Au-TiO2/Chit modified sensor for electrochemical detection of trace organophosphates insecticides

In this paper, Au–TiO₂/Chit modified electrode was prepared with Au–TiO₂ nanocomposite (Au–TiO₂) and Chitosan (Chit) as a conjunct. The Au–TiO₂ nanocomposite and the films were characterized by electrochemical and spectroscopy methods. A set of experimental conditions was also optimized for the film's fabrication. The electrochemical and electrocatalytic behaviors of Au–TiO₂/Chit modified electrode to trace organophosphates (OPs) insecticides such as parathion were discussed in this work. By differential pulse voltammetry (DPV) measurement, the current responses of Au–TiO₂/Chit modified electrode were linear with parathion concentration ranging from 1.0 ng/ml to 7.0 × 10³ ng/ml with the detection limit of 0.5 ng/ml. In order to evaluate the performance of the detection system, we also examined the real samples successfully in this work. It exhibited a sensitive, rapid and easy-to-use method for the fast determination of trace OPs insecticides.     

Fabrication and characterization of γ-Al2O3–clay composite ultrafiltration membrane for the separation of electrolytes from its aqueous solution

In this paper, we have reported the preparation of low cost γ-Al₂O₃ membrane on a macroporous clay support by dip-coating method. For the synthesis of γ-Al₂O₃ top layer on the support, a stable boehmite sol is prepared using aluminium chloride salt as a starting material by sol–gel route. The structural properties of the composite membrane as well as γ-Al₂O₃ powder is carried out using scanning electron microscopy (SEM), X-ray diffraction (XRD), nitrogen adsorption–desorption isotherm data, Fourier transform infrared analysis (FTIR) and dynamic light scattering (DLS) analysis. The mean particle size of the boehmite sol used for coating is found to be 30.9 nm. The pore size distribution of the γ-Al₂O₃–clay composite membrane is found to be in the range of 5.4–13.6 nm. Separation performance of the membrane in terms of flux and rejection of single salts solution such as MgCl₂ and AlCl₃ as a function of pH, salt concentration and applied pressure is also studied. The rejection and flux behavior are found to be strongly dependent on electrostatic interaction between the charged molecules and γ-Al₂O₃–clay composite membrane. The intrinsic rejection has been determined by calculating the concentration at membrane surface (C_m) using Speigler–Kedem model. It is found that the observed rejection shows anomalous trend with increase in applied pressure and the intrinsic rejection increases with increase in applied pressure, a trend typical of the separation of electrolyte through charged membranes. At acidic pH, both the salt solution shows higher rejection. With increase in the salt concentration, observed rejection of salt decreases due to the enhanced concentration polarization. The maximum rejection of MgCl₂ and AlCl₃ is found to be 72% and 88%, respectively for salt concentration of 3000 ppm.     

Synthesis and electrophoretic deposition of high-dielectric-constant SrTiO3 nanoparticles

We have investigated on the synthesis of SrTiO₃ nanoparticles whose bulk exhibits dielectric constant of 300, and their colloidal dispersion. As a result, we successfully synthesized SrTiO₃ nanoparticles with an average diameter of 134–485 nm measured by a scanning electron microscopic observation. The SrTiO₃ nanoparticles with a negative charge (ζ = −25 to −31 mV) can be dispersed as colloidal nanoparticles in water, and the average diameter in the dispersion were 138–356 nm measured by a dynamic light scattering technique. The colloidal dispersion of SrTiO₃ nanoparticles is promising for fabrication of low-voltage organic field-effect transistors (FETs) by a wet-processing fabrication. We have also successfully prepared SrTiO₃ films with a thickness of 1–10 μm on n-doped silicon substrates by an electrophoretic deposition technique. The SrTiO₃ films on the silicon substrates are likely used as dielectric gate insulator to low-voltage organic FETs after a sintering treatment.     

In situ chemical synthesis of SnO2–graphene nanocomposite as anode materials for lithium-ion batteries

An in situ chemical synthesis approach has been developed to prepare SnO₂–graphene nanocomposite. Field emission scanning electron microscopy and transmission electron microscopy observation revealed the homogeneous distribution of SnO₂ nanoparticles (4–6 nm in size) on graphene matrix. The electrochemical reactivities of the SnO₂–graphene nanocomposite as anode material were measured by cyclic voltammetry and galvanostatic charge/discharge cycling. The as-synthesized SnO₂–graphene nanocomposite exhibited a reversible lithium storage capacity of 765 mAh/g in the first cycle and an enhanced cyclability, which can be ascribed to 3D architecture of the SnO₂–graphene nanocomposite.     

Fabrication of mesoporous SiO2–C–Fe3O4/γ–Fe2O3 and SiO2–C–Fe magnetic composites

A synthetic method for the fabrication of silica-based mesoporous magnetic (Fe or iron oxide spinel) nanocomposites with enhanced adsorption and magnetic capabilities is presented. The successful in situ synthesis of magnetic nanoparticles is a consequence of the incorporation of a small amount of carbon into the pores of the silica, this step being essential for the generation of relatively large iron oxide magnetic nanocrystals (10 ± 3 nm) and for the formation of iron nanoparticles. These composites combine good magnetic properties (superparamagnetic behaviour in the case of SiO₂–C–Fe₃O₄/γ–Fe₂O₃ samples) with a large and accessible porosity made up of wide mesopores (>9 nm). In the present work, we have demonstrated the usefulness of this kind of composite for the adsorption of a globular protein (hemoglobin). The results obtained show that a significant amount of hemoglobin can be immobilized within the pores of these materials (up to 180 mg g⁻¹ for some of the samples). Moreover, we have proved that the composite loaded with hemoglobin can be easily manipulated by means of an external magnetic field.     

Porous cobalt oxide (Co3O4) nanorods: Facile syntheses, optical property and application in lithium-ion batteries

We developed a facile synthetic route of porous cobalt oxide (Co₃O₄) nanorods via a microemulsion-based method in combination with subsequent calcination process. The porous structure was formed by controlled decomposition of the microemulsion-synthesized precursor CoC₂O₄ nanorods without destruction of the original morphology. The as-prepared Co₃O₄ nanorods, consisting of small nanoparticles with diameter of 80–150 nm, had an average diameter of 200 nm and a length of 3–5 μm. The morphology and structure of synthesized samples were characterized by transmission electron microscopy and scanning electron microscopy. The phase and composition were investigated by X-ray powder diffraction and X-ray photoelectron spectroscopy. The optical property of Co₃O₄ nanorods was investigated. Moreover, the porous Co₃O₄ nanorods exhibited high electrochemical performance when applied as cathode materials for lithium-ion batteries, which gives them good potential applications.     

Conductivity studies of dense yttrium-doped BaZrO3 sintered at 1325 °C

High-temperature proton conductors have wide applications in the areas of fuel cells, electrolysis and hydrogen separation. Barium zirconate-based materials are of interest due to their good stability and high protonic conductivity. The reported conductivity of these ceramic materials is generally less than 10⁻² S/cm, even at high temperatures. This is not high enough for an electrolyte-supported device to achieve an ASR of less than 0.2 Ω cm² therefore thin film electrolytes are required for successful application. As BaZrO₃-based materials have to be sintered at temperatures as high as 1700 °C, this makes it difficult to find a suitable supporting electrode which will not undergo significant chemical reaction with the BaZrO₃-based electrolyte during fabrication of the required electrode supported electrolyte. In this paper, proton-conducting BaZr_0.8Y_0.2O_2.9 was successfully sintered at 1325 °C with a relative density of 96% via addition of 1 wt% ZnO. Fabrication of electrochemical cells using proton-conducting BaZr_0.8Y_0.2O_2.9 as the electrolyte thus becomes possible. The formula of the 1 wt% ZnO added sample is Ba_0.97Zr_0.77Y_0.19Zn_0.04O_3−δ which exhibits a tetragonal structure with space group P4/mbm (127); a=5.9787(1) Å, c=4.2345(1) Å, V=151.36(1) Å³. It was found that a solid solution was formed for a limited range of Zn doping. Conductivity has been studied as a function of atmosphere (air, dry and wet 5% H₂/Ar) with the changes in bulk and grain boundary on changing atmosphere being monitored as a function of time. The total conductivity of Ba_0.97Zr_0.77Y_0.19Zn_0.04O_3–δ is 1.0×10⁻³ S/cm above 600 °C therefore it may be used as a proton-conducting thin film electrolyte for efficient electrochemical devices at such temperatures. The grain boundary resistance is insignificant at high temperature for the well-sintered sample.     

The High-Temperature Soft Ferromagnetic Molecular Materials Based on [W(CN)6(bpy)]2−/− System

The synthesis of molecular materials with magnetic properties, in particular ferromagnetic properties, has been the subject of interest in coordination chemistry for decades. In the last three decades, research has accelerated, as it has emerged that creating bridging systems based on cyanido ligands is a good and relatively simple way to create complex polymer structures exhibiting magnetic properties. Based on many years of personal experience in the field of the synthesis of polycyanido systems, supported by comprehensive structural analysis, a simple method of transforming cyanido complexes into soft ferromagnetic materials with a Curie temperature (T_C) higher than the thermal decomposition temperature, usually above 150 °C has been developed. Two soft ferromagnetic materials based on zinc and cadmium hexacyanido salts in the system with [W(CN)₆(bpy)]^2−/− anions are presented. The crystal structures (X-ray single crystal as well as XRD) of the precursors and the properties of the ferromagnetic materials are discussed. Most importantly, a patented method of synthesizing this type of material, based on which we obtain more than 80 soft, high-temperature ferromagnetic compounds, which proves the wide spectrum of this method, is also presented.     

Preparation of “pore-fill” type Pd–YSZ–γ-Al2O3 composite membrane supported on α-Al2O3 tube for hydrogen separation

Mesoporous YSZ–γ-Al₂O₃ membranes were coated on α-Al₂O₃ (Ø2 mm) tube by dipping the α-Al₂O₃ support tube into mixed sol consists of nano-size YSZ and bohemite particles followed by drying and calcination at 600 °C. Addition of bohemite in YSZ sol helped a good adhesion and uniform coating of the membrane film onto α-Al₂O₃ support. The quality of the mesoporous YSZ–γ-Al₂O₃ membranes was evaluated by the gas permeability experiments. The number of defects was minimized when the γ-Al₂O₃ content became more than 40%. Addition of γ-Al₂O₃ inhibited the crystal growth of YSZ, sintering shrinkage and distortion stress. Increase of calcination temperature and time results in the increase of pore size and N₂ permeance. A hydrogen perm-selective membrane was prepared by filling palladium into the nano-pores of YSZ–γ-Al₂O₃ layer by vacuum-assisted electroless plating. Crystal growth of palladium was observed by thermal annealing of the membrane at 600 °C for 40 h. The Pd–YSZ–γ-Al₂O₃ composite membrane revealed improved thermal stability allowing long-term operation at elevated temperature (>500 °C). This has been attributed to the improved fracture toughness of YSZ–γ-Al₂O₃ layer and matching of thermal expansion coefficient between palladium and YSZ. Although fracture of the membrane did not occur, decline of H₂ flux was observed when the membrane was exposed in 600 °C. This has been attributed to the agglomeration of palladium particles by crystal growth and dense packing into the pore networks of YSZ–γ-Al₂O₃ by elevation of temperature.     

Fabrication of PLCL Block Polymer with Tunable Structure and Properties for Biomedical Application

Biodegradable materials are pivotal in the biomedical field, where how to precisely control their structure and performance is critical for their translational application. In this study, poly(L-lactide-b-ε-caprolactone) block copolymers (bPLCL) with well-defined segment structure are obtained by a first synthesis of poly(ε-caprolactone) soft block, followed by ring opening polymerization of lactide to form poly(L-lactide acid)  hard block. The pre-polymerization allows for fabrication of bPLCL with the definite compositions of soft/hard segment while preserving the individual segment of their special soft or hard segment. These priorities make the bPLCL afford biodegradable polymer with better mechanical and biodegradable controllability than the random poly(L-lactide-co-ε-caprolactone) (rPLCL) synthesized via traditional one-pot polymerization. 10 mol% ε-caprolactone introduction can result in a formation of an elastic polymer with elongation at break of 286.15% ± 55.23%. Also, bPLCL preserves the unique crystalline structure of the soft and hard segments to present a more sustainable biodegradability than the rPLCL. The combinative merits make the pre-polymerization technique a promising strategy for a scalable production of PLCL materials for potential biomedical application.     

Synthesis of LiFePO4 material with improved cycling performance under harsh conditions

LiFePO₄ material was synthesized at 670 °C in an Ar atmosphere using a sol–gel method. This material showed a well developed XRD pattern (orthorhombic structure, Pnma) without any peaks at 2θ = 41°, indicating the absence of FeP or metallic Fe₂P impurities. The Li/LiFePO₄ cell showed a high initial discharge capacity of more than 150 mA h/g and no capacity decrease until the 70th cycle (>99.9%). This cell also exhibits excellent cycle performance at high current densities of over 30C, without any surface treatment or carbon coating onto the LiFePO₄ particles.     

Preparation and characterization of lithium ion-conducting glass-ceramics in the Li1 + xCrxGe2 − x(PO4)3 system

Li₂O–Cr₂O₃–GeO₂–P₂O₅ based glasses were synthesized by a conventional melt-quenching method and successfully converted into glass-ceramics through heat treatment. Experimental results of DTA, XRD, ac impedance techniques and FESEM indicated that Li_1.4Cr_0.4Ge_1.6(PO₄)₃ glass-ceramics treated at 900 °C for 12 h in the Li_1 + xCr_xGe_2 − x(PO₄)₃ (x = 0–0.8) system exhibited the best glass stability against crystallization and the highest ambient conductivity value of 6.81 × 10⁻⁴ S/cm with an activation energy as low as 26.9 kJ/mol. In addition, the Li_1.4Cr_0.4Ge_1.6(PO₄)₃ glass-ceramics displayed good chemical stability against lithium metal at room temperature. The good thermal and chemical stability, excellent conducting property, easy preparation and low cost make it promising to be used as solid-state electrolytes for all-solid-state lithium batteries.     

Biodegradable elastomers for tissue engineering and cell-biomaterial interactions

Synthetic biomaterials serve as a cornerstone in the development of clinically focused regenerative medicine therapies that aim to reduce suffering and prolong life. Recent improvements in biodegradable elastomeric materials utilize natural extracellular matrix proteins as inspiration to yield a new class of materials with superior degradation kinetics, desirable biocompatibility profiles, and mechanical properties that closely match those of soft tissues. This review describes several classes of synthetic biodegradable elastomers and associated fabrication techniques that are relevant to scaffold development. The application of these materials to select tissue engineering models is also discussed.     

Electrophoretic deposition of hydroxyapatite–CaSiO3–chitosan composite coatings

Electrophoretic deposition (EPD) method has been developed for the fabrication of hydroxyapatite (HA)–CaSiO₃ (CS)–chitosan composite coatings for biomedical applications. The use of chitosan enabled the co-deposition of HA and CS particles and offered the advantage of room temperature processing of composite materials. The coating composition was varied by the variation of HA and CS concentrations in the chitosan solutions. Cathodic deposits were obtained as HA–CS–chitosan monolayers, HA–chitosan/chitosan multilayers or functionally graded materials (FGM) containing HA–chitosan and CS–chitosan layers of different composition. The thickness of the individual layers was varied in the range of 0.1–20 μm. The deposition yield was studied at different experimental conditions and compared with the results of modeling. It was shown that the moving boundary model for the two component system can explain the non-linear increase in the deposition yield with increasing HA concentration in chitosan solutions. The obtained coatings were studied by thermogravimetric analysis (TGA), differential thermal analysis (DTA) and scanning electron microscopy (SEM). Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) studies showed that these coatings provided corrosion protection of stainless steel substrates in Ringer's physiological solution. The deposition mechanism and kinetics of deposition have been discussed.     

XPS and XRD study of FeCl3-graphite intercalation compounds prepared by arc discharge in aqueous solution

A novel one-step synthesis method of FeCl₃–graphite intercalation compounds (FeCl₃–GICs) by an arc discharge in aqueous solution was reported for the first time. It presented a simply and controllable way to synthesize FeCl₃–GICs. The structure of the stage 7 GICs was examined and characterized by X-ray diffraction. X-ray photoelectron spectroscopic study of stage 7 of FeCl₃–GICs was also carried out. The change in the binding energy suggests the nature of charge transfer and lowering of Fermi level as has been reported previously for other acceptor intercalation compounds.     

Mesoporous MnO2 as enzyme immobilization host for amperometric glucose biosensor construction

Mesoporous MnO₂ (mesoMnO₂) is synthesized facilely through sol–gel process using nonionic surfactant polyxyethylene fatty alcohol (AEO₉) as template. Transmission electron microscopy (TEM) image and N₂ adsorption/desorption isotherm show that the obtained mesoMnO₂ material presents disordered porous structure and appropriate pore size suitable for the immobilization of glucose oxidase (GOx). An amperometric glucose biosensor based on GOx entrapped in mesoMnO₂ is fabricated, in which mesoMnO₂ also acts as a catalyst for the electrochemical oxidation of H₂O₂ produced by enzyme reaction. The biosensor shows fast and sensitive current response to glucose in the linear range of 0.0009–2.73 mM. The response time (t_95%) is less than 7 s. The sensitivity and detection limit are 24.2 μA cm⁻² mM⁻¹ and 1.8 × 10⁻⁷ M (S/N = 3), respectively. This indicates that mesoMnO₂ has promising application in enzyme immobilization and biosensor construction.     

Bioactive ceramics in the CaO-Al2O3-P2O5-ZnO system prepared by the sol-gel technology

The sol-gel method was applied to the synthesis of porous bioactive glass-ceramic materials in the Ca-Al₂O₃-P₂O₅-ZnO system when compositions were chosen in the glass formation range. Aluminium sol and soluble inorganic salts of the other components have been used as starting materials. The sol-gel transition was achieved by controlling the pH value of the medium. After drying the gel products were thermally treated up to 800°C, Phase formation was studied by X-ray diffraction, IR spectroscopy and electron microscopy.It was found that the main crystalline phases in the glass ceramics were C(PO₃)₂ and Ca₂P₂O₇. The amorphous powder was sintered to form ceramic materials with average pore size distribution of 150–200 µm by isostatic pressing and heat treatment at 500–600°C. This glass ceramic is more bioactive than hydroxylapatite in the initial stage after implantation.     

Promoting effect of Mg in supported Mo/HBeta–Al2O3 catalyst for cross-metathesis of ethene and butene-2 to propene

Promoting effects of Mg in heterogeneous Mo/HBeta–Al₂O₃ catalyst have been carefully studied for cross-metathesis of ethene and butene-2 to propene. The catalyst shows good stability with Mg content in the range of 1–2 wt%. Such effect may be attributed to the elimination of weak acid sites through introduction of Mg which suppresses the side olefin oligomerization reaction, as evidenced from NH₃-TPD and ¹H MAS NMR results. Addition of more Mg content to 3 wt% may change the state and reducibility of Mo species, as indicated from the UV–vis, UV-Raman and H₂-TPR measurements. The increasing difficulty for the reduction of Mo(VI) species is closely related with the poor performance of 3 wt% Mg–4Mo/HBeta–30% Al₂O₃ catalyst in the metathesis reaction.     

Cuttlebone-derived organic matrix as a scaffold for assembly of silver nanoparticles and application of the composite films in surface-enhanced Raman scattering

Biologically derived materials provide a rich variety of approaches toward new functional materials because of their fascinating structures and environment-friendly features, which is currently a topic of research interest. In this paper, we show that the cuttlebone-derived organic matrix (CDOM) is an excellent scaffold for the one-step synthesis and assembly of silver nanoparticles (AgNPs), which can be further used as substrate for surface-enhanced Raman scattering (SERS). Formation of AgNPs–CDOM composite was accomplished by the reaction of CDOM with AgNO₃ and NH₃·H₂O solution at 80 °C without using any other stabilizer and reducing agents. UV–vis spectra and TEM were utilized to characterize the AgNPs and investigate their formation process. Results demonstrate that the size and distribution of AgNPs can be partly regulated by changing incubation time; the concentration of NH₃·H₂O is critical to the formation rate of AgNPs. As a proof of principle, we show that the AgNPs–CDOM composite can be employed in trace analysis using SERS.     

Enhanced overcharge behavior and thermal stability of commercial LiCoO2 by coating with a novel material

Commercial LiCoO₂ has been modified with MnSiO₄ as a novel coating material. The structures, morphologies, overcharge behaviors and thermal stabilities of the pristine and MnSiO₄-coated LiCoO₂ materials were studied. The MnSiO₄-coated LiCoO₂ had initial discharge specific capacities of 181.1 and 232.2 mAh g⁻¹ within the potential ranges 2.75–4.5 and 2.75–4.7 V (vs. Li⁺/Li), respectively. It was found that the overcharge tolerance of the coated cathode was significantly better than that of the pristine LiCoO₂ under the same conditions – the discharge specific capacities of the coated cathode at upper charge cutoff voltages of 4.5 and 4.7 V were as high as 168.7 and 154.3 mAh g⁻¹, respectively, after 50 cycles. Moreover, DSC showed that the coated LiCoO₂ had a higher thermal stability than the pristine LiCoO₂.