Aerobic oxidation of 5-hydroxymethylfurfural (HMF) effectively catalyzed by a Ce0.8Bi0.2O2-delta supported Pt catalyst at room temperature

The oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) was efficiently catalyzed when Pt nanoparticles (NPs) were supported onto a Ce0.8Bi0.2O2-delta solid solution. 98% yield of FDCA was achieved within 30 min at room temperature and the catalyst was reused five times without much loss of FDCA selectivity. It is the first report on the oxidation of HMF, an alcohol and an aldehyde, effectively catalyzed by a ceria-based material supported Pt catalyst. The individual properties of the Pt NPs and the ceria-based support were retained and not affected after their combination. The superior oxygen activation ability of the Bi-doped ceria thoroughly changed the performance of the ceria supported Pt catalyst. Pt NPs were responsible for the formation of the Pt-alkoxide intermediate, followed by beta-H elimination with the help of hydroxide ions. Bi-containing ceria accelerated the oxygen reduction process because of the presence of a large amount of oxygen vacancies and the cleavage of the peroxide intermediate promoted by bismuth. These specific functions were well incorporated during the catalytic oxidation cycle, leading to the generation of the highly efficient Pt/Ce0.8Bi0.2O2-delta catalyst for HMF oxidation at room temperature

Visible-light-driven enhanced antibacterial and biofilm elimination activity of graphitic carbon nitride by embedded Ag nanoparticles

Semiconductor nanomaterials with photocatalytic activity have potential for many applications. An effective way of promoting photocatalytic activity is depositing noble metal nanoparticles (NPs) on a semiconductor, since the noble metal NPs act as excellent electron acceptors which inhibit the quick recombination of the photoexcited electron-hole pairs and thereby enhance the generation of reactive oxygen species (ROS). Herein, a highly effective platform, graphitic carbon nitride (g-C3N4) nanosheets with embedded Ag nanoparticles (Ag/g-C3N4), was synthesized by a facile route. Under visible light irradiation, the ROS production of Ag/g-C3N4 nanohybrids was greatly improved compared with pristine g-C3N4 nanosheets, and moreover, the nanohybrids showed enhanced antibacterial efficacy and ability to disperse bacterial biofilms. We demonstrate for the first time that the Ag/g-C3N4 nanohybrids are efficient bactericidal agents under visible light irradiation, and can also provide a new way for biofilm elimination. The enhanced antibacterial properties and biofilm-disrupting ability of Ag/g-C3N4 nanohybrids may offer many biomedical applications

Multifunctional electrospinning composite fibers for orthotopic cancer treatment in vivo

A multifunctional, dual-drug carrier platform was successfully constructed. Core-shell structured NaGdF4:Yb/Er@ NaGdF4:Yb@mSiO(2)-polyethylene glycol (abbreviated as UCNPS) nanoparticles loaded with the antitumor drug, doxorubicin (DOX) were incorporated into poly(epsilon-caprolactone) (PCL) and gelatin loaded with antiphlogistic drug, indomethacin (MC) to form nanofibrous fabrics (labeled as MC/UCNPS/DOX) via electrospinning process. The resultant multifunctional spinning pieces can be surgically implanted directly at the tumor site of mice as an orthotopic chemotherapy by controlled-release DOX from mesoporous silicon dioxide (SiO2) and upconversion fluorescence/magnetic resonance dual-model imaging through NaGdF4:Yb/Er@NaGdF4:Yb embedded in MC/UCNPS/DOX in vivo

Virus-templated FRET platform for the rational design of ratiometric fluorescent nanosensors

We report here the construction of a bacteriophage M13-templated supramolecular nanosystem, i.e. M13-beta-CD/Ada-FITC/Ada-RhB, which can be used as effective ratiometric fluorescent sensors for intracellular sensing

Fabrication of biomembrane-like films on carbon electrodes using alkanethiol and diazonium salt and their application for direct electrochemistry of myoglobin

Alkanethiols generally form self-assembled monolayers on gold electrodes and the electrochemical reduction of aromatic diazonium salts is a popular method for the covalent modification of carbon. Based on the reaction of alkanethiol with aldehyde groups covalently bound on carbon surface by the electrochemical reduction of aromatic diazonium salts, a new strategy for the modification of carbon electrodes with alkanethiols has been developed. The modification of carbon surface with aldehyde groups is achieved by the electrochemical reduction of aromatic diazonium salts in situ electrogenerated from a nitro precursor, p-nitrophenylaldehyde, in the presence of nitrous acid. By this way, in situ electrogenerated p-aminophenyl aldehyde from p-nitrophenylaldehyde immediately reacts with nitrous acid, effectively minimizing the side reaction of amine groups and aldehyde groups. The as-prepared alkanethiol-modified glassy carbon electrode was further used to make biomembrane-like films by casting didodecyldimethylammonium bromide on its surface. The biomembrane-like films enable the direct electrochemistry of immobilized myoglobin for the detection of hydrogen peroxide. The response is linear over the range of 1-600 mu M with a detection limit of 0.3 mu M. (C) 2014 Elsevier B.V. All rights reserved

Highly sensitive and selective colorimetric detection of glutathione based on Ag [I] ion-3,3 ',5,5 '-tetramethylbenzidine (TMB)

Glutathione (GSH) plays an important role in the biological system and serves many cellular functions. Since all of the biothiols possess similar functional groups, it is still challenging to selectively detect GSH over cysteine (Cys) and homocysteine (Hcy). In this work, a novel and simple colorimetric method for discriminative detection of glutathione (GSH) over Cys and Hcy is developed. The proposed method is based on the fact that Ag [I] ion could oxidize 3,3',5,5',-tetramethylbenzidine (TMB) to the oxidized TMB to induce a blue color and an absorption peak centered at 652 nm. However, the introduction of GSH could cause the reduction of oxidized TMB and it could also combine with Ag+, both of which result in a blue color fading and a decrease of the absorbance at 652 nm. Based on this finding, we propose a method to qualitatively and quantitatively detect GSH by naked eyes and UV-vis spectroscopy, respectively. The proposed method shows a low detection limit of 0.1 mu M by naked eyes and 0.05 mu M with the help of UV-vis spectroscopy. In addition, this method has great potential in discriminatively detecting GSH over other amino acid and biothiols. More importantly, this method is simple and fast without the preparation of nanomaterials and has also been successfully applied to the detection of GSH in biological fluids. (C) 2014 Elsevier B.V. All rights reserved

In Situ Growth of Surfactant-Free Gold Nanoparticles on Nitrogen-Doped Graphene Quantum Dots for Electrochemical Detection of Hydrogen Peroxide in Biological Environments

In this work, we report a green and simple strategy for the in situ growth of surfactant-free Au nanoparticles (Au NPs) on nitrogen-doped graphene quantum dots (Au NPs-N-GQDs). The formation of hybrid was achieved by just mixing the N-GQDs and HAuCl4 center dot 4H(2)O without addition of any other reductant and surfactant. High-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) characterizations clearly showed the formation of Au nanoparticles with predominantly exposed (111) facets which can provide more adsorption sites. Such nonsurfactant-capped Au NPs can provide naked catalytic surface with highly electrocatalytic activity. The Au NPs-N-GQDs exhibit high sensitivity and selectivity for electrochemical detection of hydrogen peroxide (H2O2) with a low detection limit of 0.12 mu M and sensitivity of 186.22 mu A/mM cm(2). Importantly, the Au NPs-N-GQDs-based electrochemical biosensor has shown great potential applications for detection of H2O2 levels in human serum samples and that released from human cervical cancer cells with satisfactory results. The present study demonstrates that such novel Au NPs-N-GQDs nanocomposite is promising for fabrication of nonenzymatic H2O2 biosensors

以活性为导向的黄酮类化合物分离制备及质谱鉴定研究

中药化学成分是中药发挥药效作用的物质基础，对其进行深入的研究是中药现代化和科学化的关键，因此也是人们研究的热点和重点问题。超滤质谱筛选方法是集筛选及结构鉴定于一体的活性筛选方法，特别适用于复杂体系中活性成分的筛选研究。利用该方法从天然产物的复杂体系中筛选出具有特定生物活性的化合物，再以此为导向从复杂体系分离制备活性成分，不仅减少了从复杂的天然产物体系中分离、鉴定单体化合物所需的工作量，同时也克服了传统天然药物分离工作中存在的局限性和盲目性问题。这对阐明中药药效物质基础和作用机理具有非常重要的意义，也为天然药物的研发提供了一定的理论和应用价值。 基于该研究理念，本论文将超滤质谱技术与高速逆流色谱（HPCCC）、快速制备色谱（RP-MPLC）联合使用，以活性筛选为导向，从三种富含黄酮类成分的传统中药——黄芩、卷柏和银杏中分离制备潜在的黄嘌呤氧化酶（XOD）和α-葡萄糖苷酶抑制剂，并应用质谱及酶...Chemical ingredients in Chinese medicines are considered the material basis to play the role of efficacy, in order to improve the process of modernization and scientific of Chinese medicine, it is crucial to study chemical ingredients in Chinese medicines thoroughly. Nowadays, this research is also a hot and key field. Ultrafiltration liquid chromatography with photodiode array detection coupled to electrospray ionization tandem mass spectrometry (Ultrafiltration LC-PDA-ESI/MS) combines the activity screening and structure identification for one step, which is especially suitable to screen active ingredients from complex system. Therefore, Ultrafiltration LC-PDA-ESI/MS is applied to screen specific biological activity compounds from a complex system of natural products, then isolation and ..

锑基双钙钛矿氧化物的研究进展

系统地总结了双钙钛矿氧化物的晶体结构特点,根据阳离子有序性的不同将双钙钛矿材料分为3类,即岩盐有序、柱状有序和层状有序,并分析了各类有序的形成条件;从B位含有非磁性阳离子的角度入手,介绍了锑基双钙钛矿氧化物的晶体结构特点及其易获得高度B位岩盐有序的机制,并以几种典型的锑基双钙钛矿氧化物为例讨论了该类氧化物的磁、电性质,特别是B位有序度等晶体结构的改变对该类氧化物物理性质的影响。最后介绍了关于A位为不同稀土离子、B位含锑双钙钛矿氧化物的最新研究工作,研究结果表明随着A位稀土离子的替换介电常数ε’值呈单调递减的趋势,说明镧系收缩抑制了过渡金属离子之间的3d电子的跃迁从而抑制极化畴的翻转;对于B位为不同过渡金属元素的化合物,介电常数ε’值按照磁矩减小的趋势呈单调递减规律,反映了磁性与介电性质之间存在着一定的耦合关系,这对更加深入地研究和探索双钙钛矿氧化物材料的磁电性质提供了有价值的参考信息

双组分加成型硅橡胶交联固化过程的流变学研究

采用流变学方法研究了双组分加成型硅橡胶的交联固化过程,并研究了反应温度对反应速率的影响.随着加成反应的进行,体系中的交联程度逐渐增加;反应温度升高,硅橡胶完全交联固化所需时间减少