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Clean Synthesis of an Economical 3D Nanochain Network of PdCu Alloy with Enhanced Electrocatalytic Performance towards Ethanol Oxidation. - Chemistry (Weinheim an der Bergstrasse, Germany)
A one-pot method for the fast synthesis of a 3D nanochain network (NNC) of PdCu alloy without any surfactants is described. The composition of the as-prepared PdCu alloy catalysts can be precisely controlled by changing the precursor ratio of Pd to Cu. First, the Cu content changes the electronic structure of Pd in the 3D NNC of PdCu alloy. Second, the 3D network structure offers large open pores, high surface areas, and self-supported properties. Third, the surfactant-free strategy results in a relatively clean surface. These factors all contribute to better electrocatalytic activity and durability towards ethanol oxidation. Moreover, the use of copper in the alloy lowers the price of the catalyst by replacing the noble metal palladium with non-noble metal copper. The composition-optimized Pd80 Cu20 alloy in the 3D NNC catalyst shows an increased electrochemically active surface area (80.95â€…m(2) â€‰g(-1) ) and a 3.62-fold enhancement of mass activity (6.16â€…Aâ€‰mg(-1) ) over a commercial Pd/C catalyst.Â© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Universal chitosan-assisted synthesis of Ag-including heterostructured nanocrystals for label-free in situ SERS monitoring. - Nanoscale
A universal chitosan-assisted method was developed to synthesize various Ag-including heterostructured nanocrystals, in which chelation probably plays a vital role. The as-prepared Ag/Pd heterostructured nanocrystals show outstanding properties when used as bifunctional nanocomposites in label-free in situ SERS monitoring of Pd-catalyzed reaction.
Antiviral Activity of Graphene Oxide: How Sharp Edged Structure and Charge Matter. - ACS applied materials & interfaces
Graphene oxide and its derivatives have been widely explored for their antimicrobial properties due to their high surface-to-volume ratios and unique chemical and physical properties. However, little information is available on their effects on viruses. In this study, we report the broad-spectrum antiviral activity of GO against pseudorabies virus (PRV, a DNA virus) and porcine epidemic diarrhea virus (PEDV, an RNA virus). Our results showed that GO significantly suppressed the infection of PRV and PEDV for a 2 log reduction in virus titers at noncytotoxic concentrations. The potent antiviral activity of both GO and rGO can be attributed to the unique single-layer structure and negative charge. First, GO exhibited potent antiviral activity when conjugated with PVP, a nonionic polymer, but not when conjugated with PDDA, a cationic polymer. Additionally, the precursors Gt and GtO showed much weaker antiviral activity than monolayer GO and rGO, suggesting that the nanosheet structure is important for antiviral properties. Furthermore, GO inactivated both viruses by structural destruction prior to viral entry. The overall results suggest the potential of graphene oxide as a novel promising antiviral agent with a broad and potent antiviral activity.
Facile Synthesis of Quasi-One-Dimensional Au/PtAu Heterojunction Nanotubes and Their Application as Catalysts in an Oxygen-Reduction Reaction. - Chemistry (Weinheim an der Bergstrasse, Germany)
An intermediate-template-directed method has been developed for the synthesis of quasi-one-dimensional Au/PtAu heterojunction nanotubes by the heterogeneous nucleation and growth of Au on Te/Pt core-shell nanostructures in aqueous solution. The synthesized porous Au/PtAu bimetallic nanotubes (PABNTs) consist of porous tubular framework and attached Au nanoparticles (AuNPs). The reaction intermediates played an important role in the preparation, which fabricated the framework and provided a localized reducing agent for the reduction of the Au and Pt precursors. The Pt7 Au PABNTs showed higher electrocatalytic activity and durability in the oxygen-reduction reaction (ORR) in 0.1â€‰M HClO4 than porous Pt nanotubes (PtNTs) and commercially available Pt/C. The mass activity of PABNTs was 218â€‰% that of commercial Pt/C after an accelerated durability test. This study demonstrates the potential of PABNTs as highly efficient electrocatalysts. In addition, this method provides a facile strategy for the synthesis of desirable hetero-nanostructures with controlled size and shape by utilizing an intermediate template.Â© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Optimized extraction of polysaccharides from Taxus chinensis var. mairei fruits and its antitumor activity. - International journal of biological macromolecules
The simultaneous ultrasonic/microwave-assisted extraction (UMAE) method is potentially useful for the extraction of polysaccharides from Taxus chinensis var. mairei fruits (TCFPs). In this study, we used a response surface methodology to identify optimal TCFPs extraction conditions. Optimal parameters were determined as follows: a liquid to raw material ratio of 33 mL/g, an extraction time of 10 min, a microwave power level of 560 W, and a fixed ultrasonic power of 50 W. Under the optimized conditions, TCFPs yields obtained by UMAE were 4.33 Â± 0.15%, a 1.79-fold increase compared with conventional heating reflux extraction (HRE). In addition, the extraction time used in UMAE was shorter than that required for HRE: 10 versus 90 min. UMAE is therefore a rapid and efficient method for the extraction of TCFPs. The inhibitory effect of TCFPs on S180 tumor growth in vivo was also studied. The tumor inhibition rate of TCFPs was 76.33%, indicating a tumor-inhibiting effect. Analysis of organ weights demonstrated that TCFPs exhibited no toxicity to liver, kidney, spleen, heart, or lung relative to a positive control group. TCFPs thus show antitumor activity with no organ toxicity.Copyright Â© 2015 Elsevier B.V. All rights reserved.
Two-dimensional colloidal crystal assisted formation of conductive porous gold films with flexible structural controllability. - Journal of colloid and interface science
Two-dimensional (2D) colloidal crystals of polystyrene (PS) particles were used as a structure-controlling template to fabricate conductive Au films with an ordered array of nanoholes. The fabrication mainly involved the functionalization of the supporting substrate with polyelectrolyte (PE) functional layers, self-assembly of Au nanoparticles, and electroless deposition of gold. The self-assembly of Au nanoparticles and electroless deposition of gold were macroscopically monitored using ultraviolet-visible (UV-vis) spectroscopy based on the changes in both the extinction spectra of Au nanoparticles and the optical responses of ordered arrays of PS particles. By scanning electron microscopy (SEM) characterization, it was found that Au nanoparticles were assembled into a film structure with orderly dispersed nanoholes and the deposition of gold was confined to the preformed Au nanoparticle films. During the formation of Au films, PE layer structure, Au nanoparticle size and heating treatment applied to the PS template could influence the structures of conductive porous Au films such as the hole diameter, film thickness, and hole diameter/wall thickness ratio (D/W). In addition, this paper also described electrochemical cyclic voltammetry (CV) employed to demonstrate the porosity of the ultimate Au films.Copyright Â© 2014 Elsevier Inc. All rights reserved.
Ionic-liquid-based ultrasound/microwave-assisted extraction of 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one and 6-methoxy-benzoxazolin-2-one from maize (Zea mays L.) seedlings. - Journal of separation science
We evaluated an ionic-liquid-based ultrasound/microwave-assisted extraction method for the extraction of 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one and 6-methoxy-benzoxazolin-2-one from etiolated maize seedlings. We performed single-factor and central composite rotatable design experiments to optimize the most important parameters influencing this technique. The best results were obtained using 1.00 M 1-octyl-3-methylimidazolium bromide as the extraction solvent, a 50Â°C extraction temperature, a 20:1 liquid/solid ratio (mL/g), a 21 min treatment time, 590 W microwave power, and 50 W fixed ultrasonic power. We performed a comparison between ionic-liquid-based ultrasound/microwave-assisted extraction and conventional homogenized extraction. Extraction yields of 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one and 6-methoxy-benzoxazolin-2-one by the ionic-liquid-based ultrasound/microwave-assisted extraction method were 1.392 Â± 0.051 and 0.205 Â± 0.008 mg/g, respectively, which were correspondingly 1.46- and 1.32-fold higher than those obtained by conventional homogenized extraction. All the results show that the ionic-liquid-based ultrasound/microwave-assisted extraction method is therefore an efficient and credible method for the extraction of 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one and 6-methoxy-benzoxazolin-2-one from maize seedlings.Â© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Optimization of ionic liquid based simultaneous ultrasonic- and microwave-assisted extraction of rutin and quercetin from leaves of velvetleaf (Abutilon theophrasti) by response surface methodology. - TheScientificWorldJournal
An ionic liquids based simultaneous ultrasonic and microwave assisted extraction (ILs-UMAE) method has been proposed for the extraction of rutin (RU), quercetin (QU), from velvetleaf leaves. The influential parameters of the ILs-UMAE were optimized by the single factor and the central composite design (CCD) experiments. A 2.00 M 1-butyl-3-methylimidazolium bromide ([C4mim]Br) was used as the experimental ionic liquid, extraction temperature 60Â°C, extraction time 12 min, liquid-solid ratio 32 mL/g, microwave power of 534 W, and a fixed ultrasonic power of 50 W. Compared to conventional heating reflux extraction (HRE), the RU and QU extraction yields obtained by ILs-UMAE were, respectively, 5.49 mg/g and 0.27 mg/g, which increased, respectively, 2.01-fold and 2.34-fold with the recoveries that were in the range of 97.62-102.36% for RU and 97.33-102.21% for QU with RSDs lower than 3.2% under the optimized UMAE conditions. In addition, the shorter extraction time was used in ILs-UMAE, compared with HRE. Therefore, ILs-UMAE was a rapid and an efficient method for the extraction of RU and QU from the leaves of velvetleaf.
Hydrogen-bonding recognition-induced aggregation of gold nanoparticles for the determination of the migration of melamine monomers using dynamic light scattering. - Analytica chimica acta
The migration of melamine monomers from food contact materials has aroused particular attention since the 2008 melamine-tainted milk scandal in China. However, the determination of melamine monomer's migratory quantity (MMMQ) has remained an open question because of the complex sample pretreatment and the low sensitivity. Based on the hydrogen bonding interaction between DNA thymine and melamine, this paper described a simple and rapid method focusing on the measurement of MMMQ from melamine tableware by gold nanoparticles (GNPs) and dynamic light scattering (DLS). With the presence of probe DNA (p-DNA), the GNPs were stable in NaCl solution (0.06 M), whereas they became aggregated when the p-DNA hybridized with melamine. The change in the hydrodynamic diameter of GNPs could be detected by DLS technology. Under the optimal conditions, the average diameter increased linearly with the concentration of melamine over the range from 5.0 to 320.0 Î¼g L(-1), and showed a detection limit of 2.0 Î¼g L(-1) (3Ïƒ/slope). The MMMQ was investigated within a range from 6.00Ã—10(-4) to 2.58Ã—10(-1) mg dm(-2) (nâ‰¥3) in four different food simulants at different temperatures and time points. The results suggest that the DLS method has great potential in the analysis of the migration of melamine monomers.Copyright Â© 2014 Elsevier B.V. All rights reserved.
Target triggered self-assembly of Au nanoparticles for amplified detection of Bacillus thuringiensis transgenic sequence using SERS. - Biosensors & bioelectronics
The research methods for DNA detection have been widely extended since the application of nanotechnology, but it remains a challenge to detect specific DNA sequences or low abundance genes in the biological samples with accuracy and sensitivity. Here we developed a SERS biosensing platform by target DNA (tDNA) triggered self-assembly of Au nanoparticles (Au NPs) probes on DNA nanowires for signal amplification in DNA analysis. Based on the hybridization chain reactions (HCR) and surface enhanced Raman scattering (SERS) technology, the SERS intensity reveals a good linearity with tDNA ranging from 50 pM to 500 pM under optimal conditions. The specific detection of tDNA sequence was realized with a detection limit of 50 pM (S/N=3). To demonstrate the specificity and universality of the strategy, the single-base mismatches in DNA and the Bacillus thuringiensis (Bt) transgenic sequence were successively applied in the SERS assay. The results showed that the sensitivity and accuracy of the SERS-based assay were comparable with real-time PCR. Besides, the method would provide precise and ultra-sensitive detection of tDNA but also informative supplement to the SERS biosensing platform.Copyright Â© 2014 Elsevier B.V. All rights reserved.
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