Acidity/basicity, electron donor properties and catalytic activity of sulphate modified stannic oxide

The surface electron donor properties of sulphate modified stannic oxide have been determined from the adsorption of electron acceptors of various electron affinities on the oxide surface. The acid base properties of stannic oxide have been determined by titration method using Hammett indicators. Catalytic activities of the oxide for esterification of acetic acid using n-butanol.reduction of cyclohexanone in 2-propanol and oxidation of cyclohexanol with benzophenone have been studied. The data have been correlated with the surface electron donor properties of these oxides. The activity for reduction and oxidation decreases and that for esterification reaction increases on modification with sulphate ion. It has heen found that electron donating capacity decreased when stannic oxide was modified with sulphate ion.

Acidity and catalytic activity of rare earth modified Al/Zr pillared clays

The pillared montmorillonite has been prepared by exchanging Na+ in the interlayer of montmorillonite with Al hydroxy cation followed by calcination. Pillared clays are also prepared after exchanging Na' ions with Ce, La, Sm-ions and then pillarcd with aluminium oxides, The surface characterisation of the prepared catalysts has been done using XRD and surface area measurements. To probe the acidic property of the system, temperature programmed desorption (TPD) of NH, has been done. Toluene alkylation by benzyl chloride has been carried out for the evaluation of catalytic activity. The most active system is found to be mixed Al/Zr pillarcd montrnorillonite.

Acidity/basicity, electron donor properties and catalytic activity of sulphate modified ceria

The changes in surface acidity/basicity and catalytic activity of cerium oxide due to surface modification by sulphate ion have been investigated. Electron donor properties of both the modified and unmodified oxides have been studied using electron acceptors of various electron affinity values, viz. 7,7,8,8-tetracyanoquinodimethane, 2,3,5,6-tetrachloro--l, 4-benzoquinone. p-dinitrobenzene and m-dinitrobenzene in order to find out whether the increase in acidity on suphation is due to the generation of new acidic sites or they are formed at the expense of some of the basic sites. The surface acidity/basicity has been determined using a set of Hammett indicators. The data have been correlated with the catalytic activity of the oxides for esterification of acetic acid using l-butanol, reduction of cyclohexanone with 2- propanol and oxidation of cyclohexanol using benzophenone.

Catalysis by sulphated tin oxide modified with some transition metal oxides

In the present work, we have tried to evaluate systematically the surface properties of sulphated tin oxide systems modified with three different transition metal oxides viz. iron oxide, tungsten oxide and molybdenum oxide. The catalytic activities of these systems are checked and compared by carrying out some industrially important reactions such as oxidative dehydrogenation of ethylbenzene and Friedel-Crafts reactions.

Catalysis by some metal oxides modified with phosphate ions

Surface acidity of phosphate modified La2O3,CeO2 and SnO2 has been estimated by titrimetric Method using Hammett Indicators.Mixed Oxides of tin and lanthanum have also been prepared and subjected to phosphate modification.Surface characterizartion of the samples has been carried out using XRD, surface area,thermal analysis and IR spectroscopy. Phosphate content in the samples has been chemically estimated. The catalytic activity for benzylation and esterification reaction has also been investigated.

Photoinduced oxidation of benzhydrol over lanthana modified sol-gel titania

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.

Surface properties and catalytic activity of phosphate modified zirconia

Preparation and physico-chemical characterization or phosphate modified zirconia systems and their application to Friedel-Crafts benzylation and benzoylation of toluene have been reported. The influence of transition metals on the surface properties and catalytic activity has also been discussed.

Transition metal and rare earth metal modified sol-gel titania: a versatile catalyst for organic transformations

Catalysis is a mature field with extensive practical applications in today's society.indeed,the catalysis of petroleum refining,fine chemical synthesis and emission control demands the production of catalysts in bulk quantities.Future improvement of these well established processes is likely to be incremental.On the other hand,the continuous demand for new products will require additional novel and innovative processes.The need for pollution abatement and prevention also imposes new demands on catalysis, and new processes are periodically advanced for the control of emission of gases as well as for remediation processes such as the cleaning of underground waters. The number of problems where catalysis can have a big impact is constantly growing.In general,science stimulated by the technology has enriched the field of catalysis in a way that has had broad and lasting value.The thesis"Transition metal and rare earth metal modified sol-gel titania: a versatile catalyst for organic transformations" accounts the preparation and characterization studies of both transition metals and rare earth metals modified sol-gel titania and its applications in industrially useful organic reactions.

Photoemission optogalvanic studies with copper as target electrode

Photoemission optogalvanaic (POG) effect has been observed by irradiating copper target electrode, in a nitrogen discharge cell using 1.06 μm and frequency doubled 532 nm Nd:YAG laser pulse. Measurement of the nature of the variation of POG signal strength with 532 nm laser fluence confirms the two photon induced photoelectric emission from copper. However, using 1.06 μm laser pulses thermally assisted photoemission is observed.

Investigations on the Radiation Characteristics of Planar Printed UWB Antennas With Modified Ground Planes

A major challenge in the transmission of narrow pulses is the radiation characteristics of the antenna. Designing the front ends for UWB systems pose challenges compared to their narrow and wide band counterparts because in addition to having electrically small size, high efficiency and band width, the antenna has to have excellent transient response. The present work deals with the design of four novel antenna designs- Square Monopole, Semi-Elliptic Slot, Step and Linear Tapered slot - and an assay on their suitability in UWB Systems. Multiple resonances in the geometry are matched to UWB by redesigning the ground-patch interfaces. Techniques to avoid narrow band interference is proposed in the antenna level and their effect on a nano second pulse have also been investigated. The thesis proposes design guidelines to design the antenna on laminates of any permittivity and the analyzes are complete with results in the frequency and time domains.

Laser-induced Bessel beams can realize fast all-optical switching in gold nanosol prepared by pulsed laser ablation

We demonstrate the possibility of realizing, all-optical switching in gold nanosol. Two overlapping laser beams are used for this purpose, due to which a low-power beam passing collinear to a high-power beam will undergo cross phase modulation and thereby distort the spatial profile. This is taken to advantage for performing logic operations. We have also measured the threshold pump power to obtain a NOT gate and the minimum response time of the device. Contrary to the general notion that the response time of thermal effects used in this application is of the order of milliseconds, we prove that short pump pulses can result in fast switching. Different combinations of beam splitters and combiners will lead to the formation of other logic functions too.

Electrochemical studies on Metal phthalocyanines

The primary aim of these investigations was to probe the elecnuchemical and material science aspects of some selected metal phthalocyanines(MPcs).Metal phthalocyanines are characterised by a unique planar molecular structure. As a single class of compounds they have been the subject of ever increasing number of physicochemical and technological investigations. During the last two decades the literature on these compounds was flooded by an outpour of original publications and patents. Almost every branch of materials science has benefited by their application-swface coating, printing, electrophotography, photoelectrochemistry, electronics and medicine to name a few.The present study was confined to the electrical and electrochemical properties of cobalt, nickel, zinc. iron and copper phthalocyanines. The use of soluble Pes as corrosion inhibitor for aluminium was also investigated.In the introductory section of the thesis, the work done so far on MPcs is reviewed. In this review emphasis is given to their general methods of synthesis and the physicochemical properties.In phthalocyanine chemistry one of the formidable tasks is the isolation of singular species. In the second chapter the methods of synthesis and purification are presented with necessary experimental details.The studies on plasma modified films of CoPe, FePc, ZnPc. NiPc and CuPc are also presented.Modification of electron transfer process by such films for reversible redox systems is taken as the criterion to establish enhanced electrocatalytic activity.Metal phthalocyanines are p- type semiconductors and the conductivity is enhanced by doping with iodine. The effect of doping on the activation energy of the conduction process is evaluated by measuring the temperature dependent variation of conductivity. Effect of thennal treatment on iodine doped CoPc is investigated by DSC,magnetic susceptibility, IR, ESR and electronic spectra. The elecnucatalytic activity of such doped materials was probed by cyclic voltammetry.The electron transfer mediation characteristics of MPc films depend on the film thickness. The influence of reducing the effective thickness of the MPc film by dispersing it into a conductive polymeric matrix was investigated. Tetrasulphonated cobalt phthalocyanine (CoTSP) was electrostatically immobilised into polyaniline and poly(o-toluidine) under varied conditions.The studies on corrosion inhibition of aluminium by CoTSP and CuTSP and By virtue of their anionic character they are soluble in water and are strongly adsorbed on aluminium. Hence they can act as corrosion inhibitors. CoTSP is also known to catalyze the reduction of dioxygen.This reaction can accelerate the anodic dissolution of metal as a complementary reaction. The influence of these conflicting properties of CoTSP on the corrosion of aluminium was studied and compared with those of CuTSP.In the course of these investigations a number of gadgets like cell for measuring the electrical conductivity of solids under non-isothermal conditions, low power rf oscillator and a rotating disc electrode were fabricated.

Fabrication of Potentiometric Sensors for the Determination of Lanthanide Ions

In many fields such as earth science biology, environment and electronics, the knowledge about elemental distributions and chemical speciation is important. The determination of metal levels especially the toxic ones both in the environment and in biological materials are increasingly demanded by the society.Ion selective sensors have become one of the most effective ad powerful means for analytical scientists for the trace level monitoring of metal ions. The wide range of applications ,low material requirements and simplicity of analytical procedure have not only brought ion-selective electrodes in to the lime light of analytical chemistry,but have promoted their use as tools for physiologists,medical researchers,biologists,geologists,environmental protection specialists etc.Potentiometric ion-selective sensors have been developed for the determination of lanthanide ions such as La3+,Nd3+,Pr3+,Sm3+, and Gd3+.The sensors fabricated include both PVC membrane sensor and chemically modified carbon paste sensor. A set of 10 sensors have been developed. The response parameters of all the sensors have been studied and the sensors were applied as an indicator electrode in the potentiometric titration and for the determination of metal ions in real samples.