The Hydrothermal Synthesis And Deep-ultraviolet Lasing Properties Of ErF₃ Upconversion Nanocrystals

Lanthanide ions are endowed with unique upconversion optical properties which generated great interest in many aspect,for example,deep-ultraviolet micro lasers are one of the potential applications.However,the low upconversion efficiency and concentrations quenching of the lanthanide NCs is still the most serious limitation for their optical application.Recently,a great deal of reaserch efforts has been devoted to enhance the upconversion efficiency of lanthanide doped upconverting nanocrystals?UCNCs?.A brightful luminescence was observed in highly Er³⁺-doped UCNCs,therefore,investing the upconversion emission properties of Er³⁺ have a significent value to enhance the brightness and emission efficiency of UCNCs.In this paper,based on the excellent upconversion luminescence peoperties of Er³⁺ ions,we designed and synthesisd ErF₃ nanocrystals as a new class of lanthanide-doped upconversion nanocrystals which take Er³⁺ as self-sensitizers in the host lattice.Then we prepared ErF₃:1%Tm³⁺ nanocrystals,constructed the Er³⁺-Tm³⁺ pairs to improve the upconversion efficiency and achieve high-order deep ultraviolet upconverison emission.This study may open up new avenues on the development of upconversion nanoctystals suitable for particular optical or biomedical application.In this paper,size and morphology controlled ErF₃ nanocrystals were synthesized via the hydrothermal method.Polydentate ligand?sodium citrate?were used in the synthesis of ErF₃ nanocrystals as a means of controlling the size and morphology of the nanocrystals.Subsequently,the particle size?morphology and phase were found to be governed by the reactant concentration,molar ratio and reaction time.And we confirmed the best synthesis conditon to prepare the high quality rhombic ErF₃ nanocrystals with a uniform size distribution,highly crystallined,smooth surface and regular shape.The photoluminescence properties and absorption cross-section of orthorhombic phase ErF₃ were investigated systemically,and the ultraviolet upconversion mechanism is discussed based on complex energy transfer proc ess.The ultraviolet upconversion emission centered at 383 nm was observed under the 980 nm excitation,the peak can be attributed to ⁴G_11/2?⁴I_15/2 transition of Er³⁺.We also observed the ultravilot upconversion random laser of ErF₃ under the 975 nm excitation.We prepared ErF₃:1%Tm³⁺ nanocrystals based the best synthesis experimental conditon.The multi-photo ultraviolet upconversion emission properties was investigated in ErF₃:1%Tm³⁺ phosphor.The deep-ultraviolet emission centered at 291 nm was observed under the 980 nm excitation which is attributed to ¹I₆?³H₆ transition of Tm³⁺.These results indicate that ErF₃ has high energy transfer efficiency and can be used as an upconversion luminescent matrix material.This study may open up new avenues of research on the development of upconversion nanocrystals suitable for particular deep-ultraviolet micro-lasers or biomedical applications.