Salma Bilal

In situ Raman and UV-vis spectroscopic studies of polypyrrole and poly(pyrrole-2,6-dimethyl-β-cyclodextrin).

Polypyrrole (PPy) and poly(pyrrole-2,6-dimethyl-β-cyclodextrin) [P(Py-β-DMCD)] films prepared by potential cycling in aqueous acidic solutions on indium tin oxide (ITO)-coated glass and gold electrodes were studied by in situ UV-vis and Raman spectroscopy. Characteristic UV-vis and Raman bands were identified and their dependencies on the electrode potential have been discussed. Spectroelectrochemical results reveal differences both in the position of the spectral bands and their potential dependence for PPy and P(Py-β-DMCD) films indicating interactions between polymer chains and CDs during electropolymerization process. The films were also characterized by cyclic voltammetry and FT-IR spectroscopy.

A Spectroelectrochemical Study of Homo-/Co-oligomerization and Homo-/Copolymers of o-Phenylenediamine and o-Toluidine

Results of in situ UV-visible (UV/vis) spectroelectrochemical studies of the electro-oxidation of o-phenylenediamine (OPD), o-toluidine (OT), and their mixtures, as well as the redox activity of the obtained polymer films, performed in an aqueous acidic solution at an indium-doped tin oxide-coated glass electrode, are reported. UV-vis spectra recorded at different time intervals during the electrolysis of mixed solutions, containing a constant concentration of OT and various OPD concentrations in the feed, are different from those obtained with single monomer solutions. A band at λ = 497 nm was assigned to the head-to-tail mixed dimer/oligomer resulting from the cross reaction between OPD and OT cation radicals. At lower OPD feed concentration this band appears as the major band. The dependence of the spectral characteristics of the copolymer films on the OPD feed concentration was deduced. The UV-vis spectra of the copolymers reveal that the copolymer backbone probably consists of a mixture of copolymer chains with different monomer contents and has a significant number of block segments. Fourier transform infrared spectral analysis of the copolymers suggests the presence of both OPD and OT units and thus the formation of a copolymer during the electrolysis of mixed solutions of OPD and OT.

New natural urease inhibitors from Ranunculus repens

Phytochemical investigations on the chloroform and ethyl acetate soluble fractions of the roots of Ranunculus repens led to the isolation of methyl 3,4,5-trihydroxybenzoate 1, R(+)- 4-methoxydalbergione 2 and R(+)-dalbergiophenol 3. The structures of these compounds were established through spectral studies including 1D and 2D NMR experiments and by comparison with literature data. These compounds showed potent inhibitory activity against urease.

Synthesis and Characterization of Processable Polyaniline Salts

Polyaniline (PANI) is one of the most promising candidates for possible technological applications. PANI has potential applications in batteries, anion exchanger, tissue engineering, inhibition of steel corrosion, fuel cell, sensors and so on. However, its insolubility in common organic solvents limits its range of applications. In the present study an attempt has been made to synthesize soluble polyaniline salt via inverse polymerization pathway using benzoyl peroxide as oxidant and dodecylbenzenesulfonic acid (DBSA) as dopant as well as a surfactant. A mixture of chloroform and 2-butanol was used as dispersion medium for the first time. The influence of synthesis parameters such as concentration of aniline, benzoyl peroxide and DBSA on the yield and other properties of the resulting PANI salt was studied. The synthesized PANI salt was found to be completely soluble in DMSO, DMF, chloroform and in a mixture of toluene and 2-propanol. The synthesized polymer salt was also characterized with cyclic voltam-metry, SEM, XRD, UV-Vis spectroscopy and viscosity measurements. TGA was used to analyze the thermal properties of synthesized polymer. The extent of doping of the PANI salt was determined from UV-Vis spectra and TGA analysis. The activation energy for the degradation of the polymer was calculated with the help of TGA.

Systematic Analysis of Poly(o-aminophenol) Humidity Sensors

A thin film of poly(o-aminophenol), POAP, has been used as a sensor for various types of toxic and nontoxic gases: a gateway between the digital and physical worlds. We have carried out a systematic mechanistic investigation of POAP as a humidity sensor; how does it sense different gases? POAP has several convenient features such as flexibility, transparency, and suitability for large-scale manufacturing. With an appropriate theoretical method, molecular oligomers of POAP, NH and O functional groups and the perpendicular side of the polymeric body, are considered as attacking sites for humidity sensing. It is found that the NH position of the polymer acts as an electrophilic center: able to accept electronic cloud density and energetically more favorable compared to the O site. The O site acts as a nucleophilic center and donates electronic cloud density toward H2Ovap. In conclusion, only these two sites are involved in the sensing process which leads to strong intermolecular hydrogen bonding, having a 1.96 Å bond distance and ΔE ∼ −35 kcal mol–1. The results suggest that the sensitivity of the sensor improved with the oxidization state of POAP.

Effect of High Temperature on the Electrochemical and Optical Properties of Emeraldine Salt Doped with DBSA and Sulfuric Acid

A comprehensive study of thermally treated polyaniline in its emeraldine salt form is presented here. It offers an understanding of the thermal stability of the polymer. Emeraldine salt was prepared by a novel emulsion polymerization pathway using dodecylbenzene sulfonic acid and sulfuric acid together as dopants. The effect of temperature and heating rate on the degradation of this emeraldine salt was studied via thermogravimetric analysis. The thermally analyzed sample was collected at various temperatures, that is, 250, 490, 500, and 1000°C. The gradual changes in the structure of the emeraldine salt were followed through cyclic voltammetry, Fourier transform infrared spectroscopy, and ultraviolet-visible spectroscopy. Results demonstrate that emeraldine salt shows high thermal stability up to 500°C. This is much higher working temperature for the use of emeraldine salt in higher temperature applications. Further heat treatment seems to induce deprotonation in emeraldine salt. Cyclic voltammetry and ultraviolet-visible spectroscopy revealed that complete deprotonation takes place at 1000°C where it loses its electrical conductivity. It is interesting to note that after the elimination of the dopants, the basic backbone of emeraldine salt was not destroyed. The results reveal that the dopants employed have a stability effect on the skeleton of emeraldine salt.

Insights into the factors responsible for curative effects of Aab-E-Shifa Spring Hasan Abdal (Pakistan)

Springs are the gifts of nature on the earth as they contribute about eighty essential nutrients that are involved in more than 7000 enzymatic processes in the human body. European balneologists have recommended spring mineral waters for different therapeutic applications. In the present investigation, Aab-e-Shifa (Punjab Pakistan) spring water was analyzed due to its therapeutic behavior in the healing of various skin diseases via atomic absorption spectroscopy (AAS). It was found that besides other important minerals (Ca, Mg, K, and Na), the spring water contains the most significant antioxidant, i.e., Zn which is probably one of the major features of the curative behavior of Aab-e-Shifa. Other trace elements (Cr, Cd, Ni, Mn, Fe, and Cu) were also found to be present in the spring water under the permissible limits of various national and international organizations.