TY  - JOUR
A1  - Strauss, Volker
A1  - Wang, Huize
A1  - Delacroix, Simon
A1  - Ledendecker, Marc
A1  - Wessig, Pablo
T1  - Carbon nanodots revised
BT  - the thermal citric acid/urea reaction
JF  - Chemical science
N2  - Luminescent compounds obtained from the thermal reaction of citric acid and urea have been studied and utilized in different applications in the past few years. The identified reaction products range from carbon nitrides over graphitic carbon to distinct molecular fluorophores. On the other hand, the solid, non-fluorescent reaction product produced at higher temperatures has been found to be a valuable precursor for the CO2-laser-assisted carbonization reaction in carbon laser-patterning. This work addresses the question of structural identification of both, the fluorescent and non-fluorescent reaction products obtained in the thermal reaction of citric acid and urea. The reaction products produced during autoclave-microwave reactions in the melt were thoroughly investigated as a function of the reaction temperature and the reaction products were subsequently separated by a series of solvent extractions and column chromatography. The evolution of a green molecular fluorophore, namely HPPT, was confirmed and a full characterization study on its structure and photophysical properties was conducted. The additional blue fluorescence is attributed to oligomeric ureas, which was confirmed by complementary optical and structural characterization. These two components form strong hydrogen-bond networks which eventually react to form solid, semi-crystalline particles with a size of similar to 7 nm and an elemental composition of 46% C, 22% N, and 29% O. The structural features and properties of all three main components were investigated in a comprehensive characterization study.
Y1  - 2020
U6  - https://doi.org/10.1039/d0sc01605e
SN  - 2041-6520
SN  - 2041-6539
VL  - 11
IS  - 31
SP  - 8256
EP  - 8266
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  -