Giant sensitivity of an optical nanothermometer based on parametric and non-parametric emissions from Tm3+ doped NaNbO3 nanocrystals

Noncentrosymmetric Lanthanide-Based MOF Materials Exhibiting Strong SHG Activity and NIR Luminescence of Er3+: Application in Nonlinear Optical Thermometry

“…It is clearly seen that the SHG signal decreases with temperature, whereas the emission band of Er 3+ broadens; hence, its integrated intensity slightly increases with temperature elevation. The observed thermal broadening effects of Er 3+ NIR emission are associated with enhanced electron–phonon coupling at elevated temperature (vibrational contribution) and slight deviations from the initial geometry of the Ln 3+ site in the crystals due to the lattice thermal expansion effects (static contribution), whereas the decrease of the SHG signal intensity with temperature is plausibly associated with increasing strains and distortions in the crystals, as well as enhanced absorption of Er 3+ ions at elevated temperature, leading to the greater reabsorption of the SHG light . DTA analysis excluded the possibility of structural interconversions in the studied T -range related to the loss of solvent molecules and eventual structural collapse of the MOF framework (Figure S2).…”

“…The observed thermal broadening effects of Er 3+ NIR emission are associated with enhanced electron–phonon coupling at elevated temperature (vibrational contribution) and slight deviations from the initial geometry of the Ln 3+ site in the crystals due to the lattice thermal expansion effects (static contribution), whereas the decrease of the SHG signal intensity with temperature is plausibly associated with increasing strains and distortions in the crystals, as well as enhanced absorption of Er 3+ ions at elevated temperature, leading to the greater reabsorption of the SHG light. 55 DTA analysis excluded the possibility of structural interconversions in the studied T -range related to the loss of solvent molecules and eventual structural collapse of the MOF framework ( Figure S2 ). Thanks to the opposite behaviors of Er 3+ NIR luminescence and SHG with temperature, we could calculate the corresponding band intensity ratios ( I Er / I SHG ) as a function of temperature, using the integrated intensities of both bands, and plot the resulting I Er / I SHG values in Figure 5 b.…”

“… 54 Recently, there appeared first reports dealing with lanthanide-doped (Tm 3+ , Ho 3+ , or Er 3+ ) BaTiO 3 and NaNbO 3 polycrystalline, inorganic materials, exhibiting SHG and upconversion luminescence properties, showing the possibility of their application in nonlinear optical thermometry. 28 , 31 , 55 Rational design strategies for readily available NLO-active Ln-MOFs, especially those that are active in the NIR region, are, however, yet to be established, with the main bottleneck being the complex structure of used ligands and consequently the generation of high costs that hinder the practical applications. 1 , 11 , 17 , 56 − 58 …”

“…Moreover, some of the lanthanide ions embedded in the structure of the organic and/or inorganic (nano)­materials may exhibit desired magnetic properties, − selective catalytic activity, , energy upconversion capability, − as well as great pressure and/or temperature sensing performance. ,− In fact, lanthanides are the main activator ions for most of the modern optical (contactless) thermometers, utilizing the effect of temperature-dependent luminescence for temperature monitoring (readouts) in a system of interest, including, e.g., optoelectronic devices, biological structures, as well as nanosized molecular magnets. ,− ,, Initially, only the lanthanide ions having thermally coupled levelsTCLs ( i.e ., two excited states separated by 200–2000 cm –1 ), such as Nd 3+ , Er 3+ , and Tm 3+ ions, were used for luminescence thermometry, later called Boltzmann-type thermometers. ,,,, However, in the last years, there has been an increasing amount of reports dealing with non-TCLs of lanthanides and the use of the corresponding, temperature-dependent band intensity ratios, emission line shifts, and even luminescence lifetimes as thermometric parameters (non-Boltzmann thermometers). ,,− One of the first papers about nonlinear temperature sensing was reported in 2010 by the group of J. García Solé, concerning the 2-photon fluorescence of CdSe quantum dots . Recently, there appeared first reports dealing with lanthanide-doped (Tm 3+ , Ho 3+ , or Er 3+ ) BaTiO 3 and NaNbO 3 polycrystalline, inorganic materials, exhibiting SHG and upconversion luminescence properties, showing the possibility of their application in nonlinear optical thermometry. ,, Rational design strategies for readily available NLO-active Ln-MOFs, especially those that are active in the NIR region, are, however, yet to be established, with the main bottleneck being the complex structure of used ligands and consequently the generation of high costs that hinder the practical applications. ,,,− …”

Controlling upconversion in emerging multilayer core–shell nanostructures: from fundamentals to frontier applications

“…216 Many efforts have been made to improve the thermal sensitivity via tuning of dopant composition and host materials. 223,224 Recently, the interface lattice self-adaptation was developed to remarkably enhance the thermal sensitivity of luminescent nanothermometers by fabricating an ingenious MLCS nanostructure. 225 For instance, the design of NaGdF 4 /NaYF 4 heterojunction can produce a lattice distortion at the core/shell interface, which was sensitive to temperature (Fig.…”