Addition Of Organic Surfactants Research Articles

Organic Surfactant Assisted Polypyrrole Materials as Effective Chemiresistive Gas Sensors for VOCs and Toxic Gas Detection

Surfactant assisted PPy materials are explored as efficient gas sensors for VOCs and toxic gases in the present work. Polypyrrole nanostructures were prepared by chemical oxidative polymerization using various sulfonic acids as surfactants between 0-5 °C. The effect of sulfonyl group on PPy was confirmed by FT-IR spectrum analysis. Doping of sulfonic acid has a strong effect on morphology of polymer blends which displayed the amorphous, globular, cauliflower, flakes and compact sheet like structures observed in the surface morphology. The conductivity of doped PPy observed to be dependent on the nature of dopant and its doping level. The electrical conductivity was observed to enhance by an order in magnitude on the addition of organic surfactants from 0.1 to 2.0 M. The pristine PPy shows high % response of 93% and 70% only for NH3 and Cl2 respectively. But different surfactant doped PPy were found to be highly sensitive for most of the VOCs and toxic gases which emerged as efficient sensor materials for fast response and recovery at the lowest level of 5 ppm.

Facile hydrothermal synthesis of ultrahigh-aspect-ratio V2O5 nanowires for high-performance supercapacitors

Ultrahigh-aspect-ratio V2O5 nanowires were successfully prepared using [VO(O2)2(OH2)]− as the starting material by a template-free hydrothermal route without the addition of organic surfactant or inorganic ions. The prepared samples were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer–Emmet–Teller (BET), cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD). The results revealed that the peroxovanadium (V) complexes can be easily transformed to V2O5 nanowires by this hydrothermal route. The uniform nanowires were with width about 50 nm and length about dozens of micron. The BET analysis showed the V2O5 nanowires had a high specific surface area of 25.6 m2 g−1. The synthesized V2O5 nanowires performed a high capacitance of 351 F g−1 when used as supercapacitor electrode in 1 mol L−1 LiNO3.

Fabrication and catalytic activity of ultra-long V2O5 nanowires on the thermal decomposition of ammonium perchlorate

Ultra-long V2O5 nanowires were successfully synthesized using peroxovanadium (V) complexes solution by a template-free hydrothermal method without the addition of organic surfactant or inorganic ions. The as-obtained products were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was found that the peroxovanadium (V) complexes can be easily transformed to V2O5 nanowires by this hydrothermal route. Furthermore, the catalytic properties of the as-prepared V2O5 nanowires on the thermal decomposition of ammonium perchlorate (AP) were evaluated by Thermo-Gravimetric Analysis and Differential Thermal Analysis (TGA/DTA), which showed the thermal decomposition temperatures of AP in the presence of 1, 3, 5 and 10wt% of V2O5 nanowires were reduced to 414, 390, 383 and 368°C (decreased by 42, 66, 73 and 88°C), respectively.

Vanadium Pentoxide Nanostructures: An Effective Control of Morphology and Crystal Structure in Hydrothermal Conditions

A systematic study was made of the synthesis of V2O5·nH2O nanostructures, whose morphologies, crystal structure, and amount of water molecules between the layered structures were regulated by strictly controlling the hydrothermal treatment variables. The synthesis involved a direct hydrothermal reaction between V2O5 and H2O2, without the addition of organic surfactant or inorganic ions. The experimental results indicate that high purity nanostructures can be obtained using this simple and clean synthetic route. On the basis of a study of hydrothermal treatment variables such as reaction temperature and time, X-ray diffraction (XRD) and scanning transmission electron microscopy (STEM) revealed that it was possible to obtain nanoribbons of the V2O5·nH2O monoclinic phase and nanowires or nanorods of the V2O5·nH2O orthorhombic phase. Thermal gravimetric analysis (TGA) shows also that the water content in the structure can be controlled at appropriate hydrothermal conditions. Concerning the oxidation state of the vanadium atoms of as-obtained samples, a mixed-valence state composed of V4+ and V5+ was observed in the V2O5·nH2O monoclinic phase, while the valence of the vanadium atoms was preferentially 5+ in the V2O5·nH2O orthorhombic phase. The X-ray absorption near-edge structure (XANES) results also indicated that the local structure of vanadium possessed a higher degree of symmetry in the V2O5·nH2O monoclinic phase.

Effect of polymeric surfactant on particulate structure in nickel-terpineol suspensions

Price of noble metals (e.g., platinum, palladium, etc.) has risen rapidly over the years, so using base metals (e.g., nickel) as the interconnection material for microelectronic hybrid thick-film components has received much attention recently [1–4]. Taking the fabrication of a multilayer ceramic capacitor as an example, a stabilized nickel (Ni) slurry with a high solids concentration and an appropriate colloidal rheology is necessary for the production of defect-free, internal electrode layers. By tailoring the interparticle potentials in the slurry [5], a stable ink with a desired particulate structure may be attainable. Sanchez-Herencia et al. [6] recently prepared aqueous Ni colloids, in which nickel powders of 27% volume were mixed uniformly with κ-carrageenan in water to form “flowable” suspensions. The Ni colloids were then transformed into compacts with a sufficient “green” strength before being subjected to sintering at elevated temperatures. Bhattacharya et al. [7] examined rheological behaviors of nickel laterite suspensions at various temperatures, concentrations, particle sizes, and pH values. When solids concentration of the laterite slurries reached 20 wt%, a Bingham plastic flow behavior was observed. The present authors [8, 9] also investigated rheological behaviors of Ni suspensions when different polymeric surfactants and liquid solvents were used in the suspension formulation. Minor addition of appropriate organic surfactant was found effective in reducing the suspension viscosity, hence leading to an increased maximum solids concentration allowable for powdered suspensions. Even though the addition of organic surfactant to the rheology of Ni slurries has been studied rather extensively [6–9], a report that addresses the change of suspension structure when the surfactant is introduced into the powdered mixtures is limited [8]. In this study, we intend to compare the structural change of a model Ni-terpineol suspension when a propylene glycol was used as a surfactant. Submicrometer Ni powders (210 H, Inco Co., USA) with particle size in a range of 0.2–0.5 μm, and a specific surface area 4–8 m2/g (vendor specification) were used as the raw material. The Ni particles were extensively agglomerated, as shown in Fig. 1, from the scanning electron microscopy (SEM, JSM-6335F, Jeol, Japan). A commercially available polymeric dispersant (KD-6, ICI Surfactant, USA) consisting of propylene glycol as its major composition was uniformly mixed with reagent-grade α-terpineol (90%, Aldrich Chemical Co., USA) before addition of the powders to form ink slurries. All the powdered slurries were ball-mixed in polyethylene bottles for a period of 24 hr before their viscosity (ηs) being determined by a strain-controlled concentric viscometer (VT550, Gebruder HAAKE Gmbh, Germany) equipped with a sensor system (MV-DIN 53019, HAAKE, Germany) of a cone-cup geometry operated at a constant temperature (25 ◦C). The viscosity measurement was performed with a steady increment of shear rate (γ ) over a range of 1–1000 s−1. An SEM observation revealed that the Ni particles remained almost spherical in shape after the high-shear ball mixing. This indicated that the impact force involved in the mixing process did not deform the powders into flake forms that might substantially hinder the flow behavior of the suspensions. The suspensions all showed a shear-thinning flow character over the shear-rate range examined. This indicated that the suspensions were flocculated in structure and the Ni aggregates remained existing in the carrier liquid, even with the addition of propylene glycol. The extent of the powder aggregation appeared to be dependent on the shear rate applied, namely, the floc reduced in size as the shear rate increased, as revealed from the shear-thinning flow behavior of the suspensions. Yield stress (τy) of the suspensions can be estimated from the Casson model [10]: