Tapan Dash

Water disinfection through photoactive modified titania.

TiO(2), N-TiO(2) and S-TiO(2) samples have been prepared by various chemical methods. These samples were characterized by X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS), Laser Raman spectrometer, UV-Visible spectrophotometer, field emission scanning electron microscope (FE-SEM) and transmission electron microscope (TEM). X-ray powder diffraction study reveals that all three samples are single anatase phase of titania and the crystallinity of titania decreases with sulphur doping whereas nitrogen doping does not affect it. UV-Visible (diffuse) reflectance spectra shows that doping of titania with nitrogen and sulphur shift the absorption edge of titania from ultraviolet to visible region. XPS study confirms that both nitrogen and sulphur are well doped in the titania lattice. It is observed that nitrogen occupies at both substitutional and interstitial position in the lattice of titania. FE-SEM and TEM studies demonstrate that the particles are below 50nm range. It is found that S and N doping of titania increased its water disinfection property in the order TiO(2)

Shear-force-dominated dual-drive planetary ball milling for the scalable production of graphene and its electrocatalytic application with Pd nanostructures

The exceptional properties of graphene-based derivatives have governed numerous research fields in recent years. The scaled up and reliable production of high-quality graphene is still a challenging task. This work presents an efficient and low-cost approach for the mass production of high-quality graphene (50 g scale batch) through the dual-drive planetary ball milling of graphite with a dicarboxylic acid. The dimensional changes of graphite were determined from the diffraction pattern of the (002) plane at different milling times and the unique signature of graphene noticed in the Raman spectra. Transmission electron microscopy clearly revealed the existence of single and bilayer graphene sheets. Non-destructive exfoliation was evidenced by the surface binding states of the C 1s core level spectra. The as-synthesized graphene was utilized as the catalytic support for formic acid fuel cell applications. Graphene supported palladium nanocomposites were prepared, and the electrocatalytic activity towards formic acid oxidation was explored. The cyclic voltammogram of the graphene–palladium nanocomposite reveals that the onset potential for formic acid oxidation is −0.1 V with a prominent oxidation peak at 0.263 V.

Preparation of graphene oxide by dry planetary ball milling process from natural graphite

Graphene oxides (GO) with different degrees of oxidation have been prepared by an in-house designed horizontal high energy planetary ball milling process. The prepared graphene oxides have been studied by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) with selected area electron diffraction (SAED), high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), micro Raman spectroscopy, Fourier transform infrared (FTIR) spectra, Brunauer–Emmett–Teller (BET) test and thermogravimetric analysis (TGA). XPS study shows an increasing trend of atomic concentration ratio of O/C with increasing ball milling time duration from 2 to 24 h of high purity graphite sample (FEED). This result is attributed to the formation of more oxidation in the graphite sample, produced due to the increasing time duration of milling. From micro Raman analysis it is also noted that ID/IG ratio increases with increasing milling time of FEED, which further supported the preparation of graphene oxide. In this study the graphene oxide prepared by 16 h of milling may be considered as the optimized sample as far as the degree of oxidation, time and energy consumption factors are concerned.

Photocatalytic destruction of Escherichia coli in water by V2O5/TiO2

Vanadia modified titania (V₂O₅/TiO₂) photo-catalysts are prepared by incipient wet impregnation method using aqueous ammonium metavanadate and anatase (Aldrich) titania. Titania with various loading concentrations of vanadia from 0 to 10 wt.% have been prepared and characterized by X-ray diffraction (XRD), Thermogravimetry (TGA), Laser Raman Spectroscopy, Fourier Transform Infrared Spectroscopy (FTIR), X-ray Photoelectron Spectroscopy (XPS), UV-Visible Spectrophotometry and Transmission Electron Microscopy (TEM). XRD study reveals that vanadia loading on titania does not bring any phase change of titania, however, diffuse (UV-Vis) reflectance spectra show that absorption edge of titania shifted from UV to visible region. TEM confirms that titania and vanadia modified titania have the particle size below 50 nm. XPS shows alteration of 2p₃/₂ peak of V(V) in the V₂O₅/TiO₂ samples whereas no such change is noticed in pure V₂O₅ indicating the interaction between vanadia and titania support. Antibacterial activity of each sample has been investigated against Escherichia coli present in the water under both UV-Visible irradiation and UV alone. V₂O₅/TiO₂ catalysts exhibit better photocatalytic effect than the unmodified titania and pure V₂O₅. It is observed that with increasing loading concentrations of V₂O₅ from 0 to 10 wt.% on titania support, the photocatalytic annihilation of E.coli is also increased and found to be little higher under UV alone than the UV-Visible irradiation.