Synthesis of Highly Fluorescent Yellow‐Green N‐Doped Carbon Nanorings for pH Variation Detection and Bioimaging

A facile and direct chemical route is developed to produce intercrossed N‐doped graphene carbon nanorings (N‐CNRs) with a high yellow‐green photoluminescence emission in both solid and aqueous states. The N‐CNRs are directly synthesized at an elevated temperature in an inert atmosphere without additional pressure using urea and sodium citrate as raw materials. N‐CNRs have a photoluminescence change phenomenon from green to blue when the pH is altered from a neutral to a base value. The luminescence mechanism is analyzed under absorbance and lifetime decay, X‐ray photoelectron spectra, and X‐ray absorption near edge structure spectroscopy. Results indicate how the optical properties are tuned. The fluorescence bioimaging of zebrafish using N‐CNRs as the probe is also studied in terms of zebrafish husbandry, embryo harvesting, and the introduction of N‐CNRs into embryos and juveniles by soaking and microinjection. The prepared N‐CNRs serve as a promising fluorescent probe for pH variation analysis, and bioimaging. The N‐CNTs show potential for use in air purification applications. A facile and direct chemical route is developed to produce intercrossed N‐doped graphene carbon nanorings with a high yellow‐green photoluminescence emission in both solid and aqueous states. It could be utilized as a promising fluorescent probe for pH variation analysis bioimaging and particulate matter adsorption.