Study On Magnetic Tuning And Plasma Enhancement Effect Of Upconversion Luminescence

Rare earth doped upconversion nanomaterials?UCNPs?have attracted much attention as a new type of luminescent materials.Because of the advantages of unique luminescence characteristics,good optical stability,strong penetrability and low toxicity,they have a very good applied prospects in the fields of nano-organisms,advanced functional materials and lighting and so on.The material of rare earth is the ideal materials to achieve the bi-function of optical and magnetic because the elements are rich in optical and magnetic properties,which is expected to be used in the field of optical and magnetic dual-mode imaging,becoming the current international research hot spots.In this paper,the regulation of the physicochemical properties of nanocrystals with high efficiency is described,and the luminescence characteristics of the upconversion nanocrystals in the case of strong magnetic field and ultra-low temperature are discussed.?1?An excellent upconversion nanocrystals was produced.Spherical NaGdF₄:18%Yb³⁺/2%Er³⁺ upconversion nanocrystals with uniform monodisperse and uniform size?about 18 ± 2 nm in diameter?were prepared by solvothermal method.?2?The luminescence intensity was improved by surface modification of nanocrystals.The NaYF₄ shell were coated on the surface of NaGdF₄: 18%Yb³⁺/2%Er³⁺ nanocrystals by solvothermal method.The luminescence intensity of NaGdF₄ was improved much higher than that of surface-modified nanocrystals.The main reason was that the coated shell isolates the effect of the surface defects of the nanocrystals nanocrystals on the luminescent center,thus improving the upconversion efficiency.?3?The luminous intensity was enhanced by adding gold nanorods.By simply mixing with NaGdF₄:18%Yb³⁺/2%Er³⁺ upconversion nanocrystals,it was found that the upconversion luminescence can be effectively improved.That the local surface plasmas produced on the surface of gold nanoparticles had intensive effect on the luminescence of nanocrystals was the main reason.?4?The compensation of the upconversion luminescence by the strong magnetic field and the ultra-low temperature plasma has been found.Mixing NaGd F₄:18%Yb³⁺/2%Er³⁺ composite nanocrystals with ordinary NaGdF₄:18%Yb³⁺/2%Er³⁺ nanocrystals were used for fluorescence analysis under strong magnetic field,that the luminous intensity of ordinary nanocrystals is inhibited by the magnetic field has been found.While the intensity of the luminescence intensity NaGdF₄:18% Yb³⁺/2% Er³⁺ composite nanocrystals had no change when the magnetic field intensity is 0 to 6T.And the suppression of all magnetic fields is higher than that of ordinary nanocrystals suppressed much smaller in the whole process.In addition,the red and green ratio?IIRRG?of ordinary nanocrystals and composite nanocrystals increased with the increase of magnetic field.The reason perhaps was that the magnetic field was stronger than the red light.