Biobased carbon dots as photoreductants – an investigation by using triarylsulfonium salts

We investigated the potential application of six types of carbon dots (CDs) obtained from different organic sources as photoreductants. Such carbon nanomaterials were synthesized by two different approaches, either hydrothermal or pyrolytic, from citric acid and glucose as the starting organic substrates. On the other hand, carbon dots deriving from fishery waste (bass scales) and fruit processing waste (blackberries) have been also prepared. Diethylenetriamine was employed in some cases as the nitrogen source. The hydrothermal syntheses yielded amorphous CDs, which were either non-doped (a-CDs) or nitrogen-doped (a-N-CDs), whereas the pyrolytic treatment afforded graphitic CDs (g-CDs). The efficiency of the so obtained carbon nanomaterials was studied in the model photoreduction reaction of triarylsulfonium salts to diaryl sulfides. A comparison carried out on the results obtained points out the key role of the starting substrates in determining the photophysics and the photochemical efficiency of the resulting CDs. In this context, citric acid-derived materials (both graphitic and amorphous) were found as the most promising materials, while less satisfactory results have been observed when using CDs derived from glucose and biowastes.