Insight into modulation of Carbon dot optical sensing attributes through reduction pathway

Oxidized/reduced carbon dots (CDs) with tunable optical features have been emerged as a new class of CDs having a common “molecular origin” but different fluorescence (FL) behavior. In the present work, using “banana peel” as a sole carbon source followed by doping with the fluorine (F), boron (B) and nitrogen (N) over CDs (BP-CDs), were synthesized using well known hydrothermal synthesis method. Moreover, as synthesized BP-CDs were further reduced to “rBP-CDs” by NaBH₄. Post reduction, the FL performance (i.e., lifetime value and quantum yield) of rBP-CDs were found to be enhanced as compared with the BP-CDs along with variation in excitation and emission wavelength. Interestingly, the optical sensing attribute of BP-CDs and rBP-CDs were changed i.e., BP-CDs selectively sense “Co²⁺ with a limit of detection (LOD) value of 180 nM”, whereas rBP-CDs detected Co²⁺ (with LOD value of 242 nM) as well as Hg²⁺ (with LOD value of 190 nM). To the best of our knowledge, this work presents the very first report on the modulation of CDs sensing behavior after reduction. The modulation in sensing behavior with the common carbon precursor and reduction paves a new possibility for exploring CDs for different commercial applications.