Constructing a Sensitive Electrochemical Sensor for Tyrosine Based on Graphene Oxide-ɛ-MnO2 Microspheres/Chitosan Modified Activated Glassy Carbon Electrode

Abstract

In present study, novel graphene oxide (GO)-ɛ-MnO2 microspheres with homogeneous flaky texture were synthesized by a precursor conversion method and bound to activated glassy carbon electrodes (GCE) by using chitosan (CS), a fixing agent, to fabricate a facile and sensitive electrochemical sensor for the determination of tyrosine (Tyr). Adding the electrochemical pretreatment to glassy carbon electrode was conducive to the increase of surface concentrations of C-O functional groups and generating rough surface on the modified electrode, thus improving the electrochemical performance compared with that of untreated glassy carbon electrode. The proposed electrochemical sensor exhibited high sensing performance toward Tyr. Scanning electron microscopy showed that GO-ɛ-MnO2 microspheres were well mixed with CS and well dispersed on the modified electrode surface, with uniform morphology and size distribution. The experimental conditions were optimized, under which the sensor showed a linear proportional response to Tyr in a wide determination range from 0.02 to 20.0 μM with a detection limit (S/N = 3) of 8.3 nM. Moreover, GO-ɛ-MnO2 microspheres/CS/activated GCE was successfully applied to detect Tyr in milk samples and real dried blood spots samples, giving satisfactory results.