Calcium-doped fluorescent carbon nanoparticles: Spontaneous thermal synthesis, pH-sensitive fluorescence off-on, and mechanism

Spontaneous thermal polymerization and carbonization assisted by calcium oxide was proposed for the first time to develop an incomparable synthetic route for the production of calcium-doped fluorescent carbon nanoparticles (FCNPs). This unique approach shares numerous virtues such as eco-friendly, moderate and controllable reaction, and uninvolved poisonous chemicals and intricate operations. Apart from several excellent photoluminescence properties of ordinary fluorescent nanomaterials, the FCNPs exhibited unexceptionable features in stark contrast to previous reports, especially possessing pH-sensitive fluorescence "off-on", thermosensitivity, and superior optical performances under alkaline condition. Furthermore, the formation processes dramatically influencing the nucleation and growth of FCNPs were meticulously discussed according to the detailed material characterization. These investigations revealed the function of doping calcium and the fabrications of carbogenic cores coupled with oxygen-containing groups served as photoluminescence center and edge. It can be speculated that the synthesis of FCNPs will inaugurate new avenues for the design of multifunctional composites with other biomaterials and expand their applications in extreme alkaline conditions. (C) 2018 Published by Elsevier B.V.