Temperature-Independent Lifetime and Thermometer Operated in a Biological Window of Upconverting NaErF4 Nanocrystals

Abstract

Lifetime of lanthanide luminescence basically decreases with increasing the ambient temperature. In this work, we developed NaErF4 core–shell nanocrystals with compensation of the lifetime variation with temperature. Upconversion lifetime of various emissions remains substantially unchanged as increasing the ambient temperature, upon 980/1530 nm excitation. The concentrated dopants, leading to extremely strong interactions between them, are responsible for the unique temperature-independent lifetime. Besides, upconversion mechanisms of NaErF4 core-only and core–shell nanocrystals under 980 and 1530 nm excitations were comparatively investigated. On the basis of luminescent ratiometric method, we demonstrated the optical thermometry using non-thermally coupled 4F9/2 and 4I9/2 emissions upon 1530 nm excitation, favoring the temperature monitoring in vivo due to both excitation and emissions fall in the biological window. The formed NaErF4 core–shell nanocrystals with ultra-small particle size, highly efficient upconversion luminescence, unique temperature-independent lifetimes, and thermometry operated in a biological window, are versatile in applications such as anti-counterfeiting, time-domain manipulation, and biological thermal probes.

Cryogenic Dependent Energy Manipulation in Nonthermally Coupled Levels for Multicolor Upconversion Luminescence

“…The optical thermometers based on the FIR of thermally coupled energy levels exhibits a number of advantages such as minimum interference of measuring conditions, rapid response, high spatial resolution, and high sensitivity. 34 The energy difference between the thermally coupled energy levels ( 2 H 11/2 and 4 S 3/2 levels) of Er 3+ ions is around 800 cm −1 , which perfectly matches the conditioins desirable for the application of the FIR method. According to the Boltzmann-type distribution theory, the FIR of the thermally coupled states can be mathematically expressed as 35−38…”

“…The variation in FIR with temperature favors the application of NaYF 4 /Er material in digital thermal sensing. The optical thermometers based on the FIR of thermally coupled energy levels exhibits a number of advantages such as minimum interference of measuring conditions, rapid response, high spatial resolution, and high sensitivity . The energy difference between the thermally coupled energy levels ( 2 H 11/2 and 4 S 3/2 levels) of Er 3+ ions is around 800 cm –1 , which perfectly matches the conditioins desirable for the application of the FIR method.…”

Carbon Dots‐in‐EuAPO‐5 Zeolite: Triple‐Emission for Multilevel Luminescence Anti‐Counterfeiting

“…With temperature increasing, both the afterglow decay rates of CDs and Eu 3+ become faster, which derive from the strong nonradiative decay processes of CDs and Eu 3+ under high temperature. [40] It has been known that CDs can be generated by the dehydration and carbonization of organic precursors during the crystallization of zeolite framework, and they are embedded in zeolite host matrix as guest. [22][23][24] The strong host-guest interactions between CDs and zeolite can well stabilize the triplet states of CDs, thus realizing the emission of long-lifetime RTP.…”

Luminescent Lifetime Regulation of Lanthanide-Doped Nanoparticles for Biosensing

“…As a consequence, elevated temperature induces the lattice to expand, leading to a longer transfer distance, and ultimately prolonging the lifetime of Er 3+ . However, the prolonged lifetime caused by lattice expansion compensated for the difference value of the shorter lifetime aroused by thermal quenching, resulting in the temperature-independent lifetime ( Figure 6 d) [ 67 ].…”

“…( d ) Negative correlation curves of the lifetime of Er 3+ at 4 S 3/2 versus ambient temperature for NaErF 4 @NaGdF 4 and NaErF 4 : 18%Yb,2%Er@NaGdF 4 nanoparticles. Reproduced with permission from [ 67 ]. Copyright 2020, MDPI.…”