Investigations Into Shape-controlled Synthesis And Correlated Photoluminescence Properties Of 4.5-monolayers Thick Cdse Quantum Wells With Zinc-blende Structure

Nanomaterials have strong morphology-dependence properties,and have great significance in basic research and technical applications.Due to the wide application semiconductor nanomaterials are an important branch of nanomaterials.II-VI semiconductor nanomaterials have attracted much attention in the fields of chemistry,optics,medicine,electricity,magnetism and so on,as a result of their outstanding optical properties,such as broad absorption range,narrow emission peak,high fluorescence efficiency,and good optical stability.The two-dimensional(2D)semiconductor nanomaterials(quantum wells)with uniform thickness in the entire quantum confinement regime,have excellent optical properties such as an adjustable and range-narrow emission.CdSe quantum wells are ideal luminescent materials in photovoltaics,light-emitting diode,bio-imaging luminescent markers,ink-jet printable large area displays and many other applications,due to their simple synthesis,good chemical stability,wide color gamut,excellent color purity and high fluorescence efficiency.This thesis aims to study the shape control of CdSe quantum wells,which are 4.5-monolayer zinc-blende structure,and the synthesis of a series of luminescence emission-tunable quantum wells.For quantum wells,shape and size are an important parameter.The shape of quantum wells is a key condition influencing the self-assembly.(1)In chapter 2,we changed the content of water in cadmium acetate and injecting water and solvent(ODE)at high temperature to control the size and shape of CdSe quantum wells.The common synthesis methods of CdSe quantum wells are based on continuously extended lateral mechanism.The synthesis of zinc-blende structure CdSe quantum wells is mainly divided into two steps: in the first step,selenium precursor and cadmium precursor reacted to form the right size seeds;in the second step,after adding cadmium acetate the quantum wells extend laterally through continuous reaction of Cd and Se precursors.Cadmium acetate plays an important role in the synthesis process and is indispensable.Bas ed on the above theory,we can control the shape and size of quantum wells by changing the ratio of cadmium acetate dihydrate to anhydrous cadmium acetate,and the amount of water added to the reaction.After optimization,to acquire ideal-shape quantum well,the molar ratio of cadmium acetate dihydrate to anhydrous cadmium acetate should be 1:1.(1)In chapter 3,based on the size-and shape-dependence of nanoparticles,we synthesized CdSe quantum wells with continuously tunable photoluminescence(PL)positions by one-pot colloidal synthesis.The CdSe 2D nanocrystals are only quantunm confined in the thickness direction.Because diverse properties of CdSe quantum wells are determined by their ultrathin thickness,the fluorescence emission of atomic flat CdSe quantum wells is very narrow and has a very high photoluminescent color purity.Because of the strong dependence of size and shape,we can obtain the CdSe quantum wells emitted at different wavelengths by controlling the synthesis method,the synthesis temperature,and the molar ratio of cadmium acetate.We have acquired a series of new PL peak position-tunable 4.5-monolayers thick CdSe quantum wells,emitting from 513 nm to 523 nm.