Effect of the surface chemistry on the photoluminescence properties of boron doped carbon dots

Two boron-doped carbon dots (BCDs), CABA and TBBA, were prepared from various boron and carbon containing precursors using a bottom-up approach. The BCDs’ chemistry and morphology were evaluated by IR, XPS and TEM analyses. The surface of BCDs was rich in surface functional groups including CB, B–O, CO and CO bonds. Their optical properties were analyzed by UV–vis, excitation and fluorescence spectroscopy. BCDs solutions, when excited at 350 nm, emitted fluorescent light with a maximum at 420−430 nm (in a violet range). The excitation spectra of BCDs were deconvoluted into three components centered respectively at 250, at around 320 and at 350 nm. The excitation peak at 250 nm was linked to the CC bonds, the one around 320 nm - to the CB bonds and the one at 350 nm - to the CO/CO bonds. The calculated quantum yields varied between 1.7 and 9.5 %. The latter number corresponds to one of the best fluorescence quantum yields reported for BCDs. This study highlighted the importance of the surface chemistry and especially of the CB and CO/CO bonds in governing the photoluminescence of BCDs. The highest quantum yield was found for BCDs with a highcontribution of CB and COB bonds and a small contribution of CO bonds.