Synthesis And Properties Of Silicene Quantum Dots Confined In Few-layer Siloxene

Two-dimensional silicene is one of the hotspots in the field of silicon materials research in recent years.Compared with traditional bulk materials,two-dimensional materials have unique physical and chemical properties due to the quantum confinement effect,showing advantages in the fields of optoelectronics,new energy,biomedicine,catalysis and so on.However,large-scale production of high-quality and low-cost two-dimensional silicon materials is still a technical difficulty so far.Based on this,this work has proposed a topochemical reaction method for preparing silicene quantum dots confined in few-layer siloxene nanosheets at room temperature innovatively.The morphological structure,optical properties and photocatalytic hydrogen production activity of the samples have been characterized,and the main results are listed as follows:?1?The morphology,structure and the principle of preparation process of the silicene quantum dots confined in few-layer siloxene nanosheets have been studied.In this work,the thickness of the silicene quantum dots?average diameter less than 4.8nm?confined in few-layer siloxene nanosheets?QD-Siloxene?prepared using CaSi₂ is less than 1.5 nm,which the ethyl acetate is used as the decalcification solvent and FeCl₃·6H₂O is used as the oxidant innovatively.In contrast,EAC-Siloxene and HCl-Siloxene nanosheets both are thicker than 10 nm,and the nanosheets do not contain crystalline silicene quantum dots,confirming that the ethyl acetate can promote the self-organization formation of amorphous silicon-rich regions in the nanosheets during the topochemical reaction,and FeCl₃·6H₂O can contribute to the layered process of the nanosheets and promote the amorphous silicon-rich regions transformed to crystalline silicene quantum dots.?2?The optical properties and luminescence mechanism of the QD-Siloxene,EAC-Siloxene and HCl-Siloxene nanosheets have been studied by UV-visible absorption spectrum,photoluminescence?PL?spectrum and time-resolved PL?TR-PL?measurement.The results are listed as follows:?1?All the three types of the nanosheets exhibit blue light emission.?2?The luminescence of the QD-Siloxene mainly comes from the quasi-direct transition of silicene quantum dots,and the radiative transition from the surface states,interface states and oxygen defects.The luminescence of the EAC-Siloxene and HCl-Siloxene nanosheets mainly due to the defects in the nanosheets.?3?The three types of nanosheets belong to wide band gap semiconductor,and the silicene quantum dots confined in the QD-Siloxene nanosheets show the characteristic of changing from indirect band gap to the quasi-direct band gap due to the quantum confinement effect.?3?The photocatalytic performance of the QD-Siloxene,EAC-Siloxene and HCl-Siloxene nanosheets has been tested.The results are listed as follows:?1?The hydrogen production rate of QD-Siloxene nanosheets is 1126.70?mol·g^-1h^-11 due to the large specific surface area and the silicene quantum dots.?2?The hydrogen production rate of HCl-Siloxene nanosheets is 561.29?mol·g^-1h^-11 because of its smooth surface and the Si-H/Si-OH groups.?3?The hydrogen production rate of EAC-Siloxene nanosheets is only 105.59?mol·g^-1h^-11 due to the thickest thickness and the defects on the surface.