Size‐Tunable Highly Luminescent SiO2 Particles Impregnated with Number‐Adjusted CdTe Nanocrystals

Highly luminescent SiO₂ particles impregnated with CdTe nanocrystals (NCs) are prepared by a sol–gel procedure. Partial ligand exchange from thioglycolic acid to 3‐mercaptopropyltrimethoxysilane (MPS) on the NCs enables retention of the initial photoluminescence (PL) efficiency of the NCs in water, while the simultaneous addition of a poor solvent (ethanol) results in regulated assembly of the NCs through condensation of hydrolyzed MPS. The SiO₂ particles thus prepared have, for example, a diameter of 16 nm and contain three NCs each. The PL efficiency of these particles is 40 %, while the initial efficiency is 46 % in a colloidal solution. The redshift and narrowed spectral width in PL observed after impregnation indicate that the concentration of NCs in these nearly reaches the ultimate value (on the order of 10²¹ particles per liter). The porosity of these particles is investigated by means of N₂ adsorption–desorption isotherms. Due to the SiO₂ shell, these particles have higher stability in phosphate‐buffered saline buffer solution than the initial NCs. Their potential use for labeling in bio‐applications is investigated by conjugating biotinylated immunoglobulin G to them by using streptavidin maleimide as linker. Successful conjugation is confirmed by electrophoresis in agarose gel. This preparation method is an important step towards fabricating intensely emitting biocompatible SiO₂ particles impregnated with semiconductor NCs.     

Self‐Assembled Luminescent Quantum Dots To Generate Full‐Color and White Circularly Polarized Light

The design and fabrication of quantum dots (QDs) with circularly polarized luminescence (CPL) has been a great challenge in developing chiroptical materials. We herein propose an alternative to the use of chiral capping reagents on QDs for the fabrication of CPL‐active QDs that is based on the supramolecular self‐assembly of achiral QDs with chiral gelators. Full‐color‐tunable CPL‐active QDs were obtained by simple mixing or gelation of a chiral gelator and achiral 3‐mercaptopropionic acid capped QDs. In addition, the handedness of the CPL can be controlled by the supramolecular chirality of the gels. Moreover, QDs with circularly polarized white light emission were fabricated for the first time by tuning the blending ratio of colorful QDs in the gel. The chirality transfer in the co‐assembly of the achiral QDs with the gelator and the spacer effect of the capping reagents on the QD surface are also discussed. This work provides new insight into the design of functional chiroptical materials.     

Size‐Tunable Polymeric Nanoreactors for One‐Pot Synthesis and Encapsulation of Quantum Dots

Hydrophilic polymeric nanoparticles are synthesized through a Bergman cyclization‐ mediated intramolecular chain collapse of structurally well‐defined linear polymers, and then used as size‐tunable nanoreactors to fabricate and encapsulate quantum dots in a one‐pot reaction. Crystalline quantum dots are formed in all of these nanoreactors and visualized by transmission electron microscopy. Smaller nanoreactors produce one quantum dot each while larger nanoreactors form a number, resulting in fluorescence quenching. By controlling the molecular weight of the linear polymer precursor, a variable number of nanocrystals are fabricated and assembled in a single nanoreactor.     

Continuous‐Flow Synthesis of CdSe Quantum Dots: A Size‐Tunable and Scalable Approach

In recent years, continuous‐flow/microreactor processing for the preparation of colloidal nanocrystals has received considerable attention. The intrinsic advantages of microfluidic reactors have opened new opportunities for the size‐controlled synthesis of nanocrystals either in the laboratory or on a large scale. Herein, an experimentally simple protocol for the size‐tunable continuous‐flow synthesis of rather monodisperse CdSe quantum dots (QDs) is presented. CdSe QDs are manufactured by using cadmium oleate as cadmium source, selenium dioxide as selenium precursor, and 1‐octadecene as solvent. Exploiting selenium dioxide as selenium source and 1‐octadecene as solvent allows execution of the complete process in open air without any requirement for air‐free manipulations using a glove box or Schlenk line. Continuous‐flow processing is performed with a stainless steel coil of 1.0 mm inner diameter pumping the combined precursor solution through the reactor by applying a standard HPLC pump. The effect of different reaction parameters, such as temperature, residence time, and flow rate, on the properties of the resulting CdSe QDs was investigated. A temperature increase from 240 to 260 °C or an extension of the residence time from 2 to 20 min affords larger nanocrystals (range 3–6 nm) whereas the size distribution does not change significantly. Longer reaction times and higher temperatures result in QDs with lower quantum yields (range 11–28 %). The quality of the synthesized CdSe QDs was confirmed by UV/Vis and photoluminescence spectroscopy, small‐angle X‐ray scattering, and high‐resolution transmission electron microscopy. Finally, the potential of this protocol for large‐scale manufacturing was evaluated and by operating the continuous‐flow process for 87 min it was possible to produce 167 mg of CdSe QDs (with a mean diameter of 4 nm) with a quantum yield of 28 %.     

具有光谱可调、高量子产率和稳定性的水溶性CdTe/Cd(OH)2核壳结构纳米粒子的可控水相合成

建立了一种简便的、以易得的无机盐为反应前体的水相法制备水溶性、高量子产率以及良好稳定性的CdTe/Cd(OH)2核壳结构量子点。本方法可以通过控制Cd(OH)2 壳层结构的厚度,使不同粒径量子点的荧光发射光谱由蓝绿色渐变到橙红色。利用透射电镜、X射线粉末衍射光谱、荧光光谱以及紫外可见光谱对该CdTe/Cd(OH)2核壳结构量子点进行了表征。CdTe/Cd(OH)2核壳结构量子点所具备的良好的水溶性可望应用于生物标记。本方法简便、反应条件温和并且容易操作,为无机金属化物包覆量子点提供了一种简便的途径。     

高质量尺寸可调CuFeS2纳米晶的合成与光电性质

制备了单分散性良好且尺寸可调的具有荧光性质的CuFeS2纳米晶,利用紫外-可见吸收光谱(UVVis)、荧光光谱、透射电子显微镜(TEM)、X射线粉末衍射(XRD)、元素分析和光电流测试等技术对其组分和结构进行了表征,分析了CuFeS2纳米晶尺寸变化对吸收光谱和光电响应行为的影响规律.随着CuFeS2纳米晶尺寸增大,其吸收峰位表现出符合量子尺寸效应的相应红移;具有荧光性质的CuFeS2纳米晶可控制备预示其在生物医学成像和光电器件等领域具有应用前景.     

Synthesis,Structure and Luminescence of Cd3Cu2 and Cd2Ni4 Heteronuclear Complexes with Macrocyclic Oxamide and 5‐Sulfosalicylicate

Two novel heteronuclear complexes [Cd₃(SSAL)₂(CuL)₂(H₂O)₄]_n ( 1 ) and [Cd₂(HSSAL)₂(NiL)₄] · 4H₂O ( 2 ) were synthesized and structurally determined, where SSAL is the fully deprotonated 5‐sulfosalicylic ion (CuL and NiL, H₂L = 2,3‐dioxo‐5,6,14,15‐dibenzo‐1,4,8,12‐tetraazacyclopentadeca‐7,13‐diene). Compound 1 displays a 1D ladder‐like chain and all these chains are further interlinked through hydrogen bonds resulting in a 2D architecture. The structure of 2 consists of 5‐sulfosalicylates and an oxamido‐bridge and is arranged in butterfly‐like hexanuclear molecules. The luminescent properties of compounds 1 and 2 are also discussed.     

Self‐Assembly through Coordination and π‐Stacking: Controlled Switching of Circularly Polarized Luminescence

Multiple noncovalent interactions can drive self‐assembly through different pathways. Here, by coordination‐assisted changes in π‐stacking modes between chromophores in pyrene‐conjugated histidine (PyHis), a self‐assembly system with reversible and inversed switching of supramolecular chirality, as well as circularly polarized luminescence (CPL) is described. It was found that l ‐PyHis self‐assembled into nanofibers showing P‐chirality and right‐handed CPL. Upon Zn^II coordination, the nanofibers changed into nanospheres with M‐chirality, as well as left‐handed CPL. The process is reversible and the M‐chirality can change to P‐chirality by removing the Zn^II ions. Experimental and theoretical models unequivocally revealed that the cooperation of metal coordination and π‐stacking modes are responsible the reversible switching of supramolecular chirality. This work not only provides insight into how multiple noncovalent interactions regulate self‐assembly pathways.     

Monodisperse AgSbS2 Nanocrystals: Size‐Control Strategy,Large‐Scale Synthesis,and Photoelectrochemistry

We report an efficient approach to the synthesis of AgSbS₂ nanocrystals (NCs) by colloidal chemistry. The size of the AgSbS₂ NCs can be tuned from 5.3 to 58.3 nm with narrow size distributions by selection of appropriate precursors and fine control of the experimental conditions. Over 15 g of high‐quality AgSbS₂ NCs can be obtained from one single reaction, indicative of the up‐scalability of the present synthesis. The resulting NCs display strong absorptions in the visible‐to‐NIR range and exceptional air stability. The photoelectrochemical measurements indicate that, although the pristine AgSbS₂ NC electrodes generate a cathodic photocurrent with a relatively small photocurrent density and poor stability, both of them can be significantly improved subject to CdS surface modification, showing promise in solar energy conversion applications.     

A Room‐Temperature Luminescent AgCF3COO Complex Consisting of Cationic Complex Chains and Anionic Guests

Reaction of p‐phenylenediacetonitrile (p‐phda) with AgCF₃COO afforded the coordination polymer, {[Ag₂(p‐phda)₂] [Ag₄(CF₃COO)₆]}_n ( 1 ), where the 1D cationic [Ag₂(p‐phda)₂]²⁺ chain acts as host and the anionic [Ag₄(CF₃COO)₆]^2– as guest molecules occupy the channel between neighboring host chains. This is a rare crystal example of AgCF₃COO complex consisting of cationic complex chains and anionic guests. In addition, complex 1 exhibits luminescence at room temperature in solid state.