Multifunctional cellulose fibers: Intense red upconversion under 1532 nm excitation and temperature-sensing properties

The use of energy looping between Tm3+ and Er3+ ions to obtain an intense upconversion under the 1208 nm radiation and its use in temperature sensing

“…Tm 3+ to Er 3+ ET is a subject of many reports and explains the shift from green to red upconversion in materials co-doped with Tm 3+ . 54–57 Here, we postulate that the ET3 from the 4 I 11/2 excited state of Er 3+ ions is more probable than from the 4 I 9/2 state. Red luminescence does not result from multiphonon relaxation from the 4 S 3/2 excited state.…”

Anti-counterfeiting system based on luminescent varnish enriched by NIR- excited nanoparticles for paper security

“…On the contrary, the lowest calculated values of the lifetimes measured under 980 nm laser excitation were for the 4 F 9/2 → 4 I 15/2 . The reason is that Tm 3+ ions play the role of trapping centers and mediate the UC mechanism 41 . Generally, all the luminescence lifetimes were longer for the NaErF 4 :Tm 3+ @NaYF 4 _II structure.…”

Achieving ultrasensitive temperature sensing through non-thermally coupled energy levels to overcome energy gap constraints

“…A new and fast-emerging thermometry technology based on optical information meets all of the above requirements and has attracted much research attention in recent years. [1][2][3] Actually, there exists a series of temperature-dependent optical parameters that can be employed for the purpose of temperature detection, among which the fluorescence intensity ratio (FIR) between two thermally coupled energy levels (TCLs) of lanthanide ions shows tremendous potential to accurately extract the temperature information due to its independence of background noise, excitation source and other factors. 4,5 For instance, our group has reported the temperature sensing performance of BaY 2 O 4 :Yb 3+ /Er 3+ based on the thermally coupled Stark sublevels of the Er 3+ : 4 F 9/2 state, revealing high thermometric sensitivity with the penetration depth in the biological tissues of approximately 6 mm.…”