超声法一步合成生物相容的黄绿色荧光碳点

本文以蜡烛灰为碳源,在强酸环境中超声法一步合成了粒径均匀的荧光碳点（CDs）,粒径（3.47±1.81）nm,在紫外灯照射下发出黄绿色荧光.研究表明,CDs表面带有-OH、C=O和-COOH等官能团,存在sp3杂化和sp2杂化两种碳原子.所合成的碳点具有良好的耐光漂白能力和生物相容性,能潜在地作为黄绿色荧光成像试剂应用于细胞成像.     

Microstructural evolution and mechanical investigation of hot stretched graphene oxide reinforced polyacrylonitrile nanofiber yarns

To reveal the enhancement effect of graphene oxide (GO) in polymer nanofiber yarns, polyacrylonitrile (PAN)/GO nanofibers with different GO content (0.1‐0.5 wt%) were electrospun. The alignment of PAN chains and GO in nanofibers was enhanced by hot stretching of the yarn in dry conditions. The microstructure of the composite nanofiber yarns was investigated through X‐ray diffraction, polarized Fourier transform infrared spectroscopy and transmission electron microscopy. The results demonstrated that the hot stretching above T_g of PAN precursor lead to the increased orientation‐induced crystallization and alignment of PAN chain and GO. The yarn with 0.1 wt% GO and stretched by 4 times its length obtained the highest strength and modules (310.88 ± 24.68 MPa and 7.24 ± 0.55 GPa), which were 600% and 500% higher than those of the as‐electrospun pure PAN yarn. The most promising tensile properties found in hot stretched yarns with low GO content was because the strong interaction occurred between PAN molecules and oxygen‐containing functional groups. Indirect evidence of GO aggregation was also presented, which adversely affected the mechanical properties at higher GO content. Composite nanofiber yarns were sewable and weavable, and could be used as a new generation of composite reinforcement after pyrolysis.     

Nanosized anatase titanium dioxide loaded porous carbon nanofiber webs as anode materials for lithium-ion batteries

Nanosized anatase titanium dioxide loaded porous carbon nanofibers (TiO₂/PCNFs) were prepared from electrospun TiO(OAc)₂/PAN/PMMA composite precursor fibers with different amount of PMMA porogen, which were sequentially heat-treated in different environments. Electrochemical measurement results show that these as-prepared TiO₂/PCNFs present higher cyclic reversible capacity than the TiO₂/CNFs counterpart (without PMMA porogen in its precursor fibers). Among the as-prepared TiO₂/PCNFs samples, the representative TiO₂/PCNFs (the mass ratio of PAN to PMMA is 3:1) exhibits the best high-rate performance with a high stable capacity retention about 200 mAhg^{− 1} at a current density as high as 800 mAg^{− 1}. This novel TiO₂/PCNFs composite material opens up a promising application in high-power lithium-ion batteries.     

Enhanced conductivity composites for aircraft applications: carbon nanotube inclusion both in epoxy matrix and in carbonized electrospun nanofibers

The potential of carbonized electrospun nanofiber mats to render epoxy resin composites for aircraft applications electrically and thermally more conductive was investigated. The effect of carbon nanotube inclusion both inside the carbon nanofiber and in the epoxy resin matrix material was studied, in order to reveal any synergistic effects of multilevel presence of nanosized reinforcements on the conductivity and mechanical properties. The carbon nanotube inclusion into the carbonized nanofibers increased the electrical conductivity of the samples by 20–50% and the thermal conductivity by approximately three times leading to a higher value than that of the conventional composites. The preparation of layered composites with a conductive upper layer containing nonwoven carbon nanofabric and a load bearing lower layer with conventional unidirectional carbon fiber reinforcement can offer a cost‐effective and weight‐saving solution for the replacement of metal meshes in structural aircraft composites. Copyright © 2014 John Wiley & Sons, Ltd.     

基于头孢他啶测定的CQDs内标型比率荧光探针的构建

以天然生物质蒲公英为碳源,加入乙二胺,通过一步水热法合成氨基化蒲公英碳量子点(DE-CQDs).该DE-CQDs可与罗丹明6G(Rh6G)通过静电吸附作用形成具有特征双发射信号的DE-CQDs/Rh6G复合物.单一激发波长343 nm下,BR缓冲溶液pH 3.0时,复合物DE-CQDs/Rh6G于425 nm和550 ...     

Sensitive pH probe developed with water-soluble fluorescent carbon dots from chocolate by one-step hydrothermal method

In present work, fluorescent carbon dots (CDs) with an average diameter of 2.5 nm were firstly synthesised by a simple, convenient and low-cost hydrothermal method from chocolate. The obtained CDs possessed fine monodispersity and bright blue fluorescence that was strongest at an excitation wavelength of 360 nm and had a comparable quantum yield of 12% (in case of dots prepared in presence of nitric acid). The emission peak depended on the excitation wavelength in the range from 320 to 440 nm. Ionic strength had a weak effect up to 1.0 M and then no significant change was found in the range of 1.0–4.5 M. The fluorescence intensity of CDs displayed good pH adaptability and a linear dependence on the pH change in the range of pH 1.0–3.0 and pH 9.0–12.5, which have promising potentials for pH sensor.     

A novel fluorescent assay for edaravone with aqueous functional CdSe quantum dots

Aqueous thiol-capped CdSe QDs with a narrow, symmetric emission were prepared under a low temperature. Based on the fluorescence enhancement of thiol-stabilized CdSe quantum dots (QDs) caused by edaravone, a simple, rapid and specific quantitative method was proposed to the edaravone determination. The concentration dependence of fluorescence intensity followed the binding of edaravone to surface of the thiol-capped CdSe QDs was effectively described by a modified Langmuir-type binding isotherm. Factors affecting the fluorescence detection for edaravone with thiol-stabilized CdSe QDs were studied, such as the effect of pH, reaction time, the concentration of CdSe QDs and so on. Under the optimal conditions, the calibration plot of C/(I − I₀) with concentration of edaravone was linear in the range of (1.45–17.42) μg/mL (0.008–0.1 μmol/L) with correlation coefficient of 0.998. The limit of detection (LOD) (3σ/κ) was 0.15 μg/mL (0.0009 μmol/mL). Possible interaction mechanism was discussed.     

Hydrothermal synthesis of fluorescent nitrogen-doped carbon quantum dots from ascorbic acid and valine for selective determination of picric acid in water samples

Nitrogen doped carbon quantum dots (N-CQDs) were synthesised by a hydrothermal method using ascorbic acid and valine as precursors. The as-synthesised N-CQDs were characterised by transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, UV?vis absorption spectra, as well as fluorescence spectrophotometer. The results revealed that the as-prepared N-CQDs were spherical shaped with an average diameter of 4 nm and emitted bright blue photoluminescence with a quantum yield of approximately 4.8 %. Additionally, we found that the fluorescence of the N-CQDs was intensively quenched by the addition of picric acid (PA). The decrease of the fluorescence intensity made it possible to determine PA in the linear range of 0.06–7.81 µg ml^–1 based on the fluorescence resonance energy transfer between PA and N-CQDs. The detection limit was as low as 11.46 ng ml^–1. The proposed approach was further successfully applied for the determination of PA in water sample collected from Fenhe river for public safety and security, suggesting its great potential towards water routine analysis.     

Fabrication of carbon quantum dots via ball milling and their application to bioimaging

Carbon quantum dots (CQDs) with an average diameter of 3 nm, exhibiting blue photoluminescence, have been obtained from commercial conductive carbon black by a cost-effective and straightforward exfoliation method using dry ball milling in the presence of sodium carbonate. As a secondary abrasive medium, sodium carbonate provides effective exfoliation of carbon black with a high degree of CQD graphitization and plays an essential role in the functionalization of CQDs with oxygen groups. Due to the low toxicity of CQDs against HeLa cancer cells (cell viability above 90% at a CQD concentration of 200 μg cm⁻³) and the ability to penetrate cells and emit blue light, CQDs are possibly suitable for biological imaging of cells.     

氮掺杂鸡毛碳点荧光关开探针用于测定百草枯

以鸡毛和乙二胺为碳源和氮源,通过一步水热法合成强荧光性能的氮掺杂碳量子点(N-CQDs),并优化其制备和掺杂条件.该碳量子点具有良好的光学、结构性质和稳定性,平均粒径7.89 nm,荧光量子产率为14％.最大激发波长为320 nm,最大发射波长为386 nm.Hg2+存在条件下N-CQDs溶液的荧光被碎灭(关),添加百...     

Magnesium-containing silk fibroin/polycaprolactone electrospun nanofibrous scaffolds for accelerating bone regeneration

Bone tissue engineering has become one of the most effective methods for treating bone defects. In this study, an electrospun tissue engineering membrane containing magnesium was successfully fabricated by incorporating magnesium oxide (MgO) nanoparticles into silk fibroin and polycaprolactone (SF/PCL)-blend scaffolds. The release kinetics of Mg²⁺ and the effects of magnesium on scaffold morphology, and cellular behavior were investigated. The obtained Mg-functionalized nanofibrous scaffolds displayed controlled release of Mg²⁺, satisfactory biocompatibility and osteogenic capability. The in vivo implantation of magnesium-containing electrospun nanofibrous membrane in a rat calvarial defect resulted in the significant enhancement of bone regeneration twelve weeks post-surgery. This work represents a valuable strategy for fabricating functional magnesium-containing electrospun scaffolds that show potential in craniofacial and orthopedic applications.     

Electrically conductive carbon nanofiber/polyethylene composite: effect of melt mixing conditions

The effect of melt mixing conditions on the morphological, rheological, electrical, electromagnetic interference (EMI) shielding effectiveness (SE), and tensile properties of 7.5 vol% vapor grown carbon nanofiber (VGCNF)/polyethylene composites were investigated. 7.5 vol% VGCNF was used because such loading is required to obtain a composite with satisfactory EMI SE. The composites were compounded by melt mixing and the parts were prepared by hot‐compression molding. The dispersion and distribution of nanofibers were enhanced by increasing the mixing energy, i.e. mixing time and/or rotation speed. The influence of mixing energy on the electrical and EMI SE properties was found to be a function of rotation speed, i.e. shear stress. For composites compounded at 20 rpm, increasing the mixing energy from 70 to 2300 J/ml decreased the EMI SE from 29.5 to 23.9 dB. However, for composites prepared at 100 rpm, increasing the mixing energy from 600 to 1700 J/ml decreased the EMI SE from 25.4 to 18.6 dB. No considerable influence on the yield stress, Young's modulus, and strain at break were found for different processing conditions. Copyright © 2009 John Wiley & Sons, Ltd.     

Microwave-assisted one-pot conversion from deoiled asphalt to green fluorescent graphene quantum dots and their interfacial properties

High-quality graphene quantum dots (GQDs) were prepared through a facile route of microwave-assisted one-step mild oxidation of cheap deoiled asphalt (DOA). The as-prepared DOA-derived GQDs dissolved in water with a much smaller and thinner size than most of the reported GQDs, and luminesced bright green light by excitation of 365 nm. Furthermore, the GQDs possessed excellent properties of excitation-tuned fluorescence behavior with a high quantum yield up to 16.4%. In addition, the GQDs showed amphipathic properties and could significantly reduce the interfacial tension, which give them great potential as surfactants for asphalt emulsion.     

One-step straightfoward solid synthesis of high yield white fluorescent carbon dots for white light emitting diodes

Herein,we directly prepared white fluorescent CDs(W-CDs) using 1,6-dihydroxynaphthalene(1,6-DHN)and L-asparagine(L-Asn) as carbon sources through a simple solvent-free method.As-prepared W-CDs can be obtained in high yield(95%).A relative pure white LEDs(WLEDs) were fabricated with Commission Internationale de Eclairage(CIE) coordinates of(0.32,0.31).As-prepared W-CDs will have promising future for a wide range of optoelectronic devices.     

One-pot electrochemical synthesis of functionalized fluorescent carbon dots and their selective sensing for mercury ion

We propose a simple, economical, and one-pot method to synthesize water-soluble functionalized fluorescent carbon dots (C-Dots) through electrochemical carbonization of sodium citrate and urea. The as-prepared C-Dots have good photostability and exhibit a high quantum yield of 11.9%. The sizes of the C-Dots are mainly distributed in the range of 1.0–3.5 nm with an average size of 2.4 nm. It has been further used as a novel label-free sensing probe for selective detection of Hg²⁺ ions with detection limit as low as 3.3 nM. The detection linear range is 0.01–10 μM. The as-prepared C-Dots are also successfully applied for the determination of Hg²⁺ in real water samples.     

可视化辅助碳点荧光比色法检测水中痕量汞离子

利用巯基功能化碳点(M-CDs)构建用于检测水中Hg^2+的荧光探针。红外光谱证实M-CDs被巯基(-SH)成功修饰,透射电镜显示M-CDs的平均粒径约为4.88 nm。XRD晶型表征显示M-CDs具有类石墨烯结构。由于银硫醇盐的团聚作用,M-CDs溶液中加入Ag^+可快速形成M-CDs/Ag的棕色沉淀,并引起M-CDs的荧光猝灭。用PBS缓冲液(0.01 mol/L,pH 7.4)溶解沉淀物而形成检测Hg^2+的荧光传感器。在传感体系中加入Hg^2+后,M-CDs荧光明显恢复。在Hg^2+浓度为0.01~0.55 nmol/L范围内,检测体系荧光恢复强度与Hg^2+浓度成良好线性关系,检测限(LOD,3σ/k)4.2 pmol/L。该探针对Hg^2+表现出良好的选择性,同时可以通过可视化辅助判断探针的选择性。该传感器可用于对实际水样的检测,为Hg^2+污染监测提供技术依据。     

Thiourea functionalized CdSe/CdS quantum dots as a fluorescent sensor for mercury ion detection

CdSe/CdS quantum dots(QDs) functionalized by thiourea(TU) were synthesized and used as a fluorescent sensor for mercury ion detection.The TU-functionalized QDs were prepared by bonding TU via electrostatic interaction to the core/shell CdSe/CdS QDs after capping with thioglycolic acid(TGA).It was observed that the fluorescence of the functionalized QDs was quenched upon the addition of Hg~(2+).The quantitative detection of Hg~(2+) with this fluorescent sensor could be conducted based on the linear relationship between the extent of quenching and the concentration of Hg~(2+) added in the range of1-300 μg L~(-1).A detection limit of 0.56 μg L~(-1) was achieved.The sensor showed superior selectivity for Hg~(2+) and was successfully applied to the determination of mercury in environmental samples with satisfactory results.     

Highly fluorescent carbon dots from peanut shells as potential probes for copper ion: The optimization and analysis of the synthetic process

The use of natural materials, a renewable resource, instead of chemicals as carbon precursors for simple synthesis of fluorescent carbon dots (FCDs) remains a significant challenge. Here, we report the preparation of FCDs with a photoluminescence (PL) quantum yield (QY) of 10.58% from peanut shells via one-pot pyrolysis treatment optimized by using a central composite experiment design. Optimum pyrolysis conditions were found to be 400 °C temperature, 4 h duration, and 70 g peanut shell weight. The as-prepared FCDs possess unique excitation-dependent behavior, good water dispersibility and high photostability. The results of Fourier transform infrared (FTIR) spectroscopy to analyze the pyrolytic process indicated the complete combustion of peanut shells happened at 3 and 4 h at 400 °C. The PL intensity of the FCDs was not always proportional to the corresponding QY value in our work due to the different amount of carbon-rich residues after the pyrolysis process. Fluorescence-quenching trials were conducted to analyze their sensitivity and selectivity in Cu²⁺ detection. The detection limit was found to be 4.8 μM. Our pyrolysis treatment of peanut shells for preparing FCDs is not only a green and facile method but also a means of recycling peanut shells.     

氮掺杂荧光碳点用于Co2+的超灵敏检测及细胞成像

首次以金银花和乙二胺为原料,通过水热法合成出性能优异的氮掺杂碳点(N-CDs)。制备的N-CDs具有丰富的官能团、良好的水溶性、低细胞毒性、高的荧光稳定性和良好的生物相容性。在最佳条件下,N-CDs能够高选择性地检出Co²⁺,N-CDs的荧光强度在0.5～3.6 nmol·L^-1范围内被Co²⁺线性猝灭,检出限低至1.38 nmol·L^-1,其猝灭机制属于内滤效应和静态猝灭。该方法也已成功应用于实际样品的精确分析。此外,N-CDs还可用于细胞成像及细胞内Co²⁺传感。     

Ratiometric fluorescence detection of mercuric ion based on the nanohybrid of fluorescence carbon dots and quantum dots

A novel nanohybrid ratiometric fluorescence probe comprised of carbon dots (C-dots) and hydrophilic CdSe@ZnS quantum dots (QDs) has been developed by simply mixing the blue-emission C-dots with red-emission carboxylmethyldithiocarbamate modified CdSe@ZnS QDs (GDTC-QDs). The nanohybrid ratiometric fluorescence probe exhibits dual emissions at 436 nm and 629 nm under a single excitation wavelength. Due to the strong chelating ability of GDTC on the surface of QDs to mercuric ion (Hg²⁺), the fluorescence of the GDTC-QDs in the nanohybrid system could be selectively quenched in the presence of Hg²⁺ while the fluorescence of the C-dots remained constant, resulting in an obviously distinguishable fluorescence color evolution (from red to blue) of the nanohybrid system. The detection limit of this method was found to be as low as 0.1 μM. Furthermore, the recovery result for Hg²⁺ in real samples including tap water and lake water by this method was satisfying, suggesting its potential application for Hg²⁺ sensing.