| Metal-organic frameworks (MOFs) are a new class of porous materials with unrivalleddegree of tunability, and they have received considerable attention from the last decade due totheir high accessible surface area, porosity and multitudinous structures and functions. Owingto their excellent properties, these complexes have been applied in varieties fields such as gasstorage and separation, catalysis, drug delivery and supercapacitors. MIL-101has showed alarge pore volume, a very high specific surface area and a well thermal stability and chemicalstability, thus, the MIL-101has great potential for applications in electrochemical sensors.Carbon paste electrodes (CPEs) are preferred due to the properties of low costs,renewable surface and wide potential window. The screen-printed carbon paste electrodes(SPCEs) was developed by combined with screen printed technique. SPCEs not only have thesame advantages of CPEs, but also can be mass-preparing product and replaced. SPCEs makethe electrochemical sensors smaller and more portable and have been used widely inelectroanalysis. This paper mainly study the electrochemical behaviors of the MIL-101modified carbon paste electrode (MIL-CPE) and the pre-treatment SPCE and theirapplications in electroanalysis. The main works is concisely described as followed:(1) MIL-101was synthesized from hydrothermal reaction and characterized by scanningelectron microscope (SEM) and N2physical adsorption experiments. The CPE modified withmetal-organic framework MIL-101was developed. The electrochemical sensing features ofMIL-CPE were studied by electrochemical impedance spectroscopy (EIS) and cyclicvoltammetry (CV). The charge transfer resistance (Rct) of [Fe(CN)6]3-/4-couple at theMIL-CPE was considerably smaller than that of CPE (the value of Rctreduced to400Ω from1200Ω), and the redox currents of K3[Fe(CN)6] and Ru(NH3)6Cl3at MIL-CPE were higherthan that of CPE meanwhile the reversibility of K3[Fe(CN)6]was enhanced. It turned out thatthe MIL-CPE posses a good electrical conduction ability. An enhanced electrocatalyticactivity towards oxidation of dopamine (DA) and uric acid (UA) were observed at theMIL-CPE, and the peak to peak separation was increased to118mV.. Thus, the MIL-101hasgreat potential for applications in electrochemical sensors. The peak currents of DA and UAwere liner with the concentration from5to250μM and30to200μM respectively, and thedetection limits were2.0and20μM for DA and UA.(2) Ethylenediamine was grafted on the uncoordinated Cr(III) sites of the MIL-101successfully. The EN-MIL-101was characterized by SEM, infrared spectra and N2physicaladsorption experiments. The effect of uncoordinated Cr(III) sites was studied by EIS and CV. Compared with CPE and MIL-CPE, the Rctof [Fe(CN)6]3-/4-couple at the EN-MIL-101modified CPE (EN-MIL-CPE) was smaller (the value of Rctwas about400Ω), and the redoxcurrents of K3[Fe(CN)6] at EN-MIL-CPE were higher, and the reversibility of K3[Fe(CN)6]was enhanced. It turned out that the ethylenediamine improved the electrical conductionability of MIL-101. In addition, the uncoordinated Cr(III) sites was important for theoxidation of DA and UA and was identified as the activity site for catalysis.(3) The original SPCE was pre-treated by CVs in0.1M KCl, and the pre-treated SPCE(P-SPCE) was characterized by EIS and CV. Results indicated that the activity sites of theelectrode surface increased and the electrical conduction ability has been enhanced after thepre-treated procedure. The P-SPCE was used for detected Pb2+with the sensor of in situplated bismuth film. The testing conditions and performances of the P-SPCE were optimizedby differential pulse stripping voltammetry (DPSV). Under the optimal experimentalconditions, the linearity was found to be2to1500μg L1for Pb2+detection, and the limits ofdetection is0.868μg L1. A great result was obtained in the detection of actual samples. |
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