Preparation And Performance Of CdS Quantum Dots Nanocomposites

Nanomaterials have developed rapidly since the 21st century.Semiconductor quantum dots?QDS?are an important field in the scope of nanomaterials due to their special structure and properties.The sizes of QDs are between bulk materials and molecules,and their sizes are limited on the three-dimensional direction,showing quantum size effect and surface effect.Moreover,the luminescence of QDs depends on their sizes,so QDs with different optical properties can be obtained by controlling the size of them when being prepared.This nature makes QDs obtain great potential and research value in nonlinear optical response,medicine and photoelectric materials.However,there are still some problems.Quantum dots are prone to agglomeration and form surface defects in the process of combination with polymers,which will lead to non-radiative transition of electrons and decrease the luminous performances.In addition,as an inorganic nanocrystals,QDs are unable to compatible with polymers well,which limits the application scope and processability of them.In order to solve these problems,CdS QDs were prepared by in-situ synthesis with polymer as template.The preparation conditions were explored,and the performances of the QDs were invesigated.Then,a kind of fluorescencent nanofiber membrane composites were prepared by electrostatic spinning.The specific research contents are as follows:First of all,the high-performance linear structure polyether ether ether ketone?PEEK?was sulfonated,we obtained sulfonated polyether ether ketone?SPEEK?.SPEEK was used as the ligand and polymer template in the in-situ synthesis programs.CdS/SPEEK QDs were prepared with cadmium acetate dihydrate as the cadmium source and thioureas as the sulfur source.The sulfonic acid groups on the SPEEK provide the acting sites for the QDs crystals,and the polymers provide the frame for the generation of QDs crystals.The effects of reaction time and the content of the reactions how to effect the fluorescence performances of quantum dots were investigated then.Since the linear SPEEK chain is rigid and unable to coat QDs well,the hyperbranched poly aromatic ether ketone?HPAEK?with carboxyl group was synthesized by using 2,4',6-difluorodiphenyl ketone and phenol naphthalene.In the process of the synthesis,the carboxyl groupson the HPAEK provide the acting sites,while the polymers provide the frame for the QDs.Due to the net structure of hyperbranched polymer,voids limit the sizes of QDs and implement the crysals dispers uniformly.Thus HPAEK plays a role in the coating and stabilization of QDs.Exploring the influence of reaction conditions,we found that the reaction time being 5min and the reactants ratio being Cd²⁺:-SO₃H:S^2-=1:5:1,the fluorescence performance of the CdS/HPEK QDs we obtained were the best.The fluorescence quantum yield was 61%.CdS QDs coated with HPAEK implement the transformation from inorganic nanocrystals to inorganic-organic nanocomposites.Linear poly aromatic ether ketone?PAEK?with carboxyl side groups was synthesized by 4,4-difluorophenone and phenol naphthalene monomers.This research explored the electrostatic spinning conditions of linear PAEK.Then the CdS quantum dots coated with HPAEK were blended into linear PAEK.Nanocomposite fiber membranes with excellent fluorescence performance were prepared by electrostatic spinning.This kind of membrane possesses the characteristics of both fluorescence and heat resistance,realizing the integration of the properties of QDs and polymers,laying a foundation for the research of new photoelectric devices.