Huihui Liang,Mengli Xu,Yongmei Zhu,Linyu Wang,Yi Xie,Yonghai Song,Li Wang
A uniform nanosphere derived from ferrocence-modified covalent-organic frameworks (COFETTA-TPAL-Fc(COOH)2) with 200 nm in diameter was prepared by dehydration condensation reaction between 4,4′,4′,4′- (ethane-1,1,2,2-tetrayl) tetraaniline and terephthalaldehyde in the presence of electroactive Fc(COOH)2. The Fc(COOH)2 was embedded into the layers of COFETTA-TPAL to result in the formation of nanospheres, which increased the specific surface area of the available COFETTA-TPAL to provide more active sites due to the increase in interlayer distance. The Fc(COOH)2 could interact with H2O2 which might undergo self-disproportionation process to produce O2 and be reduced into H2O simultaneously, whereas the generated O2 was directly reduced into H2O by COFETTA-TPAL. The reduction peak current of the generated O2 at −0.5 V (j–0.5 V) was gradually enhanced, whereas that of Fc(COOH)2 around 0.45 V (j0.45 V) was decreased with continuous adding of H2O2. Thus, the COFETTA-TPAL-Fc(COOH)2 nanospheres were used to fabricate a “on–off” nonenzymatic H2O2 ratiometric electrochemical sensor. The proposed “on–off” ratiometric electrochemical sensor showed good performance with a wide linear range of 1.1–500 μM, high sensitivity of 0.009 μM–1, and lower detection limit of 0.33 μM. The work would offer insights for design and preparation of electroactive COF and accelerate the practical application of COF in electroanalysis.
A novel ascorbic acid (AA) electrochemical biosensor based on ferrocene dicarboxylic acid (Fc(COOH) 2 )/zeolitic imidazolate framework-8 (ZIF-8)/three-dimensional (3D) kenaf stem-derived macroporous carbon (3D-KSCs) was proposed for the first time. The formation and properties of Fc(COOH) 2 /ZIF-8/3D-KCSs nanocomposites were characterized by scanning electron microscopy, Fourier transform-infrared spectroscopy, N 2 adsorption/desorption isotherms, X-ray powder diffraction, and energy dispersive X-ray spectroscopy. The results showed that a large number of short rod-like ZIF-8/Fc(COOH) 2 was arrayed on the 3D-KSCs surface via a simple one-step hydrothermal method. Fc(COOH) 2 was firmly encapsulated into the pores of ZIF-8 simultaneously during the synthesis process of ZIF-8. The Fc(COOH) 2 /ZIF-8/3D-KCSs nanocomposites were employed to prepare integrated Fc(COOH) 2 /ZIF-8/3D-KSCs electrode directly for electrochemical AA sensing, and the integrated electrode showed better performance for AA detection than traditional enzyme-based biosensors and nonenzymatic sensors. A wide detection range of 0.06 μM~5.01 mM and a low detection limit of 0.017 μM were obtained with good stability and selectivity. The work also sheds new light on developing ZIF-8-based nanocomposites for electrochemical sensing.
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