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For monitoring tilapia ( Orechromis niloticus ) freshness degree, a colorimetric method based on a copolymer of ortho -phenylenediamine and aniline, in a molar ratio of 1 to 1, was developed. The optical sensor changes color as a function of pH, therefore, it is sensitive to the presence of alkaline vapors such as the volatile amines (TVB-N) produced during fish spoilage. A kinetic approach was used to correlate the copolymer (sensor) response to the presence of ammonia, dimethylamine, and trimethylamine vapors, which are the main products generated by the bacteria during fish spoilage. The levels of TVB-N and microbial growth patterns ( Pseudomonas spp ), in specimens of tilapia fillets stored under refrigeration at 10 °C, correlated well with the color change of the copolymer, showing that after 48 h the specimen was no longer fit for human consumption. [ABSTRACT FROM AUTHOR]

Abstract: Series of polystyrene/polyaniline core–shell composites were synthesized by adding reactive surfactant anilinium dodecylsulfate (DS-AN) as the monomer of polyaniline. DS-AN conversion to polyaniline was calculated by quantitative infrared spectroscopy and thermogravimetric analysis, showing both methods small differences. Composites particle size distribution showed no clear evidence of increment in the overall composite particle diameter as function of polyaniline content; however, electron microscopy (HR mode) showed that the conductive polymer was deposited over the polystyrene cores in the form of thin coatings. Composites electrical conductivity, determined by the 4-probe technique, was in the range 10−6 to 10−2 Scm−1. The percolation–tunneling mechanism, according to the curve of conductivity (Scm−1) versus polyaniline (wt%), was the electron transfer mechanism. Finally, all the composites were electroactive, as shown by cyclic voltammetry. [Copyright &y& Elsevier]

A poly( ortho -phenylenediamine- co -aniline) copolymer is synthesized via the oxidative route, using a 1:1 M ratio of aniline to ortho -phenylenediamine ( o PDA) and ammonium persulfate as the oxidizing agent. Infrared spectroscopy indicates that the copolymer contains the functional groups typically present in polyaniline and poly( ortho -phenylenediamine); whereas UV-vis-NIR spectroscopy shows that the copolymer adopts a phenazine-type structure. Cyclic voltammetry evidences the copolymer synthesis, as a redox peak at −65 mV, different from those exhibited by polyaniline (160 mV and 600 mV) or poly( o -phenylenediamine) (−240 mV) is observed. Finally, electrochemical impedance spectroscopy and the charge/discharge test provide support to propose the copolymer application in electrodes for supercapacitors. [ABSTRACT FROM AUTHOR]