One-step synthesis of carbon nanoparticles and yellow to blue fluorescent nanocarbons in flame reactors

We propose a one-step synthesis for the large production of carbon nanoparticles (CNP) based on a flame reactor synthesis approach in which the key tunable parameter is the fuel composition. Specifically, the properties of CNP including fluorescent nanocarbons could be varied by fueling a premixed flame with mixtures ranging from ethylene to benzene. CNP characterization was carried out through Raman and UV-Visible spectroscopy defining their in-plane crystallite size and optical band gap. By simply changing the relative percentages of ethylene/benzene in the fuel it is shown how CNP properties can be tuned, fixing the optical band gap and changing the crystallinity and particle size, or viceversa fixing the crystallinity and changing the optical band gap and particle size. Fluorescent nanocarbons presenting typical carbon nanodot characteristics could be obtained by extraction and simple filtration (<20 nm) of CNP. By changing the fuel composition, nanocarbons fluorescing from yellow to blue and showing a quantum yield moving from 3 to 10% could be easily produced. The properties of CNP and of their fluorescent fraction (<20 nm) are directly defined by the flame reactor conditions without any further modifications that is a key advantage for large-scale production of CNP and especially of fluorescent nanocarbons.