Eco-friendly (green) synthesis of magnetically active gold nanoclusters

Abstract

Au–Fe_xO_y composite nanoparticles (NPs) are of great technological interest due to their combined optical and magnetic properties. However, typical syntheses are neither simple nor ecologically friendly, creating a challenging situation for process scale-up. Here we describe conditions for preparing Au–Fe_xO_y NPs in aqueous solutions and at ambient temperatures, without resorting to solvents or amphiphilic surfactants with poor sustainability profiles. These magnetic gold nanoclusters (MGNCs) are prepared in practical yields with average sizes slightly below 100 nm, and surface plasmon resonances that extend to near-infrared wavelengths, and sufficient magnetic moment (up to 6 emu g^–1) to permit collection within minutes by handheld magnets. The MGNCs also produce significant photoluminescence when excited at 488 nm. Energy dispersive X-ray (EDX) analysis indicates a relatively even distribution of Fe within the MGNCs, as opposed to a central magnetic core.     

汤的威力:食品科学新知

汤在各国的饮食文化中都带有健康调理的色彩,现代临床医学和药效学也验证了部分汤的功效.本文简要回顾了有关汤中存在的纳米颗粒在形成、组成成分和活性实验上的研究结果,展望了汤纳米颗粒的研究能给功效成分筛选和毒理学研究带来的新思路.     

Sensitive detection of biological species through localized surface-plasmon resonance on gold nanodisks

In this paper, we are interested in the detection of biological molecules. This detection relies on the use of nanosensors based on localized surface-plasmon resonance (LSPR). We discuss the sensitivity of these nanosensors by studying the influence of the concentration of Biotin on the shift of the LSPR wavelength. Moreover, to study the selectivity of these sensors, the systems Biotin/Anti-Biotin (AB) and Biotin/Streptavidin (SA) are used to detect very weak concentration of AB or SA. We found respectively 7 pM and 3 nM for the limits of detection of SA and AB.     

Electrospinning of P3HT-PEO-CdS fibers by solution method and their properties

Homogeneous composite fibers of poly(3-hexylthiophene) (P3HT)-polyethylene oxide (PEO)-Cadmium Sulfide (CdS) were manufactured by electrospinning technique using chloroform as solvent. The incorporation of CdS in the composite fibers was determined by SEM, FTIR and TGA techniques. SEM and confocal microscopy have been used to determine size, surface morphology and distribution of the fluorescence phase in the fibers. A morphology change in P3HT/PEO fibers was caused by the presence of CdS: porous morphology was obtained for low CdS concentration (3.8 wt% and less) and when the content of CdS nanoparticles is higher, they were concentrated at the center of the fibers. The photoluminescence response was modified with CdS inside the P3HT-PEO fibers. By XRD it was determined that the introduction of CdS nanoparticles in the P3HT-PEO fibers caused disorder in P3HT chains. The obtained composite fibers are promising materials for optic and electronic applications.     

Size Effect on Properties of Varistors Made From Zinc Oxide Nanoparticles Through Low Temperature Spark Plasma Sintering

Conditions for the elaboration of nanostructured varistors by spark plasma sintering (SPS) are investigated, using 8‐nm zinc oxide nanoparticles synthesized following an organometallic approach. A binary system constituted of zinc oxide and bismuth oxide nanoparticles is used for this purpose. It is synthesized at room temperature in an organic solution through the hydrolysis of dicyclohexylzinc and bismuth acetate precursors. Sintering of this material is performed by SPS at various temperatures and dwell times. The determination of the microstructure and the chemical composition of the as‐prepared ceramics are based on scanning electron microscopy and X‐ray diffraction analysis. The nonlinear electrical characteristics are evidenced by current–voltage measurements. The breakdown voltage of these nanostructured varistors strongly depends on grain sizes. The results show that nanostructured varistors are obtained by SPS at sintering temperatures ranging from 550 to 600 °C.     

Thermodynamic Evaluation of Inclusions Formation and Behaviour in Steels during Casting and Solidification

For demanding applications high steel cleanliness and strictly controlled inclusions are required. Primary inclusions are formed during steel treatments in the ladle. Most of these are removed to the ladle slag or on the lining. However, the rest of the inclusions still remain through the successive process stages, and additionally new inclusions are formed during casting and solidification due to decreasing thermodynamic solubility of oxygen in the steel at lower temperatures, reactions with surrounding slag, refractory materials and eventual contact with air. Inclusions formation and transformation are simulated by thermodynamic calculations in the steel/inclusions/slag system taking into account the solidification phenomena. In this paper inclusions in Si/Mn‐deoxidised steel and Al‐deoxidised Ca‐treated steels are contributed. Calculations are compared with experimental results from steel plants.     

Mesoflowers: A new class of highly efficient surface-enhanced Raman active and infrared-absorbing materials

A method for the synthesis of a new class of anisotropic mesostructured gold material, which we call “mesoflowers”, is demonstrated. The mesoflowers, unsymmetrical at the single particle level, resemble several natural objects and are made up of a large number of stems with unusual pentagonal symmetry. The mesostructured material has a high degree of structural purity with star-shaped, nano-structured stems. The mesoflowers were obtained in high yield, without any contaminating structures and their size could be tuned from nano- to meso-dimensions. The dependence of various properties of the mesoflowers on their conditions of formation was studied. The near-infrared-infrared (NIR-IR) absorption exhibited by the mesoflowers has been used for the development of infrared filters. Using a prototypical device, we demonstrated the utility of the gold mesoflowers in reducing the temperature rise in an enclosure exposed to daylight in peak summer. These structures showed a high degree of surface-enhanced Raman scattering (SERS) activity compared to spherical analogues. SERS-based imaging of a single mesoflower is demonstrated. The high SERS activity and NIR-IR absorption property open up a number of exciting applications in diverse areas. Electronic Supplementary Material  Supplementary material is available in the online version of this article at http://dx.doi.org/ and is accessible free of charge.     

高炉炉温与铁水含硅量工程推算法及应用

在既定冶炼条件下，依据炉内反应平衡学原理，导出了炉温定量推算式及铁水[Si]量推算式，其推算结果与实际数据具有良好对应关系，可用于现场操作推算与调控参考。     

Adhesive wear behaviour of cast aluminium–silicon alloys: Overview

This paper describes the various technological aspects related to adhesive wear of cast aluminium–silicon (Al–Si) alloys. Number of hypothesis and theories proposed in the last two decades in order to explain the different phenomenon related with wear and friction, and influence of test parameters (such as load, sliding speed, counter-surface) and work material properties (like mechanical and metallurgical) on tribological behaviour of aluminium–silicon alloys have been presented and discussed.