Highly blue luminescent nitrogen-doped carbon dots (N-CDs) were prepared in a one-step microwave process using Tween®80 as a surface passivation agent for an otherwise standard citric acid/urea composition. These N-CDs possessed a fluorescent quantum yield as high as 75.5%, when excited at 350 nm, compared to a quantum yield of only 8.2% for the N-CDs prepared using the same composition and reaction conditions but without Tween®80. The addition of Tween®80 also resulted in a red shift in the absorbance wavelength of the π –π* transition from 230 nm to 270 nm and for the n- π* transition from 330 nm to 338 nm. The significant differences in quantum yield and stability between these Tween®80 passivated N-CDs and the non-passivated N-CD counterparts are attributed to the altered carbon and oxygen ratio of the N-CD surface. The passivated N-CDs are highly stable fluorescent probes that can selectively detect Fe2+ and Fe3+ ions with detection limits of 6.5 µM and 2.5 µM respectively. Other carbon dots evaluated for this use have a significantly lower quantum yield and only detect Fe3+ ions, so these N-CDs possess significant advantages over similar probes, and due to their enhanced quantum yield and stability, further research may adapt them to other areas.

High quantum yield carbon dots that give selective detection of Fe2+/Fe3+ ions prepared with Tween® 80

ACS Spring 2022

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