A comparative study on impact factors of emission: surface state, carbonaceous core, and size based on series of exactly designed P, S co-doped carbon dots

Heteroatoms, such as nitrogen, sulfur, and phosphorus, in surface state dedicate the passivation layer, which along with the structure of carbonaceous core (the size of conjugated sp(2) domains) and diameter in carbon dots affect the emission. To disclose the dominant one among them, two series of well-designed P, S co-doped carbon dots (P/S-CDots) possessing different particle sizes and individual chemical structures both in surface and core were prepared. As results, the concentration of sp2 hybrid carbon atom in carbonaceous core plays the vital role in effecting the photoluminescence efficiency of carbon dots by determining the optical-harvesting ability, followed by heteroatom's doping amount. Besides, phosphorus is superior to sulfurs regarding to improving the photoluminescence efficiency based on the calculated results of LUMO-HOMO gap. It is worth mentioning that the copolymer as precursor is very qualified in the paper, because that the structure and diameter of P, S-CDots are easy to be manipulated by managing the chain structure and molecular weight of it, which is a terpolymer prepared by free radical polymerization using acrylic phosphate, sodium methylallyl sulfonate, and acrylic acid as monomers in the presence of ammonium persulfate.