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Carbon dots (CDots) are a promising biocompatible nanoscale source of light, yet the origin of their emission remains under debate. Here, we show that all the distinctive optical properties of CDots, including the giant Stokes shift of photoluminescence and the strong dependence of emission color on excitation wavelength, can be explained by the linear optical response of the partially sp-hybridized carbon domains located on the surface of the CDots' sp-hybridized amorphous cores. Using a simple quantum chemical approach, we show that the domain hybridization factor determines the localization of electrons and the electronic bandgap inside the domains, and analyze how the distribution of this factor affects the emission properties of CDots. Our calculation data fully agree with the experimental optical properties of CDots, confirming the overall theoretical picture underlying the model. It is also demonstrated that fabrication of CDots with large hybridization factors of carbon domains shifts their emission to the red side of the visible spectrum, without a need to modify the size or shape of the CDots. Our theoretical model provides a useful tool for experimentalists and may lead to extending the applications of CDots in biophysics, optoelectronics, and photovoltaics.
This article was published in the following journal.
Name: ACS nano
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Stable carbon atoms that have the same atomic number as the element carbon, but differ in atomic weight. C-13 is a stable carbon isotope.
The method of measuring the dispersion of an optically active molecule to determine the relative magnitude of right- or left-handed components and sometimes structural features of the molecule.
Lanthanum. The prototypical element in the rare earth family of metals. It has the atomic symbol La, atomic number 57, and atomic weight 138.91. Lanthanide ion is used in experimental biology as a calcium antagonist; lanthanum oxide improves the optical properties of glass.
A nonmetallic element with atomic symbol C, atomic number 6, and atomic weight 12.011. It may occur as several different allotropes including DIAMOND; CHARCOAL; and GRAPHITE; and as SOOT from incompletely burned fuel.
Unstable isotopes of carbon that decay or disintegrate emitting radiation. C atoms with atomic weights 10, 11, and 14-16 are radioactive carbon isotopes.