title: White carbon: Fluorescent carbon nanoparticles with tunable quantum yield in a reproducible green synthesis.
abstract: In this study, a new reliable, economic, and environmentally-friendly one-step synthesis is established to obtain carbon nanodots (CNDs) with well-defined and reproducible photoluminescence (PL) properties via the microwave-assisted hydrothermal treatment of starch and Tris-acetate-EDTA (TAE) buffer as carbon sources. Three kinds of CNDs are prepared using different sets of above mentioned starting materials. The as-synthesized CNDs: C-CND (starch only), N-CND 1 (starch in TAE) and N-CND 2 (TAE only) exhibit highly homogenous PL and are ready to use without need for further purification. The CNDs are stable over a long period of time (>1 year) either in solution or as freeze-dried powder. Depending on starting material, CNDs with PL quantum yield (PLQY) ranging from less than 1% up to 28% are obtained. The influence of the precursor concentration, reaction time and type of additives on the optical properties (UV-Vis absorption, PL emission spectrum and PLQY) is carefully investigated, providing insight into the chemical processes that occur during CND formation. Remarkably, upon freeze-drying the initially brown CND-solution turns into a non-fluorescent white/slightly brown powder which recovers PL in aqueous solution and can potentially be applied as fluorescent marker in bio-imaging, as a reduction agent or as a photocatalyst.
authors.affiliation: Physical Chemistry, Institute of Chemistry, University of Potsdam, 14476 Potsdam-Golm, Germany.
authors.forename: Till T
authors.initials: TT
authors.lastname: Meiling
authors.affiliation: Functional Materials and Devices, Fraunhofer Institute for Applied Polymer Research, 14476 Potsdam-Golm, Germany.|Coordination Complexes and Functional Materials, Institute of Physical Chemistry, Polish Academy of Sciences, 01-224 Warsaw, Poland.
authors.forename: Piotr J
authors.initials: PJ
authors.lastname: Cywiński
authors.affiliation: Physical Chemistry, Institute of Chemistry, University of Potsdam, 14476 Potsdam-Golm, Germany.|BAM, Federal Institute of Material Research and Testing, 12489 Berlin, Germany.
authors.forename: Ilko
authors.initials: I
authors.lastname: Bald