Ultrasmall Near‐Infrared Non‐cadmium Quantum Dots for in vivo Tumor Imaging

The high tumor uptake of ultrasmall near‐infrared quantum dots (QDs) attributed to the enhanced permeability and retention effect is reported. InAs/InP/ZnSe QDs coated by mercaptopropionic acid (MPA) exhibit an emission wavelength of about 800 nm (QD800‐MPA) with very small hydrodynamic diameter (<10 nm). Using 22B and LS174T tumor xenograft models, in vivo and ex vivo imaging studies show that QD800‐MPA is highly accumulated in the tumor area, which is very promising for tumor detection in living mice. The ex vivo elemental analysis (Indium) using inductively coupled plasma (ICP) spectrometry confirm the tumor uptake of QDs. The ICP data are consistent with the in vivo and ex vivo fluorescence imaging. Human serum albumin (HSA)‐coated QD800‐MPA nanoparticles (QD800‐MPA‐HSA) show reduced localization in mononuclear phagocytic system‐related organs over QD800‐MPA plausibly due to the low uptake of QD800‐MPA‐HSA in macrophage cells. QD800‐MPA‐HSA may have great potential for in vivo fluorescence imaging.     

Tunneling control of cavity linewidth narrowing via quantum interference in triangular quantum dot molecules

A scheme for tunneling control of cavity linewidth narrowing by quantum interference in triangular-type triple quantum dots (TQDs) is proposed. In such system, quantum interference induced by tunneling between the TQDs can result in the appearance of two transparency windows and a steep dispersion. Furthermore, when the sample is embedded in a ring cavity, an ultranarrow transmission peak is obtained within the narrowed transparency windows. And by varying the tunneling, the linewidth and the position of the ultranarrow transmission peak can be engineered. Because no coupling laser is required, the scheme proposed here is more convenient for future experiments and applications in optics, and may be useful in designing novel optoelectronic devices.     

Preparation of regularly ordered Ge quantum dot lattices in amorphous matrices

We compare structural and optical properties of Ge quantum dot lattices in amorphous silica matrix obtained by two recently published techniques for the preparation of regularly ordered quantum dot lattices in amorphous matrices. The first technique is self-ordering growth of (Ge + SiO₂)/SiO₂ multilayer at an elevated substrate temperature where diffusion and surface morphology effects drive the self-ordering. The second one is irradiation of (Ge + SiO₂)/SiO₂ multilayer by oxygen ions. The multilayer used for the irradiation is grown at room temperature in this case, resulting with no Ge clusters after the deposition process. The irradiation causes clustering of Ge and ordering of Ge quantum dots in the irradiation direction. We show that the size of the dots and their arrangement can be easily manipulated by the preparation parameters. The structural properties of the films prepared by these methods affect the quantum confinement of the charge carriers which is visible in the absorption properties of the films.     

碳量子点敏化二氧化钛复合光催化剂的制备与光催化降解苯酚

为了解决二氧化钛光催化剂存在的禁带宽度大和量子效率低的问题,利用具有优异光吸收性能和电子转移能力的碳量子点改性二氧化钛,可以大幅度提高二氧化钛的光催化性能。本文以富勒烯碳灰为原料,利用混酸回流法制备了一种发黄蓝光的碳量子点,然后采用一步水热法将碳量子点负载于二氧化钛制备了复合光催化剂。借助高分辨透射电子显微镜(HRTEM)、傅里叶变换红外光谱(FT-IR)、紫外可见光光谱(UV-vis)、荧光光谱、X射线衍射(XRD)、X射线光电子能谱分析(XPS)等表征手段对碳量子点和复合光催化剂进行表征,并以苯酚作为模拟废水进行光催化降解实验,结果表明,与纯二氧化钛相比,用碳量子点改性的二氧化钛对苯酚的去除率可提高60%,且其具有较好的稳定性与重复使用性,6次循环利用后仍可达到初次的97.8%。     

基于量子关联的显微成像研究进展

简要回顾了量子关联成像的基本原理和发展历程,从量子光源和经典光源的角度详细介绍了量子关联成像在显微成像中的研究进展。做出了基于经典源的量子关联成像因易于实施、成本较低,在显微成像中更具应用前景的判断。     

Green-emissive carbon quantum dots with high fluorescence quantum yield: Preparation and cell imaging

High fluorescence quantum yield (QY), excellent fluorescence stability, and low toxicity are essential for a good cellular imaging fluorescent probe. Green-emissive carbon quantum dots (CQDs) with many advantages, such as unique fluorescence properties, anti-photobleaching, low toxicity, fine biocompatibility and high penetration depth in tissues, have been considered as a potential candidate in cell imaging fluorescent probes. Herein, N, S-codoped green-emissive CQDs (QY= 64.03%) were synthesized by the one-step hydrothermal method, with m-phenylenediamine as the carbon and nitrogen source, and L-cysteine as the nitrogen and sulfur dopant, under the optimum condition of 200 °C reaction for 2 h. Their luminescence was found to originate from the surface state. In light of the satisfactory photobleaching resistance and the low cytotoxicity, CQDs were used as a cell imaging probe for HeLa cell imaging. The results clearly indicate that cells can be labeled with CQDs, which can not only enter the cytoplasm, but also enter the nucleus through the nuclear pore, showing their broad application prospect in the field of cell imaging.     

碳量子点的一步合成及其发光性质的研究

本文采用油浴加热柠檬酸一步法合成碳量子点,用HRTEM透射电镜和FTIR红外光谱对其形貌和结构进行表征。研究该碳量子点的荧光性质,初步探讨了其发光的可能机理。实验结果表明,该方法合成的碳量子点粒径大小为3~5 nm,在360 nm处有一个很强的紫外吸收峰,最大激发波长和发射波长分别为365 nm和460 nm,其光学稳定性良好,在pH5.0~7.0范围内,碳量子点的荧光强度随pH的变化比较敏感。     

Low-temperature synthesis of zirconium silicate stabilized perovskite quantum dot composite material

Perovskite quantum dots (PQDs) have been devised as an efficient narrow half-width phosphor and received extensive attention due to their high photoluminescence quantum yield (PLQY), adjustable emission colour and high colour purity. However, the low stability of perovskite quantum dots seriously affects its performance and application. Here, we have proposed a simple ligand-assisted precipitation method to encapsulate PQDs in zirconium silicate (ZrSi). Owing to the special stacked structure and high specific surface area of ZrSi, the composite material exhibits extremely high humidity stability and thermal stability compared to pure PQDs. Both ZrSi/CH₃NH₃PbBr₃ PQDs and ZrSi/CsPbBr₃ PQDs prepared by ZrSi packaging exhibit excellent luminescence properties, and the three-colour phosphor composite prepared by changing the halogen ratio has a very high colour gamut. In addition, ZrSi/CH₃NH₃PbBr₃ PQDs and ZrSi/CsPbBr₃ PQDs assembled white light-emitting diodes (LEDs) also have very excellent optical properties. This work provides a new method for the synthesis of high-stability perovskite quantum dots for white LED and display materials by using stacked structure materials.     

Improved peptidyl linkers for self-assembly of semiconductor quantum dot bioconjugates

We demonstrate improved peptide linkers which allow both conjugation to biomolecules such as DNA and self-assembly with luminescent semiconductor quantum dots. A hexahistidine peptidyl sequence was generated by standard solid phase peptide synthesis and modified with the succinimidyl ester of iodoacetamide to yield a thiol-reactive iodoacetyl polyhistidine linker. The reactive peptide was conjugated to dye-labeled thiolated DNA which was utilized as a model target biomolecule. Agarose gel electrophoresis and fluorescence resonance energy transfer analysis confirmed that the linker allowed the DNA to self-assemble with quantum dots via metal-affinity driven coordination. In contrast to previous peptidyl linkers that were based on disulfide exchange and were thus labile to reduction, the reactive haloacetyl chemistry demonstrated here results in a more stable thioether bond linking the DNA to the peptide which can withstand strongly reducing environments such as the intracellular cytoplasm. As thiol groups occur naturally in proteins, can be engineered into cloned proteins, inserted into nascent peptides or added to DNA during synthesis, the chemistry demonstrated here can provide a simple method for self-assembling a variety of stable quantum dot bioconjugates.      

Thermal conductivity of InAs quantum dot stacks using AlAs strain compensating layers on InP substrate

The growth and thermal conductivity of InAs quantum dot (QD) stacks embedded in GaInAs matrix with AlAs compensating layers deposited on (1 1 3)B InP substrate are presented. The effect of the strain compensating AlAs layer is demonstrated through Atomic Force Microscopy (AFM) and X-ray diffraction structural analysis. The thermal conductivity (2.7 W/m K at 300 K) measured by the 3ω method reveals to be clearly reduced in comparison with a bulk InGaAs layer (5 W/m K). In addition, the thermal conductivity measurements of S doped InP substrates and the SiN insulating layer used in the 3ω method in the 20–200 °C range are also presented. An empirical law is proposed for the S doped InP substrate, which slightly differs from previously presented results.     

Influences of silicon doping in quantum dot layers on optical characteristics of InAs/GaAs quantum dot infrared photodetector

We have investigated the effects of silicon doping concentration within thirty-period self-assembled quantum dot (QD) layers on quantum dot infrared photodetectors (QDIPs). The lens-shaped quantum dots with the dot density of 1 × 10¹¹ cm^− 2 were observed by atomic force microscope (AFM). From the high ratio of photoluminescence (PL) peak intensities from dot layer to that from wetting layer, we have concluded that high dot density caused the short diffusion length for carriers to be easily captured by QDs. Moreover, the Si-doped samples exhibited the multi-state transitions within the quantum dots, which were different to the single level transition of undoped sample. Besides, the dominant PL peaks of Si-doped samples were red-shifted by about 25 meV compared to that of the undoped sample. It should result from the dopant-induced lowest transition state and therefore, the energy difference should be equal to the binding energy of Si in InAs QDs.