One-Step Synthesis of Acidophilic Highly-Photoluminescent Carbon Dots Modified by Ionic Liquid from Polyethylene Glycol.

Acidophilic highly-photoluminescent ionic liquid (IL)-modified carbon dots (CDs) were fabricated directly from polyethylene glycol-2000 (PEG) by a simple one-step hydrothermal method in a system containing an IL (1-butyl-3-methylimidazolium bromide [Cmim]Br) and hydrochloric acid (HCl). In this process, PEG works as the carbon source, [Cmim]Br as the modifier, and HCl as the accelerator. CDs with low photoluminescence (PL) intensity and quantum yields (QYs) were generated in the system without H, but CDs with high PL intensity and QYs could be prepared after H was introduced. Moreover, with the increase of H concentration, the QYs of the prepared CDs increase subsequently, and the highest QY reaches up to 43%. The formation mechanism was explored, and the results showed that H changes the surface groups of the CDs generated without H into those that exist on the CDs generated with H, which further improves the PL performance of the CDs. Different from most CDs reported in the literature, the as-prepared CDs can still exhibit high PL intensity even under strong acidic condition.