Amphiphilic Carbon Dots with Excitation-Independent Double-Emissions

Developing total carbon-based multicolor emissive carbon dots (Cdots), especially amphiphilic Cdots (A-Cdots) with several luminescent bands and limited emissive sites, is still a challenge. Herein, A-Cdots with bright excitation-independent blue/yellow photoluminescence (PL) bands from two types of fluorophores are synthesized by the solvothermal treatment of citric acid and dodecylamine in cyclohexane (c-hexane) solution. Due to the hydrogen-bonding interaction of carboxylic groups linked with A-Cdots and the hydrophobic effects of long-chain alkyl groups, assemblies of A-Cdots with reversed micelle-like structure formed in c-hexane solution lead to remarkable yellow-PL (y-PL) with quantum yield of 33.1%. Time-resolved fluorescence and the distinct solvation effects of A-Cdots conclude that the blue-PL and y-PL are from the radiative recombination of emissive sites of amide and carboxylic groups. For the solvent-dependent optical properties and the amplification effect of dual-color PL, the A-Cdots exhibit good potential in the very sensitive detection of trace impurities in alkane solution, such as ethanol in c-hexane with content as low as 0.033% (v/v). With A-Cdots as phosphors, white-light-emitting diodes (WLEDs) are successfully constructed with luminous efficiency of 52.72 lm W-1. This work provides a new thinking for the design of multicolor luminous Cdots materials and their potential applications.