As an emerging zero-dimensional nanomaterial, MXene quantum dots (MQDs) have aroused the interest of researchers because of their unique physical and chemical characteristics. Here, a straightforward hydrothermal strategy was used to successfully produce the amino-functionalized Ti 3 C 2 MQDs. The functionalized Ti 3 C 2 MQDs exhibited bright blue fluorescence (FL), which was derived from its size effect and surface defects. In addition, Ni 2+ can bind to the amino groups on the surface of Ti 3 C 2 MQDs. The absorption of the excitation light by the light-absorbing substance causes nickel ions to effectively quench the photoluminescence of Ti 3 C 2 MQDs, which can be explained by the internal filter effect (IFE). At the same time, the strong affinity of histidine (His) for Ni 2+ , which is absorbed by His to form a stable complex, causes Ni 2+ to dissociate from the Ti 3 C 2 MQD surface and restore the FL. Thus, a fluorescent sensor for detecting the His content in serum was developed. Overall, this work provides a method for the detection of His and shows that the Ti 3 C 2 MQDs have great potential in biomedical and biosensing applications.
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