# Polymer Films of 2-(Azulen-1-yldiazenyl)-5-(thiophen-2-yl)-1,3,4-thiadiazole: Surface Characterization and Electrochemical Sensing of Heavy Metals

## TL;DR

This paper introduces a new polymer film that can detect lead in water with high sensitivity, potentially useful for environmental monitoring.

## Contribution

A novel redox-active polymer film is developed for highly sensitive lead detection in aqueous solutions.

## Key findings

- The polymer films show high affinity for lead ions in aqueous solutions.
- The detection limit for Pb(II) is below 10−8 M in non-optimized conditions.
- The films are suitable for use in portable environmental monitoring systems.

## Abstract

This work introduces 2-(azulen-1-yldiazenyl)-5-(thiophen-2-yl)-1,3,4-thiadiazole (L) as a functional monomer capable of forming stable, redox-active films with high affinity for lead in aqueous solutions. L was synthesized and characterized using physical chemical methods and electrochemistry. Polymer films of L were prepared through oxidative electro polymerization on glassy carbon electrodes in L solutions in 0.1 M TBAP in acetonitrile. They were characterized through electrochemistry. The surface of chemically modified electrodes (CMEs) prepared through controlled potential electrolysis (CPE) at variable concentrations, potentials, and electric charges was characterized through scanning electron spectroscopy, atomic force microscopy, and Raman spectroscopy, which confirmed the films’ formation. Electrochemical sensing of the films deposited on these CMEs was tested with respect to heavy metal (HM) ion analysis in aqueous solutions to obtain sensors for HMs. The obtained CMEs presented the best characteristics for the recognition of Pb among the investigated HMs (Cd, Pb, Cu, and Hg). Calibration curves were obtained for the analysis of Pb(II) in aqueous solutions, which allowed for the estimation of a good detection limit of this cation (<10−8 M) for non-optimized CMEs. The resulting CMEs show promise for deployment in portable environmental monitoring systems, with implications for public health protection and environmental safety.