Dual emission carbon dots from carotenoids: Converting a single emission to dual emission.

Dual emission carbon dots have a high potential for use as fluorescence-based sensors with higher selectivity and sensitivity. This study demonstrated the possibility of conversion of a biological molecular system with a single emission peak to a double emission carbon dots system. This report is the first to describe the synthesis of dual emission carbon dots by tuning the electronic environment of a conjugated system. Here we prepared carbon dots from a natural extract, from which carotenoids were used as a new source for carbon dots. Formation of the carbon dots was confirmed by images obtained under a transmission electron microscope as well as from a dynamic light scattering study. The prepared carbon dots system was characterized and its optical property was monitored. The study showed that, after irradiation with microwaves, the fluorescence intensity of the whole system changed, without any change in the original peak position of the carotenoid but with the appearance of an additional peak. A Fourier transform infrared study confirmed breaking of the conjugated system. When using ethylene glycol as a surface passivating agent added to these carotenoid carbon dots, the dual emission spectra became more distinct.