RAJAGOPAL S

@psgcas.ac.in

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

RAJAGOPAL S


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https://researchid.co/rajagopals
Indian

RESEARCH, TEACHING, or OTHER INTERESTS

Materials Science, Atomic and Molecular Physics, and Optics, Condensed Matter Physics, Materials Chemistry
14

Scopus Publications

730

Scholar Citations

10

Scholar h-index

10

Scholar i10-index

Scopus Publications

  • Effect of synthesis conditions on Rheodiscolor leaf-derived carbon quantum dots as electrolytes for energy storage applications
    B.K. Nagendraprasad, Rajagopal Shanmugasundaram, M. Chethan, Karthik Kumara, M. Sathish, S. Thiyagaraj
    Next Materials, 2026
    Carbon Quantum Dots (CQDs) were synthesized from Rheodiscolor leaf extract using Soxhlet extraction followed by a hydrothermal process in four variants: S1 (raw CQDs), S2 (5 % ethanol-CQDs), S3, and S4. UV–Visible absorption bands at 211–339 nm and excitation-dependent photoluminescence (315–475 nm) confirmed moderate quantum confinement. FTIR spectra identified O–H (∼3400 cm⁻¹) and C O (∼1645 cm⁻¹) groups, with additional C–H and C C bands in S2–S4 enhancing solubility. Electrochemical characterization using GCD and cyclic voltammetry (CV) revealed contrasting outcomes: GCD showed reduced capacitance of GCE for all CQD variants compared to KOH, with S1 retaining 45–54 % and S4 only 20–38 %, whereas CV indicated strong, stable performance of GCE for CQDs (S1–S3) (∼80–88 % of KOH) and moderate retention for CQD (S4) (43–60 %). These findings suggest that Rheodiscolor leaf-derived CQDs, especially S1–S3, are promising, sustainable, and tunable electrolyte materials for energy storage applications, with properties strongly influenced by synthesis conditions.
  • Insight into unusual complex thermodynamical behaviour of citric acid and ethanolamine solution
    Reshma Karunakaran, Rajagopal Shanmugasundaram
    Discover Materials, 2025
    Inverse freezing fluids (IFF) are the new field of science that thermodynamically acts opposite to conventional fluids. These IFFs are novel artificial materials that work as typical thermal metamaterials. This paper reports the IFF phenomenon with basic chemicals such as citric acid and ethanolamine subjected to different conditions. The amine molecule within the precursor compound is crucial in attaining this phenomenon. Its respective inter and intramolecular ‘hydrogen’ atoms remain the key reason for this effect. Results of rheometry, Raman, proton nuclear magnetic resonance (1HNMR), photoluminescence (PL) spectroscopy, and thermogravimetric analysis (TGA) of this fluid confirmed this phenomena, collectively. Experimental findings confirm the reversible phase transformation which is contrary to the conventional fluids. It will open the interest in finding new thermal metamaterials. This study can be considered the first attempt at synthesizing IFFs through a new preparation method and analysed in detail. Many challenges were faced during synthesis and characterizations, so this study will help to resolve the complexity in this domain. Further, the sample was sintered and found to be multi-layered reduced graphene oxide (rGO) powder. This rGO sample’s structural, chemical nature, and morphology are studied through x-ray diffraction (XRD), Fourier transformed infra-red (FTIR), Raman spectroscopy, scanning electron microscope (SEM), transmission electron microscope imaging and energy dispersive analysis of x-rays (EDAX). XRD pattern confirmed the presence of the main peak at 26° (2θ) corresponding to the basal reflection (002) of rGO phase. It was further evidenced by its D and G bands of Raman spectra at 1357 and 1574 cm−1, respectively. FTIR analysis also revealed a reduced OH- band whereas EDAX analysis confirms the purity of rGO by the presence of carbon and oxygen peaks only. Multilayer formation of rGO was confirmed by SEM and TEM observations and found that the measured thickness of the sheet was nearly 1 nm.
  • Radiation attenuation effectiveness of the inverse freezing fluid - a new shielding material for gamma radiation
    Reshma Karunakaran, Rajagopal Shanmugasundaram
    Discover Applied Sciences, 2025
    The inverse freezing fluids are the new field of science, in which the synthesised fluid mixtures freezes at high temperature and liquifies at lower temperature. Recently we observed such a new thermal and thermal–mechanical metamaterial behaviour from the liquid mixtures of citric acid and ethanolamine solution under different conditions. This new science is still in the basic research stage with no applications so far developed. This is the first paper which gives a detailed description about the application of such inverse freezing fluids. Here we have opted to study the gamma radiation shielding of the synthesised inverse freezing fluids (IFF) namely, pure IFF and metals such as, vanadium and molybdenum doped IFF samples. From the data reported and analysis in this manuscript, it is evident that different liquids mixtures, especially, IFF’s can be used for gamma radiation shielding with varying temperature. We found better shielding parameters while taking IFF’s at higher temperature. The effect of temperature has influenced the radiation absorption and transmittance through the samples. Comparison plots were given for better understanding with which the molybdenum doped sample shows better shielding than the other two samples. In case of the Co-60 source the absorption factor is 0.3418, LAC is 1.1396 cm−1 and MFP was 0.8774 cm−1 for molybdenum doped samples which are evidently more compared to the vanadium doped samples. To the best of our knowledge this is the first comprehensive study exploring the temperature dependent gamma attenuation properties of the soft matter which is initially in the liquid form. Fundamental discovery of such IFF’s are promising research materials, in the context of emerging liquid phase systems for the radiation shielding applications.
  • Green synthesis and characterization of Mn3O4 nanoparticles for photocatalytic and supercapacitors
    H. S. Sumantha, S. Rajagopal, M. Shashank, G. Nagaraju, Vinayak K. Pattar, Pavithra Shanmugaraj, Sakunthala Ayyasamy, B. L. Suresha
    Ionics, 2023
  • Facile and eco-friendly combustion synthesis of NiO particles for photodegradation studies
    H.S. Sumantha, S. Rajagopal, G. Nagaraju, M. Shashank, B.L. Suresha
    Chemical Physics Letters, 2021
  • Crystal structure and electronic properties of facile synthesized Cr2O3 nanoparticles
    S Rajagopal, M Bharaneswari, D Nataraj, O Y Khyzhun, Yahia Djaoued
    Materials Research Express, 2016
    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 MoO3 hybrid nanostructures and investigation of their photocatalytic activity
    S. Rajagopal, M. Bharaneswari, D. Nataraj, O. Y. Khyzhun, Yahia Djaoued
    Rsc Advances, 2016
    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, Chang-Koo Kim
    Korean Journal of Chemical Engineering, 2013
  • Controlled synthesis of MoO3 microcrystals by subsequent calcination of hydrothermally grown pyrazine-MoO3 nanorod hybrids and their photodecomposition properties
    S. Rajagopal, D. Nataraj, O.Y. Khyzhun, Yahia Djaoued, Jacques Robichaud, Chang-Koo Kim
    Materials Chemistry and Physics, 2013
  • Effect of partial preferential orientation and distortions in octahedral clusters on the photoluminescence properties of FeWO4 nanocrystals
    M. A. P. Almeida, L. S. Cavalcante, C. Morilla-Santos, C. J. Dalmaschio, S. Rajagopal, M. Siu Li, E. Longo
    Crystengcomm, 2012
    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 3 hybrid nanostructures
    S. Rajagopal, D. Nataraj, O. Yu. Khyzhun, Yahia Djaoued, Jacques Robichaud, K. Senthil, D. Mangalaraj
    Crystengcomm, 2011
  • Electronic structure of FeWO4 and CoWO4 tungstates: First-principles FP-LAPW calculations and X-ray spectroscopy studies
    S. Rajagopal, V.L. Bekenev, D. Nataraj, D. Mangalaraj, O.Yu. Khyzhun
    Journal of Alloys and Compounds, 2010
  • Hydrothermal synthesis and electronic properties of FeWO4 and CoWO4 nanostructures
    S. Rajagopal, D. Nataraj, O. Yu. Khyzhun, Yahia Djaoued, J. Robichaud, D. Mangalaraj
    Journal of Alloys and Compounds, 2010
  • Controlled growth of WO 3 nanostructures with three different morphologies and their structural, optical, and photodecomposition studies
    S Rajagopal, D Nataraj, D Mangalaraj, Yahia Djaoued, Jacques Robichaud, O Yu Khyzhun
    Nanoscale Research Letters, 2009

RECENT SCHOLAR PUBLICATIONS

  • Insight into unusual complex thermodynamical behaviour of citric acid and ethanolamine solution
    K Reshma, S Rajagopal
    Discover Materials 5 (18) , 2025
    2025
    Citations: 4
  • Effect of synthesis conditions on Rheodiscolor leaf-derived carbon quantum dots as electrolytes for energy storage applications
    BK Nagendraprasad, S Rajagopal, M Chethan, K Kumara, M Sathish, ...
    Next Materials 10, 101500 , 2025
    2025
  • Radiation attenuation effectiveness of the inverse freezing fluid - a new shielding material for gamma radiation
    K Reshma, S Rajagopal
    Discover Applied Sciences 7 (926) , 2025
    2025
    Citations: 1
  • Green synthesis and characterization of Mn 3 O 4 nanoparticles for photocatalytic and supercapacitors
    HS Sumantha, S Rajagopal, M Shashank, G Nagaraju, VK Pattar, ...
    Ionics 29 (2), 733-749 , 2023
    2023
    Citations: 22
  • 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
    2021
    Citations: 24
  • 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
    2016
    Citations: 18
  • 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
    2016
    Citations: 30
  • 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 (10), 1833-1835 , 2013
    2013
    Citations: 9
  • 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
    2013
    Citations: 24
  • 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
    2012
    Citations: 42
  • 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
    2011
    Citations: 74
  • 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
    2010
    Citations: 98
  • 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
    2010
    Citations: 201
  • 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
    2009
    Citations: 183

MOST CITED SCHOLAR PUBLICATIONS

  • 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
    2010
    Citations: 201
  • 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
    2009
    Citations: 183
  • 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
    2010
    Citations: 98
  • 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
    2011
    Citations: 74
  • 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
    2012
    Citations: 42
  • 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
    2016
    Citations: 30
  • 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
    2021
    Citations: 24
  • 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
    2013
    Citations: 24
  • Green synthesis and characterization of Mn 3 O 4 nanoparticles for photocatalytic and supercapacitors
    HS Sumantha, S Rajagopal, M Shashank, G Nagaraju, VK Pattar, ...
    Ionics 29 (2), 733-749 , 2023
    2023
    Citations: 22
  • 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
    2016
    Citations: 18
  • 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 (10), 1833-1835 , 2013
    2013
    Citations: 9
  • Insight into unusual complex thermodynamical behaviour of citric acid and ethanolamine solution
    K Reshma, S Rajagopal
    Discover Materials 5 (18) , 2025
    2025
    Citations: 4
  • Radiation attenuation effectiveness of the inverse freezing fluid - a new shielding material for gamma radiation
    K Reshma, S Rajagopal
    Discover Applied Sciences 7 (926) , 2025
    2025
    Citations: 1
  • Effect of synthesis conditions on Rheodiscolor leaf-derived carbon quantum dots as electrolytes for energy storage applications
    BK Nagendraprasad, S Rajagopal, M Chethan, K Kumara, M Sathish, ...
    Next Materials 10, 101500 , 2025
    2025