The differaction efficiency,sensitivity and storage life of Methylene blue sensitized poly(vinyl chloride) film was improved by the addition of an electron donor in the matrix. The
addition of pyridine enhanced the diffraction efficiency by two times and storage life of the
gratings was increased to 2-3 days.
Sreekumar, K(Japaneese society of Applied physics, November 8, 2006)
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Abstract:
Copper doped methylene blue sensitized poly(vinyl alcohol) (MBPVA)–acrylamide films were fabricated to improve the
storage life of recorded gratings. The films were fabricated using gravity settling method and the copper chloride
concentration was optimized as 3:18 10 3 mol/l for a dye concentration of 6:2 10 4 mol/l. The gratings recorded on the
optimized film constitution could be stored for months with stable diffraction efficiency (24%) without any chemical or
thermal fixing techniques. The resolution of the material is found to be unaffected with the addition of copper chloride.
Invertase was immobilized on acid activated montmorillonite via two independent procedures, adsorption and covalent binding. The immobilized enzymes were characterized by XRD, NMR and N2 adsorption measurements and their activity was tested in a fixed bed reactor. XRD revealed that the enzyme was situated on the periphery of the clay and the side chains of different amino acid residues were involved in intercalation with the clay matrix. NMR demonstrated that tetrahedral Al was linked to the enzyme during adsorption and the octahedral Al was involved during covalent binding. Secondary interaction of the enzyme with Al was also observed. N2 adsorption studies showed that covalent binding of enzymes caused pore blockage since the highly polymeric species were located at the pore entrance. The fixed bed reactor proved to be efficient for the immobilized invertase. The optimum pH and pH stability improved upon immobilization. The kinetic parameters calculated also showed an enhanced efficiency of the immobilized systems. They could be used continuously for long period. Covalently bound invertase demonstrated greater operational stability.
Seven bis(ligand) Co(III) complexes {[CoL21] NO3 · H2 O (1), [CoL21] Cl · 2 H2 O (2),[CoL21] ClO4 (3), [CoL22] NO3 (4), [CoL22] Cl · 2 H2 O (5), [CoL23] Br · 2 H2 O (6), [CoL23] ClO4 · H2 O (7)} of three thiosemicarbazone ligands {pyridine-2-carbaldehyde-N(4)-p-methoxyphenyl thiosemicarbazone [HL1], pyridine-2-carbaldehyde-N(4)-2-phenylethyl thiosemicarbazone [HL2] and pyridine-2-carbaldehyde-N(4)-(methyl),N(4)-(phenyl) thiosemicarbazone [HL3]} were synthesized and physico-chemically characterized. All complexes are assigned octahedral geometries on the basis of spectral studies. The ligands deprotonate and coordinate by means of pyridine nitrogen, azomethine nitrogen, and thiolate sulfur atoms. The single crystal X-ray structures of HL3 and two nitrate compounds are discussed. The structural studies corroborate the spectral characterization.
Glucoamylase was immobilized on acid
activated montmorillonite clay via two different procedures
namely adsorption and covalent binding. The
immobilized enzymes were characterized by XRD,
NMR and N2 adsorption measurements and the
activity of immobilized glucoamylase for starch
hydrolysis was determined in a batch reactor. XRD
shows intercalation of enzyme into the clay matrix
during both immobilization procedures. Intercalation
occurs via the side chains of the amino acid residues,
the entire polypeptide backbone being situated at the
periphery of the clay matrix. 27Al NMR studies
revealed the different nature of interaction of enzyme
with the support for both immobilization techniques.
N2 adsorption measurements indicated a sharp drop in
surface area and pore volume for the covalently bound
glucoamylase that suggested severe pore blockage.
Activity studies were performed in a batch reactor. The
adsorbed and covalently bound glucoamylase retained
49% and 66% activity of the free enzyme respectively.
They showed enhanced pH and thermal stabilities. The
immobilized enzymes also followed Michaelis–Menten
kinetics. Km was greater than the free enzyme that was
attributed to an effect of immobilization. The immobilized
preparations demonstrated increased reusability
as well as storage stability.
Shali, N B; Sugunan, S(Springer Netherlands, 2007)
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Abstract:
Lanthana modified sol-gel titania is prepared
through particulate sol-gel route and the physico-chemical
characterizations of the prepared systems were done using
X-Ray diffration, EDX, BET surface area-pore volume measurements
and TG-DTG analysis. Benzophenone was observed
to be the sole product in the TiO2 photocatalyzed
oxidation of benzhydrol in oxygen purged acetonitrile. The
influence of various parameters, like irradiation time, amount
of catalyst, concentration of the catalyst and other factors on
the photocatalytic oxidation has been investigated. The proposed
mechanism envisages the involvement of a superoxide
radical anion.
Rare earth exchanged Na–Y zeolites,
H-mordenite, K-10 montmorillonite clay and amorphous
silica-alumina were effectively employed for the
continuous synthesis of nitriles. Dehydration of benzaldoxime
and 4-methoxybenzaldoxime were carried
out on these catalysts at 473 K. Benzonitrile (dehydration
product) was obtained in near quantitative yield
with benzaldoxime whereas; 4-methoxybenzaldoxime
produces both Beckmann rearrangement (4-methoxyphenylformamide)
as well as dehydration products
(4-methoxy benzonitrile) in quantitative yields. The
production of benzonitrile was near quantitative under
heterogeneous reaction conditions. The optimal protocol
allows nitriles to be synthesized in good yields
through the dehydration of aldoximes. Time on stream
(TOS) studies show decline in the activity of the catalysts
due to neutralization of acid sites by the basic reactant
and product molecules and water formed during the
dehydration of aldoximes.
Rapheal,P F; Manoj, E; Prathapachandra Kurup, M R(Elsevier, 2007)
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Abstract:
Ten copper(II) complexes {[CuL1Cl] (1), [CuL1NO3]2 (2), [CuL1N3]2 · 2/3H2O (3), [CuL1]2(ClO4)2 · 2H2O (4), [CuL2Cl]2 (5), [CuL2N3] (6), [Cu(HL2)SO4]2 · 4H2O (7), [Cu(HL2)2] (ClO4)2 · 1/2EtOH (8), [CuL3Cl]2 (9), [CuL3NCS] · 1/2H2O (10)} of three NNS donor thiosemicarbazone ligands {pyridine-2-carbaldehyde-N(4)-p-methoxyphenyl thiosemicarbazone [HL1], pyridine-2-carbaldehyde-N(4)-2-phenethyl thiosemicarbazone [HL2] and pyridine-2-carbaldehyde N(4)-(methyl), N(4)-(phenyl) thiosemicarbazone [HL3]} were synthesized and physico-chemically characterized. The crystal structure of compound 9 has been determined by X-ray diffraction studies and is found that the dimer consists of two square pyramidal Cu(II) centers linked by two chlorine atoms.
The quantum yields of singlet oxygen production and
lifetimes at the gas–solid interface in silica gel material
are determined. Different photosensitizers (PS) are encapsulated
in parallelepipedic xerogel monoliths (PS-SG). PS were chosen according
to their known photooxidation properties: 9,10-dicyanoanthracene
(DCA), 9,10-anthraquinone (ANT), and a benzophenone
derivative, 4-benzoyl benzoic acid (4BB). These experiments
are mainly based on time-resolved 1O2 phosphorescence detection,
and the obtained FD and tD values are compared with
those of a reference sensitizer for production, 1H-phenalen-1-
one (PN), included in the same xerogel. The trend between their
ability to oxidize organic pollutants in the gas phase and their efficiency
for production is investigated through photooxidation
experiments of a test pollutant dimethylsulfide (DMS). The
FD value is high for DCA-SG relative to the PN reference, whereas
it is slightly lower for 4BB-SG and for ANT-SG. FD is related to
the production of sulfoxide and sulfone as the main oxidation
products for DMS photosensitized oxidation. Additional mechanisms,
leading to C!S bond cleaveage, appear to mainly occur
for the less efficient singlet oxygen sensitizers 4BB-SG and ANTSG.
Manoj, Easwaran potti; Prathapachandra Kurup, M R; Fun, Hoong-Kun(Elsevier, 2007)
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Abstract:
A novel N4O coordination mode offers carbohydrazone ligands as a building block for interesting frameworks through self-assembly. Bridging mode of oxygen of bis(2-benzoylpyridine ketone) carbohydrazone (H2L) with metal centers facilitates the formation of the macrocyclic molecular square [Zn(HL)]4(BF4)4 · 10H2O, offers wide range of applications for carbohydrazones.
Seena, E B; Prathapachandra Kurup, M R(Elsevier, 2007)
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Abstract:
Three copper(II) complexes of salicylaldehyde N(4)-phenyl thiosemicarbazone (H2L1) and two copper(II) complexes of N(4)-cyclohexyl thiosemicarbazone (H2L2) have been synthesized and characterized by different physicochemical techniques like magnetic studies and electronic, infrared and EPR spectral studies. The complexes View the MathML source and [(CuL2)2] (4) having dimeric structure. The thiosemicarbazones bind to the metal as dianionic ONS donor ligand in all the complexes, except in the complex [Cu(HL1)2] · H2O (2). In complex 2, the ligand moieties are coordinated as monoanionic (HL−) ones. Two of the complexes [CuL1dmbipy] · H2O (3) and [CuL2dmbipy] (5) have been found to possess the stoichiometry [CuLB], where B = 4,4′-dimethyl-2,2′-bipyridine (dmbipy). The coordination geometry around copper(II) in 5 is trigonal bipyramidal distorted square based pyramidal (TBDSBP), as obtained by X-ray diffraction studies.
Sreesha, Sasi; Prathapachandra Kurup, M R; Suresh, E(Springer, January 1, 2007)
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Abstract:
The cobalt(III) complex, [Co(L)2(N3)2]2(ClO4)2, L being a Schiff base N-[phenyl(pyridin-2-yl)methylene]aniline has been synthesized and the crystal structure determined using X-ray crystallography. The complex crystallizes in triclinic system, space group P-1 with unit cell parameters a=10.9367(9) , b=18.0817(17) , c=20.1629(16) , α=111.341(2), β=91.622(2), γ=107.5030(10), V=3499.1(5) 3 and Z=2. It crystallizes with two independent molecules in the asymmetric unit. The two cobalt atoms are hexa-coordinate and have a distorted octahedral geometry, satisfied by four nitrogen atoms from two molecules of the Schiff base and two nitrogen atoms from the monodentate azide group. The perchlorate ions are non-coordinating.
Mohammed Yusuff, K K; Sridevi, N; Pearly Sebastian, C(Wiley InterScience, January 9, 2007)
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Abstract:
Ruthenium(III) complexes of the Schiff bases
formed by the condensation of polymer bound aldehyde and
the amines, such as 1,2-phenylenediamine (PS-opd), 2-aminophenol
(PS-ap), and 2-aminobenzimidazole (PS-ab) have been
prepared. The magnetic moment, EPR and electronic spectra
suggest an octahedral structure for the complexes. The complexes
of PS-opd, PS-ap, and PS-ab have been assigned the
formula [PS-opdRuCl3(H2O)], [PS-apRuCl2(H2O)2], [PS-ab-
RuCl3(H2O)2], respectively. These complexes catalyze oxidation
of catechol using H2O2 selectively to o-benzoquinone. The catalytic activity of the complexes is in the order [PS-ab-
RuCl3(H2O)2] . [PS-opdRuCl3(H2O)] [PS-apRuCl2(H2O)2].
Mechanism of the catalytic oxidation of catechol by ruthenium(
III) complex is suggested to take place through the formation
of a ruthenium(II) complex and its subsequent oxidation
by H2O2 to the ruthenium(III) complex.
Vanadia/ceria catalysts (2–10 wt% of V2O5) were prepared by wet impregnation of ammonium metavanadate in oxalic acid solution. Structural characterization was done with energy dispersive X-ray analysis (EDX), powder X-ray diffraction (XRD), BET surface area measurements, FT-IR spectroscopy and nuclear magnetic spectral analysis (51V MASNMR). XRD and 51V MASNMR results show highly dispersed vanadia species at lower loadings and the formation of CeVO4 phase at higher V2O5 loading. The catalytic activity of catalysts was conducted in liquid phase oxidation of ethylbenzene with H2O2 as oxidant. The oxidation activity is increased with loading up to 8 wt% V2O5 and then decreased with further increase in V2O5 content to 10 wt%. Different vanadia species evidenced by various techniques were found to be selective towards ethylbenzene oxidation. The CeVO4 formation associated with increased concentration of vanadia on ceria results the production of acetophenone along with 2-hydroxyacetophenone.
Sugunan, S; Binitha, N N(Journal of Applied Polymer Science,Wiley InterScience, March 16, 2007)
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Abstract:
In situ polymerization of aniline is done
inside the pillared clay matrix. The nonswellable pillared
clay confined matrix allows efficient polymerization that
leads to nanofibrous morphology. As a result high polymer
order and crystallinity is attained and is evident from
XRD patterns. The strong interaction between the clay
layers and polyaniline (PANI) is understood from FTIR and DRS spectra. Additionally these analytical results suggest that the prepared PANI is in the doped state. The
PANI/pillared clay nanocomposite formation gives additional
thermal stability to the polymer backbone and is clear from the DTG curves.
Sreekumar, K; Sudheesh Kumar, K(Taylor & Francis, June 1, 2007)
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Abstract:
Various polyurethanes containing photoactive bis(azo) and bis(o-nitrobenzyl)
groups in the main chain were synthesized by polyaddition reactions of diols such
as bis(4-hydroxyphenylazo)-2,20-dinitrodiphenylmethane, 4-hydroxy-3-methylphenylazo-
40-hydroxyphenylazo-2,20-dinitrodiphenylmethane and bis(4-hydroxy-3-
methylphenylazo)-2,20-dinitrodiphenylmethane with hexamethylene di-isocyanate
(HMDI), in dimethyl acetamide (DMAc) in the presence of di-n-butyltin dilaurate
(DBTDL) as catalyst. All of them were characterized by IR, UV-vis, 1H NMR and
13C NMR spectra and also by thermogravimetric analysis (TGA), differential scanning
calorimetry (DSC) and gel permeation chromatography (GPC).
Description:
International Journal of Polymeric Materials, 58:160–166, 2009
Kumar,K G; Augustine,P; John,S(Department of Applied Chemistry, June 21, 2007)
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Abstract:
A novel electrochemical sensor has been developed for the determination of nimesulide.
The sensor is based on the NIM- molybdophosphoric acid (MPA) as the electroactive
material in PVC matrix in presence of bis(2-ethyl hexyl) phthalate (BEP) as a
plasticizer. The sensor showed a fast, stable, near Nernstian response for 1 × 10-2 –1 ×
10-6 M NIM over the pH range 5 – 8 with a slope 55.6 ±0.5m V/decade and the response
time is < 45 s. Selectivity coefficient data for some common ions show negligible
interferences. The sensor was successfully applied for the determination of NIM in
tablet and the results obtained are in good agreement with those obtained by the official
method.
The effect of chromium doping on methylene
blue sensitized Poly (vinyl alcohol)/Acrylamide was carried
out by varying the ratios of Ammonium dichromate
and methylene blue. In the case of films without ammonium
dichromate, the diffraction efficiency was found to
decrease on storage. On chromium doping the storage life
was improved. Interestingly, a self-enhancement in efficiency
was observed for a particular ratio of methylene
blue and ammonium dichromate.
Three enzymes, α-amylase, glucoamylase and invertase, were immobilized on acid activated montmorillonite K 10 via two independent techniques, adsorption and covalent binding. The immobilized enzymes were characterized by XRD, N2 adsorption measurements and 27Al MAS-NMR spectroscopy. The XRD patterns showed that all enzymes were intercalated into the clay inter-layer space. The entire protein backbone was situated at the periphery of the clay matrix. Intercalation occurred through the side chains of the amino acid residues. A decrease in surface area and pore volume upon immobilization supported this observation. The extent of intercalation was greater for the covalently bound systems. NMR data showed that tetrahedral Al species were involved during enzyme adsorption whereas octahedral Al was involved during covalent binding. The immobilized enzymes demonstrated enhanced storage stability. While the free enzymes lost all activity within a period of 10 days, the immobilized forms retained appreciable activity even after 30 days of storage. Reusability also improved upon immobilization. Here again, covalently bound enzymes exhibited better characteristics than their adsorbed counterparts. The immobilized enzymes could be successfully used continuously in the packed bed reactor for about 96 hours without much loss in activity. Immobilized glucoamylase demonstrated the best results.
The title reaction was undertaken to establish the interaction between amantadine and molybdate at physiological pH. Identical FTIR spectra, TG-DTA curves and CHN data of the complexes formed from three solutions at pH 1.5, 7.4 and 8.0 indicate that the same complex was formed at all the three pHs. The FTIR spectrum shows shift in peaks corresponding to primary amino group of the drug due to coordination to molybdate. An octahedral geometry is assigned to the complex. The kinetics of the complexation has been studied at low concentrations of the reactants using UV-visible spectrophotometry. At pH 7.4, the initial rate varies linearly with [molybdate]. A plot of initial rate versus [drug] is linear passing through origin. These results indicate that the drug and molybdate react at pH 7.4 even at low concentrations. At pH 1.5, the rate increases linearly with increase in [drug] but decreases with [molybdate]. The effect of pH and ionic strength on the rate of the reaction has also been studied. A suitable mechanism has been proposed for the reaction. Reaction between the drug and molybdate even at low concentrations and the fact that the amino group of amantadine required to be free for its function as antiviral, is bound to molybdate in the complex suggests that simultaneous administration of the drug and molybdate supplements should be avoided.