Quantum Dots for Display Applications

This article offers a materials-chemistry perspective for colloidal quantum dots (QDs) in the field of display, including QD-enhanced liquid-crystal-display (QD-LCD) and QD-based light-emitting-diodes (QLEDs) display. The rapid successes of QDs for display in the past five years are not accidental but have a deep root in both maturity of their synthetic chemistry and their unique chemical, optical, and optoelectronic properties. This article intends to discuss the natural match of QD emitters for display and chemical means to eventually bring about their full potential.     

手性碳量子点的制备及其应用

手性碳量子点(CQDs)因兼具优异的荧光性质、良好的生物相容性、较低的毒性、易于功能化以及手性特征等,在催化、检测和生物医学等领域具有广阔的应用潜力。目前,通过一步法或两步法制备的手性CQDs,已应用于手性催化、手性检测、高尔基体靶向成像、选择性调控酶和蛋白活性、选择性调控细胞能量代谢和促进植物生长等领域。然而,手性CQDs的发展初露头角,需进一步完善可控合成工艺,制备高荧光量子产率的长波长手性CQDs,使其在生物医学等领域绽放异彩。     

The Growth of Co:ZnO/ZnO Core/Shell Colloidal Quantum Dots: Changes in Nanocrystal Size,Concentration and Dopant Coordination

We report a synthesis route for the growth of Co:ZnO/ZnO core/shell quantum dots. This procedure consists of successive steps, comprising the addition of diluted precursor salt solutions, and heat treatment at 50 °C. By deriving a relation between the extinction coefficient at 250 nm and the nanocrystal diameter, we are able to monitor changes in quantum dot concentration during shell growth. We found that a mechanism based on the nucleation of new particles after salt addition and subsequent Ostwald ripening during the heat treatment is responsible for the shell growth. Based on ligand‐field absorption spectroscopy, we demonstrate that the Co²⁺ ions adsorbed at the surface of Co:ZnO quantum dots are incorporated inside the ZnO shells. Finally, EPR spectroscopy indicates that the surface‐adsorbed Co²⁺ ions can be incorporated as substitutional as well as interstitial Co²⁺ ions.     

从量子点的角度审视碳点的研究进展

碳点不仅具有类似于传统量子点的强发光和小尺寸特性,还表现出传统量子点无法比拟的水相分散性和生物相容性等优势.作为量子点领域的一个新兴分支,碳点的结构、合成化学和光电性质与传统量子点显著不同,也为量子点的发展提供了新的机遇和挑战.随着碳点领域的迅速发展和不断深化,越来越有必要在一些基本概念上与传统量子点比较,并从传统量子点的角度澄清碳点的独特特征和关键挑战.本综述主要聚焦于基本结构、合成化学、光学性质和应用研究等四个方面,从传统量子点基础概念的角度来重新审视碳点领域的研究进展和挑战.     

Long-Range Transport in an Assembly of ZnO Quantum Dots: The Effects of Quantum Confinement,Coulomb Repulsion and Structural Disorder

We have studied the storage and long-range transport of electrons in a porous assembly of weakly coupled ZnO quantum dots permeated with an aqueous and a propylene carbonate electrolyte solution. The number of electrons per ZnO quantum dot is controlled by the electrochemical potential of the assembly; the charge of the electrons is compensated by ions present in the pores. We show with optical and electrical measurements that the injected electrons occupy the S, P, and D type conduction electron levels of the quantum dots; electron storage in surface states is not important. With this method of three-dimensional charge compensation, up to ten electrons per quantum-dot can be stored if the assembly is permeated with an aqueous electrolyte. The screening of the electron charge is less effective in the case of an assembly permeated with a propylene carbonate electrolyte solution. Long-range electron transport is studied with a transistor set-up. In the case of ZnO assemblies permeated with an aqueous electrolyte, two quantum regimes are observed corresponding to multiple tunnelling between the S orbitals (at a low occupation) and P orbitals (at a higher occupation). In a ZnO quantum-dot assembly permeated with a propylene carbonate electrolyte solution, there is a strong overlap between these two regimes.     

Semiconductor Quantum Dots as Components of Photoactive Supramolecular Architectures

Luminescent quantum dots (QDs) are colloidal semiconductor nanocrystals consisting of an inorganic core covered by a molecular layer of organic surfactants. Although QDs have been known for more than thirty years, they are still attracting the interest of researchers because of their unique size-tunable optical and electrical properties arising from quantum confinement. Moreover, the controlled decoration of the QD surface with suitable molecular species enables the rational design of inorganic-organic multicomponent architectures that can show a vast array of functionalities. This minireview highlights the recent progress in the use of surface-modified QDs – in particular, those based on cadmium chalcogenides – as supramolecular platforms for light-related applications such as optical sensing, triplet photosensitization, photocatalysis and phototherapy.     

Solution‐Processable Graphene Quantum Dots

This minireview describes recent progress in solution‐processable graphene quantum dots (SGQDs). Advances in the preparation, modification, properties, and applications of SGQDs are highlighted in detail. As one of emerging nanostructured materials, possible ongoing research related to the precise control of the lateral size, edge structure and surface functionality; the manipulation and characterization; the relationship between the properties and structure; and interfaces with biological systems of SGQDs have been speculated upon.     

石墨相氮化碳量子点的制备及应用的研究进展

近年来,石墨相氮化碳(g-C3N4)因其稳定的物理化学性能和良好的生物相容性而受到研究者关注。与块体g-C3N4相比,石墨相氮化碳量子点(g-CNQDs)尺寸更小、荧光效率更高,且具有量子限域效应,因此拥有特殊的理化性质与更好的光催化性能。本文主要从g-CNQDs的制备策略和应用展开讨论,着重综述了微波辅助法、低温固相法、热化学腐蚀法和电化学刻蚀法制备g-CNQDs,以及g-CNQDs在催化剂、离子检测、生物传感与诊疗等领域的最新应用研究进展;指出了目前g-CNQDs在性质、制备和应用等研究方面的重点和难点;最后对g-CNQDs存在的问题和未来的发展方向作出了展望。     

Large and Emissive Crystals from Carbon Quantum Dots onto Interfacial Organized Templates

Here, we report template-assisted assembly of emissive carbon quantum dot (CQD) microcrystals on organized cellulose nanocrystals templates at the liquid–air interface. This large-scale assembly is facilitated by the complementary amphiphilic character of CQDs and cellulose nanocrystals in the organized nematic phase. The resulting large microcrystals up to 200 μm across show unusually high emission that is not observed for limited CQDs aggregates. The dense crystal packing of CQDs in the layered fashion suppresses local molecular rotations and vibrations, thus restricting the intermolecular energy transfer and corresponding quenching phenomena. The as-prepared crystals are mechanically stable and can be exploited for recyclable catalysis, enabling applications beyond the individual nanoparticles or disordered aggregates. The ligand-templated assembly can be used to diversify CQD crystal architectures to guide formation of fibers, microplates, and micro-flowers.     

水稳定的镁掺杂ZnO量子点:一锅法合成及细胞成像应用

一锅法合成了镁掺杂的ZnO量子点,利用APTES对其进行表面包覆,并采用XRD、TEM、UV-Vis、PL和FTIR等对材料进行了表征。结果表明镁掺杂能明显增强荧光发光强度,在合适的掺杂浓度(30%)下其量子产率由11%增加到33%。通过APTES的表面包覆使镁掺杂的ZnO量子点具有良好的水溶性和荧光稳定性,可用于MCF-7细胞成像研究。     

水稳定的镁掺杂ZnO量子点:一锅法合成及细胞成像应用

一锅法合成了镁掺杂的ZnO量子点, 利用APTES对其进行表面包覆, 并采用XRD、TEM、UV-Vis、PL和FTIR等对材料进行了表征。结果表明镁掺杂能明显增强荧光发光强度, 在合适的掺杂浓度(30%)下其量子产率由11%增加到33%。通过APTES的表面包覆使镁掺杂的ZnO量子点具有良好的水溶性和荧光稳定性, 可用于MCF-7细胞成像研究。     

量子点在生物分析及医学诊断中的研究与应用

量子点(quantum dots,QDs)是近年来发展起来的一种优异的新型荧光纳米材料,在生物分析及医学诊断研究中得到了广泛应用,并取得了一系列重要研究成果。本文简介了过去10年中量子点的合成和表面功能性修饰的发展,并重点介绍其在病原体检测、生物芯片、生物分子相互作用、生物传感器、基因沉默、细胞成像、靶向药物传输、光动力学治疗和植物学研究等领域的研究现状。同时,对量子点的应用前景及研究方向进行了评述和展望。     

CdSe Spherical Quantum Dots Stabilised by Thiomalic Acid: Biphasic Wet Synthesis and Characterisation

CdSe quantum dots stabilised by thiomalic acid have been synthesised by an aqueous biphasic ligand exchange reaction in air. The materials are completely water‐soluble and were found to be stable over a long time. X‐ray diffraction and transmission electron microscopy reveal the formation of CdSe nanocrystals with cubic structure (a=0.6077 nm; spatial group: F‐43m). The average particle size is about 5 nm. Energy dispersive X‐ray analysis shows that the nanocrystals are nonstoichiometric, with a Cd/Se ratio varying between 60/40 and 70/30, and indicates the presence of Cd²⁺ ions at the nanocrystal surface. Diffuse reflectance infrared Fourier transform measurements suggest that thiomalic acid chelates CdSe through the thiol group and one carboxylic function, while the second COOH group is semi‐free. A complex‐like structure is proposed, in which thiomalic acid forms a five‐membered chelate ring with the Cd²⁺ ions present on the nanocrystal surface. Chelate effect accounts for the easiness of ligand exchange and is expected to additionally stabilise the nanosystem.     

Graphene Nanosheets and Quantum Dots: A Smart Material for Electrochemical Applications

A novel material for the electrochemical determination of endocrine disruptors using a composite based on graphene oxide modified with cadmium telluride quantum dots has been evaluated. The morphology, structure and electrochemical performance of the composite electrodes were characterised by transmission electron microscopy, dynamic light scattering, UV‐visible absorption spectra, fluorescence spectra, Raman spectra and cyclic voltammetry. The dynamic light scattering, transmission electronic microscopy and spectrophotometric measurements all showed good distribution of the quantum dots with a small particle size. The electrochemical measurements demonstrated the high performance of the composite response in the presence of a light source. Differential pulse voltammetry allowed the development of a method to determine 17β‐estradiol levels in the range from 0.2 to 4.0 μmol L ^?1 with a detection limit of 2.8 nmol L ^?1 (0.76 μg L ^?1).     

单个量子点的光学性质与应用

量子点(QDs)是一种具有诸多优良光学特性的荧光纳米颗粒,已在化学分析、生物传感、分子影像等领域得到了广泛应用.单个量子点的光学性质研究有望发现一些宏观方法不能发现的实验现象,可以为改善其光学性能提供思路,有助于更好的应用于各领域.本文评述了单个量子点的检测与判定方法,单个量子点的荧光增强、漂白、眨眼(blinking)、蓝移等光学性质及其在单分子示踪、生物化学传感、超分辨定位技术等方面的应用.总结了目前量子点作为荧光探针在实际应用中遇到的问题,并提出未来量子点将朝着合成能同时满足尺寸小、量子产率高、 "non-blinking"、蓝移幅度大、无生物毒性的量子点及能同时为成像/检测提供荧光探针与散射探针的等离子体量子点等研究方向发展.     

Quantifying the Thermodynamics of Ligand Binding to CsPbBr3 Quantum Dots

Cesium lead halide perovskites are an emerging class of quantum dots (QDs) that have shown promise in a variety of applications; however, their properties are highly dependent on their surface chemistry. To this point, the thermodynamics of ligand binding remain unstudied. Herein, ¹H NMR methods were used to quantify the thermodynamics of ligand exchange on CsPbBr₃ QDs. Both oleic acid and oleylamine native ligands dynamically interact with the CsPbBr₃ QD surface, having individual surface densities of 1.2–1.7 nm^?2. 10‐Undecenoic acid undergoes an exergonic exchange equilibrium with bound oleate (K_eq=1.97) at 25 °C while 10‐undecenylphosphonic acid undergoes irreversible ligand exchange. Undec‐10‐en‐1‐amine exergonically exchanges with oleylamine (K_eq=2.52) at 25 °C. Exchange occurs with carboxylic acids, phosphonic acids, and amines on CsPbBr₃ QDs without etching of the nanocrystal surface; increases in the steady‐state PL intensities correlate with more strongly bound conjugate base ligands.