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.

Synthesis of Cu-Deficient and Zn-Graded Cu–In–Zn–S Quantum Dots and Hybrid Inorganic–Organic Nanophosphor Composite for White Light Emission

Abstract: Cu-deficient graded-zinc Cu-In-Zn-S (CIZS) quantum dots (QDs) were synthesized by a two-step solvothermal method. These CIZS QDs exhibited size and composition tunable photoluminescence characteristics with emission color tunable from greenish-yellow to orange to red with a relatively high quantum yield between 45 and 60%. Novel white-light-emitting (WLE) hybrid composite is fabricated by integrating the blue-emissive 1,4-bis-2-(5-phenyl oxazolyl)-benzene (POPOP) organic fluorophore and quaternary CIZS inorganic QDs. Integrating CIZS QDs with POPOP fluorophore resulted in series of tunable emission colors with CIE coordinates lying in a straight line between the coordinates of the end member. WLE was shown for hybrid mixture comprising 0.5 nM of POPOP and 3 mg/mL of CIZS QDs with color coordinates (0.3312, 0.3324). Thin films of this hybrid mixture in PMMA matrix coated on UV-LED or on glass substrates with UV backlit light also showed broadband WLE with ideal CIE color coordinates of (0.34, 0.33), high color-rendering index value of 92, and correlated color temperature value of 5143 K. The hybrid composite exhibit Forster resonance energy transfer cascading from POPOP to CIZS which results in emission covering the entire visible spectral range. POPOP and CIZS QDs hybrid composite is a versatile material for WLED applications.

Effects of fatty acid surfactants on the magnetic and magnetohydrodynamic properties of ferrofluids

Abstract: We prepared Fe3O4 magnetic nanoparticles having diameters of approximately 12 nm by chemical coprecipitation, which were coated with three different fatty acid surfactants: oleic acid, lauric acid, and myristic acid. From x-ray diffraction, transmission electron microscopy, and Mossbauer spectroscopy measurements we confirmed that Fe3O4 is the only phase present in the samples. The zero field cooled magnetization curves for the nanoparticles exhibit broad peaks, consistent with superparamagnetic blocking for the polydisperse samples, and a saturation magnetization smaller than that for bulk Fe3O4. Although there are minimal differences in the magnetic properties of the nanoparticles having different surfactants, we find significant changes in the hydrodynamic response depending on chain length. Hyperthermia measurements show considerably larger response for oleic acid-coated samples, while magneto-optical studies indicate that these samples have slower dynamics of aggregation under the influence of a dc f...

Hexaferrite–FeCo nanocomposite particles and their electrical and magnetic properties at high frequencies

Abstract: Nanocomposites are realized by chemical reduction whereby the conducting magnetic particles of Fe–Co alloy are generated within the insulating ferrimagnetic $BaCo_2Fe_{16}O_{27}$ or $Ba_2Co_2Fe_{12}O_{22}$ hexaferrite matrix. Transmission electron microscopy revealed that metal nanoparticles precipitate coherently as thin flakes along the a–b planes of the derivative magnetoplumbite lattice of the hexaferrites above the characteristic reduction temperature, $T_R$ >375 °C in $H_2$ atmosphere. The coercivity increases with $T_R$ in the early stages of the solid-state precipitation and then decreases with the formation of larger fractions of Fe–Co alloy; a converse trend is noticed for magnetization. The complex permittivity increases with reduction to ~50 in the broad frequency range of 4–18 GHz. The complex permeability is also enhanced with the content of Fe–Co nanoparticles. It is proposed that the spin reorientation at the Fe–Co/hexaferrite interface gives rise to broadband response, rendering these composite particles useful as electromagnetic microwave absorbers.

Effect of cationic substituents on particle morphology of goethite and the magnetic properties of maghemite derived from substituted goethite

Abstract: Preparation of nanoparticles with the desired shape and size by the wet-chemical precipitation process is a challenging task. Thus, the effects of different substitutional impurities such as Al, Cr, Co or Ni on the particle morphology and phase stability of goethite have been investigated. Goethite is prepared by air oxidation of $Fe(OH)_2 · xH_2O$ gel under near neutral conditions. Below certain concentration levels of dopants $(Al^{3+} \leq 10; Cr^{3+} \leq 5; Co^{2+} \leq 10$ and $Ni^{2+} \leq 5 at.%)$ the samples remained monophasic as revealed by XRD, TEM, and IR studies. Above these levels, the substituents produce traces of secondary phases such as lepidocrocite, spinel ferrite and $M^n(OH)_n$. The goethite structure is stable in spite of the iso- or aliovalent substitutions. The individual additives have divergent influence on the particle morphology; $Al^{3+}$ and $Cr^{3+}$ decreases the particle size to <50 nm and aspect ratio (AR) <2. Co-substitution produces slender particles with AR as high as 25. Whereas, $Ni^{2+}$ does not have any influence on the particle morphology. The attributable factors in morphology control are the increased nucleation rate, restricted growth along needle axes, and the strain induced in the goethite lattice as a result of difference in ionic radii. Maghemite, $\gamma -Fe_2O_3– \delta$, particles are obtained from goethite wherein the topotactic conversion renders the retention of the particle morphology of the precursor. Maghemite with substituted impurities showed substantial differences in magnetic properties. Saturation magnetization $(\sigma s)$ and coercivity $(H_ c)$ go down to very low values due to relaxation of spins on the surface atoms as revealed by Mossbauer spectroscopy. Decrease in coercivity is by way of the presence of diamagnetic ion $(Al^{3+})$. Whereas, Co-substituted maghemite has enhanced $H_ c$ as a result of high magnetocrystalline anisotropy accompanied by the shape anisotropy.

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