Highly defective mesoporous carbon toward fabrication of efficientelectrochemical sensors

The presence of structural defects significantly alters the properties of carbon nanostructures. Theresults of recent literature have confirmed that the vacancy defects can serve as favorable sites forthe electron transfer as well as adsorption sites which are beneficial for fabrication of energystorage and electrochemical sensing devices. For example, improved heterogeneous electrontransfer 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 oftheoretical efforts predicted the favorable adsorption of Li+, Na+, Ca2+ ions on the defective sitesof graphene sheets [4-6]. Generally, structural defects were induced by chemical treatments andion 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. Thesynthesis of DMC with desired structural defects was conducted using nanosilica as hardtemplate, sucrose as a carbon source, and KNO3 as a defect causing agent. During carbonizationprocess, the oxygen gas released from the decomposition of KNO3, which was coated onnanosillica template, reacts with carbon atoms and provides a highly defective mesopores carbon.Raman spectroscopy was used to evaluate defect density while porous structure and surfacemorphology of synthesized materials were investigated with N2-adsorption/desorption, XRD,SEM and TEM techniques. Cyclic voltammetry and electrochemical impedance spectroscopystudies were performed on fabricated renewable mesoporous carbon paste electrode (MCPE).The optimal effective heterogeneous rate constant for ferri/ferrocyanide redox probe at thesurface 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 that the obtained K0 (0.42 cmS-1) at the surface of highly defective mesoporous carbon presentedin this work is higher than those of other reported carbon based electrodes such as edge planeHOPG (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 electrochemicalperformance of the synthesized highly defective nanocarbon. The favorable electroanalyticalbehavior of highly defective mesoporous carbon toward fabrication of electrochemical sensorswere further explored by study the CVs of some important biological and environmental speciessuch as ascorbic sacid, uric acid, dopamine, paracetamol, hydroquinone, and Bisphenol A. Theexperimental findings are valuable for design and fabrication of efficient carbon basedelectrochemical sensing devices.

Keywords:

Structural defect , mesoporous carbon , electrochemical sensing , paste electrode