Colorimetric detection of Cu (II) in water and urine samples using 2,2′-thiodiacetic acid modified silver nanoparticles

Copper is one of the important and essential elements for human health and is required for normal metabolic processes [1,2]. It plays essential functions, such as enzyme activation, energy production and dioxygen transport [3]. Nanomaterials are at the leading edge of the rapidly developing field of nanotechnology. Their unique size-dependent properties make these materials superior and indispensable in many areas of human activity [4]. Recently, Uv-vis spectrophotometry technique based on gold nanoparticles (AuNPs) and silver nanoparticles (AgNPs) have been developed to detect different analytes. This is due to their excellent optical properties and easy detection of color changes between their dispersed and aggregation states of this nanopaticles [5]. As a result, a wide number of colorimetric sensor assays have been reported using AgNPs for the detection of various analytes. A silver nanoparticle probe based on 2,2′-thiodiacetic acid (TDA) for determination of Cu (II) is proposed. The copper ions cause the aggregation of silver nanoparticles capped with TDA, while other ions do not have an effect. As a result, the color of the solution changes from yellow to brown which can be recognized using naked eye or by UV-vis spectroscopy. The limit of detection obtained was 17 nM. The ratio A570 / A393 nm is linearly correlated to the concentration of copper ion in the 0.3 to 6.0 μM range. The method was successfully applied to the determination of Cu (II) in spiked water and urine samples and gave recoveries that ranged from 97.5 to 101.1 %.