Linker-Free Magnetite-Decorated Gold Nanoparticles (Fe3O4-Au): Synthesis, Characterization, and Application for Electrochemical Detection of Arsenic (III)

Abstract

Linker-free magnetite nanoparticles (Fe3O4NPs)-decorated gold nanoparticles (AuNPs) were grown using a new protocol that can be used as a new platform for synthesis of other intact metal–metal oxide nanocomposites without the need for linkers. This minimizes the distance between the metal and metal oxide nanoparticles and ensures the optimum combined effects between the two material interfaces. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy confirmed the successful synthesis of the Fe3O4-Au nanocomposite, without any change in the magnetite phase. Characterization, using transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy, revealed the composite to consist of AuNPs of 70 ± 10 nm diameter decorated with tiny 10 ± 3 nm diameter Fe3O4NPs in Au:Fe mass ratio of 5:1. The prepared Fe3O4-Au nanocomposite was embedded in ionic liquid (IL) and applied for the modification of glassy carbon electrode (GCE) for the electrochemical detection of As(III) in water. By combining the excellent catalytic properties of the AuNPs with the high adsorption capacity of the tiny Fe3O4NPs towards As(III), as well as the good conductivity of IL, the Fe3O4-Au-IL nanocomposite showed excellent performance in the square wave anodic stripping voltammetry detection of As(III). Under the optimized conditions, a linear range of 1 to 100 μg/L was achieved with a detection limit of 0.22 μg/L (S/N = 3), and no interference from 100-fold higher concentrations of a wide variety of cations and anions found in water. A very low residual standard deviation of 1.16% confirmed the high precision/reproducibility of As(III) analysis and the reliability of the Fe3O4-Au-IL sensing interface. Finally, this proposed sensing interface was successfully applied to analyzing synthetic river and wastewater samples with a 95–101% recovery, demonstrating excellent accuracy, even in complex synthetic river and wastewater samples containing high concentrations of humic acid without any sample pretreatments.

Multiplexed Anodic Stripping Voltammetry Detection of Heavy Metals in Water Using Nanocomposites Modified Screen-Printed Electrodes Integrated With a 3D-Printed Flow Cell

“…Electron microscopy, X-Ray Diffraction and Fourier transform infra-red spectroscopy were used to ensure the synthesized (BiO) 2 CO 3 -rGO and Fe 3 O 4 -Au nanocomposites had desired morphologies/structures and chemical compositions as reported in our previously published papers ( Zhao et al, 2020 ; Sedki et al, 2021 ).…”

“…The (BiO) 2 CO 3 -rGO-Nafion and Fe 3 O 4 -Au-IL sensing nanocomposites were synthesized based on previously reported protocols ( Zhao et al, 2020 ; Sedki et al, 2021 ) using the following steps.…”

“…The employment of the disposable SPEs avoided the traditional pretreatment process frequently-used to prepare glassy carbon or carbon paste WE, but obtained a comparable sensitivity based on the modification of the nanocomposites. Compared to the batch electrochemical cells in previously published papers, including ours (Zhao et al, 2020;Sedki et al, 2021), the flow electrochemical stripping analysis reported in this study has the advantages of: automation potential, high throughput analysis of large quantities of samples, high reliability due to reduced human intervention, miniaturization potential on the size of analytical cell/device, near-/real-time detection, integration with other analytical systems and capability for the simultaneous detection of As(III), Cd(II), and Pb(II). Additionally, the flow cell geometry was optimized and finally confirmed by COMSOL Multiphysics to resolve the problems existing in the application of SPEs in flow system based on a finite element method (FEM), which is a reliable and effective approach for the computational fluid dynamic (CFD) analysis.…”

“…Nano-materials/composites modified electrodes for detection of heavy metals Pb(II), Cd(II), and As(III) in water by ASV in batch electrochemical cells has received a great deal of attention ( Bi et al, 2010 ; Pandey et al, 2016 ; Zhao et al, 2020 ; Sedki et al, 2021 ). While highly sensitive and selective, batch cells have limitations.…”

“…The SPEs were composed of two WEs, a CE and a Ag/AgCl quasi-RE. As well, two sensing nanocomposites, i.e., (BiO) 2 CO 3 -reduced graphene oxide (rGO)-Nafion ((BiO) 2 CO 3 -rGO-Nafion) and Fe 3 O 4 magnetic nanoparticles (Fe 3 O 4 MNPs) @Au nanoparticles (AuNPs)-ionic liquid (IL) (Fe 3 O 4 -Au-IL), with different catalytic properties were used to modify the two WEs integrated in SPE separately based on our previous works ( Zhao et al, 2020 ; Sedki et al, 2021 ) with small changes to obtain a good sensitivity and selectivity, as compared with the bare SPEs. On this basis, a homemade flow system for the stripping voltammetry analysis of HMIs was developed, comprising a nanocomposites-modified SPE integrated with an 3D-printed flow cell.…”