Mesopore‐controllable Carbon Aerogel and their Highly Loaded PtRu Anode Electrocatalyst for DMFC Applications

Catalyst loading and layer thickness are crucial factors to enhance the cell performance and to reduce cost of membrane electrode assemblies (MEAs). Outstanding properties, such as large surface area to disperse metal nanoparticles and sufficient pore volume and size, is needed in utilization of fuel cell. Carbon aerogels are one of the good candidates that meets the above conditions. Those are synthesized by polycondensation reaction of resorcinol and formaldehyde (RF) polymer, supercritical drying to keep pore skeleton structure caused by capillary force and calcination of RF polymer in nitrogen atmosphere to be controllable meso pore (2～43 nm) as role of support for electric conductor and dispersion of metal nanoparticles. In order to utilization of anode catalyst in direct methanol fuel cell, highly loaded (80 weight percent) platinum and ruthenium onto carbon aerogel are synthesized by Bönnemann colloid method. The single cell test of carbon aerogel supported PtRu anode catalyst is performed and over 40 nm pore sized‐catalysts are the best performance due to sufficient surface area to anchor uniform and small metal nanoparticles and good pathway to drive fuel and outgas even though PtRu nanoparticles are anchored on the outer surface of carbons.     

A Highly Efficient,Clean‐Surface,Porous Platinum Electrocatalyst and the Inhibition Effect of Surfactants on Catalytic Activity

Herein we report a gentle seedless and surfactant‐free method for the preparation of clean‐surface porous platinum nanoparticles. In terms of electrocatalytic CH₃OH oxidation, the clean‐surface porous platinum exhibited better performance than platinum nanoparticles and a commercial Pt/C catalyst. The porous nanostructures exhibited 2.26‐fold higher mass activity and 2.8‐fold greater specific activity than the Pt/C catalyst. More importantly, three typical surfactants, cetyltrimethylammonium bromide/chloride (CTAB/C), poly(vinylpyrrolidone), and sodium dodecyl sulfate, were chosen to study the inhibition effect of surfactants on electrocatalytic performance. It was observed that the surfactants led to a clear selective decrease in electrocatalytic performance. CTAB/C inhibited the catalytic activity the most due to the stronger interaction between the OH‐enriched platinum surface and the positively charged molecules. Thus, this work indicates that these clean‐surface porous platinum nanoparticles may be used as efficient catalysts for direct methanol fuel cells and provides a greater understanding of the inhibition effects of surfactants on catalytic activity.     

Chitosan‐Functionalized Carbon Nanotubes as Support for the High Dispersion of PtRu Nanoparticles and their Electrocatalytic Oxidation of Methanol

Carbon nanotubes (CNTs) were non‐covalently functionalized with chitosan (Chit) and then employed as the support for PtRu nanoparticles. The functionalization was carried out at room temperature without the use of corrosive acids, thereby preserving the integrity and the electronic conductivity of the CNTs. Transmission electron microscopy reveals that PtRu nanoparticles were highly dispersed on the surface of Chit‐functionalized CNTs (CNT‐Chit) with small particle‐size. Cyclic voltammetry studies indicated that the PtRu nanoparticle/CNT‐Chit nanohybrids have a higher electrochemical surface area, electrocatalytic performance, and stability towards methanol oxidation compared to PtRu nanoparticles supported on the pristine CNTs.     

Highly Efficient,Conjugated‐Polymer‐Based Nano‐Photosensitizers for Selectively Targeted Two‐Photon Photodynamic Therapy and Imaging of Cancer Cells

Two‐photon photodynamic therapy (2P‐PDT) is a promising noninvasive treatment of cancers and other diseases with three‐dimensional selectivity and deep penetration. However, clinical applications of 2P‐PDT are limited by small two‐photon absorption (TPA) cross sections of traditional photosensitizers. The development of folate receptor targeted nano‐photosensitizers based on conjugated polymers is described. In these nano‐photosensitizers, poly{9,9‐bis[6′′‐(bromohexyl)fluorene‐2,7‐ylenevinylene]‐co‐alt‐1,4‐(2,5‐dicyanophenylene)}, which is a conjugated polymer with a large TPA cross section, acts as a two‐photon light‐harvesting material to significantly enhance the two‐photon properties of the doped photosensitizer tetraphenylporphyrin (TPP) through energy transfer. These nanoparticles displayed up to 1020‐fold enhancement in two‐photon excitation emission and about 870‐fold enhancement in the two‐photon‐induced singlet oxygen generation capability of TPP. Surface‐functionalized folic acid groups make these nanoparticles highly selective in targeting and killing KB cancer cells over NIH/3T3 normal cells. The 2P‐PDT activity of these nanoparticles was significantly improved, potentially up to about 1000 times, as implied by the enhancement factors of two‐photon excitation emission and singlet oxygen generation. These nanoparticles could act as novel two‐photon nano‐photosensitizers with combined advantages of low dark cytotoxicity, targeted 2P‐PDT with high selectivity, and simultaneous two‐photon fluorescence imaging capability; these are all required for ideal two‐photon photosensitizers.     

Nano‐sized metal complexes of azo L‐histidine: Synthesis,characterization and their application for catalytic oxidation of 2‐amino phenol

A novel azo dye ligand formed by the coupling of L‐histidine with 2‐hydroxy‐1‐naphthaldyhide(H₂L) and its Ru³⁺, Pd²⁺ and Ni²⁺ nano‐sized complexes were obtained and described by elemental analysis, TGA, magnetic moment measurements, molar conductance, UV‐Vis, ESR, X‐ray powder diffraction, IR, SEM, TEM, ¹H‐nmr, ¹³C‐nmr, and EI‐mass spectral studies. The analytical results and spectral studies detected that the H₂L ligand acts as dibasic tetradentate via aldehyde oxygen, azo nitrogen and deprotonated OH and COOH groups. The data showed the paramagnetic Ru³⁺ complex has octahedral geometry while Pd²⁺ and Ni²⁺ have square planar structures. The molar conductance measurements display all complexes are nonelectrolyte. The crystallinity, morphology and average particle size data revealed the prepared complexes were formed in the Nano scale. The average particle size as calculated from TEM images are found to be 13.72, 64.52 and 115.00 nm for Ru³⁺, Pd²⁺ and Ni²⁺ chelates, respectively. The catalytic activities of these compounds were checked for oxidation of 2‐amino phenol to 2‐amino‐3H phenoxazine‐3‐one as heterogeneous catalysts. A 96, 31 and 21% catalytic conversion are found when using Ru(III), Pd(II) and Ni(II) complexes respectively.     

Highly reusable support‐free copper(II) complex of para‐hydroxy‐substituted salen: Novel,efficient and versatile catalyst for C─N bond forming reactions

An air‐stable, highly active and versatile method for C─N bond forming reactions is reported. Under mild conditions using a highly reusable support‐free Cu(II)–salen complex, structurally diverse N ‐aryl‐substituted compounds were obtained via direct C─N bond forming reaction of HN‐heterocycles with aryl iodides or three‐component C─N bond forming reaction of 2‐bromobenzaldehyde, aniline derivatives and sodium azide in good to excellent yields. C─N bond forming reaction for benzimidazole derivatives was also performed in the presence of the catalyst under ambient conditions. A series of hybrid benzimidazoles bearing morpholine, tetrazole and quinoxaline backbones were produced using this method. All reactions were performed in short times under air. The Cu(II) catalyst could be reused up to eight times in the direct cross‐coupling reaction of 9H –carbazole with iodobenzene without any decrease in its catalytic activity.     

Application of Single‐use Electrode Based on Nano‐clay and MWCNT for Simultaneous Determination of Acetaminophen,Ascorbic Acid and Acetylsalicylic Acid in Pharmaceutical Dosage

In this study, a highly sensitive, selective and cost‐effective electrochemical nano‐sensor has been developed for the first time so as to facilitate the simultaneous and low‐level detection of acetaminophen (paracetamol, PAR), ascorbic acid (A) and acetylsalicylic acid (ASA) ternary mixture. The sensor is based on nano‐sepiolite clay (SEP) with multiwall carbon nanotubes (MWCNTs) onto electrochemically pretreated pencil graphite electrode (pPGE). The surface properties of the sensor were examined by using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM) techniques. The pH effect, composition of modifiers, immobilization time, deposition potential and deposition time values were optimized to reach the best response of PAR, A and ASA. Moreover, in optimum analytical conditions, adsorptive stripping differential pulse voltammmetric (AdsDPV) method was developed for the simultaneous analysis of the ternary mixtures concerned by using SEP/MWCNTs/pPGE sensor. This sensor exhibited the low detection limits of 0.018, 0.042 and 0.047 μM for PAR, A and ASA ternary mixture, respectively. The developed AdsDPV method was applied for quantitative determination of PAR, A and ASA in the pharmaceutical formulation. The recovery experiments were carried out to control the accuracy and precision of the method. The obtained voltammetric recoveries were comparable with the HPLC data given in the literature.     

Synthesis,characterization and catalytic performance of palladium supported on pyridine‐based covalent organic polymer for Suzuki‐Miyaura reaction

A bipyridine‐based covalent organic polymer (COP) was successfully synthesized by condensation of trimesoyl chloride (TMC) and 2,2′‐bipyridine‐5,5′‐diamine (Bpy) under ambient conditions. This material was modified by coordination of PdCl₂ to COP framework, affording a hybrid material, Pd@TMC‐Bpy COP, which was applied as a highly efficient heterogeneous catalyst for Suzuki‐Miyaura reaction under ligand‐free conditions in ethyl lactate. The catalyst could be reused for five times without obvious loss of its activity.     

Preparation,characterisation and modification of carbon‐based monolithic rods for chromatographic applications

A range of porous carbon‐based monolithic (PCM) rods with flow‐through pore sizes of 1, 2, 5 and 10 μm, were produced using a silica particle template method. The rods were characterised using SEM and energy‐dispersive X‐ray spectroscopy, BET surface area and porous structure analysis, dilatometry and thermal gravimetry. SEM evaluation of the carbon monolithic structures revealed an interconnected rigid bimodal porous structure and energy‐dispersive X‐ray spectroscopy analysis verified the quantitative removal of the embedded silica beads. The specific surface areas of the 1, 2, 5 and 10 μm rods were 178, 154, 84 and 125 m²/g after pyrolysis and silica removal, respectively. Shrinkage of the monolithic rods during pyrolysis is proportional to the particle size of the silica used and ranged from 9 to 12%. Mercury porosimetry showed a narrow distribution of pore sizes, with an average of ～700 nm for the 1 μm carbon monolith. The suitability of bare and surface oxidised PCM rods for the use as a stationary phase for reversed and normal phase LC was explored. The additional modification of PCM rods with gold micro‐particles followed by 6‐mercaptohexanoic acid was performed and ion‐exchange properties were evaluated.     

Polymer complexes. LXXVI. Synthesis,characterization, CT‐DNA binding,molecular docking and thermal studies of sulfoxine polymer complexes

Novel polymer complexes of 8‐hydroxyquinoline‐5‐sulfonic acid hydrate ( H ₂ L ) with Cu²⁺, Co²⁺ and Ni²⁺ chloride were prepared and characterized. Microanalysis, magnetic susceptibility, IR spectra, electron spin resonance, mass spectra, X‐ray, molar conductance, thermal, and UV–Vis spectra studies have been used to confirm the structure of the prepared polymer complexes. The molecular and electronic structures of the hydrogen bond conformers for ligand ( H ₂ L ) were optimized theoretically and the quantum chemical parameters were calculated. On the basis of elemental and IR data, the chemical structure of metal chelates commensurate that the tri‐dentate (H₂L) coordinate to metal chlorides through oxygen atom of phenolic OH and oxygen atom of SO₃‐H group by replacing H atoms and nitrogen of the quinoline ring. The magnetic studies suggested the octahedral geometrical structure for all produced polymer complexes with general formula {[ML (OH₂)₃] .xH₂O}_n (M = Cu²⁺, x = 1.; Co²⁺, x = 2 and Ni²⁺, x = 2) in molar ratio (1:1). Coats–Redfern and Horowitz–Metzger methods have been used for calculating the activation thermodynamic parameters of the thermal decomposition for H ₂ L and its polymer complexes. The interaction between H ₂ L and its transition metal complexes with the calf thymus DNA (CT‐DNA) was determined by UV–Vis spectra. Binding efficiency between H ₂ L with the receptors of the prostate cancer (PDB code 2Q7L Hormone) and the breast cancer (PDB code 1JNX Gene regulation) was studied by molecular docking. The inhibition behaviour of H ₂ L against the corrosion of carbon steel / HCl (2 M) solution was studied by weight loss, Tafel polarisation, electrochemical impedance spectroscopy (EIS) and electrochemical frequency modulation (EFM) techniques. The adsorption isotherm was found to be Friendlish isotherm. The morphology of inhibited carbon steel? s surface was studied using scanning electron microscope (SEM) and energy dispersive X‐ray spectroscopy (EDS).     

Surface modification of MWCNTs with glucose and their utilization for the production of environmentally friendly nanocomposites using biodegradable poly(amide‐imide) based on N‐trimellitylimido‐S‐valine matrix

In the present investigation, the preparation, characterization, and surface morphology of poly(amide‐imide) (PAI)/multi‐walled carbon nanotubes (MWCNTs) bionanocomposites (BNCs) were the main goals of the study. At first, an optically active PAI based on S‐valine as a biodegradable segment was synthesized. Then, carboxyl‐modified MWCNTs were functionalized with glucose (f‐MWCNT) as a biological active molecule in a green method to achieve a fine dispersion of f‐MWCNT bundles in the PAI matrix. The existence of S‐valine in the PAI matrix and functionalized MWCNT with glucose resulted in a series of potentially biodegradable nanocomposites. The obtained BNCs were characterized by various techniques. Field emission scanning and transmission electron microscopy micrographs of the composites showed a fine dispersion of f‐MWCNTs in the polymer matrix because of hydrogen bonding and π–π stacking interaction between f‐MWCNTs and polymer functional groups and aromatic moieties. Adding f‐MWCNTs into polymer matrix significantly improved the thermal stability of BNCs because of the increased interfacial interaction between the PAI matrix and f‐MWCNTs and also good dispersion of f‐MWCNT in the polymer matrix. Copyright © 2015 John Wiley & Sons, Ltd.     

Magnetic NiFe2O4 nanoparticles: efficient,heterogeneous and reusable catalyst for synthesis of acetylferrocene chalcones and their anti‐tumour activity

A robust synthesis of magnetic NiFe₂O₄ nanoparticles via a hydrothermal technique was investigated. The prepared magnetic NiFe₂O₄ nanoparticles were characterized using powder X‐ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy (TEM), high‐resolution TEM, energy‐dispersive X‐ray spectroscopy, thermogravimetric analysis, infrared spectroscopy and vibrating sample magnetometry. XRD and TEM analyses confirmed the formation of single‐phase ultrafine nickel ferrite nanoparticles with highly homogeneous cubic shape and elemental composition. Moreover, the prepared magnetic NiFe₂O₄ nanoparticles were used as an efficient, cheap and eco‐friendly catalyst for the Claisen–Schmidt condensation reaction between acetylferrocene and various aldehydes (aromatic and/or heterocyclic) yielding acetylferrocene chalcones in excellent yields, with easy work‐up and reduced reaction time. The products were purified via crystallization. The structures of the produced compounds were elucidated using various spectroscopic analyses (¹H NMR, ¹³C NMR, GC–MS). The catalyst is readily recovered by simple magnetic decantation and can be recycled several times with no discernible loss of catalytic activity. Furthermore, the prepared chalcone derivatives were evaluated for their anti‐tumour activity against three human tumour cell lines, namely HCT116 (colon cancer), MCF7 (breast cancer) and HEPG2 (liver cancer), and showed a good activity against colon cancer. Copyright © 2016 John Wiley & Sons, Ltd.     

Influence of poly(N‐isopropylacrylamide) and poly(N,N′‐diethyl acrylamide) coatings on polysulfone/polyacrylonitrile‐based membranes for protein separation

Herein we describe the design and the assembly of temperature sensitive polysulfone (PS)/polyacrylonitrile (PAN) blend membranes using supercritical fluid technology. Blended membranes were prepared using the CO₂‐assisted phase inversion method, and their pores were coated with two thermoresponsive hydrogels‐poly(N‐isopropylacrylamide) (PNIPAAm) and poly(N,N′‐diethylacrylamide) (PDEAAm). Permeation experiments of bovine serum albumin (BSA) and lysozyme (LYS) solutions were used to evaluate the performance and temperature‐responsive behavior of coated membranes. While membranes coated with PNIPAAm presented similar protein permeation profiles at temperatures below and above its lower critical solution temperature, PDEAAm coating imparted a temperature‐responsive behavior to PS/PAN (90:10) membranes and selective permeation of proteins with different sizes. Copyright © 2011 John Wiley & Sons, Ltd.     

Highly active bifunctional cobalt‐salen complexes for the synthesis of poly(ester‐block‐carbonate) copolymer via terpolymerization of carbon dioxide,propylene oxide,and norbornene anhydride isomer: Roles of anhydride conformation consideration

This article describes an efficient synthetic route of defined reactive polyester‐block‐polycarbonate copolymers, utilizing a bifunctional SalenCoNO₃ complex as catalyst for the single‐step terpolymerization of norbornene anhydride (NA), propylene oxide, and carbon dioxide. The geometric isomer of NA plays an important role in polymerization efficacy and the resulting polymer microstructure, including carbonate content, sequence isomer of polycarbonate moiety, and molecular weight. A hydroxyl‐functionalized polyester–polycarbonate block copolymer was synthesized by a thiol‐ene reaction. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 789–795     

A Graphene‐based Electrochemical Sensor for the Individual,Selective and Simultaneous Determination of Total Chlorogenic Acids,Vanillin and Caffeine in Food and Beverage Samples

An electrochemical sensor based on the electrocatalytic activity of graphene (GR) was prepared, and used for the individual, selective and simultaneous determination of 5‐O‐Caffeoylquinic acid (5‐CQA) that is major compound of chlorogenic acids in coffee, vanillin (VAN) and caffeine (CAF). The electrochemical behaviors of these compounds on GR modified glassy carbon electrode (GR/GCE) were investigated by cyclic voltammetry and square‐wave adsorptive stripping voltammetry. By using stripping conditions after 30 s accumulation under open‐circuit voltage, the electrochemical oxidation peaks appeared at +0.53, 0.83 and 1.39 V in phosphate buffer pH 2.5, and good linear current responses were obtained with detection limits of 4.4×10⁻⁹, 5.0×10⁻⁷, and 3.0×10⁻⁷ M for 5‐CQA, VAN and CAF, respectively. The potential applicability of the proposed method was illustrated in commercial food and beverage samples.     

Synthesis,Spectroscopic Characterization,Antimicrobial, Pesticidal and Nematicidal Activity of Some Nitrogen‐Oxygen and Nitrogen‐Sulfur donor Coumarins based Ligands and their Organotin(IV) Complexes

Series of new tin complexes are synthesized by classical thermal and microwave‐irradiated techniques. The biologically potent ligands 3‐formyl‐4‐chlorocoumarin semicarbazone (L¹H) and 3‐formyl‐4‐chlorocoumarin thiosemicarbazone (L²H), were prepared by the condensation of semicarbazide hydrochloride and thiosemicarbazide in ethanol with the particular ketone by using microwave as well as conventional methods. The tin(IV) complexes have been prepared by mixing Ph₃SnCl/Me₃SnCl/Me₂SnCl₂ in 1:1 and 1:2 molar ratios with monofunctional bidentate ligands. The structures of the ligands and their tin complexes were confirmed by the elemental analysis, melting point determinations, molecular weight determinations, IR, ¹H NMR, ¹³C NMR, ¹¹⁹Sn NMR, UV, mass spectral and X‐ray powder diffraction studies. On the basis of these studies it is clear that the ligands coordinated to the metal atom in a monobasic bidentate mode, by X$^{\cap}$ N donor system. Thus, suitable trigonal bipyramidal geometry for penta‐coordinated state and octahedral geometry for hexa‐coordinated state have been suggested for the 1:1 and 1:2 metal compounds. Both the ligands and their complexes have been screened for their antimicrobial, pesticidal and nematicidal activities. Copyright © 2011 John Wiley & Sons, Ltd.     

Mechanistic models for the intramolecular hydroxycarbene–formaldehyde conversion and their intermolecular interactions: Theory and chemistry of radicals,mono‐, and dications of hydroxycarbene and related configurations

We have studied with theoretical and mechanistic models the intramolecular 1,2‐hydrogen shift in trans‐hydroxycarbene‐formaldehyde and trans‐methylhydroxycarbene‐acetaldehyde/vinyl alcohol, and the corresponding intermolecular complexation between hydroxycarbene (cis and trans) with formaldehyde. The purpose of our work is making an analysis of the proposed intramolecular hydrogen shifts mainly based on thermodynamic principles and the product selectivity on monochromatic irradiation of trans‐hydroxycarbene in carbon monoxide and molecular hydrogen, and formaldehyde. A geometric visualization of the various intermolecular complexes between hydroxycarbene and formaldehyde, based on ab initio results, is demonstrated and discussed with a concept abstracted from the van't Hoff dynamics for a regular tetrahedron in which the interstitial carbon changes its position from tetrahedral into a trigonal‐bipyramidal configuration. This concept has been also used for interactions via proton transfer, concretized as hydrogen‐bonded complexation in hydroxycarbene‐formaldehyde. With the introduced definitions for various van't Hoff ratio numbers, it was possible to judge the ab initio results of the intermolecular complexes between the hydroxycarbenes and formaldehyde. To make an eye‐opener, we discuss the role of the carbene lone pair in hydroxycarbene extended to the formation of mono‐ and dications demonstrating intermediates or transition states with an exclusive mechanistic behavior. Especially, substituted diaryl methylene dications are of interest for nucleophilic substitution reactions, which occur via an in‐plane tetracoordinate carbon intermediate, showing coherence with the orbital organization of methylene dications. A reaction of this type differs fundamentally from the classical S reaction. © 2012 Wiley Periodicals, Inc.     

Perylene‐based Solution‐processable Conjugated Molecules for Optoelectronic Applications: Synthesis and Comparison of Different Substituents on the Optical,Thermal, and Electrochemical Properties

A series of small organic molecules were synthesized by exploiting the bay and imide positions of the perylene nucleus. The synthesized compounds 1 – 11 were characterized by spectroscopic and elemental analyses. These molecules show yellowish color in solution and are highly soluble in dichloromethane. Compound 7 shows a bandgap of 1.7 eV and a Stokes shift of 27. From these results, we infer that this compound can serve as structural template in the design of organic electronics. Moreover, compound 7 shows higher T_d (370°C) and T_g (132°C) values, which reflect its high thermal stability.     

Immobilization of cerium (IV) and erbium (III) in mesoporous MCM‐41: Two novel and highly active heterogeneous catalysts for the synthesis of 5‐substituted tetrazoles,and chemo‐ and homoselective oxidation of sulfides

Two well‐ordered 2D ‐ hexagonal cerium (IV) and erbium (III) embedded functionalized mesoporous MCM ‐ 41(MCM‐41@Serine/Ce and MCM ‐ 41@Serine/Er) have been developed via functionalization of mesoporous MCM ‐ 41. The surface modification method has been used in the preparation of serine‐grafted MCM ‐ 41 and led to the development of MCM‐41@Serine. The reaction of MCM‐41@Serine with Ce (NH₄)₂(NO₃)₆·2H₂O or ErCl₃·6H₂O in ethanol under reflux led to the organization of MCM‐41@Serine/Ce and MCM‐41@Serine/Er catalysts. The structures of these catalysts were determined using scanning electron microscopy, mapping, energy‐dispersive X‐ray spectroscopy, Fourier transform‐infrared, thermogravimetric analysis, X‐ray diffraction, inductively coupled plasma, and Brunauer–Emmett–Teller analysis. These MCM‐41@Serine/Ce and MCM‐41@Serine/Er catalysts show outstanding catalytic performance in sulfides oxidation and synthesis of 5‐substituted tetrazoles. These catalysts can be recycled for seven repeated reaction runs without showing a considerable decrease in catalytic performance.