CuO nanoparticles derived from metal-organic gel with excellent electrocatalytic and peroxidase-mimicking activities for glucose and cholesterol detection
Graphical abstract
Introduction
Substantial research efforts are directed toward the utilization of nanomaterials in catalytic systems(Brahman et al., 2016; Chen et al., 2018a; Hu et al., 2017b; Huang et al., 2017; Muench et al., 2017; Reddy et al., 2018; Song et al., 2019; Suresh et al., 2018; Zheng et al., 2018). However, to the best of our knowledge, nanomaterials with collective catalytic properties such as high electrocatalytic activity and enzyme-mimicking activities have rarely been reported. Among these available nanocatalysts, transition metal oxides (TMOs) have received much attention in the field of catalysis owing to their higher exposed metal active sites(Chen, et al., 2018b; Ling et al., 2018; Natalio et al., 2012; Tanaka et al., 2018; Xu et al., 2019). Copper oxide (CuO), an important member of the TMOs family, is considered as a promising catalytic material owing to its abundant active sites, chemical stability, low-cost and environmental benignity(Ko et al., 2012; Poizot et al., 2000; Wang et al., 2011). To date, different CuO nanomaterials fabricated by various methods including microwave synthesis (Foroughi et al., 2017; Zheng et al., 2016), thermal oxidation (Guo et al., 2012; Huang et al., 2014), templated synthesis (Yang et al., 2016), chemical etching (Huang et al., 2015) have been reported to be used as electrocatalysts or nanozymes. However, the unsatisfactory catalytic activities or the complex synthesis of CuO nanomaterials limits their further applications in different fields. Clearly, it is still highly desirable to develop a simple, efficient and cost-effective strategy for fabricating porous CuO nanomaterials with the versatile catalytic properties of high electrocatalytic activity and enzyme mimicking.
Metal-organic gel (MOG) is an emerging smart soft material that is rapidly straightforwardly self-assembled from metal ions and organic ligands through metal-ligand interactions and intermolecular forces(He et al., 2018; Tam and Yam, 2013; Wu et al., 2019a). MOG have been an increasing interest in the fields of separation (Jayaramulu et al., 2017; Karan and Bhattacharjee, 2016), sensing (Li et al., 2018; Lin et al., 2016), catalysis (He et al., 2017, 2018), drug delivery (Li et al., 2010; Tan et al., 2016) and light-emitting diodes (Kamtekar et al., 2010; Sun et al., 2006) due to their intrinsic and desirable characteristics of porosity, large surface area, low molecular weight and high thermal stability(Wang et al., 2017). More interestingly, other than their direct use, MOG have been recently employed as a novel attractive precursor for the preparation of different nanomaterials. For instance, FexOy/nitrogen-doped carbon films derived from Fe-based MOG for enhanced lithium storage(Yang et al., 2018). The carbonization of Cr-based MOG in an inert atmosphere to produce nitrogen-doped porous carbon material could be used for small biomolecular sensing(Shih et al., 2017). Magnetic porous carbon was efficiently remove organic dyes by using Fe-based MOG as a template(Wang et al., 2016). Nevertheless, despite the above progress and achievements, nanostructured TMOs with high surface area derived from MOG has rarely been reported. Therefore, it is highly possible to prepare CuO nanostructures by using MOG as a precursor due to its facile synthesis and the desirable characteristics of large specific surface areas, porosities, stability and ultrahigh metallic dispersion.
Herein, a simple and efficient stratege was developed to synthesize CuO nanoparticles (CuO-NPs) with high surface area as a versatile catalytic nanomaterial by thermal decomposition of Cu-based metal-organic gel (Cu-MOG) precursor. As shown in Scheme 1, the CuO-NPs showed high electrocatalytic activity for glucose (Glu) oxidation and distinguished peroxidase-like catalytic activities. The versatile catalytic functions of CuO-NPs could provide a promising platform for developing a bioanalysis and sensing system. Moreover, the strategy for the utilization of MOG as a novel and potential precursor to prepare CuO nanostructures with high surface area provided new promising applications of the rapidly growing MOG family.
Section snippets
Synthesis of CuO-NPs
Firstly, Cu-MOG was synthesized rapidly by a one-step mixing method. Briefly, 0.02 M CuSO4·5H2O and 1,3,5-tris(4,-carboxyphenyl) (H3BTB) were mixed in an equal volume. Then blue gel was appeared quickly. The as-obtained Cu-MOG was further freeze-dried to completely remove solvents. Subsequently, the dried Cu-MOG was heated to 500 °C for 1 h with a ramp of 2 °C min−1 in air. Finally, the color of the final product changed from blue to black.
Electrochemical experiments for Glu detection
Firstly, glassy_carbon_electrode (GCE) were polished
Characterization
Thermogravimetric (TG) analysis (Fig. S1) suggested that Cu-MOG lost weight seriously at about 400 °C and had almost no more weight loss with increasing temperature. From which it can be inferred that the simultaneous formation of stable and pure CuO-NPs at temperatures above 400 °C. Furthermore, scanning electron microscope (SEM) images of Cu-MOG calcined at different temperatures in air indicated that Cu-MOG precursor converted to CuO-NPs at 500 °C (Fig. S2a∼d). The as-prepared Cu-MOG showed
Conclusion
In summary, we successfully reported a facile and efficient strategy to prepare CuO-NPs as versatile catalysts by thermal calcination MOG precursor. The as-synthesized CuO-NPs with high specific surface areas, porosities and abundant exposed metal active sites could be successfully used as electrocatalysts and biomimetic nanozymes, which showed high sensitivity and selectivity for the detection of Glu and cholesterol. Consideration the limitations of in vitro testing, the further interesting
CRediT authorship contribution statement
Qing Wu: Conceptualization, Methodology, Investigation, Data curation, Validation, Formal analysis, Writing - original draft. Li He: Writing - review & editing. Zhong Wei Jiang: Visualization. Yang Li: Software. Zheng Mao Cao: Software. Cheng Zhi Huang: Formal analysis, Writing - review & editing. Yuan Fang Li: Funding acquisition, Formal analysis, Writing - review & editing, Project administration.
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgments
The authors are grateful to the National Natural Science Foundation of China (NSFC, no. 21575117).
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