RAJAGOPAL S
@psgcas.ac.in
Assistant Professor , Department of Physics
PSG College of Arts & Science
Indian
RESEARCH, TEACHING, or OTHER INTERESTS
Materials Science, Atomic and Molecular Physics, and Optics, Condensed Matter Physics, Materials Chemistry
Scopus Publications
Scholar Citations
Scholar h-index
Scholar i10-index
Scopus Publications
H. S. Sumantha, S. Rajagopal, M. Shashank, G. Nagaraju, Vinayak K. Pattar, Pavithra Shanmugaraj, Sakunthala Ayyasamy, and B. L. Suresha
Springer Science and Business Media LLC
H.S. Sumantha, S. Rajagopal, G. Nagaraju, M. Shashank, and B.L. Suresha
Elsevier BV
S Rajagopal, M Bharaneswari, D Nataraj, O Y Khyzhun, and Yahia Djaoued
IOP Publishing
We report on a facile method of synthesis of Cr2O3 nanoparticles by hydrothermal method. Chromium sulfate was used as a starting material whereas urea was used as a strong reducing agent. Cr2O3 nanoparticles, with rhombohedral crystal structure, have been synthesized, when the reaction solution was treated under hydrothermal condition at high pH (10). At pH = 8 amorphous Cr2O3 powders were obtained. Chromium oxide could not be synthesized in the absence of urea. Two different Raman modes have been detected for the final products synthesized at the high pH value. As-prepared Cr2O3 nanoparticles reveal agglomeration as evidenced from scanning electron microscope (SEM) images. Flake-like Cr2O3 nanoparticles, 20 to 50 nm in size, show clear lattice fringes through the high resolution transmission electron microscope (HRTEM) images. The electronic structure of the Cr2O3 nanoparticles has been studied employing x-ray photoelectron spectroscopy (XPS) and x-ray emission spectroscopy (XES) methods.
S. Rajagopal, M. Bharaneswari, D. Nataraj, O. Y. Khyzhun, and Yahia Djaoued
Royal Society of Chemistry (RSC)
An organic–inorganic hybrid was synthesized using 2,2′-dipyridyl and MoO3 nanorods via simple hydrothermal method. Here, dipyridyl has acted as stretching molecule and bonded the MoO3 nanorods together along the length to form hybrid micro crystals.
Shanmugasundaram Rajagopal, Hae-Min Lee, Kangtaek Lee, and Chang-Koo Kim
Springer Science and Business Media LLC
S. Rajagopal, D. Nataraj, O.Y. Khyzhun, Yahia Djaoued, Jacques Robichaud, and Chang-Koo Kim
Elsevier BV
M. A. P. Almeida, L. S. Cavalcante, C. Morilla-Santos, C. J. Dalmaschio, S. Rajagopal, M. Siu Li, and E. Longo
Royal Society of Chemistry (RSC)
This communication is a report of our initial research to obtain iron tungstate (FeWO4) nanocrystals by the microwave-hydrothermal method at 170 °C for 45 min. X-ray diffraction patterns showed that the FeWO4 nanocrystals prepared with polyethylene glycol-200 have a partial preferential orientation in the (011) plane in relation to other nanocrystals prepared with sodium bis(2-ethylhexyl)sulfosuccinate and water. Rietveld refinement data indicates that all nanocrystals are monophasic with wolframite-type monoclinic structures and exhibit different distortions on octahedral [FeO6]/[WO6] clusters. High resolution transmission electron microcopy revealed an oriented attachment mechanism for the growth of aggregated FeWO4 nanocrystals. Finally, we observed that the photoluminescence properties of these nanocrystals are affected by partial preferential orientation in the (011) plane and distortions on [FeO6]/[WO6] clusters.
S. Rajagopal, D. Nataraj, O. Yu. Khyzhun, Yahia Djaoued, Jacques Robichaud, K. Senthil, and D. Mangalaraj
Royal Society of Chemistry (RSC)
High aspect ratio molybdenum trioxide (MoO3) nanorods grown along the [100] direction were successively synthesized by a simple hydrothermal method. We used sodium molybdate and hydrochloric acid as starting materials and from their reaction we obtained MoO3 nanorods of high aspect ratio. The dimensions of the nanorods were found to be uniform in size, with well-defined boundaries. The intercalation of an organic molecule (pyrazine) into these nanorods has resulted in single-crystalline MoO3 microstructures, with a change in their length and breadth of a few orders. Pyrazine has acted as a stitching molecule and has bound the nanorods together along their length to form micron sized single crystalline MoO3. The presence of pyrazine and its intercalation was confirmed by a uniform shift in the XRD [0k0] peak positions. As the size of the pyrazine is similar to the van der Waals gap of the orthorhombic MoO3 crystal, it seemed to fit well within the gap and thereby helped to bind the nanorods along the [0k0] direction. The Raman ring deformation modes, at 714 and 996 cm−1, have also supported the intercalation of the pyrazine in the van der Waals gap. The deintercalation process was done by calcinating the sample at 400 °C and the removal of pyrazine was confirmed by TGA and XRD measurements. The influence of pyrazine in the valence band electronic density of states (DOS) of MoO3 was also analyzed by XPS and XES methods. The replacement of oxygen at the van der Waals gap by nitrogen from the intercalating pyrazine caused a shift in the valence band towards the Fermi level. A photoluminescence study was also conducted, reflecting the intercalation effect on the emission characteristics of the MoO3 nanostructures.
S. Rajagopal, V.L. Bekenev, D. Nataraj, D. Mangalaraj, and O.Yu. Khyzhun
Elsevier BV
S. Rajagopal, D. Nataraj, O. Yu. Khyzhun, Yahia Djaoued, J. Robichaud, and D. Mangalaraj
Elsevier BV
S Rajagopal, D Nataraj, D Mangalaraj, Yahia Djaoued, Jacques Robichaud, and O Yu Khyzhun
Springer Science and Business Media LLC
Abstract Tungsten trioxide (WO3) nanostructures were synthesized by hydrothermal method using sodium tungstate (Na2WO4·2H2O) alone as starting material, and sodium tungstate in presence of ferrous ammonium sulfate [(NH4)2Fe(SO4)2·6H2O] or cobalt chloride (CoCl2·6H2O) as structure-directing agents. Orthorhombic WO3having a rectangular slab-like morphology was obtained when Na2WO4·2H2O was used alone. When ferrous ammonium sulfate and cobalt chloride were added to sodium tungstate, hexagonal WO3nanowire clusters and hexagonal WO3nanorods were obtained, respectively. The crystal structure and orientation of the synthesized products were studied by X-ray diffraction (XRD), micro-Raman spectroscopy, and high-resolution transmission electron microscopy (HRTEM), and their chemical composition was analyzed by X-ray photoelectron spectroscopy (XPS). The optical properties of the synthesized products were verified by UV–Vis and photoluminescence studies. A photodegradation study on Procion Red MX 5B was also carried out, showing that the hexagonal WO3nanowire clusters had the highest photodegradation efficiency.