Using deep eutectic solvents to electrodeposit CoSm films and nanowires

A Deep Eutectic Solvent of 1 chlorine chloride: 2 urea eutectic mixture at 70 °C has been tested as useful to electrodeposit both magnetic SmCo films and nanowires. Galvanostatic deposition allows obtaining homogeneous deposits over metallic substrate with variable composition as a function of the current density applied. The deposits obtained at 0.5–1.5 mA cm^? 2 were uniform and they correspond to a cobalt hexagonal crystalline phase with magnetic anisotropy and coercivity of 250 Oe. It has been possible to deposit SmCo nanowires from the DES solvent using alumina templates. Uniform CoSm nanowires of 50 nm of diameter have been obtained; they correspond also to hexagonal phase, but they present higher coercivity.     

Development of an instrumented and automated single mode cavity for ceramic microwave sintering: Application to an alpha pure alumina powder

This paper describes the development of an instrumented and automated single mode microwave cavity for sintering ceramic powders. This setup includes an optical dilatometer and a motorized plunger to control heating cycles in a wide range of heating rates (from 5 °C ∙ min^− 1 to 200 °C ∙ min^− 1) up to 1600 °C and to allow reliable comparison with conventional sintering. The cavity and the sintering cells for both hybrid and direct microwave sintering were designed using finite element simulation. For accurate temperature measurement, an optical pyrometer calibrated with a specific protocol has been used. Microwave sintering of fine grained (< 100 nm) alpha alumina compacts was thus investigated and compared to conventional sintering. This pure alumina powder has been sintered by direct microwave heating, without any susceptor nor doping element to initiate heating as often achieved in the literature. The comparison of the densification kinetics along an identical thermal cycle evidenced a significant enhancement of sintering under microwaves during the first and intermediate stages.     

UV resistibility of a nano-ZnO/glass fibre reinforced epoxy composite

The harmfulness of ultraviolet (UV) radiation (UVR) to human health and polymer degradation has been the focus recently in all engineering industries. A polymer-based composite filled with nano-ZnO particles can enhance its UV resistibility. It has been found that the use of appropriate amount of nano-ZnO/Isopropyl alcohol solvent to prepare a UV resistant nano-ZnO/glass fibre reinforced epoxy (ZGFRE) composite can effectively block the UV transmission with negligible influence on the crystal structure of its resin system. This paper aims at investigating the interfacial bonding behaviour and UV resistibility of a ZGFRE composite. The solvent effect in relation to the dispersion properties of ZnO in the composite is also discussed. XRD results indicated that 20 wt% Isopropyl alcohol was an effective solvent for filling nano-ZnO particles into an epoxy. SEM examination also showed that the bonding behaviour between glass fibre and matrix was enhanced after filling 20 wt% nano-ZnO particles with 20 wt% Isopropyl alcohol into the composite. Samples filled with 20 wt% nano-ZnO/Isopropyl alcohol and 40 wt% nano-ZnO/Isopropyl alcohol has full absorption of UVA (315–400 nm), UVB (280–315 nm) and a part of UVC (190–280 nm).     

Synthesis of mesoporous Al2O3 macrospheres using the biopolymer chitosan as a template: A novel active catalyst system for CO2 reforming of methane

A new and simple method to prepare alumina containing mainly mesopores is described. This alumina has a high surface area (464 m²/g) and a large pore volume ranging from about 0.35 to 0.65 cm³/g. The present method was developed using a biopolymer (chitosan) and Al solution. The Al–chitosan solution was added to NH₄OH solution in the form of drops. A hybrid macrosphere compound of aluminum hydroxide and organic polymer is formed. Through polymer elimination by thermal treatment, porous Al₂O₃ spheres with a high specific surface area are obtained. The Ni-impregnated Al₂O₃ spheres showed a high catalytic activity and stability for dry reforming of methane at 650 °C and a CH₄ / CO₂ = 1 molar ratio.     

Amperometric biosensor for ethanol detection based on alcohol oxidase immobilised within electrochemically deposited Resydrol film

A new biosensor based on amperometric transducer and alcohol oxidase immobilised in Resydrol polymer for ethanol detection has been developed. The optimal composition and immobilisation conditions for creating active membrane based on alcohol oxidase have been determined. Electrochemical deposition of the polymer film has been achieved by applying the potentiostatic pulse profile consisting of 20 consecutive pulses of + 1900 mV for 0.3 s and − 300 mV for 5 s. The biosensors developed show good analytical characteristics such as reproducibility, operational and storage stability. The minimal detection limit was 3.5 × 10^− 2 (% v/v) of ethanol. The biosensor developed has been shown to be a potential for ethanol detection in real alcoholic beverages.     

Modification of chloromethylated polystyrene with 2-mercabtobenzothiazole for application as a new sorbent for preconcentration and determination of Ag+ from different matrices

Chloromethylated polystyrene polymer (CMSP) modified with 2-mercabtobenzothiazole (MBT) has been developed for the selective separation and/or preconcentration of silver. The modified polymer (CMS-MBT) was characterized by elemental analysis and IR spectra. Batch and column modes were applied. The newly designed polymer quantitatively sorbed Ag⁺ at pH 2 when the flow rate is 5 ml min^?1. The maximum sorption capacity was 0.493 mmol g^?1 while the preconcentration factor was 250 for Ag⁺. The detection limit was 8 ng ml^?1. The desorption was effective with 5 ml of 2 mol l^?1 HNO₃ prior to detection using AAS. The modified polymer was highly ion-selective in nature even in the presence of large concentrations of electrolytes or organic media, with a preconcentrating ability for Ag⁺. The utility of the modified polymer to synthetic and drugs samples showed RSD values of <3% reflecting its accuracy and reproducibility.     

Preparation and thermomechanical properties of Ag-PVA nanocomposite films

Metal–polymer hybrid nanocomposites have been prepared from an aqueous solution of polyvinyl alcohol (PVA) and silver nitrate (AgNO₃). The silver nanoparticles were generated in PVA matrix by the reduction of silver ions with PVA molecule at 60–70 °C over magnetic stirrer. UV–vis analysis, X-ray diffraction studies, transmission electron microscopy, scanning electron microscopy and current–voltage analysis were used to characterize the nanocomposite films prepared. The X-ray diffraction analysis reveals that silver metal is present in face centered cubic (fcc) crystal structure. Average crystallite size of silver nanocrystal is 19 nm, which increases to 22 nm on annealing the film at 150 °C in air. This result is in good agreement with the result obtained from TEM. The UV–vis spectrum shows a single peak at 433 nm, arising from the surface plasmon absorption of silver nanocolloids. This result clearly indicates that silver nanoparticles are embedded in PVA. An improvement of mechanical properties (storage modulus) was also noticed due to a modification of PVA up to 0.5 wt% of silver content. The current–voltage (I–V) characteristic of nanocomposite films shows increase in current drawn with increasing Ag-content in the films.     

Synthesis and luminescence of a new phosphorescent iridium(III) pyrazine complex

The synthesis and luminescent study of a new iridium pyrazine complex are reported. The iridium complex [Ir(MDPP)2(acac)] (MDPP=5-methyl-2,3-diphenylpyrazine, acac=acetylacetone) shows strong ¹MLCT (singlet metal-to-ligand charge-transfer) and ³MLCT (triplet metal to ligand charge-transfer) absorption at 386 and 507 nm, respectively. Organic light emitting device (OLED) with a configuration of ITO / NPB (30 nm) / NPB: 7% (wt.) Ir(MDPP)₂(acac) (25 nm) / BCP (10 nm) / Alq₃(30 nm) / Mg : Ag (mass ratio 10 : 1)120 nm / Ag(10 nm) exhibits an external quantum efficiency of 6.02% (power efficiency 9.89 lm W^− 1 ) and a maximum brightness of 78,924 cd m^− 2. The device also shows high color purity with a maximum peak at 576 nm without any shoulder.     

Synthesis of conducting ferromagnetic nanocomposite with improved microwave absorption properties

The present paper reports the synthesis of polyaromatic amine–ferromagnetic composite with nanosize TiO₂ (～70–90 nm) and γ-Fe₂O₃ (～10–15 nm) particles via in situ emulsion polymerization. Magnetic and conductivity studies demonstrate that the conducting ferromagnetic composite possesses saturation magnetization (M_S) value of 26.9 emu g^?1 and conductivity of the order of 0.46 S cm^?1, which are measured by vibrating sample magnetometer and four-probe technique, respectively. It is observed that the presence of the nanosized γ-Fe₂O₃ in the polyaniline–TiO₂ matrix affects the electromagnetic shielding property of the composite. Polyaniline–TiO₂–γ-Fe₂O₃ nanocomposite has shown better shielding effectiveness due to absorption (SE_A ～ 45 dB) than the polyaniline-γ-Fe₂O₃ (SE_A ～ 8.8 dB) and polyaniline–TiO₂ (SE_A ～ 22.4 dB) nanocomposite. The polymer composites were further characterized by high resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) technique.     

Synthesis of nanoporous silicon carbide via the preceramic polymer route

Nanoporous silicon carbide materials were prepared by the pyrolysis of the preceramic polymer, polycarbosilane (PCS), with and without the addition of an inert filler (nano- and micron-sized silicon carbide powders). Hydrosilylation crosslinking of PCS with divinylbenzene prior to pyrolysis appeared to have little influence on the development of micro- and mesoporosity. Maximum micropore volumes were 0.28 cm³ g^?1 for non-crosslinked PCS and 0.25, 0.33 and 0.32 cm³ g^?1 for PCS crosslinked with 2, 6 and 10 wt.% DVB respectively. Micropore volumes decreased under hydrothermal conditions to 0.03 cm³ g^?1 for non-crosslinked and 0 cm³ g^?1 for crosslinked PCS. Porosity was also lost at temperatures above 700 °C. The addition of nano-sized SiC powders to PCS prior to pyrolysis maintained mesoporosity to temperatures of 1200 °C, however, micron-sized SiC powders did not maintain porosity above 800 °C. The modal pore size in pellets formed by compressing micron-sized powders with the preceramic polymer was 5 μm compared to 30 nm when nano-sized powders were used.     

The synthesis and characterization of a novel biodegradable and electroactive polyphosphazene for nerve regeneration

Conductive polymers have been of great interest to the biopharmaceutical industry because of their cell adhesion and proliferation. In this paper, a novel electrically-conductive and biodegradable polyphosphazene polymer containing parent aniline pentamer (PAP) and glycine ethyl ester (GEE) as side chains was synthesized through a nucleophilic substitution reaction for its potential application in nerve regeneration. The electrical conductivity of the polymer was ~ 2 × 10^? 5 S/cm in the semiconducting region upon preliminarily protonic-doped experiment. Degradation studies carried out in phosphate-buffered saline at 37 °C showed a mass loss of ~ 50% after 70 days. In vitro cytotoxicity to the RSC96 Schwann cells was evaluated using the cell viability assay. The polymer exhibited no cytotoxicity, indicating that such a polyphosphazene polymer has potential as scaffold material in tissue engineering for peripheral nerve regeneration or other biomedical devices that require electroactivity.     

Preparation of novel carbon microfiber/carbon nanofiber-dispersed polyvinyl alcohol-based nanocomposite material for lithium-ion electrolyte battery separator

A novel nanocomposite polyvinyl alcohol precursor-based material dispersed with the web of carbon microfibers and carbon nanofibers is developed as lithium (Li)-ion electrolyte battery separator. The primary synthesis steps of the separator material consist of esterification of polyvinyl acetate to produce polyvinyl alcohol gel, ball-milling of the surfactant dispersed carbon micro-nanofibers, mixing of the milled micron size (~ 500 nm) fibers to the reactant mixture at the incipience of the polyvinyl alcohol gel formation, and the mixing of hydrophobic reagents along with polyethylene glycol as a plasticizer, to produce a thin film of ~ 25 μm. The produced film, uniformly dispersed with carbon micro-nanofibers, has dramatically improved performance as a battery separator, with the ion conductivity of the electrolytes (LiPF₆) saturated film measured as 0.119 S-cm^? 1, approximately two orders of magnitude higher than that of polyvinyl alcohol. The other primary characteristics of the produced film, such as tensile strength, contact angle, and thermal stability, are also found to be superior to the materials made of other precursors, including polypropylene and polyethylene, discussed in the literature. The method of producing the films in this study is novel, simple, environmentally benign, and economically viable.     

The effect of polymeric wall on the permeability of drug-loaded nanocapsules

The aim of this work was to establish a quantitative correlation between the drug permeability and the polymer concentration in the nanocapsules. Indomethacin ethyl ester-loaded nanoemulsion and nanocapsules containing poly(epsilon-caprolactone) at different concentrations (0, 2, 4, 6, 8 and 10 mg/mL) presented drug loading between 0.981 and 1.005 mg/mL, pH values from 5.0 to 5.4, particle sizes between 232 and 261 nm, polydispersity lower than 0.24 and zeta potentials from − 8.54 mV to − 11.86 mV. An alkaline hydrolysis of indomethacin ethyl ester carried out at the particle/water interface was used to simulate a sink condition of release. The number of particles in each suspension was estimated. The calculated values ranged from 5.84 × 10¹² to 6.60 × 10¹² particles cm^− 3, showing similar concentration of particles in the formulations. The diffusion was proposed as the main mechanism of the indomethacin ester release after fitting the data to the Higuchi model. Applying the Fick's first law, the calculated indomethacin ester fluxes (J) decreased from 2.20 × 10^− 7 to 1.43 × 10^− 7 mg cm^− 2 min^− 1. Then, the drug relative permeability decreased according to the increase in the polymer concentration fitting a power law.     

Structural and pyroelectric properties of sol–gel derived multiferroic BFO thin films

Multiferroic BFO/PZT multilayer films were fabricated by spin-coating method on the (1 1 1)Pt/Ti/SiO₂/Si substrate alternately using PZT(30/70), PZT(70/30) and BFO alkoxide solutions. The structural and ferroelectric properties were investigated for uncooled infrared detector applications. The coating and heating procedure was repeated six times to form BFO/PZT multilayer films. All films showed the typical XRD patterns of the perovskite polycrystalline structure without presence of the second phase such as Bi₂Fe₄O₃. The thickness of BFO/PZT multilayer film was about 200–220 nm. The ferroelectric properties such as dielectric constant, remnant polarization and pyroelectric coefficient were superior to those of single composition BFO film, and those values for BFO/PZT(70/30) multilayer film were 288, 15.7 μC/cm² and 9.1 × 10^?9 C/cm² K at room temperature, respectively. Leakage current density of the BFO/PZT(30/70) multilayer film was 3.3 × 10^?9 A/cm² at 150 kV/cm. The figures of merit, F_V for the voltage responsivity and F_D for the specific detectivity, of the BFO/PZT(70/30) multilayer film were 6.17 × 10^?11 Ccm/J and 6.45 × 10^?9 Ccm/J, respectively.     

Plasticized alkaline solid polymer electrolyte system

Alkaline solid polymer electrolytes were prepared by utilizing poly(vinyl alcohol) (PVA), potassium hydroxide (KOH), α-Al₂O₃ and different amounts of propylene carbonate (PC). The addition of PC to the PVA:KOH:α-Al₂O₃:H₂O increased its conductivity by three orders of magnitude to the reading of ∼ 10^− 4 S cm^− 1. The plot for log σ − 1 / T showed a transformation from liquid-like conductivity to Arrhenius type. The dielectric constant (ε_r) of the samples increases with increasing PC concentrations and temperatures. Scanning electron microscopy also shows the effect of PC on the polymer electrolytes surface. Thermogravimetric studies show that the thermal stability of the polymer electrolytes decreases with the addition of PC.     

Synthesis and characterization of spherical polymer brushes

The synthesis of spherical polymer brushes consisting of a nano-SiO₂ core modified by γ-methacryloxypropyl trimethoxy-silane and a shell of linear polyacrylamide by grafting polymerization was described. The spherical polymer brushes were characterized by Transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and Thermo-gravimetric analysis (TGA). After cleavage of the ester group that connected the polymers to the surface, the molecular weight of the brushes was determined by Gel Permeation Chromatography (GPC). The results showed that the average diameter of spherical polymer brushes was ca. 140 nm while weight average molecular weight and surface grafting density were 1.407 × 10³ g/mol and 1.016 × 10^?4 mol/g respectively.     

Room-temperature photoluminescence from porous anodic alumina films with embedded terbium and europium species

Strong room-temperature terbium and europium photoluminescence, with well-resolved optical bands corresponding to electron transitions ⁵D₄→⁷F_j (j = 3–6) for Tb³⁺, and ⁵D₀→⁷F_j (j = 1–4) for Eu³⁺, was observed from porous anodic alumina films of 5–55 µm thickness after immersion in solutions of terbium or europium nitrates and subsequent heat treatment. GDOES and TEM examinations of the specimens treated with terbium ions revealed a uniform distribution of terbium across the porous anodic film thickness of 55 µm, with an increased terbium concentration toward the pore bases. Europium- and terbium-doped specimens displayed anisotropic indicatrix of luminescence for the emission wavelength of 613 nm for europium and 545 nm for terbium, with a maximum intensity in the direction along the channels of the pores that is typical for porous anodic alumina with lanthanide ions within the pores. The potential applications of porous anodic alumina doped with lanthanides through immersion in the absence of xerogel are discussed.     

Lithium storage capability of CuGeO3 nanorods

Copper metagermanate (CuGeO₃) nanorods were synthesized through a low temperature hydrothermal method at 180 °C. The as-synthesized CuGeO₃ nanorods show a well crystallined nanostructure with diameters in the range from 40 to 70 nm, and a length from 250 to 350 nm. Electrochemical measurements demonstrate that the CuGeO₃ nanorods exhibit a first charge capacity of 924 mAh g^?1 and 690 mAh g^?1 after 50 cycles, which is remarkably improved than the pure nanosize GeO₂ electrode. This investigation indicates that CuGeO₃ nanorods could be utilized as a high capacity anode material in lithium-ion batteries by reducing particle size and metal oxide addition. The lithium storage mechanisms for the improved capacity retention were also studied.     

Effect of solvent ratio on the properties of highly oriented sprayed fluorine-doped tin oxide thin films

Transparent conducting thin films of F:SnO₂ have been deposited onto preheated glass substrates by a spray pyrolysis technique using pentahydrate stannic chloride (SnCl₄·5H₂O) and ammonium fluoride (NH₄F) as precursors and mixture of water and propane-2-ol as solvent. The concentration of SnCl₄·5H₂O and NH₄F is kept fixed and the ratio of water and propane-2-ol solvent in the spraying solution is varied. A fine spray of the source solution using air as a carrier gas has grown films of thickness up to 995 nm. Optical absorption, X-ray diffraction, Van der Pauw technique for measurement of a sheet resistance and Hall effect measurements at room temperature for determination of carrier density and conductivity have been used. The as-deposited films are of polycrystalline SnO₂ with a tetragonal crystal structure and are preferentially having orientation along the (200) direction with texture coefficient as high as 6.16. The average grain size for the as-deposited sample is found to be of the order of 44 nm. The films have moderate optical transmission (up to 70–85% at 550 nm). The figure of merit (ϕ) values vary from 1.95 · 10^− 3 to 35.68 · 10^− 3 Ω^− 1. The films are heavily doped, degenerate and exhibit n-type electrical conductivity. The lowest sheet resistance (R_s) for the optimized sample is 5.1 Ω. The films have a resistivity of 5.43 · 10^− 4 Ω cm and mobility around 7.38 cm² V^− 1 s^− 1.     

Fine-tuning the photoluminescence and photocatalytic properties of CdS nanorods of varying dimensions

CdS nanorods having different aspect ratio viz., 17 (length ∼170 nm and width ∼10 nm) and 28 (length ∼140 nm and width ∼5 nm) has been synthesized by solvothermal technique at different time intervals (2–10 h). The effect of aspect ratio, crystallinity, band gap energy, surface area and Au/Ag loading on the various photoactive properties of these CdS nanostructures are discussed here. The photocatalytic activity for salicylic acid oxidation under UV irradiation is gradually improved with the increasing crystallinity of CdS nanostructures, length (140 < 170 nm), exposed area (2358 < 5722 nm²) per particle and decreasing surface area (158 < 122 < 76 m²g⁻¹), surface to volume ratio (0.82 < 0.41 nm⁻¹) and aspect ratio (28 < 17). The deposition of 1–2 wt% Au (∼3.5 nm) and Ag (∼1.8 nm) nanoparticles onto CdS drastically quenched the emission and enhanced the photocatalytic activity.