Chandran Sudakar

Bio: Chandran Sudakar is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Magnetization & Thin film. The author has an hindex of 32, co-authored 140 publications receiving 3204 citations. Previous affiliations of Chandran Sudakar include Wayne State University & Indian Institute of Science.

Role of support on the photocatalytic activity of titanium oxide

Abstract: We demonstrate an enhanced photocatalytic activity for TiO2 when it is dispersed on ZrO2 and zeolite compared to that dispersed on Al2O3 and CeO2. In these composite systems, TiO2 exists as a dispersed particulate phase and the extent of dispersion is the highest on ZrO2 support. Na–Y zeolite possesses the maximum Lewis acidity followed by ZrO2, Al2O3 and CeO2. Optical absorption property of TiO2 dispersed on ZrO2, zeolite and CeO2 is better than that of unsupported TiO2. In the above mentioned systems, photocatalytic activity of TiO2 shows a strong dependence on the surface acidity of the support. A significantly high photocatalytic activity for hydrogen generation from water–methanol mixture is observed for the TiO2–ZrO2 system. The enhanced activity of TiO2 dispersed on ZrO2 is attributed to the enhanced optical absorption and increased life time of the photogenerated charge carriers assisted by the surface acidic sites. Present study leads to a new result that a highly dispersed phase of TiO2 on a support having higher surface acidity exhibits enhanced photocatalytic activity. This strategy may be useful for the design of new catalysts yielding high photocatalytic activity. Presence of a co-catalyst like Pd metal enhances the photocatalytic activity further.

Synthesis of acicular hydrogoethite (α-FeOOH·xH2O; 0.1 < x < 0.22) particles using morphology controlling cationic additives and magnetic properties of maghemite derived from hydrogoethite

Abstract: A method for the preparation of acicular hydrogoethite (α-FeOOH·xH2O, 0.1 < x < 0.22) particles of 0.3–1 μm length has been optimized by air oxidation of Fe(II) hydroxide gel precipitated from aqueous (NH4)2Fe(SO4)2 solutions containing 0.005–0.02 atom% of cationic Pt, Pd or Rh additives as morphology controlling agents. Hydrogoethite particles are evolved from the amorphous ferrous hydroxide gel by heterogeneous nucleation and growth. Preferential adsorption of additives on certain crystallographic planes thereby retarding the growth in the perpendicular direction, allows the particles to acquire acicular shapes with high aspect ratios of 8–15. Synthetic hydrogoethite showed a mass loss of about 14% at ∼280 °C, revealing the presence of strongly coordinated water of hydration in the interior of the goethite crystallites. As evident from IR spectra, excess H2O molecules (0.1–0.22 per formula unit) are located in the strands of channels formed in between the double ribbons of FeO6 octahedra running parallel to the c-axis. Hydrogoethite particles constituted of multicrystallites are formed with Pt as additive, whereas single crystallite particles are obtained with Pd (or Rh). For both dehydroxylation as well as H2 reduction, a lower reaction temperature (∼220 °C) was observed for the former (Pt treated) compared to the latter (Pd or Rh) (∼260 °C). Acicular magnetite (Fe3O4) was prepared either by reducing hydrogoethite (magnetite route) or dehydroxylating hydrogoethite to hematite and then reducing it to magnetite (hematite–magnetite route). According to TEM studies, preferential dehydroxylation of hydrogoethite along leads to microporous hematite. Maghemite (γ-Fe2O3 − δ, 0 < δ < 0.25) was obtained by reoxidation of magnetite. The micropores are retained during the topotactic transformation to magnetite and finally to maghemite, whereas cylindrical mesopores are formed due to rearrangement of the oxygen sublattice from hexagonal to cubic close packing during the conversion of hydrogoethite to magnetite and then to maghemite. Accordingly, three different types of maghemite particles are realized: strongly oriented multicrystalline particles, single crystalline acicular particles with micropores or crystallites having mesopores. Higher values of saturation magnetization (σs = 74 emu g−1) and coercivity (Hc = 320 Oe) are obtained for single crystalline mesoporous particles. In the other cases, the smaller size of particles and larger distribution of micropores decreases σs considerably (<60 emu g−1) due to relaxation effects of spins on the surface atoms as revealed by Mossbauer spectroscopy.

Room temperature ferromagnetism in Cr-doped In2O3 on high vacuum annealing of thin films and bulk samples

Abstract: We report on the observation of room temperature ferromagnetism in Cr-doped In2O3 bulk samples and spin-coated thin films. The samples showed a clear ferromagnetism above 300K with magnetic moments of 0.008 and 0.22μB∕Cr at 300K for the bulk and thin film, respectively, only after high vacuum (HV) annealing at 600°C. The vacuum annealed Cr-doped In2O3 thin films showed a typical semiconducting behavior with a room temperature resistivity of 0.73Ωcm, while bulk samples were more conducting (23mΩcm). We present systematic investigations on the influence of HV annealing on the carrier concentrations, resistivity, and magnetic properties of the samples.

Raman scattering studies of magnetic Co-doped ZnO thin films

Abstract: Structural, magnetization, and Raman spectroscopic investigations have been carried out on spin coated Zn1−xCoxO (0⩽x⩽0.1) films. We investigated the broadening of the E2low mode for different values of x in both air and vacuum annealed films, and found a direct correlation of Co ions incorporation at the Zn sites with ferromagnetic order. The magnitudes of the magnetic moment are directly related to the size of the disorder correlation radius. However, for x∼5% where the magnetic moment becomes negligible, the broadening of the E2low Raman mode also becomes negligible, suggesting rejection of the Co ions from the Zn sites. For a given x, Co ions are incorporated at the Zn sites with the same concentration in both the air and vacuum annealed films but the magnetic moment values are much smaller for the air annealed samples. This behavior is directly related to the presence of oxygen vacancies. We also discuss the effects of air and vacuum annealing on the linewidth of E2high and A1 (LO) modes. At higher doping levels, e.g., x>5%, the air annealed films showed a strong phase separation tendency toward Co3O4 as shown by both Raman and high resolution electron microscopy.

Semiconductor-based Photocatalytic Hydrogen Generation

Abstract: 2.3. Evaluation of Photocatalytic Water Splitting 6507 2.3.1. Photocatalytic Activity 6507 2.3.2. Photocatalytic Stability 6507 3. UV-Active Photocatalysts for Water Splitting 6507 3.1. d0 Metal Oxide Photocatalyts 6507 3.1.1. Ti-, Zr-Based Oxides 6507 3.1.2. Nb-, Ta-Based Oxides 6514 3.1.3. W-, Mo-Based Oxides 6517 3.1.4. Other d0 Metal Oxides 6518 3.2. d10 Metal Oxide Photocatalyts 6518 3.3. f0 Metal Oxide Photocatalysts 6518 3.4. Nonoxide Photocatalysts 6518 4. Approaches to Modifying the Electronic Band Structure for Visible-Light Harvesting 6519

Understanding TiO2 photocatalysis: mechanisms and materials.

Abstract: Jenny Schneider,*,† Masaya Matsuoka,‡ Masato Takeuchi,‡ Jinlong Zhang, Yu Horiuchi,‡ Masakazu Anpo,‡ and Detlef W. Bahnemann*,† †Institut fur Technische Chemie, Leibniz Universitaẗ Hannover, Callinstrasse 3, D-30167 Hannover, Germany ‡Faculty of Engineering, Osaka Prefecture University, 1 Gakuen-cho, Sakai Osaka 599-8531, Japan Key Lab for Advanced Materials and Institute of Fine Chemicals, East China University of Science and Technology, Shanghai 200237, China

Ferromagnetic materials

Abstract: In this chapter, we will restrict our attention to the ferrites and a few other closely related materials. The great interest in ferrites stems from their unique combination of a spontaneous magnetization and a high electrical resistivity. The observed magnetization results from the difference in the magnetizations of two non-equivalent sub-lattices of the magnetic ions in the crystal structure. Materials of this type should strictly be designated as “ferrimagnetic” and in some respects are more closely related to anti-ferromagnetic substances than they are to ferromagnetics in which the magnetization results from the parallel alignment of all the magnetic moments present. We shall not adhere to this special nomenclature except to emphasize effects, which are due to the existence of the sub-lattices.

Advanced Nanoarchitectures for Solar Photocatalytic Applications

Abstract: UV-Visible ار راد ن .د TiO2 ( تیفرظ راون مان هب نورتکلا یاراد یژرنا زارت لماش VB و ) رگید زارت ی یژرنا اب ( ییاناسر راون مان هب نورتکلا زا یلاخ و رتلااب VB یم ) .دشاب ت ود نیا نیب یژرنا توافت یژرنا فاکش زار ، پگ دناب هدیمان یم .دوش هک ینامز زا نورتکلا لاقتنا VB هب VB یم ماجنا دریگ ، TiO2 اب ودح یژرنا بذج د ev 2 / 3 ، نورتکلا تفج کی دیلوت یم هرفح .دیامن و نورتکلا هرفح ی نا اب هدش دیلوت یم کرتشم حطس هب لاقت ثعاب دناوت شنکاو ماجنا اه یی ددرگ . TiO2 دربراک ،دراد یدایز یاه هلمج زا یم ناوت اوه یگدولآ هیفصت یارب (CO2) و بآ و ... نآ زا هدافتسا درک .

Titanium dioxide-based nanomaterials for photocatalytic fuel generations.

Abstract: Generations Yi Ma,† Xiuli Wang,† Yushuai Jia,† Xiaobo Chen,‡ Hongxian Han,*,† and Can Li*,† †State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences and Dalian National Laboratory for Clean Energy, 457 Zhongshan Road, Dalian 116023, China ‡Department of Chemistry, College of Arts and Sciences, University of Missouri-Kansas City, 5100 Rockhill Road, Kansas City, Missouri 64110, United States