this method is simple, fast and inexpensive, with low sample volume consumption. It also exhibits a good selectivity.     

水溶性InP/ZnS量子点的合成及其在指纹显现中的应用

以磷化锌、氯化铟为原料,以十二烷胺为溶剂,在150～200℃下合成了InP量子点,通过相转移和紫外光照得到了巯基乙酸修饰的水溶性InP/ZnS量子点.利用X射线衍射仪、透射电镜、高分辨透射电镜、荧光光谱仪等分析了不同温度下合成的量子点的粒径、形貌、荧光性能及指纹显现效果.结果表明,合成的InP和InP/ZnS量子点为球...     

Synthesis of cysteamine-coated CdTe quantum dots and its application in mercury (II) detection

High-quality cysteamine-coated CdTe quantum dots (CA-CdTe QDs) were successfully synthesized in aqueous phase by a facile one-pot method. Through hydroxylamine hydrochloride-promoted kinetic growth strategy, water-soluble CA-CdTe QDs could be obtained conveniently in a conical flask by a stepwise addition of raw materials. The photoluminescence quantum yield (PL QY) of the obtained QDs reached 9.2% at the emission peak of 520 nm. The optical property and the morphology of the QDs were characterized by UV–vis absorption spectra, photoluminescence spectra (PL) and transmission electron microscopy (TEM) respectively. Furthermore, the fluorescence of the resultant QDs was quenched by copper (II) (Cu²⁺) and mercury (II) (Hg²⁺) meanwhile. It is worthy of note that to separately detect Hg²⁺, cyanide ion could be used to eliminate the interference of Cu²⁺. Under the optimal conditions, the response was linearly proportional to the logarithm of Hg²⁺ concentration over the range of 0.08–3.33 μM with a limit of detection (LOD) of 0.07 μM.     

柠檬酸盐稳定的水溶性CdSe量子点的合成及表征

以柠檬酸三钠为稳定剂在水溶液中合成了水溶性CdSe量子点,用X射线粉末衍射、透射电镜、紫外-可见吸收光谱和荧光发射光谱对CdSe量子点的结构、形貌及其荧光性质进行了表征.结果表明合成的CdSe量子点为立方闪锌矿结构,呈球形,分散性良好,平均尺寸约为2.6nm,具有窄且对称的荧光发射光谱,半峰宽为45nm.     

Synthesis and surface photochemistry of graphitized carbon quantum dots

Graphitized carbon quantum dots (CQDs) were synthesized by a simple hydrothermal process with cetyltrimethylammonium bromide (CTAB) as the starting material and nitric acid as surface oxidant. The photoluminescent quantum yield (QY) of CQDs could be greatly enhanced through surface esterification with glycol. Based on the structure characterization, we proposed that the CQDs consisted of the stack of graphene sheets sized several nanometers and their excitation-dependent photoluminescence (PL) should be attributed to the n→π* transition of CO bond of surface carboxylic groups. And the PL of CQDs was obviously enhanced by the esterification of carboxylic groups, possibly due to the increase of the molecular coplanarity or the rigidity.     

量子点的制备及应用研究进展

综述了量子点的制备方法以及在分析检测、生物、药学、光电器材、指纹显现等领域的应用.指出量子点是一种新型的荧光纳米材料,因其具有独特的光电性质而引起了广泛的关注;并就它的发展方向及应用前景进行了展望.     

Synthesis and structure modeling of ZnS based quantum dots

Quantum dots (QDs) based on zinc sulfide are synthesized by a microwave method in an aqueous medium using dioctyl sodium sulfosuccinate (DS) or 4,4′-bipyridine (BP). Based on the analysis of X-ray diffraction profiles the conclusion is drawn that QDs obtained have a structure of cubic zinc blende with an average particle size of 5.6 nm for the ZnS_DS sample and 4.8 nm for ZnS_BP. Transmission electron microscopy images show the presence of spherical aggregates of particles only for ZnS_DS. FTIR data indicate the presence of sulfate ions in both samples; DS remains in the sample, facilitating the QD agglomeration, while BP is effectively washed out. From the optical diffuse reflectance spectra the band gap is estimated, which turns out to be larger than the expected one due to the presence of elemental sulfur in the samples and partial oxidation of the QD surface. The QD structure based on ZnS particles is also modeled in the work. The possibility to employ X-ray absorption near-edge spectroscopy for the verification of atomic structural parameters around zinc sites in QDs based on zinc sulfide is demonstrated.     

高量子产率水溶性CdTe量子点的制备与表征

以巯基乙酸(HSCH2 COOH,TGA)为稳定剂,在水相中合成高量子产率CdTe量子点(QDs),产率达68%.用紫外.可见分光光度计、荧光分光光度计、红外光谱仪、透射电子显微镜等对制备的样品进行表征.结果表明:CdTe Ods紫外吸收峰及荧光发射峰均随回流时间延长而红移,即粒径在不断增大;荧光发射峰窄而对称,表明QDs分散性好、大小较均一,半峰宽随回流时间延长而逐渐变宽,表明粒径在增大的同时粒径分布范围也变宽;从TEM及紫外.可见光谱推算,可知其粒径约为3 nm;红外光谱图说明作为稳定剂的巯基乙酸对QDs表面起到修饰作用.     

Synthesis and electronic properties of semiconductor nanoparticles/quantum dots

This review examines recent work on the synthesis, characterisation and potential applications of semiconductor nanoparticles (quantum dots). Recent advances in single quatum dot spectroscopy is also reviewed.     

Glass substrates crosslinked with tetracycline-imprinted polymeric silicate and CdTe quantum dots as fluorescent sensors

A fluorescence-based sensor that combines the merits of quantum dots (QDs) and molecularly imprinted polymers (MIPs) was first fabricated on a glass substrate via a sol–gel route. Some of the key performance factors, including silane selection, substrate etching, the reaction times of glass silanization and sol–gel polymerization, and the times and methods used for template stripping and loading, were discussed and determined. After fabricating the sensor on either a 3-aminopropyltriethoxysilane (APS) or a 3-mercaptopropyltriethoxysilane (MPS) modified glass substrate, APS showed a much better performance than MPS as both the capping reagent of QDs and the functional monomer of tetracycline-templated MIPs. The APS-QDs on APS-modified glass had a higher imprinted factor (IF = 5.6), a lower LOD (2.1 μM, 3σ), and a more stable signal (2.8%, n = 10 at 70 μM) than those on the MPS-modified glass (IF = 5.2, LOD = 6.5 μM, stability = 6.2%). Furthermore, the recoveries of tetracycline (70 μM) from BSA (133 μg/mL) and FBS (0.66 ppt) by the APS-modified glass were 98% (RSD = 3.5%, n = 5) and 97% (RSD = 5.7%), respectively. For the MPS-modified glass, recoveries of 95% (RSD = 7.2%) and 89% (RSD = 8.7%) were observed at 67 μg/mL of BSA and 0.33 ppt of FBS, respectively.     

水溶性CdTe量子点的合成及其用于荧光猝灭法测定肌红蛋白

以3-巯基丙酸为稳定剂,合成了具有特殊光学性质的水溶性CdTe量子点,其最大发射波长位于544 nm.利用荧光光谱、紫外可见光谱及圆二色光谱法系统的研究了CdTe量子点与肌红蛋白(Mb)二者结合前后体系光谱的变化,从而证实了CdTe量子点与Mb之间静电结合反应的特征.在pH 7.0的PBS缓冲液中,用CdTe量子点作为荧光探针研究了肌红蛋白与量子点的相互作用,并基于肌红蛋白对CdTe量子点有显著的荧光猝灭作用,建立了肌红蛋白的快速检测方法.在最佳实验条件下,该体系荧光强度的猝灭程度(△F)与肌红蛋白质量浓度呈良好的线性关系,线性范围为0.3～24 μg/mL,检出限为0.13 μg/mL.该方法已对合成样品中肌红蛋白进行检测,并用于人体尿样中肌红蛋白的测定.