Hybrid materials in which reduced graphene oxide (rGO) is decorated with Au nanoparticles (rGO–Au NPs) were obtained by the in situ reduction of GO and AuCl4?(aq) by ascorbic acid. On laser excitation, rGO could be oxidized as a result of the surface plasmon resonance (SPR) excitation in the Au NPs, which generates activated O2 through the transfer of SPR‐excited hot electrons to O2 molecules adsorbed from air. The SPR‐mediated catalytic oxidation of p‐aminothiophenol (PATP) to p,p′‐dimercaptoazobenzene (DMAB) was then employed as a model reaction to probe the effect of rGO as a support for Au NPs on their SPR‐mediated catalytic activities. The increased conversion of PATP to DMAB relative to individual Au NPs indicated that charge‐transfer processes from rGO to Au took place and contributed to improved SPR‐mediated activity. Since the transfer of electrons from Au to adsorbed O2 molecules is the crucial step for PATP oxidation, in addition to the SPR‐excited hot electrons of Au NPs, the transfer of electrons from rGO to Au contributed to increasing the electron density of Au above the Fermi level and thus the Au‐to‐O2 charge‐transfer process. 相似文献
We report on a non-covalent functionalization of graphene foam (GF) synthesized via chemical vapour deposition (CVD). The GF was treated with pyrene carboxylic acid (PCA) which acted as a source of oxygen and/or hydroxyl groups attached to the surface of the graphene foam for its electrochemical performance improvement. The modified graphene surface enabled a high pseudocapacitive effect on the GF. A specific capacitance of 133.3 F g?1, power density ~ 145.3 kW kg?1 and energy density ~ 4.7 W h kg?1 were achieved based on the functionalized foam in 6 M KOH aqueous electrolyte. The results suggest that non-covalent functionalization might be an effective approach to overcome the restacking problem associated with graphene electrodes and also signify the importance of surface functionalities in graphene-based electrode materials. 相似文献
The present work describes the development of an amperometric sensor based on hemin immobilized on a titanium oxide modified silica toward detection of artemisinin (ARN) in neutral medium at an applied potential of −0.5 V vs. Ag/AgCl. The sensor presented its best performance in 0.1 mol L−1 phosphate buffer solution, at pH 7.0. After optimizing the operational conditions, the sensor provided a linear response range for ARN reduction from 50 nmol L−1 to 1000 nmol L−1 with a sensitivity, detection and quantification limits of 24.66 A L mol−1, 15 nmol L−1 and 52 nmol L−1, respectively. The proposed sensor showed a stable response for at least 80 successive determinations. The repeatability of the measurements with the sensor and the preparation of a series of electrodes, evaluated in terms of relative standard deviation, were 4.1% and 5.0%, respectively, for n = 10. The developed sensor was applied for the determination of ARN in the crude extracts of A. vulgaris L and the average recovery for these samples is 101.4 (± 3.1)%. 相似文献
The development of delivery systems efficiently uptaken by cells is of due importance since sites of drug action are generally localized in subcellular compartments. Herein, naked and core–shell polymeric nanoparticles (NPs) have been produced from poly(lactic‐co‐glycolic acid)—PLGA, poly(ethylene oxide)‐b‐poly(ε‐caprolactone)—PEO‐b‐PCL, and poly(ethylene oxide)‐b‐poly(lactic acid)—PEO‐b‐PLA. The nanostructures are characterized and the cellular uptake behavior is evaluated. The data evidence that cellular uptake is enhanced as the length of the hydrophilic PEO‐stabilizing shell reduces and that high negative surface charge restricts cellular uptake. Furthermore, NPs of higher degree of hydrophobicity (PEO‐b‐PCL) are more efficiently internalized as compared to PEO‐b‐PLA NPs. Accordingly, taking into account our recent published results 1 and the findings of the current investigation, there should be a compromise regarding protein fouling and cellular uptake as resistance to nonspecific protein adsorption and enhanced cellular uptake are respectively directly and inversely related to the length of the PEO‐stabilizing shell.
The present study describes a simple strategy to integrate electrochemical detection with an assembled microchip‐capillary electrophoresis platform. The electrochemical cell was integrated with a microfluidic device consisting of five plastic squares interconnected with fused silica capillaries, forming a four‐way injection cross between the separation channel and three side‐arms (each of 15 mm in length) acting as buffer/sample reservoirs. The performance of the system was evaluated using electrodes made with either carbon ink, carbon nanotubes, or gold and under different experimental conditions of pH, capillary length, and injection time. Using this system it was possible to separate the neurotransmitters dopamine and cathecol and to quantify phenol from a real sample using a linear calibration curve with a calculated LOD of 0.7 µM. A similar concept was applied to determine glucose, by including a pre‐reactor filled with beads modified with glucose oxidase (GOx). The latter system was used to determine glucose in a commercial sample, with a recovery of 95.2 %. Overall, the presented approach represents a simple, inexpensive, and versatile approach to integrate electrochemical detection with CE separations without requiring access to microfabrication facilities. 相似文献
Nanoparticles of octakis[3-(3-amino-1,2,4-triazole)propyl]octasilsesquioxane (ATZ-SSQ) were tested as ligands for transition-metal ions in aqueous solution with a special attention to sorption isotherms, ligand-metal interaction, and determination of metal ions in natural waters. The adsorption potential of the material ATZ-SSQ was compared with related [3(3-amino-1,2,4-triazole)propyl]silica gel (ATZ-SG). The adsorption was performed using a batchwise process and both organofunctionalized surfaces showed the ability to adsorb the metal ions from aqueous solution. The Langmuir model was used to simulate the sorption isotherms. The results suggest that the sorption of these metals on ATZ-SSQ and ATZ-SG occurs mainly by surface complexation. The equilibrium condition is reached at time lower than 3 min for ATZ-SSQ, while for ATZ-SG is only reached at time of 25 min. The maximum metal ion uptake values for ATZ-SSQ were higher than the corresponding values achieved with the ATZ-SG. In order to obtain more information on the ligand-metal interaction of the complexes on the surface of the ATZ-SSQ nanomaterial, ESR study with various degrees of copper loadings was carried out. The ATZ-SSQ was tested for the determination (in flow using a column technique) of the metal ions present in natural waters. 相似文献
The transport of ions through multiple drift regions is modeled to develop an equation that is useful for an understanding
of the resolving power of an overtone mobility spectrometry (OMS) technique. It is found that resolving power is influenced
by a number of experimental variables, including those that define ion mobility spectrometry (IMS) resolving power: drift
field (E), drift region length (L), and buffer gas temperature (T). However, unlike IMS, the resolving power of OMS is also influenced by the number of drift regions (n), harmonic frequency value (m), and the phase number (Φ) of the applied drift field. The OMS resolving power dependence upon the new OMS variables (n, m, and Φ) scales differently than the square root dependence of the E, L, and T variables in IMS. The results provide insight about optimal instrumental design and operation. 相似文献
A new method that allows a linear drift tube to be operated as a continuous ion mobility filter is described. Unlike conventional
ion mobility instruments that use an electrostatic gate to introduce a packet of ions into a drift region, the present approach
uses multiple segmented drift regions with modulated drift fields to produce conditions that allow only ions with appropriate
mobilities to pass through the instrument. In this way, the instrument acts as a mobility filter for continuous ion sources.
By changing the frequency of the applied drift fields it is possible to tune this instrument to transmit ions having different
mobilities. A scan over a wide range of drift field frequencies for a single ion species shows a peak corresponding to the
expected resonance time of the ions in one drift region segment and a series of peaks at higher frequencies that are overtones
of the resonant frequency. The measured resolving power increases for higher overtones, making it possible to resolve structures
that were unresolved in the region of the fundamental frequency. We demonstrate the approach by examining oligosaccharide
isomers, raffinose and melezitose as well as a mixture of peptides obtained from enzymatic digestion of myoglobin. 相似文献