The Source of the Surface Fluorescence of Nanodiamonds

Abstract

In this paper photoluminescence properties of aqueous suspensions of carbon nanoparticles (nanodiamonds, carbon dots and complexes on their basis) with different ratio of surface carbon in sp 3 -and sp 2 -hybridizations were studied by methods of Raman, fluorescence and IR absorption spectroscopy. It was found that intensity of photoluminescence correlates with amount of carbon in non-diamond phase on the surface of nanoparticles. Nanoparticles with high non-diamond carbon phase content revealed more intense photoluminescence. The obtained results support the hypothesis about surface nature of photoluminescence of nanodiamonds and carbon dots.

Surface Photoluminescence of Oxidized Nanodiamonds: Influence of Environment pH

“…The difference in NDs’ PL intensities (of F 0 values) can also be explained by the dependence of the surface PL on the hybridization of surface carbon. In a number of studies, it was suggested that sp 2 -hybridized carbon, not the diamond surface, is the source of the surface PL of NDs. − It follows from Figure a that on the surface of all studied NDs there is indeed the sp 2 -hybridized carbon, varying in amount and state (amorphous or graphitelike). Such differences in surface carbon hybridization can contribute to the observed differences in the intensity of NDs’ PL (Figure ).…”

“…Photoluminescence (PL) of NDs and CDs is also dependent on the properties of nanoparticles’ surfaces and their immediate environment. For NDs, the depednece of PL on their surface chemistry, − on the strength of the environments’ hydrogen bonds, ,, and on interactions with biomolecules ,− allowed us to distinguish the specific type of ND emission:surface photoluminescence, distinct from the well-studied PL of color centers in the diamond core. − Recently, increasingly more authors believe that the source of surface PL of nanodiamonds is the functionalized sp 2 -hybridized carbon on their surfaces. − …”