Facile synthesis of PtSnZn nanosheet thin film at oil–water interface by use of organometallic complexes: An efficient catalyst for methanol oxidation and p‐nitrophenol reduction reactions

PtSnZn nanosheet thin film with stable and high activity towards methanol electro‐oxidation was synthesized via a simple reduction of organometallic precursors including [PtCl₂(cod)] (cod = cis,cis‐1,5‐cyclooctadiene) and [Sn(CH₃)₄] complexes, in the presence of [Zn(acac)₂] (acac = acetylacetonate) complex at toluene–water interface. Catalytic activities of PtSnZn nanosheets were investigated in the p‐nitrophenol (p‐Nip) reduction and methanol oxidation reactions. The obtained results demonstrate that PtSnZn nanosheets exhibit a good electrocatalytic performance for methanol oxidation reaction, the catalytic activity of the PtSnZn nanosheets being at least 3.5 times higher than that of Pt nanoparticle thin film. Also, the apparent rate constant obtained for p‐Nip reduction with the PtSnZn nanosheets is at least 2.3 times higher than that for Pt nanoparticle thin film due to the appropriate interaction between platinum, tin and zinc metals and geometric properties of PtSnZn nanosheet thin film. Nanosheets are highly favourable for superior catalytic performances due to their geometric properties. A facile and efficient route was used to synthesize trimetallic alloy thin film at oil–water interface.     

Synthesis and characterization of a novel and green rod-like magnetic ZnS/CuFe2O4/agar organometallic hybrid catalyst for the synthesis of biologically-active 2-amino-tetrahydro-4H-chromene-3-carbonitrile derivatives

The magnetic biocompatible rod-like ZnS/CuFe₂O₄/agar organometallic hybrid catalyst was designed and prepared based on a natural macromolecule (agar) through a green and convenient method using inexpensive, nontoxic, and easily available substances. Then, the as-prepared catalyst was characterized by several techniques such as Fourier transform-infrared spectroscopy, energy-dispersive X-ray analysis, scanning electron microscopy image, transmission electron microscopy, vibrating sample magnetometry curve, X-ray diffraction pattern, and thermogravimetric analysis. Eventually, the catalytic application of the ZnS/CuFe₂O₄/agar nanobiocomposite was assessed in sequential Knoevenagel condensation–Michael addition reaction of dimedone, malononitrile, and different substituted aromatic aldehydes for the synthesis of 2-amino-tetrahydro-4H-chromene-3-carbonitrile derivatives. Some notable strengths of this environmentally benign catalyst include simplicity of catalyst preparation and separation, affording desired products with satisfactory yields (81%–97%) in very short reaction times (3–18 min), and with no need for complicated work-up processes. Experimental tests showed that the catalyst can be successfully reused after five sequential runs without significant reduction in its catalytic efficiency.     

One-pot synthesis of 1,2,4,5-tetrasubstituted and 2,4,5-trisubstituted imidazoles by zinc oxide as efficient and reusable catalyst

Abstract  

ZnO is an efficient, readily available, and reusable catalyst for the one-pot synthesis of 1,2,4,5-tetrasubstituted and 2,4,5-trisubstituted imidazoles. This procedure is very simple and affords excellent yields.     

Current advancements on charge selective contact interfacial layers and electrodes in flexible hybrid perovskite photovoltaics

Perovskite-based photovoltaic materials have been attracting attention for their strikingly improved performance at converting sunlight into electricity.The beneficial and unique optoelectronic characteristics of perovskite structures enable researchers to achieve an incredibly remarkable power conversion efficiency.Flexible hybrid perovskite photovoltaics promise emerging applications in a myriad of optoelectronic and wearable/portable device applications owing to their inherent intriguing physicochemical and photophysical properties which enabled researchers to take forward advanced research in this growing field.Flexible perovskite photovoltaics have attracted significant attention owing to their fascinating material properties with combined merits of high efficiency,light-weight,flexibility,semitransparency,compatibility towards roll-to-roll printing,and large-area mass-scale production.Flexible perovskite-based solar cells comprise of 4 key components that include a flexible substrate,semi-transparent bottom contact electrode,perovskite(light absorber layer)and charge transport(electron/hole)layers and top(usually metal)electrode.Among these components,interfacial layers and contact electrodes play a pivotal role in influencing the overall photovoltaic performance.In this comprehensive review article,we focus on the current developments and latest progress achieved in perovskite photovoltaics concerning the charge selective transport layers/electrodes toward the fabrication of highly stable,efficient flexible devices.As a concluding remark,we briefly summarize the highlights of the review article and make recommendations for future outlook and investigation with perspectives on the perovskite-based optoelectronic functional devices that can be potentially utilized in smart wearable and portable devices.     

A novel proposal for DWDM demultiplexer design using modified-T photonic crystal structure

We propose an ultra compact structure to realize demultiplexing operation for Dense Wavelength Division Multiplexing (DWDM) communication systems using resonant cavity in modified-T Photonic Crystal (PC) structure. To the best of our knowledge, this is for the first time that a PC-based demultiplexer has been achieved with 1 nm channel spacing and 0.45 nm mean value of bandwidth without using either specific materials or complexities in fabrication process. Designs offering improvement of channel spacing and bandwidth of the proposed demultiplexer is our aim in this work. The attained characteristics are approximately in the range of the DWDM communication systems. Accurate resonant cavities have been used in terms of location and size of holes in the proposed structure in order for them to capture desired wavelengths in optical telecommunication range. Our simulations indicate the average amount of crosstalk (Xt) and the average quality factor (Q) to be ?21.1 dB and 3488, respectively. Two-dimensional (2D) Finite-Difference-Time-Domain (FDTD) is chosen for simulation of the proposed structure. The footprint of the structure is approximately 536 μm² and can be fabricated and integrated densely and easily.     

TMSCl-promoted selective oxidation of sulfides to sulfoxides with hydrogen peroxide

Selective oxidation of sulfides to sulfoxides is achieved using H₂O₂ and TMSCl as the promotor. Aromatic and aliphatic sulfides are oxidized to sulfoxides in excellent yields and in short reaction times. Different functional groups including ketone, alkene, ester, and alcohol are tolerated.     

Existence of global solutions to nonlinear fuzzy Volterra integro-differential equations

In this paper, we introduce new solutions for fuzzy differential equations as mixed solutions, and prove the existence and uniqueness of global solutions for fuzzy initial value problems involving integro-differential operators of Volterra type. One example is also given by applying mixed solution concept to fuzzy linear differential equations for obtaining their global solutions.     

Highly selective catalytic Friedel–Crafts sulfonylation of aromatic compounds using a FeCl3-based ionic liquid

Friedel–Crafts sulfonylation of aromatic compounds was carried out using FeCl₃-based ionic liquid. These liquids serve as efficient media as well as Lewis acid catalyst.     

Determination of BTEX in urine samples using cooling/heating-assisted headspace solid-phase microextraction

Excessive and uncontrolled exposures of the workers to benzene, toluene, ethylbenzene and xylene (BTEX) have currently raised great concerns among industrial hygienist all over the world. Therefore, the effective monitoring of such exposures is assumed to be of prime importance. A cold fiber solid-phase microextraction device based on a cooling capsule as a cooling unit and CO₂ as a coolant was applied to quantitatively analyze BTEX in aqueous samples. A gas chromatography with flame ionization detection was recruited to analyze the target analytes, which had been identified according to their retention times. Several factors such as coating temperature, extraction time and temperature, sample volume and sodium content were optimized. Two modes of extraction, i.e., headspace (HS) and headspace cold fiber (HS-CF) in SPME, were investigated and compared under optimized conditions. The results revealed that HS-CF-SPME has the most appropriate outcome for the extraction of BTEX from aqueous samples. Under the optimized conditions, the calibration curves were linear within the range of 0.2–500 ng ml^?1 and the detection limits were between 0.02 and 0.07 ng ml^?1.The intraday relative standard deviations was lower than about 10%. The method was successfully applied to the determination of BTEX in urine samples with good recovery.     

Delayed autocatalytic behavior of Mn(II) ions at a critical ratio: The effect of structural isomerism on permanganic oxidation of L‐norleucine

The kinetics of the permanganic oxidation process of L ‐norleucine, L ‐leucine, L ‐iso‐leucine, and L ‐tert‐leucine in strong acid medium has been investigated using a spectrophotometric technique. Conclusive evidences have proven autocatalytic activity of Mn(II) for these reactions in strong acid medium analogous to weak acid medium, but in the former, ratio of Mn(II) to amino acid concentration must reach a certain amount for autocatalytic phenomenon to emerge, which we call “critical ratio.” This critical ratio depends on the nature of the amino acid employed. Thus considering “delayed autocatalytic behavior” of Mn(II) ions, rate equations satisfying observations for both catalytic and noncatalytic routes have been presented. Kinetic data in a noncatalytic pathway have been fitted to a biparametric equation including inductive, steric, and hyperconjugation correction effects, and it is determined that by shifting the side branch on a carbon chain toward an α‐carbon atom (adjacent to amino acid's functional group) and also adding branches to the α‐carbon atom, the reaction rate in the noncatalytic pathway decreases. Inductive and steric hindrance factors in amino acid's carbon chain are effective on processes' rate both in catalytic and noncatalytic pathways. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 38: 1–11, 2006