One-step synthesis of fluorescent smart thermo-responsive copper clusters: A potential nanothermometer in living cells

Temperature measurement in biology and medical diagnostics, along with sensitive temperature probing in living cells, is of great importance; however, it still faces significant challenges. Metal nanoclusters (NCs) with attractive luminescent properties may be promising candidates to overcome such challenges. Here, a novel one-step synthetic method is presented to prepare highly fluorescent copper NCs (CuNCs) in ambient conditions by using glutathione (GSH) as both the reducing agent and the protective layer preventing the aggregation of the as-formed NCs. The resultant CuNCs, with an average diameter of 2.3 nm, contain 1-3 atoms and exhibit red fluorescence (lambda(em) = 610 nm) with high quantum yields (QYs, up to 5.0%). Interestingly, the fluorescence signal of the CuNCs is reversibly responsive to the environmental temperature in the range of 15-80 degrees C. Furthermore, as the CuNCs exhibit good biocompatibility, they can pervade the MC3T3-E1 cells and enable measurements over the physiological temperature range of 15-45 degrees C with the use of the confocal fluorescence imaging method. In view of the facile synthesis method and attractive fluorescence properties, the as-prepared CuNCs may be used as photoluminescence thermometers and biosensors

Decoration of porous ceramic substrate with pencil for enhanced gas separation performance of carbon membrane

Carbon membranes have been extensively applied in gas separation field, and the cost and performance of membranes strongly rely on the properties of the substrate material. In this study, effective nanoporous carbon membranes were prepared by pencil coating of the macroporous ceramics, followed by carbonization treatment of polyfurfuryl alcohol (PFA) coated on the pencil-modified ceramics substrates. The decoration of the macroporous ceramics substrates with pencil effectively repairs surface defects and decreases surface roughness, and greatly prevents PFA from penetrating into the ceramics substrates during pyrolysis. The as-prepared carbon membranes showed high gas permeability and permselectivity properties. This work provides an efficient method to fabricate nanoporous carbon membranes with enhanced gas separation performance. (C) 2014 Elsevier Ltd. All rights reserved

Gold nanoclusters decorated with magnetic iron oxide nanoparticles for potential multimodal optical/magnetic resonance imaging

Efficient nanoprobes for fluorescent and magnetic resonance multimodal imaging (MRI/FI) are in high demand in bioimaging. Herein, a nanoprobe with fluorescent gold nanoclusters (NCs) and magnetic iron oxide composite materials (Fe3O4@AuNCs) was prepared for dual bioimaging. The AuNCs were synthesized using the glutathione (GSH) template. The hydrophobic Fe3O4 magnetic nanoparticles (MNPs) were capped with cetyltrimethyl ammonium bromide (CTAB) to obtain hydrophilic Fe3O4 MNPs. Subsequently, the Fe3O4@AuNCs were prepared by the adsorption of Fe3O4-CTAB on the GSH-AuNCs through electrostatic attraction. The resultant Fe3O4@AuNCs, having an average size of 13.5 nm, can be readily dispersed in water, which displayed a strong red fluorescence (lambda(Em) = 650 nm) with a quantum yield of 4.3%. Confocal laser scanning microscopy studies proved that the Fe3O4@AuNCs have good photostability and low cytotoxicity to 293T cells. The magnetic properties of Fe3O4@AuNCs showed that this material was a T-2-based contrast agent for MRI with a transverse relaxivity r(2) of 20.4 mM(-1) S-1. Furthermore, the signal intensity of the T-2-weighted MRI decreased with an increase in the concentration. The dual optical and magnetic properties of the synthesized Fe3O4@AuNCs were applicable to dual fluorescence and MR-based imaging

Interfacial synthesis of polyethyleneimine-protected copper nanoclusters: Size-dependent tunable photoluminescence, pH sensor and bioimaging

The copper nanoclusters (CuNCs) offer excellent potential as functional biological probes due to their unique photoluminescence (PL) properties. Herein, CuNCs capped with hyperbranched polyethylenimine (PEI) were prepared by the interfacial etching approach. The resultant PEI-CuNCs exhibited good dispersion and strong fluorescence with high quantum yields (QYs, up to 7.5%), which would be endowed for bioimaging system. By changing the reaction temperatures from 25 to 150 degrees C, the size of PEI-CuNCs changed from 1.8 to 3.5 nm, and thus tunable PL were achieved, which was confirmed by transmission electron microscopy (TEM) imagings and PL spectra. Besides, PEI-CuNCs had smart absorption characteristics that the color changes from colorless to blue with changing the pH value from 2.0 to 13.2, and thus they could be used as color indicator for pH detection. In addition, the PEI-CuNCs exhibited good biocompatibility and low cytotoxicity to 293T cells through MIT assay. Owing to the positively charged of PEI-CuNCs surface, they had the ability to capture DNA, and the PEI-CuNCs/DNA complexes could get access to cells for efficient gene expression. Armed with these attractive properties, the synthesized PEI-CuNCs are quite promising in biological applications. (C) 2016 Elsevier B.V. All rights reserved

Alcohol-assisted rapid growth of vertically aligned carbon nanotube arrays

Millimeter-to-centimeter scale vertically aligned carbon nanotube (VACNT) arrays are widely studied because of their immense potential in a range of applications. Catalyst control during chemical vapor deposition (CVD) is key to maintain the sustained growth of VACNT arrays. Herein, we achieved ultrafast growth of VACNT arrays using Fe/Al2O3 catalysts by ethanol-assisted two-zone CVD. One zone was set at temperatures above 850 degrees C to pyrolyze the carbon source and the other zone was set at 760 degrees C for VACNT deposition. By tuning synthesis parameters, up to 7 mm long VACNT arrays could be grown within 45 min, with a maximal growth rate of similar to 280 mu m/min. Our study indicates that the introduction of alcohol vapor and separation of growth zones from the carbon decomposition zone help reduce catalyst particle deactivation and accelerate the carbon source pyrolysis, leading to the promotion of VACNT array growth. We also observed that the catalyst film thickness did not significantly affect the CNT growth rate and microstructures under the conditions of our study. Additionally, the ultralong CNTs showed better processability with less structural deformation when exposed to solvent and polymer solutions. Our results demonstrate significant progress towards commercial production and application of VACNT arrays. (C) 2015 Elsevier Ltd. All rights reserved

考虑时变刚度与侧隙影响的非对称渐开线齿轮动力学特性研究

为获得更为准确的非对称渐开线齿轮动力学变化规律，将时变啮合刚度和齿轮侧隙两个因素引入传统齿轮副扭转振动模型，建立非对称渐开线齿轮的动力学模型；利用Runge-Kutta法求解该模型，获得时间历程图、相图、Poincaré映射图以及FFT频谱图，进而分析时变啮合刚度和齿轮侧隙变化时的齿轮动力学行为。研究发现，非对称渐开线齿轮的平均啮合刚度大于对称渐开线齿轮，具有更优的动力学性能；时变啮合刚度中的1阶谐波分量对动力学性能影响不大，但平均啮合刚度影响较大，且其与动力学性能之间呈现出非线性变化规律，即随着平均啮合刚度的增加，动力学特性由差变好，但继续增加后又变差，因此，需根据实际工况确定其最优值。随着齿轮侧隙的增加，动力学性能下降，与对称渐开线齿轮相同。该项研究对于扩充非对称渐开线齿轮动力学理论体系、提高其传动性能，具有一定的理论意义和应用价值