Highly fluorescent green and red emissions from boron-doped graphene quantum dots under blue light illumination

Highly fluorescent boron-doped graphene quantum dots (B-doped GQDs, average particle size of ∼4 nm) are synthesized via one-pot solvothermal route in the presence of 1,3,6-trinitropyrene (TNP) and boric acid. The chemical ratio of the boric acid to TNP precursor is identified as a crucial factor in modulating the B-dopant concentration within the GQD lattices. The GQD suspensions maintain uniform dispersion over extended operation thanks to the NO2 groups formed in the GQD edge sites promoting high dispersivity in polar and nonpolar solvents. The B-doped GQD suspensions are homogeneously stored in n-hexane and propylene glycol methyl ether acetate, enabling highly fluorescent green and red emission, respectively. Under the blue-light illumination, the green emission takes place at ca. 541 nm with a narrow full width at half maximum (FWHM) of 31.7 nm, whereas the red emission centers at ca. 617 nm with a FWHM of 42.5 nm. Through adjusting the concentration of B-dopant, the quantum yield of green and red fluorescence reached as high as 99.8 and 17.1%, respectively. Accordingly, the novel solvothermal synthesis route developed in this work provides the essential framework for engineering B-doped GQDs with tunable optical properties for high-performance biosensors and biomedical devices.