Dezhi Yang

The Cu-MOF anchored on graphitic carbon nitride (Cu-MOF/C ₃ N ₅ ) framework for antioxidant sensing exhibits enhanced laccase-like activity due to increased hot carrier production and photothermal effects from NIR irradiation.

A novel copper and iron doped containing chitosan and heparin sodium carbon dots (CS-Cu,Fe/HS) nanozyme was formulated through a single-step microwave digestion method. CS-Cu,Fe/HS exhibits excellent peroxidase (POD)-like activity and positive charge characteristics, and it can oxidize the negatively charged 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) in the presence of H₂O₂ to produce a green compound (ox-ABTS). Furthermore, CS-Cu,Fe/HS enhances electron transfer and provides additional active sites through the valence state transformations of Fe²⁺/Fe³⁺ and Cu²⁺/Cu⁺. Interestingly, the POD-like activity of CS-Cu,Fe/HS is inhibited with the introduction of ampicillin (AMP), which may be because the Cu and Fe ions in CS-Cu,Fe/HS form complexes with AMP, leading to changes in the structure or surface properties of the nanozyme, thereby reducing the number of active sites on the nanozyme. Drawing from this, a straightforward and reliable colorimetric sensor was constructed for AMP detection, featuring a linear range of 0.033 to 110 μg/mL and a detection limit as low as 11.6 ng/mL. The proposed detection method for AMP performed well in real samples, with recoveries ranging from 94.8% to 110.2%. Graphical abstract

A metal–organic-framework (MOF) fluorescent sensor is reported based on NH₂-MIL-101(Fe) propelled pesticide and alkaline phosphatase (ALP) catalytic reaction. Different from previous reports, a cascade reaction system combined with MOF structural changes to generate fluorescence was employed. The rationale is that ALP can hydrolyze L-ascorbic acid 2-phosphate (AAP) into L-ascorbic acid (AA), which can reduce Fe³⁺ to decompose structurally NH₂-MIL-101(Fe), resulting in 2-aminoterephthalic acid (NH₂-BDC) with intense fluorescence. The fluorescence can be decreased to different degrees due to inhibition of organophosphate pesticides (OPPs) on the activity of ALP. By taking chlorpyrifos (CPY) as the model compound of an OPP pesticide and adding ALP and CPY into the NH₂-MIL-101(Fe) framework, the resulting cascade reaction fluorescence sensors exhibit a good sensitivity for CPY and ALP sensing. The working ranges are 0.02–2 μg/L and 0.2–20 mU/mL with detection limits (LOD) of 5.31 ng/L and 0.05 mU/mL, respectively. The proposed sensor has been actually applied to satisfactory detection of CPY and ALP in food and serum samples. This fluorescence-based assay may extend the application of MOF-based biosensors. Graphical Abstract