Phosphorus induced crystallinity in carbon dots for solar light assisted seawater desalination

Abstract

A highly ordered crystalline structure in carbon dots (Cdots) can substantially enhance the gamut of their applications in conversion, transfer and transport of energy; however, achievement of such crystallinity in a controlled manner has been elusive. We report here a facile method for the synthesis of highly crystalline doped Cdots of an average size of 2.8 ± 0.8 nm, that contain nitrogen, sulphur and phosphorus heteroatoms (N,S,P-Cdots). The extent of crystallinity was dependent on the phosphorus content in the doped Cdots. We attempt to understand the nature of phosphorus doping into carbon nanostructures (N,S,P-Cdots) via spectroscopic and microscopic techniques. Based on computational refinement of the powder X-ray diffraction pattern via the LeBail method we propose an orthorhombic crystal structure for N,S,P-Cdots. Importantly, the crystallinity in N,S,P-Cdots significantly enhanced the bulk solar photothermal evaporation efficiency to 83.6%. This phenomenon was further applied towards successful and efficient solar-based seawater desalination.