In vitro temperature sensing with up-conversion NaYF4:Yb3+/Tm3+-based nanocomposites: Peculiarities and pitfalls

Study of stability of luminescence intensity of b-NaGdF4:Yb:Er nanoparticle colloids in aqueous solution

“…Up-conversion luminescence is convenient for bioimaging, since it allows the excitation of the phosphor in the near-infrared region of the spectrum and the registration of the luminescence response in the visible range of the spectrum [13,14]. Various techniques have been developed which allow in vivo determination of temperature [15][16][17][18], pH, and a viscosity [19] inside cells based on up-conversion nanoparticles. The highest quantum yields of up-conversion luminescence (PLQY) were recorded for β-NaYF 4 :21.4%Yb 3+ , 2.2%Er 3+ (PLQY=10.5% at 35 W/cm 2 ) [20], BaY 2 ZnO 5 :7%Yb 3+ , 3%Er 3+ (PLQY=5% at 2.2 W/cm 2 ) [21], La 2 O 2 S:9%Yb 3+ , 1%Er 3+ (PLQY=5,8% at 13 W/cm 2 ) [22], SrF 2 :3%Yb, 2%Er (PLQY=6.5% at 230 W/cm 2 ) [11].…”

Up-Conversion Luminescence Processes in NaLaF4 Doped with Tm3+ and Yb3+ and Dependence on Tm3+ Concentration and Temperature

“…Temperature effects on up-conversion luminescence have been observed in various materials (e.g., polycrystalline powder, glass ceramics, nanoparticles) doped with thulium ions. [18][19][20][21][22] Up-conversion luminescence spectra measurements at higher temperatures were performed to verify whether sample temperature variation could significantly affect the intensity of up-conversion luminescence bands. For this experiment, the heater head was slightly covered with NaLaF 4 :Tm 3þ ,Yb 3þ , almost invisible to the naked eye, but under 976 nm excitation the blue Tm 3þ up-conversion luminescence could be observed with the naked eye.…”

Impact of sensitizer Yb and activator Tm on luminescence intensity of beta-NaYF4:Yb/Tm nanoluminophores

“…In such nanoparticles, it is possible to implement up-conversion luminescence in which two or more photons with low energy turn into one photon with higher energy [1][2][3]. Such phosphors are used for optical imaging in biology and medicine [4][5][6], as optical coding elements [7], photovoltaic devices and anticounterfeiting [8], thermometry [9][10][11][12], and increasing the efficiency of solar panels [13][14][15].…”

“…Currently, the most effective up-conversion nanoluminophores have been developed on the basis of substances with gagarinite type crystal structure -NaYF 4 [9,16,17] or NaGdF 4 [5,12,18], which are doped with two types of ions. One (sensitizer ion) has a large absorption cross-section, and the other (activator ion) has high luminescence efficiency.…”

“…The sensitizer ion absorbs the excitation energy and non-radiatively transfers it to the activator ion, which then emits up-conversion luminescence. Ytterbium ions often act as sensitizer while erbium, thulium, and holmium ions are used as activators [5,8,9,12,[16][17][18].…”