Fluorophosphate Glasses Containing PbSe Quantum Dots

The specific features in the formation of IV–VI (PbSe) quantum dots in a vitreous fluorophosphate matrix are investigated by X-ray microanalysis, high-resolution scanning transmission electron microscopy (STEM), high-resolution X-ray diffraction, and optical absorption spectroscopy. A complete characterization of the quantum dots grown (their sizes, morphology, and distributions over the matrix bulk and sizes) in the glass is performed on the basis of the results obtained. The inference is made that spherical PbSe nanocrystals with a cubic lattice of the NaCl type are formed in fluorophosphate glasses. The nanocrystals are uniformly distributed over the matrix bulk and are characterized by a narrow size distribution (R/R 7%) in the studied size range R 1.8–10 nm, which corresponds to strong quantum confinement. It is noted that the mechanism of the quantum-dot growth in the glasses under consideration differs from the mechanisms studied earlier in glasses of silicate systems.     

Crystallization Behaviors of PbSe Quantum Dots in Silicate Glasses

This study, composed of three parts, aims at studying the crystallization behaviors of PbSe quantum dots (QDs) in silicate host glasses. Firstly, due to the importance of the choice of base glass for the QDs' crystallization, the selection of base glass compositions, the glass fragility, and glass formation ability (GFA) are discussed in details, and the results show that the selected glass compositions have an intermediate fragility and accordingly an intermediate glass transition temperature range among a wide variety of inorganic glass systems together with a good GFA/glass stability (GS). Thus, this base glass is suitable as the host glass in which PbSe QDs crystallize. Secondly, the experimental results on PbSe QDs' crystallizations are presented, and the results show that PbSe QDs can precipitate from silicate glasses favorably with no other chemical compounds precipitation, and the optimized temperature for PbSe QDs crystallization is 600°C. Lastly, the classical nucleation theory is used to analyze the PbSe QD crystallization behaviors in host glasses. The steady‐state nucleation rates and the growth rates of PbSe QDs as well as the time–temperature transformation (TTT) curves are calculated. The results indicate that the free surface energy between the PbSe nuclei and the host glass has great influence on the nucleation rates of PbSe QDs, while it has less effect on the growth rates of PbSe QDs; the crystallization behaviors of PbSe QDs with different volume fractions can be described well by the TTT curves while keeping the dimensionless empirical constant, α, unchanged for one certain curve.     

Fluorophosphate Glasses with Quantum Dots Based on Lead Sulfide

The specific features in the formation of IV–VI (PbS) quantum dots in a vitreous fluorophosphate matrix are investigated by X-ray microanalysis, high-resolution scanning transmission electron microscopy (STEM), high-resolution X-ray diffraction, and optical absorption spectroscopy. A complete characterization of the nanocrystals grown (their sizes and morphology) in the glass is performed on the basis of the results obtained. It is demonstrated that spherical PbS nanocrystals with a cubic lattice of the NaCl type are formed in fluorophosphate glasses synthesized. The nanocrystals are uniformly distributed over the matrix bulk and are characterized by a narrow size distribution (R/R 7%) in the studied size range R 2.0–15 nm, which corresponds to strong quantum confinement.     

Precipitation and Optical Properties of CsPbBr3 Quantum Dots in Phosphate Glasses

CsPbBr₃ quantum dots were precipitated in phosphate glasses through heat treatment. Controlled formation of CsPbBr₃ quantum dots was realized by adjustment of heat‐treatment conditions. Absorption and photoluminescence spectra of CsPbBr₃ quantum dots were tuned from 432 to 521 nm. Upon ultraviolet or blue light excitation, efficient photoluminescence from these CsPbBr₃ quantum dots doped phosphate glasses was observed.     

Quantum Dots in Glasses: Size-Dependent Stokes Shift by Lead Chalcogenide

Size-dependent Stokes shift of PbS quantum dots (QDs) formed in the glasses was investigated. PbS QDs with diameters of 3.5 nm to 13.3 nm were precipitated in silicate glasses with different S/Pb ratios using the conventional thermal treatment method. Absorption and photoluminescence (PL) of PbS QDs were tuned from ~0.9 μm (1.38 eV) to ~2.3 μm (0.54 eV) by adjusting the diameters of PbS QDs from 3.5 nm to 13.3 nm. PL energies of QDs exhibited linear dependence on the absorption energies with a slope of 0.484 for PbS QDs with band gap energies larger than 0.98 eV, and the maximum Stokes shift was found to be 206.2 meV for 3.5 nm-sized PbS QDs. For large PbS QDs with band gap energies smaller than 0.98 eV, Stokes shift was found to be ~20 meV or smaller. The size-dependent Stokes shift indicated that surface defects made the main contribution and relative energy positions of these surface defects were strongly dependent on the size of PbS QDs.     

Influence of Intermediate ZnO on the Crystallization of PbSe Quantum Dots in Silicate Glasses

Glasses containing PbSe quantum dots have important prospective applications in the area of near infrared optoelectronic devices. ZnO plays an important but complicated role in the preparation of quantum dot glass. We gave reasonable elaborations on the color changes of the as‐prepared and annealed glasses containing PbSe quantum dots. The as‐prepared glasses presenting nearly black to transparent straw‐yellow colors with rising ZnO content can be understood in terms of the conversion between PbSe and ZnSe; the colors of all annealed glasses turning very black can be well explained through thermodynamic calculations with the Gibbs–Helmho1tz equation. Next, according to the results of X‐ray diffraction, transmission electron microscopy and optical measurements, the sample with an introduction of 9.4 wt.% ZnO possesses a maximum degree of crystallization and the best optical properties among all samples, which suggests the host glass with addition of 9.4 ± 1 wt.% ZnO is optimum for crystallization of PbSe quantum dots. Finally, we employed classical nucleation theory to quantitatively calculate the nucleation rates and growth rates of PbSe quantum dots, and found that with the growing ZnO content in host glass, the nucleation rate decreases, whereas the growth rate of PbSe quantum dot increases gradually.     

Plasmon‐Assisted Precipitation of PbS Quantum Dots in Glasses Containing Ag Nanoparticles

PbS QDs of ~ 5nm diameter were precipitated in glasses containing Ag nanoparticles after 3 min of 1.5‐W continuous‐wave laser illumination at λ = 532 nm. Photoluminescence spectra of the PbS QDs recorded in the 1.3~1.6 μm wavelength region revealed conversion of photon energy to thermal energy by surface plasmon resonance. Laser‐assisted local heating around Ag NPs can provide a new method to control the spatial distribution of QDs in glasses.     

Direct Imaging of the Distribution of Nd3+ Ions in Glasses Containing PbS Quantum Dots

The influence of Nd³⁺ ions was investigated on the precipitation and optical properties of PbS quantum dots (QDs) inside silicate glasses. The diameters of the PbS QDs decreased as the concentration of Nd³⁺ in the glass increased as evidenced by blue shifts in the absorption and photoluminescence spectra. Electron energy loss spectroscopy shows that Nd³⁺ ions exist preferentially inside the PbS nanocrystals rather than in the glass matrix. We postulate that Nd–O clusters are preserved during heat treatment and serve as nucleation sites for PbS crystals. No change in the local bonding scheme of the Nd³⁺ ions was observed following heat treatment.     

Spectroelectrochemistry of Quantum Dots

Spectroelectrochemistry (SEC) is a set of techniques with many advantages in the study and characterization of materials. Although SEC has not yet been widely used to study quantum dots (QDs), the information extracted from SEC experiments about these nanostructures is very useful. Most of the works that use SEC to study QDs are high‐quality pieces of research. This review intends to show how to perform SEC in an easy way and what information can be obtained using these techniques. Most of the examples shown in this review are related to semiconductor and carbon QDs. After a brief introduction, some optoelectronic properties of QDs and the main SEC techniques are described. The capabilities of SEC for the study of QDs are illustrated with examples extracted from literature. Finally, the needs of SEC to become a user‐friendly technique and its evolution to become more powerful are commented in the last section of the review.     

二维光子晶格的带隙位置以及影响带隙宽度的因素研究

利用四孔振幅掩模的傅里叶变换法,在LiNbO3∶Fe晶体中制作了二维光子晶格,利用功率计测量其透射效率,找到满足Bragg衍射条件的带隙并测量出了二维正方晶格斜45°角方向上以及水平方向上的相对带隙宽度。实验结果表明,在照射相同条件下二维正方格子斜45°方向上的相对禁带宽度比水平方向上的相对禁带宽度宽。     

量子点的合成研究

量子点（半导体纳米晶）是纳米尺度的微小发光粒子。作为新型的生物标记试剂,具有比传统的有机染料更好的光谱特性和光学稳定性。本文对量子点的光学性质、制备方法做一简要综述。     

Overview of Computational Simulations in Quantum Dots

Quantum dots (QDs) are semiconductor nanocrystals that exhibit exceptional properties not found in their bulk counterparts. They have attracted extensive academic and industrial attentions due to their quantum confinement effects and unique photophysical properties. Computational approaches such as first principles and classical molecular dynamics simulations are indispensable tools in both scientific studies and industrial applications of QDs. In this review, the state‐of‐the‐art progress in computational simulations of optical, electronic and thermal properties of QDs is summarized and discussed. First, the physics of QDs in low dimensional materials are comprehensively reviewed. Then, the theoretical basis and practical applications of two main computational methods are presented. Properties of QDs revealed by computational studies are summarized respectively. Finally, the paper was concluded with comments on future directions in computational modeling of QDs.     

Quantum Cutting in Luminescent Glasses and Glass Ceramics

In the last decade, revolutions in photonic material design and large-area nanostructure fabrication have given researchers and technologists tools to enable a new era of ultrahigh-efficiency photovoltaics. Quantum cutting has received much attention as a potential approach to enhance the photovoltaic conversion efficiency of solar cell in the recent decades. In this article, we review the phenomena, mechanisms, and design of the quantum cutting processes, focusing on the promising applications of the transparent glasses and glass ceramic materials as the down-converter of solar spectrum. We discuss the gaps between the current theoretical analysis and the practical applications of the quantum-cutting materials. To concave the negative effects of using the quantum-cutting materials as a down-converter on the front surface of the solar cell, much attention should be given to the choice of material and improvement of the material properties as well as the integration of photonic nanostructures and circuits on the solar cell.     

碳量子点在光催化领域的应用

碳量子点(carbon quantum dots,CQDs)是一种新型的零维碳纳米材料,具有易制备、低毒、生物兼容性好,及良好的光稳定性等特点,在生物成像、传感器及电致发光器件等领域具有潜在的应用前景。除此之外,碳量子点的尺寸依赖性、上转换发光性质、响应波长从近红外区延伸到可见区等优点使其成为太阳能光催化材料领域的"新宠"。就碳量子点在光催化领域的应用进行了综述。     

量子点的合成及表面修饰

量子点在生物学及生物医学中的应用是当今纳米技术领域中快速发展的研究方向。与传统的有机荧光染料相比,量子点发光的长程稳定性和同时探测多色信号的能力使其在生物成像和生物传感方面具有广泛的应用。概述了量子点的结构及合成方法,并介绍了量子点表面修饰的研究进展。     

量子点在生物化学分析中的应用

介绍了量子点的基本特性,对量子点在生物化学分析中的应用进行了综述,并展望了其发展趋势和应用前景。     

石墨烯量子点的制备与表征

介绍了一种改进的溶剂热法制备石墨烯量子点(GQDs)。该方法以N,N-二甲基甲酰胺(DMF)和氧化石墨烯(GO)作为溶剂和原料,过程中会对GO进行微波膨胀预处理,然后进行反应。分别采用紫外可见吸收、光致发光、红外、透射电镜对石墨烯量子点进行结构、形貌以及荧光性能的表征。通过该方法制备的GQDs的荧光发射光谱表明其具有可激发性且具有良好的荧光性能。     

石墨烯量子点的制备及应用

石墨烯量子点(GQDs)作为石墨烯家族的最新一员,除了继承石墨烯的优异性能,还因量子限制效应和边界效应而显现出一系列新的特性,引起了化学、物理、材料和生物等各领域科研工作者的广泛关注。GQDs的制备方法通常分自上而下和自下而上的方法。对其各种制备方法和应用分别进行了介绍,并结合各种应用对GQDs的要求给出了制备方法的建议。指出了GQDs研究中存在的问题及发展方向。