Optimized hexamine-derived carbonized polymer dots as fluorescent nanoswitches for precision spectral imaging sensing of glucocorticoids.

The synthesis is presented of highly fluorescent hexamine-derived carbonized polymer dots (HACDs), which are made possible by ethylenediamine and folic acid. Density functional theory is used to clarify the formation mechanism and optimize the electronic structure of HACDs that resemble polymers. Our study reveals effective intramolecular charge transfer pathways and a favorable reaction coordinate, supported by electrostatic potential mapping and HOMO-LUMO transitions. The resulting HACDs have a ∼3.3 eV optical bandgap, an extraordinary quantum yield of 80.1%, and aggregation-induced, dual-emissive, excitation-independent fluorescence, a property that enables self-calibrated readouts. This dual emission reduces interference from environmental fluctuations (pH, polarity), thereby improving reliability in practical biosensing and bioimaging applications. We confirm the nitrogen doping and excellent photostability through spectroscopic studies over a 90-day duration. The emission quenching represented by HACD was used to determine hydrocortisone and prednisolone quantitatively to examine their biosensing capacity. The negligible toxicity was displayed by the MTT assay on V79 fibroblast cells to confirm the safe biological use of HACD as a nontoxic fluorescence sensor. The obtained results established that the HACDs have potential for the selective detection of glucocorticoids for biomolecular sensing.