Active Nanozymes Research Articles

NiFe2O4 nanoparticles as nanozymes, a new colorimetric probe for 2,4-dichlorophenoxyacetic acid herbicide detection

• A Nano compound NiFe 2 O 4 synthesized. • The synthesized nanomaterial exhibit peroxidase-like activity. • New insight into the design of new nanozymes for cascaded catalytic detection and other low-cost, high-efficiency, and rapid detection applications. • New colorimetric method is described for the detection of 2,4-D herbicide residues. The use of enzyme mimics to detect herbicide residues quickly has recently sparked a lot of attention. The majority of nanozymes, nevertheless, are low active. Here, an active nanozyme (NiFe 2 O 4 ) that mimics peroxidase (POD-like) with improved activity was logically developed. The probe was systematically characterized by powder XRD, SEM, EDX, HR-TEM, UV–Vis absorption, FTIR and fluorescence spectrophotometers. Based on its high peroxidase-like activities and cascaded catalytic reactions with 2,4-dichlorophenoxyacetic acid (2,4-D), a new method is described for the detection of 2,4-D herbicide residues using 4-(Dimethylamino) benzaldehyde as chromogenic substrate in the presence of hydrogen peroxide. More importantly, the proposed method shows the limit of detection (LOD) of 0.311 µg.mL -1 and the recovery ranged from 97.74 to 101.44%. This study provided new insight into the design of new nanozymes for cascaded catalytic detection and other low-cost, high-efficiency, and rapid detection applications.

Enzyme-like activity of cobalt-MOF nanosheets for hydrogen peroxide electrochemical sensing

Metal-organic frameworks (MOFs) are receiving increased attention as new functional nanomaterials for the development of electrochemical sensors. Herein, we develop an electrochemical platform for non-enzymatic hydrogen peroxide detection built with a composite of two-dimensional cobalt MOF nanosheets and Nafion (2D-Co-MOF@Nafion). The feasibility of the 2D-Co-MOF@Nafion composite as active material for high performance hydrogen peroxide sensor was investigated by using cyclic voltammetry and chronoamperometry. Its voltammetric response reveals an efficient charge transport through the MOF composite, and rapid electron exchange between MOF and electrode. Notably, these MOF nanosheets exhibit enzyme-like activity for the non-common catalytic oxidation of hydrogen peroxide, leading to an electrochemical sensor with rapid quantitative detection, outstanding sensitivity, selectivity, stability, and durability at the desirable neutral pH. In particular, for a cobalt metal loading of 1.2 nanomol, the sensor yields amperometric H2O2 detection with characteristic electrocatalytic parameters of imax= 5.7 mA cm−2 and KM = 13 mM. Moreover, linear ranges of up to either 1 mM or 10 mM are achieved, with sensitivities as high as 570 ± 5 A cm−2 mM−1 or 395 ± 10 A cm−2 mM−1 for the low and high concentration ranges, respectively. The particular coordination chemistry of the MOF consisting of a regular arrangement of multiple Co(II) redox metal sites connected by appropriate organic ligands can provide inherent enzyme-mimicking properties, thereby explaining the higher oxidase-like activity of the present MOF. This work raises the new idea of using two-dimensional cobalt-based MOFs as active nanozymes, offering exciting opportunities in the design of non-enzymatic electrochemical sensing devices.