Amphiphilic acetylacetone-based carbon dots

Abstract

The ongoing development of carbon dots (CDs) for different applications calls for researching novel methods for their synthesis and surface functionalization. For the fabrication of photonic devices, apart from the obvious requirement of bright luminescence, CDs also should be soluble in the non-polar solvents used for the ink-printing of their functional layers. Herein, we introduce amphiphilic CDs synthesized from a mixture of benzoic acid and ethylenediamine in acetylacetone, which satisfy both of the abovementioned requirements. These CDs are quasi-spherical nanoparticles that are 20–50 nm in size, with aliphatic, carbonyl, amide, imine, and carbamate groups at the surface. This wide spectrum of surface groups renders them amphiphilic and soluble in a variety of substances, such as toluene, chloroform, alcohol, and water, with relative polarity ranging from 0.002 to 1. By variation of the molar ratio of benzoic acid and ethylenediamine, the highest quantum yield reported so far of 36% in isopropanol is achieved for the amphiphilic CDs. As a demonstration of the use of developed amphiphilic CDs in LEDs, green-emitting charge-injection devices were fabricated with a broad emission band centered at 515 nm, maximal luminance of 1716 cd m⁻², and CCT of 5627 K. These LEDs are the first ones based on amphiphilic CDs. Furthermore, these CDs can be used as luminescent inks and as an active material for solar concentrators.