Gelatin Carbon Dots Interaction with Nitrosyl Ruthenium Complex: Fluorescence Quenching and Chemiluminescence...

Carbon dots (CDs) exhibit luminescence, biocompatibility, and higher water solubility. This material has been developed for biological applications, specifically in bioimaging. In this work, the gelatin carbon dots (CD_g) was obtained from commercial gelatin using a hydrothermal method in domestic microwave, and the suppression fluorescent mechanism were enhanced by the addition of the [Ru^II(bdq)(NO)(tpy)]³⁺ (Rubdq-NO⁺) complex ion. After purification through a dialysis bag, the resulting CDs (CD_g) exhibit fluorescent emission at 400 nm and maintained fluorescence stability in an aqueous solution (pH = 7) for 30 days under 5 ^◦C. Fluorescence quenching studies revealed an electrostatic interaction between the negative charge from CD_g (δ =  - 20 mV) and the positively charged nitrosyl (NO⁺) ligand of the ruthenium complex (Rubdq-NO⁺), resulting in quenching of the CD_g fluorescence due to the inner filter effects (IFE). The chemiluminescence reaction of CD_g and Rubdq-NO-CD_g in presence of norepinephrine (NOR) were evaluated. NOR in PBS are liable to undergo spontaneous oxidation to quinone form (NOR-quinone). CD_g are believed interact with NOR-quinone and an electron transfer occur obtained CD_g⁺ accompanied to green emission fluorescence (520 nm). While for Rubdq-NO-CD_g in presence of NOR, the green emission occurs accompanied by NO⁰ release using DAF-2 probe.