Qualification: 
Ph.D, MPhil
ks_rajani@cb.amrita.edu

Dr. K. S. Rajni did her M. Phil from Bharathiar University, India and completed her Doctoral dissertation in Physics from Bharathiyar University, India.

Her M. Phil. work was based on Characterization of CdS Thin Films Prepared by Spray Pyrolysis Technique. Her doctoral studies were focused on Preparation of Photo Electro Chemical (PEC) Cells based on CdSe, InSe Doped CdSe and ZnSe Doped CdSe Thin Films by Electron Beam Evaporation Technique.

Dr. Rajni is guiding a number of undergraduate & postgraduate student projects and Ph. D. research scholars. She currently researches on Dye Sensitized Solar Cell using Naturally Available Organic Materials as Sensitiser.

She is involved in the project titled, Developing Nano Electrodes and Membrane for Direct Methanol and Ethanol Fuel Cells – Preliminary Studies.

Affiliation(s):

  • Associate Professor, Department of Sciences, Amrita School of Engineering, Amrita Vishwa Vidyapeetham, Coimbatore – 641 112, Tamil Nadu, India

Qualification

Year Degree/Program Institution
2010 Ph. D Bharathiar University
1991 M. Phil Bharathiar University
1990 M. Sc Kongunadu Arts and Science College
1988 B. Sc PSGR Krishnammal College for Women

Research Interest

  • Area of Interest
    • Interest 1: Synthesis and Characterisation of Nanomaterials
    • Interest 2: Thin Film Solar Cells and Dye Sensitized Solar Cells Applications
    • Interest 3: Super Capacitor Applications
  • Keywords
    • Nanomaterials
    • Solar Cells
    • DSSC
    • Super Capacitors

Research Group

Present Team: Ph. D Scholars

G. Kiruthiga Prabhu
Research Interest: Dye Sensitized Solar Cells

 

T. Raguram
Research Interest: Dye Sensitized Solar Cells, Photocatalytic and Magnetic Applications

D. Pughal Selvi
Research Interest: Super Capacitor Applications

 

Past Team: Ph. D Scholars

  • Name: Baskar

Teaching

  • UG Theory:
    • B.Tech -Engineering Physics,Concepts of nanophysics and nanotechnology
    • M.Sc integrated Physics-Digital electronics,Solid state physics ,Concepts of nanophysics and nanotechnology
  • PG/Ph.D Theory
    • M.Sc integrated -Physics-Thin film Technology
    • Ph.D-Physics of Nanomaterials
  • UG Labs
    • B.Tech-First year B.Tech-Engineering physics Lab I and II

Workshops Attended

  • Participated in Bhabha Atomic Research Centre (BARC) sponsored two day workshop on Macro-Nanotechnology for societal cause conducted by PSG Institute of Advanced Studies, Coimbatore during October 4 - 5, 2012.
  • Attended DST sponsored two day national workshop on Exigent Apprehensions in Scaling up & Stacking Fuel Cells, during June 22 - 23, 2012 at Department of Automobile Engineering, PSG College of Technology, Coimbatore.
  • Participated in DST PURSE sponsored national workshop on Advanced Instruments for Characterization at Department of Nanosciences and Technology, Bharathiyar University, Coimbatore.
  • Attended in DAE-BRANS theme meeting on Materials Chemistry (TMMC-2012), UGC-DAE CSR during Feb 13 – 15, 2012 at Kalpakkam,Tamil Nadu.
  • Attended a two day workshop on Fuel Cell Technology at National Institute of Technology, Calicut, Kerala during June 11- 12, 2011.
  • Participated in fifth NIAS- DST workshop on Nano Technology: Dimensions of Nano Science, Nano Technology & Society for Women Scientists & Technologists during Dec 14 - 18, 2009 at National Institute of Advanced Studies, Bangalore.

Publications

Publication Type: Journal Article

Year of Publication Title

2020

R. T. D and Dr. Rajni K. S., “Characterization of TiO2 photoanodes and natural dyes (Allamanda Blanchetti and Allamanda Cathartica) extract as sensitizers for dye-sensitized solar cell applications”, Journal of Sol-Gel Science and Technology, vol. 93, 2020.[Abstract]


In the present work, Dye-Sensitized Solar Cells (DSSC) were fabricated using fabricated TiO2 photoanodes and natural dyes (Allamanda Blanchetti (AB) and Allamanda Cathartica (AC)) as the sensitizers. Initially, TiO2 nanoparticles were synthesized by sol–gel technique and a thin film of TiO2 was formed on the FTO substrate by Doctor Blade technique. Then, they were annealed at 400, 500, and 600 °C to act as the photoanode. X-ray diffraction analysis shows the prepared samples have tetragonal crystal structure with anatase and rutile phase. The average crystallite size was found to be 10–17 nm when the annealing temperature (TA) was increased from 400 to 600 °C. From UV–DRS analysis, the percentage of reflectance was found to starts at 315 nm. The bandgap analysis shows the transitions were indirect allowed and the bandgap value decreases from 3.6 to 2.8 eV when the TA increases from 400 to 600 °C. From the optical absorption spectra, the absorption of dye and dye-sensitized TiO2 was found to be in the visible region. From PL analysis, the emission peak intensity of Ti⁴⁺ was increasing with decrease in oxygen (O2⁻) vacancies with TA increases from 400 to 600 °C was noted. FESEM analysis shows the synthesized particles were spherical and from EDS the presence of Ti and O was confirmed. From FTIR analysis, the functional groups presented in the prepared extracts were confirmed. The Efficiency of DSSC was found to be 1.16 and 0.30% for AB sensitized TiO2 (400 °C) and AC sensitized TiO2 (400 °C) as photoanodes. From Electrochemical Impedance Spectroscopic (EIS) analysis, DSSC with AB + TiO2 shows low charge transfer resistance compared with AC + TiO2.

More »»

2020

K. M. Aiswarya, Raguram, T., and Dr. Rajni K. S., “Synthesis and characterisation of nickel cobalt sulfide nanoparticles by the solvothermal method for dye-sensitized solar cell applications”, Polyhedron, vol. 176, p. 114267, 2020.[Abstract]


The aims of this study were to synthesize and characterize a nickel cobalt sulfide (NiCo2S4), namely a ternary transition metal sulfide, by the solvothermal method for DSSC applications. Four samples of NiCo2S4 nanoparticles (NCS1, NCS2, NCS3 and NCS4) were synthesized by varying the amount of thiourea used in the synthesis. The samples were found to have an average crystallite size of 3 nm. The FE-SEM images of the samples show the particles to have uniform spherical shape, with agglomeration into clusters in some places. The presence of Co, Ni and S was confirmed through EDS analysis. From the fingerprint region of the FTIR spectra, the presence of sulfur was confirmed. A peak at 672 cm−1 was observed in the Raman spectra which matches the reported value of 678 cm−1, confirming the formation of NiCo2S4 nanoparticles. The efficiencies of the DSSCs fabricated with NCS2, NCS3 and NCS4 were found to be 0.87, 1.54 and 1.87%. From the results it is concluded that NiCo2S4 can be a candidate for use as a counter electrode in DSSC applications.

More »»

2020

T. Raguram and Dr. Rajni K. S., “Effects of varying the soaking duration of Eosin Blue sensitized TiO2 photoanodes for dye-sensitized solar cells”, Optik, vol. 204, p. 164169, 2020.[Abstract]


In the present work, Dye-sensitized solar cells (DSSCs) are fabricated using synthesized TiO2 nanoparticles as photoanode and organic synthetic dye (Eosin Blue (EB)) as a sensitizer. The soaking duration of TiO2 photoanodes in EB dye are varied [24 h (S1), 36 h (S2), 48 h (S3), and 60 h (S4)] and the efficiency is calculated. From XRD, the synthesized TiO2 nanoparticles show a tetragonal crystal structure with anatase and rutile phase and it is confirmed by micro-Raman analysis. The average crystallite size is found to be ∼8 nm and it is confirmed by TEM. BET analysis shows that the specific surface area of the sample is 147.128 m2 g−1. From FTIR, the strongest peak observed at 460 cm−1 confirms the bending vibrations of Ti-O. The thermal decomposition and the phase transitions of synthesized TiO2 nanoparticles are analyzed by TGA. From UV–vis studies, the optical absorption of EB sensitized TiO2 is red-shifted. From the PL analysis, the excitonic emission band is observed at 376 nm and the oxygen vacancies are observed at 414, 465 and 530 nm. From J-V characteristics, maximum efficiency of 2.3 % is observed for DSSC fabricated with TiO2 photoanode sensitized with EB dye at the soaking duration of 48 h (S3).

More »»

2020

A. Dharr, Arjun, A., Raguram, T., and Dr. Rajni K. S., “Influence of pH on the structural, spectral, optical, morphological and photocatalytic properties of ZrO2 nanoparticles synthesized by sol–gel technique”, Journal of Materials Science: Materials in Electronics, vol. 31, no. 18, pp. 15718 - 15730, 2020.[Abstract]


In the present work, ZrO2 nanoparticles are synthesized with different pH (3 to 8) by the sol–gel technique. From X-ray diffraction analysis, the synthesized particles show a tetragonal crystal structure, and the average crystallite size is found to vary from 7.35 to 4.7 nm as the pH increases from 3 to 8. From the FTIR analysis, the peak observed at 621 cm−1 is ascribed to Zr–O vibrations in the nano-tetragonal ZrO2. The bandgap values are found to increase from 2.0 to 2.9 eV with an increase in pH. From the PL analysis, the observed peaks show a large band and considerable red shift in the band maximum compared to the bandgap of bulk ZrO2. This strongly expresses that the fluorescence involves extrinsic states. From the morphological analysis, the synthesized nanoparticles are found to be spherical in shape and EDS results confirm the presence of Zr and O. The photocatalytic analysis carried out using Alizarin yellow dye, shows that the degradation efficiency is 84.04% for ZrO2 (S3-pH 6). This is attributed to the excess –OH group present on the surface of ZrO2.

More »»

2020

S. Vedavarshni, Raguram, T., and Dr. Rajni K. S., “Studies on the characteristics of TiO2 photoanode and flavanol pigment as a sensitiser for DSSC applications”, Pramana - J Phys, vol. 94, 2020.[Abstract]


In the present work, dye-sensitised solar cell (DSSC) is fabricated using natural dye (Tecoma Stans)-
sensitised TiO2 as the photoanode, platinum as the counter electrode and lithium iodide and iodine as the electrolyte.
Initially, TiO2 nanoparticles are synthesised by the sol–gel technique using glacial acetic acid as the hydrolysing
agent. The photoanodes are prepared by the Doctor Blade technique using the synthesised nanoparticles coated onto
the fluorine-doped tin oxide (FTO) substrate and annealed at 400, 500 and 600◦C for 30 min. Structural analysis
shows the anatase phase of the TiO2 thin film with a tetragonal crystal structure. The optical transmittance is found
to be around 95% with an optical band gap close to 3.1 eV and increases with an increase in annealing temperature.
From the PL emission spectra, the excitation of the titania band is observed. The pigment flavan-4-ol which acts as
a sensitiser is extracted from Tecoma Stans flower. From the absorption study of the pigment, the active region of
radiation and the band gap are found to be around 550 nm and 2 eV respectively. FTIR analysis of the pigment shows
a stable structure similar to that of the prepared photoanodes. CV analysis of the sensitiser shows maximum oxidation
within the active region. Field emission scanning electron microscope (FE-SEM) analysis shows that the prepared
photoanode (600◦C) has spherical shape. The overall photoconversion efficiency of Tecoma Stans-sensitised TiO2
photoanode is 0.4491%.

More »»

2020

P. Arun, Raguram, T., P Menon, M., Sajna, P. J., and Dr. Rajni K. S., “Synthesis and characterization of microwave-assisted TiO2 nanoparticles for dye-sensitized solar cell application”, Optoelectronics and Advanced Materials - Rapid Communications, vol. 14, pp. 445-451 , 2020.[Abstract]


Titanium dioxide nanostructures are the most widely used photocatalysts among all photocatalytic compounds, because TiO2 is inexpensive, biologically and chemically stable, and corrosion-resistive. In this study, we have developed a fast technique for the synthesis of TiO2 nanowires via a facile microwave-assisted hydrothermal process. Moreover, the structure and optical properties of the produced photocatalysis were characterized using X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Energy and Dispersive X-ray Spectroscopy (EDXS) measurements. Finally, we tested the applicability of photocatalysis TiO2 nanorods prepared as an antibacterial. The SEM, EDX, TEM and XRD analysis indicated that photocatalysts TiO2 nanorods are crystalline. Moreover, photocatalysts TiO2 nanorods by using water as a solvent via a facile microwave-assisted hydrothermal process were prepared in this work for the first time. The antibacterial activity of TiO2 nanoparticles was tested against E. coli ATCC® 8739™. The viable bacteria were monitored by counting the number of colony forming units (CFUs). The results revealed a significant reduction (p<0.05) in the number of CFUs/ ml after only 30 min of exposure to TiO2 nanoparticles. There was a significant difference between the number of CFUs/ml after 0 min exposure to TiO2 nanoparticles and the number of CFUs/ml after 30 min exposure. A growth inhibition of three orders of magnitude is observed after only 30 min of exposing E. coli to TiO2 nanoparticles. Further, a significant decrease (p<0.05) is observed in the number of CFUs/ml for E. coli after 24 h exposure to TiO2 nanoparticles. Taken together these results show superior antibacterial activity for TiO2 nanoparticles against pathogenic bacteria, which demonstrates potential applications in medical and biomedical fields. Finally, the one outstanding feature of this study is that we need more experimental work under different growth conditions to which we could demonstrate that photocatalysts metal oxide nanostructures are promising for important applications in water purification.

More »»

2020

A. Arjun, Dharr, A., Raguram, T., and Dr. Rajni K. S., “Study of Copper Doped Zirconium Dioxide Nanoparticles Synthesized via Sol–Gel Technique for Photocatalytic Applications”, vol. 30, no. 12, pp. 4989 - 4998, 2020.[Abstract]


In the present work, undoped and Cu-doped ZrO2 nanoparticles with a different weight percentage of copper (0 to 0.05 wt%) are synthesized by sol–gel technique. From XRD analysis, the observed peaks corresponding to the plane match well with the JCPDS data of tetragonal ZrO2. Microstructural analysis shows that the average crystallite size decreases from 6.96 to 5.73 nm when the Cu content increases from 0 to 0.05 wt%. From FTIR analysis the peaks observed at 489 and 429 cm−1 confirm the tetragonal Zirconia. From the morphology, the shape of the synthesized nanoparticles is observed to be spherical and the average particle size (using ImageJ) is found to vary from 30 to 7.18 nm when the dopant concentration increases from 0 to 0.05 wt%. The presence of Zr, Cu, and O in the prepared samples are confirmed by EDS analysis. The optical analysis shows that the optical absorption is blue-shifted when Cu content increases from 0 to 0.05 wt% and it is attributed to the confinement of charge carriers. Bandgap (Eg) analysis shows the transitions are direct allowed and the Eg value increases from 3. 27 to 3. 35 eV when Cu content increases from 0 to 0.05 wt%. From PL analysis, the peak at 389 nm is attributed to the ionized oxygen vacancies (F and F centers) from CB. From the photocatalytic analysis, undoped and Cu-doped ZrO2 used as the catalyst for the degradation of Alizarin Yellow is found to be faster for 0.05 wt% of Cu-doped ZrO2 (S3) than undoped (S1) and 0.03 wt% of Cu-ZrO2 (S2) which is attributed to the crystallite size of the 0.05 wt% of Cu-doped ZrO2 nanoparticles.

More »»

2019

T. Raguram and Dr. Rajni K. S., “Synthesis and analysing the structural, optical, morphological, photocatalytic and magnetic properties of TiO 2 and doped (Ni and Cu) TiO 2 nanoparticles by sol–gel technique”, Applied Physics A: Materials Science and Processing, vol. 125, 2019.[Abstract]


In the present work, Ni 2+ and Cu 2+ ions are doped with TiO 2 using sol–gel technique. The effects of Ni and Cu doping in TiO 2 matrix are characterized by XRD, Micro-Raman, FTIR, UV–DRS, PL, and FESEM with EDS. Furthermore, it is analyzed for photocatalytic activity and magnetic applications. From XRD analysis, it is observed that the peaks corresponding to the planes match with the JCPDS data [anatase: 89-4203] of TiO 2 . The crystallite size of the doped samples is found to be greater than that of TiO 2 . Micro-Raman analysis shows the confirmation of anatase phase of TiO 2 . FTIR analysis confirms the presence of functional groups which are presented in the prepared samples. From UV–DRS, the band-gap values of TiO 2 and doped TiO 2 (Ni 2+ , Cu 2+ ) are found to be 3.25, 2.48, and 1.25 eV. Photoluminescence (PL) results show an emission edge of Ni- and Cu-doped TiO 2 is red shifted which is due to the vacancies of titanium and oxygen imported subsequently during doping. The surface morphology and the elemental composition of Ni- and Cu-doped TiO 2 nanoparticles are also analyzed. The photocatalytic activity of all the prepared samples are assessed by methylene blue dye as testing pollutant and visible radiation. The test reveals that Cu–TiO 2 , Ni–TiO 2 , and TiO 2 show the degradation efficiency of 68.14, 61.04, and 33.32%, thereby showing that the doped TiO 2 are more efficient in degrading the pollutant and can be applied for future photocatalytic applications. From VSM analysis, the saturation magnetization of Ni–TiO 2 and Cu–TiO 2 is found to be weak and can be improved by the synthesis process and the proportion of dopant. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature.

More »»

2019

G. S. Kumar, Raguram, T., and Dr. Rajni K. S., “Synthesis and Characterization of Nickel-Substituted Cobalt Ferrite Nanoparticles Using Sol–Gel Auto-combustion Method”, Journal of Superconductivity and Novel Magnetism, 2019.[Abstract]


In the present work, Co1−xNixFe2O4 (x = 0.02, 0.04, and 0.06 M) is prepared by sol–gel auto-combustion method and its structural, functional, magnetic, and morphological characteristics are analyzed. The peaks corresponding to the plane observed from XRD matches with JCPDS data of CoFe2O4 (22-1086) and NiFe2O4 (10-0325). It is noted that the average crystallite size decreases from 31 to 27 nm when the nickel concentration increases from 0.02 to 0.06 M, indicative of the incorporation of Ni2+ ion in the cobalt ferrite lattice. FTIR analysis shows the presence of M⇔ O vibration at the tetrahedral and octahedral sites. Micro - Raman spectroscopy shows the stretching vibrations at 486.87 cm− 1 (Eg) and 696.96 cm− 1 (A1g), which are the characteristic vibrations of spinel ferrites. Magnetic studies show the variation in saturation magnetization (MS = 20.25, 9.41, 18.5 emu/g.) and coercivity (HC = 746.06, 953.03, 885.59 Oe) when the concentration of Ni2+ ion increases from 0.02 to 0.06 M. The prepared nanoparticles show a ferromagnetic nature which is attributed to the creation of an antiparallel spin and the magnetic moment created by the cation at tetrahedral and octahedral sites. The surface morphology of samples is imaged by a field emission scanning electron microscope. © 2018, Springer Science+Business Media, LLC, part of Springer Nature.

More »»

2016

R. T. D, Dr. Rajni K. S., Shanmugam, P., and Selvakumar, M., “Synthesis and characterisation of undoped and methyl orange (dye) doped L-alanine acetate single crystal”, Int. J. of ChemTech Research, vol. 9, pp. 678-687, 2016.[Abstract]


The potential application of amino acid crystals, used in NLO applications leads to intensive investigation about the material. In the present work, L-alanine acetate and methyl orange (dye) doped L-alanine acetate crystal was grown by slow evaporation method. The samples were synthesized and purified by repeated re-crystallization process and the solubility of the sample was found at different temperatures. The cell parameters were calculated using Powder X-ray diffraction analysis and the functional groups were identified using the Fourier Transforms Infra-Red Spectroscopic (FTIR) studies. From UV-Vis-NIR spectral study, it is noted that the transmission in the lower cut-off wave length, reflecting the good transmittance property of the crystal in the entire visible region. The optical emission bands were estimated by the Photoluminescence Studies. The optical band gap was also calculated for the grown crystal. NLO property of the crystal is confirmed by Kurtz-Perry powder technique. The mechanical properties such as hardness value, yield strength and stiffness constant were estimated by the Vicker’s Microhardness measurement. EDS analysis shows the elements present in the grown samples. From TG/DTA analysis, the decomposition point for methyl orange doped L-alanine acetate crystal is found to be at 2900 C which shows more thermal stability compared to that of undoped L-alanine acetate crystal.

More »»

2016

Ta Baskar and Dr. Rajni K. S., “Effect of different sulfur concentration on structural and magnetic properties of electrodeposited NiCoS magnetic thin films”, International Journal of ChemTech Research, vol. 9, pp. 317-324, 2016.[Abstract]


Nano crystalline NiCoS alloy thin films were deposited on the copper substrate with different concentration of Sulfur by electrodeposition method. Electro deposited NiCoS thin films were subjected to the structural, mechanical and magnetic characterization analysis. The chemical composition of the coated films was analyzed by EDAX. The surface and structural morphology of the coated film were analyzed by using SEM and XRD. The mechanical properties of NiCoS films have been studied by VHT. The magnetic properties of thin films have been analyzed by VSM. The electroplated NiCoS thin films were strongly adherent to the copper substrate.The SEM pictures of NiCoS thin films shows that the deposits of thin films are crack free, uniform and bright surface with fine grain size. All the electro deposited NiCoS films exhibit FCC crystalline structure with crystalline size in the order of nano scale. The VSM result of NiCoS thin films shows that the NiCoS thin films coated withhigh concentration of sulfur have highest saturation magnetisation value with lower coercivity. Due to highest magnetisation value with low coercivity, NiCoS thin films can be used for the manufacturing of MEMS and NEMS devices. © 2016, Sphinx Knowledge House. All rights reserved.

More »»

2015

Ta Baskar and Dr. Rajni K. S., “Effect of bath temperature on structural and magnetic properties of electrodeposited NiCoS magnetic thin films”, International Journal of ChemTech Research, vol. 8, pp. 234-239, 2015.[Abstract]


Nano crystalline Ni-Co-S alloy thin films were deposited on the copper substrate at different temperature by electrodeposition method. Electro deposited Ni-Co-S thin films were subjected to the structural, mechanical and magnetic characterization analysis. The chemical composition of the coated films was analysed by EDAX. The surface and structural morphology of the coated film were analyzed by using SEM and XRD. The mechanical properties of NiCoS films have been studied by VHT. The magnetic properties of thin films have been analysed by VSM. The electroplated NiCoS thin films were strongly adherent to the copper substrate The SEM pictures of NiCoS thin films show that, the deposits of thin films are crack free, uniform and bright surface with fine grain size. All the electro deposited Ni-Co-S films exhibit FCC crystalline structure with crystalline size in the order of nano scale. The VSM result of NiCoS thin films shows that the NiCoS thin films coated at high bath temperature have highest saturation magnetisation value with lower coercivity. Due to highest magnetisation value with low coercivity, NiCoS thin films can be used for the manufacturing of MEMS and NEMS devices. © 2015, Sphinx Knowledge House. All rights reserved.

More »»

2014

Dr. Rajni K. S., “Studies on the structural and conduction mechanism (ac) in thermally evaporated CdSe thin films”, International Journal of ChemTech Research, vol. 7, pp. 1509-1515, 2014.[Abstract]


In the present work, the structural properties of thermally evaporated CdSe films prepared at different thicknesses has been undertaken and the conduction mechanism is studied for the film of thickness 100nm. It is noted from the result that, all the films prepared at room temperature are poly crystalline and the peak oriented towards (002) plane and the peak corresponding to (103) plane begins to emerge when the thickness increases. From the analysis of the ac conductance mechanism, it is noted that it varies according to the relation Gp α ωn and‘n’ is found to vary depending on the frequency and temperature range studied, which suggests that the conduction mechanism in CdSe thin films are by means of hopping.

More »»

2014

S. S, D., A., C., G., P., S., Dr. Rajni K. S., and Ramachandran T., “Fabrication And Optimization Of Parameters For Dye Sensitized Solar Cell”, International Conference on Nanomaterials for Frontier Applications and Indo-Norwegian Workshop on Advanced Materials for Solar Cell Applications (ICNFA 2013), vol. 3, pp. 1-5, 2014.[Abstract]


The interest in the dye sensitized solar cell is due to its low cost, simple preparation techniques and benign effect on the&nbsp;environment. Thin film of TiO2 deposited on FTO (Fluorine doped Tin Oxide) acts as one electrodes, platinum coated FTO acts as&nbsp;the other electrode and eosin B solution acts as the sensitizer. Lithium iodide, iodine in acetonitrile solution is used as the electrolyte. It is noted that an efficiency of 7.4% was observed for a cell with Intensity 70 lux. Also the open circuit voltage of&nbsp;0.5V, short circuit current of 150µA and a fill factor of 0.68 were observed for the cell of area 1X1 cm&nbsp;2. The experimental model&nbsp;is checked with theoretical model using MATLAB software. It is noted that the simulated values follow a pattern which closely resembles the actual values of the experiment. The effect of the aging process on the overall performance of the device was&nbsp;analyzed by means of electrochemical impedance spectroscopy. The results shows that the electrolyte-TiO2 capacitance of 20 µF&nbsp;(parallel) and the resistance of 14.74 k ohms (parallel) in series with the platinum resistance of 25.58 ohms.

More »»

2011

M. G. Syed Ah Basheer, Dr. Rajni K. S., Vidhya, V. S., Swaminathan, V., Thayumanavan, A., Murali, K. R., and Jayachandran, M., “Structural, Optical, Electrical and Luminescence Properties of Electron Beam Evaporated CdSe:In Films”, Crystal Research and Technology, vol. 46, pp. 261–266, 2011.[Abstract]


CdSe:In films were prepared by electron beam evaporation technique using CdSe and In2Se3 (purity ∼99.9%) pellets. The crystal structure of the films with and without Indium, measured by X-ray diffraction (XRD), showed a typical wurtzite structure, higher Indium doping shifts the peak angle to higher side along with the broadening of the peaks. X-ray photoelectron spectroscopy (XPS) studies indicated binding energies corresponding to 54 eV (Se3d5/2), 444 eV (In 3d5/2), 411 eV (Cd 3d3/2), (Cd 3d5/2). Atomic force microscope (AFM) studies indicated a uniform surface.The grain size decreases with increase of In doping. A decrease in the band gap was observed with increase of dopant concentration. Resistivity of the films is in the range of 10-3 Ωcm. Carrier density was in the range of 1021 cm-3 for the films. The photolumineasenec spectra (PL) spectra indicated three peaks. The peak intensity decreases as the Indium concentration increases. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

More »»

Publication Type: Conference Proceedings

Year of Publication Title

2020

K. Athira, Merin, K. T., Raguram, T., and Dr. Rajni K. S., “Synthesis and characterization of Mg doped TiO2 nanoparticles for photocatalytic applications”, Materials Today: Proceedings, vol. 33. pp. 2321-2327, 2020.[Abstract]


Undoped and Mg-doped (0.3 and 0.4 M) TiO2 nanoparticles were synthesized by the sol–gel technique. X-ray diffraction (XRD) and field emission scanning electron microscope (FESEM) were used to characterize the crystallite structure and morphology of TiO2 nanoparticles. The crystallite size varies from 8.11 to 27.17 nm when Mg content increases from 0 to 0.4 M. UV-DRS studies show the occurrence of strong blue shift and broad absorption show incorporation of Mg in TiO2 lattices. The bandgap values were found to be decreased from 3.02 to 2.87 eV when the Mg content increases from 0 to 0.4 M. From the PL analysis, the emission spectra were recorded for the prepared samples. The Ti, O and Mg were identified from the EDS spectra. Photocatalytic degradation of methyl orange was also analyzed using the synthesized nanoparticles acts as a catalyst.

More »»

2020

K. T. Merin, Athira, K., Raguram, T., and Dr. Rajni K. S., “Effect of Zinc concentration in TiO2 nanoparticles synthesized by Sol-Gel technique for Photocatalytic Applications”, Materials Today: Proceedings, vol. 33. pp. 2315-2320, 2020.[Abstract]


In the present study, we have focused on the synthesis and characterization of undoped (ZT-0) and Zinc doped TiO2 nanoparticles (ZT1-0.3 M and ZT2-0.5 M) using the sol–gel method and analyzed the photocatalytic degradation activity of methyl orange under UV irradiation. The synthesized particles were characterized by XRD, UV–Visible absorption spectra, Photoluminescence spectroscopy (PL), Micro-Raman Spectroscopy, SEM and EDS. From XRD analysis the synthesized samples showed tetragonal crystal structure with the peaks matching with the JCPDS data for anatase, rutile, and ZnO. The average crystallite size was found to vary from 27 to 3 nm when the zinc concentration increased from 0 to 0.5 M. Both anatase and rutile phases were noted in the XRD spectra of synthesized samples and it was confirmed by micro-Raman analysis. The calculated anatase and rutile ratios for the prepared samples were found to be 10:90 (ZT-0), 67:33 (ZT-1) and 58:42 (ZT-2). From the Kubelka-Munk plot, the bandgap values were found to be increased from 2.8 to 3.03 eV when Zn concentration increased from 0 to 0.5 M and this was attributed to the incorporation of metal ions into the TiO2 lattice. From PL analysis, the emission band in the blue region was due to Zn doping and it led to increased PL intensities. From SEM analysis, the synthesized particles showed a spherical shape with agglomeration at some points and from EDS the elements present in the synthesized nanoparticles were noted. From the photocatalytic studies, the efficiency of ZT-0 (94%) was much greater than that of ZT-1 (33.07%) and ZT-2 (23.18%).

More »»

2020

T. Raguram and Dr. Rajni K. S., “Influence of boron doping on the structural, spectral, optical and morphological properties of TiO2 nanoparticles synthesized by sol–gel technique for DSSC applications”, Materials Today: Proceedings, vol. 33. pp. 2110-2115, 2020.[Abstract]


In the present work, boron-doped TiO2 nanoparticles are synthesized by sol–gel technique with varying boron concentrations (0.025–0.3 M). The X-ray diffraction pattern shows the tetragonal crystal structure with the anatase phase. The average crystallite size is found to be decreased from 11.83 to 6.14 nm with increasing the boron concentration. The peak observed at 1372 cm−1 from FTIR confirms the presence of Ti – O – B vibrations. UV-DRS analysis shows the absorption edge is blue-shifted due to the incorporation of boron and the bandgap values increases from 2.95 to 3.17 eV. From PL analysis, the variation of emission edge and intensity of boron doped TiO2 nanoparticles is attributed to the subsequent doping with host lattices. The surface morphology of the synthesized particle is spherical in shape with agglomeration. DSSCs fabricated using pristine (undoped) TiO2, BT3 and BT4 photoanodes show the efficiency of 2.28%, 3.91% and 3.37%.

More »»

2019

V. K. Lakshmi, Kumar, G. S., Anugraha, A., Raguram, T., and Dr. Rajni K. S., “Structural and Magnetic Studies of Zinc Substituted Cobalt Ferrite Nanoparticles prepared by Sol–Gel Technique”, IOP Conference Series: Materials Science and Engineering, vol. 577. IOP Publishing, p. 012068, 2019.[Abstract]


All Magnetic nanoparticles are newly explored materials due to its large surface to volume ratio, smaller grain size, quantum confinement effect, large uni-axial anisotropy and superparamagnetism. In the present study, Zinc substituted cobalt ferrite nanoparticles are prepared by sol-gel auto-combustion method with copper concentration varies from 0.0 to 0.0. Structural studies are taken by XRD, it was confirmed that the sample has pure cubic spinel phase structure and the crystallite size decreases from 25nm to 15nm as the Zn content increases. Raman spectroscopy confirming the spinel structure and in the case of Co1-xZnxFe2O4, the Raman bands show a shoulder-like feature at the lower wavenumber which are Raman active bands in Fe3O4 all the tetrahedral and octahedral sites are occupied by Fe ions. From FTIR Analysis, the peak observed at 433 cm−1 and around 580 cm−1 it confirms the metal oxygen vibration at octahedral and tetrahedral site. Morphological analysis shows that the spherical sized particles with pores due to the evolution of gases during the annealing process at higher temperature. The magnetic studies reveals that as the ratio of metal nitrates increases, the coercivity and remanence decreases following a hysteresis path. By the above characterization technique we were successfully able to confirm the substitution of Zinc in the octahedral sites of cobalt ferrite.

More »»

2019

C. Amritha, Kurian, S., Raguram, T., and Dr. Rajni K. S., “Structural, Optical, Functional, Morphological and Compositional Analysis of Ni - doped TiO2 Nanofibers Prepared by Electrospinning Technique”, IOP Conference Series: Materials Science and Engineering, vol. 577. IOP Publishing, p. 012073, 2019.[Abstract]


In the present work, three different concentration of Nickel is doped with TiO2/PVA nanofibers by electrospinning method which can be used as photoanode in DSSC applications. The samples are annealed at 2000C for one hour. XRD results show the anatase phase of the prepared samples. FESEM images of different concentration of nanofibers show that diameter of nanofibers depends on the concentration of Ni. Large concentrations of nanofibers show fewer diameters of nanofibers. The EDX spectrum clearly confirmed that the TiO2 composite nanofibers are consists of nickel, titanium and oxygen elements. From UV-DRS studies, redshift is observed with the increase in dopant concentration. The transitions are direct and indirect allowed and the calculated bandgap finds to be decreasing with increase in dopant concentration. PL spectra of Ni-doped samples show less intensity, which indicates the low recombination rate and intensity decreases with increase in dopant concentration. It is concluded that Ni is doped with TiO2/PVA gives better energy conversion efficiency in DSSC compare to undoped TiO2.

More »»

2019

S. Kurian, Amrita, C., Raguram, T., and Dr. Rajni K. S., “Preparation and Characterisation of PVA$\mathplus$TiO2 Nanofiber by Electrospinning Technique”, IOP Conference Series: Materials Science and Engineering, vol. 577. IOP Publishing, p. 012077, 2019.[Abstract]


In the present work PVA+TiO2 nanofibers were prepared by electrospinning technique. Structural and Functional groups were carried out by X-Ray diffraction and FTIR technique. The optical analysis was analysed by UV-DRS and Photoluminscence studies. Morphology and compositional were characterized by FESEM and EDS analysis. From Structural analysis shows PVA+TiO2 anatase crystal structure and crystallite size are nanometers. The FTIR technique was used to find out the functional groups present in the prepared set of samples. The optical analysis shows above 70% transparency in the visible region. From the PL analysis titanium and oxygen vacancies are found to be 375 and 526 nm. FESEM analysis of the annealed samples shows the uniformity of nanofibers without any beads which is attributed to the interaction of TiO2 particles with the PVA matrix. From the compositional analysis, the atomic weight percentage of Ti and O increases with the TiO2 loading in PVA.

More »»

2019

H. Vignesh, Vishnu, V., Balakumar, P., Raguram, T., and Dr. Rajni K. S., “Structural and Magnetic properties of Cobalt Ferrite (CoFe2O4) Nanoparticles by Sol-Gel Technique using Yeast”, IOP Conference Series: Materials Science and Engineering, vol. 577. IOP Publishing, p. 012092, 2019.[Abstract]


The aim of the present work is to synthesize cobalt ferrite nanoparticles by sol-gel technique using yeast. The source culture is prepared using yeast, carbon and nitrogen. Three samples are prepared by mixing the source culture with ferric nitrate (0.2 M) and cobalt nitrate (0.15, 0.2, 0.25M) and stirred for suitable duration to get the gel. The final product is heated at 600°C to get the cobalt ferrite nanopowder. Structural analysis reveals the cubic phase of cobalt ferrite nanoparticles with the peaks corresponding to the plane (220), (311), (400), (511) and (440) matches with the PDF data. The peaks are sharp showing the crystalline nature of the prepared samples. From the microstructural parameters calculated for the prominent peak (311) shows the average crystallite size is 44 nm. The lattice constant is found to be around 8.350 Å which is close to the bulk value of cobalt ferrite nanoparticle (8.373Å). The calculated X-ray density is more than their bulk counterpart and is attributed to the formation of pores throughout the synthesis method. FTIR analysis shows the existence of functional groups within the prepared sample. EDAX analysis shows the rise in the atomic weight percentage of cobalt with increase in weight proportion of cobalt nitrate. SEM analysis shows the surface morphology of the prepared sample and the ferromagnetic behavior of the cobalt ferrite nanoparticle is observed by VSM studies.

More »»

2019

K. G Prabhu, Raguram, T., and Dr. Rajni K. S., “Annealing Effect of Magnesium Tin Oxide Thin Films Prepared by Nebulizer Spray Pyrolysis Technique for DSSC applications”, IOP Conference Series: Materials Science and Engineering, vol. 577. IOP Publishing, p. 012093, 2019.[Abstract]


In the present work, Magnesium Tin Oxide (MTO), transparent conducting oxide thin films (TCO) are prepared by Nebulizer Spray Pyrolysis Technique and the properties are compared with the available ITO substrate. Magnesium acetate (MA), Tin (II) chloride (TC) are taken in three different ratios (0.1:0.1M, 0.1:0.2M, 0.1:0.3M) and the thin films are prepared onto the glass substrate at 400°C. The prepared films were annealed at 400°C for three hours. The structural analysis show the presence of Magnesium Tin Oxide with maximum intensity showing the crystallinity of the prepare samples. Also, the peak corresponds to magnesium oxide and Tin oxides were also observed with less intensity. The crystallite size was found to be around 5 nm and the thickness of the film is found to be 0.23, 0.27 and 0.32 µm for the films prepared at MA: TC in the ration of 0.1:0.1M, 0.1:0.2M and 0.1:0.3M. The sign of bulk carrier concentration shows that the coated film is having n-type conductivity and the resistivity value is very low in the range of 7 x 10 −3Ω cm which is very close to the resistivity value of ITO (8 x10−4Ω cm). The Percentage of Transmittance is between 75 to 85% in the visible region and the band gap value is 3.8 eV. From the results, it is concluded that MTO is a Best alternative for ITO and can be used in Dye-Sensitized Solar Cell (DSSC).

More »»

2019

A. Anugraha, Lakshmi, V. K., Kumar, G. S., Raguram, T., and Dr. Rajni K. S., “Synthesis and Characterisation of Copper Substituted Cobalt Ferrite Nanoparticles by Sol-Gel Auto Combustion Route”, IOP Conference Series: Materials Science and Engineering, vol. 577. IOP Publishing, p. 012059, 2019.[Abstract]


In the present study, the structural, functional, morphological and magnetic characteristics of copper substituted cobalt ferrite nanoparticles were investigated. The samples of Co1-xCuxFe2O4 at x = 0.06, 0.08 and 0.1 M were prepared by Sol-gel auto combustion route. X-ray diffraction technique was used to confirm the phase formation and structural analysis which matches with the JCPDS Data. The average crystallite size was found to be ∼25, ∼19 and ∼18 nm for x = 0.06, 0.08 and 0.1 respectively. The Micro Raman Spectroscopy revealed the stretching vibrations at 274 cm−1, 660 cm−1, and 466 cm−1, which are characteristic of Spinel Ferrites. From the FTIR analysis, the band observed at 3457cm−1 and 1650 cm−1 is assigned to hydrogen bonded O-H group and ionic stretching of C-H bond. The band assigned at 1105 cm−1, is due to Co – O and Cu - O or Fe – O vibrations. The existence of water adsorption band and metal oxygen band confirms the existence of Co and Cu in the synthesized sample. The surface morphology of samples was imaged by the field emission scanning electron microscope. The substitution of Cu2+ in the parent systems caused a significant reduction in particle size. The compositional analysis was done, which confirmed that the concentration of copper was increased in the samples. The samples were subjected to magnetic characterization because magnetic behavior is also affected by substitution of Copper in Cobalt ferrite. Magnetic hysteresis study at room temperature confirmed the reduction in saturation magnetization (MS = 14.25 to 8.33 emu/g.) and reduction in coercivity (HC = 602.64 to 380.94 Oe) when size is reduced. As the concentration of Cu into CoFe2O4 matrix increases, particle size decreases and the saturation magnetization decreases.

More »»

2019

R. Mana, Raguram, T., and Dr. Rajni K. S., “Physical Properties of Nickel Ferrite Nanoparticles at different annealing temperature Prepared by Sol-Gel Technique”, Materials Today: Proceedings, vol. 18. pp. 1753-1759, 2019.[Abstract]


Nickel ferrite is one of the versatile and technologically important soft ferrite materials due to its typical ferromagnetic properties, low conductivity and thus lower eddy current losses, high electrochemical stability, catalytic behavior and also abundance in nature. In the present work nickel ferrite nanoparticles are synthesized by sol-gel technique using citric acid as the chelating agent. 0.2M, 0.3M and 0.4M concentration of nickel nitrate, ferric nitrate and citric acid is taken and the ratio of metal nitrate to citric acid is taken as 1:1 by volume. The final product, the gel is annealed at three different temperatures 400,600 and 800°C. XRD analysis shows the cubic spinel phase of the nickel ferrite nanoparticles and the peaks matches with the JCPDS data. Micro structural analysis calculated for the prominent peak (311) showsincreases in crystallite size from 20 – 36nm with increases in temperature. The lattice parameter and the X-ray density are found to be in the range of 8.30-8.27 Å and 5.412 -5.557 g/cm3. FTIR analysis confirms the intrinsic stretching vibrations of the M-O is found around 600 cm−1which is attributed to the vibrations of the tetrahedral sites. SEM analysis, shows the agglomeration of crystallites with increasing annealing temperature. The crystallite size calculated by image J software matches with the crystallite size calculated by Scherer formula.

More »»

2014

B. K. V, Dr. Rajni K. S., .Ramachandran, T., Biswas, S., and J, A., “Extraction And Absorption Study Of Natural Plant Dyes For Dssc”, International Conference on Sustainable Energy Technologies ICSET-2014. PSG tech, 2014.[Abstract]


The absorption spectrum of sensitizer plays an important role in the conversion efficiency of DSSC. It is noted that a minimum gap of 0.2eV from the HOMO level of TiO2 is necessary to provide the electron injection from the dye to TiO2 layer conduction band. One of the basic requirements is the dye absorption on the nonporous TiO2 layer which is indicated by VU absorption spectrum. In the present work dyes extracted from beetroot, pomegranate using water and yellow bell flower (Thanga arali) using hot water and the wavelength of light absorption is found out with UV-Vis spectrophotometer. The absorption peak was found to be
516 to 528 nm, for beetroot dye with pH ranges from 7.43 to 8.28 and 322nm for pomegranate with pH 6.99 and for yellow bell flower the peak position was found to be at 308 and 205nm. From the absorption spectrum the band gap of the dye and the extinction coefficient is also calculated.

More »»

2013

Dr. Rajni K. S., “Conduction Studies on Cadmium Selenide (CdSe) Thin Films,”, International Conference on Thin Films & Applications (ICTFA-2013) . 2013.

2012

Dr. Rajni K. S., S., V. V., and M., J., “Raman Spectroscopy Studies of Electron Beam Evaporated CdSe Films Prepared at Different Substrate Temperatures”, International conference on frontiers in materials science for Energy and Environment. Loyola College, Chennai , 2012.

2012

Dr. Rajni K. S., “Structural and Bandgap Analysis of Electron Beam Evaporated Indium Selenide Nanocrystalline Thin Film”, NanoSciTech 2012, International conference on frontiers of nanoscience, nanotechnology and their applications . 2012.

2012

Dr. Rajni K. S., S., V. V., and M., J., “Structural Investigations of CdSe and Indium Selenide Doped CdSe Films”, International Conference on Recent trends in Advanced Materials . Vellore, 2012.

2012

Dr. Rajni K. S., S., V. V., and M., J., “Cadmium Selenide (CdSe) PEC (Photo Electro Chemical) Solar Cells”, International Conference on Renewable Energy Resources for 21st Century - Challenges & Opportunities. Ettimadai, 2012.

2012

Dr. Rajni K. S., S., V. V., and M., J., “In Doped CdSe Nanocrystalline Thin Film for PEC Solar Cells”, International Conference on Nanoscience and Nanotechnology-ICREU 2012 . Mexico, 2012.

2011

Dr. Rajni K. S., S., V. V., and M., J., “Effects of Substrate Temperature on the Structural Properties of CdSe and In Doped CdSe Thin Films”, 7th international conference on MEMS NANO and Smart system. Kaulalampur, Malaysia , 2011.

2011

Dr. Rajni K. S., “Structural Investigations of Electron Beam Evaporated Indium Selenide Thin Film at Different Thicknesses”, DRDO sponsored National Conference on Recent trends in Materials Science - 2011 (NCRTMS-2011) . KS Rengasamy college of Technology, Tiruchencode , 2011.

2011

Dr. Rajni K. S., “Microstructural and Optical Investigations of Thermally Evaporated CdSe Thin Film”, International conference on Advanced Materials ICAM-2011. 2011.

2010

Dr. Rajni K. S., S., V. V., and M., J., “Nanocrystalline CdSe Thin Films Photo Electrochemical (PEC) Solar Cells”, International Workshop on Applications of Nanotechnology to Energy, Environment and Biotechnology (NANO EEB). St. Aloysius College Mangalore, 2010.

2009

Dr. Rajni K. S., S., V. V., and M., J., “Structural Properties of Electron Beam Evaporated CdSe Polycrystalline Films”, UGC Sponsored National Conference on Nanomaterial for Energy Conversion and Conservation (NMCEE'09) . Tiruchirappalli, 2009.

Publication Type: Conference Paper

Year of Publication Title

2018

R. Harsh, Srivastav, H., Balakrishnan, P., Saini, V., Senthilkumar D., Dr. Rajni K. S., and Dr. Thirumalini S., “Study of Heat Transfer Characteristics of Nanofluids in an Automotive Radiator”, in IOP Conference Series: Materials Science and Engineering, 2018, vol. 310, no. 1, p. 012117.[Abstract]


This paper presents an experimental study on heat transfer using nanofluid as coolants in engines. Previous studies shows that Al 2 O 3 is found to be more effective in heat transfer due to its high conductive property which is found to increase with concentration. Particles having diameter in the range 10 -3 to 10 -6 m have low thermal conductivities and cause clogging in the flow section along with significant friction and are highly unstable in solution. Nanoparticles on the other hand are easily dispersed and cause minimal clogging or friction in the flow. In the present work, ethylene glycol-water solution is taken as a base fluid for nanoparticle dispersion. The ratio of water to ethylene glycol used is 80:20 and it has been noted out that heat conduction improved with increasing fraction of ethylene glycol. The experiments were conducted with flow rate of 4,5,6 and 7 L/min and the air flow rate inside the duct was kept constant at 4.9 m/s. The temperature of water in the reservoir is kept at 70°C. The nanoparticles used in this experiment are Cu and TiO 2 having particle size less than 80nm. Result shows that there is an improvement of 24.5% in the overall heat transfer coefficient and there was also an increase of 13.9% in the heat transfer rate compared to the base fluid (80:20 Water: EG solution).

More »»

Invited Talks

  1. Resent Research in simulation of crystal growth and its device applications- CSIR sponsored Two day national (4 to 5 april 2019) conference on Recent Research In Simulation of Crystal Growth And its Device Applications in Industries- 4 th April 2019. P.A College of Engineering and Technology, Coimbatore -642002 Pollachi.
  2. Semiconductor nano thin films for energy applications-One day conference on Novel Materials for Energy, Engineering and Biological Applications (NMEEB'19) organized by Department of Science & Humanities, M. Kumarasamy College of Engineering, Karur on 9thApril 2019.
  3. Overview of Crystal Growth and its Device Applications-A Dazzling Gateway of Crystal Growth in Energy Applications CSIR sponsored Two day national workshop on “New Trends in Research and Modeling of Crystal Growth and Its Energy Applications”- 18 th July 2019. P.A College of Engineering And Technology, Coimbatore -642002 Pollachi
  4. Department of Science and Humanities Physics),PA, College of Engineering and Technology, Coimbatore-642002, Tamil Nadu-NANOMATERIALS FOR ENERGY APPLICATIONS09-07-2020 30-12 PM-
Faculty Research Interest: