Paper-Derived Carbon Electrodes, a Versatile Option to Develop Electrochemical Sensors

Abstract

Carbon-based materials are particularly well-suited for electroanalytical applications due to their distinct properties, such as high chemical stability, large electroactive areas, wide electrochemical potential window in aqueous solutions, low electrical resistance, rich surface chemistry, and activity towards a variety of redox reactions. While carbon electrodes can be produced via thermal decomposition of gaseous hydrocarbons followed by their surface-induced recombination, this method is not cost-effective and suffers from both low efficiency (~20%) and limited selectivity towards graphitic forms. Alternatively, carbon electrodes can be developed via pyrolytic treatment of non-volatile substrates. This approach yields carbon materials that are rich in graphitic phases and provides researchers a much richer selection of starting materials and source-to-product efficiencies ~70%. Our team has applied this approach to develop several optically transparent carbon electrodes and has described a method for fabricating carbon electrodes by pyrolysis of paper, using a tube furnace and under a mild reducing atmosphere. The resulting electrodes not only feature the properties of traditional carbon materials but also preserve the 3D structure of the starting material, are mildly hydrophobic, and offer a wide electrochemical window and can be patterned using laser engraving. Moreover, the process also enables the incorporation of metallic nanoparticles within the structure of the material (by pyrolyzing paper pre-soaked in a solution containing the selected cation), significantly improving the conductivity of the material. Thus, this presentation will provide a brief summary of the reactions leading to the fabrication of these substrates as well as discuss the most recent applications towards their use as sensors in microfluidic devices.Special emphasis will be placed on the use of these electrodes for the detection of S. aureus, application that required the modification of the material with a thin layer of sputtered gold (that minimizes lateral resistivity and significantly improves the electron transfer process) and with chitosan (used as a binder to offer flexibility). This biosensor was controlled using a custom-built potentiostat (via a wireless connection), which was used to detect the presence of the bacteria via the oxidation of the ferrocyanide (produced by the bacteria’s respiration cycle) in the presence of mannitol.More information about the group can be found in our web site scienceweb.clemson.edu/uacl/