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, 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
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
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.
Monica Susai Mary S., S. Malathi, Sudha Varadharaj, K. Thanigai Arul, Rama Shanker Verma, J. Ramana Ramya, K. Asokan, J.B.M. Krishna, S. Narayana Kalkura, and Moorthy Babu S.
Elsevier BV
D. V. Dake, N. D. Raskar, V. A. Mane, R. B. Sonpir, E. Stathatos, M. Vasundhara, R. Meena, K. Asokan, and B. N. Dole
Springer Science and Business Media LLC
AbstractSuperparamagnetic N-doped graphene oxide (GO)- with ZnS nanowires was synthesized by a one-step hydrothermal method by doping dilute amounts of Ga, Cr, In, and Al ions for water treatment and biomedical applications. In these experiments, to enhance their properties, 2% of Ga3+, In3+, and or Al3+ were codoped along with 2% Cr ions in these ZnS nanowires. The nanocomposite with the composition, In0.02Cr0.02Zn0.96S, has better photocatalytic efficiency than other co-doped nanocomposites. The In (metalloids) and Cr (transition metal ion) are the best combinations to increase the magnetic properties which are beneficial for photocatalytic activity. Synthesized nanocomposite materials were characterized by several techniques such as X-ray diffraction, Field emission-scanning electron microscope (FESEM) with EDAX, vibrating sample magnetometer (VSM), UV–Vis, X-ray photoelectron spectroscopy (XPS), and fluorescence spectroscopy. The correlation of intriguing magnetic properties with their photocatalytic properties is also discussed. XPS was employed for the detection of surface defects, phase transformation, and the nature of chemical components present in the nanocomposites. The Frankel and substitutional defects have a direct impact on photocatalytic activity that was determined from the fluorescence (FL) spectroscopy. FL and XPS reveal that the Cr and In codoped composite has a higher percentage of defects hence its photocatalytic efficiency reaches 94.21%.
J. Ramana Ramya, K. Thanigai Arul, K. Asokan, J. Gajendiran, Chung-Li Dong, and R. Ilangovan
Elsevier BV
Kurinjinathan Panneerselvam, Anita R Warrier, Thileep Kumar K, Roselin Ranjitha Mathiarasu, Raghu Subashchandrabose, Yu-Cheng Huang, Thanigai Arul Kumaravelu, Chung-Li Dong, Asokan Kandasami, and Ramana Ramya Jayapalan
Elsevier BV
Alageshwaramoorthy Krishnaprasanth, Pandian Mannu, Seetha Mahalingam, Dhanaprabhu Pattappan, Asokan Kandasami, Yi-Ting Lai, Yoshitake Masuda, Han-Wei Chang, Mei-Yu Chen, Ping-Hung Yeh,et al.
Elsevier BV
A. Kumari, W.W. Tjiu, Z. Aabdin, J. Roy, V.K. Verma, A. Kandasami, and V.R. Singh
Elsevier BV
Riya Dawn, Weng Weei Tjiu, Zainul Aabdin, Ferry Faizal, Camellia Panatarani, I Made Joni, Waseem Akhtar, Kundan Kumar, Ariful Rahaman, Girish Chandra,et al.
American Chemical Society (ACS)
In this study, magnetic Fe3O4 nanoparticles (NPs) were dispersed uniformly by varying the thickness of the SiO2 coating, and their electronic and magnetic properties were investigated. X-ray diffraction confirmed the structural configuration of monophase inverse-spinel Fe3O4 NPs in nanometer size. Scanning electron microscopy revealed the formation of proper nonporous crystallite particles with a clear core-shell structure with silica on the surface of Fe3O4 NPs. The absorption mechanism studied through the zeta potential indicates that SiO2-coated Fe3O4 nanocomposites (SiO2@Fe3O4 NCs) possess electrostatic interactions to control their agglomeration in stabilizing suspensions by providing a protective shield of amorphous SiO2 on the oxide surface. High-resolution transmission electron microscopy images demonstrate a spherical morphology having an average grain diameter of ∼11-17 nm with increasing thickness of SiO2 coating with the addition of a quantitative presence and proportion of elements determined through elemental mapping and electron energy loss spectroscopy studies. Synchrotron-based element-specific soft X-ray absorption spectroscopy and X-ray magnetic circular dichroism (XMCD) techniques have been involved in the bulk-sensitive total fluorescence yield mode to understand the origin of magnetization in SiO2@Fe3O4 NCs. The magnetization hysteresis of Fe3O4 was determined by XMCD. At room temperature, the magnetic coercivity (Hc) is as high as 1 T, which is about 2 times more than the value of the thin film and about 5 times more pronounced than that of NPs. For noninteracting single-domain NPs with the Hc spread from 1 to 3 T, the Stoner-Wohlfarth model provided an intriguing explanation for the hysteresis curve. These curves determine the different components of Fe oxides present in the samples that derive the remnant magnetization involved in each oxidation state of Fe and clarify which Fe component is responsible for the resultant magnetism and magnetocrystalline anisotropy based on noninteracting single-domain particles.
G. Sriramulu, K. Praveena, B. Ravinder Reddy, Asokan Kandasami, and S. Katlakunta
Elsevier BV