Highly defective mesoporous carbon toward fabrication of efficient electrochemical sensors

The presence of structural defects significantly alters the properties of carbon nanostructures. The results of recent literature have confirmed that the vacancy defects can serve as favorable sites for the electron transfer as well as adsorption sites which are beneficial for fabrication of energy storage and electrochemical sensing devices. For example, improved heterogeneous electron transfer rate toward electrochemical reaction of ferrocenemethanol [1], oxygen [2], and nitrate [3] was reported at the surface of defective nanocarbon based electrodes. Also the results of theoretical efforts predicted the favorable adsorption of Li+, Na+, Ca2+ ions on the defective sites of graphene sheets [4-6]. Generally, structural defects were induced by chemical treatments and ion irradiation [7,8]. In this paper, preparation of a highly defective mesoporous carbon (DMC) via a facile mass producible method for electrochemical sensing applications was reported. The synthesis of DMC with desired structural defects was conducted using nanosilica as hard template, sucrose as a carbon source, and KNO3 as a defect causing agent. During carbonization process, the oxygen gas released from the decomposition of KNO3, which was coated on nanosillica template, reacts with carbon atoms and provides a highly defective mesopores carbon. Raman spectroscopy was used to evaluate defect density while porous structure and surface morphology of synthesized materials were investigated with N2-adsorption/desorption, XRD, SEM and TEM techniques. Cyclic voltammetry and electrochemical impedance spectroscopy studies were performed on fabricated renewable mesoporous carbon paste electrode (MCPE). The optimal effective heterogeneous rate constant for ferri/ferrocyanide redox probe at the surface of highly defective mesoporous carbon was determined as 0.42 cms-1 which is about 145, 75 and 50 fold faster than graphite, MWCNT and graphene, respectively. It is worth mentioning 403 that the obtained K0 (0.42 cmS-1) at the surface of highly defective mesoporous carbon presented in this work is higher than those of other reported carbon based electrodes such as edge plane HOPG (0.10 cmS-1), 50 SWCNT (0.003 cmS-1), 51 and glassy carbon (0.029 cmS-1) [9-11]. Moreover, the study of CVs of different redox species verified the excellent electrochemical performance of the synthesized highly defective nanocarbon. The favorable electroanalytical behavior of highly defective mesoporous carbon toward fabrication of electrochemical sensors were further explored by study the CVs of some important biological and environmental species such as ascorbic sacid, uric acid, dopamine, paracetamol, hydroquinone, and Bisphenol A. The experimental findings are valuable for design and fabrication of efficient carbon based electrochemical sensing devices.