Fluorescent Carbon Nanoparticles: Synthesis, Characterization, and Bioimaging Application

TLDR

Fluorescent carbon nanoparticles (2–6 nm) with ~3 % quantum yield were produced by nitric‑acid oxidation of carbon soot, which incorporates nitrogen and oxygen to confer water solubility and light emission, and size‑selective isolation of the smallest particles further boosts fluorescence. The resulting nanocrystalline, graphitic CNPs emit green fluorescence under UV and readily enter cells without functionalization, enabling fluorescence‑based cell imaging.

Abstract

Fluorescent carbon nanoparticles (CNPs) 2−6 nm in size with a quantum yield of about ∼3% were synthesized via nitric acid oxidation of carbon soot, and this approach can be used for milligram-scale synthesis of these water-soluble particles. These CNPs are nanocrystalline with a predominantly graphitic structure and show green fluorescence under UV exposure. Nitric acid oxidation induces nitrogen and oxygen incorporation into soot particles, which afforded water solubility and a light-emitting property; the isolation of small particles from a mixture of different sized particles improved the fluorescence quantum yield. These CNPs show encouraging cell-imaging applications. They enter into cells without any further functionalization, and the fluorescence property of these particles can be used for fluorescence-based cell imaging applications.