Study On Phosphine-free Synthesis Of Metal Telluride Nanocrystals And High-pressure Fluorescence Properties

With the rapid development of nanomaterials technology,semiconductor metal telluride nanocrystals（NCs）have become a hot spot of nanomaterial in the past decade,not only for their excellent photoelectric properties and thermoelectric properties but also for their wide application prospects.As one of the metal telluride nanocrystals,cadmium telluride nanocrystals have the advantages of narrow and tunable emission spectra,high fluorescence efficiency and good physicochemical stability.It has great application value in solar cells,light-emitting diodes,biological probes and other fields.A colloidal strategy offers opportunities for the rational design and synthesis of metal telluride nanocrystals（NCs）with the desired crystal structure,uniform geometry,and composition.However,the synthesis of metal telluride nanocrystals involving cadmium telluride is still faced with the serious problems such as complicated,toxicity,expensive and environmentally unfriendly.Here,we developed a new strategy for fabricating highly reactive phosphine-free Te precursor at room temperature,and then prepare high quality cadmium telluride and other metal telluride nanoparticles,which provides a new way for the green preparation of semiconductor metal telluride.The specific related research works are summarized as follows.Design of size controllable preparation of binary metal tellurides NCs.Herein,we report an efficient synthesis method of phosphine-free Te precursor at room temperature,where the TeO₂ powder is first reduced by DDT in the presence of OLA to generate a soluble alkylammonium telluride.Based on the in-situ UV-vis absorption spectroscopy results,we provide direct experimental evidence that the OLA–Te complexes were formed in a second-magnitude kinetic process.Subsequently,we have fabricated high-quality and monodisperse cadmium telluride nanocrystals by using highly reactive phosphine-free Te precursor.With the reaction time of 30s,the CdTe NCs are synthesized with a size of 2.2±0.3 nm,based on the analysis of 100 nanoparticles.On increasing the reaction time,the diameters of the as-synthesized CdTe NCs increase.The OLA-Te solution is stable enough as the precursor for hot-injection synthesis of telluride NCs,such as PbTe,FeTe₂ and Cu₂Te NCs.The present results inspect the applicability of our phosphine-free Te precursor and provide a new idea for the green synthesis route of metal telluride nanocrystals.2.Study on the fluorescence characteristics of cadmium telluride nanocrystals.To further assess the quality of the as-prepared Te precursor,we investigated the fluorescence properties of the synthesized CdTe NCs.The change of UV-vis absorption peaks at 300 nm attributed to the critical nuclei indicates the evolution of CdTe particle size and distribution with the reaction time.Such a spectroscopic observation clearly suggests a dynamic formation process involving（1）nucleation,（2）growth stages.In situ fluorescence spectroscopy experimental results show that,with the increase of reaction time,the CdTe NCs has full-color emission and the fluorescence peak is red shifted.Because of the narrow emission spectra and high brightness,the as-synthesized CdTe NCs are further utilized as color conversion layer materials to fabricate LEDs.Under high pressure,the fluorescence intensity of CdTe NCs is weakened with a blue shift of the peak position.This experimental study provides a scientific experimental basis for the application of CdTe nanocrystals,such as fluorescence labeling,fluorescence probe and screen display,etc.