Sreekumar, K(Optical society of America, June 20, 2004)
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Abstract:
A methylene-blue-sensitized polymer blend of polyvinyl alcohol and polyacrylic acid is fabricated and
tested for holographic recording. It was found to have good characteristics such as high sensitivity,
storage stability, ease of fabrication, and environmental stability. Optimization of the ratio of polyvinyl
alcohol polyacrylic acid, the sensitizer concentration, pH, energy, diffraction efficiency measurements,
etc., have been done. pH is found to have a great influence on the recovery of the dye in this matrix.
The results of experimental investigations into the properties of this new material are reported.
Sudha Kartha, C(Optical society of America, June 20, 2004)
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Abstract:
A methylene-blue-sensitized polymer blend of polyvinyl alcohol and polyacrylic acid is fabricated and
tested for holographic recording. It was found to have good characteristics such as high sensitivity,
storage stability, ease of fabrication, and environmental stability. Optimization of the ratio of polyvinyl
alcohol polyacrylic acid, the sensitizer concentration, pH, energy, diffraction efficiency measurements,
etc., have been done. pH is found to have a great influence on the recovery of the dye in this matrix.
The results of experimental investigations into the properties of this new material are reported.
Sheeba, M; Dr. Radhakrishnan, P(Cochin University of Science and Technology, May 22, 2008)
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Abstract:
Although the main application of optical fibers are in the field of
telecommunication, optical fiber based sensors of various designs are
becoming valuable devices for wide industrial applications. The
advantages of optical fiber-based sensors include high sensitivity,
insensitivity to electromagnetic radiation; spark free, light weight and
minimal intrusiveness due to their relatively small size and deployment in
harsh and hostile environments. It has been proved that POI-7 based
sensors can be employed to detect a great variety of parameters including
temperature, humidity, pressure, refractive index etc.
The proposed thesis presented in six chapters deals with the work carried
on dye doped and undoped POF for photonic device applications such as
amplifier, laser and sensor
Description:
International School of Photonics
Cochin University of Science and Technology
Varkey,K P; Dr.Vijayakumar, K P(COCHIN UNIVERSITY OF SCIENCE AND TECHNOLOGY, August , 1999)
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Abstract:
The study on the fabrication and characterization of spray pyrolysed cadmium sulphide homojunction solar cells. As an alternative to the conventional energy source, the PV technology has to be improved. Study about the factors affecting the performance of the existing solar cells and this will result in the enhancement of efficiency of the cells. At the same time it is equally important to have R&D works on developing new photovoltaic devices and processes which are less expensive for large scale production. CdS is an important binary compound semiconductor, which is very useful in the field of photovoltaics. It is very easy to prepare large area CdS thin films. In order to fabricate thin film homojunction cadmium sulphide cells, prepared and characterized SnO2 thin film as the lower electrode, p-CdS as the active layer and n-CdS as window layer. Cadmium material used for the fabrication of homojunction solar cells is highly toxic. The major damage due to continued exposure to low levels of cadmium are on the kidneys, lungs and bones. The real advantage of spray pyrolysis process is that there is no emission of any toxic gases during the deposition. Very low concentration of the chemicals is needed in this process. The risk involved from this material is very low, though they are toxic. On large scale usage it may become necessary that the cells after their life, should be bought back by the companies to retrieve chemicals like cadmium. This will reduce environmental problem and also the material wastage
Sebastian, P J; Dr.Sathianandan, K(Cochin University Of Science And Technology, November 25, 1981)
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Abstract:
Eventhough a large number of schemes have been proposed and develoned for N9 laser ouined dye lasers the
relatively low efficiency compelled the scientists to
device new methods to improve the system efficiencs.
Energy transfer mechanism has been shown to he a convenien
tool for the enhancement of efficiency of dye lasers. Th
p resent work covers a detailed study of the performance
characteristics of a N2 laser pumped dye laser in the con—
ventional mode and also, when pumped by the energy transfer
mechanism. For .th.e present investigations a dye laser
pumped by a'N2 laser (A4200 kw peak power) was fabricated.
The grating at grazing incidence was used as the beam expanding
device; A t its best performance the system was
giving an output peak power of l5 kW for a 5 X lC"3H/l Rh—€
solution in methanol. T he conversion efficiency was 7.5;
The output beam was having 3 divergence of 2 mrad and bandwidth
o.9 A. Suitable modifications were suggested for
obtaining better conversion efficiency and bandwidth.
Description:
Department of Physics,
Cochin University Of Science And Technology
Jayaraj, M K; Dr.Girijavallabhan,C P(Cochin University of Science and Technology, June 20, 1988)
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Abstract:
This thesis contains the author's work in preparing efficient EL phosphors, the details of fabrication of low voltage operated thin film EL (TFEL) devices and DC TFEL devices. Some of the important work presented here are related to the white light emitting ZnS:Cu,Pr,Cl phosphor which can be colour tuned by changing the excitation frequency, observation of energy transfer from Cu/Ag ions to rare earth ions in ZnS:(Cu/Ag), RE,Cl phosphors, development of TFEL device which can be operated below 50V, optimization of the device parameters for long life, high brightness in terms of the active and insulating layer thicknesses, observation of dependence of threshold voltage for the onset of emission on frequency of excitation when a novel dielectric Eu2O3 film was used as insulator and the devices with multicolor emission using ZnS doped with rare earth as active layer. Characterization based on other devices based on ZnS:Sm, ZnS:Pr, ZnS:Dy and their emission characteristics are also illustrated
Description:
Department of Physics, Cochin University of Science and Technology
Anantharaman, M R; Soumya, Jose; Narayanan, T N; Senoy, Thomas; Al-Harthi, S H(IOP Publishing LTD, July 31, 2009)
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Abstract:
Two-dimensional electronic systems play a crucial role in modern electronics and offer a
multitude of opportunities to study the fundamental phenomena at low dimensional physics.
A quantum well heterostructure based on polyaniline (P) and iodine doped polyaniline (I) thin
films were fabricated using radio frequency plasma polymerization on indium tin oxide coated
glass plate. Scanning probe microscopy and scanning electron microscopy studies were
employed to study the morphology and roughness of the polymer thin films. Local electronic
density of states (LDOS) of the P–I–P heterostructures is probed using scanning tunnelling
spectroscopy (STS). A step like LDOS is observed in the P–I–P heterostructure and is
attributed to the quantum well confinement of electrons in the polymer heterostructure.
Sareena, John; Dr.Girish Kumar, K(Cochin University of Science and Technology, December , 2007)
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Abstract:
Potentiometric chemical sensors,an important class of electro-chemical sensors are widely used in pharmaceutical analysis because of its inherent advantages.The present study was aimed at fabrication of potentiometric sensors for the drugs mebendazole,pefloxacin,ambroxol,sildenafil citrate,dextro-methorphan and tetracycline.A total of 18 sensors have been developed for the determination of theses drugs.The major step in the fabrication of the sensor was the preparation of the ion association.Two types of sensors viz:PVC membrane sensor and carbon paste electode (CPE) were fabricated.The response characteristics of the different sensors fabricated were studied.Various response parameters studied include response time,selectivity and the effect of pH.The developed sensors were also employed for the determination of the drugs in pharmaceutical formulations and also for the recovery of the drug from urine samples.The selectivity studies reveal that the developed sensors are highly selective to the drug even in prescence of foreign ions.
Description:
Department of Applied Chemistry,
Cochin University of Science and Technology
Sindhu, Issac; Dr.Girish Kumar, K(Cochin University of Science & Technology, February , 2011)
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Abstract:
Voltammetric sensors are an important class of electrochemical sensors in which the analytical information is obtained from the measurement of current obtained as a result of electrochemical oxidation/reduction.This current is proportional to the concentration of the analyte.Chemically modified electrodes(CMEs) have great significance as important analytical tools for the electrochemical determination of pharmaceuticals.The modification of electrode results in efficient determination of electro-active biomolecules at very lower potential without its major interferences.The operation mechanism of CMEs depends on the properties of the modifier materials that are used to promote selectivity towards the target analytes.Modified electrodes can be prepared by deposition of various compounds such as organic compounds ,conducting polymers,metal oxides,etc. on the various electrode surfaces.The thesis presents the development ,electrochemical characterization and analytical application studies of eight voltammetric sensors developed for six drugs viz.,Ambroxol,Sulfamethoxazole,PAM Chloride, Lamivudine,Metronidazole and Nimesulide.The modification techniques adopted as part of the present work include Multiwalled Carbon Nanotube(MWCNT) based modification.Electropolymerisation and Gold Nanoparticle (AuNP) based modifications.
Description:
Dept.of Applied Chemistry,Cochin University of Science & Technology
Remalakshmy,Poduval; Girish Kumar,K(Department of applied chemistry, 2006)
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Abstract:
In this study Fabrication of Potentiometric sensors for the determination of certain metal ions, presents the synthesis and characterization of seven ionophores, their use in the fabrication of potentiometric sensors and the results and discussion of fourteen sensors developed for the determination of five transition metal ions. As part of the present investigations a total of fourteen potentiometric sensors have been developed and fabricated. A three fold approach has been taken in developing he sensors, PVC plasticized membrane sensor, carbon paste electrode and chemically modified carbon paste electrode. All the sensors are highly useful in the determination of metal ions such as manganese, nickel, copper, mercury and lead. A through analytical study has been carried out with respect to each other developed. Based on these studies, optimum conditions have been developed for the quantitative determinations of the selected metal ions using the sensors. Systematic application studies have also been carried out for all the developed sensors and the results revealed that the presently developed sensors are far superior than most of the sensors reported.
Beena, S; Dr.Girish Kumar, K(Cochin University of Science and Technology, May , 2010)
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Abstract:
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.
Description:
Department of Applied Chemistry,
Cochin University of Science and Technology
The fabrication and analytical applications of two types of potentiometric
sensors for the determination of ketoconazole (KET) are described. The
sensors are based on the use of KET-molybdophosphoric acid (MPA) ion pair
as electroactive material. The fabricated sensors include both polymer membrane
and carbon paste electrodes. Both sensors showed a linear, stable and near
Nernstian slope of 57.8mV=decade and 55.2mV=decade for PVC membrane
and carbon paste sensors respectively over a relatively wide range of KET concentration
(1×10-2-5×10-5 and 1×10-2-1×10-6). The sensors showed a fast
response time of <30 sec and <45 sec. A useful pH range of 3–6 was obtained
for both types of sensors. A detection limit of 2.96 10 5M was obtained for
PVC membrane sensor and 6.91 10 6M was obtained for carbon paste sensor.
The proposed sensors proved to have a good selectivity for KET with respect to a
large number of ions. The proposed sensors were successfully applied for the
determination of KET in pharmaceutical formulations. The results obtained
are in good agreement with the values obtained by the standard method.
Sunitha, Sabastin; Dr. M. Kailasnath(Cochin University of Science and Technology, June 12, 2015)
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Abstract:
Polymer Optical Fibers have occupied historically a place for large core flexible fibers operating in short distances. In addition to their practical passive application in short-haul communication they constitute a potential research field as active devices with organic dopants. Organic dyes are preferred as dopants over organic semiconductors due to their higher optical cross section. Thus organic dyes as gain media in a polymer fiber is used to develop efficient and narrow laser sources with a tunability throughout the visible region or optical amplifier with high gain. Dyes incorporated in fiber form has added advantage over other solid state forms such as films since the pump power required to excite the molecules in the core of the fiber is less thereby utilising the pump power effectively. In 1987, Muto et.al investigated a dye doped step index polymer fiber laser. Afterwards, numerous researches have been carried out in this area demonstrating laser emission from step index, graded index and hollow optical fibers incorporating various dyes. Among various dyes, Rhodamine6G is the most widely and commonly used laser dye for the last four decades. Rhodamine6G has many desirable optical properties which make it preferable over other organic dyes such as Coumarin, Nile Blue, Curcumin etc. The research focus on the implementation of efficient fiber lasers and amplifiers for short fiber distances. Developing efficient plastic lasers with electrical pumping can be a new proposal in this field which demands lowest possible threshold pump energy of the gain medium in the cavity as an important parameter. One way of improving the efficiency of the lasers, through low threshold pump energy, is by modifying the gain of the amplifiers in the resonator/cavity. Success in the field of Radiative Decay Engineering can pave way to this problem. Laser gain media consisting of dye-nanoparticle composites can improve the efficiency by lowering the lasing threshold and enhancing the photostability. The electric field confined near the surface of metal nanoparticles due to Localized Surface Plasmon Resonance can be very effective for the excitation of active centers to impart high optical gain for lasing. Since the Surface Plasmon Resonance of nanoparticles of gold and silver lies in the visible range, it can affect the spectral emission characteristics of organic dyes such as Rhodamine6G through plasmon field generated by the particles. The change in emission of the dye placed near metal nanoparticles depend on plasmon field strength which in turn depends on the type of metal, size of nanoparticle, surface modification of the particle and the wavelength of incident light. Progress in fabrication of different types of nanostructures lead to the advent of nanospheres, nanoalloys, core-shell and nanowires to name a few. The thesis deals with the fabrication and characterisation of polymer optical fibers with various metallic and bimetallic nanostructures incorporated in the gain media for efficient fiber lasers with low threshold and improved photostability.