A Robust Electrochemical Sensor Based on Butterfly‐shaped Silver Nanostructure for Concurrent Quantification of Heavy Metals in Water Samples

Abstract

Heavy metals in drinking water have become a severe threat to human health. Detection of heavy metals has been achieved by electrochemical sensors that are modified with complex nanocomposites; however, reproducibility of these sensors is still a big challenge when applied in commercial settings. Here, a simple, very robust, and sensitive electrochemical sensor based on a screen‐printed carbon electrode modified with butterfly‐shaped silver nanostructure (AgNS/SPCE) has been developed for the concurrent determination of cadmium (II), lead (II), copper (II), and mercury (II) in water samples. The electrochemical behavior of the modified electrodes was investigated using cyclic voltammetry and differential pulse anodic stripping voltammetry. The AgNS/SPCE showed distinct peak potentials and a significant increase in the peak currents for all heavy metals, attributed to the high electrical conductivity and electrocatalytic activity of the synthesized butterfly‐shaped AgNS. Moreover, the excellent stability and sensitivity towards simultaneous quantification of heavy metals have been obtained with detection limits of 0.4 ppb, 2.5 ppb, 7.3 ppb, and 0.7 ppb for Cd (II), Pb (II), Cu (II), and Hg (II), respectively. Besides, the constructed sensor was successfully applied to simultaneously quantify target heavy metals in spiked water samples. Owing to excellent sensitivity, high robustness, affordability, and fast response, the presented electrochemical sensor could be incorporated into a portable and miniaturized potentiostat device, making it a promising method for on‐site water analysis.

The Role of Silver Nanoparticles in Electrochemical Sensors for Aquatic Environmental Analysis

“…Nevertheless, even strong reducing agents can render AgNPs of various morphologies (quasi-spherical, cubic, twinned structure, and triangles) and larger size distributions when deposited on highly wrinkled and folded graphene nanosheets [ 155 ], or when the Ag(I) precursor is previously encapsulated with a massive chelating ligand [ 156 ], while a precisely controlled green approach can produce remarkably small particles ( d = 5 nm) with high catalytic efficiency [ 168 ]. AgNPs of precise size and shape can also be formed and fine-tuned using electric current [ 79 , 80 , 119 , 182 ]. In electrochemical sensors based on electrodeposited silver nanomaterial [ 81 , 148 ], the addition of silver material was found to play a key role in the trace-level quantification of both trivalent and hexavalent chromium through formation and stabilization of functional bimetallic silver–gold metal oxides [ 81 ], and in the formation of dual-region WE for simultaneous detection of inorganic nitrogen-containing species (nitrate/ammonia) through a signal current channel [ 148 ].…”

“…Electrodeposition can be performed by immersing the electrode substrate (disc or 3D electrodes) into the silver salt solution [ 75 ]. In addition, electrodeposition can be carried out from various background electrolytes such as acetic acid(AcOH)/NH 3 buffer [ 76 ], H 2 SO 4 [ 77 ], HNO 3 [ 78 ], KNO 3 [ 79 ] and phosphate buffer solution (PBS) [ 80 ]. For two-dimensional sensors (screen-printed carbon electrodes, inkjet-printed electrodes, doped rigid glass substrates), electrodeposition can also be done by drop casting the Ag(I) solution on the surface of the working electrode and applying a CV in a given timeframe [ 81 ].…”

“…( d ) DPASV sensor based on SPCE decorated with butterfly-shaped silver nanostructure for the simultaneous detection of Cd(II), Pb(II), Cu(II), and Hg(II) in tap water and environmental (rain, lake, river) water, respectively. Reproduced from Naseri et al [ 79 ] under the terms of Creative Commons CC BY license.…”

“…Different voltammetric platforms have been developed for the simultaneous detection of four different HMs, i.e., lead, cadmium, copper, and mercury, one based on AgNPs/rGO nanocomposite as interface material layered over a magnetic GCE [ 116 ], and the other based on a butterfly-shaped silver nanomaterial modified SPCE [ 79 ]. In the first report [ 116 ], the SWASVs exhibits four distinct and well-defined peaks (−0.74 V for Cd, −0.56 V for Pb, −0.05 V for Cu, and +0.32 V for Hg, respectively), and a wide linear range from 0.05 μM to 3.5 μM for all target ions with LODs of 0.254 μM (Cd), 0.287 μM (Pb); 0.171 μM (Cu) and 0.180 μM (Hg) were achieved in the simultaneous analysis.…”

“…In the first report [ 116 ], the SWASVs exhibits four distinct and well-defined peaks (−0.74 V for Cd, −0.56 V for Pb, −0.05 V for Cu, and +0.32 V for Hg, respectively), and a wide linear range from 0.05 μM to 3.5 μM for all target ions with LODs of 0.254 μM (Cd), 0.287 μM (Pb); 0.171 μM (Cu) and 0.180 μM (Hg) were achieved in the simultaneous analysis. In the second report [ 79 ], DPASV was employed for simultaneous detection of four target HMs in tap water, rainwater, lake water, and river water. Under the optimal conditions (0.1 M acetate buffer, pH = 4.4; E d = −0.7 V; t d = 30 s), individual peaks occurred at −0.788 V, −0.536 V, −0.209 V, and +0.627 V, corresponding to the oxidation of cadmium, lead, copper, and mercury, respectively ( Figure 5 d).…”