A rapid, simple and sensitive biosensor system for tetracycline detection is very important in food safety. In this paper we developed a label-free aptasensor for electrochemical detection of tetracycline. According to the electrochemical impendence spectroscopy (EIS) analysis, there was a linear relationship between the concentration of tetracycline and the electron transfer resistance from 10 to 3000 ng ml−1 of the tetracycline concentration. The detection limit was 10 ng ml−1 in 15 min detection duration. The prepared aptasensor showed a good reproducibility with an acceptable stability in tetracycline detection. The recoveries of tetracycline in spiked milk samples were in the range of 88.1%–94.2%. The aptasensor has sensitivity 98% and specificity of 100%.
Graphene oxide (GO) significantly affects the electrochemical activity of its composite with polyanline titanium dioxide (TiO2). In this work various composites with different GO contents have been successfully synthesized by chemical method to compare not only their material properties but also electrochemical characteristics with each other. The results of an electrochemical impedance study showed that their electrochemical property has been improved due to the presence of GO in a composite matrix. The galvanodynamic polarization explained that among them the composite with GO/Ani ratio in the range of 1–14 exhibits a better performance compared to the other due to yielding a higher current desity (280 μA cm−2). The TEM and SEM images which presented the fibres of a composite bundle with the presence of PANi and TiO2 were examined by IR-spectra and x-ray diffraction, respectively.
The results of this study of sawdust-polyaniline nanocomposite synthesized by a chemical method for Cr(VI) treatment in the environment are presented. Cr(VI) adsorption on a composite was determined by colorimetry. The results showed that sawdust-polyaniline composite synthesized with an aniline : sawdust ratio equal to 0.5 had an adsorption degree of 21.4 mg g −1 and adsorbed nearly 99% of the Cr(VI) after 2 h. The composite could be used for the adsorption of Cr(VI) from waste water. The Cr(VI) adsorption ability of the composite slightly depends on the pH value of the medium. The adsorption is fast during the first half hour and then the rate decreases.
Hybrid materials based on PbO 2 and PANi were prepared by cyclic voltammetry combined with chemical method. Firstly, PbO 2 and PbO 2 -PANi were deposited on stainless steel by cyclic voltammetry (CV) at a scan rate of 100 mV s −1 . Next, they were immersed in acidic aniline solution (0.1 M) to form new fresh PbO 2 -PANi composites. The properties of materials were characterized by x-ray diffraction, IR-spectroscopy, scanning electron microscopy and transmission electron microscopy. The electrocatalytic oxidation for methanol of all PbO 2 -PANi layers was investigated in acidic medium by potentiodynamic measure at a scan rate of 100 mV s −1 in the range of 1.4 V to 2.2 V versus Ag/AgCl/saturated KCl electrode. The obtained results indicated that the composites prepared by above combined method could significantly enhance the electrocatalysis for oxidation of methanol.
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