Due to its unique biological composition, aquatic products, especially fish, are extremely perishable compared to other muscle products. Herein, we proposed an artificial nanozyme-based colorimetric detection of hypoxanthine (Hx), the indicator of fish freshness, in a minute–time scale without the assistance of a natural enzyme (hypoxanthine oxidase). The principle is based on the interaction between Hx and polyvinylpyrrolidone-modified platinum cubic nanomaterials (PVP-PtNC), in which the catalytic active sites of PVP-PtNC’s surface were blocked by Hx. This causes the downregulation of PVP-PtNC’s catalytic ability and weakened its ability to catalyze the oxidization of 3,3′,5,5′-Tetramethylbenzidine (TMB) by H2O2. Accordingly, the decrease in the UV–vis absorption and the weakening of the colorimetric reaction color is proportional to the Hx concentration. On this basis, a target-triggered colorimetric method for detecting Hx is developed for fish freshness monitoring with a fast detection speed, low cost, high accuracy, and simplified operation. Experiments reveal that the correlation response of Hx is from 0.5 μM to 10 mM with a limit of detection of 0.16 μM. In particular, the Hx detected from real fish indicates that the method possesses a promising potential for practical application. All of these features are expected to promote the development of online detection tools for food safety monitoring.

Visible‐light photoredox‐catalyzed metal‐free one‐pot tandem regioselective synthesis of C4‐phosphorylated phthalazin‐1(2H)‐ones from arylhydrazines, 2‐formylbenzoic acids with diarylphosphine oxides is described. This three‐component transformation occurs smoothly under mild conditions, providing regiospecific access to various phosphorylated products in 73–91% yield. The efficacy of the current catalysis arises from the use of organic 1,2,3,5‐tetrakis(carbazol‐9‐yl)‐4,6‐dicyanobenzene (4CzIPN) as the photocatalyst and cheap K2S2O8 as the oxidant.

Due to the unique biological composition of aquatic products especially fish, it is extremely perishable than other muscle products. Herein, we proposed a polyvinylpyrrolidone-modified platinum cubic nanomaterials (PVP-PtNC) with peroxidase activity for colorimetric detection of hypoxanthine (Hx), the indicator of fish freshness, in a minute-time scale. The principle is based on the interaction of Hx with PVP-PtNC to occupy catalytic active sites on PVP-PtNC’s surface. This causes the downregulation of PVP-PtNC’s catalytic ability and weakened its ability to catalyze the oxidization of H2O2by TMB. Accordingly, the decrease of the UV-Vis absorption and the weakening of the colorimetric reaction color is proportional to the Hx concentration. On this basis, a target-triggered colorimetric method for detecting Hx is developed for fish freshness monitoring with a fast detection speed, low cost, high accuracy, and simplified operation. Experiments reveal that the correlation response of Hx is from 0.5 μM to 10 mM with a limit of detection of 0.16 μM. Especially, the Hx detected from real fish indicates the method possesses promising potentials for practical application. All these features are expected to promote the development of online detection tools for food safety monitoring.