Charanjit Singh

Enhanced Photocatalytic Degradation of Methylene Blue Using /MWCNT Composite Synthesized by Hydrothermal Method

Multiwalled carbon nanotubes (MWCNTs) were synthesized using arc discharge method at a magnetic field of 430 G and purified using HNO3/H2O2. Transmission electron micrographs revealed that MWCNTs had inner and outer diameter of ~2 nm and ~4 nm, respectively. Raman spectroscopy confirmed formation of MWCNTs showing G-band at 1577 cm−1. ZnFe2O4 and ZnFe2O4/MWCNT were produced using one step hydrothermal method. Powder X-ray diffraction (XRD) confirmed the formation of cubic spinel ZnFe2O4 as well as incorporation of MWCNT into ZnFe2O4. Visible light photocatalytic degradation of methylene blue (MB) was studied using pure ZnFe2O4 and ZnFe2O4/MWCNT. The results showed that ZnFe2O4/MWCNT composite had higher photocatalytic activity as compared to pure ZnFe2O4. After irradiation for 5 hours in the visible light, MB was almost 84% degraded in the presence of ZnFe2O4 photocatalyst, while 99% degradation was observed in case of ZnFe2O4/MWCNT composite. This enhancement in the photocatalytic activity of composite may be attributed to the inhibition of recombination of photogenerated charge carriers.

Encrustation of cobalt doped copper ferrite nanoparticles on solid scaffold CNTs and their comparison with corresponding ferrite nanoparticles: a study of structural, optical, magnetic and photo catalytic properties

Cobalt doped copper ferrite nanoparticles and their nanocomposites with carbon nanotubes (CNTs) were synthesized by microemulsion method where sodium dodecyl sulphate was used as soft templating agent to control the particle size and shape. Powder X-ray diffraction technique confirmed the formation of cobalt doped copper ferrite nanoparticles and their corresponding nanocomposites. A significant decrease in the lattice parameter was observed using Le-bail refinement method which confirmed the doping of cobalt ion in to the copper ferrite lattice. Appearance of peak at around 25.9° indicated that CNTs remain unaffected during synthesis procedure. High Resolution Transmission Electron Microscopy (HR-TEM) was used to estimate the particle size, shape and uniformity of all the synthesized samples. Particle size was observed to be around 4–5 nm. A fine layer of ferrite nanoparticles on the surface of CNTs was also confirmed. Optical studies of the entire samples showed wide coverage of visible light spectrum from 675–1050 nm. Magnetic studies of the all samples were carried out using vibrating sample magnetometer and a significant increase in the saturation magnetization and coercivity values with cobalt ion doping was observed. This increase could be attributed to the higher magnetic moment of Co2+ ions (3 μB) as compared to Cu2+ ion (1 μB) at B-sub lattice. Comparative photocatalytic activity was also elevated and it was found that ferrite–CNTs nanocomposites show higher catalytic activities for the degradation of Rhodamine B dye in comparison with the ferrite nanoparticles.

CdS nanorod–MFe2O4 (M = Zn, Co and Ni) nanocomposites: a heterojunction synthesis strategy to mitigate environmental deterioration

A facile strategy to encrust MFe2O4 (M = Zn, Co and Ni) nanoparticles over CdS nanorods via a two-step solvothermal method has been reported. The ferrite–CdS nanocomposites (NCs) were characterized using powder X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy. A shift in the peak corresponding to the (311) plane confirmed the presence of different metal ions in the spinel ferrite lattice. However, no variation in the peak of CdS was observed which indicates that the phase and morphology of the CdS nanorods remain unaltered after hydrothermal treatment. High resolution transmission electron microscopy (HR-TEM) analysis revealed the efficacious attachment of the nanoferrite on the CdS nanorods. Optical studies of the NC samples provided information about the fabrication of the visible light responsive photocatalyst and covered the solar spectrum from 525 nm to 737 nm. From magnetic studies, CdS–CoFe2O4 and CdS–NiFe2O4 were found to be ferromagnetic in nature with a saturation magnetization of 26.4 and 15.5 emu g−1, respectively. Interestingly, a transition from ferromagnetic to super-paramagnetic was observed for the ZnFe2O4 loaded CdS nanorods. The photo-catalytic activities of the nanocomposites were studied by carrying out photo-degradation of rhodamine B and methylene blue dyes under visible-light irradiation. The maximum activity was observed in the case of the CdS–ZnFe2O4 nanocomposites.

Effect of Magnetic Field on the Growth of Aligned Carbon Nanotubes Using a Metal Free Arc Discharge Method and their Purification

Multiwalled Carbon Nanotubes (MWCNTs) have been synthesized using a low cost arc discharge method without using metal catalyst and vacuum devices. Effect of magnetic field on the synthesis of MWCNTs and their purity has been scrutinized. A magnetic field of 310 gauss has been found to give better purity of carbon nanotubes as confirmed by Raman spectroscopy. However, the removal of amorphous carbon from the surface of so prepared multiwalled carbon nanotubes has been achieved by different oxidizing conditions. It has been observed that the maximum removal of amorphous carbon found by using the strong oxidizing agent HNO3/H2O2. This strong oxidizing agent HNO3/H2O2 removes most of the carbonaceous impurities leading to thermal stability of carbon nanotubes suggested by thermo gravimetric analysis. X-ray diffraction show the formation of carbon nanotubes having a peak indexed at (002) as the fingerprint for multiwalled carbon nanotubes. Fourier Transform Infrared (FTIR) spectra confirmed the formation of the multiwalled carbon nanotubes showing a characteristic stretching band at 1615 cm-1 corresponding to the C=C bonds of tubular carbon. Raman spectroscopy revealed invaluable insights into the purification of nanotubes. G-band (1577 cm-1) corresponds to the confirmation of MWCNTs. Defect induced D-band (1355 cm-1) has been minimized after purifying CNTs with HNO3/H2O2 for 24 hrs. Transmission Electron microscopic (TEM) studies indicate the formation of CNTs with controlled alignment having diameter in the range 2-8 nm.

Production of carbon nanotubes by AC arc discharge method

We describe a method for the synthesis of multiwalled carbon nanotubes by AC arc discharge. The discharge is maintained in a magnetic field whose strength can be varied. The soot obtained was purified in several steps. The structure and morphology of the MWCNTs thus produced are characterized by using Transmission Electron Microscopy (TEM) and Raman Spectroscopy. The produced MWCNTs are found to be of high quality as seen from characterization results. However there is wide dispersion in outer diameter and number of walls.

Morphology Controlled CdS Nanostructures: A Proficient Visible-Light-Driven Photocatalyst

Abstract Visible light driven catalytically active CdS morphologies viz. nanoparticles, nanorods, nanospheres and nanoflowers were fabricated via facile and versatile solvothermal method by adjusting the experimental conditions. The fabricated samples were critically analyzed using Powder X-ray Diffraction, High Resolution Transmission Electron Microscopy, Brunauer-Emmett-Teller and UV-vis Diffused Reflectance Spectrum. Elemental composition of CdS samples was confirmed by using Energy Dispersive X-ray Spectroscopy. Crystallite size for CdS nanoparticles was found to be ∼ 4 nm while in case of other morphologies, it was found to be in range of 27-33 nm. Optical studies revealed the information about the band gap of visible light responsive photocatalysts and covered the solar spectrum from 525 nm to 650 nm. Photocatalytic activities of all the CdS morphologies were compared using methylene blue, methyl orange, safranin O, rhodamine B and remazol brilliant yellow as probe molecule. The different CdS morphologies were found to exhibit dissimilar catalytic efficacy, which was due to the fact that there was large difference in the surface area of the samples. The experimental results were found to be in accordance with the order: CdS nanoparticles > CdS nanorods > CdS nanospheres ∼ CdS nanoflowers. Therefore, CdS morphology with better catalytic activity can be deduced as an ideal catalyst for the treatment of dye waste water.