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

• Published in: Nano letters Vol. 14; no. 10; pp. 5656 - 5661
• Main Authors: Ghosh, Siddharth, Chizhik, Anna M, Karedla, Narain, Dekaliuk, Mariia O, Gregor, Ingo, Schuhmann, Henning, Seibt, Michael, Bodensiek, Kai, Schaap, Iwan A. T, Schulz, Olaf, Demchenko, Alexander P, Enderlein, Jörg, Chizhik, Alexey I
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 08.10.2014
• Subjects: Carbon; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Dipoles; Electronics; Emission analysis; Emission spectroscopy; Exact sciences and technology; Joining; Lattice dynamics; Materials science; Nanocrystalline materials; Nanoscale materials and structures: fabrication and characterization; Nanostructure; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures; Phonon-electron and phonon-phonon interactions; Phonons and vibrations in crystal lattices; Phonons in low-dimensional structures and small particles; Photoluminescence; Physics; carbon nanodots; electron−phonon coupling; nanotechnology; transition dipole moment; nanoparticles; fluorescence; Vibrations; Lifetime; Transmission electron microscopy; Imaging; Photoluminescence; Electronic transition; Electron-phonon interactions; Nanodot; Quantum yield; Carbon; Nanostructured materials
• ISSN: 1530-6984; 1530-6992; 1530-6992
• DOI: 10.1021/nl502372x

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.