Photoacoustic studies on thermal parameters of liquid crystal mixtures

Complete thermal characterization of liquid crystal mixtures in the smectic phase consisting of various relative volume fractions of cholesterol and 1-hexadecanol have been carried out using the photoacoustic technique. Thermal diffusivity values of these liquid crystal mixtures are evaluated using the open cell photoacoustic technique whereas the thermal effusivity value is measured using the conventional photoacoustic technique. From the measured values of these transient thermophysical parameters, the thermal conductivity and heat capacity of the sample under investigation are calculated. Analyses of the results show that all the thermophysical parameters depend strongly on the volume fraction of the constituents. Results are interpreted in terms of enhanced hydrogen bonding and the consequent enhancement in cohesive thermal energy transport with increasing volume fraction of 1-hexadecanol

Photoacoustic studies on thermal parameters of liquid crystal mixtures

Complete thermal characterization of liquid crystal mixtures in the smectic phase consisting of various relative volume fractions of cholesterol and 1-hexadecanol have been carried out using the photoacoustic technique. Thermal diffusivity values of these liquid crystal mixtures are evaluated using the open cell photoacoustic technique whereas the thermal effusivity value is measured using the conventional photoacoustic technique. From the measured values of these transient thermophysical parameters, the thermal conductivity and heat capacity of the sample under investigation are calculated. Analyses of the results show that all the thermophysical parameters depend strongly on the volume fraction of the constituents. Results are interpreted in terms of enhanced hydrogen bonding and the consequent enhancement in cohesive thermal energy transport with increasing volume fraction of 1-hexadecanol

Photoacoustic studies on thermal parameters of liquid crystal mixtures

Complete thermal characterization of liquid crystal mixtures in the smectic phase consisting of various relative volume fractions of cholesterol and 1-hexadecanol have been carried out using the photoacoustic technique. Thermal diffusivity values of these liquid crystal mixtures are evaluated using the open cell photoacoustic technique whereas the thermal effusivity value is measured using the conventional photoacoustic technique. From the measured values of these transient thermophysical parameters, the thermal conductivity and heat capacity of the sample under investigation are calculated. Analyses of the results show that all the thermophysical parameters depend strongly on the volume fraction of the constituents. Results are interpreted in terms of enhanced hydrogen bonding and the consequent enhancement in cohesive thermal energy transport with increasing volume fraction of 1-hexadecanol

Use of photoacoustic effect for the detection of phase transitions in liquid crystal mixtures

We report on a laser induced photoacoustic study of the nematic-to-isotropic transition in certain commercial nematic liquid crystal mixtures, namely BL001, BL002, BL032 and BL035. A simple analysis of the experimental data using the Rosencwaig–Gersho theory shows that the heat capacities of all these compounds exhibit a sharp peak as the temperature of the sample is varied across the transition region. Also, substantial differences in the photoacoustic signal amplitudes in nematic and isotropic phases have been noticed for all the mixtures. The increased light scattering property of the nematic phase may be the reason for the enhanced photoacoustic signal amplitude in this phase.

Use of photoacoustic effect for the detection of phase transitions in liquid crystal mixtures

We report on a laser induced photoacoustic study of the nematic-to-isotropic transition in certain commercial nematic liquid crystal mixtures, namely BL001, BL002, BL032 and BL035. A simple analysis of the experimental data using the Rosencwaig–Gersho theory shows that the heat capacities of all these compounds exhibit a sharp peak as the temperature of the sample is varied across the transition region. Also, substantial differences in the photoacoustic signal amplitudes in nematic and isotropic phases have been noticed for all the mixtures. The increased light scattering property of the nematic phase may be the reason for the enhanced photoacoustic signal amplitude in this phase

Use of photoacoustic effect for the detection of phase transitions in liquid crystal mixtures

We report on a laser induced photoacoustic study of the nematic-to-isotropic transition in certain commercial nematic liquid crystal mixtures, namely BL001, BL002, BL032 and BL035. A simple analysis of the experimental data using the Rosencwaig–Gersho theory shows that the heat capacities of all these compounds exhibit a sharp peak as the temperature of the sample is varied across the transition region. Also, substantial differences in the photoacoustic signal amplitudes in nematic and isotropic phases have been noticed for all the mixtures. The increased light scattering property of the nematic phase may be the reason for the enhanced photoacoustic signal amplitude in this phase.

Electrochemical Reduction and Voltammetric Determination of Metronidazole Benzoate at Modified Carbon Paste Electrode

A metalloporphyrin incorporated carbon paste sensor has been developed for the determination of metronidazole benzoate (MTZB). Zn(II) complex of 5,10,15,20-tetrakis (3-methoxy-4-hydroxy phenyl) porphyrin (TMHPP) was used as the active material. The MTZB gave a well-defined reduction peak at - 0.713V in 0.1 mol l -1 phosphate buffer solution of pH around 7. Compared with bare carbon paste electrode (CPE), the TMHPP Zn(II) modified electrode significantly enhanced the reduction peak current of MTZB as well as lowered its reduction potential. Under optimum conditions the reduction peak current was proportional to MTZB concentration over the range 1×10-3 mol1-1 to 1×10-5mol1-1. The detection limit was found to be 4.36×10-6mol1-1 . This sensor has been successfully applied for the determination of MTZB in pharmaceutical formulations and urine samples.

Photophysical and Electrochemical Investigations on Photoconducting Poly(6-tert-butyl-3,4-dihydro-2H- 1,3-benzoxazine)

Poly(6-tert-butyl-3,4-dihydro-2H-1,3-benzoxazine) was synthesized by thermally activated cationic ring opening polymerization. The structure of the polymer was confirmed by spectral and thermal studies. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) were estimated using cyclic voltammetry and optical absorption. Modulated photocurrent measurement technique was employed to study the spectral and field dependence of photocurrent. Photocurrent of the order of 1.5 micro A/m2 was obtained for polymer at a biasing electric field of 40 V/mico m.

Material Characterisation and Electro-Optical Studies of a Ferroelectric Liquid Crystal

Department of Electronics, Cochin University of Science and Technology

Synthesis and crystal structure of cobalt(III) complex with a Schiff base and azide

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.

Copper(II) complexes of N(4)-substituted thiosemicarbazones derived from pyridine-2-carbaldehyde: Crystal structure of a binuclear complex

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.

Fabrication of Electrochemical Sensors for the Determination of Pharmaceuticals

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.

Spectral studies and crystal structures of some transition metal complexes of N4-substituted semicarbazones

The present work is concentrated on the studies of two novel semicarbazones, di-2-pyridyl ketone-N4-phenyl-3-semicarbazone (HL1) and quinoline-2-carboxaldehyde-N4-phenyl-3-semicarbazone (HL2). The compositions of these semicarbazones were determined by the CHN analyses. For the characterization of these compounds we have used IR, UV and NMR spectral studies. The molecular structure of quinoline-2-carboxaldehyde-N4-phenyl-3- semicarbazone (HL2) was obtained by single crystal X-ray diffraction studies. Also, we have synthesized Zn(II), Cd(II), Cu(II), Ni(II), Co(II) and Mn(II) complexes of these semicarbazones, HL1 and HL2. These complexes were characterized by various spectroscopic techniques, magnetic and conductivity studies. We could isolate single crystals of some Zn(II) and Cd(II) compounds suitable for X-ray diffraction studies. For other complexes we could not isolate single crystals of good quality for single crystal X-ray diffraction studies.