Biju, Francis; Dr. M. L. P. Reddy(Cochin University of Science and Technology, January 6, 2016)
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Abstract:
The fascinating photoluminescence properties of trivalent europium (Eu3+)
coordination compounds have aroused tremendous interest in recent years due
to their potential applications ranging from biomedical analysis to material
science. The Eu3+ ions have excellent luminescent features such as long-lived
excited-state lifetimes (μs–ms range) and narrow, easily recognizable line-like
red emission bands with large Stokes shifts. A big challenge in the chemistry of
lanthanide ions is to develop luminescent europium complexes that can be
sensitized by visible-light. This field has become much more important because
of the demand for less-harmful labelling reagents in the life sciences and lowvoltage-
driven pure-red emitters in optoelectronic. Thus, the primary objective
of the present research work is to design and develop novel visible-light
sensitized Eu3+-β-diketonate complexes with impressive photophysical
propertiesThe thesis comprises of four chapters which are presented as independent
units and therefore the structure formulae, schemes, figures and references are
numbered chapterwise. The introductory chapter highlights a background
sketch of the use of β-diketonates as antenna ligands for Eu3+ ion, the recent
developments in visible light excitable Eu3+-β-complexes and an overview of
the various methods of synthesis of Eu3+-based silica hybrid materials, their
photophysical properties and possible applications
Prathapachandra Kurup, M R; Suma, S; Sudarsana Kumar, M R; Siji, V L(Elsevier, February 26, 2010)
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Abstract:
Eight new transition metal complexes of benzaldehyde-N(4)–phenylsemicarbazone have been synthesized
and characterized by elemental analyses, molar conductance, electronic and infrared spectral
studies. In all the complexes, the semicarbazone is coordinated as neutral bidentate ligand. 1H NMR
spectrum of [Zn(HL)2(OAc)2] shows that there is no enolisation of the ligand in the complex. The magnetic
susceptibility measurements indicate that Cr(III), Mn(II), Fe(III), Co(II) and Cu(II) complexes are
paramagnetic and Ni(II) is diamagnetic. The EPR spectrum of [Mn(HL)2(OAc)2] in DMF solution at 77K
shows hyperfine sextet with low intensity forbidden lines lying between each of the two main hyperfine
lines. The g values calculated for the [Cu(HL)2SO4] complex in frozen DMF, indicate the presence of
unpaired electron in the dx2−y2 orbital. The metal ligand bonding parameters evaluated showed strong
in-plane bonding and in-plane bonding. The ligand and complexes were screened for their possible
antimicrobial activities.
Description:
Spectrochimica Acta Part A 76 (2010) 22–28 doi:10.1016/j.saa.2010.02.035
Pazhoor Bijumon, Varghese; Mohanan, P; Mailadil, Thomas Sebastian(The Japan Society of Applied Physics, 2002)
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Abstract:
Microwave ceramic dielectric materials Ca5Nb2TiO12 and Ca5Ta2TiO12 have been prepared by a conventional solid-state
ceramic process. The structure was studied by X-ray diffraction and the dielectric properties were characterized at microwave
frequencies. The ceramics posses a relatively high dielectric constant, very low dielectric loss (Q5 x f > 30000GHz) and
small temperature variation of resonant frequency. These materials are potential candidates for dielectric resonator
applications in microwave integrated circuits. [DOI: 10. 1 143/JJAP.41.3834]
Pramila Devi, D S; Dr.Sunil,Narayanankutty K(Cochin University of Science And Technology, December , 2012)
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Abstract:
The search for new materials especially those possessing special
properties continues at a great pace because of ever growing demands of the
modern life. The focus on the use of intrinsically conductive polymers in
organic electronic devices has led to the development of a totally new class of
smart materials. Polypyrrole (PPy) is one of the most stable known conducting
polymers and also one of the easiest to synthesize. In addition, its high
conductivity, good redox reversibility and excellent microwave absorbing
characteristics have led to the existence of wide and diversified applications for
PPy. However, as any conjugated conducting polymer, PPy lacks processability,
flexibility and strength which are essential for industrial requirements. Among
various approaches to making tractable materials based on PPy, incorporating
PPy within an electrically insulating polymer appears to be a promising method,
and this has triggered the development of blends or composites. Conductive
elastomeric composites of polypyrrole are important in that they are composite
materials suitable for devices where flexibility is an important parameter.
Moreover these composites can be moulded into complex shapes.
In this work an attempt has been made to prepare conducting elastomeric
composites by the incorporation of PPy and PPy coated short Nylon-6 fiber
with insulating elastomer matrices- natural rubber and acrylonitrile butadiene
rubber. It is well established that mechanical properties of rubber composites
can be greatly improved by adding short fibers. Generally short fiber
reinforced rubber composites are popular in industrial fields because of their
processing advantages, low cost, and their greatly improved technical
properties such as strength, stiffness, modulus and damping. In the present
work, PPy coated fiber is expected to improve the mechanical properties of the
elastomer-PPy composites, at the same time increasing the conductivity. In
addition to determination of DC conductivity and evaluation of mechanical
properties, the work aims to study the thermal stability, dielectric properties
and electromagnetic interference shielding effectiveness of the composites.
The thesis consists of ten chapters.
Description:
Department of Polymer Science and Rubber Technology,
Cochin University of Science and Technology
Pramila Devi, D.S.; Dr. Sunil K. Narayanan Kutty(Cochin University of Science and Technology, December 12, 2012)
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Abstract:
The search for new materials especially those possessing special
properties continues at a great pace because of ever growing demands of the
modern life. The focus on the use of intrinsically conductive polymers in
organic electronic devices has led to the development of a totally new class of
smart materials. Polypyrrole (PPy) is one of the most stable known conducting
polymers and also one of the easiest to synthesize. In addition, its high
conductivity, good redox reversibility and excellent microwave absorbing
characteristics have led to the existence of wide and diversified applications for
PPy. However, as any conjugated conducting polymer, PPy lacks processability,
flexibility and strength which are essential for industrial requirements. Among
various approaches to making tractable materials based on PPy, incorporating
PPy within an electrically insulating polymer appears to be a promising method,
and this has triggered the development of blends or composites. Conductive
elastomeric composites of polypyrrole are important in that they are composite
materials suitable for devices where flexibility is an important parameter.
Moreover these composites can be moulded into complex shapes.
Dielectric ceramics based on solid solution phases of [RE1_x= REr]TiNb06, where REI_s = Nd, Pr, Sm and RE' = Dy, Gd and Y, were prepared by the conventional solid-state ceramic route for values of x. The ceramic samples are characterized by X-ray diffraction and microwave methods. Ceramics based on RE (Pr, Nd and Sm) belonging to aeschynite group shows positive value of Tf and those based on RE (Gd, Dy and Y) belonging to euxenite group show negative value of r f. The solid solution phases between the aeschynite and the euxenite group shows intermediate dielectric constant and r f values. The results indicate the possibility of tailoring the dielectric properties by varying the composition of the solid solution phases. The range of solid solubility of euxenite in aeschenite and aeschenite
in euxenite are different for different rare earth ions
Mohammed Yusuff, K K; Manju, Sebastian; Arun, Vasudevan; Robinson, P P; Leeju, Pally; Digna, Varghese; Varsha, Gopalakrishnan(Taylor & Francis, Journal of Coordination Chemistry, October 15, 2009)
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Abstract:
The mononuclear cobalt(II) complex [CoL2] H2O (where HL is quinoxaline-2-carboxalidine-
2-amino-5-methylphenol) has been prepared and characterized by elemental analysis, conductivity
measurement, IR, UV-Vis spectroscopy, TG-DTA, and X-ray structure determination.
The crystallographic study shows that cobalt(II) is distorted octahedral with each tridentate
NNO Schiff base in a cis arrangement. The crystal exhibits a 2-D polymeric structure parallel to
[010] plane, formed by O-H...N and O-H... O intermolecular hydrogen bonds and pye
stacking interactions, as a racemic mixture of optical enantiomers. The ligand is a Schiff base
derived from quinoxaline-2-carboxaldehyde
Reena Mary, A P; Narayanan, T N; Vijutha, Sunny; Sakthi Kumar, D; Yasuhiko, Yoshida; Joy, P A; Anantharaman, M R(Springer, 2010)
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Abstract:
Bio-compatible magnetic fluids having high
saturation magnetization find immense applications in
various biomedical fields. Aqueous ferrofluids of superparamagnetic
iron oxide nanoparticles with narrow size
distribution, high shelf life and good stability is realized by
controlled chemical co-precipitation process. The crystal
structure is verified by X-ray diffraction technique. Particle
sizes are evaluated by employing Transmission electron
microscopy. Room temperature and low-temperature magnetic
measurements were carried out with Superconducting
Quantum Interference Device. The fluid exhibits good
magnetic response even at very high dilution (6.28 mg/cc).
This is an advantage for biomedical applications, since only
a small amount of iron is to be metabolised by body organs.
Magnetic field induced transmission measurements carried
out at photon energy of diode laser (670 nm) exhibited
excellent linear dichroism. Based on the structural and
magnetic measurements, the power loss for the magnetic nanoparticles under study is evaluated over a range of
radiofrequencies.
Bejoy, Thomas; Prathapan, Sreedharan; Sugunan, Sankaran(Elsevier, May , 2005)
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Abstract:
The synthesis of dimethyl acetals of carbonyl compounds such as cyclohexanone, acetophenone, and benzophenone has successfully been carried out by the reaction between ketones and methanol using different solid acid catalysts. The strong influence of the textural properties of the catalysts such as acid amount and adsorption properties (surface area and pore volume) determine the catalytic activity. The molecular size of the reactants and products determine the acetalization ability of a particular ketone. The hydrophobicity of the various rare earth exchanged Mg–Y zeolites, K-10 montmorillonite clay, and cerium exchanged montmorillonite (which shows maximum activity) is more determinant than the number of active sites present on the catalyst. The optimum number of acidic sites as well as dehydrating ability of Ce3+-montmorillonite and K-10 montmorillonite clays and various rare earth exchanged Mg–Y zeolites seem to work well in shifting the equilibrium to the product side.
Anantharaman, M R; Suchand Sandeep, C S; Narayanan, T N; Shaijumon, M M; Ajayan, P M; Reji, Philip(IOP Publishing LTD, June 24, 2009)
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Abstract:
Magnetic heterostructures with carbon nanotubes having multiple functionalities are fascinating
materials which can be manipulated by means of an external magnetic field. In this paper we
report our investigations on the synthesis and optical limiting properties of pristine cobalt
nanotubes and high coercivity cobalt-in-carbon nanotubes (a new nanosystem where carbon
nanotubes are filled with cobalt nanotubes). A general mobility assisted growth mechanism for
the formation of one-dimensional nanostructures inside nanopores is verified in the case of
carbon nanotubes. The open-aperture z-scan technique is employed for the optical limiting
measurements in which nanosecond laser pulses at 532 nm have been used for optical
excitation. Compared to the benchmark pristine carbon nanotubes these materials show an
enhanced nonlinear optical absorption, and the nonlinear optical parameters calculated from the
data show that these materials are efficient optical limiters. To the best of our knowledge this is
the first report where the optical limiting properties of metal nanotubes are compared to those of
carbon nanotubes
Anantharaman, M R; Narayanan, T N; Shaijumon, M M; Ajayan, P M(American Chemical Society, July 3, 2008)
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Abstract:
Cobalt nanotubes (CoNTs) with very high longitudinal coercivity were prepared by electrodeposition of cobalt
acetate for the first time by using anodized alumina (AAO) template. They were then characterized with
X-ray diffraction (XRD), a field emission scanning electron microscope (FESEM), and a transmission electron
microscope (TEM). Formation of a highly ordered hexagonal cobalt phase is observed. Room temperature
SQUID (superconducting quantum interference device) magnetometer measurements indicate that the easy
axis of magnetization is parallel to the nanotube axis. These CoNTs exhibit very high longitudinal coercivity
of ∼820 Oe. A very high intertubular interaction resulting from magnetostatic dipolar interaction between
nanotubes is observed. Thick-walled nanotubes were also fabricated by using cobalt acetate tetrahydrate
precursors. A plausible mechanism for the formation of CoNTs based on mobility assisted growth is proposed.
The role of the hydration layer and the mobility of metal ions are elucidated in the case of the growth mechanism
of one-dimensional geometry
Anantharaman, M R; Shaijumon, M M; Ajayan, P M; Narayanan, T N(Springer, October 21, 2009)
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Abstract:
Hybrid magnetic nanostructures with high
coercivity have immense application potential in various
fields. Nickel (Ni) electrodeposited inside Cobalt (Co)
nanotubes (a new system named Ni @ Co nanorods) were
fabricated using a two-step potentiostatic electrodeposition
method. Ni @ Co nanorods were crystalline, and they have
an average diameter of 150 nm and length of *15 lm.
The X-ray diffraction studies revealed the existence of two
separate phases corresponding to Ni and Co. Ni @ Co
nanorods exhibited a very high longitudinal coercivity. The
general mobility-assisted growth mechanism proposed for
the growth of one-dimensional nanostructures inside nano
porous alumina during potentiostatic electrodeposition is
found to be valid in this case too
Muhammad, Abdul Jamal E; Joy, P A; Anantharaman, M R; Philip, Kurian(Elsevier, January , 2009)
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Abstract:
Nanocomposites based on natural rubber and nano-sized nickelwere synthesized by incorporating nickel
nanoparticles in a natural rubber matrix for various loadings of the filler. Structural, morphological, magnetic
and mechanical properties of the compositeswere evaluated along with a detailed study of dielectric
properties. Itwas found that nickel particleswere uniformly distributed in the matrix without agglomeration
resulting in a magnetic nanocomposite. The elastic properties showed an improvement with increase
in filler content but breaking stress and breaking strain were found to decrease. Dielectric permittivity
was found to decrease with increase in frequency, and found to increase with increase in nickel loading.
The decrease in permittivity with temperature is attributed to the high volume expansivity of rubber at
elevated temperatures. Dielectric loss of blank rubber as well as the composites was found to increase
with temperature.
Eby Thomas, Thachil; Unnikrishnan, K P; Benny Cherian, A; Jenish, Paul(Universal Research Publications, December , 2011)
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Abstract:
In this study, pendant epoxy functional poly dimethyl siloxanes were synthesized by the hydrosilylation reaction of pendant silyl hydride functional polydimethyl siloxane with allyl glycidyl ether. The hydrosilylation reaction was characterized by spectroscopic techniques. Samples of pendant epoxy functional poly dimethyl siloxanes and pendant silyl hydride functional polydimethyl siloxane were blended with commercial epoxy resin, diglycidyl ether of bis-phenol A, at various ratios using a polyamine as curing agent. The results show that the addition of functionalised poly dimethyl siloxanes increases the flexibility of the cross linked network and also the thermal stability and water resistance
Description:
Advances in Polymer Science and Technology: An International Journal 2011; 1 (2): 22-29