Multi-color fluorescent carbon dots: Non-size effect dominate graphitized sp2 conjugated domain and surface state energy level co-modulate band-gap.

Multi-color fluorescent carbon dots: Non-size effect dominate graphitized sp2 conjugated domain and surface state energy level co-modulate band-gap.
Chemistry. 2020 Mar 26;:
Authors: Wei S, Yin X, Li H, Du X, Zhang L, Yang Q, Yang R
Abstract
Four types of carbon dots with various color (blue, green, yellow and red) emissions have been synthesized under solvent-free condition from citric acid and different nitrogen sources (DMF, urea, ethanamide and formamide). By detailed characterization and comparion, it is comfimed that the graphitized sp2 conjugated domain and surface functional groups such as C-O and C=N play synergitic roles in adujusting fluorescence properties. Notable, the size effect is not the dominant mechanism to achieve multi-color fluorescence emissions in our work. The structural configuration of carbon dots further influences the energy band structure, as demonstrated in simplified energy level diagrams. An absorption peak ~560nm appears in visible light area for red-emitting f-CDs, assigned to n→π* transition of aromatic structure, thus introducing a new surface state energy level, resulting in reducing the energy of electron transition and the expanding visible region in UV-vis spectrum. Taking advantage of diverse absorption and emission properties, different CDs/TiO2 binary composites are obtained for photocatalytic degradation of organic dyes, and it is found that absorption range in visible light and the ban...

Source: Chemistry - March 25, 2020 Category: Chemistry Authors: Wei S, Yin X, Li H, Du X, Zhang L, Yang Q, Yang R Tags: Chemistry Source Type: research