Background: The presence of heavy metals in water is very harmful for the environment
and the human’s health. Some heavy metals such as copper, at trace levels, are indispensable to preserve
the metabolism of the human body. The application of the electrochemical methods (potentiometric
and impedimetric) for Cu detection are simple and low cost with short detection times. One
of the most important challenges in sensors development is how to increase sensibility and the obtained
the best detection limit. The aim of this work is to investigate and compare two different types
of electrochemical (potentiometric and impedimetric) methods for detection of Cu2+ ions in aqueous
solution using chitosan-gold nanoparticles (CS-AuNPs) membrane.
Methods: CS-AuNPs membrane has been prepared by adding of AuNPs obtained using Turkevich
method to the CS dispersed in the acid acetic solution. Potentiometric and impedimetric measurements
were performed using a graphite-epoxy electrode modified by CS-AuNPs membrane in aqueous
solution in the concentration range of 10−9 to 10−1 M of Cu(NO3)2.
Results: For the first time, the relation between percolation threshold and detection limit of copper
ions has been established. The best detection limit in both methods has been observed when the concentration
of AuNPs is near the percolation threshold. Obtained results show that potentiometric
method has a detection limit of 2.36 × 10-5 and a linear response range between 2.36 × 10-5 and 4 ×
10-2 M of Cu2+. However, impedimetric method shows superior properties: detection limit ca. 10-7 M,
linear response range 10-7-10-3 M of Cu2+ ions.
Conclusion: The obtained relationship between impedance measurements and critical percolation
concentration of AuNPs are of primary importance in the design and optimization of nanocomposite
for sensor application. Our results suggest that CS-AuNPs membranes can be used for the development
of a low cost sensor for copper detection based upon potentiometric and impedimetric measurements.