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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Developing efficient water adsorbents for solar-driven atmospheric water harvesting (AWH) still remains a challenge due to the poor photothermal heating ability and slow sorption kinetics of most adsorbents. Postsynthetic ligand exchange (LE) provides an alternative strategy to prepare metal–organic framework (MOF) materials with varied structures and functions. In this work, multifunctional hollow MIL-101(Cr) with ferrocene dicarboxylic acid (Fc(COOH)2) ligand exchanged (HMF) nanospheres are prepared and utilized for efficient AWH. The resulted HMF nanospheres present great visible light absorption (>80%) and photothermal conversion ability (61.6%) due to the introduced Fc(COOH)2 ligand. The water adsorption and desorption rates of the HMF nanosorbent are 2.3 times and 4.5 times that of MIL-101(Cr). The fast water capture and solar-driven release kinetics of HMF nanosorbents indicate its great potential for actual water harvesting. The outdoor water collection experiment demonstrates that the areal water harvesting capacity of the HMF nanosorbent is 1720 g m–2 per cycle with packed thickness of 8 mm. HMF nanosorbents also demonstrate good antibacterial activity (91.4%), which is beneficial to the collection of healthy and safe water. This work provides a facile and practical method to design multifunctional MOFs from the molecular level by LE and to achieve solar-driven AWH and other fields.
Lysozyme (Lyz) is found in animal and human bodily fluids, and is frequently utilized as a biomarker for various diseases. Even trace amounts of Lyz in food can potentially trigger adverse immune system reactions in sensitive individuals. Therefore, it is very important to monitor Lyz concentration in foods for safety. In this study, a simple and convenient electrochemical sensor for Lyz detection was prepared by modifying gold nanoparticles (AuNPs) and ferrocene dicarboxylic acid (Fc(COOH)2) on a glass carbon electrode (GCE), which was characterized fully by various electrochemical methods and field emission scanning electron microscope (FESEM). The proposed method utilized Fc(COOH)2as a probe and AuNPs as an electron transfer medium to improve the sensor’s current response performance. Under optimal conditions, the sensor was used to detect Lyz with a linear range from 0.10~0.70 mmol·L−1with a sensitivity of 50.55 μA·mM−1·cm−2, and a limit of detection (LOD) of 0.07 mmol·L−1. In the standard addition experiment of food samples (egg white), a total R.S.D. of less than 6.75% and an average recovery between 95.45% and 102.62% were obtained.Keywords:electrochemical sensors;ferrocene dicarboxylic;gold nanoparticles;lysozyme;amplifier unit
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