Pressure-Resistance Of Magic-Sized Cadmium Selenide Nanocrystals

Magic-sized Nanocrystals（MSNs）have attracted much attention because of their stable structure,accurate to atomic composition and extremely small particle size,which show physical and chemical properties different from those of conventional quantum dots.In terms of composition and size,Magic-sized nanocrystals exhibit similar properties to ultra-small nanocrystals,but there are two basic characteristics that can be used to distinguish MSNs from ultra-small nanocrystals,namely absorption peak width and growth mechanism type.The narrow absorption band of MSNs is due to the fact that the number of atoms it has is not arbitrary,but exactly equal to a"magic number",in this case,the so-called"magic number"refers to the coordinated with central atom,resulting in a stable,compact arrangement of structure,a typical example of which is the fullerenes group,including C₆₀ and C₇₀ and C₈₄.In addition,during the synthesis process,with the extension of reaction period or the increase of temperature,the growth of MSNs is not continuous,the absorption peak does not change continuously,but the structure is very stable.People are concerned about the magic size of cadmium selenide nanocrystals.Through continuous exploration and research on the ir synthesis methods,many kinds of MSNs with different sizes have been successfully prepared.Due to the narrow band and size dependence of CdSe nanocrystals,their photoluminescence properties have attracted attention.We know that photoluminescence intensity and wavelength are two key parameters to evaluate the performance of optoelectronic devices.Up to now,a series of innovative achievements have been made in enhancing the photoluminescence intensity of CdSe nanocrystals by means of shell less surface passivation,low temperature suppression of non-radiative recombination and the introduction of cations.MSNs CdSe are the products of the stage from nucleation to growth of nanocrystals.Compared to the quantum dots that people like to study before,MSNs CdSe show a narrow absorption peak and a stable peak position,which is mainly due to the precise atomic ratio and the singularity of the size of the material,resulting in a very small spread of the non-uniform spectrum lines.And pressure,which is thought of as a thermodynamic parameter in addition to temperature and chemical composition,can largely change the way electrons bond,changing the orbital behavior between clouds of electrons by changing the distance between the atoms,thus changing the behavior of electron orbitals and the way of bonding.As early as the 1990s,the optical response of CdSe nanocrystals under high pressure was firstly studied,and subsequent high pressure theories and experiments were promoted.Researchers have made new research achievements in pressure response.However,there are relatively few studies on the optical compressive stability under pressure,and there is no research on the effect of pressure on Magic-sized materials.The evaluation and testing of the stability of MSNs CdSe materials under pressure will not only help to explore the general relationship between the structure of MSNs materials and their optical properties,but also provide references for the research and development of more stable new optoelectronic materials,so as to develop optical devices resistant to high pressure.In this study,MSNs CdSe was synthesized by colloidal chemical method to explore the optical response and stability of the prepared MSNs CdSe under pressure.The MSNs CdSe synthesized under normal pressure can still maintain good stability under pressure.The high pressure fluorescence spectra and high pressure UV-Vis absorption spectra of MSNs CdSe show that the emission and absorption peaks of MSNs CdSe remain unchanged with the increase of pressure.This stable behavior under pressure is contrary to the sensitive characteristics of traditional nanomaterials under external pressure.After decompression,MSNs CdSe maintained its initial structure and morphology at normal pressure.MSNs CdSe show good pressure resistance during compression,which is helpful for the research of magic size nanomaterials under extreme compression conditions.