Separation of benzo[a]pyrene and <Emphasis Type="Italic">n</Emphasis>-tetradecane mixtures using pervaporation technique and optimization

Benzo[a]pyrene is a carcinogen often present in diesel. For pervaporative removal of benzo[a]pyrene from n-tetradecane, representing a model diesel composition, both conventional as well as statistically designed experimental methods have been carried out. The effect of membrane composition, thickness, the effect of membrane pretreatment time and operating temperature on pervaporative separation have been investigated by response surface methodology, RSM for efficient permeation of target compound. The suitable membrane has been further used to study the effect of different physico-chemical parameters on permeation conventionally. RSM has also been applied to optimize the operational conditions of pervaporation process to maximize the response, i.e., the pervaporation separation index. With the design of experiments, the quadratic response surface models have been developed to link the response with input variables via mathematical relationships. The maximum value of Pervaporation Separation Index obtained is 1.9654 kg m^?2 h^?1. The optimized process condition’s run time is 10.79 h, the feed PAH concentration is 166.34 ppm with a permeate side pressure of 0.73 mmHg and an operating temperature of 451.25 K.     

Photoquantum Hall Effect and Light‐Induced Charge Transfer at the Interface of Graphene/InSe Heterostructures

The transfer of electronic charge across the interface of two van der Waals crystals can underpin the operation of a new class of functional devices. Among van der Waals semiconductors, an exciting and rapidly growing development involves the “post‐transition” metal chalcogenide InSe. Here, field effect phototransistors are reported where single layer graphene is capped with n‐type InSe. These device structures combine the photosensitivity of InSe with the unique electrical properties of graphene. It is shown that the light‐induced transfer of charge between InSe and graphene offers an effective method to increase or decrease the carrier density in graphene, causing a change in its resistance that is gate‐controllable and only weakly dependent on temperature. The charge transfer at the InSe/graphene interface is probed by Hall effect and photoconductivity measurmentes and it is demonstrated that light can induce a sign reversal of the quantum Hall voltage and photovoltaic effects in the graphene layer. These findings demonstrate the potential of light‐induced charge transfer in gate‐tunable InSe/graphene phototransistors for optoelectronics and quantum metrology.     

The Mechanisms of Rectification in Au|Molecule|Au Devices Based on Langmuir–Blodgett Monolayers of Iron(III) and Copper(II) Surfactants

Langmuir–Blodgett films of metallosurfactants were used in Au|molecule|Au devices to investigate the mechanisms of current rectification.     

Application of high performance liquid chromatography coupled to on-line solid-phase extraction-nuclear magnetic resonance spectroscopy for the analysis of degradation products of V-class nerve agents and nitrogen mustard

The detection and identification of the degradation products of nitrogen mustard and nerve agent VX by high performance liquid chromatography coupled to on-line solid-phase extraction-nuclear magnetic resonance spectroscopy (HPLC-UV-SPE-NMR) were demonstrated. The analytes selected for the study were N,N-dimethylaminoethanol (DMAE), N,N-diethylaminoethanol (DEAE), N,N-diisopropylaminoethanol (DIAE) and triethanolamine (TEA). Offline solid-phase extraction (SPE) followed by derivatization was applied to eliminate the interferents and make the analytes amenable for UV detection. Thereafter, chromatographically separated derivatives were trapped on on-line SPE cartridges. They were subsequently eluted and ¹H NMR and COSY spectra were obtained. The overall detection limits of the LC-UV-SPE-NMR method for the mentioned analytes were found to be 18, 23, 25, and 32 mg/L respectively. Applicability of the method to real samples was demonstrated by the analysis of samples provided during the 22nd OPCW official proficiency test. The method gave reproducible NMR spectra devoid of intense background signals.     

Markov chain model for performance analysis of transmitter power control in contention based wireless MAC protocol

We have developed a three-state discrete-time Markov-chain model for the performance evaluation of contention-based medium access control (MAC) protocol. The proposed Markov-chain model is then used to analyze the carrier sense multiple access (CSMA) type MAC protocol for its delay and throughput characteristics with and without transmitter power control. Using simulations, the conditional capture probability (p _cap ), which gives a measure of the effectiveness of transmitter power control due to the capture effect, is quantified and experiments are performed to validate these simulated data for the p _cap . To analyze the effect of transmitter power variation, the Markov-chain model is modified by incorporating the p _cap . Numerical results show significant throughput as well as delay performance improvement using transmitter power control.     

Polyurea microcapsules: Surface modification and capsule size control

A postmodification method for polyurea microcapsule (PUMC) surfaces using functional polyelectrolytes is reported in this article. Fluorescein isothiocyanate (FITC) was used to probe the chemistry on PUMC surface and label nucleophilic groups on the surface, in particular amines. As well, a fluorescently labeled polyanion containing electrophilic acetoacetate groups was used to covalently react with these nucleophilic groups on the PUMC surfaces. This modification causes charge reversion of the originally cationic PUMC and enables subsequent layer‐by‐layer (LbL) coating using other polyelectrolytes, allowing for covalent or noncovalent modification of the capsule surface. All modification steps were monitored using either laser scanning confocal microscopy or fluorescence microscopy. Optical and fluorescence microscopy of PUMC wall cross‐sections embedded in resin confirmed that the modifications were restricted to the outer surface of PUMCs, offering minimum interference of this modification method with other capsule wall properties. In addition, a simple T‐junction type microfluidic device based on a commercially available MicroTEE was designed to produce narrowdisperse PUMCs. This device was easy to set up and operate and was proved to be an useful tool for making monodisperse emulsions and narrowdisperse MCs. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Recent Development of Active Nanoparticle Catalysts for Fuel Cell Reactions

This review focuses on the recent advances in the synthesis of nanoparticle (NP) catalysts of Pt‐, Pd‐ and Au‐based NPs as well as composite NPs. First, new developments in the synthesis of single‐component Pt, Pd and Au NPs are summarized. Then the chemistry used to make alloy and composite NP catalysts aiming to enhance their activity and durability for fuel cell reactions is outlined. The review next introduces the exciting new research push in developing CoN/C and FeN/C as non‐Pt catalysts. Examples of size‐, shape‐ and composition‐dependent catalyses for oxygen reduction at cathode and formic acid oxidation at anode are highlighted to illustrate the potentials of the newly developed NP catalysts for fuel cell applications.