Intrinsic Time‐Tunable Emissions in Core–Shell Upconverting Nanoparticle Systems

Abstract

Color‐tunable luminescence has been extensively investigated in upconverting nanoparticles for diverse applications, each exploiting emissions in different spectral regions. Manipulation of the emission wavelength is accomplished by varying the composition of the luminescent material or the characteristics of the excitation source. Herein, we propose core–shell β‐NaGdF4: Tm3+, Yb3+/β‐NaGdF4: Tb3+ nanoparticles as intrinsic time‐tunable luminescent materials. The time dependency of the emission wavelength only depends on the different decay time of the two emitters, without additional variation of the dopant concentration or pumping source. The time‐tunable emission was recorded with a commercially available camera. The dynamics of the emissions is thoroughly investigated, and we established that the energy transfer from the 1D2 excited state of Tm3+ ions to the higher energy excited states of Tb3+ ions to be the principal mechanism to the population of the 5D4 level for the Tb3+ ions.

Exploring near-infrared absorbing nanocarriers to overcome cancer drug resistance

“…Lanthanide-doped upconverting nanoparticles (UCNPs) absorb NIR light, which is converted via an anti-Stokes shift to light with higher energy. The light produced can be in the UV, visible, or NIR range of the spectrum [165,186] . UCNPs are especially interesting for biomedical research because their emission wavelength is tunable [187] .…”

Modulating Photo- and Radioluminescence in Tb(III) Cluster-Based Metal–Organic Frameworks

“…The decay time of the 5 D4 → 7 F5 transition (545 nm) of Tb-UiO-66 upon 355 nm excitation is 1048.6 ± 6.93 μs (Figure S13), which is typical for Tb(III) 4f-4f transitions. [36][37][38] The radioluminescence emission spectrum of Tb-UiO-66 under 50 kVp, 80 μA unfiltered X-ray excitation (Au target) also exhibits characteristic Tb(III) emissions and no linker emission. Of all three MOFs, the radioluminescence intensity of Tb-UiO-66 is the most intense (Figure 3d, Figure S14), indicative of high X-ray attenuation by the hexanuclear Tb(III)-clusters coupled with the highly efficient sensitization of Tb(III) from the triplet state of BDC 2-.…”

“…Interestingly, the lifetime of the 5 D4 → 7 F5 transition of Tb(III) upon 355 nm excitation was found to be 53.1 ± 0.08 μs (Figure S13), which is relatively short for this transition. [36][37][38] Since the emission of TCPB 4 ⁻ overlaps with the 5 D4 → 7 F5 transition at 545 nm, and has a short decay time (on the order of ps-ns), the lifetime of the 5 D4 → 7 F3 transition of Tb(III) at 621 nm was also measured. The decay time of this transition was found to be 51.6 ± 1.13 μs, which is similar to the 5 D4 → 7 F5 transition, and is still unexpectedly short for a Tb(III) decay time (Figure S13).…”