Studies of physical and chemical properties of styrene-based plasma polymer films deposited by radiofrequency Ar/styrene glow discharge

Styrene-based plasma polymer (SPP) films having thickness in the range of 900–1800 nm are deposited from radiofrequency (RF) Ar/styrene glow discharge. Depositions of the SPP films are carried out at working pressure of 1.2 × 10^?1 mbar and in the RF power range of 40–130 W. The physical and chemical properties of the SPP films are investigated as a function of RF power. Optical emission spectroscopy (OES) studies on Ar/styrene glow discharge reveal that the relative concentrations of active plasma species are strongly dependent on the variation of RF power. Fourier transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS) are used to analyze the internal chemical structures of the films. It is revealed that the SPP film with highest carbon content exhibits enhanced scratch and corrosion resistance behavior along with stable thermal properties. The thermogravimetric (TGA) and gel permeation chromatography (GPC) results suggest the presence of both aliphatic and aromatic units in the SPP films. Attempts are made to correlate the results obtained from OES, FT-IR and XPS analyses with the deposited films properties. The possibility of using SPP films as protective coatings is also explored.     

Systematic study of interfacial interactions between clays and an ionomer

To study the interfacial interactions between an ionomer [poly(ethylene‐co‐acrylic acid) neutralized by zinc salts (PI)] and clays, PI–clay nanocomposites were prepared using a solution method. Two types of commercially available montmorillonite clays respectively K10 and KSF were used, and were modified with organic modifiers with chain lengths of 12–18 carbons. The interactions between the PI, clays, and modifiers were evaluated through study of the structure, morphology, and properties of the PI–clay nanocomposites. We found that the modifiers were successfully intercalated into the clay layers (Fourier transform infrared spectroscopy). The clay modified with a long‐chain agent showed an exfoliated nature in the nanocomposite. The thermal stability and storage modulus of PI were improved greatly by the addition of the clays, especially when the long‐chain modifier was used (thermogravimetric analysis and dynamic mechanical analysis). The differential scanning calorimetry results show that clay layers are inserted into the clusters because of solvent‐directed morphological evolution, so the transition of the ionic domains and the crystallinity of PI are changed. The interaction between PI, the modifier, and the silicate layer played an important role in the determination of the properties of the nanocomposites. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Biomimetic protein‐based elastomeric hydrogels for biomedical applications

In recent years, protein‐based elastomeric hydrogels have gained increased research interest in biomedical applications for their remarkable self‐assembly behaviour, tunable 3D porous structure, high resilience (elasticity), fatigue lifetime (durability), water uptake, excellent biocompatibility and biological activity. The proteins and polypeptides can be derived naturally (animal or insect sources) or by recombinant (bacterial expression) routes and can be crosslinked via physical or chemical approaches to obtain elastomeric hydrogels. Here we review and present the recent accomplishments in the synthesis, fabrication and biomedical applications of protein‐based elastomeric hydrogels such as elastin, resilin, flagelliform spider silk and their derivatives. © 2013 Society of Chemical Industry     

The eventuality of diffusiophoresis and chemical reaction in a flow with variable fluid properties through an upright channel

The quintessence of this article encompasses the effect of diffusiophoresis, chemical reaction, and varying viscosity as well as thermal conductivity on a fully developed dissipative flow through an upright channel. The fluid is electrically conducting undergoing mixed convection. The governing equations, after transfiguring into dimensionless formation, are solved through a numerical procedure for boundary value problems incorporating MATLAB solver. Imperative scrutiny is made to visualize associative impacts of flow parameters, namely, magnetic parameter, the Brinkmann number, the Schmidt number, variable viscosity parameter, variable thermal conductivity parameter, chemical reaction parameter, diffusiophoretic parameter, and particle diffusion parameter, on the flow. The velocity field, the temperature field, the solute concentration field, the particle concentration field, the skin friction, the Nusselt number, the Sherwood number, and the particle concentration gradient are assessed in view of alteration of the aforesaid parameters with the help of visual illustrations in graphical form and tabular form. Solute mass transposition and colloidal particle locomotion are the fresh inclusions to the scrutiny of upright channel flow in light of solving scheme of bvp4c. Chemical reaction engulfs both solute and particle concentration. Growing viscosity hinders the fluid velocity and heats up the flow encouraging interlayer friction.     

MoS2-Polyaniline Based Flexible Electrochemical Biosensor: Toward pH Monitoring in Human Sweat

Wearable pH sensors for sweat analysis have garnered significant scientific attention for the detection of early signs of many physiological diseases. In this study, a MoS₂-polyaniline (PANI) modified screen-printed carbon electrode (SPCE) is fabricated and used as a sweat biosensor. The exfoliated MoS₂ nanosheets are drop casted over an SPCE and are functionalized by a conducting polymer, polyaniline (PANI) via the electropolymerization technique. The as-fabricated biosensor exhibits high super-Nernstian sensitivity of −70.4 ± 1.7 mV pH⁻¹ in the linear range of pH 4 to 8 of 0.1 m standard phosphate buffer solution (PBS), with outstanding reproducibility. The sensor exhibits excellent selectivity against the common sweat ions including Na⁺, Cl⁻, K⁺, and NH₄⁺ with tremendous long-term stability over 180 min from pH 4 to 6. The enhanced active surface area and better electrical conductivity as a consequence of the synergistic effect between MoS₂ and PANI are correlated with the boosted performance of the as-produced biosensor. The feasibility of the sensor is further examined using an artificial sweat specimen and the successful detection confirms the potential of the biosensor for a real-time noninvasive, skin attachable, and flexible wearable pH sensor.     

Synthesis of n-HAP using different precursors and dependence of Vickers hardness on the structure by tuning sintering temperature

Three sets of starting materials Ca(NO₃)₂·4H₂O and (NH₄)₂HPO₄; Ca(OH)₂ and H₃PO₄; Ca(OH)₂ and (NH₄)₂HPO₄ were chosen for the preparation of different precursors of hydroxyapatite nanoparticles (n-HAP) by wet chemical precipitation technique denoted by HAP-1, HAP-2, HAP-3. X-ray diffraction (XRD) studies show that n-HAP of all three types exhibited single-phase in the as-prepared condition. Transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and selected area electron diffraction (SAED) studies of as-prepared samples showed characteristic needle-like particles with a width of 5 nm, which were fully crystalline exhibited by the lattice fringe in HRTEM, and single-phase demonstrated by SAED patterns. The samples were pelletized and annealed at varying temperatures in the range of 600°C–1400°C. The results indicated that HAP-1 and HAP-3 samples showed phase decomposition at 1400°C to form β-tricalcium phosphate (β-TCP) while for HAP-2 no such decomposition occurred up to 1400°C. Data from the Vickers hardness test revealed that the hardness value up to 2.5 GPa was attained at the sintering temperature of 1200°C for HAP-1 and HAP-3. The hardness values are consistently higher for HAP-2 than HAP-1 and HAP-3 at all sintering temperatures and attained a value of 3 GPa at 1200°C. Thus, synthesizing n-HAP by using H₃PO₄; Ca(OH)₂ bestows highest Vickers hardness.