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C: Physical Processes in Nanomaterials and Nanostructures
Tailoring the Emission Color of Carbon Dots through Nitrogen-Induced Changes of Their Crystalline Structure Luisa Sciortino, Alice Sciortino, Radian Popescu, Reinhard Schneider, Dagmar Gerthsen, Simonpietro Agnello, Marco Cannas, and Fabrizio Messina J. Phys. Chem. C, Just Accepted Manuscript • DOI: 10.1021/acs.jpcc.8b04514 • Publication Date (Web): 16 Jul 2018 Downloaded from http://pubs.acs.org on July 17, 2018
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The Journal of Physical Chemistry
Tailoring the Emission Color of Carbon Dots Through
Nitrogen-Induced
Changes
of
Their
Crystalline Structure Luisa Sciortino,a Alice Sciortino,a,b Radian Popescu,c Reinhard Schneider,c Dagmar Gerthsen,c Simonpietro Agnello,a,d Marco Cannas,a Fabrizio Messinaa,d*. a
Dipartimento di Fisica e Chimica, Università degli Studi di Palermo, Via Archirafi 36, 90123
Palermo b
Dipartimento di Fisica ed Astronomia, Università degli Studi di Catania, Via Santa Sofia 64,
95123 Catania, Italy c
Laboratory for Electron Microscopy, Karlsruhe Institute of Technology, Engesserstrasse 7,
76131 Karlsruhe, Germany d
CHAB – ATeN Center – Università degli Studi di Palermo, Viale delle Scienze, Edificio 18,
9018 Palermo, Italy.
ABSTRACT
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Nitrogen content in carbon dots plays a crucial role both on the structure and on the optical properties. We synthesized two distinct families of CDs which differ both in structure and in the optical emission, demonstrating how nitrogen determines the structure and the optical properties of N-carbon dots in two main cases: low content and high content of nitrogen. While the lownitrogen-content family is characterized by blue-emitting nanoparticles with a N-doped hexagonal C-graphite crystalline core structure and a complex surface structure, the highnitrogen-content family is composed by nanoparticles behaving as dual emitters (blue and green) with a hexagonal β-C3N4 crystalline core structure and a high amount of amide groups grafted on the surface. Our data demonstrate clearly that the nitrogen is not simply a doping agent but it can also have a decisive role on the structure of carbon dots, which directly reflects into their optical properties. The emission mechanisms of the two types of N-doped CDs are discussed and related to their different structures.
INTRODUCTION Carbonaceous materials were traditionally considered non-luminescent until the first directed synthesis of Carbon Dots (CDs) was performed about a decade ago,
1
demonstrating the
capability of such a new class of C-based nanoparticles to display an intense and tunable fluorescence. Since then, CDs have been widely investigated because of their outstanding features such as large biocompatibility, several common solvents,
4,5
2
high quantum yield,
3
and strong interaction with
and a plethora of possible applications have been proposed,
instance in catalysis, 7 sensing,
8,9
6
for
light-emitting materials, nanocomposites and devices,10,11,12,13
and optical imaging.14 Nowadays, CDs have achieved an important and still growing position in
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The Journal of Physical Chemistry
the scientific literature due to their remarkable optical emission.
15,16,17,18
While a small size of
the dots (
