Structural Evolution Of Rare Earth Doped NaLnF₄ Miro/nanocrystal And Application Of Immunoassay For Cardiovascular Diseases

Rare earth?RE?-based fluoride microcrystals?MCs?and nanocrystals?NCs?are a class of rapidly growing materials because of their outstanding luminescent and magnetic properties.The enthusiasm for research on high up-conversion luminescent?-NaLnF₄ micro-crystals is driven by both fundamental interest and micron size photonic device integration.Among all the RE-based fluoride MCs,?-NaLnF₄with a space group of P6₃/m have potentially higher up-conversion?UC?luminescence efficiency over a wide wavelength range adequate thermal and chemical stabilities,where NaYbF₄ as well as NaGdF₄ have attracted most research interests.However,there are still significant hurdles in the control of size,morphology and phase of?-NaLnF₄ MCs due to limited understanding of their solution growth mechanism.And there are few studies on the application of UC nanoparticles as independent reporters in the detection of myocardial infarction on the strip.Herein,we report the preparation of hexagonal NaLnF₄ MCs with various morphologies?rod-,disk-and flake-like?and crystal sizes?100 nm to 10?m?via a hydrothermal route.The morphologies and sizes of NaLnF₄ MCs were revealed to be highly dependent on the ionic radius of different Ln³⁺ions.We have proposed a ligand-adsorption-driven oriented growth model and a surface energy dominant nucleation model to interpret the above phenomena.In addition,we also synthesized NaYF₄:Yb³⁺/Er³⁺@NaYF₄ core-shell nanoparticles and successfully applied into the lateral flow strips to detect the heart diseases.These results provide a thermodynamic understanding for researchers to develop NaLnF₄ MCs with targeted morphology and size and it widens the application scope of Ln³⁺doped up-conversion NaYF₄nanoparticles in lateral flow strip.Specifically,this paper mainly carried out the following research:It reveals the phase and morphology evolution mechanism of luminescent NaLnF₄?Ln=La to Yb?microcrystals?MCs?,which is indeed an ionic radii and surface energy dependent solution growth mechanism.The morphologies of NaLnF₄ MCs change from rod to disk-shape with increasing ionic radius of Ln³⁺.This can be attributed to the less adsorption of citrate ions(Cit^3-)ions on the?100?crystal planes that induced a weaker preferential growth orientation along[100]directions.In addition,the first principle calculations were performed,confirming that with increasing ions radius of Ln³⁺,the required surface energy for NaLnF₄ nucleation is decreased.It expedites nucleation rate and leads to smaller crystal size.An efficient Goldschmidt's law associated to phase change of NaLnF₄/LnF₃ phase change has also established.These important findings can provide new sights for researchers to obtain rare earth doped hexagonal NaLnF₄ with high upconversion photoluminescence efficiency.?1?Further,we prepared NaYF₄:18%Yb³⁺/2%Er³⁺@NaYF₄ and NaYF₄:60%Yb³⁺/8%Er³⁺@NaYF₄ core-shell structured nanoparticles?UCNPs?by coprecipitation method.In order to better couple the nanoparticles with antibody protein,the fluorescent nanoparticles were coated with layer of SiO₂.Then,UCNPs@SiO₂ was modified and activated as fluorescence labeled conjugate and the capture antibody solidified in the detection band.The double antibody sandwich method was used to detect the markers of myocardial infarction?serum amyloid A,SSA?.The reaction process was completed within 15 minutes,which provided important research value for the real-time detection and diagnosis of myocardial infarction.