Optimized photoluminescence quantum yield in upconversion composites considering the scattering, inner-filter effects, thickness, self-absorption, and temperature

Abstract

Optimizing upconversion (UC) composites is challenging as numerous effects influence their unique emission mechanism. Low scattering mediums increase the number of dopants excited, however, high scattering mediums increase the UC efficiency due to its non-linear power dependency. Scattering also leads to greater thermal effects and emission saturation at lower excitation power density (PD). In this work, a photoluminescence quantum yield (PLQY) increase of 270% was observed when hexagonal NaYF4:(18%)Yb3+,(2%)Er3+ phosphor is in air compared to a refractive index-matched medium. Furthermore, the primary inner-filter effect causes a 94% PLQY decrease when the excitation focal point is moved from the front of the phosphor to 8.4 mm deep. Increasing this effect limits the maximum excitation PD, reduces thermal effects, and leads to emission saturation at higher excitation PDs. Additionally, self-absorption decreases the PLQY as the phosphor’s thickness increases from 1 to 9 mm. Finally, in comparison to a cuboid cuvette, a 27% PLQY increase occurs when characterizing the phosphor in a cylindrical cuvette due to a lensing effect of the curved glass, as supported by simulations. Overall, addressing the effects presented in this work is necessary to both maximize UC composite performance as well as report their PLQY more reliably.

Photodynamic Therapy and Multi-Modality Imaging of Up-Conversion Nanomaterial Doped with AuNPs

“…Others have offered sliver doping [7], which has a large impact as well; however, sliver is poisonous to cells, may cause cell death without targeting, and cannot be employed in biology. Many scholars have proposed constructing core-shell structures such as NaYF 4 :Yb 3+ /Er 3+ @NaGdF 4 :Yb 3+ and NaYF 4 :Yb 3+ /Er 3+ @NaNdF 4 :Yb 3+ /Tm 3+ @NaGdF 4 :Yb 3+ [8][9][10]. Alternatively, use the reverse microemulsion method to construct a layer of silica or porous silica, such as NaYF 4 :Yb 3+ /Er 3+ @SiO 2 , or NaYF 4 :Yb 3+ /Er 3+ @NaGdF 4 :Yb 3+ @m-SiO 2 [11][12][13][14].…”

Synthesis of Rare-Earth Nanomaterials Ag-Doped NaYF4:Yb3+/Er3+@NaYF4:Nd3+@NaGdF4 for In Vivo Imaging

“…Others have proposed doping with silver, which also has a significant effect, but silver has a high light-to-heat conversion efficiency, can cause cell apoptosis without targeting, and cannot be used in biology [ 7 , 8 ]. Other scholars have proposed constructing core-shell structures such as NaYF 4 :Yb 3+ /Er 3+ @NaGdF 4 :Yb 3+ , NaYF 4 :Yb 3+ /Er 3+ @NaNdF 4 :Yb 3+ /Tm 3+ @NaGdF 4 :Yb 3+ [ 9 , 10 , 11 ]. Alternatively, the reverse microemulsion method can be used to construct a layer of silica or porous silica, such as NaYF 4 :Yb 3+ /Er 3+ @SiO 2 , NaYF 4 :Yb 3+ /Er 3+ @NaGdF 4 :Yb 3+ @m-SiO 2 [ 12 , 13 , 14 ].…”

SiO2 Coated Up-Conversion Nanomaterial Doped with Ag Nanoparticles for Micro-CT Imaging

“…Other studies proposed doping with Ag, which has a significant effect but Ag has a high light-to-heat conversion efficiency and can cause cell apoptosis without targeting; therefore, Ag cannot be used in biological studies [7,8]. Many researchers proposed developing core-shell structures such as NaYF 4 : Yb 3+ /Er 3+ @NaGdF 4 : Yb 3+ and NaYF 4 : Yb 3+ /Er 3+ @NaNdF 4 : Yb 3+ /Tm 3+ @NaGdF 4 : Yb 3+ [9][10][11]. Alternatively, the material surface is covered with a biocompatible coating such as DSPE-PEG 2K and ICG [12][13][14].…”