%0 Journal Article
%A Meierhofer, Florian
%A Weigert, Florian
%A Dissinger, Frank
%A Jungclaus, Jörgen
%A Müller-Caspary, Knut
%A Waldvogel, Siegfried R.
%A Resch-Genger, Ute
%A Voss, Tobias
%T Citric Acid Based Carbon Dots with Amine Type Stabilizers: pH-Specific Luminescence and Quantum Yield Characteristics
%J The journal of physical chemistry  / C
%V 124
%N 16
%@ 1932-7455
%C Washington, DC
%I Soc.
%M FZJ-2021-02908
%P 8894 - 8904
%D 2020
%X We report the synthesis and spectroscopic characteristics of two different sets of carbon dots (CDs) formed by hydrothermal reaction between citric acid and polyethylenimine (PEI) or 2,3-diaminopyridine (DAP). Although the formation of amide-based species and the presence of citrazinic acid type derivates assumed to be responsible for a blue emission is confirmed for both CDs by elemental analysis, infrared spectroscopy, and mass spectrometry, a higher abundance of sp2-hybridized nitrogen is observed for DAP-based CDs, which causes a red-shift of the n-π* absorption band relative to the one of PEI-based CDs. These CD systems possess high photoluminescence quantum yields (QY) of ∼40% and ∼48% at neutral pH, demonstrating a possible tuning of the optical properties by the amine precursor. pH-Dependent spectroscopic studies revealed a drop in QY to < 9% (pH ∼ 1) and < 21% (pH ∼ 12) for both types of CDs under acidic and basic conditions. In contrast, significant differences in the pH-dependency of the n-π* transitions are found for both CD types which are ascribed to different (de)protonation sequences of the CD-specific fluorophores and functional groups using zeta potential analysis.
%F PUB:(DE-HGF)16
%9 Journal Article
%U <Go to ISI:>//WOS:000529225800047
%R 10.1021/acs.jpcc.9b11732
%U https://juser.fz-juelich.de/record/893896