RAJAGOPAL S

@psgcas.ac.in

Assistant Professor , Department of Physics
PSG College of Arts & Science

https://researchid.co/rajagopals

Indian

RESEARCH, TEACHING, or OTHER INTERESTS

Materials Science, Atomic and Molecular Physics, and Optics, Condensed Matter Physics, Materials Chemistry

Scopus Publications

652

Scholar Citations

Scholar h-index

Scholar i10-index

Scopus Publications

Insight into unusual complex thermodynamical behaviour of citric acid and ethanolamine solution
Reshma Karunakaran and Rajagopal Shanmugasundaram
Springer Science and Business Media LLC

Green synthesis and characterization of Mn<inf>3</inf>O<inf>4</inf> nanoparticles for photocatalytic and supercapacitors
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

Facile and eco-friendly combustion synthesis of NiO particles for photodegradation studies
H.S. Sumantha, S. Rajagopal, G. Nagaraju, M. Shashank, and B.L. Suresha
Elsevier BV

Crystal structure and electronic properties of facile synthesized Cr<inf>2</inf>O<inf>3</inf> nanoparticles
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.

Systematic synthesis and analysis of change in morphology, electronic structure and photoluminescence properties of 2,2′-dipyridyl intercalated MoO<inf>3</inf> hybrid nanostructures and investigation of their photocatalytic activity
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.

Hydrothermal synthesis of one-dimensional tungsten oxide nanostructures using cobalt ammonium sulfate as a structure-directing agent
Shanmugasundaram Rajagopal, Hae-Min Lee, Kangtaek Lee, and Chang-Koo Kim
Springer Science and Business Media LLC

Controlled synthesis of MoO<inf>3</inf> microcrystals by subsequent calcination of hydrothermally grown pyrazine-MoO<inf>3</inf> nanorod hybrids and their photodecomposition properties
S. Rajagopal, D. Nataraj, O.Y. Khyzhun, Yahia Djaoued, Jacques Robichaud, and Chang-Koo Kim
Elsevier BV

Effect of partial preferential orientation and distortions in octahedral clusters on the photoluminescence properties of FeWO<inf>4</inf> nanocrystals
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.

Systematic synthesis and analysis of change in morphology, electronic structure and photoluminescence properties of pyrazine intercalated MoO <inf>3</inf> hybrid nanostructures
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.

Electronic structure of FeWO<inf>4</inf> and CoWO<inf>4</inf> tungstates: First-principles FP-LAPW calculations and X-ray spectroscopy studies
S. Rajagopal, V.L. Bekenev, D. Nataraj, D. Mangalaraj, and O.Yu. Khyzhun
Elsevier BV

Hydrothermal synthesis and electronic properties of FeWO<inf>4</inf> and CoWO<inf>4</inf> nanostructures
S. Rajagopal, D. Nataraj, O. Yu. Khyzhun, Yahia Djaoued, J. Robichaud, and D. Mangalaraj
Elsevier BV

Controlled growth of WO <inf>3</inf> nanostructures with three different morphologies and their structural, optical, and photodecomposition studies
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.

RECENT SCHOLAR PUBLICATIONS

Insight into unusual complex thermodynamical behaviour of citric acid and ethanolamine solution
K Reshma, S Rajagopal
Discover Materials 5 (18) 2025

Green synthesis and characterization of Mn₃O₄ nanoparticles for photocatalytic and supercapacitors
HS Sumantha, S Rajagopal, M Shashank, G Nagaraju, VK Pattar, ...
Ionics 29 (2), 733-749 2023

Facile and eco-friendly combustion synthesis of NiO particles for photodegradation studies
HS Sumantha, S Rajagopal, G Nagaraju, M Shashank, BL Suresha
Chemical Physics Letters 779, 138837 2021

Systematic synthesis and analysis of change in morphology, electronic structure and photoluminescence properties of 2, 2’-Dipyridyl intercalated MoO3 hybrid nanostructures and
S Rajagopal, M Bharaneswari, D Nataraj, O Y Khyzhun and Yahia Djaoued
RSC Advances 6, 88287 - 88299 2016

Crystal structure and electronic properties of facile synthesized Cr2O3 nanoparticles
S Rajagopal, M Bharaneswari, D Nataraj, O Y Khyzhun, Yahia Djaoued
Materials Research Express 3, 095019 2016

Hydrothermal synthesis of one-dimensional tungsten oxide nanostructures using cobalt ammonium sulfate as a structure-directing agent
S Rajagopal, HM Lee, K Lee, CK Kim
Korean Journal of Chemical Engineering 30, 1833-1835 2013

Controlled synthesis of MoO3 microcrystals by subsequent calcination of hydrothermally grown pyrazine–MoO3 nanorod hybrids and their photodecomposition properties
S Rajagopal, D Nataraj, OY Khyzhun, Y Djaoued, J Robichaud, CK Kim
Materials Chemistry and Physics 141 (1), 383-392 2013

Effect of partial preferential orientation and distortions in octahedral clusters on the photoluminescence properties of FeWO 4 nanocrystals
MAP Almeida, LS Cavalcante, C Morilla-Santos, CJ Dalmaschio, ...
CrystEngComm 14 (21), 7127-7132 2012

Systematic synthesis and analysis of change in morphology, electronic structure and photoluminescence properties of pyrazine intercalated MoO 3 hybrid nanostructures
S Rajagopal, D Nataraj, OY Khyzhun, Y Djaoued, J Robichaud, K Senthil, ...
CrystEngComm 13 (7), 2358-2368 2011

Electronic structure of FeWO4 and CoWO4 tungstates: First-principles FP-LAPW calculations and X-ray spectroscopy studies
S Rajagopal, VL Bekenev, D Nataraj, D Mangalaraj, OY Khyzhun
Journal of alloys and compounds 496 (1-2), 61-68 2010

Hydrothermal synthesis and electronic properties of FeWO4 and CoWO4 nanostructures
S Rajagopal, D Nataraj, OY Khyzhun, Y Djaoued, J Robichaud, ...
Journal of alloys and compounds 493 (1-2), 340-345 2010

Controlled growth of WO 3 nanostructures with three different morphologies and their structural, optical, and photodecomposition studies
S Rajagopal, D Nataraj, D Mangalaraj, Y Djaoued, J Robichaud, ...
Nanoscale research letters 4 (11), 1335-1342 2009

MOST CITED SCHOLAR PUBLICATIONS

Crystal structure and electronic properties of facile synthesized Cr2O3 nanoparticles
S Rajagopal, M Bharaneswari, D Nataraj, O Y Khyzhun, Yahia Djaoued
Materials Research Express 3, 095019 2016
Citations: 24

Facile and eco-friendly combustion synthesis of NiO particles for photodegradation studies
HS Sumantha, S Rajagopal, G Nagaraju, M Shashank, BL Suresha
Chemical Physics Letters 779, 138837 2021
Citations: 19

Green synthesis and characterization of Mn₃O₄ nanoparticles for photocatalytic and supercapacitors
HS Sumantha, S Rajagopal, M Shashank, G Nagaraju, VK Pattar, ...
Ionics 29 (2), 733-749 2023
Citations: 10