Abstract
A metal-organic framework MIL-53(Fe) was successfully synthesized by a simple hydrothermal method. A synthesized MIL-53(Fe) sample was characterized, and results indicated that the formed MIL-53(Fe) was a single phase with small particle size of 0.8 μm and homogeneous particle size distribution was obtained. The synthesized MIL-53(Fe) has been used to modify a glassy carbon electrode (GCE) by a drop-casting technique. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements of the MIL-53(Fe)-modified GCE showed that the MIL-53(Fe) was successfully immobilized onto the GCE electrode surface and the electrochemical behavior of the GCE/MIL-53(Fe) electrode was stable. In addition, several electrochemical parameters of MIL-53(Fe)-modified GCE (GCE/MIL-53(Fe)) including the heterogeneous standard rate constant ( k 0 ) and the electrochemically effective surface area ( A ) were calculated. Obtained results demonstrated that the synthesized MIL-53(Fe) with the small particle size, highly homogeneous particle size, and high electrochemically effective surface area was able to significantly enhance the electrochemical response signal of the working electrode. Therefore, the GCE/MIL-53(Fe) electrode has been used as a highly sensitive electrochemical sensor for cadmium ion (Cd(II)) monitoring in aqueous solution using differential pulse voltammetry (DPV) technique. The response signal of the electrochemical sensor increased linearly in the Cd(II) ion concentration range from 150 nM to 450 nM with the limit of detection (LOD) of 16 nM.
Highlights
The pollution of water sources caused by heavy metal ions, inorganic substances, organic matters, and bacteria from different agricultural, industrial, and medical waste sources has seriously affected people’s lives and the ecosystems and organisms in the aquatic environment [1,2,3]
It can be seen that the samples prepared with the hydrothermal time of 8 hours (Figure 1(a), curve A) and 24 hours (Figure 1(a), curve D) have specific peaks of the MIL-53(Fe); there are several peaks belonging to other crystals [31, 34]
Comparing X-ray diffraction (XRD) patterns of sample B and sample C, the hydrothermal time for the formation of MIL-53(Fe) was chosen to be 12 hours because of the sharper and higher characteristic peaks, which implied that the crystals were formed completely
Summary
The pollution of water sources caused by heavy metal ions, inorganic substances, organic matters, and bacteria from different agricultural, industrial, and medical waste sources has seriously affected people’s lives and the ecosystems and organisms in the aquatic environment [1,2,3]. To improve the sensitivity of electrochemical sensors, advanced materials have been applied to modified electrodes, including nanostructured conducting polymers [12, 15], metal and metal oxide nanoparticles [16,17,18], nanostructured carbon materials (such as porous carbon, carbon nanotube, and graphene/graphene oxide) [17,18,19], and metal-organic frameworks (MOFs) [6, 9, 20,21,22,23,24]. In this work, an effective hydrothermal method was carried out to synthesize a metal-organic framework MIL-53(Fe), which was used to modify the glassy carbon electrode (GCE) for sensitive electrochemical determination of Cd(II) ion concentration in aqueous solutions. The specific characteristics of the synthesized MIL-53(Fe) were carefully analyzed by various chemical-physical techniques
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