Structure-property relationships in carbon electrochemistry

Abstract Carbonaceous nanomaterials can be a game changing materials in many technological fields, especially in electroanalytical applications. However, there is no consensus on the associations between the structure and electrochemical performance of these nanomaterials — even for the most basic electrochemical properties. This challenge stems from the fact that typically carbonaceous nanomaterials are obtained from various sources and not characterized properly. Therefore, to solve this deadlock we carry out systematic electrochemical characterization for a set of in-house fabricated as well as physicochemically thoroughly characterized carbon nanomaterials. We will then proceed to establish structure — performance associations for these materials. In addition, we will highlight how sensitive the electrochemical performance of these materials can be to small changes in their structural properties. Further, we emphasize the lack of correlation between electrochemical performance of electrode materials as determined using outer sphere redox (OSR) and inner sphere redox (ISR) probes the latter being highly analyte specific. As a first consistent set of electrochemical data obtained by using well characterized carbonaceous nanomaterials, this work will provide solid basis to expand the use of these materials in more complex electroanalytical as well as other applications

In-situ production of Histamine-imprinted polymeric materials for electrochemical monitoring of fish

Histamine (HIS) is a major public health problem due to its toxic properties. High levels can cause a chronic toxicity as poisoning and can be used as a signal of food hygiene. Thus, a new electrochemical sensor for HIS detection in fish is presented herein, prepared by tailoring a molecularly imprinted polymer (MIP) sensing material on a gold screen-printed electrode (Au-SPEs), in which the polymeric film was generated in-situ. This film was obtained by electropolymerizing aniline under conditions that preserved the chemical structure of HIS. Raman spectroscopy followed the chemical changes occurring at each stage of the electrode modification. The device performance was assessed by evaluating the changes in electron transfer properties of a standard redox probe [Fe(CN)6]4/[Fe(CN)6]3, by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). EIS was also used to calibrate the sensor, being the standard solutions prepared under different background media (electrolyte or a blank sample of fish extract). The device displayed a linear response from 500nM to 1mM, with a limit of detection of 210nM, and a selective behaviour against tyramine, another amine related to fish degradation. The sensing system was further employed to monitor the HIS content in samples in different time points of storage at ambient temperature. The obtained results were in agreement with the ELISA method, while offering more reproducible data. In general, the optimized sensor allowed reproducible and accurate analysis of fish samples subject to degradation and was completely assembled in-situ, in a very simple and straightforward approach. The device is low cost and suitable for further adaptation to on-site analysis, as required in food control.The authors acknowledge national funding to the National Foundation for Science and Technology (FCT), I.P., and European funding to FEDER (European Funding or Regional Development), via COMPETE2020 – POCI (operational program for internationalization and competitiveness), through projects PTDC/MAR-IO/6044/2014 and PTDC/AAG-TEC/5400/2014.info:eu-repo/semantics/publishedVersio