A novel hydrothermal approach to preparing ZnO flower-like using CQDs as growth seeds.

[Display omitted] • CQDs grown with Malva sylvestris. • CQDs are used as seeds for the hydrothermal nucleation and growth of ZnO. • CQDs/ZnO has a flower-like morphology. • Under the same hydrothermal conditions, ZnO nanosheets grow without Malva sylvestris. • CQDs/ZnO flowers demonstrate excellent methylene blue degradation. This study presents a new synthesis route to prepare ZnO flower-like particles. Firstly, carbon quantum dots (CQDs) were prepared hydrothermally, using the Malva sylvestris flower as the sole carbon source. Subsequently, flower-like particles of ZnO/CQDs were synthesized using CQDs seeds and the same hydrothermal process. The efficiency of the redox process of solar excitation was measured by reducing the dye methylene blue (MB). The SEM and TEM characterization shows ZnO flower-like particles of around 1.5 µm whose petals are formed by crystallites of around 10 nm. ZnO nanocrystals appear embedded in an amorphous carbon matrix. TEM images show carbon quantum dots on the surface of ZnO flowers. Without using Malva sylvestris , ZnO morphologies are not formed; instead, 2D nanolaminates appear. The ZnO/CQDs nanocomposite achieved 98 % MB degradation in 80 min. The small size of CQDs can be a good scenario for the growth of crystalline nanostructures using the nanocarbon seed. [ABSTRACT FROM AUTHOR]