Acid treatment to tune the optical properties of carbon quantum dots

The photophysical properties of carbon quantum dots (CQDs) can be manipulated by doping external elements to control photoluminescence (PL) emission wavelength and enhance quantum yield during either growth or post-treatment. However, the utilization of CQDs has been limited by broad bandwidth of emission and the requirements of a multi-step purification processes. Here, we report an efficient process – a simple acid treatment (H2SO4 or HCl) - for producing nitrogen-doped carbon quantum dots (NCQDs) capable of multicolor emission. Using this acid treatment, the full-width half maximum (FWHM) of the resulting NCQDs PL emissions can be narrowed by approximately 46 nm in the visible light region. We also determined that the crystallinity of the NCQDs can be enhanced without any significant changes in the density of oxygen-included functional groups, and the lifetime of the charge carriers falls within a range of 3.36 and 6.27 ns. We anticipate that our approach will allow for the practical utilization of NCQDs in a variety of optoelectronic devices in the near future.