Abstract
Herein, several analytical techniques aimed on validation of separation effectiveness of free molecular fluorophores from citric acid-based carbon dots were elaborated and compared. Generally, chromatographic methods were found more reliable than steady-state optical measurements, pointing at the LC-FLD (liquid chromatography coupled to fluorescence detector) protocols as the most sensitive. Furthermore, the applicability of the frequently reported 1H NMR technique for confirmation of the absence of highly fluorescent free low-molecular weight species in carbon dots samples was called into question. It was found that, in the case of effectively PL emitting compounds (such as 5-oxo-2,3- dihydro-5H-[1,3]thiazolo[3,2-a]pyridine-3,7-dicarboxylic acid (TPA)), the lowest concentration that could be detected with above technique (0.08 mg mL−1 of TPA) is higher than the concentration at which the particular fluorophore shows the brightest PL emission (∼0.01 mg mL−1 of TPA).
Published Version
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