Preparation and Characterization of PbS Quantum Dots Doped Ormocers

A new method for the preparation of semiconductor PbS quantum dot-doped Ormocer (Organically Modified Ceramic) has been developed. The Ormocer matrix was prepared through the hydrolysis and condensation of alkoxysilane precursors (sol-gel process). Formation of PbS particles took place in the porous Ormocer through H₂S gas reaction with a lead precursor incorporated at the solution stage. Control of the PbS dot size was achieved through the use of organically substituted trifunctional silanes. Particle formation and growth was studied under different experimental conditions (e.g. temperature and lead precursor concentrations) where nucleation and aggregation processes occurred. Determination of the average particle size was done by XRD. Transmission electron microscopy was also used to determine particle diameter as well as particle size distribution. Optical absorption spectra were measured at the UV-VIS wavelength range. Absorption edge blue shifts showed the quantum confinement effect in these materials. The non-hydrolyzed groups bonded to the silane prevented uncontrolled nucleation and aggregation during the particle formation and growth, i.e. at the solution stage by the homogeneous distribution of the Pb salts or at the xerogel state by the capping of the growing particles.     

Control of Semiconductor Particle Size in Sol-Gel Thin Films

Thin silica and silica-titania films containing CdS and PbS quantum size particles were obtained by separate preparation of the matrix and the colloidal sols and successive mixing. Sulfide particles were obtained by reaction of metal acetates with thioacetamide and control of particle size was achieved by surface capping agents. Powders and thin films deposited on soda-lime slides were prepared and characterized by XRD. Absorption spectra were recorded on films. The nonlinear refractive index was measured by anm-line technique on a CdS-doped sample. The nonlinear effect was found to be reversible and an ₂ value of −3 10⁻⁹ cm²/kW was measured.     

纳米TiO2/CdSe量子点的制备及其结构表征

用水热方法制备了CdSe量子点(CdSe QDs)并通过溶胶-凝胶法制备了量子点掺杂改性的纳米TiO2复合物。运用多种方法对此复合物进行表征,并对其光催化性能进行研究。结果表明:1在其制备焙烧过程中,CdSe QDs已掺杂进入TiO2纳米颗粒中形成纳米复合物;2 CdSe QDs的引入增强了TiO2的吸光性,改善了TiO2在可见光区的吸光效率;3 TiO2的原始晶体结构在焙烧过程中发生变化,形成了两种晶相的混晶,有利于其光催化活性的改善;此外纳米TiO2复合物的表面电子结构以及吸附性能等对其光催化作用也有协同作用,使其催化性能进一步提高。     

Additive-Free Electrophoretic Deposition of Graphene Quantum Dots Thin Films

The electrophoretic deposition (EPD) of graphene-based materials on transparent substrates is highly potential for many applications. Several factors can determine the yield of the EPD process, such as applied voltage, deposition time and particularly the presence of dispersion additives (stabilisers) in the suspension solution. This study presents an additive-free EPD of graphene quantum dot (GQD) thin films on an indium tin oxide (ITO) glass substrate and studies the deposition mechanism with the variation of the applied voltage (10–50 V) and deposition time (5–25 min). It is found that due to the small size (≈3.9 nm) and high content of deprotonated carboxylic groups, the GQDs form a stable dispersion (zeta-potential of about −35 mV) without using additives. The GQD thin films can be deposited onto ITO with optimal surface morphology at 30 V in 5 min (surface roughness of approximately (3.1±1.3) nm). In addition, as-fabricated GQD thin films also possess some interesting physico-optical properties, such as a double-peak photoluminescence at about λ=417 and 439 nm, with approximately 98 % visible transmittance. This low-cost and eco-friendly GQD thin film is a promising material for various applications, for example, transparent conductors, supercapacitors and heat conductive films in smart windows.     

Influence of the Host Matrix on the Microstructure of Sol-Gel Films Doped with CdS and PbS Q-Dots

The preparation of non-linear optical materials for integrated photonic devices needs the development of procedures which permit a very good control of the microstructure. Sol-gel is a good method for the preparation of glasses doped with semiconductor Q-Dots. However, the control on the microstructure and the properties of the material is related to many parameters (e.g., conditions of hydrolysis, precursors, heat treatments, etc.). In this work the effect of the matrix on the size and size distribution of the semiconductor nanoparticles was investigated. The films were characterized by UV-VIS-NIR spectrophotometry, Grazing Angle X-Ray Diffraction (GA-XRD), and High Resolution Transmission Electron Microscopy (HRTEM).     

高质量CdSe量子点的水相制备与表征

以巯基丁二酸为稳定剂, 亚硒酸钠为硒源, 制备了高质量水溶性CdSe量子点. 研究了反应时间、 镉与硒的摩尔比及镉与巯基丁二酸的摩尔比等实验条件对CdSe量子点光谱性能的影响. 分别用紫外-可见光谱、 荧光光谱、 X射线粉末衍射和透射电子显微镜等对量子点进行表征. 结果表明, 采用这种方法制得的CdSe量子点为立方晶型, 量子点的荧光发射峰在518～562 nm范围内连续可调, 并且发射峰的半峰宽始终保持在35 nm左右, 荧光量子产率可达21%.     

ZnS量子点的合成及荧光特性

采用液相沉淀法,用不同的硫源或金属离子螯合剂,从三个途径合成了不同粒径的ZnS量子点,并用透射电子显微镜,X-射线粉末衍射仪所合成的量子点进行了表征,用荧光分光光度计研究了量子点的荧光性质。结果表明,所合成的ZnS量子点为分散性好、纯度高且具有良好荧光特性的球形微粒。     

Optical Characterization of CdS Quantum Dots Nanoparticles Dispersed in Clays

Synthesis, characterization, and the optical behavior of CdS quantum dots nanoparticles were studied confined in clays. An alternative synthesis approach in different natural clays K-10 bentonite, Na-montemorillonite, halloysite, and saponite was carried out. The composite materials were characterized by XRD and FTIR spectroscopy, energy dispersive, scanning, and transmission electron microscopy. After CdS-QDs formation, the synthesized materials became fluorescent with emission wavelengths (average and standard deviation of the maximum wavelength; full width of half maximum): K-10 bentonite-CdS (590 ± 5 nm; 183 nm); Na-montmorillonite-CdS (550 ± 3 nm; 219 nm); saponite-CdS (550 ± 5 nm; 219 nm), and halloysite-CdS (590 ± 8 nm; 185 nm). (Supplemental materials are available for this article. Go to the publisher's online edition of the Journal of Dispersion Science and Technology to view the free supplemental file.)     

水溶性量子点的制备及应用

高量子产率的水溶性量子点在众多领域如发光晶体、薄膜光激发器件,尤其是生物荧光标记中展现出巨大的潜在应用价值.量子点荧光明亮、稳定,激发光谱宽,发射光谱窄,且发射波长可通过改变材料的粒径大小和组成来调控,因而在生物样本尤其是活组织的多色成像中极为有用,能有效避免因样本自身发光和光散射导致的信号干扰.量子点的研究已成为一门新兴的交叉科学,是目前最有吸引力的研究领域之一.近年来,水溶性量子点作生物荧光标记物的研究取得了长足的进展.本文简述了量子点的结构特征及光学特性,重点综述了水溶性量子点的制备方法及应用研究进展,特别是它在生物、医学中作荧光探针的最新研究.     

荧光可调控的碳量子点的电化学制备及性质研究

采用循环伏安法（Cyclic Voltammetry,CV）在碱性条件下电解石墨棒,得到水溶性的荧光碳量子点. 通过透射电子显微镜（TEM）、拉曼光谱（Raman spectrum）、原子力显微镜（AFM）对所制备的碳量子点进行形貌及结构表征,发现该碳量子点由1～4层石墨烯片层堆积形成,粒径在19 nm左右,厚度在1 nm左右. 通过荧光光谱（PL）、紫外可见吸收光谱（UV-vis）、傅里叶变换红外光谱（FTIR）、X射线光电子能谱（XPS）对所制备的碳量子点进行性质测定,发现该碳量子点在400和525 nm处有两个荧光发射峰,且通过控制扫描周数可以调节两个发射峰的相对强度,从而调控碳量子点的荧光颜色：随着扫描周数的增加,400 nm处发射峰的相对强度逐渐减小,而525 nm处发射峰的相对强度逐渐增大,两个荧光发射峰分别与碳量子点的π-π共轭体系和含氧官能团的n-π共轭体系有关.     

碳量子点的荧光发射机制

碳量子点(CQDs)一般是指粒径小于10 nm的零维碳材料,因其具有优良的光学特性而在生物成像、光学器件、生物复合材料和生物传感等领域得到广泛应用,并有望成为未来应用最广泛的一种碳材料.CQDs的光学特性受粒径、表面官能团及合成的条件(如温度、溶剂的种类和pH等)的影响,为了精准调控其光学性能以及进一步扩大其应用范围,...     

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.     

Doped Sol-Gel Films for Silica-on-Silicon Photonic Components

Further expansion of optical communication systems depends strongly on the development of cheap component technologies for functions such as switching, demultiplexing and amplification. Silica-on-silicon is increasingly recognised as the best approach to low cost integrated optics for such applications, but so far the functionality is limited. The purpose of NODES, a basic research collaboration sponsored by the European Union under the programme ESPRIT, has been to examine the application of sol-gel to a highly functional silica-on-silicon technology. In particular, the project has investigated film processing and characterisation, rare-earth doping for amplification, and semiconductor nanocrystallite doping for nonlinear functions. This paper presents the background and context to this work, summarises the technical results obtained, and discusses requirements and challenges for successful application of sol-gel in photonics.     

CdSe Quantum Dot Doped Amine-Functionalized Ormosils

Nanosized phenyl-capped CdSe particles (quantum dots) were isolated, after preparation inside reversed micelles present in AOT/H2 O/heptane, and then successfully redispersed in amine-functionalized ormosils derived from 3-aminopropyl(trimethoxy)silane (i.e., SA). Doped ormosils were formed into films of a few m thickness or small bulk samples. Host ormosils were structurally characterized by means of absorption spectroscopy, in the near- and mid-infrared ranges, and by 29Si and 13C solid-state nuclear magnetic resonance (NMR) spectroscopy. Doped ormosils were prepared and investigated via visible spectroscopy. The size of CdSe particles dispersed into the amino-ormosil hosts was calculated using the Effective Mass Model.     

微波一步法制备氮掺杂碳点及其用于多巴胺的检测研究

以柠檬酸为碳源,尿素为氮源,采用微波一步法制备得到稳定性高,水溶性好的蓝色荧光的氮掺杂碳点。并将该氮掺杂碳点经透射电子显微镜(TEM)、原子力显微镜(AFM)、X-射线光电子能谱(XPS)和红外光谱(IR)表征,发现其粒径为0.5～5 nm,平均粒径2.6 nm,富含羟基、羧基和氨基等官能团。在优化实验条件下,多巴胺浓度在2.5～37.5μmol/L范围内与N-CDs的荧光猝灭效率(I_F/I_(F0))呈良好的线性关系,方法的检出限为0.08μmol/L。采用该方法对正常人尿液中的多巴胺进行测定,其加标回收率为99.5%～106%,RSD为1.8%～2.3%,方法准确度高,结果满意。     

硅量子点支撑钯纳米粒子的可控制备

采用微乳法制备烯丙胺修饰的硅量子点(Si QDs),通过紫外-可见吸收光谱、荧光光谱和红外光谱对其光学性能进行了表征,通过透射电镜(TEM)对其形貌进行了表征,测得其荧光量子产率为10.06%,荧光寿命τ1=3.1982ns,τ2=12.4527ns。依据Si QDs的光学性质,制备了Si QDs支撑Pd纳米粒子材料(Si QDs/Pd)。通过量子点的浓度实现了Pd纳米粒子形貌和尺寸的有效控制。结果表明制备的Pd纳米材料具有较好的分散性,在有机催化和能源转化领域具有潜在的应用价值。     

水溶性量子点的制备及其与壳聚糖衍生物的自组装

以3-巯基丙酸(HS-CH2CH2COOH)为稳定剂, 制备了水溶性的碲化镉(CdTe)量子点(QDs), 考察了制备条件对QDs荧光性能的影响及CdTe QDs与壳聚糖及叶酸和聚乙二醇改性的壳聚糖的自组装. 研究发现, 壳聚糖及改性壳聚糖与QDs的复合物荧光强度相对纯的CdTe QDs明显增强, 且QDs被包裹在内核, 复合粒子呈明显的核/壳结构. 改性壳聚糖/QDs复合物较小且尺寸分布更为均一.     

Non‐Blinking Semiconductor Colloidal Quantum Dots for Biology,Optoelectronics and Quantum Optics

Twinkle, twinkle: The blinking of semiconductor colloidal nanocrystals is the main inconvenience of these bright nanoemitters. There are various approaches for obtaining non‐blinking nanocrystals, one of which is to grow a thick coat of CdS on the CdSe core (see picture). Applications of this method in the fields of optoelectronic devices, biologic labelling and quantum information processing are discussed.

     

表面修饰CdTe量子点的合成及其光学特性

在水相中合成高发光性能的CdTe量子点,研究以巯基乙酸(TGA)为稳定剂对CdTe表面进行修饰,制备在水中分散性良好的纳米晶,通过对CdTe量子点合成反应条件的摸索,掌握了其合成的反应规律.同时用紫外分光光度计、荧光分光光度计和透射电子显微镜对其进行了表征.结果表明,回流时间、n(Cd²⁺):n(HTe^-)、反应物浓度、TGA用量、反应体系pH值,对纳米晶的光学性质具有显著影响.回流2 h制得的CdTe纳米粒子直径约为5 nm,其发射峰窄且对称,表现出良好稳定的光学性质.     

基于上转换发光的碳量子点制备及应用研究

碳量子点具有易制备、低毒性、化学惰性高、荧光特性稳定等特点,和其他碳纳米材料(如富勒烯、碳纳米管和石墨烯等)一样引起了研究者的广泛关注。本文将从碳量子点的合成、特性、改性和应用等方面进行阐述,并对其受长波长光激发后可发出短波长光的这一上转换发光特性进行重点综述,为今后碳量子点的合成、改性以及应用提供一定的参考。