Low Frequency Ultrasonication of Degussa P25 TiO₂ and Its Superior Photocatalytic Properties

Vijayarangamuthu, K.,Han, EunJi,Jeon, Ki-Joon American Scientific Publishers 2016 Journal of Nanoscience and Nanotechnology Vol.16 No.5

<P>We report the simple and effective method for enhancing the photocatalytic properties of Degussa P25 TiO2 by low frequency ultrasonication. The improvement in the crystallinity of ultrasonicated TiO2 was confirmed by the X-ray diffraction and Raman spectroscopy studies. Further, the X-ray photoelectron spectroscopy was utilized to study the changes in chemical nature and band edge due to the effect of ultrasonication and H2O2 solvent. The transmission electron microscope (TEM) was used to analysis the surface distortion. The Moire fringes in TEM were examined to understand the partial transformation of amorphous to crystalline anatase structure and overlapping of rutile over anatase crystal. The photocatalytic results indicated improvement in the degradation of methylene blue dye. The degradation efficiency was estimated to be 86% for ultrasonicated TiO2, which is higher as compared to 40% of P25. The rate constant values revealed four times superior degradation property of ultrasonicated TiO2. The improvement in the photocatalytic efficiency was correlated to the formation of rutile/anatase TiO2 aggregation and its consequences on electronhole recombination.</P>

Morphology Control of Zinc Oxide Nanostructure on Single Layer Graphene

Ahn, Seungbae,Vijayarangamuthu, K.,Jeon, Ki-Joon American Scientific Publishers 2016 Journal of nanoscience and nanotechnology Vol.16 No.5

<P>Various morphologies of zinc oxide (ZnO) nanostructures on single layer graphene were synthesized by electrodeposition method. The current density was utilized to control the morphology of the ZnO. The Scanning Electron Microscope (SEM) was used to examine the surface morphology of the samples. SEM analysis shows morphology changes to nanorod, flower, and flakes with increase in the current density from 0.1, 0.2, and 0.3 mA/cm(-1) respectively. The XRD, XPS, and Raman spectroscopy were adopted to characterize the ZnO nanostructure and to understand the formation of various morphologies. The Raman result clearly shows extra modes due to for flakes structure caused by c-axis orientation along the substrate direction. Further, XPS data also supports formation of ZnO without any other intermediate compound such as Zn(OH)(2). The formation of various morphologies was correlated to the formation different ratio of Zn2+ and OH- ions and the change in growth direction due to various current densities.</P>

2P-439 Control of fluorine nature on single layer graphene for future energy applications

안승배,( Kalimuthu Vijayarangamuthu ),남경목,윤상희,전기준 한국공업화학회 2017 한국공업화학회 연구논문 초록집 Vol.2017 No.0

Degussa P25 TiO₂ modified with H₂O₂ under microwave treatment to enhance photocatalytic properties

Han, Eunji,Vijayarangamuthu, K.,Youn, Jong-sang,Park, Young-Kwon,Jung, Sang-Chul,Jeon, Ki-Joon Elsevier 2018 CATALYSIS TODAY - Vol.303 No.-

<P><B>Abstract</B></P> <P>We report a facile and effective low-temperature modification method for improving the photocatalytic activity of commercial Degussa P25 TiO<SUB>2</SUB>. The method involves the microwave treatment of TiO<SUB>2</SUB> in an H<SUB>2</SUB>O<SUB>2</SUB> solution. The properties of the modified TiO<SUB>2</SUB>, including improved crystallinity, size distribution, and aggregation of the anatase/rutile phases, were analyzed by X-ray diffraction (XRD), Raman spectroscopy, and transmission electron microscope (TEM). Further, we found that Ti<SUP>3+</SUP> and Ti-OH were formed because of the presence of H<SUB>2</SUB>O<SUB>2</SUB>. Moreover, the valence band (VB) edge was determined by Raman and X-ray photoelectron spectroscopy (XPS) studies. In addition, photoluminescence (PL) measurements showed that the surface defects in the modified P25 affected the hole–electron recombination rate. UV–vis spectroscopy measurements show various size distribution and band gap effects after the simple modification process, and the photocatalytic activity was determined using the degradation of Rhodamine 6G (R6G). From these results, the degradation efficiency under solar and UV irradiation were measured to be 94 and 51% for modified P25 and be 47 and 25% for unmodified P25, respectively. The modified P25 showed twice the photocatalytic performance of the unmodified P25. The enhancement in the photocatalytic efficiency of modified P25 is correlated to the formation of surface defects, such as Ti<SUP>3+</SUP> and Ti-OH, the size distribution, and the re-aggregation of the anatase/rutile phases.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Improving photocatalytic property with modified P25 TiO<SUB>2</SUB>. </LI> <LI> Producing mid-bandgap due to surface defects and re-aggregation of anatase/rutile phase. </LI> <LI> Surface defects reduce re-combination time of electron-hole. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Effective Removal of Heavy Metals from Wastewater Using Modified Clay

Song, Mun-Seon,Vijayarangamuthu, K.,Han, EunJi,Jeon, Ki-Joon American Scientific Publishers 2016 Journal of nanoscience and nanotechnology Vol.16 No.5

<P>We report an economical and eco-friendly way to remove the heavy metal pollutant using modified clay. The modification of clay was done by calcining the natural clay from Kyushu region in Japan. Further, the removal efficiency for various pH and contact time was evaluated. The morphology of the clays was studied using the scanning electron microscopy (SEM). The structural and chemical analyses of modified clay were done by using X-ray diffraction (XRD), Raman spectroscopy, and Energy dispersion analysis (EDAX) to understand the properties related to the removal of heavy metal pollutant. Further, we studied the absorption efficiency of clay for various pH and contacting time using Ni polluted water. The modified clays show better removal efficiency for all pH with different saturation time. The adsorption follows pseudo-second order kinetics and the adsorption capacity of modified clay is 1.5 times larger than that of natural clay. The increase in the adsorption efficiency of modified clay was correlated to the increase in hematite phase along with increase in surface area due to surface morphological changes.</P>

Enhancement of photocatalytic disinfection of surface modified rutile TiO2 nanocatalyst

송문선,서정원,Kalimuthu Vijayarangamuthu,한은지,전기준 한국화학공학회 2016 Korean Journal of Chemical Engineering Vol.33 No.8

We demonstrate a facile modification of rutile TiO2 and its anti-bacterial activity under solar irradiation. The modification of rutile TiO2 was done by microwave-assisted hydrothermal process with hydrogen peroxide (H2O2) as a solvent. The structural properties were analyzed by using XRD and Raman studies. The modified rutile TiO2 shows no change either crystalline phase or crystalline size. The formation of Ti-OH was observed in Raman study. The TEM analysis shows modification on the surface of rutile TiO2. The photocatalytic disinfection of Escherichia coli (E. coli) under solar irradiation shows double-times better performance by modified rutile TiO2 compared to rutile TiO2. The enhancement of anti-bacterial activity was attributed surface modification and Ti-OH.

200 MeV Ag 15+ ion beam irradiation induced modifi cations in spray deposited MoO 3 thin films by fl uence variation

R. Rathika,M. Kovendhan,D. Paul Joseph,K. Vijayarangamuthu,A. Sendil Kumar,C. Venkateswaran,K. Asokan,S. Johnson Jeyakumar 한국원자력학회 2019 Nuclear Engineering and Technology Vol.51 No.8

Spray deposited Molybdenum trioxide (MoO3) thin film of thickness nearly 379 nm were irradiated with 200 MeV Ag15þ ion beam at different fluences (Ø) of 5 1011,1 1012,5 1012 and 1 1013 ions/cm2. The X-ray diffraction (XRD) pattern of the pristine film confirms orthorhombic structure and the crys-tallinity decreased after irradiation with the fluence of 5 1011 ions/cm2 due to irradiation induced defects and became amorphous at higher fluence. In pristine film, Raman modes at 665, 820, 996 cm1 belong to MoeO stretching, 286 cm1 belong to MoeO bending mode and those below 200 cm1 are associated with lattice modes. Raman peak intensities decreased upon irradiation and vanished completely for the ion fluence of 5 1012 ions/cm2. The percentage of optical transmittance of pristine film was nearly 40%, while for irradiated films it decreased significantly. Red shift was observed for both the direct and indirect band gaps. The pristine film surface had densely packed rod like structures with relatively less porosity. Surface roughness decreased significantly after irradiation. The electrical trans-port properties were also studied for both the pristine and irradiated films by Hall effect. The results are discussed.

Tailoring the properties of spray deposited V₂O₅ thin films using swift heavy ion beam irradiation

Rathika, R.,Kovendhan, M.,Joseph, D. Paul,Pachaiappan, Rekha,Kumar, A. Sendil,Vijayarangamuthu, K.,Venkateswaran, C.,Asokan, K.,Jeyakumar, S. Johnson Korean Nuclear Society 2020 Nuclear Engineering and Technology Vol.52 No.11

Swift heavy ion (SHI) beam irradiation can generate desirable defects in materials by transferring sufficient energy to the lattice that favours huge possibilities in tailoring of materials. The effect of Ag¹⁵⁺ ion irradiation with energy 200 MeV on spray deposited V₂O₅ thin films of thickness 253 nm is studied at various ion doses from 5 × 10¹¹ to 1 × 10¹³ ions/㎠. The XRD results of pristine film confirmed orthorhombic structure of V₂O₅ and its average crystallite size was found to be 20 nm. The peak at 394 cm^-1 in Raman spectra confirmed O-V-O bonding of V₂O₅, whereas 917 cm^-1 arise because of distortion in stoichiometry by a loss of oxygen atoms. Raman peaks vanished completely above the ion fluence of 5 × 10¹² ions/㎠. Optical studies by UV-Vis spectroscopy shows decrement in transmittance with an increase in ion fluence up to 5 × 10¹² ions/㎠. The red shift is observed both in the direct and indirect band gaps until 5 × 10¹² ions/㎠. The surface topography of the pristine film revealed sheath like structure with randomly distributed spherical nano-particles. The roughness of film decreased and the density of spherical nanoparticles increased upon irradiation. Irradiation improved the conductivity significantly for fluence 5 × 10¹¹ ions/㎠ due to band gap reduction and grain growth.

Prototype electrochromic device and dye sensitized solar cell using spray deposited undoped and 'Li' doped V₂O₅ thin film electrodes

Kovendhan, M.,Paul Joseph, D.,Manimuthu, P.,Sendilkumar, A.,Karthick, S.N.,Sambasivam, S.,Vijayarangamuthu, K.,Kim, H.J.,Choi, B.C.,Asokan, K.,Venkateswaran, C.,Mohan, R. Elsevier 2015 CURRENT APPLIED PHYSICS Vol.15 No.5

Lithium (Li) (0-5 wt%) doped V<SUB>2</SUB>O<SUB>5</SUB> thin films were spray deposited at 450 <SUP>o</SUP>C onto ITO substrates. Structural analysis using X-ray diffraction and Raman spectroscopy revealed orthorhombic phase of the films. In addition to the V<SUB>2</SUB>O<SUB>5</SUB> phase, presence of VO<SUB>2</SUB> peaks due to high deposition temperature is also evident from structural and optical characterization. The non-stoichiometric nature of the films due to loss of the terminal O atom was confirmed from Raman spectroscopy. The direct band gap, indirect bandgap, and phonon energies were also calculated from optical studies. Different charge states of vanadium ions present in the film were identified from X-ray photoelectron spectroscopy study. Results from cyclic voltammetry experiments reflected significant differences between the undoped and Li doped V<SUB>2</SUB>O<SUB>5</SUB> samples. Transport properties by Hall-effect measured at room temperature indicated significant increase in conductivity, carrier concentration and mobility of V<SUB>2</SUB>O<SUB>5</SUB> thin films on doping with Li. A Dye Sensitized Solar Cell (DSSC) was fabricated using mobility enhanced 5 wt% Li doped V<SUB>2</SUB>O<SUB>5</SUB> film as photoanode and its efficiency was found to be 2.7%. A simple electrochromic cell is fabricated using undoped V<SUB>2</SUB>O<SUB>5</SUB> thin film to demonstrate the colour change.

Prototype electrochromic device and dye sensitized solar cell using spray deposited undoped and ‘Li’ doped V2O5 thin film electrodes

M. Kovendhan,D. Paul Joseph,P. Manimuthu,A. Sendilkumar,S.N. Karthick,S. Sambasivam,K. Vijayarangamuthu,김희제,최병춘,K. Asokan,C. Venkateswaran,R. Mohan 한국물리학회 2015 Current Applied Physics Vol.15 No.5

Lithium (Li) (0-5 wt%) doped V2O5 thin films were spray deposited at 450 ℃ onto ITO substrates. Structural analysis using X-ray diffraction and Raman spectroscopy revealed orthorhombic phase of the films. In addition to the V2O5 phase, presence of VO2 peaks due to high deposition temperature is also evident from structural and optical characterization. The non-stoichiometric nature of the films due to loss of the terminal O atom was confirmed from Raman spectroscopy. The direct band gap, indirect bandgap, and phonon energies were also calculated from optical studies. Different charge states of vanadium ions present in the film were identified from X-ray photoelectron spectroscopy study. Results from cyclic voltammetry experiments reflected significant differences between the undoped and Li doped V2O5 samples. Transport properties by Hall-effect measured at room temperature indicated significant increase in conductivity, carrier concentration and mobility of V2O5 thin films on doping with Li. A Dye Sensitized Solar Cell (DSSC) was fabricated using mobility enhanced 5 wt% Li doped V2O5 film as photoanode and its efficiency was found to be 2.7%. A simple electrochromic cell is fabricated using undoped V2O5 thin film to demonstrate the colour change.