Novel cookie-with-chocolate carbon dots displaying extremely acidophilic high luminescence

A fluorescent carbon dot with a cookie-with-chocolate film structure (about 5 x 5 mu m(2)) showed a high fluorescence quantum yield (61.12%) at low pH. It was hydrothermally synthesized from L-serine and L-tryptophan. The formation mechanism of the film with carbon dots (CDs) was investigated. The film structure was formed by hydrogen bonding and pi-pi stacking interactions between aromatic rings. The strong blue fluorescence of the CDs increased under strong acidic conditions owing to the changes in the N-groups. These cookie-like CDs are attractive for their potential use as effective fluorescent probes for the sensitive detection of aqueous H+ and Fe3+.