Jin Yang,Xin Shu,Shangying Qin,Li Huang,Shiqi Cheng,Yilin Wang
Co 3 O 4 nanoclusters (NCs) was prepared, and a novel method based on hydrogen peroxide (H 2 O 2 ) mediated fluorescence recovery of calcein-Co 3 O 4 NCs system for cholesterol detection was developed. The detection utilizes fluorescence quenching and recovery of calcein. In the absence of H 2 O 2 , the fluorescence of calcein is quenched by Co 2+ ions on the surface of Co 3 O 4 NCs. However, the fluorescence of calcein is restored in the presence of H 2 O 2 as a result of the oxidation of Co 2+ ions to Co 3+ ions. Further investigation indicates tha Co 3 O 4 t there is a correlation between H 2 O 2 concentration and fluorescence enhancement of calcein. Due to H 2 O 2 being one of the products of cholesterol catalytic oxidation, a novel cholesterol fluorescence measurement method has been established, which can achieve sensitive detection of cholesterol in the range of 1.0–50 μM, with a limit of detection (LOD) as low as 0.48 μM. More importantly, the feasibility of the method was verified in human serum total cholesterol determination with satisfactory results, indicating its potential application in real sample analysis.
This study innovated cobalt-based catalytic nanocomposites (CCNs) for the heterogeneous activation of peracetic acid (PAA), a green and efficient advanced oxidation process for removing antibiotics from water. Commercial Co 3 O 4 catalysts exhibit limited activity due to stable electronic structures. To overcome this, CCNs were synthesized using a one-step condensation method, incorporating a size control strategy that anchors Co 3 O 4 nanoclusters within 4–5 nm onto six-fold cavity of g-C 3 N 4 , simultaneously modifying the coordination environment of Co. This alteration significantly enhances the adsorption energy of PAA and catalytic activity compared to commercial Co 3 O 4 . The improved performance of CCN2, in particular, is attributed to a shift in the cobalt d band center towards the Fermi level, facilitating electron delocalization and transfer, enhancing Co–O bonding, and accelerating PAA decomposition. CCN2’s superior activity, with a cefapirin (CFP) degradation kinetic rate constant ( k 1 = 0.760 min −1 ) ~11 times that of PAA direct oxidation ( k 1 = 0.070 min −1 ) and ~5 times that of commercial Co 3 O 4 /PAA system ( k 1 = 0.164 min −1 ), is due to its ability to generate dominant reactive species for antibiotic degradation, including alkoxy radicals (CH 3 C(=O)OO•), high valence metal (Co IV (=O) 2+ ), and singlet oxygen ( 1 O 2 ), with the latter two being crucial for the degradation process. The degradation of CFP involved three mechanisms, including direct oxidation by PAA, decarboxylation, and open-ring reactions at nitrogen sites. This research provides insights into developing high-activity catalysts for efficient PAA activation and antibiotic removal, leveraging the strategy of shifting the transition metal d band center.
Li Wang,Yayun Zhang,Yingzhen Xie,Jie Yu,Han Yang,Longfei Miao,Yonghai Song
A novel supporting material named as three-dimensional kenaf stem-derived carbon (3D-KSCs) was used to load hierarchical Co 3 O 4 nanoclusters for electrochemical sensing glucose. The 3D-KSCs/hierarchical Co 3 O 4 nanoclusters were constructed by two steps. Los of acicular precursor nanoclusters firstly grew on the channels of 3D-KSCs densely by hydrothermal method and then the as-prepared 3D-KSCs/hierarchical Co 3 O 4 nanoclusters was obtained by thermal pyrolysis of the 3D-KSCs/precursors nanocomposites at 400 °C. The 3D macroporous configuration of 3D-KSCs resulted in lots of hierarchical Co 3 O 4 nanoclusters arrayed on the surface of 3D-KSCs owing to its large enough specific surface area , which effectively avoided their aggregations and improved the stability of nanocomposites. The obtained 3D-KSCs/hierarchical Co 3 O 4 nanoclusters showed a large number of needle-shaped and layered Co 3 O 4 nanoclusters uniformly grew on the macropore’s walls of 3D-KSC. Due to its unique nanostructures, the 3D-KSCs/hierarchical Co 3 O 4 nanoclusters integrated electrode showed superior performance for nonenzymatic electrochemical glucose sensing, showing wide linear range (0.088–7.0 mM) and low detection limit of 26 μM. It might be a new strategy to prepare nanostructures on 3D-KSC for future applications.
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