CdS:Mn/ZnS核壳结构纳米晶体的场致发光性质

锰掺杂的核壳结构CdS:Mn/ZnS纳米晶体由胶体化学方法制备,并将该纳米晶体所形成的薄膜夹在两层Ta₂O₅薄膜中间,形成交流薄膜电致发光器件.该器件的电致发光强度随着环境温度的升高呈现先增强后减小的变化规律,并且Mn杂质的位置会影响其电致发光谱.     

Ultra-sensitive DNA assay based on single-molecule detection coupled with fluorescent quantum dot-labeling and its application to determination of messenger RNA

Rapid, inexpensive, and convenient methods for quantifying elemental sulfur (S⁰) with low or sub-μg g⁻¹ limits of detection would be useful for a range of applications where S⁰ can act as a precursor for noxious off-aromas, e.g., S⁰ in pesticide residues on winegrapes or as a contaminant in drywall. However, existing quantification methods rely on toxic reagents, expensive and cumbersome equipment, or demonstrate poor selectivity. We have developed and optimized an inexpensive, rapid method (∼15 min per sample) for quantifying S⁰ in complex matrices. Following dispersion of the sample in PEG-400 and buffering, S⁰ is quantitatively reduced to H₂S in situ by dithiothreitol and simultaneously quantified by commercially available colorimetric H₂S detection tubes. By employing multiple tubes, the method demonstrated linearity from 0.03 to 100 μg S⁰ g⁻¹ for a 5 g sample (R² = 0.994, mean CV = 6.4%), and the methodological detection limit was 0.01 μg S⁰ g⁻¹. Interferences from sulfite or sulfate were not observed. Mean recovery of an S⁰ containing sulfur fungicide in grape macerate was 84.7% with a mean CV of 10.4%. Mean recovery of S⁰ in a colloidal sulfur preparation from a drywall matrix was 106.6% with a mean CV of 6.9%. Comparable methodological detection limits, sensitivity, and recoveries were achieved in grape juice, grape macerate and with 1 g drywall samples, indicating that the methodology should be robust across a range of complex matrices.     

Colloidal Cu2ZnSnS4 nanocrystals generated by a facile route using ethylxanthate molecular precursors

We have demonstrated a flexible method for preparing Cu₂ZnSnS₄ (CZTS) nanocrystals by use of zinc ethylxanthate (Zn(ex)₂) and copper ethylxanthate (Cu(ex)₂). TEM, SEM, XRD, UV–vis, EDS, XPS and TG‐DTA indicate that the CZTS nanocrystals have been successfully synthesized. As air‐stable molecular precursors, Zn(ex)₂ and Cu(ex)₂ can optimize the synthesis of quaternary CZTS nanocrystals because Cu(ex)₂ and Zn(ex)₂ facilitate the formation of homogeneous precursor solutions including all precursors and then for the flexible production of CZTS nanocrystals in homogeneous reaction solutions. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Novel closed-cycle reaction mode for totally green production of Cu1.8Se nanoparticles based on laser-generated Se colloidal solution

Non-stoichiometric copper selenide (Cu_2-xSe, x=0.18～0.25) nanomaterials have attracted extensive attentions due to their excellent thermoelectric, optoelectronic and photocatalytic performances. However, efficient production of Cu_2-xSe nanoparticles (NPs) through a green and convenient way is still hindered by the inevitable non-environmentally friendly operations in common chemical synthesis. Herein, we initially reveal the coexistence of seleninic acid content and elemental selenium (Se) NPs in pulsed laser-generated Se colloidal solution. Consequently, we put forward firstly a closed-cycle reaction mode for totally green production of Cu_1.8Se NPs to exclude traditional requirements of high temperature and toxic precursors by using Se colloidal solution. In such closed-cycle reaction, seleninic acid works as the initiator to oxidize copper sheet to release cuprous ions which can catalyze the disproportion of Se NPs to form SeO₃^2- and Se^2- ions and further produce Cu_2-xSe NPs, and the by-product SeO₃^2- ions promote subsequent formation of cuprous from the excessive Cu sheet. In experiments, the adequate copper (Cu) sheet was simply dipped into such Se colloidal solution at 70 ℃, and then the stream of Cu_1.8Se NPs could be produced until the exhaustion of selenium source. The conversion rate of Se element reaches to more than 75% when the size of Se NPs in weakly acidic colloidal solution is limited between 1 nm and 50 nm. The laser irradiation duration shows negative correlation with the size of Se NPs and unobvious impact to the pH of the solution which both are essential to the high yield of Cu_1.8Se NPs. Before Cu sheet is exhausted, Se colloidal solution can be successively added without influences to the product quality and the Se conversion rate. Such green methodology positively showcases a brand-new and potential strategy for mass production of Cu_2-xSe nanomaterials.     

Multistage polar switching in bent-core mesogens

We report a novel type of electro-optical switching in a tilted smectic phase of bent-shaped mesogens. The switching consists of a continuous stage and two bistable transitions. Detailed optical and electro-optical measurements using high-speed imaging are given and possible interpretations of the experimental results are discussed.     

Phase behavior of flowerlike micelles in a SCF cell model

We study the interactions between flowerlike micelles, self-assembled from telechelic associative polymers, using a molecular self-consistent field (SCF) theory and discuss the corresponding phase behavior. In these calculations we do not impose properties such as aggregation number, micellar structure and number of bridging chains. Adopting a SCF cell model, we calculate the free energy of interaction between a central micelle surrounded by others. Based on these results, we predict the binodal for coexistence of dilute and dense liquid phases, as a function of the length of the hydrophobic and hydrophilic blocks. In the same cell model we compute the number of bridges between micelles, allowing us to predict the network transition. Several quantitative trends obtained from the numerical results can be rationalized in terms of transparent scaling arguments.     

Monitoring the buckling threshold of drying colloidal droplets using water-ethanol mixtures

We visualize the drying of droplets of colloids suspended in a mixture of two miscible solvents, namely water and ethanol. After a period of isotropic shrinkage, droplets suddenly buckle like elastic shells. For a fixed colloid solid fraction, the buckling threshold evolves as a function of ethanol content, due to changes of the solvent mixture physical properties, such as viscosity and evaporation rate. A simplified model predicting the qualitative behavior of the buckling threshold as a function of the initial ethanol mass fraction has been developed that fits well experimental results.     

Discotic liquid crystals of cucurbit[7]uril (CB[7])-functionalised Laponite clays

ABSTRACT

Here we demonstrate that in the presence of the small, barrel-shaped molecule cucurbit[7]uril (CB[7]) Laponite clay particles undergo a phase transition into a birefringent gel with lamellar structure and a fluid, Laponite-poor aqueous solution. We employ various characterisation methods and polarised light microscopy to study this transition and the system's structural and optical properties. Furthermore, when dried completely we obtain a layered, transparent composite film, still retaining some liquid-crystalline structure that can be rehydrated reversibly. We argue that this new system may be a model system for anisotropic patchy particles.     

CdSe量子点滤光片尺寸、温度依赖的光学特性

为了缩小光谱仪体积使之适用于军事卫星等领域,本文将胶体量子点作为滤光材料,研究了CdSe胶体量子点滤光片的光学特性.本文采用热注入法合成出了高质量的CdSe胶体量子点,经过对苯二胺消光处理制备成CdSe胶体量子点滤光片.利用透射电子显微镜(TEM)进行样品形貌结构的表征及粒径尺寸的测量,并分别在不同温度下进行了紫外.可...