CuO/ZIF-8 hybrid structure was obtained by adding the PVP-modified foliaceous CuO microstructures during the preparation of ZIF-8 polygon particles as a promising candidate for promoting the thermolysis process of NC. Thermoanalysis and pyrolysis kinetics based on the DSC and TG/DTG data revealed that the CuO/ZIF-8-NC decomposition had a weightlessness rate of 77.81%, heat release of 2882.5 J⋅g – 1 , the exothermic peak temperature of 471.25 K, and activation energy of 172.2 ± 16.0 kJ⋅mol – 1 , indicating that CuO/ZIF-8 has better catalytic activity than CuO and ZIF-8. The reconstructed n th -order kinetic models for NC/catalysis complexes were obtained using a modified fitting algorithm based on the results of isoconversional kinetic analysis, indicating that CuO/ZIF-8, CuO, and ZIF-8 had different catalytic effects on the thermolysis pathways of NC. This study suggests that CuO/ZIF-8 composite may have prospective application as a high potential and unique catalyst for accelerating NC pyrolysis.
Lei Deng,Senqing Fan,Yu Chen,Jiaojiao Chen,Zenghui Mai,Zeyi Xiao
A binder-free self-supported CuO/ZIF-8@NiF electrode is fabricated with CuO/ZIF-8 particles in situ growth in nickel foam pores. ZIF-8 is first assembled inside the nickel foam pores and then Cu2+ is adsorbed around the surface of ZIF-8 crystal, and finally reduced and oxidized to form CuO. Scanning electron microscopy indicates CuO is uniformly distributed on the surface of ZIF-8. The Cu element is significantly increased from 1.16 to 30.91 mg·g–1 under the existence of ZIF-8 from inductively coupled plasma results. The electrochemical analyses show that the electrochemical active surface area of the CuO/ZIF-8@NiF electrode can be increased two times while its electronic transport resistance can be reduced to one-seventh compared with the CuO/ZIF-8/NiF electrode with CuO/ZIF-8 binding on the substrate. The detection tests exhibit enhanced electrochemical properties with a sensitivity of 5640 μA·mM–1·cm–2, a low detection limitation of 0.1 μM, and a linear detection range from 0.5 to 120 μM. The biosensor presents good anti-interference property, stability, and a 101.08–104.53% recovery rate.
Xiaolun Peng,Ruijie Xu,Liang Zhang,Xingyao Li,Junhui Xu,Dongyun Huang,Yazhen Wang
A sensitive electrochemical sensor was proposed for neohesperidin dihydrochalcone (NHDC) detection using copper oxide/ zinc imidazole framework 8@ carbon nanotubes modified glassy carbon electrode (CuO/ZIF-8@CNTs GCE). The multi-component CuO/ZIF-8@CNTs GCE was prepared by two-step drop-casting method and characterized by Field-emission scanning electron microscopy (FE-SEM). The effective combination of CuO and ZIF-8@CNTs enhanced the electron transfer and catalytic activity of the electrode and greatly strengthened the oxidation current of NHDC, which was about 5.6-fold that of the CuO GCE and 2.3-fold that of the ZIF-8@CNTs GCE. Inspired by this, the CuO/ZIF-8@CNTs GCE was used for NHDC detection and some crucial parameters were optimized. The reaction mechanism at CuO/ZIF-8@CNTs GCE was confirmed to involve two-step two-electron process by cyclic voltammetry (CV) measurements. Finally, the sensor achieved NHDC detection ranging from 0.03 to 10 μM using differential pulse voltammetry (DPV) technique, with a detection limit of 16.0 nM. The satisfactory recoveries of 92.9–107.8 % in liquor samples also demonstrated its practicability in actual samples, matching well with that of high-performance liquid chromatography (HPLC). This work not only designs a simple detection method for NHDC but also opens up a paradigm for leveraging multi-component MOF composite electrode materials for food safety monitoring.
Dongsheng Fu,Yuanzheng Ding,Ruijie Guo,Jie Zhang,Huifang Wang,Baolong Niu,Hong Yan
ZIF-8, a subclass of metal organic frameworks (MOFs), was employed as the CuO carriers because of its high surface areas and good dispersibility. A novel antibacterial agent CuO@ZIF-8 was synthesized by environmentally-friendly direct calcination strategy, and introduced into the composite double-layer films for packing materials. The double-layer films were prepared via solution casting method with polylactic acid (PLA) and polyvinyl alcohol (PVA)-quaternary ammonium chitosan as the matrix of outer layer and inner layer, respectively; and CuO@ZIF-8 nanoparticles were introduced into the PVA-quaternary ammonium chitosan layer. The double-layer films exhibited superior antibacterial activity resulted from the uniform dispersion of CuO by ZIF-8 carriers. The elongation at break was enhanced and up to 17.13%, about 2.4-fold that of PLA films. Meanwhile, the films provided low water vapor permeability and strong UV-barrier ability which were attributed to the lay-by-layer casting, CuO@ZIF-8 doping and TiO 2 addition. Cherry tomato preservation experiment revealed that the composite films retarded the growth of harmful microorganisms on the fruit surface. MTT assay confirmed the cytocompatibility of the films. The easily fabricated double-layer films presented potential possibility in the field of biodegradable food packaging.
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