An in situ electrochemical fabrication of layer by layer graphenized graphite polyaniline as a stable solid‐phase microextraction fiber coating for trace environmental analysis

A layer by layer graphenized graphite/polyaniline coating was fabricated on commercial pencil lead substrate by an in situ facile, fast and efficient electrochemical procedure. The electrodeposited polyaniline film on surface‐confined graphene structure can integrate the advantages of the both layers and was used for solid‐phase microextraction. Effective experimental parameters in electrochemical production of graphene nanosheets and electropolymerization of aniline were optimized. The prepared fiber was used for extraction and determination of four polycyclic aromatic hydrocarbons: phenanthrene, anthracene, fluoranthene and pyrene in aqueous samples by high performance liquid chromatography. The fiber coating was characterized by Fourier transform infrared spectroscopy, X‐ray diffraction and scanning electron microscopy. Under the optimized conditions, the coating provided good linear ranges (0.10–25 μg/L for phenanthrene, 0.05–12.5 μg/L for anthracene, 0.825–99 μg/L for fluoranthene and 0.625–75 μg/L for pyrene (R² = 0.999)) and limits of detection, 0.016 to 0.275 μg/L. The produced coating has several attractive features such as high stability, low cost and long operation time.     

Thermal analysis of nanofluids in microfluidics using an infrared camera

We present the thermal analysis of liquid containing Al(2)O(3) nanoparticles in a microfluidic platform using an infrared camera. The small dimensions of the microchannel along with the low flow rates (less than 120 μl min(-1)) provide very low Reynolds numbers of less than 17.5, reflecting practical parameters for a microfluidic cooling platform. The heat analysis of nanofluids has never been investigated in such a regime, due to the deficiencies of conventional thermal measurement systems. The infrared camera allows non-contact, three dimensional and high resolution capability for temperature profiling. The system was studied at different w/w concentrations of thermally conductive Al(2)O(3) nanoparticles and the experiments were in excellent agreement with the computational fluid dynamics (CFD) simulations.     

Dielectrophoresis for manipulation of micro/nano particles in microfluidic systems

Dielectrophoretic (DEP) force is exerted when a neutral particle is polarized in a non-uniform electric field, and depends on the dielectric properties of the particle and the suspending medium. The integration of DEP and microfluidic systems offers numerous applications for the separation, trapping, assembling, transportation, and characterization of micro/nano particles. This article reviews the applications of DEP forces in microfluidic systems. It presents the theory of dielectrophoresis, different configurations, and the applications of such systems for particle manipulation and device fabrication.     

Novel tuneable optical elements based on nanoparticle suspensions in microfluidics

This work demonstrates the application of dielectrophoretic (DEP) control of silica nanoparticles to form tuneable optical elements within a microfluidic system. The implementation consisted of a microfluidic channel with an array of curved microelectrodes along its base. Various DEP conditions were investigated at alternating current voltage amplitudes, flow rates and frequencies from 5 to 15 V, 2 to 10 μL/min and 0 to 20 MHz, respectively. The fluid channel was filled with deionized water suspending silica particles with diameters of 230 and 450 nm. Experiments were conducted to demonstrate DEP concentration and deflection of the particles and the impact of these particles distributions on the optical transmission through the fluid channel. Both confinement and scattering of the light were observed depending on the particle dimensions and the parameters of the DEP excitation. The results of this investigation illustrate the feasibility of DEP control in an optofluidic system and represent a significant step toward the dynamic formation of electrically controlled liquid optical waveguides.     

Palladium‐catalysed reductive carbonylation of aryl halides with iron pentacarbonyl for synthesis of aromatic aldehydes and deuterated aldehydes

The first use of iron pentacarbonyl is described for the novel and efficient conversion of aryl iodides, bromides and chlorides into their corresponding aryl aldehydes and/or aryl deuterated aldehydes. The reaction is catalysed with Pd(0) in aqueous N,N‐dimethylformamide at atmospheric pressure. In this protocol, neither gaseous hydrogen nor any reducing agent is required for the formation of the carbonylated product. The reaction can be performed without a P(III) ligand for aryl iodides; however, employing a P(III) ligand is necessary to perform the reaction with aryl bromides and chlorides. Copyright © 2015 John Wiley & Sons, Ltd.     

Assessment of Luminescent Downshifting Layers for the Improvement of Light‐Harvesting Efficiency in Dye‐Sensitized Solar Cells

Luminescence downshifting (LDS) of light can be a practical photon management technique to compensate the narrow absorption band of high‐extinction‐coefficient dyes in dye‐sensitized solar cells (DSSCs). Herein, an optical analysis on the loss mechanisms in a reflective LDS (R‐LDS)/DSSC configuration is reported. For squaraine dye (550–700 nm absorption band) and CaAlSiN₃:Eu²⁺ LDS material (550–700 nm emission band), the major loss channels are found to be non‐unity luminescence quantum efficiency (QE) and electrolyte absorption. By using an ideal LDS layer (QE=100 %), a less absorbing electrolyte (Co‐based), and antireflection coatings, approximately 20 % better light harvesting is obtained. If the absorption/emission band of dye/LDS is shifted to 800 nm, a maximal short‐circuit current density (J_sc) of 22.1 mA cm^?2 can be achieved. By putting the LDS layer in front of the DSSC (transmissive mode), more significant loss channels are observed, and hence a lower overall efficiency than the R‐LDS configuration.     

Dielectrophoretically patterned carbon nanotubes to sort microparticles

This article compares the operation of a dielectrophoretic (DEP) platform before and after pattering carbon nanotubes (CNTs) between its microelectrodes. The diverse performance of the DEP system is assessed by separating 1 and 5 μm polystyrene particles. In the absence of CNTs, both particles can only be trapped by operating the system at low medium conductivities, (<10⁻³ S/m) and frequencies (<75 kHz). Alternatively, applying CNTs to the system, some CNTs coat the surface of particles and increase their overall conductivity and permittivity, whereas the rest of them are patterned between the microelectrodes and induce strong DEP forces at their free ends, which can effectively trap the coated particles. The first development extends the range of medium conductivities and frequencies at which the trapping of both particles is achievable, whereas the second development facilitates the selective deposition of particles along the surface of curved microelectrodes. Setting the medium conductivity to 2×10⁻³ S/m and the frequency to 20 MHz, most of 5 μm particles are trapped at the entry region of the first microelectrode pair, whereas most of 1 μm particles are trapped at the tips, and this distinction facilitates their separation. The trapping of 1 μm particles can be improved by decreasing the frequency to 1.5 MHz. This study demonstrates how the integration of CNTs into microfluidic systems enables them to operate beyond their capabilities.     

Laser-muon spin spectroscopy in liquids - a technique to study the excited state chemistry of transients

This study introduces laser-muon spin spectroscopy in the liquid phase, which extends muonium chemistry in liquids to the realm of excited states and enables the detection of muoniated molecules by their spin evolution after laser excitation. This leads to new opportunities to study the Kinetic Isotope Effects (KIEs) of muonium/atomic hydrogen reactions and to probe transient chemistry in radiolysis processes involved in muonium formation, as well as muoniated intermediates in excited states.     

Simultaneous Spectrophotometric Determination of Sunset Yellow and Quinoline Yellow in a Single Step

In this work a new modified standard addition method for simultaneous spectrophotometric determination of Sunset yellow (SY) and Quinoline yellow (QY) is used. The generalized Net Analyte Signal Standard Addition Method (GNASSAM) was introduced for simultaneous standard addition of analytes. By applying this method the concentrations of analytes are determined in a single step. The applicability of new method was used for the simultaneous determination of strongly overlapped spectra of SY and QY in a real sample without using any separation step. GNASSAM was also used to calculate figures of merit. Moreover, good limits of detection (SY=0.13 and QY=0.16 mg L ^?1) and suitable selectivity and sensitivity were determined. HPLC method was applied for finding subspace in binary mixtures of real samples. The results of investigated method for real sample were compared with HPLC results. The obtained results were in a good agreement with those of HPLC method.