Physicochemical properties and sensing ability of metallophthalocyanines/chitosan nanocomposites

Electroactive nanostructured films of chitosan (Ch) and tetrasulfonated metallophthalocyanines containing nickel (NiTsPc), copper (CuTsPc), and iron (FeTsPc) were produced via the electrostatic layer-by-layer (LbL) technique. The multilayer formation was monitored with UV-vis spectroscopy by measuring the increase of the Q-band absorption from metallophthalocyanines. Results from transmission and reflection infrared spectroscopy suggested specific interactions between SO(3)(-) groups from metallophthalocyanines and NH(3)(+) from chitosan. The electroactive multilayered films assembled onto an ITO electrode were characterized by cyclic voltammetry, with Ch/NiTsPc films showing higher stability and well-defined voltammograms displaying reversible redox peaks at 0.80 and 0.75 V. These films could be used to detect dopamine (DA) in the concentration range from 5.0 x 10(-6) to 1.5 x 10(-4) mol L(-1). Also, ITO-(Ch/NiTsPc)(n)() electrodes showed higher electrocatalytic activity for DA oxidation when compared with a bare ITO electrode. On the other hand, only the Ch/FeTsPc and Ch/CuTsPc modified electrodes could distinguish between DA and ascorbic acid. These results demonstrate that versatile electrodes can be prepared by incorporation of different metallophthalocyanine molecules in LbL films, which may be used in bioanalytical applications.     

Imidazole-containing chitosan derivative: a new synthetic approach and sorption properties

A novel method for the synthesis of a hetaryl-containing chelate amino polymer, namely, N-(4(5)-imidazolylmethyl)chitosan (IMC), with a degree of substitution up to 0.3 was proposed. The “synthesis in gel” approach involves direct substitution of the hydroxyl group in 4(5)-imidazolylmethanol. The structures of these polymers were confirmed by ¹H NMR data. For sorption studies, IMC samples were crosslinked with epichlorohydrin and diglycidyl ethers of ethylene glycol and diethylene glycol. The degrees of swelling and sorption properties of the polymers largely depend on the crosslinking agent and the degree of crosslinking. The sorption capacities of IMC for Au^III, Pt^IV, and Pd^II ions are higher than those of the nonmodified polymer. The extraction of noble metal ions from chloride solutions becomes more selective with increasing degree of crosslinking. The sorption capacity of IMC for Co^II and Ni^II ions is higher than those of chitosan and its known N-heterocyclic derivatives.     

A one-pot synthetic approach to prepare palladium nanoparticles embedded hierarchically porous TiO2 hollow spheres for hydrogen peroxide sensing

A simple one-step method to fabricate hierarchically porous TiO₂/Pd composite hollow spheres without any template was developed by using solvothermal treatment. Pd nanoparticles (2-5 nm) were well dispersed in the mesopores of the TiO₂ hollow spheres via in-situ reduction. In our experiment, polyvinylpyrrolidone played an important role in the synthetic process as the reducing agent and the connective material between TiO₂ and Pd nanoparticles. HF species generated from solvothermal reaction leaded to the formation of TiO₂ hollow spheres and Ostwald ripening was another main factor that affected the size and structure of the hollow spheres. The as-prepared TiO₂/Pd composite hollow spheres exhibited high electrocatalytic activity towards the reduction of H₂O₂. The sensitivity was about 226.72 μA mM⁻¹ cm⁻² with a detection limit of 3.81 μM at a signal-to-noise ratio of 3. These results made the hierarchically porous TiO₂/Pd composite a promising platform for fabricating new nonenzymic biosensors.     

A green approach to prepare Ag NPs loaded IC/PVA polymeric film for antimicrobial applications

In this study, glyoxal-cross-linked Iota carrageenan (IC) /poly(vinyl alcohol) PVA films were prepared and loaded with silver nanoparticles via a green approach, consisting of sweet lime juice induced in-situ reduction of Ag(I) ions to nano silver within the film matrix. The formation of silver nanoparticles was confirmed using UV–visible spectrophotometry. The Ag NPs-loaded films were also characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR). The dynamic water uptake data were interpreted by the ‘Power functional model’. The films showed fair antimicrobial action against bacteria E. Coli.     

A convenient new method to construct 1-alkynyl cyclopropanol and its synthetic application to prepare trisubstituted dienones

A new synthetic route was developed via the nucleophilic addition of lithium alkynylide to 1-arylsulfonyl cyclopropanol 1 to afford 1-alkynyl cyclopropanol, which then reacted with aryl iodide to construct trisubstituted cross-conjugated dienones through a palladium-catalyzed process, where the key steps included the regioselective carbopalladation of arylpalladium(II) intermediate across the triple bond of 1-alkynyl cyclopropanol and the ring opening of the cyclopropyl group.     

The synthesis and optical properties of the heterostructured ZnO/Au nanocomposites

ZnO/Au heterostructured nanoparticles were formed through epitaxial growth of Au on the ZnO seeds. The morphology and structure of ZnO/Au nanocomposites were investigated by TEM and XRD analysis. The nanocontact between Au and ZnO results in red-shift of surface plasmon of the Au and increase the intensity of Raman signals of ZnO. Heterostructured ZnO/Au nanocomposites also enhance chemical stability of ZnO in aqueous solution.     

Organic–inorganic polypyrrole‐surface modified SiO2 hybrid nanocomposites: a facile and green synthetic approach

Organic–inorganic hybrid nanocomposites composed of conductive polypyrrole (PPy) and surface modified silica (SiO₂) were successfully prepared through an in situ chemical oxidative polymerization in supercritical carbon dioxide (scCO₂). SiO₂ nanoparticles were surface modified using 3‐methacryloxypropyltrimethoxysilane (MPTMS) in order to disperse well in the medium. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) showed that the SiO₂ nanoparticles were encapsulated into the polymer. UV‐visible spectra of the diluted colloidal dispersions of PPy/SiO₂ hybrid nanocomposites were similar to those of PPy system. Fourier transform infrared spectroscopy (FT‐IR) suggested the strong interaction between PPy and SiO₂. Surface characterizations of nanocomposites were described by X‐ray photoelectron spectroscopy (XPS). The nanocomposites synthesized in scCO₂ have been shown to possess higher electrical conductivity and thermal stability. Copyright © 2009 John Wiley & Sons, Ltd.     

Ultrasonically assisted in situ emulsion polymerization: a facile approach to prepare conducting copolymer/silica nanocomposites

Ultrasonically assisted in situ emulsion polymerization was used to prepare electrically conducting copolymer poly(aniline‐co‐p‐phenylenediamine) [poly(Ani‐co‐pPD)] and silica (SiO₂) nancomposites. This approach can solve problems in the dispersion and stabilization of SiO₂ nanoparticles in the copolymer matrix. It was found that the aggregation of SiO₂ nanoparticles could be reduced under ultrasonic irradiation. Scanning transmission electron microscopy (STEM) confirmed that the resulting poly(Ani‐co‐pPD)/SiO₂ nanocomposite particles were spherical in shape, in which SiO₂ nanoparticles were well dispersed. The comonomer molecules were absorbed on the surface of SiO₂ particles and then polymerized to form core–shell nanocomposite. The incorporation of SiO₂ in the nanocomposite was supported by Fourier transform infrared spectroscopy (FT‐IR). UV‐visible spectra of the diluted colloid dispersion of nanocomposite particles were similar to those of the neat copolymer. Conductivity of nanocomposites was higher than the value obtained for the neat copolymer. Copyright © 2009 John Wiley & Sons, Ltd.     

Cerium-doped mesoporous BaTiO3/TiO2 nanocomposites: structural,optical and photocatalytic properties

Research on Chemical Intermediates - Nanoscale composite materials based on cerium, barium titanate and titanium dioxide were synthesized by thermal hydrolysis. The obtained individual TiO2, BaTiO3...     

A new approach to preparation of granulated materials based on chitosan and its imidazole derivative

A new approach to preparation of granulated materials based on chitosan and N-(5-methyl-4-imidazolyl)- methyl chitosan was developed. The procedure is simple and efficient and involves the use of glutaraldehyde as cross-linking agent without using precipitants. The composition and structural features of the materials obtained were determined by elemental analysis and Fourier IR spectroscopy. The dependence of the degree of material swelling on the degree of functionalization with glutaraldehyde was determined. The polymer granules were used as support for Pd0-containing catalysts for reduction of organic compounds.     

Novel synthetic approach for optical resolution of cryptophanol-A: a direct access to chiral cryptophanes and their chiroptical properties

The separation by crystallization of the pair of cryptophane diastereomers 1 a and 1 b, obtained in 1:1 ratio by treating racemic anti cryptophanol-A (2) with (-)-camphanic acid chloride, provided a substantial amount of optically pure material (diastereomeric excess>98 %). Subsequent hydrolysis afforded the optically pure cryptophanol-A enantiomers (+)-2 and (-)-2, which were submitted to nucleophilic substitution reactions to provide cryptophane-A (+)-3 and cryptophane monoester (-)-4 in optically pure form. The chiroptical properties of the new cryptophanes 1-4 were investigated by using circular dichroism spectroscopy, and the absolute configuration of the molecules was clearly established. These new cryptophanes represent additional interesting examples for studying the Cotton effect of interacting multichromophoric systems. Moreover, this novel approach presents numerous advantages over the other methods developed so far to obtain optically pure cryptophanes, and compounds (-)-2, (+)-2, and (-)-4 can give access to new enantiopure functionalized cryptophanes with host-guest properties similar to those of cryptophane-A.     

Single-source approach to cubic FeS2 crystallites and their optical and electrochemical properties

Cubic FeS2 crystallites have been synthesized via a single-source approach using iron diethyldithiocarbamate as precursor under hydrothermal conditions. The sample is characterized by XRD, IR, TEM, and FESEM. The optical properties of the as-prepared FeS2 reveal that there exists a red shift compared with that of bulk materials. Meanwhile, the electrochemical properties of FeS2 demonstrate that it delivers a large discharge capacity, which might find possible application as an electrode material in lithium cells. It is also found that the reaction temperature is of importance to the formation of cubic FeS2 crystallites.     

A new synthetic approach for 4(S)-hydroxycyclopent-2-enone: a precursor to prostanoid synthesis

A new and efficient approach to 4(S)-hydroxycyclopent-2-enone is presented. This methodology allows the preparation of 4(S)-hydroxycyclopent-2-enone in large scale and with high optical purity.     

Graphene and its nanocomposites used as an active materials for supercapacitors

This review article investigates the hot topics by presenting the latest advances on graphene-based nanostructures for supercapacitors. In literature, many scientists have studied the nanomaterials and combination of conducting polymers in supercapacitor (SC) devices. The main aim of this review article is to present the higher capacitance, and higher power and energy density performances of the SC devices, which includes the active materials of carbon-based materials, metal oxides, conducting polymers, nanocomposites, etc. Many conventional techniques have already been used such as photolithography, inkjet printing, etc. Each of these methods has specific advantages and some drawbacks, with some working better in different environments. Among various nanoscaled materials, nanocrystal oxides of transition metals play an important role in advanced materials development. In addition to design of active material, symmetric and asymmetric supercapacitor device fabrication is also directly effect to obtain a higher capacitance, energy and power density performances. Therefore, this review article focuses on supercapacitor technology in new developments, such as design of active materials, device fabrication, etc.     

Electrodeposition of chitosan enables synthesis of copper/carbon composites for H2O2 sensing

This work presents a novel approach in synthesizing copper (Cu)/carbon composite materials by electrodeposition of the biopolymer chitosan, a renewable carbon precursor, on a copper anode, followed by pyrolysis of the electrodeposited chitosan gel. The amount of copper in the Cu/carbon composite material can be controlled by modifying the pH of the chitosan solution from which the electrodeposition is performed. This further influences the physical properties of the composite material. Here we show a 14 fold increase in electrical conductivity of the Cu/carbon composite, when compared to the material without copper inclusions. Metal/carbon composite materials have a wide range of applications already reported in the literature. As a proof of concept, we demonstrate the electrochemical sensing capability of this Cu/carbon material for non-enzymatic detection of hydrogen peroxide, achieving a sensitivity of 58.9 μA/mM cm², which is comparable to state of the art non-enzymatic hydrogen peroxide sensors. The anodic electrodeposition of chitosan proves to be a simple and straightforward medium for synthesis of Cu/carbon composites. We speculate that this method can be extended to obtain other metal/carbon composites as a low-cost alternative for the fabrication of functional composite electrodes.     

A simple and green route to transparent boron nitride/PVA nanocomposites with significantly improved mechanical and thermal properties

A simple and green method is developed to prepare hexagonal boron nitride(h-BN)/poly(vinyl alcohol) (PVA) nanocomposites by using water as a common solvent of h-BN nanosheets and PVA.The obtained h-BN/PVA nanocomposites are highly transparent,and have significantly improved mechanical and thermal properties.They may outperform nano-clay and nano-alumina/PVA nanocomposites as flexible optoelectronic devices,optical windows and heat-releasing materials operated in oxidative or corrosive environment.     

2-吡啶甲醛改性壳聚糖的合成及螯合性能的研究

以壳聚糖为主体,2-吡啶甲醛为配体,经Schiff碱反应对壳聚糖进行修饰,合成了具有高螯合性能的2-吡啶甲醛缩壳聚糖(PYCTS)。采用正交实验法研究,并得到了缩合反应的最佳条件:溶胀温度为65℃,反应物的配比(壳聚糖与2-吡啶甲醛的摩尔比)为1:4,溶液pH值为6.0,反应时间为12h。经红外光谱表征了其结构。最高缩合率为97.5%。并研究了2-吡啶甲醛改性壳聚糖(PYCTS)对Cu(Ⅱ)、Ni(Ⅱ)、Co(Ⅱ)、Fe(Ⅲ)离子的静态螯合性能,以及介质种类、介质酸度、金属离子浓度和螯合时间对PYCTS螯合金属离子能力的影响。结果表明,在pH为3~8时,其对Cu(Ⅱ)、Ni(Ⅱ)、Co(Ⅱ)具有较好的螯合性能,且介质种类和介质酸度对PYCTS螯合金属离子能力的影响较大。     

双马来酰亚胺树脂/SiO_2纳米复合材料的制备及性能

以表面含有胺基官能团的纳米SiO_2为填料,通过一步原位聚合法制备双马来酰亚胺树脂/SiO_2纳米复合材料(BMI/SiO_2).采用热重分析仪(TGA)、红外光谱分析仪(FTIR)、邵氏D硬度计(H)等仪器设备对BMI/SiO_2纳米复合材料进行测试分析,探讨纳米SiO_2对双马来酰亚胺聚酯树脂的热稳定性能、硬度和界面强度的影响.结果表明,所制备的BMI/SiO_2纳米复合材料的硬度随加入的纳米SiO_2含量的增加,呈现逐渐升高趋势.当纳米SiO_2含量为3%时,相对于双马来酰亚胺聚酯,复合材料的硬度提高了80%.通过热稳定性分析可知,纳米SiO_2的加入降低了双马来酰亚胺树脂基体材料的热分解温度,使其从458℃降低到451℃.通过对双马来酰亚胺/SiO_2纳米复合材料的界面分析发现,纳米SiO_2的表面接枝了双马来酰亚胺分子链,说明纳米SiO_2参与了双马来酰亚胺的聚合过程,有利于提高聚合物基体材料与填料间的界面强度,进而提高复合材料的机械性能.     

Chemical synthesis of MnFe2O4/chitosan nanocomposites for controlled release of ofloxacin drug

In this study, we synthesized ofloxacin‐loaded MnFe₂O₄ nanoparticles (NPs) surface modified with chitosan (CS‐MnFe₂O₄) for prolonged antibiotic release in a controlled manner. It was found that the synthesized CS‐MnFe₂O₄ was spherical in shape with an average size of 30–50 nm, low aggregation, and good magnetic responsibility. An in vitro drug loading and release kinetics study reveals that the drug delivery system can take 86% of drug load and can release ofloxacin over a sustained period of 3 days. The release kinetics study reveals that the drug follows zero order kinetics and the mechanism of drug release is diffusion‐controlled type. These results indicated that CS‐MnFe₂O₄ NPs with pH‐sensitive properties can be used as candidates for intestinal targeted drug delivery through oral administration by avoiding the drug release in the highly acidic gastric fluid region of the stomach.