碳量子点的合成和应用

近几年,碳量子点作为纳米碳材料中的一颗新星,引起了人们广泛的关注。碳量子点除了具有优秀的光学性质,还有良好的水溶性、低毒性、环境友好、成本低等优点。自从碳量子点被发现以来,人们发现了多种多样的合成碳量子点的方法,主要有电化学法、化学烧蚀法、激光法和微波法等。由于碳量子点具有许多优点,被广泛应用于很多领域,特别是在光催化、生物成像、化学传感等方面。本文介绍了碳量子点的主要合成方法和主要应用。     

碳量子点的合成、表面改性及应用研究进展

碳量子点(CDs)因其独特的物理或化学特性而被广泛应用于各领域。与传统半导体量子点相比,CDs的最大优点是低细胞毒性,高生物相容性,同时对环境友好。通过选择特定的合成或改性方法来获得满足应用条件的碳点,是研究人员的迫切需求。综述了CDs的自上而下和自下而上的各种合成方法并描述了其合成后的各种特性,其中自上而下法偏向于生产较大量的碳点,但尺寸和碳点形态难以控制。自下而上法能更好地控制碳点的尺寸及形状,但过程较为复杂耗时。再进一步探讨了CDs的表面改性包括表面钝化,表面功能化的研究进展。不同合成方法或改性方法制备的碳点特性具有较大差别,延伸出其在各方面的应用,包括细胞成像,荧光传感,药物递送,光催化,离子检测等。最后总结分析了碳点研究可进一步探索的方面,以期为碳点更深入的研究与更广泛的应用提供参考。     

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。     

铜铟硫三元量子点的合成及在生物领域的应用

量子点(quantum dots,QDs)是一种尺寸在1～10 nm的半导体纳米晶体,具有特殊的光、电、磁学性质,在定量分析、生物医学、太阳能电池等领域前景巨大.其中铜铟硫(CuInS2)三元QDs因其不含毒性重金属元素镉或铅,且荧光性质稳定,从而被认为是一种理想的绿色环保型荧光纳米材料.详细介绍了CuInS2三元QD...     

基于水相法制备CdTe量子点及其功能化组装研究进展

量子点具有荧光效率高、Stokes位移大,以及独特的宽激发窄发射性能,在实现高分辨率生物成像方面具有巨大的应用价值。水相法制备CdTe量子点具有操作简单、可重复性强以及产物水溶性良好等优点,成为绿色、廉价合成量子点的新宠。以CdTe为主体,总结了近年来出现的水相法制备CdTe量子点的新进展,并对其功能化组装新思路进行了综述。     

Ⅱ-Ⅵ型量子点的制备、修饰及其生物应用

根据近10年的研究情况对Ⅱ-Ⅵ型量子点的制备、修饰进行了介绍,分析了量子点制备过程中的优、缺点. 探讨了Ⅱ-Ⅵ量子点在生物应用的最新研究成果,并对其研究前景进行了预测.     

碳量子点的合成、性质及其应用

碳量子点(CQDs,C-dots or CDs)是一种新型的碳纳米材料,尺寸在10nm以下,具有良好的水溶性、化学惰性、低毒性、易于功能化和抗光漂白性、光稳定性等优异性能,是碳纳米家族中的一颗闪亮的明星。自从2006年[1]报道了碳量子点(CQDs)明亮多彩的发光现象后,世界各地的研究小组开始对CQDs进行了深入的研究。最近几年的研究报道了各种方法制备的CQDs在生物医学、光催化、光电子、传感等领域中都有重要的应用价值。这篇综述主要总结了关于CQDs的最近的发展,介绍了CQDs的合成方法、表面修饰、掺杂、发光机理、光电性质以及在生物医学、光催化、光电子、传感等领域的应用。     

生物医用量子点材料的研究进展

量子点是一种新型的荧光材料,由于独特的微观结构和物理、化学特性,使其在生物医学领域有广阔的应用前景。通过对近十多年来,有关含重金属的量子点制备技术、应用实例等的现状分析,提出了合成新颖的无重金属量子点即低毒性或生物兼容性量子点的重要意义和迫切性,介绍了合成低毒性或生物兼容性量子点的最新研究现状,并展望了今后的发展前景。     

量子点的合成、表面修饰及在聚合物太阳电池中的应用

量子点因具有特殊的量子尺寸效应而得到广泛应用,尤其是在聚合物太阳电池中的应用具有独特的优势。列举了量子点常见的合成方法,如有机相合成法、水相合成法、水热法和溶剂热法、微波辅助水热法、微乳液法等;介绍了常见的量子点表面修饰方法,如偶联剂法、配位基交换法及化学反应法等;最后,介绍了表面修饰后的量子点在聚合物太阳电池中的应用,并针对器件效率较低这一问题讨论了提高聚合物/量子点太阳电池效率的方法。     

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.     

Amphoteric CdSe nanocrystalline quantum dots

The nanocrystal quantum dot (NQD) charge states strongly influence their electrical transport properties in photovoltaic and electroluminescent devices, optical gains in NQD lasers, and the stability of the dots in thin films. We report a unique electrostatic nature of CdSe NQDs, studied by electrophoretic methods. When we submerged a pair of metal electrodes, in a parallel plate capacitor configuration, into a dilute solution of CdSe NQDs in hexane, and applied a DC voltage across the pair, thin films of CdSe NQDs were deposited on both the positive and the negative electrodes. Extensive characterizations including scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier transform infrared (FTIR) and Raman studies revealed that the films on both the positive and the negative electrodes were identical in every respect, clearly indicating that: (1)?a fraction (<1%) of the CdSe NQDs in free form in hexane solution are charged and, more importantly, (2)?there are equal numbers of positive and negative CdSe NQDs in the hexane solution. Experiments also show that the number of deposited dots is at least an order of magnitude higher than the number of initially charged dots, indicating regeneration. We used simple thermodynamics to explain such amphoteric nature and the charging/regeneration of the CdSe NQDs.     

Detection of bioconjugated quantum dots passivated with different ligands for bio-applications

Bioconjugation of quantum dots has resulted in a significant increase in resolution of biological fluorescent labeling. This intrinsic property of quantum dots can be utilized for sensitive detection of target analytes with high sensitivity; including pathogenic bacteria and cancer monitoring. The quantum dots and quantum dot doped silica nanoparticles exhibit prominent emission peaks when excited at 400 nm but on conjugation to model rabbit antigoat antibodies exhibit diminished intensity of emission peak at 600 nm. It shows that photoluminescence intensity of conjugated quantum dots and quantum dot doped silica nanoparticles could permit the detection of bioconjugation. Samples of conjugated and unconjugated quantum dots and quantum dot doped silica nanoparticles were subjected to enzyme linked immunosorbent assay for further confirmation of bioconjugation. In the present study ligand exchange, bioconjugation, fluorescence detection of bioconjugated quantum dots and quantum dot doped silica nanoparticles and further confirmation of bioconjugation by enzyme linked immunosorbent assay has been described.     

Extracellular biosynthesis of biocompatible CdSe quantum dots

An extracellular biosynthesis method has been developed to prepare cadmium selenide (CdSe) quantum dots (QDs) with strong fluorescence emission by incubating cheap Cd and Se inorganic salts with Escherichia coli (E.coli) bacteria. Ultraviolet–visible absorption spectra, photoluminescence (PL) spectra, and high‐resolution transmission electron microscopy analysis showed that the biosynthesised CdSe QDs have an average size of 3.1 nm, the excellent optical properties with fluorescence emission around 494 nm, and the good crystallinity. It was found that addition of 80 mg of mercaptosuccinic acid resulted in the formation of CdSe QDs with highest PL intensity. Furthermore, Fourier‐transform infrared spectra of as‐synthesised CdSe QDs confirmed the presence of a surface protein capping layer. The biosynthesised CdSe QDs were incorporated into the yeast cells as illustrated by laser confocal scanning microscopy images, showing a great potential in bio‐imaging and bio‐labelling application.Inspec keywords: microorganisms, molecular biophysics, fluorescence, visible spectra, nanofabrication, nanobiotechnology, proteins, cellular biophysics, nanostructured materials, wide band gap semiconductors, cadmium compounds, semiconductor quantum dots, II‐VI semiconductors, transmission electron microscopy, photoluminescence, optical microscopy, ultraviolet spectra, Fourier transform infrared spectra, biological techniques, semiconductor growthOther keywords: biocompatible CdSe quantum dots, extracellular biosynthesis method, cadmium selenide quantum dots, high‐resolution transmission electron microscopy analysis, biosynthesised CdSe QDs, Fourier‐transform infrared spectra, Escherichia coli, ultraviolet‐visible absorption spectra, PL intensity, fluorescence emission, photoluminescence spectra, optical properties, surface protein capping layer, laser confocal scanning microscopy images, bioimaging, biolabelling application, yeast cells, f mercaptosuccinic acid, CdSe     

Photoluminescence-enhanced biocompatible quantum dots by phospholipid functionalization

A simple two-step strategy using phospholipid (PPL) to functionalize core/shell CdSe/ZnS quantum dots (QDs) has been described. The experimental data show that the use of S-H terminated PPL results not only in the high colloidal stability of core/shell CdSe/ZnS QDs in the aqueous phase, but also in the significant enhancement of photoluminescence. The degree of the enhancement is a function of the PPL-CdSe/ZnS QDs sample concentration. These results might be promising for future biological platform in new devices ranging from photovoltaic cells to biosensors and other devices.     

Multi-functional chitosan nanoparticles encapsulating quantum dots and Gd-DTPA as imaging probes for bio-applications

Chitosan was used to encapsulate both CdSe/ZnS quantum dots (QDs) and the magnetic resonance imaging (MRI) contrast agent gadolinium-diethylenetriaminepentaacetate (Gd-DTPA), forming multi-functional nanoparticles that can be used in a wide range of in vitro or in vivo studies as fluorescent biological labels as well as MRI contrast agents, respectively. Multi-color QDs at pre-determined molar ratios were encapsulated into chitosan nanoparticles to produce bar-coding fluorescent labels. The encapsulated QDs and Gd-DTPA still maintained their desirable optical properties and relatively high relaxivity, respectively. The chitosan nanoparticles also showed good aqueous stability and enhanced biocompatibility on myoblast cells.     

Multi-wavelength intermittent photoluminescence of single CdSe quantum dots

A single chromophore detection using video-microscopy is one of the latest methodologies to reveal unique characteristics, which could not be obtained from ensemble measurements. Among many kinds of subjects, dynamic optical properties observed in colloidal semiconductor nanoparticles are attractive and important not only for the basis of photo-physics but also for application studies, e.g. biological labeling, electronic devices. In this study, fluorescence video-microscopy was performed on cadmium selenide (CdSe) quantum dots (QDs) spin-coated on a glass substrate. From single CdSe QDs detection, emissions at wavelengths separated over 60 nm were observed for the first time. This spectral feature was attributed to the existence of double-emissive relaxation processes in CdSe QDs. Photoluminescence intermittency was also observed both from relaxation processes. Fluorescence video-microscopy, which was advanced in biology, can be applicable for the real-time monitoring of dynamic properties in semiconductor photo-physics.     

Uncoated, broad fluorescent, and size-homogeneous CdSe quantum dots for bioanalyses

In the present study, we describe the synthesis of highly luminescent uncoated water-soluble CdSe quantum dots (QDs) possessing the following characteristics: approximately 2 nm in diameter, with very good size distribution (in 95% homodispersed) accompanied by a broad-band photoluminescent spectrum. The synthetic procedure is simple, is conducted at room temperature, in the absence of the most popular coordinating ligands (as TOPO or HDA), and is highly reproducible. The obtained CdSe core QDs possessed a comparatively long fluorescence half-life (approximately 30-90 ns, depending on the emission wavelength) detected by time-resolved spectroscopy. These QDs were further conjugated with antibodies and applied in several biochemical analyses.     

Sensitization of ZnO nanorods with CdSe quantum dots

We have optimized the low-temperature growth of aligned arrays of zinc oxide nanorods of controlled length and diameter on conductive substrates. Varying the solution concentration and growth time, we were able to tune the nanorod diameter and length in the ranges 40–600 nm and 0.5–15 μm, respectively. The grown zinc oxide nanorods were photosensitized with CdSe quantum dots (QDs) in an oleic shell, which was replaced by pyridine. We studied the optical and transport properties of the ZnO nanorod arrays, with and without CdSe QDs on their surface. The current-voltage characteristics of the ZnO nanorod arrays with CdSe QDs are significantly influenced by illumination with light at a wavelength under the absorption band of the QDs, which points to effective interaction between the QDs and ZnO matrix.     

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.     

Multi-wavelength intermittent photoluminescence of single CdSe quantum dots

A single chromophore detection using video-microscopy is one of the latest methodologies to reveal unique characteristics, which could not be obtained from ensemble measurements. Among many kinds of subjects, dynamic optical properties observed in colloidal semiconductor nanoparticles are attractive and important not only for the basis of photo-physics but also for application studies, e.g. biological labeling, electronic devices. In this study, fluorescence video-microscopy was performed on cadmium selenide (CdSe) quantum dots (QDs) spin-coated on a glass substrate. From single CdSe QDs detection, emissions at wavelengths separated over 60 nm were observed for the first time. This spectral feature was attributed to the existence of double-emissive relaxation processes in CdSe QDs. Photoluminescence intermittency was also observed both from relaxation processes. Fluorescence video-microscopy, which was advanced in biology, can be applicable for the real-time monitoring of dynamic properties in semiconductor photo-physics.