Determination of ganciclovir as an antiviral drug and its interaction with DNA at Fe3O4/carboxylated multi-walled carbon nanotubes modified glassy carbon electrode

The electrochemical oxidation of an antiviral drug, ganciclovir (GCV) at Fe₃O₄/carboxylated multi-walled carbon nanotubes modified glassy carbon electrode (Fe₃O₄/cMWCNTs/GCE) was studied by voltammetric techniques. The influence of the effective parameters on the electrochemical behavior of GCV was investigated. Under optimized conditions, the proposed sensor was applied for low level GCV determination. The relationship between peak current and the concentration of GCV was linear in the range of 80–53,000 nM with a detection limit of 20 nM through square wave voltammetry (SWV). The interaction of GCV with calf thymus DNA was also explored by voltammetric and spectrofluorometric methods. Based on the obtained data the mode of binding of GCV to DNA was intercalative binding. The decrease in the SWV peak current of GCV in the presence of DNA was used for the determination of DNA. The modified electrode exhibited a good sensitivity, stability and pleasant reproducibility, and it was applied for the determination of GCV in spiked serum and urine, with satisfactory results.     

The influence of added carbon nanotubes on the properties of the carbon‐fiber‐reinforced paper‐based wet clutch friction materials

Different carbon nanotubes (CNT) content was used to investigate the influence on physical properties, microstructure, tribological behaviour and thermal endurance properties of the materials. Experimental results show that the bulk density of the specimens increase with the increase of the CNT content, and the open porosity of the samples gradually reduced, whereas the CNT content increases. When comparing the tribological properties of the specimens with different CNT content, specimens that contain 4 wt.% carbon nanotubes show the highest dynamic friction coefficient and the lowest variation coefficient of the dynamic friction coefficient. Moreover, the specimens exhibit more thermal stability and lower weight loss after adding the CNT. Copyright © 2015 John Wiley & Sons, Ltd.     

Antiwear,Antifriction, and Extreme Pressure Properties of Motor Bike Engine Oil Dispersed with Molybdenum Disulfide Nanoparticles

This work presents studies on the antiwear, antifriction, and extreme pressure properties of motor oil dispersed with MoS₂ nanoparticles. Commercial oil (SAE 20W-40 grade) is dispersed with stabilized MoS₂ nanoparticles in 0.25, 0.5, 0.75, and 1 wt%. The test oils are tested for antiwear, antifriction, and extreme pressure properties on a four-ball wear tester. The wear and friction offered by nanolubricants has decreased remarkably compared to the commercial base oil. The weld load and load wear index of oils dispersed with nanoparticles were improved substantially compared to the commercial base oil. Metallographic studies conducted on the wear balls from the extreme pressure test show that nanoparticles are deposited on the worn area along with additives in the oil, thereby preventing welding of the surfaces. An optimum weight fraction is arrived at for best performance. A synergy between the additives in the oil and dispersed nanoparticles has been observed, resulting in less dispersion for best results. It is found that beyond an optimum weight percentage of nanoparticles, the trends tend to reverse, resulting in greater wear and friction.     

A study on mechanical and tribological properties of silicone rubber reinforced with white carbon black

This paper analysed the effect of different white carbon black (fumed silica and precipitated silica) on the mechanics and friction property of silicone rubber. The tensile strength, tearing strength, elongation rate and shore hardness of silicone rubber reinforced with different kinds or dosages of white carbon black were investigated in detail. The wear morphology, worn surface analysis and chemical compositions of the rubber sample after the friction test were analysed by means of scanning electron microscopy, three-dimensional profile metre and energy dispersive spectrometer, respectively. Results showed that the mechanics properties of silicone rubber were obviously enhanced with the increase in white carbon black content. Moreover, after the friction test, the vulcanised rubber reinforced with fumed silica has less wear surface protrusions and grinding than that of precipitated silica. The wear rubber filled with fumed silica surface is quite smooth and shows few furrows and grooves, which well corresponds to good anti-wear ability of the reinforcing fillers. In the course of practical application, it is necessary to take into account of the mechanical properties, wear resistance of rubber and the adding amount of filler to achieve the optimum coordination for the best mechanical and friction properties of silicone rubber.     

A study of the thermal,dynamic mechanical,and tribological properties of polyphenylene sulfide composites reinforced with carbon nanofibers

The thermal, dynamic mechanical, and tribological properties of polyphenylene sulfide (PPS) composites reinforced with carbon nanofiber (CNF) were studied. Dynamic mechanical thermal analysis (DMTA) and differential scanning calorimetry (DSC) were used to study the viscoelastic properties and thermal transitions. In order to study the tribological properties, friction and wear tests in a pin-on-disk configuration were performed. The changes in melting point, crystallization temperature, and glass transition temperature were found to be small as a result of reinforcement. Steady state wear rates of the reinforced composites sliding against the counterface of roughness 0.13–0.15 μm Ra were significantly lower than that of the unreinforced PPS. When the composites were tested against the smoother counterface of 0.06–0.11 μm Ra, the wear rates were higher. The coefficient of friction in all the cases was not practically affected by the presence of CNF. The transfer films formed on the counterface during sliding were examined by optical microscopy and atomic force microscopy (AFM). The variation of wear is discussed in terms of the texture and topography of transfer film.