Facile fabrication of 17β-estradiol electrochemical sensor using polyaniline/carbon dot-coated glassy carbon electrode with synergistically enhanced electrochemical stability

Previous 17β-estradiol sensors required expensive reagents or complicated fabrication of sensing probes. In this work, a cheap, simple, and reusable electrochemical sensor based on commercially available polyaniline (PANI) and carbon dots (CDs) synthesized from iota-carrageenan was developed for the sensitive detection of 17β-estradiol. The sensor was simply prepared by drop-casting CDs/PANI composite on a glassy carbon electrode (GCE) using poly(vinylidene fluoride) as a binder. With synergistic contributions from both CDs and PANI, the CDs-PANI/GCE was much more electrochemically stable than the CDs/GCE or PANI/GCE. The CDs-PANI/GCE was sensitive to 17β-estradiol across a linear range from 0.001 to 100 μmol L^-1 with a detection limit of 43 nmol L^-1. The electrochemical measurement can be performed in 2 min and the probe can be reused for several hundred times. The CDs-PANI/GCE was selective towards 17β-estradiol against several interferences and gave excellent recovery between 94.4 and 103.7 % from real sample analysis. From intensive investigation on electron transfer process and energy levels, the oxidation reaction of 17β-estradiol occurred on the surface of CDs-PANI/GCE via favorable energy levels and dominantly surface adsorption process through π-π stacking and hydrogen bonding between 17β-estradiol and CDs/PANI. Such unique interfacial interactions also resulted in the synergistically enhanced electrochemical stability of the modified electrode.