Carbon Quantum Dots with Tunable Size and Fluorescence Intensity for Development of a Nano‐biosensor

Carbon quantum dots (CQDs) are a class of nanomaterials known for their remarkable photostability, chemical inertness and biocompatibility. Changing their size, structure, and surface chemistry enable the tuning of their luminescence property, which gives them tremendous potential for various applications. CQDs synthesis typically involves long tedious processes, requiring multiple steps and harsh reaction conditions. Here, a new reliable, economical, and ultra-rapid one-step fabrication method is introduced to obtain CQDs with well-defined and reproducible photoluminescence properties via a simple heat treatment. These solid-state CQDs are homogenous in size and are ready to use without the need for further purification. The size of the fabricated CQDs and their corresponding peak fluorescence intensity are confirmed to be tunable by simple adjustment of the heat treatment conditions. Coupled with their selective fluorescence quenching by metal ions, the clinical potential of CQDs is demonstrated for biosensing applications by designing a new nano-biosensor to assess the quality of stored blood units through hemolysis quantification without disrupting storage conditions. This may pave the way for a new standard in blood bank inventory management.