Growth mechanism, optical and photocatalytic properties of the ZnSe nanosheets constructed by the nanoparticles

► The morphologies changed from isotropic nanoparticles to highly anisotropic nanosheets. ► The nanosheets with a length of up to 4μm exhibited a single crystalline nature. ► Both the nanoparticles and nanosheets showed an NBE peak centered at 422nm. ► The nanosheets were more suitable for the degradation of Rhodamine B. ZnSe nanocrystals with different morphologies were obtained by annealing the precursors via a solvothermal process with different amount of ethylenediamine (EN) (30ml, 40ml, and 50ml). When EN was increased from 30ml to 50ml in the mixed solution, the morphologies changed from isotropic nanoparticles to highly anisotropic nanosheets. The X-ray diffraction (XRD) results showed that both the ZnSe nanoparticles and nanosheets were in the metastable wurtzite crystal phase. The large-scaled ZnSe nanosheets were composed of nanoparticles due to the template effect of the EN. The nanoparticles were found to be uniform with an average size of approximately 7nm, while the large-scale nanosheets had a length of up to 4μm and a width of up to 3μm, and also exhibited a single crystalline nature. Both the nanoparticles and nanosheets showed an near band-edge emission peak centered at 422nm, which was blue-shifted compared to the bulk wurtzite (WZ) structure of ZnSe. The investigation of the photocatalytic activity of the ZnSe nanoparticles and nanosheets showed that the nanosheets were more suitable for the degradation of Rhodamine B under UV radiation.