Precision design of highly sensitive luminescent thermometers via crystal field splitting engineering.

Rare earth-doped up-conversion luminescent materials have attracted considerable attention in the field of optical temperature sensing due to their superior spatial resolution and fast response. However, their practical application has been fundamentally hindered by their low relative sensitivity (S), which inherently restricts the accuracy of temperature measurement, and conventional optimization strategies, which predominantly rely on empirical trial-and-error approaches, and lack systematic theoretical guidance for rational material design. To address these critical challenges, we propose a novel thermometric paradigm based on the energy splitting factor (K) to theoretically determine the energy gap (ΔE) between thermally coupled excited states.

Engineering Trap Distribution by Doping Rare Earth Ion for Mechanoluminescence Enhancement.

Mechanoluminescence materials exhibit fascinating optical properties due to their energy harvesting and controllable release capabilities. SrAlO:Eu (SAOE) has been extensively studied as a traditional mechanoluminescence material, however, the luminescence intensity enhancement and the luminescence mechanism of its mechanoluminescence remain an unresolved issue, which hinders the development and widespread application of excellent phosphors. Herein, a promising rare earth (Re = Sm, Dy, Er, and Tm) doping strategy was proposed to achieve intense mechanoluminescence of SAOE.

Li-Based Nanoprobes with Boosted Photoluminescence for Temperature Visualization in NIR Imaging-Guided Drug Release.

Lanthanide-doped fluoride nanocrystals have emerged as promising tools in biomedicine, yet their applications are still limited by their low luminescence efficiency. Herein, we developed highly efficient lithium-based core-shell-shell (CSS) nanoprobes (NPs) featuring a rhombic active domain and a spherical inert protective shell. By introducing Yb as an energy transfer bridge and optimizing the CSS design, a remarkable 1643-fold enhancement in visible emission and a 33-fold increase in NIR emission are achieved compared to original nanoparticles.

Engineering dual-mode near-infrared ratiometric thermometers based on rare earth-doped molybdates.

Near-infrared optical thermometers have sparked great interest for their ability to provide non-destructive testing and high-resolution. However, the restricted relative sensitivity and single temperature measurement mode represent the current limitations of luminescent thermometers. Herein, near-infrared dual-mode ratiometric thermometers with high sensitivity in La(MoO): Yb, Ln (LMO: YbLn, Ln = Er, Ho, Nd) phosphors were designed.

Achieving Near-Infrared Highly Sensitive Temperature Sensing in Lanthanide-Doped Lead-Free Double Perovskite NaLaMgWO with Significant Thermal Enhancement.

The significant temperature response of lanthanide-doped up-conversion luminescent materials is typically characterized by a severe thermal quenching of the luminescence intensity at elevated ambient temperatures, which severely restricts materials' capability in temperature sensing. Herein, the influence of matrix phonon properties on the remarkable thermal enhancement effect in the thermosensitive material NaLaMgWO:Yb/Nd is reported. It is elucidated that achieving a significant thermal enhancement of Nd with a higher phonon energy oxide matrix is easier than a halide matrix, which has lower phonon energy by comparison with previous findings.

Toward Ultra-High Sensitivity Optical Thermometers and Bright Yellow LEDs Based on Phonon-Assisted Energy Transfer in Rare Earth-Doped LaZnTiO Double Perovskite.

Double perovskites, a class of ceramic oxides with unique crystal structures and diverse physical properties, show promise for various technological applications including solar cells, photodetectors, and light-emitting diodes (LEDs). Despite limited research on rare earth-doped double perovskites, leveraging their ultrahigh luminous efficiency to achieve bright yellow LED emission and addressing energy transfer challenges between Yb and Nd ions in double perovskite LaZnTiO with moderate phonon energy are explored in this work. Through phonon-assisted energy transfer, an ultrasensitive optical thermometer covering a wide temperature range is developed by utilizing the different temperature responses of Er emission in the visible light region and Nd emission in the near-infrared region based on the luminescence intensity ratio (LIR).

Engineering Visible to Near-Infrared Luminescence through a Selective Doping Strategy for High-Performance Temperature Sensing.

Luminescence nanothermometers have garnered considerable attention due to their noncontact measurement, high spatial resolution, and rapid response. However, many nanothermometers employing single-mode measurement encounter challenges regarding their relative sensitivity. Herein, a unique class of tunable upconversion (UC) and downshifting (DS) luminescence covering the visible to near-infrared range (400-1700 nm) is reported, characterized by the superior Tm, Ho, and Er emissions induced by efficient energy transfer.

The Art of Nanoparticle Design: Unconventional Morphologies for Advancing Luminescent Technologies.

The advanced design of rare-earth-doped (RE-doped) fluoride nanoparticles has expanded their applications ranging from anticounterfeiting luminescence and contactless temperature measurement to photodynamic therapy. Several recent studies have focused on developing rare morphologies of RE-doped nanoparticles. Distinct physical morphologies of RE-doped fluoride materials set them apart from contemporary nanoparticles.

Optimization of deliquescence-proof perovskite-like CsErF phosphor and dual-mode luminescent intensity ratio thermometry.

The susceptibility of Cs-based fluorides to deliquescence has led to the fact that lanthanide-doped Cs-based fluorides and their related applications have hardly been reported. Herein, the method to solve the deliquescence of CsErF and its excellent temperature measurement performance were discussed in this work. Initially, the soaking experiment of CsErF found that water had irreversible damage to the crystallinity of CsErF.

Enhancing the Upconversion Luminescence and Sensitivity of Nanothermometry through Advanced Design of Dumbbell-Shaped Structured Nanoparticles.

The core-shell engineering of lanthanide-doped nanoparticles has captured considerable attention because it can safeguard the luminescence intensity of the core by reducing surface defects. However, the limited surface area of the traditional spherical core-shell structure hinders the further breakthrough of the brightness. Herein, a unique NaYF:Yb/RE@NaYF:Yb/RE@NaNdF:Yb (RE = Ho or Er) dumbbell-shaped multilayer nanoparticle featuring a high surface area is reported.

The Charge Transfer Band as a Key to Study the Site Selection Preference of Eu in Inorganic Crystals.

On account of the strong oxidizing property of the europium(III) ion, its charge transfer band (CTB) can be easily formed in many inorganic compounds. In this work, the Eu ions were singly doped into the KLuSiO compound with a hexagonal structure, and two kinds of Eu-O CTBs were detected by monitoring at specific wavelengths. The qualitative analysis of Eu ion site occupation was illuminated by combining Eu-O CTBs with the corresponding cell volume.

A novel differential display material: KLuSiO: Tb/Bi phosphor with thermal response, time resolution and luminescence color for optical anti-counterfeiting.

Optical anti-counterfeiting and encryption have become a hotspot in information security. However, the advanced optical anti-counterfeiting technology still suffers from low security by single-luminescent mode. Herein, we present a novel multi-mode anti-counterfeiting strategy based on KLuSiO: Tb/Bi (KLSO: Tb/Bi) phosphors for the first time.

Trimodal Ratiometric Luminescent Thermometer Covering Three Near-Infrared Transparency Windows.

Near-infrared (NIR) transparency windows have evoked considerable interest in biomedical thermal imaging owing to the superior tissue penetration and the high signal-to-noise ratio, allowing real-time temperature reading with nanometric spatial resolution. Here, we develop a multimode nonintrusive luminescent thermometer based on the YAlO (YAG):Cr/Ln (Ln = Ho, Er, Yb) phosphor, which covers three NIR biological transparency windows, enabling cross-checking readings with high sensitivity and a high penetration depth. Utilizing the energy transfer between lanthanide ions and transition-metal ions, the Cr/Ln-activated upconversion emissions provide ideal signals for ratiometric luminescent thermometry of the NIR-I mode.

Investigation of high-concentration doping performance based on Er-ion-doped BaGdTiO.

Recently, various strategies have been explored during research into the use of lanthanide-doped luminescent materials to mitigate energy loss at elevated dopant concentrations. Herein we report Yb3+/Er3+ co-doped Ba6Gd2Ti4O17 (BGTO) phosphors with a laminated lattice structure, which can allow the high-concentration doping of Er3+ ions into the oxide. Detailed investigations into the luminescence properties and crystal structures of Yb3+/Er3+ co-doped BGTO reveal that an increase in the dopant concentration is associated with the dimensional limitation of energy transfer in the crystal lattice.

Upconversion luminescence and temperature sensing characteristics of Yb/Tm:KLa(MoO) phosphors.

Yb3+/Tm3+ codoped KLa(MoO4)2 phosphors are synthesized by a hydrothermal method. Under 980 nm excitation, the upconversion (UC) emission spectra of the phosphors are observed. The temperature sensing characteristic based on the fluorescence intensity ratio is studied.

What determines the performance of lanthanide-based ratiometric nanothermometers?

Luminescence intensity ratio (LIR) nanothermometers are ideally suited for noninvasive temperature detection of microelectronic devices and living cells, and the painstaking pursuit of new nanothermometers with higher absolute temperature sensitivity (Sa) or relative temperature sensitivity (Sr) has dominated recent research. However, whether higher Sa and Sr values can intrinsically improve the performance of LIR nanothermometers and what factors essentially determine their accuracy have rarely been considered; these considerations are instructive for their design and application while reducing time and costs. Here, we clarify that the accuracy of lanthanide-based LIR nanothermometers is essentially determined by Sr and the relative error of the luminescence intensity (σI/I) but not Sa based on lanthanide-doped NaYF4, YPO4, YVO4, CaF2, YF3, Y2O3, BaTiO3, LaAlO3 and Y3Al5O12 temperature sensors, meaning that our previous pursuit of higher Sa does not contribute to the accuracy of lanthanide-based LIR nanothermometers.

Superior temperature sensing of small-sized upconversion nanocrystals for simultaneous bioimaging and enhanced synergetic therapy.

The upconversion nanoparticles (UCNPs) exhibit versatility applications aiming at biological domains for decades on account of superior optical characteristics. Nevertheless, the UCNPs are confronted with tremendous difficulties in biological field owing to large grain size, low fluorescence efficiency, and single function. Herein, the small-sized CaF: Yb/Er UCNPs coated with NaGdF shells (activator and inert, UCNPs-RBHA-Pt-PEG) not only burst out strong fluorescence, but also provide prominent diagnosability by taking advantage of magnetic resonance (MR) imaging as well as temperature sensing and inhibiting capability for CT26 tumor tissues based on synergetic therapy modality of photodynamic therapy (PDT) and chemotherapy.

Prediction of Thermal-Coupled Thermometric Performance of Er.

Predicting the thermometric performance of diverse materials will facilitate the selection and design of nanothermometers to suit complex environments and specific signal outputs while saving much time and expense. Herein we explore and unveil the thermal-coupled thermometric performance of Er/Yb codoped in a set of host lattices via the chemical bond theory of complex crystals. The unknown and Δ values of the thermometry are accurately estimated by the chemical bond parameters, further deepening our cognition of the correlation between the luminescence properties of Er ions and the microscopic crystal structure.

One-pot synthesis of SiO-coated Gd(WO):Yb/Ho nanoparticles for simultaneous multi-imaging, temperature sensing and tumor inhibition.

Rare earth ion-doped fluoride upconversion nanoparticles (UCNPs), emerging as a novel class of probes and drug carriers, exhibit superior promise for bio-applications in diagnostics and treatment on account of their strong luminescence, fine biocompatibility, and high drug loading. However, the fine control and manipulation of particle size and the distribution of rare earth ion-doped oxides has remained an insurmountable challenge to date. In this work, we construct and synthesize silica-coated Gd2(WO4)3:Yb3+/Ho3+ nanoparticles by one-pot co-precipitation, with uniform distribution (∼130 nm) and enhanced yellow fluorescence.

Multifunctional Optical Thermometry Based on the Rare-Earth-Ions-Doped Up-/Down-Conversion BaTiGeO:Ln (Ln = Eu/ Er/ Ho/ Yb) Phosphors.

The fabrication of a multifunctional sensor together with a widening temperature-sensing range is an essential challenge in optical thermometers especially for trivalent lanthanide-doped materials. Herein, we design a wide range, highly sensitive, and multifunctional thermometer by exploiting the emission spectrum of Eu ions, and further detailed discussion has been made on the new temperature-sensing mechanism. The sensor can be operated between 358 and 548 K with a maximum relative sensitivity ( S) of 0.

Investigation on the Fluorescence Intensity Ratio Sensing Thermometry Based on Nonthermally Coupled Levels.

Fluorescence intensity ratio (FIR) of rare earth ions has been widely used in real-time and accurate temperature sensing because of its superiority of rapid response, self-reference, and noncontact in recent years. However, the energy gap (Δ) restriction of thermally coupled levels (TCLs) has hindered the sensitivity and practical use of such detectors. Herein, we investigate the FIR thermometry based on nonthermally coupled levels (NTCLs) of rare earth ions for fabricating a sensitive, precise temperature detector.

Investigating the Luminescence Behaviors and Temperature Sensing Properties of Rare-Earth-Doped BaInO Phosphors.

We present a strategy for selecting an optimal material in a particular temperature range by investigating the relationship between the absolute sensitivity ( S) and energy gap (Δ E), as well as the relationship between S and temperature on the basis of Yb/Ln (Ln = Er, Ho)-codoped BaInO phosphors. Through an investigation of optical performance, the phosphors exhibit near-infrared (NIR) downshifting and visible upconversion (UC) emissions under 980 nm excitation. The NIR spectral range from 700 to 1800 nm is referred to as the "biological window".

Investigation on Two Forms of Temperature-Sensing Parameters for Fluorescence Intensity Ratio Thermometry Based on Thermal Coupled Theory.

Absolute temperature sensitivity (S) reflects the precision of sensors that belong to the same mechanism, whereas relative temperature sensitivity (S) is used to compare sensors from different mechanisms. For the fluorescence intensity ratio (FIR) thermometry based on two thermally coupled energy levels of one rare earth (RE) ion, we define a new ratio as the temperature-sensing parameter that can vary greatly with temperature in some circumstances, which can obtain higher S without changing S. Further discussion is made on the conditions under which these two forms of temperature-sensing parameters can be used to achieve higher S for biomedical temperature sensing.

Inhomogeneous-Broadening-Induced Intense Upconversion Luminescence in Tm and Yb Codoped LuO-ZrO Disordered Crystals.

Near-infrared (980 nm) to near-infrared (800 nm) and blue (490 nm) upconversion has been studied in 0.2% Tm and 10% Yb codoped LuO-ZrO solid solutions as a function of the ZrO content in the range of 0-50%, prepared by a high-temperature solid-state reaction. The continuous enhancement of upconversion luminescence is observed with increasing ZrO content up to 30%.