Exploring the blue luminescence origin of nitrogen-doped carbon dots by controlling the water amount in synthesis

Abstract

A series of nitrogen-doped carbon dots (N-CDs) with high quantum yield (QY) and product yield were prepared by hydrothermally treating the same carbon sources with different amounts of water at 110 °C for 4 hours. Along with the increasing water amount in synthesis, the graphitization degree of the N-CDs decreased but the corresponding QY increased firstly and then decreased. When the water amount in synthesis was 0.5 mL, the obtained N-CDs had the highest QY of 73% and a product yield of 63% respectively. The optimal N-CDs were applied as bioimaging probes successfully due to their excellent PL properties and low cytotoxicity. Detailed characterization results on these N-CDs proved that the blue luminescence mainly originated from the functional group CO in the COOH on the N-CD surfaces.