Upconverting carbon quantum dots: An eco-friendly material for light energy harvesting and bio-imaging

Eco-friendly carbon quantum dots (CQDs) are finding many applications in the field of chemical sensing, photocatalytic applications, photovoltaic applications, bio-imaging, etc. Herein, CQDs are grown via a cost-effective manner, where the lemon and onion extracts are used as the reaction precursors. Formed CQDs are characterized using electronic spectroscopic and microscopic techniques. The emission yield of the present CQDs is found to be 11.2%. In contrast to general fluorophores/ semiconductors, this material showed an upconverting photoluminescence. Upon exciting with a lower energy continuous wave light of 695 nm, we observed an upconverted emission centered at 438 nm. For upconversion, as the excitation wavelength is at the lower energy, the photodecomposition of the material will be minimum. This will increase the efficiency and the lifetime of the light harvesting devices as the photodecomposition is minimum at lower wavelengths. Also, upconverting CQDs can be a potential candidate for the bio-imaging applications as the light induced decomposition of the biological samples will be minimum. (C) 2019 Elsevier Ltd. All rights reserved.