Redox-active gold nanoparticle-encapsulated poly(amidoamine) dendrimer for electrochemical sensing of 4-aminophenol

Metal nanoparticle-encapsulated with dendrimer networks have gained enormous interest towards fabrication of various electrochemical devices, including electrochemical sensors. In this work, we have designed a redox active electrochemical sensor using ferrocene terminated poly(amidoamine) (PAA) dendrimers encapsulated with gold nanoparticles (AuNPs) for the detection of 4-aminophenol (4-AP). The redox mediator, ferrocene (as ferrocene carboxaldehyde), was covalently attached to an amine terminated third generation of PAA dendrimer through Schiff base condensation to form a stable imine bond. Thereafter, AuNPs were entrapped in the dendritic network to yield a Fc-PAA-AuNPs, which was deposited over a glassy carbon electrode (GCE) to form Fc-PAA-AuNPs/GCE. The cyclic voltammogram of 0.1 M phosphate buffer at the fabricated electrode displayed a set of distinct redox peaks with an oxidation peak at 0.427 V and reduction peak at 0.345 V corresponding to ferrocene/ferrocenium (Fc/Fc⁺) redox couple. Further, the fabricated electrode has shown prominent electrocatalytic response for the detection of 4-AP based on which an electrochemical sensor towards the determination of 4-AP has been developed. Noticeably, the newly developed electrochemical sensor has shown impressive performance towards detection of 4-AP with a linear range from 30 to 1064 μM, with a sensitivity of 87.8 μA mM⁻¹ cm⁻² and a limit of detection of 7.61 μM. Besides, the developed sensor exhibited good selectivity and excellent stability towards the detection of 4-AP. The superior efficacy of the developed sensor could be due to the covalent immobilization of Fc and effective encapsulation of AuNPs in the hyperbranched Fc terminated PAA dendritic network, which augumented their electronic conductivity as well as operational stability.