Photoluminescence of Carbon Nanodots: Dipole Emission Centers and Electron–Phonon Coupling

Abstract

Inorganic carbon nanomaterials, also called carbon nanodots, exhibit a strong photoluminescence with unusual properties and, thus, have been the focus of intense research. Nonetheless, the origin of their photoluminescence is still unclear and the subject of scientific debates. Here, we present a single particle comprehensive study of carbon nanodot photoluminescence, which combines emission and lifetime spectroscopy, defocused emission dipole imaging, azimuthally polarized excitation dipole scanning, nanocavity-based quantum yield measurements, high resolution transmission electron microscopy, and atomic force microscopy. We find that photoluminescent carbon nanodots behave as electric dipoles, both in absorption and emission, and that their emission originates from the recombination of photogenerated charges on defect centers involving a strong coupling between the electronic transition and collective vibrations of the lattice structure.

Size-controllable polypyrrole nanospheres synthesized in the presence of phosphorylated chitosan and their size effect in different applications

“…9, which show that CDs are introduced successfully onto the surface of PPy nanospheres due to the p-p interaction between the PPy and the sp 2 p clouds of CDs (Li et al 2013). The CDs with a size of 3-5 nm present a lattice structure with the lattice spacing of 0.26 nm, which corresponds to the (100) crystal plane of graphite (Ghosh et al 2014).…”

Carbon Nanodots: Supramolecular Electron Donor–Acceptor Hybrids Featuring Perylenediimides

“…[21][22][23] Whatever the synthesis route,t he sizes of CNDs typically range from 1-10 nm with different numbers of stacked graphene layers that are saturated with functional groups at their periphery.I mportantly,t heir facile synthesis and low cost make CNDs promising replacements for expensive organic dyes in optoelectronic applications. [21,[24][25][26][27][28] Thec harge-transfer activity of CNDs has recently been explored, both in ground and excited states, [27,29] for the excited states this was done in conjunction with av ariety of electron donors and acceptors. [26,30] Fori nstance,C NDs have been used together with complementary forms of nanocarbons,s uch as fullerenes,c arbon nanotubes,g raphene,i n tailored charge-transfer systems.Inaleading example,CNDs have been combined with single-walled carbon nanotubes (SWCNTs) affording supramolecular nanohybrids,i nw hich the components function as electron donors and acceptors.…”

Using carbon nanodots as inexpensive and environmentally friendly sensitizers in mesoscopic solar cells

“…It has been proposed that such trap states in the bandgap play an important role for the photoluminescence of CNDs, 16,25,26 and that the trapping effect consists of energy transfer between p-conjugated subdomains within single particles or with the recombination of photogenerated charges at defect centers. 27,28 We found that the fluorescence intensity of CND1 is significantly quenched under acidic conditions (pH 1). Similarly, the absorption in the visible region is reduced - Fig.…”