Simple analyzer for continuous monitoring of sulfur dioxide in gas streams

The construction, optimization and use of simple and inexpensive gas analyzer for real time measurement of sulfur dioxide in gas streams are described. The analyzer consisted of three main components (i) a custom fabricated hollow fiber membrane (HFM) gas contactor, (ii) carrier solution which absorbs SO₂ molecules from the gas stream in the HFM gas contactor and (iii) a flow-through detector placed downstream which continuously measures the changes occurred to the carrier solution upon absorption of SO₂ molecules. The significant acidic properties of the produced sulfurous acid suggested pH and conductivity detectors to monitor the decrease in pH or the increase in the conductivity which constituted the basis for quantification of SO₂ in the gas line. Aqueous potassium oxalate (10^? 1 mol/L) and hydrogen peroxide (10^? 3 mol/L) were used as carrier solutions in combination with pH and conductivity detectors, respectively. The analyzer equipped with pH detector provided linear potentiometric response to SO₂ concentration up to 1000 ppm with Nernstian slop of 61 mV/log[SO₂]. Excellent SO₂ recoveries (97–108%) were obtained in the presence of several folds of potentially interfering acidic gases, i.e., CO₂ and H₂S. The conductivity detector provided linear response up to 2500 ppm. Under optimized conditions, both detectors offered several favorable performance characteristics such as (i) fast response and recovery times, (ii) excellent signal stability and reproducibility (RSD = 0.5%), (iii) intrinsic high selectivity to most common neutral gases, e.g., CH₄, N₂, O₂, CO, etc. The suggested analyzer was applied successfully in monitoring the removal of SO₂ from SO₂–N₂ gas mixtures with hollow fiber membrane contactor using distilled water or aqueous sodium hydroxide as stripping solvents.     

Iron(III)(salen)Cl as an efficient catalyst for synthesis of bis(indolyl)methanes

[Fe(III)(salen)]Cl (salen = N,N′-ethylenebis(salicylimine)) is an efficient catalyst for the electrophilic substitution of indole with carbonyl compounds to afford the corresponding bis(indolyl)methanes in good yields in molten tetrabutylammonium bromide as an ionic liquid. Notable features of this new procedure are shorter reaction times, cleaner reaction profiles, and simple experimental and work-up procedures.     

Temperature dependent polariton emission from strongly coupled organic semiconductor microcavities

We investigated the absorption and photoluminescence (PL) of J-aggregates of a cyanine dye both in a thin film format and when used as the active layer in a strongly-coupled microcavity. We show that as temperature is reduced, the absorption linewidth of the J-aggregates narrows and shifts to higher energy. When the J-aggregate is placed in a microcavity we find that the energy of the polariton modes also shifts to higher energies as temperature is reduced. We compare the intensity of PL emission from the upper and lower branches at resonance as a function of temperature, and find that it can be described by an activation energy of 25 meV. PL emission spectra at resonance also suggest that uncoupled excitons inside the microcavity populate the upper polariton branch states.     

Hidden electrochemistry in the thermal grafting of silicon surfaces from grignard reagents

Covalent grafting of alkyl chains on silicon can be obtained by thermal treatment in Grignard reagents. Alkyl halide present in the Grignard solution as an impurity appears to play a key role in the grafting process. Grafting efficiency is improved when the alkyl halide concentration is increased. It is also enhanced on n-type substrates as compared to p-type substrates and when alkyl bromides are present in solution rather than alkyl chlorides. The grafting reaction involves a zero-current electrochemical step. A reaction model in which simultaneous Grignard oxidation and alkyl halide reduction take place at the silicon surface accounts for all these observations. Alkyl halide reduction is the rate-determining step. Negative charging of the silicon surface lowers the energetic barrier for this reaction, allowing for efficient grafting on n-Si.     

Development and validation of SPMMTE HPLC method for analysis of profens from human plasma

A fast, selective and reproducible solid‐phase membrane microtip extraction (SPMMTE) HPLC method has been developed and validated for the analyses of ibuprofen, ketoprofen, and flurbiprofen from human plasma. The analysis was carried out on a C₁₈ (150 × 4.6 mm; 5 μm) column. The mobile phase used was water–acetonitrile (55:45, v/v) adjusted to pH 3.0 using trifluoroacetic acid, at a flow rate 0.5 mL/min with a detection wavelength of 225 nm. The values for the capacity factors for the profen samples ranged from 0.47 to 1.50. The values for the selectivity factor (α) for ketoprofen–flurbiprofen, flurbiprofen–ibuprofen and ibuprofen–ketoprofen combinations from human plasma samples were 1.99, 1.00 and 2.10, respectively. The resolution factors (Rs) for ketoprofen–flurbiprofen, flurbiprofen–ibuprofen and ibuprofen–ketoprofen from plasma samples were 3.00, 1.50 and 4.10, respectively. The percentage recoveries of ibuprofen, ketoprofen, and flurbiprofen from human plasma were 75–85%. All of the profens were separated within 7.0 min, indicating a relatively fast method. During the development of the SPMMTE procedure the parameters of pH, contact time, desorption and types of solvents were optimized. The final method was also found to be efficient, effective and inexpensive. Copyright © 2016 John Wiley & Sons, Ltd.     

A photonic crystal biosensor with temperature dependency investigation of micro-cavity resonator

A two dimensional photonic crystal biosensor implemented by waveguides and microcavity is theoretically investigated. The designed structure has high quality factor about 15,000 and sensitivity approximately 141.67 nm/RIU, which are important parameters in biosensing applications. Also there is a linear dependency between resonant wavelength shift and refractive index changes. Since water is the main component of human organism, the temperature and wavelength dependence of proposed microcavity is investigated. The results show that the structure has good temperature stability. The temperature sensitivity is about −0.0142 nm/°C.     

Dual-seeded dispersion polymerization: Effect of different polymerization conditions on the shape of the produced particles

Dual-seeded dispersion polymerization (DSDP) of 2-ethylhexyl methacrylate with polystyrene (PS) and poly(methyl methacrylate) (PMMA) seed beads in the presence of saturated hydrocarbon droplets followed by evaporation of the hydrocarbon was studied. The effect of various polymerization conditions including initiator type and content, stabilizer type and concentration, and different hydrocarbon’s content on the shape of the obtained particles was investigated. The increase of concentration of 2,2'-azobis(isobutyronitrile) (AIBN) had no effect on the shape of the produced almond-shell-like PS particles, although it contributes in the formation of associated composite particles along with larger poly(2-ethylhexyl methacrylate) (PEHMA) beads produced by secondary nucleation. The experimental results showed that other initiators led to the formation of stable golf-ball-like PMMA particles as well as PS ones with symmetric shape. The type of stabilizer did not affect the shape of the particles. This observation suggests that unique almond-shelllike PS particles can be produced through a stabilizer-free DSDP process. The lowering of the concentration of hydrocarbons with long alkyl chains yielded stable disc-like PMMA particles. The formation of functional almond-shell-like particles by using light hydrocarbons was another interesting finding of this research.     

NaY zeolite functionalized by sulfamic acid/Cu(OAc)2 as a new and reusable heterogeneous hybrid catalyst for efficient solvent-free formylation of amines

NaY zeolite functionalized by sulfamic acid/Cu(OAc)_2[NaY/SA/Cu(Ⅱ)] was synthesized and used as a new,efficient and recyclable catalyst for preparation of formamides. This novel organic-inorganic hybrid catalyst was characterized by several techniques such as FT-IR, XRD, SEM, EDX and TG analysis.Chemoselectivity, easy procedure, excellent yields, very short reaction times, solvent-free and mild reaction conditions are some benefits of this new protocol.