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41.
The SrS:Ce/ZnS:Mn phosphor blends with various combination viz 75:25, 50:50 and 25:75 were assign to generate the white-light emission using near-UV and blue-light emitting diodes (LED) as an excitation source. The SrS:Ce exhibits strong absorption at 427 nm and the corresponding intense emission occurs at 480 and 540 nm due to electron transition from 5d(2D)−4f(2F5/2, 7/2) of Ce3+ ion as a result of spin-orbit coupling. The ZnS:Mn excited under same wavelength shows broad emission band with λmax=582 nm originates due to 3d (4G−6S) level of Mn2+. Photoluminescence studies of phosphor blend excited using near-UV to blue light confirms the emitted radiation varies from cool to warm white light in the range 430-600 nm, applicable to LED lightings. The CIE chromaticity coordinate values measured using SrS:Ce/ZnS:Mn phosphor blend-coated 430 nm LED pumped phosphors in the ratio 75:25, 50:50 and 25:75 are found to be (0.235, 0.125), (0.280, 0.190) and (0.285, 0.250), respectively. 相似文献
42.
Panchatcharam Thiyagarajan M. S. Ramachandra Rao 《Applied Physics A: Materials Science & Processing》2010,99(4):947-953
Rare earth ions (Ce3+, Eu2+) activated Ca3MgSi2O8 (CMSO) phosphors have been synthesized using solid-state reaction method in 95%N2+5%H2 reduction atmosphere at elevated temperatures by varying Eu2+ concentration from 0.0075 to 0.0300 at the fixed Ce0.03 concentration to study their photoluminescence (PL) properties. An energy transfer occurs from Ce3+ to Eu2+ through a significant overlap of Eu2+ excitation spectrum with Ce3+ emission spectrum in CMSO, together with the systematic relative decrease and increase in emission bands of Ce3+ and Eu2+, respectively, have been observed. To support the phenomenon, diffuse reflectance spectra show various absorption levels corresponding to Ce3+, Eu2+, and/or mixture of both rare earth ions. An optimum emission was realized at 0.0150 of Eu2+ via. energy transfer from Ce3+ ion. By utilizing the principle of energy transfer, the critical distance (R c ) between activator ions was found to be 18.64 Å. The CIE chromaticity coordinates measured on the Ca3MgSi2O8:Ce3+, Eu2+ phosphors excited under ultraviolet (365 nm) source shows the values lie in cool white light region could be applied to solid state lighting. 相似文献
43.
Narayanan RA Thiyagarajan P Lewis S Bansal A Schadler LS Lurio LB 《Physical review letters》2006,97(7):075505
A small amount of alumina nanoparticles in polymethylmethacrylate causes a sharp depression of the glass transition temperature (Tg) accompanied by a toughening of the composite. We investigated this phenomenon using multispeckle x-ray photon correlation spectroscopy. Measurements reveal a dynamic structure factor that has the form exp[-(t/taua)beta], with beta greater than 1. We show for the first time that beta(T) tracks the internal stress at the polymer-particle interface. The internal stress, which we propose arises due to the entropic penalty that the polymer faces in the presence of the nanoparticles, engenders temporally heterogeneous dynamics. In the jammed glassy state, we show that the dominant fast relaxation mode--taumax--aided by a weak dewetting interface relieves the stress and follows the variations in Tg. 相似文献
44.
J. Daisy Vimala Rani S. Kamatchi A. Dhathathreyan 《Journal of colloid and interface science》2010,341(1):48-52
Stable lyophilisomes of fibrinogen at pH 7.5 have been prepared by the method of a rapid freezing–heating and annealing sequence. Reduction of the lyophilisomes of the nickel–fibrinogen complex coated on solid substrates and subsequent heating showed formation of nickel hydroxide and finally nickel oxide. Ultraviolet–visible spectroscopy has been used to monitor the thin films of pure fibrinogen microcapsules, as well as the subsequent nucleation and growth of nanoparticles within the supramolecular structure. Transmission electron microscopy showed initially a thread-like structure which disappeared on continued heating, resulting in nanoparticles ranging from 10 to 50 nm. Particle-size distribution of product was analyzed by using X-ray diffraction (XRD), transmission electron microscopy (TEM) and the corresponding selected area electron diffraction (SAED), and Brunauer–Emmett–Teller (BET) N2 adsorption. The results suggest that the NiO particles have a body-centered cubic structure and are well dispersed. The particle-size distribution ranges from 10 to 50 nm with an average particle size about 28 nm, and the specific surface area is 34 m2/g. Magnetic study carried out on the prepared nanoparticles showed a ferromagnetic behavior. 相似文献
45.
Barun K. Datta Durairaj Thiyagarajan Chirantan Kar Aiyagari Ramesh Gopal Das 《Analytica chimica acta》2015
A new tricarbocyanine-based chemosensor exhibited a dramatic Al3+-specific fluorescence turn-on response in the near-infrared (NIR) region. The receptor was found to be highly selective towards Al3+ over other metal ions in physiological condition. The sensor was non-toxic and could thus be employed as an imaging probe for detecting intracellular Al3+ in live cells. Interestingly, upon interaction with DNA in solution, the L–Al3+ ensemble rendered tracking of DNase activity in solution through a systematic reduction in the fluorescence emission intensity. 相似文献
46.
Siluvaimuthu S. Thiyagarajan S. Martin Leenus Jesu Nagalingam B. 《Journal of Thermal Analysis and Calorimetry》2020,140(4):1945-1956
Journal of Thermal Analysis and Calorimetry - High-viscous neat neem oil (NO) with low-viscous wintergreen oil (WGO) may be used in diesel engines without any engine modification. Based on the... 相似文献
47.
Padmanabhan Santhosh Nagarajan Senthil Kumar Murugesan Renukadevi Anantha Iyengar Gopalan Thiyagarajan Vasudevan Kwang-Pill Lee 《Analytical sciences》2007,23(4):475-478
A glassy carbon electrode modified with a coating of polypyrrole (Ppy) exhibited an attractive performance for the detection and determination of a non-steroidal and non-narcotic analgesic compound, ketorolac tromethamine (KT). Cyclic voltammetry, differential pulse and square wave voltammetry were used in a combined way to identify the electrochemical characteristics and to optimize the conditions for detection. For calibrating and estimating KT, square-wave voltammetry was mainly used. The drug shows a well-defined peak at -1.40 V vs. Ag/AgCl in the acetate buffer (pH 5.5). The existence of Ppy on the surface of the electrode gives higher electrochemical active sites at the electrode for the detection of KT and preconcentrate KT by adsorption. The square-wave stripping voltammetric response depends on the excitation signal and the accumulation time. The calibration curve is linear in the range 1 x 10(-11) to 1 x 10(-7) M with a detection limit of 1.0 x 10(-12) M. Applicability to serum samples was also demonstrated. A detection limit of 1.0 ng ml for serum was observed. Square-wave voltammetry shows superior performance over UV spectroscopy and other techniques. 相似文献
48.
Thiyagarajan Shanmugam C. Sivakumar A. Sultan Nasar 《Journal of polymer science. Part A, Polymer chemistry》2008,46(16):5414-5430
Novel AB2‐type monomers such as 3,5‐bis(4‐methylolphenoxy)benzoic acid ( monomer 1 ), methyl 3,5‐bis(4‐methylolphenoxy) benzoate ( monomer 2 ), and 3,5‐bis(4‐methylolphenoxy)benzoyl chloride ( monomer 3 ) were synthesized. Solution polymerization and melt self‐polycondensation of these monomers yielded hydroxyl‐terminated hyperbranched aromatic poly(ether‐ester)s. The structure of these polymers was established using FTIR and 1H NMR spectroscopy. The molecular weights (Mw) of the polymers were found to vary from 2.0 × 103 to 1.49 × 104 depending on the polymerization techniques and the experimental conditions used. Suitable model compounds that mimic exactly the dendritic, linear, and terminal units present in the hyperbranched polymer were synthesized for the calculation of degree of branching (DB) and the values ranged from 52 to 93%. The thermal stability of the polymers was evaluated by thermogravimetric analysis, which showed no virtual weight loss up to 200 °C. The inherent viscosities of the polymers in DMF ranged from 0.010 to 0.120 dL/g. End‐group modification of the hyperbranched polymer was carried out with phenyl isocyanate, 4‐(decyloxy)benzoic acid and methyl red dye. The end‐capping groups were found to change the thermal properties of the polymers such as Tg. The optical properties of hyperbranched polymer and the dye‐capped hyperbranched polymer were investigated using ultraviolet‐absorption and fluorescence spectroscopy. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5414–5430, 2008 相似文献
49.
Kolesnikov AI Zanotti JM Loong CK Thiyagarajan P Moravsky AP Loutfy RO Burnham CJ 《Physical review letters》2004,93(3):035503
Quasi-one-dimensional water encapsulated inside single-walled carbon nanotubes, here referred to as nanotube water, was studied by neutron scattering. The results reveal an anomalously soft dynamics characterized by pliable hydrogen bonds, anharmonic intermolecular potentials, and large-amplitude motions in nanotube water. Molecular dynamics simulations consistently describe the observed phenomena and propose the structure of nanotube water, which comprises a square-ice sheet wrapped into a cylinder inside the carbon nanotube and interior molecules in a chainlike configuration. 相似文献
50.