Indirect Nano-sensing approach: A universal potentiometric silver ion selective sensor for inline quantitative profiling of the kinetics and thermodynamics of formation and decay of silver nanoparticles

Indirect Nano-sensing are indispensable chemical sensory points that make use of the unique properties of nanoparticles to derive information about it to our macroscopic world. Precious Silver nanoparticles have become more attractive in many areas of healthcare and life sciences leading to massive industrial production and increase of environmental exposure which may lead to Nanotoxicity accompanied by the release of Ag⁺ ions. A reversible silver selective screen-printed electrode was fabricated, optimized, and validated. A wide linearity range of 1 × 10^-6 - 1 × 10^-2 M was obtained, with a LOD that reaches 1.5 × 10^-7 M and a typical slope of monovalent cationic compounds of 59.6 mV/decade. It showed high selectivity towards the cationic Ag⁺ ion activity in presence of the negatively charged citrate capped silver nanoparticles (Cit-AgNPs). The fabricated sensor has been used for tracking the decrease of Ag⁺ activity during the reduction of AgNO₃ with tri-sodium citrate during the Bottom-up synthesis of Cit-AgNPs at different temperature (60, 70 and 80 °C). The kinetic parameters (Activation energy (E_a) and Reaction rate (K)) and the thermodynamic characteristics (free activation energy (ΔG), entropy (ΔS), enthalpy (ΔH)) have been calculated. Furthermore, it has been used for tracking the release of Ag+ during the spontaneous and stimulated decay of Cit-AgNPs. The present work could be a junction between nanotechnology and recent advances in design of a reproducible, portable real-time analyzer for in-process monitoring of the production of Cit-AgNPs and its environmental hazards with many advantages in comparison to the reported techniques in terms of portability, simplicity, cost-efficient, fast inline tracking, no sampling, real-time profiles at high temperatures and it does not need professional operators.