A de novo tripeptide, YFF, can self‐assemble into fluorescent nanostructures under ultraviolet irradiation, and their fluorescence can be selectively quenched by copper ions. Copper ions can co‐assemble with YFF NPs into hierarchical nanostructures, and the quenched fluorescence can recover again with the addition of pyrophosphate (diphosphate, PPi), which is due to the robust interaction between copper ions and PPi. Based on this principle, a simple and cost‐effective alkaline phosphatase (ALP) biosensor has been built up by making use of the specific dephosphorylation of ALP to PPi, in which the coordinated copper ions can reversibly bind to PPi, thus quench and recover the fluorescence of tripeptide nanostructures. The fluorescence intensity correlated well to the concentration of Cu2+ (2–100 μM), PPi (0–500 μM) and ALP (0–500 U/L) i, respectively, and the corresponding limits of detection (LOD) are 1.29 μM, 0.77 μM and 1.84 U/L, respectively. The designed tripeptide‐based nanosensor also exhibits biocompatible, robust sensing performance in serum, indicating its great potential application for clinical diagnosis.

Har Gabur is the carbide obtained from pig manure by burning. The fluorescent carbon dots (CDs) of Har Gabur were successfully synthesized through simulating the digestion process of human gastrointestinal tract. Transmission Electron Microscope (TEM) analysis showed that the average size of the prepared Har Gabur CDs was 4 nm, with good solubility in water and strong fluorescence under UV irradiation. The X-ray and Raman results showed that the Har Gabur CDs were mainly composed of oxygen "O" and carbon "C" elements, in the forms of "C=O" and "C-O." The bond energy results showed that the nitrogen "N" atom presented as "C-N" form, which indicated that Har Gabur CDs also contain "N." In photobleaching assay, Har Gabur CDs showed excellent light stability compared with ordinary organic dye, fluorescein, and Rhodamine B. The fluorescence intensity of Har Gabur CDs was fairly stable within a wide pH range of 3-10. When L-lysine and L-cysteine were applied for the passivation stage, the relative quantum yields were improved by 1.53 and 3.68 times, respectively. Finally, the fluorescence properties of Har Gabur CDs were tested in cells and zebrafish, illustrating that Har Gabur CD has potential in the application of biological labeling and imaging.