Highly selective electrochemical sensing of hydroquinone and catechol using Co nanoparticles anchored on N-doped carbon nanotube hollow sphere.

BACKGROUND

Hydroquinone (HQ) and catechol (CC), two important isomers with similar structures, are highly toxic, often coexisting, and impeding each other in the simultaneous detection. Electrochemical technique provides a promising alternative toward the quantification of HQ and CC, due to its inherent advantages in terms of highly sensitive reaction, ease of monitoring, low-cost, simplicity and quick response. Development of a sensing material with outstanding electrocatalytic capabilities and its utilization for the fabrication of an electrochemical sensor for highly selective monitoring of HQ and CC is of great significance.

RESULTS

In this study, a novel hierarchical nanostructure is fabricated where Co nanoparticles are anchored on N-doped carbon nanotube hollow sphere (Co/HNC) through the pyrolysis of ZIF-67@ZIF-8 hollow microsphere. On the Co/HNC modified electrode two well-defined and distinguishable peaks are displayed, resulting from electrochemical oxidation of both isomers. As an electrochemical sensor, the recorded peak current displays a linear relationship to the concentration of both HQ and CC from 0.1 to 100 μM under optimal conditions, coupled with their low detection limit of 23 nM and 37 nM, respectively. The probable application of this sensing platform was also checked for the detection of HQ and CC in real samples (e.g., lake water, tap water, detergents, ointment and orange juice), showing outstanding recovery rates. Moreover, simultaneous analysis of HQ and CC exhibited high reproducibility, selectivity and long-term stability.

SIGNIFICANCE

As a highly efficient electrocatalyst, the unique hollow and porous microsphere structure of Co/HNC affords abundant active sites, short ion diffusion path, outstanding electronic conductivity and high electrocatalytic activity, thereby certifying excellent sensing capability for these two important isomers. This study thus efficiently explores the advances of metal/NC with hollow structure for the formation of selective dihydroxybenzene electrochemical sensors.