Ion-Imprinted Nanofilms Based on Tannic Acid and Silver Nanoparticles for Sensing of Al(III)

Electrochemically triggered self-assembly can be effectively utilized to produce electroactive materials of tailored properties for various applications, such as sensor development. Here, we present a thin sensor film based on tannic acid (TA) and silver nanoparticles (AgNPs), ionically imprinted via electrodeposition and tailor-designed for electrochemical tracing of aluminum ions, Al(III). In the first stage, the conditions for the Al(III) printing of TA films onto an indium-tin-oxide (ITO) electrode via electrodeposition are established and optimized. To form an AgNPs-containing film, AgNPs are presynthesized via a direct reduction of Ag(I) by TA resulting in TA-stabilized AgNPs (TA@AgNPs) of 1–4 nm in size, as observed by dynamic light scattering. Next, Al(III) ions are added to complex the TA molecules adsorbed on the surface of AgNPs. The resulting Al(III)/TA@AgNPs mixture is then electrodeposited onto the ITO surface by applying an anodic potential to form a film. As a result, a mesh-structured layer composed of AgNPs with TA on their surface and electrochemically cross-linked via TA–TA covalent bonds at the Al(III)-free coordination sites is formed. The introduction of Al(III) ions bonded via coordination bonds with TA and their consecutive removal using sodium fluoride formed vacancies ready to bind Al(III) ions from the analyzed solution allowing their electrochemical sensing, as monitored by cyclic voltammetry, quartz crystal microbalance, and X-ray photoelectron spectroscopy. The film was employed for sensing of neurotoxic Al(III) in human serum. A linear correlation between the current value at 0.9 V and the concentration of Al(III) was obtained in the range between 0.10 and 0.298 μM.