||Fluorescent nano-diamond(FND) is an unique fluorescence bio-labeling materials, which exhibit good fluorescence yield, excellent photostability, and non-toxicity. The emission color of FND is determined by the defect centers in the diamond crystal. When the defect center composed of one vacancy and two nearest-neighborhood nitrogen substitutes, it forms a H3 center. H3 center has a zero-phonon line at 496nm , and a broadband green emission around 530 nm,. When the FND contains lots of H3 centers, the emission color is green, hence it’s called green FND(gFND).|
Since H3 centers composed of two nitrogen substitutes, it is naturally to fabricate the gFNDs by diamonds with high nitrogen substitutes. However, H3 center is not the only products when the diamond contains many nitrogen substitutes, and high density of vacancies. Other type of defect centers (NV-, NV0, …) exhibit lower energy gap, and quench the emission of H3 centers.
In this thesis, it aims to study the spectroscopic homogeneity of the gFNDs. Comparing the intensity of the scattering images and the corresponding fluorescence images, it provides the information of the relation between particle size and the density of color centers. Furthermore, images with different color filters are compared to provide the information of the composition of defect structures. Fluorescence lifetime image is performed for the emission dynamics of the nano-particle. The results indicate that the decay lifetime has an relation to the emission intensity. When the nano-particle contains more color centers, it quenches the emission from H3 centers more.