Sonochemical synthesis of novel thermo-responsive polymer and tungsten dioxide composite for the temperature-controlled reversible "on-off" electrochemical detection of ß-Blocker metoprolol.

Thermo-responsive polymer nanocomposite based on poly (styrene-co-N-isopropylacrylamide) hybrid tungsten dioxide (WO2@PS-co-PNIPAM) was synthesized by a facile ultrasonic irradiation (Frequency; 20 kHz, power; 180 W, calorimetrically determined power; 5.73 W in the bath, and Type; probe) method in the presence of water as inisolv. The as-synthesized WO2@PS-co-PNIPAM modified glassy carbon electrode (WO2@PS-co-PNIPAM/GCE) was acting as a reversibly switched detection for the electrooxidation of metoprolol (MTP), with the thermal stimuli response of the PNIPAM. In below lower critical solution temperature (LCST), the PS-co-PNIPAM expanded to embed the electroactive sites of WO2, and the MTP could not proceed via the polymer to attain electronic transfer, indicating the "off" state. Rather, in above LCST, the PS-co-PNIPAM shrank to reveal electroactive sites and expand cyclic voltammetric background peak currents, the MTP was capable to undergo electro-oxidation reaction usually and produce the response current, indicating "on" state. Additionally, the proposed sensor had excellent sensitivity (2.21 µA µM-1 cm-2), wide dynamic range (0.05-306 µM), and a low limit of detection of 0.03 µM for MTP. Intriguingly, the fabricated sensor demonstrates the good selectivity towards the detection of MTP among the possible interfering compounds. Eventually, the WO2@PS-co-PNIPAM/GCE has been utilized in the analysis of MTP in human blood serum samples.