An activated microporous carbon prepared from phenol-melamine-formaldehyde resin for lithium ion battery anode

Microporous carbon anode materials were prepared from phenol-melamine-formaldehyde resin by ZnCl₂ and KOH activation. The physicochemical properties of the obtained carbon materials were characterized by scanning electron microscope, X-ray diffraction, Brunauer–Emmett–Teller, and elemental analysis. The electrochemical properties of the microporous carbon as anode materials in lithium ion secondary batteries were evaluated. At a current density of 100 mA g^?1, the carbon without activation shows a first discharge capacity of 515 mAh g^?1. After activation, the capacity improved obviously. The first discharge capacity of the carbon prepared by ZnCl₂ and KOH activation was 1010 and 2085 mAh g^?1, respectively. The reversible capacity of the carbon prepared by KOH activation was still as high as 717 mAh g^?1 after 20 cycles, which was much better than that activated by ZnCl₂. These results demonstrated that it may be a promising candidate as an anode material for lithium ion secondary batteries.     

Potentiometric urea biosensor based on multi-walled carbon nanotubes (MWCNTs)/silica composite material

A novel potentiometric urea biosensor has been fabricated with urease (Urs) immobilized multi-walled carbon nanotubes (MWCNTs) embedded in silica matrix deposited on the surface of indium tin oxide (ITO) coated glass plate. The enzyme Urs was covalently linked with the exposed free –COOH groups of functionalized MWCNTs (F-MWCNTs), which are subsequently incorporated within the silica matrix by sol–gel method. The Urs/MWCNTs/SiO₂/ITO composite modified electrode was characterized by Fourier transform infrared (FTIR) spectroscopy, thermal gravimetric analysis (TGA) and UV–visible spectroscopy. The morphologies and electrochemical performance of the modified Urs/MWCNTs/SiO₂/ITO electrode have been investigated by scanning electron microscopy (SEM) and potentiometric method, respectively. The synergistic effect of silica matrix, F-MWCNTs and biocompatibility of Urs/MWCNTs/SiO₂ made the biosensor to have the excellent electro catalytic activity and high stability. The resulting biosensor exhibits a good response performance to urea detection with a wide linear range from 2.18 × 10^? 5 to 1.07 × 10^? 3 M urea. The biosensor shows a short response time of 10–25 s and a high sensitivity of 23 mV/decade/cm².     

Influence of carbon precursors on thermal plasma assisted synthesis of SiC nanoparticles

Nanosized SiC was synthesized by solid state method using silicon and carbon powders followed by non-transferred arc thermal plasma processing. X-ray diffraction (XRD) analysis revealed that activated carbon has highest reactivity while graphite has lowest activity in the crystallization of SiC through solid state method. The reactivity was dependent on surface area of carbon source and activated carbon with highest surface area (590.18 m² g⁻¹) showed highest reactivity, whereas graphite with least surface area (15.69 m² g⁻¹) showed lowest reactivity. The free silicon content was decreased with increasing reaction time as well as carbon mole ratio. Scanning electron microscope (SEM) study showed that the shape and size of synthesized SiC depends on the shape and size of carbon source. SiC nanoparticles within 500 nm were formed for carbon black while bigger particles (∼5 μm) were formed for activated carbon and graphite. Plasma processing of these solid–solid synthesized SiC resulted into the formation of well dispersed, ultrafine SiC nanoparticles (30–40 nm) without any structural modification. Thermal plasma processing resulted into the increase in crystallite size of SiC.     

Synthesis and characterization of an energetic three-dimensional metal–organic framework with blue photoluminescence

A new inorganic–organic hybrid lead(II) coordination polymer [PbCl(tza)]_n (Htza = tetrazole-1-acetic acid) has been synthesized under hydrothermal condition. The complex was characterized by elemental analysis, FT-IR spectroscopy, single-crystal X-ray analysis, thermogravimetric analysis (TG) and differential scanning calorimetry thermal analysis (DSC). The Pb(II) centers are connected through both the tza and Cl^? bridging ligands to form a three-dimensional metal–organic framework (MOF). The compound has been found to exhibit blue photoluminescence in the solid state at room temperature and may be good candidates for photoactive materials. DSC thermal analysis shows the complex is an energetic coordination compound and tza can be used as an energetic ligand.     

Non-cytotoxic organic–inorganic hybrid bioscaffolds: An efficient bedding for rapid growth of bone-like apatite and cell proliferation

Synthesis and characterization of organic–inorganic macroporous hybrid scaffolds were investigated. The materials were prepared by combining 2-hydroxyethylmethacrylate (HEMA) and triethoxyvinylsilane (TEVS) chemically modified by Ca^2 + and PO₄^3 ? ions via sol–gel route. In this study we have constructed a sugar-based cracks-free three-dimensional (3D) network with interconnected porous architecture within the range of 150–300 μm and rough topography. The obtained results revealed that both topography and composition of prepared materials allow rapid growth of the bone-like apatite (HAp) layer on their surface after soaking in biological medium. Preliminary studies have shown that hybrids covered by HAp are non-cytotoxic and allow cell proliferation that make them a promising scaffolds in the field of bone regenerative medicine. The materials were mainly characterized by powder X-ray diffraction analysis (PXRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy–energy-dispersive spectroscopy (SEM–EDS) and transmission electron microscopy–energy-dispersive spectroscopy (TEM–EDS).     

Hydrothermal synthesis,characterization and electrical investigation of poly(para-phenylenediamine)/vanadium oxide nanocomposite nanosheets

Sheet-like mesoporous poly(paraphenylenediamine)/vanadium oxide nanocomposite has been synthesized by the hydrothermal process using the vanadium oxide V₂O₅ as inorganic precursor and paraphenylendiamine as reducing and a structure-directing agent. Such techniques as X-ray diffraction (XRD), scanning electron microscopy (SEM), thermal analysis (TG-DTA), Fourier transform infrared spectroscopy (FTIR), Raman Spectroscopy, X-ray photoelectron spectroscopy (XPS) and nitrogen adsorption/desorption isotherms (BET) have been used to characterize the structure, morphology and the texture of the material. The conductivity of the material was measured by complex impedance spectroscopy which increases from 72 × 10^?5 Ω^?1 cm^?1 at 298 K to 95 × 10^?4 Ω^?1 cm^?1 at 493 K. The Arrhenius diagram is not linear, it presents a rupture situated at 407 K and the activation energies’ average values are 0.044 eV and 0.13 eV.     

Determination of residual stresses in SiC monofilament reinforced metal-matrix composites using Raman spectroscopy

Raman spectroscopy has been used to follow the deformation of chemical vapour deposition type SCS-6 and Sigma 1140+ SiC monofilaments and to determine residual stresses in these SiC monofilaments reinforced metal-matrix composites. Raman bands at 1330 and 1600 cm⁻¹ due to carbon have been observed on the monofilament surface and it has been shown that both bands shift linearly to lower wavenumbers during tensile deformation. The residual stresses in SiC monofilament reinforced composites arising from thermal expansion mismatch have also been determined by measuring the shifts of carbon bands from the same monofilaments embedded in a Ti–6Al–4V matrix. The axial residual stresses in the carbon coating are found to be around −850 MPa for the SCS-6 composite and −540 MPa for the Sigma 1140+ composite.     

Ultralow density carbon aerogels with low thermal conductivity up to 2000 °C

Ultralow density (0.052 g cm^?3) carbon aerogels (CAs) were prepared for ultrahigh temperature thermal insulation, and their thermal conductivities were determined by laser flash method. The CAs have a total thermal conductivity as low as 0.601 W m^?1 K^?1, which is only one third of the value for closed-pore carbon foam (CF) with a density of 0.054 g cm^?3, at 2000 °C under 0.15 MPa argon. The solid, gaseous, and radiative conductivities of the CA are all much lower than those of the CF, because of the special nanoporous and pearl-necklace nanoparticle structures of the CA. The ultralow density CA clearly demonstrates its great potentials as thermal insulations for extreme applications.     

Study of physical properties of cobalt oxide (Co3O4) nanocrystals

Cobalt oxide nanocrystals of size 10–15 nm have been prepared by a simple co-precipitation method. The structural investigations have been performed with X-ray diffraction and Transmission Electron Microscopy. Specific surface area of the nanocrystals is 77.5 × 10⁴ cm²/g which have been calculated by X-ray diffraction data. Optical properties are discussed with UV/visible spectroscopy which shows the multiple band gap energies 2.28 eV (O^? II → Co^II) and 1.57 eV (O^? II → Co^III) which suggest the possibility of degeneracy of the valence band. The magnetic behavior is investigated using Vibrating Sample Magnetometer. The Co₃O₄ nanocrystals possess paramagnetic character at room temperature.     

Characterization of carbon nanotubes decorated with NiFe2O4 magnetic nanoparticles as a novel electrochemical sensor: Application for highly selective determination of sotalol using voltammetry

A magnetic nano‐composite of multiwall carbon nanotube, decorated with NiFe₂O₄ nanoparticles, was synthesized with citrate sol–gel method. The multiwall carbon nanotubes decorated with NiFe₂O₄ nanoparticles (NiFe₂O₄–MWCNTs) were characterized with different methods such as Fourier transform infrared spectroscopy (FT‐IR), transmission electron microscopy (TEM), atomic force microscopy (AFM), vibrating sample magnetometer (VSM), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The new nano-composite acts as a suitable electrocatalyst for the oxidation of sotalol at a potential of 500 mV at the surface of the modified electrode. Linear sweep voltammetry exhibited two wide linear dynamic ranges of 0.5–1000 μmol L^? 1 sotalol with a detection limit of 0.09 μmol L^? 1. The modified electrode was used as a novel electrochemical sensor for the determination of sotalol in real samples such as pharmaceutical, patient and safe human urine.     

Application of a europium complex,Eu(AA)3phen (AA = acrylic acid,phen = 1,10-phenanthroline) as a spectroscopic probe and cleaving reagent of DNA

A complex Eu(AA)₃phen was synthesized and characterized by elemental analysis, IR spectroscopy and ¹H NMR. Interaction between Eu(AA)₃phen and DNA was studied by UV/visible absorption spectroscopy, fluorescence spectrophotometer, circular-dichroism (CD) spectra and gel-electrophoresis measurements. Absorption spectral indicated that Eu(AA)₃phen binding to DNA was an electrostatic mode, which was authenticated by the effect of ionic strength, thermal denaturation and fluorescence quenching experiments. The intrinsic binding constant K_b of Eu(AA)₃phen was calculated to be 1.6 × 10⁴ L mol^? 1.     

Application of an exfoliated graphite nanoplatelet-modified electrode for the determination of quintozen

A chitosan–grafted exfoliated graphite nanoplatelet (xGnP) hybrid chemically modified electrode was developed and characterized for the determination of organochlorine pesticides with nitro groups using quintozen as a representative. The hybrid material was characterized by Fourier transform infrared spectroscopy (FTIR), ultraviolet–visible spectroscopy (UV–VIS) and scanning electron microscopy (SEM). The electrochemical properties of the chitosan–xGnP modified electrode were characterized by a physical deposition method for depositing it on a graphite electrode. Because of the affinity of the xGnP for nitro groups, nitroaromatic organophosphate pesticides are attached to the surface, allowing the extraction of quintozen within a short time (4 min). The differential pulse response was linear over the quintozen concentration range of 10^?12–10^?6 M, and the current linearly increased with the quintozen concentrations in two concentration ranges: from 10^?12 to 10^?8 M with the linear regression equation of y = 0.0423x + 0.6451, R² = 0.9964 and from 10^?8 to 10^?6 M with the linear regression equation of y = 0.0085x + 0.303, R² = 0.9952, with a detection limit of 10^?11 M.     

Gold nanoparticle/single-walled carbon nanotube film on the surface of glassy carbon electrode and its application

A sensor based on gold nanoparticle/single-walled carbon nanotube film on the surface of glassy carbon electrode is prepared. Electrochemical behavior of adrenaline hydrochloride (AH) on the surface of gold nanoparticle/single-walled carbon nanotube modified glassy carbon electrode is investigated. A simple, sensitive, and inexpensive method for determination of AH is proposed. The oxidation peak currents is proportional to adrenaline hydrochloride concentrations in the range of 0.20 mg L^? 1 to 1.80 mg L^? 1 in 0.1 M phosphate buffer solution of pH 7.3, the detection limit for AH is 0.06 mg L^? 1, and the recoveries are in the range from 100.0 to 110.0% with RSD of 1.2–1.9% (n = 6).     

Flux growth and thermal properties of LiBaB9O15 single crystal

A large LiBaB₉O₁₅ single crystal has been grown by the top-seeded solution growth (TSSG) method using a Li₂Mo₃O₁₀ flux system. The crystal obtained exhibits (1 1 0), (1 1 3) and (1 0 2) faces. For the first time, thermal properties of the as-grown crystal, including thermal expansion, specific heat and thermal conductivity, have been investigated as a function of temperature. The specific heat of the LiBaB₉O₁₅ crystal was measured to be 0.663–1.110 J g^?1 K^?1 over the temperature range of 20–400 °C. The crystal exhibits thermal expansion along the a- and b-axis, coupled with thermal contraction along the c-axis, over the measured temperature range of 25–500 °C. The average thermal expansion coefficients along the a- and c-axis of the LiBaB₉O₁₅ crystal from 25 to 500 °C are calculated to be α_a = 6.56 × 10^?6 K^?1 and α_c = ?4.82 × 10^?6 K^?1, respectively.     

Biopolymer-manganese oxide nanoflake nanocomposite films fabricated by electrostatic layer-by-layer assembly

Bio-nanocomposite films based on chitosan and manganese oxide nanoflake have been fabricated via the layer-by-layer (LBL) self-assembly technique. UV–vis absorption spectra showed that the subsequent growth of the nanocomposite film was regular and highly reproducible from layer to layer. X-ray photoelectron spectroscopy (XPS) spectra confirmed the incorporation of chitosan and manganese oxide nanoflake into the films. Scanning electron microscopy (SEM) images revealed that the nanocomposite film had a continuous surface and a layered structure. A sensitive hydrogen peroxide (H₂O₂) amperometric sensor was fabricated with the chitosan–manganese oxide nanoflake nanocompoite film. The sensor showed a rapid and linear response to H₂O₂ over the range from 2.5 × 10^? 6 to 1.05 × 10^? 3 M, with a sensitivity of 0.038 A M^? 1 cm^? 2.     

Fabrication and characterization of a zirconia/multi-walled carbon nanotube mesoporous composite

A zirconia/multi-walled carbon nanotube (ZrO₂/MWCNT) mesoporous composite was fabricated via a simple method using a hydrothermal process with the aid of the cationic surfactant cetyltrimethylammonium bromide (CTAB). Transmission electron microscopy (TEM), N₂ adsorption–desorption, Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) techniques were used to characterize the as-made samples. The cubic ZrO₂ nanocrystallites were observed to overlay the surface of MWCNTs, which resulted in the formation of a novel mesoporous–nanotube composite. On the basis of a TEM analysis of the products from controlled experiment, the role of the acid-treated MWCNTs and CTAB was proposed to explain the formation of the mesoporous–nanotube structure. The as-made composite possessed novel properties, such as a high surface area (312 m² · g^? 1) and a bimodal mesoporous structure (3.18 nm and 12.4 nm). It was concluded that this composite has important application value due to its one-dimensional hollow structure, excellent electric conductivity and large surface area.     

Nitrogen-doped hollow carbon spheres with enhanced electrochemical capacitive properties

Nitrogen-doped hollow carbon spheres (N-HCS) with uniform size have been synthesized via the hydrothermal method using pyrrole as the precursor. After carbonization at 850 °C, the average diameter of N-HCS is ca. 370 nm with shell thickness of ～15 nm. The electrochemical capacitive behavior of N-HCS was investigated by cyclic voltammetry and galvanostatic charge–discharge method in 1.0 M H₂SO₄ aqueous solution. Results show that N-HCS have high specific capacitance (345.2 F g^?1 at 0.2 A g^?1) and high-rate capability with the increase of the scan rate from 10 to 1000 mV s^?1 due to the synergetic effects of the unique hollow nanostructure and the N-doped thin carbon shell. In addition, the capacitance retains 98.1% after 1500 cycles even at a high loading current density of 10 A g^?1.     

Effect of carbon content and calcination temperature on the electrochemical performance of lithium iron phosphate/carbon composites as cathode materials for lithium-ion batteries

Lithium iron phosphate/carbon (LiFePO₄/C) composites were prepared by a convenient method with water-soluble phenol-formaldehyde resin as the carbon precursor. The morphology, crystalline structure, thermal stability, and composition of as-prepared LiFePO₄/C composites were investigated by scanning electron microscopy, X-ray diffraction, thermogravimetric analysis, and Raman spectrometry. Their electrochemical performance was examined based on cyclic voltammogram with a LAND battery testing system while the effect of carbon content and calcination temperature was highlighted. Results show that carbon content and calcination temperature dramatically influence the discharge capacities and rate performance of LiFePO₄/C composites. The optimal calcination temperature is 700 °C, and the optimal carbon content (mass fraction) is 8.7%. The LiFePO₄/C composite prepared under the optimal conditions exhibits an initial room temperature discharge capacity of 150.2 mA h g^?1 at a 0.2 C rate and a constant discharge capacity of about 105.7 mA h g^?1 at a 20.0 C rate after 50 cycles, showing promising potential as a novel cathode material for lithium ion batteries.     

Voltammetric sensor based on carbon paste electrode modified with molecular imprinted polymer for determination of sulfadiazine in milk and human serum

A new sensitive voltammetric sensor for determination of sulfadiazine is described. The developed sensor is based on carbon paste electrode modified with sulfadiazine imprinted polymer (MIP) as a recognition element. For comparison, a non-imprinted polymer (NIP) modified carbon paste electrode was prepared. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) methods were performed to study the binding event and electrochemical behavior of sulfadiazine at the modified carbon paste electrodes. The determination of sulfadiazine after its extraction onto the electrode surface was carried out by DPV at 0.92 V vs. Ag/AgCl owing to oxidation of sulfadiazine. Under the optimized operational conditions, the peak current obtained at the MIP modified carbon paste electrode was proportional to the sulfadiazine concentration within the range of 2.0 × 10^? 7–1.0 × 10^? 4 mol L^? 1 with a detection limit and sensitivity of 1.4 × 10^? 7 mol L^? 1 and 4.2 × 10⁵ μA L mol^? 1, respectively. The reproducibility of the developed sensor in terms of relative standard deviation was 2.6%. The sensor was successfully applied for determination of sulfadiazine in spiked cow milk and human serum samples with recovery values in the range of 96.7–100.9%.     

Determination of Pb2+ ions by a modified carbon paste electrode based on multi-walled carbon nanotubes (MWCNTs) and nanosilica

A novel carbon paste ion selective electrode for determination of trace amount of lead was prepared. Multi-walled carbon nanotubes (MWCNTs) and nanosilica were used for improvement of a lead carbon paste sensor response. MWCNTs have a good conductivity which helps the transduction of the signal in carbon paste electrode. The electrode composition of 20 wt% paraffin oil, 57% graphite powder, 15% ionophore (thiram), 5% MWCNTs, and 3% nanosilica showed the stable potential response to Pb²⁺ ions with the Nernstian slope of 29.8 (±0.2) mV decade^?1 over a wide linear concentration range of 10^?7–10^?2 mol L^?1. The electrode has fast response time, and long term stability (more than 2 months). The proposed electrode was used to determine the concentration of lead ions in waste water and black tea samples.