Spontaneous Formation of Fluorescent Carbon Nanoparticles in Glutaraldehyde Solution and Their Fluorescence Mechanism.

Fluorescent carbon nanoparticles exhibit merits in terms of photochemical stability, functional modification flexibility and excellent biocompatibility. Currently, fluorescent carbon nanoparticles are often obtained by bottom-up or up-bottom strategies. So far, there has been no literature concerning spontaneous formation of fluorescent carbon nanoparticles. However, we have successfully found that fluorescent carbon nanoparticles can form spontaneously in the glutaraldehyde solution. Then further investigations were conducted on the storage time, pH and temperature, which could affect the fluorescence intensity of glutaraldehyde solution. The results indicate that the value of the fluorescence intensity will increase with the extension of the storage time. Moreover, the fluorescence mechanism of the glutaraldehyde solution was studied according to its properties and experiment results. Transmission electron microscopy was used to demonstrate nanoparticles in the glutaraldehyde solution. It's assumed that such phenomenon is probably attributed to the conjugated structure resulting from the polymerization of glutaraldehyde and the quantum confinement effect owing to the nanoparticles formed by the aggregation of polymers. Therefore, the spontaneous fluorescence produced by glutaraldehyde solution provides a simple and environmentally-friendly way to prepare fluorescent carbon nanoparticles.