Sargassum coriifolium seaweed derived sub-micro sphere carbon for simultaneous electrochemical detection of hydroquinone and catechol: Mechanistic and kinetic studies

In this work, Sargassum coriifolium seaweed was used to synthesize sub-micro sphere carbon (SMSC). The SMSCmodified glassy carbon electrode (SMSC/GCE) has been fabricated and employed to detect hydroquinone (HQ) and catechol (CT) simultaneously. Through scanning electron microscopy and transmission electron microscopy analysis, the sub-micro spherical morphology of the SMSC has been confirmed. The graphitic structure of SMSC was confirmed by X-ray diffraction analysis. The structural defect was studied via Raman spectroscopy. In addition, cyclic voltammetry and electrochemical impedance spectroscopy were studied to characterize the electrochemical performance of the SMSC/GCE. From quantitative analysis, the linear concentration range of 10-200 mu M and lower detection limits of 43 nM and 24 nM were observed for HQ and CT, respectively. Different kinetic parameters have been studied to know the underlying chemistry of SMSC/GCE. Heterogeneous charge transfer constants (k(s)) were found to be 0.22 s(-1) (HQ) and 0.30 s(-1) (CT). Also charge-transfer coefficient (alpha) were calculated as 0.50 and 0.51 for HQ and CT respectively. Moreover, free energy functions (Delta G) for both HQ (-3.47 kJ mol(-1)) and CT (-26.63 kJ mol(-1)) were derived to evaluate the feasibility and spontaneity of surface reactions. Mechanistic insights of interfacial interactions are demonstrated to understand the effect of different parameters like pH, scan rate, analyte concentration, and H - bonds on redox reactions. Besides, the proposed electrochemical sensor showed excellent anti-interference capability (<5% RSD), high stability, good reproducibility, and satisfactory recovery for determining isomers in tap water.