Title The Flexible Electrochemical Methadone Sensor Based on Gold Nanoparticles and Over-oxidized Poly(Thiophene) Modified Carbon Cloth Electrode Type of Research Presentation Keywords Methadone, Carbon cloth, Electrochemical sensor, Gold nanoparticles, poly(thiophene) Abstract In this study, a carbon cloth (CC) composite electrode modified by gold nanoparticles (Au NPs) and over-oxidized poly(thiophene) (p(Thp)–Ox) was prepared and applied to the detection of methadone (MET) in biological fluids. The flexible Ox–p(Thp) / Au NPs/ CC integrated electrode increased the oxidation peak current of MET 10 times according to bare CC. Oxidation peak current value of MET linearly increased with the concentration of MET in the ranges of 0.049–9.9 μM and 9.9–29.1 μM with a limit of detection of 14 nM (S/N=3). Excellent recovery results were obtained for determination of MET in spiked human blood plasma and urine samples at the modified electrode. Researchers Habib Razmi (First Researcher)، (Second Researcher)، Faezeh Shahdost-fard (Third Researcher)