Asokan Kandasami
@iuac.res.in
Scientist H
Inter University Accelerator Centre
RESEARCH INTERESTS
ion beam interactions, Synchrotron-based XAS and other techniques
Scopus Publications
Scopus Publications
N.D. Raskar, D.V. Dake, V.A. Mane, R.B. Sonpir, M. Vasundhara, K. Asokan, U. Deshpande, R. Venkatesh, V.D. Mote, and B.N. Dole
Elsevier BV
Hetal Kundalia, Brinda Vyas, Malay Udeshi, Ashish Ravalia, K Asokan, and D.G. Kuberkar
Elsevier BV
Debashish Sen, Shaila Bahl, Pooja Seth, Birendra Singh, A. Pandey, Mohammad Zulfequar, and Asokan Kandasami
Elsevier BV
Kurinjinathan Panneerselvam, Anita R. warrier, Roselin Ranjitha Mathiarasu, Ta Thi Thuy Nga, Ramana Ramya J, Thanigai Arul Kumaravelu, Wu-Ching Chou, Yu-Cheng Huang, Jeng-Lung Chen, Chi-Liang Chen,et al.
Elsevier BV
Keval Gadani, Faizal Mirza, Davit Dhruv, K. Asokan, P. S. Solanki, N. A. Shah, and A. D. Joshi
Springer Science and Business Media LLC
N.D. Raskar, D.V. Dake, V.A. Mane, R.B. Sonpir, H.A. Khawal, V.D. Mote, M. Vasundhara, K. Asokan, K.P. Gattu, and B.N. Dole
Elsevier BV
I-Han Wu, Arvind Chandrasekar, Kumaravelu Thanigai Arul, Yu-Cheng Huang, Ta Thi Thuy Nga, Chi-Liang Chen, Jeng-Lung Chen, Da-Hua Wei, Kandasami Asokan, Ping-Hung Yeh,et al.
Elsevier BV
Bhargav Rajyaguru, Keval Gadani, Himanshu Dadhich, Davit Dhruv, V. Ganesan, K. Asokan, N.A. Shah, and P.S. Solanki
Elsevier BV
Hardik Gohil, Keval Gadani, Hetal Boricha, Bhargav Rajyaguru, Himanshu Dadhich, Nisarg Raval, Davit Dhruv, V.R. Rathod, N.P. Barde, P.P. Bardapurkar,et al.
Elsevier BV
Kishor H. Gavhane, M.S. Bhadane, Preeti P. Kulkarni, Vikas Kashid, V.S. Ghemud, K. Hareesh, K. Asokan, Anjali Kshirsagar, V.N. Bhoraskar, S.D. Dhole,et al.
Elsevier BV
Riya Dawn, Rajashri Urkude, Shilpa Tripathi, Satyaban Bhunia, Weng Weei Tjiu, Zainul Aabdin, Asokan Kandasami, and Vijay Raj Singh
IOP Publishing
Abstract The evolution of the nanostructures and electronic properties of 5% cobalt-doped TiO2 nanoparticles (NPs) annealed at 400 °C, 600 °C, and 800 °C have been investigated to understand the structural phase transformations through chemical co-precipitation synthesis. A detailed analysis of the X-ray Diffractogram confirms that the sample annealed at 400 °C is anatase, at 600 °C, the mixed phase of anatase and rutile evolves, and at 800 °C, the sample is of rutile structure. A detailed morphological study by scanning transmission electron microscope provides the particle size, lattice spacing, and variation in polycrystalline grain growth at different phases. Electron Energy Loss Spectroscopy analysis indicates from the O K, Co, and Ti L 2,3-edges that Ti4+ ions are primarily in an octahedral symmetry with the oxygen ligands changing their structural phases from anatase to mixed phase and then stable rutile phase with increasing temperature of annealing. X-ray Absorption Near Edge Spectroscopy (XANES) extracts information about the varying oxidation states and 3-dimensional geometry of Ti-ions. The unresolved issues of the structural details at the atomic-scale picture with the local environment of the cation with a few nearest neighbour shells are derived from Extended X-ray Absorption Fine Structure (EXAFS) and pre-edge parts of the absorption spectra. The limits of EXAFS in this situation of asymmetric bond length disorder, which is typical for mixed-valence oxides, are generated to reconcile the two data and highlight the value of pre-edge XANES analysis for identifying local heterogeneities in structural and compositional motifs. TiO2 possesses unique properties depending upon its structural phase. The Ti L 2,3-edge spectrum indicates that there is an octahedron connectivity of the Oxygen atoms at the anatase state which transforms to a higher energetic tetrahedral correspondence as it proceeds towards the rutile phase. The driving force behind such interest is to modulate the properties of TiO2 NPs to better photocatalytic material and to integrate its application as a versatile energy storage device.
Arkaprava Das, Camille Latouche, Stephane Jobic, Eric Gautron, Amina Merabet, Marcin Zajac, Akinori Shibui, Peter Krüger, Wei-Hsiang Huang, Chi-Liang Chen,et al.
Elsevier BV
Ashutosh Kumar, Akhilananda Kumar, Asokan Kandasami, and Vijay Raj Singh
Springer Science and Business Media LLC
R.B. Sonpir, D.V. Dake, N.D. Raskar, V.A. Mane, K. Asokan, U. Deshpande, M. Vasundhara, and B.N. Dole
Elsevier BV
Karthikeyan Kandhasamy, Matheswaran Palanisamy, Shankar Hari, Shradha Suman, Kamatchi Jothiramalingam Sankaran, Pandiyarasan Veluswamy, Gokul Bangaru, and Asokan Kandhasami
Elsevier BV
A. Kumar, T. Ghosh, Z. Aabdin, J. Roy, V. K. Verma, A. Ghosh, S. K. Sahoo, R. Urkude, S. Bhunia, U. K. Goutam,et al.
AIP Publishing
Spintronics-based studies have produced significant attention in the last decade while claiming the observation of room temperature ferromagnetism (RTFM). Nevertheless, there is a lack of consensus on a mechanism responsible for this phenomenon. In this study, we focus on Cu-doped ZnO (ZCO) to understand the microscopic origin of RTFM and the role of different oxidation states of Cu in RTFM. We have performed different spectroscopic techniques using synchrotron facilities. The values of spin-moment obtained from x-ray magnetic circular dichroism sum-rule truly exhibit a ferromagnetic interaction in the nanocrystalline powder of ZCO with ∼0.58 μB for 5% of Cu concentration in the total fluorescence yield mode. Such an enhanced magnetization is attributed to the presence of Cu2+, which is mainly localized in the bulk region. Cu in ZCO is mostly dominated by the presence of Cu2+. This is clearly reflected by the profiles of x-ray photoemission spectroscopy. Consequently, the weakly magnetized total electron yield mode is attributed to a state of magnetic frustration as the majority of Cu3+ is found on the surface. Some of these Cu3+ when come in the vicinity of Cu2+ ions result in a highly correlated state of double exchange mechanism, which is the microscopic origin of RTFM in ZCO. The coupling between Cu2+-Cu3+ is mediated via oxygen vacancies (VO), the presence of which is confirmed through the features of electron energy loss spectroscopy over different edges. The confirmation of VO is also supported by the deconvolution of E2high-phonon in the Raman spectra. Moreover, the defects in the local electronic structures of ZCO are demonstrated by the deconvoluted spectra of Cu L3 x-ray absorption spectroscopy. The images obtained from high-resolution transmission electron microscopy confirm the incorporation of Cu into the wurtzite crystal of ZnO. A clear enhancement in magnetization upon an increase in carriers of Cu in ZCO indicates carrier-induced ferromagnetism. Cu2+ and VO are the two attributes of RTFM in ZCO.
Akanksha Motla, Thanigai Arul Kumaravelu, Chung-Li Dong, Chi-Liang Chen, K. Asokan, and S. Annapoorni
Springer Science and Business Media LLC
Bhargav Rajyaguru, Keval Gadani, M.J. Keshvani, Davit Dhruv, A.D. Joshi, K. Asokan, R.J. Choudhary, D.M. Phase, N.A. Shah, and P.S. Solanki
Elsevier BV
Akanksha Motla, Thanigai Arul Kumaravelu, Chung-Li Dong, Asokan Kandasami, Devesh Kumar Avasthi, and S. Annapoorni
Springer Science and Business Media LLC
P. Jeya, L. Kungumadevi, R. Yuvakkumar, G. Ravi, Kandasami Asokan, T.S. Senthil, Saju Subin, and Sagadevan Suresh
Elsevier BV
Suniksha Gupta, Smita Howlader, K. Asokan, M. K. Banerjee, and K. Sachdev
Springer Science and Business Media LLC
Arkaprava Das, Marcin Zajac, Wei-Hsiang Huang, Chi-Liang Chen, Asokan Kandasami, Fabienne Delaunois, Xavier Noirfalise, and Carla Bittencourt
IOP Publishing
Abstract This study thoroughly examines the collective influence of compositional variation and annealing temperature on the electronic structure of sol–gel derived NixZn1−xO (x = 0 to 1) thin films annealed at different temperatures (700 ° C, 800 ° C, and 900 ° C) using x-ray photoelectron spectroscopy (XPS) and x-ray absorption spectroscopy. A gradual structural phase transition from hexagonal wurtzite ZnO to cubic rocksalt NiO with increasing Ni concentration was revealed by x-ray diffraction (XRD). Grain growth was observed from scanning electron microscopy with increasing annealing temperature. Photoluminescence measurements indicate the presence of interstitial oxygen when Ni atoms are incorporated in the film. The Ni L 3,2 absorption edge shows an intensity enhancement in the white-line feature with increasing Ni concentration, evidencing the presence of higher oxidation states. Concurring results were observed by XPS where both Ni2+ and Ni3+ free ion multiplets are present in the Ni 2p core level spectrum for 20% and higher Ni concentration. O K and Zn L 3,2 XAS spectra demonstrated the e g-t 2g sub-band splitting at higher Ni concentration, triggered by band anti-crossing interaction and crystal field splitting. The extended x-ray absorption fine structure (EXAFS) simulation for the Zn K edge revealed a Zn–Zn/Ni bond length change for 60% Ni concentration. The thermal disorder factor increased up to 40% Ni concentration, and beyond that, it decreased due to stable NiO phase dominance in the alloy composite. Ni K edge EXAFS fitting indicated an insignificant change in the Ni-O and Ni–Ni/Zn bond lengths throughout the range of varying Ni concentrations. The thermal disorder factor increases with increasing annealing temperature, indicating a more disordered lattice. Such investigation is essential where the electronic properties of nanometer-sized materials determine the performance of functional devices. The present work critically elucidates the combined impact of compositional variations and annealing temperatures on electronic structures.
Rashmi Kajal, Asokan Kandasami, Indra Sulania, and Devendra Mohan
Springer Science and Business Media LLC
Chetan Awasthi, R. Meena, Asokan Kandasami, and S.S. Islam
Elsevier BV
Jeya P, Keerthana SP, L. Kungumadevi, Yuvakkumar Rathinam, Ravi Ganesan, Asokan Kandasami, and T. S. Senthil
American Chemical Society (ACS)
Photocatalysts based on semiconducting chalcogenides due to their adaptable physio-chemical characteristics are attracting attention. In this work, Bi-doped PbS (henceforth PbS:Bi) was prepared using a straightforward chemical precipitation approach, and the influence of γ-irradiation on PbS’s photocatalytic ability was investigated. Synthesized samples were confirmed structurally and chemically. Pb(1–x)BixS (x = 0, 0.005, 0.01, 0.02) samples that were exposed to gamma rays showed fine-tuning of the optical bandgap for better photocatalytic action beneath visible light. The photocatalytic degradation rate of the irradiated Pb0.995Bi0.005S sample was found to be 1.16 times above that of pure PbS. This is due to the occupancy of Bi3+ ions at surface lattice sites as a result of their lower concentration in PbS, which effectively increases interface electron transport and the annealing impact of gamma irradiation. Scavenger tests show that holes are active species responsible for deterioration of the methylene blue. The irradiated PbS:Bi demonstrated high stability after being used repeatedly for photocatalytic degradation.