Jinqing Kan

Energy density and IR spectra of polyaniline synthesized electrochemically in the solutions of strong acids

The electrochemical polymerization of aniline in fluoboric acid, hydrochloric acid, perchloric acid, sulphuric acid and nitric acid was carried out at a constant potential of 0.75 V (vs. SCE). The conductivity of polyaniline synthesized in fluoboric acid is the largest and that synthesized in nitric acid is the smallest among the above acids used for the polymerization of aniline. The conductivity of polyaniline synthesized in sulphuric acid is a little higher than that synthesized in nitric acid. Based on the results from the constant current charge–discharge process, the order of the energy density of polyaniline synthesized in the various acids is as follows: EHBF4>EHCl>EHClO4>EH2SO4>EHNO3. This result is similar to the redox charge of polyaniline from the cyclic voltammograms of polyaniline obtained in various acids at the same polymerization charge. The absorption peaks of BF4−, ClO4−, NO3− and SO42− doped in polyaniline are observed in the IR spectra. There is a relationship between the relative intensity of the absorption peaks of the benzene and quinone rings to that of the doped anion, i.e., the relative intensity of absorption peaks in IR spectra decreases with increasing conductivity of polyaniline.

The effect of salts on the electrochemical polymerization of aniline

Abstract Aniline is electrolysed by repeated potential cycling between 0 and 1.1 V (versus SCE); a current plateau instead of a current peak is observed on the I-E curve for the first cycle during electrolysis of aniline in aqueous acid solution in the presence of NaCl. The occurrence of the current plateau plays an important role in extending the potential range of electrolysis of aniline at a high rate. The polymerization rate of aniline in a solution containing a given HCl concentration increases with increasing concentration of sodium chloride; the potential range of the intermediate generated at the disk electrode is also extended with increasing concentration of NaCl. The potential necessary for the formation of the soluble intermediate is at least 0.75 V. The hydrochloric acid concentration necessary for an autocatalytic polymerization of aniline decreases from 0.6 to 0.4 M in the presence of NaCl. The conductivity of polyaniline prepared in a solution containing 0.2 M aniline, 0.4 M HCl and 1 M NaCl is about 30 times higher than that of polyaniline prepared in a solution containing 0.2 M aniline and 0.4 M HCl. The oxidation potential of aniline in the presence of the salts shifts toward negative potentials, depending on the ionic radius of cations and the concentration of the different salts.

The galactose biosensor based on microporous polyacrylonitrile

A galactose biosensor is obtained by immobilizing galactose oxidase (GAO) in a microporous polyacrylonitrile (PAN) thin film. The effects of pH, potential and temperature on response current are studied. The optimum pH and apparent activation energy of enzyme-catalyzed reaction are 7.1 and 31.1 kJ mol−1, respectively. The response current of the biosensor increases linearly with the increasing galactose concentration from 0.02 to 1.60 mmol dm−3. The Michaelis–Menten constant value (Kmapp) is 12.15 mmol dm−3. The biosensor shows good operational stability and reproducibility. The galactose biosensor is characterized with cyclic voltammogram, FTIR and UV-Vis.

Synthesis, Characterisation, and Conductive Superparamagnetism Studies of γ-Fe2O3/Polyaniline-Levodopa Composites

γ-Fe2O3/polyaniline–levodopa (γ-Fe2O3/PANI–levodopa) composites were prepared using γ-Fe2O3 and levodopa as dopants and ammonium persulfate as oxidant. The composites were characterised by Fourier transform infrared spectra and confirmed that the γ-Fe2O3 and levodopa were doped into the PANI chain. A transmission electron microscopy study revealed that the size of the γ-Fe2O3 was of the order of 10 nm, whereas the composite size was of the order of 25 nm; furthermore, it was observed that the PANI–levodopa chain was intercalated to form a core shell of γ-Fe2O3. Cyclic voltammetry and magnetisation studies showed that the γ-Fe2O3/PANI–levodopa composites had both electrochemical activity and conductive superparamagnetism, so these composites may be well suited for chemotherapy drugs.

Synthesis and characterisation of PANI–Co in presence of magnetic field

Abstract Polyaniline–Co (PANI–Co) was synthesised using peroxydisulphate as an oxidant in a solution containing 0·1 mol L–1 aniline and 0·5 mol L–1 HCl and adequate CoCl2.6H2O in the applied magnetic field. The electron paramagnetic resonance spectrum displayed that there were unpaired electrons in PANI–Co, the spin density of which was 6·903 6 1019 spins/g. The conductivity of PANI–Co synthesised under magnetic field was 0·728 S cm–1. The relationship between magnetisation and applied magnetic field showed that the PANI–Co had soft ferromagnetic property at room temperature. The saturation magnetisation and the coercive force of the PANI–Co were 6·6 emu g–1 (electromagnetic unit per gram) and 48 Oe, respectively. The UV-Vis and Fourier transform infrared spectra implied that there was the interaction between Co2+ and PANI chains but the structure of backbone chains of PANI–Co hardly changed compared with that of PANI. The results of cyclic voltammogram indicated that the ferromagnetic PANI–Co film was of excellent electrochemical activity.