Effect Of Transition Metal Zn²⁺,Ni²⁺,Mn²⁺ Ions On The Spectral Properties Of Upconversion Crystal

In recent years,lanthanide-doped upconverson nanocrystals?UCNs?have drawn considerable attention not only because they have large anti-Stokes shifts,high photochemical stability,sharp emission bands,long lifetime,high upconversion efficiency,and weak background luminescence,but also because they have potential applications such as solar cells,optics encoding,new-generation lighting,and biological probes compare to quantum dots,organic dyes.However,the application of these UCNs is still restricted due to their low upconversion luminescene efficiency.Therefore,various methods have been attempted to improve upconversion luminescene efficiency,such as doping with different metal ions to modify hosts,varying the crystal phase of nanocrystals to change the crystal field asymmetry,fabricating core-shell structures to decrease surface quenching,increasing sensitizer or doping with different rare-earth ions to expand the excitation spectrum or minimize nonradiative energy loss and so on.As the current popular strategy,the doping of metal ions or atoms into the host materials is an efficient way to produce UCNPs with diversified size,phase and emission.In this paper,we mainly introduce three parts work.The first part is focusing on facilitating the crystal growth of NaYF₄:Yb³⁺/Tm³⁺NCs through the introduction of Zn²⁺ions in the initial solution,and study the change of crystal growth and emission intensity.In addition,the mechanism about how the Zn²⁺ions influence the NCs growth is discussed and explained in detail combined with experimental data.The second part is focusing on the optical properties of NaYF₄:Yb³⁺/Er³⁺/Ni²⁺,the variety spectrum of NaYF₄:Yb³⁺/Er³⁺with different concentration of Ni²⁺is studied,furthermore the mechanisation is discussed based on experimental data and investigation of literature.The third part is focusing on enhancing the red emission of KMgF₃:Yb³⁺/Er³⁺through doping Mn²⁺.as we all known,the red region?600-700 nm?is generally addressed as the“optical window”of the biological tissues due to the lack of the efficient endogenous absorbers,and the KMgF₃:Yb³⁺/Er³⁺crystal can produce single red emission under 980nm laser diode,after investigation of material synthesis method and the optical properties of KMg F₃:Yb³⁺/Er³⁺,we synthesize and observe the emission intensity change of KMgF₃:Yb³⁺/Er³⁺with variety concentration of Mn²⁺,then explained this phenomenon in detail.Our results show that,the transition metal ions not only have an important effect on the growth and surface morphology of the UCNPs,but also play an important role in the spectrum and emission intensity of the UCNPs.We synthesize NaYF₄:Yb³⁺/Tm³⁺by introducing Zn²⁺in the initial solution,and found that he Zn²⁺ion can promote the growth and the phase transition of NaYF₄:Yb³⁺/Tm³⁺NCs,then enhance the crystal emission.The NaYF₄:Yb³⁺/Er³⁺emission intensity and the upconversion efficiency will increase after doping with Ni²⁺,besides the red/green ratio is variety with different concentration of Ni²⁺,so it can tune the upconversion luminescence with different concentration of Ni²⁺.Manganese(Mn²⁺)doping in host lattices of KMgF₃:Yb³⁺/Er³⁺crystal can lead to enhance upconversion luminescence due to more energy transfer way,furthermore,the KMgF₃:Yb³⁺/Er³⁺crystal have uniform size and regular shape for biological applications.