Gum Arabic-capped silver nanoparticles for electrochemical amplification sensing of methylene blue in river water

Herein, a novel electrochemical amplification sensor is developed for detecting methylene blue (MB) using gum Arabic-capped silver nanoparticles (AgNPs) for the first time. Gum Arabic-AgNPs were fabricated via a direct chemical reduction technique using silver nitrate as an AgNPs precursor and gum Arabic as a reducing and capping agent. They were characterized using ultraviolet-visible (UV-Vis) spectrophotometry, square wave voltammetry (SWV), and transmission electron microscopy (TEM). UV-Vis and SWV results show the characteristic absorption and electrochemical oxidation peaks of the AgNPs at 431 nm and 0.18 V, respectively. Additionally, TEM images of the AgNPs show that they are spherical with an average size of 25 +/- 8 nm. An electrochemical sensor was constructed by dipping a glassy carbon (GC) electrode in gum Arabic-AgNPs for 30 min. Next, the resultant gum Arabic-AgNPs/GC electrode was incubated with a phosphate buffer solution containing MB for 10 min for detecting MB. The detection was accomplished directly via the MB monomer and polymer oxidation, and indirectly via AgNPs oxidation amplification. The amplification electrochemical sensor exhibits linear ranges of 1-20 mu g/L, 0.1-10 mg/L, and 1-15 mg/L, respectively, for AgNPs, MB monomer, and poly MB oxidation-based sensors. Moreover, the sensor was applied for the detection of MB in river water samples, with acceptable recovery values. Interestingly, the interplay between the AgNPs and MB mediators in the oxidation signal amplification of both is reported for the first time. (c) 2021 Elsevier Ltd. All rights reserved.