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 Tm3+, Ho3+, and Er3+ emissions induced by efficient energy transfer. The outstanding negative thermal expansion characteristic of ScF3 nanocrystals has been found to guide excitation energy toward the relevant emitting states in the Yb3+-Ho3+-Tm3+-codoped system, consequently resulting in remarkable near-infrared III (NIR-III) luminescence at ∼1625 nm (Tm3+:3F4 → 3H6 transition), which in turn presents numerous opportunities for designing multimode ratiometric luminescence thermometry. Furthermore, by facilitating phonon-assisted energy transfer in Er3+-Ho3+-codoped systems, the luminescence intensity ratio (LIR) of 4I13/2 of Er3+ and 5I6 of Ho3+ in ScF3:Yb3+/Ho3+/Er3+ exhibits a strong temperature dependence, enabling NIR-II/III luminescence thermometry with superior thermal sensitivity and resolution (Sr = 0.78% K-1, δT = 0.64 K). These findings not only underscore the distinctive and ubiquitous attributes of lanthanide ion-doped nanomaterials but also hold significant implications for crafting luminescence thermometers with unparalleled sensitivity.

Tuning the Red-to-Green-Upconversion Luminescence Intensity Ratio of Na3ScF6: 20% Yb3+, 2% Er3+ Particles by Changes in Size

Na₃ScF₆: 20% Yb³⁺, 2% Er³⁺ samples were synthesized with different reaction times and reaction temperatures using the solvothermal method. We carried out a series of tests on Na3ScF6 crystals. The XRD patterns showed that the monoclinic phases of the Na₃ScF₆ samples could be synthesized under different reaction conditions, and doping with Yb³⁺ ions and Er³⁺ ions did not change the crystal structures. The SEM images showed that the sizes of the samples gradually increased with reaction time and reaction temperature. The fluorescence spectra showed that the emission peaks of the prepared samples under 980 nm near-infrared (NIR) excitation were centered at 520 nm/543 nm and 654 nm, corresponding to the ²H_11/2/⁴S_3/2→⁴I_15/2 and ⁴F_9/2→⁴I_15/2 transitions, respectively. With the increasing size of the samples, the emission intensities at 654 nm increased and the luminescence colors changed from green to red; at the same time, the red-to-green luminescence intensity ratios (IR/IG ratios) increased from 0.435 to 15.106-by as much as ~34.7 times. Therefore, this paper provides a scheme for tuning the IR/IG ratios of Na₃ScF₆: 20% Yb³⁺, 2% Er³⁺ samples by changing their sizes, making it possible to enhance the intensity of red upconversion, which has great potential for the study of color displays and lighting.

A lanthanide ion-doped Ba3Sc2F12 phosphor: hydrothermal synthesis, morphological control, energy transfer, and temperature-sensing performance

Ba₃Sc₂F₁₂ crystals were synthesized by a facile one-step hydrothermal method with Ba/Sc raw material in a ratio of 3 : 2. With the F/Sc ratio increasing from 4 to 8, the obtained crystal's morphology evolved gradually from a strip to a chocolate shape; further, the use of the additives, such as CTAB and EDTA, the obtained crystal's morphology changed from strip to cubic. The energy transfer of Ce³⁺→ Tb³⁺ in the Ba₃Sc₂F₁₂ host was also explored, and it was found to belong to a dipole-dipole interaction mechanism; the color of the light could be adjusted from blue-violet to green due to the different energy transfer efficiencies at different Ce³⁺ and Tb³⁺ ion-doping concentrations. Because of the thermal coupling level of Er³⁺ (²H_11/2→⁴I_15/2 and ⁴S_3/2→⁴I_15/2), Ba₃Sc₂F₁₂:14%Yb³⁺,2%Er³⁺ phosphors showed an excellent temperature-sensing ability with S_A(max) = 0.0043 K^-1 and T_max = 523 K, which are much better than the previously reported values for Yb³⁺/Er³⁺ co-doped systems. The as-prepared lanthanide ion-doped phosphors might have potential to serve as color light/displays and temperature control/sensors.

Temperature sensing performance based on up-conversion luminescence in hydrothermally synthesized Yb3+/Er3+ co-doped NaScF4 phosphors

NaScF₄:Yb³⁺/Er³⁺ crystals were successfully hydrothermally synthesized using distilled water as a single solvent.

Lanthanide-doped KYb3F10 crystals: controllable phases, rich morphologies and Tb3+/Eu3+ down-conversion emission

KYb₃F₁₀:Ln³⁺ (Ln = Er, Ho, Tb, Gd, Eu, Sm, Ce and La) micro/nanocrystals with abundant morphologies were synthesized via a one-step hydrothermal route without employing any surfactants.

One-step surfactant-free synthesis of KSc2F7 microcrystals: controllable phases, rich morphologies and multicolor down conversion luminescence properties

The obtained products show controlled phases and abundant morphologies with the increase of fluoride ion concentration.

Size of the rare-earth ions: a key factor in phase tuning and morphology control of binary and ternary rare-earth fluoride materials

An IL based solvothermal route to prepare RE ion doped luminescent binary/ternary fluoride nanomaterials. Size of the RE ions tunes the nature of the product, crystal phase, lattice strain and morphology, effecting the luminescence properties.

Preparation and temperature-dependent photoluminescence properties of ScF3:Eu3+ submicroparticles

Negative thermal expansion Eu³⁺-doped ScF₃ submicroparticles were prepared via a facile solvothermal method and their temperature-dependent luminescence properties were investigated.

Near-infrared-light-mediated high-throughput information encryption based on the inkjet printing of upconversion nanoparticles

Background-free and high-throughput information encryption on paper is realized by the inkjet printing of upconversion nanoparticles.

From ScOOH to Sc2 O3 : Phase Control, Luminescent Properties, and Applications

In the controlled synthesis of ScOOH nanomaterials, the surfactant molecule Na3 Cit not only helps to manipulate the crystallographic structures, but also to initiate the transfer from α-ScOOH to γ-ScOOH. Further annealing of ScOOH generates cubic Sc2 O3 with morphologies inherited from respective origins. When doped with lanthanide ions, both ScOOH and Sc2 O3 can be utilized for high-temperature probing and light-emitting-diode lighting.

White light-emitting, tunable color luminescence, energy transfer and paramagnetic properties of terbium and samarium doped BaGdF5 multifunctional nanomaterials

Multicolor luminescence of BaGdF₅:Tb³⁺,Sm³⁺ nanospheres can be obtained by adjusting the excitation wavelength. The obtained phosphors also exhibit paramagnetic properties at room temperature and low temperature.

Magnetic-downconversion luminescent bifunctional BaGdF5:Dy3+,Eu3+ nanospheres: energy transfer, multicolor luminescence and paramagnetic properties

The color-tunable and white light emissions have been obtained in Dy³⁺ and Eu³⁺ co-activated BaGdF₅ phosphors by adopting different excitation wavelengths. Simultaneously, the obtained samples also exhibit paramagnetic properties at room temperature and low temperature.

Enhanced red upconversion emission, magnetoluminescent behavior, and bioimaging application of NaSc0.75Er0.02Yb0.18Gd0.05F4@AuNPs nanoparticles

The present study reports significant enhancement in the red upconversion emission of Er(3+) in NaSc0.8Er0.02Yb0.18F4 upconversion nanoparticles (UCNPs), via a two step process, (i) codoping of Gd(3+) ion at Sc(3+) site and (ii) attaching gold nanoparticles (AuNPs) at the surface of these codoped nanostructures, and further probes the use of these Gd:UCNPs@AuNPs for bioimaging application. The Gd(3+) codoping tailors the particle size (reduces) of UCNPs and bring out Er(3+)-Yb(3+) ion pair in close proximity, which promotes the cross relaxation mechanism and boosts the population in red emitting level (4)F9/2. Further, attachment of AuNPs on the surface of UCNPs gives 2-fold advantages, that is, reduction in green band (through resonance energy transfer with efficiency 31.54%) and enhancement in red band (through plasmonic effect). It gives red to green (R/G) ratio nearly 20:1 (almost single band red UC), which is quite promising for imaging application. In addition to this, codoping of Gd(3+) enhances the magnetic moment appreciably and the obtained magnetic moment for NaSc0.75Er0.02Yb0.18Gd0.05F4 UCNPs (∼1.7 emu/g) is close to the reported values for bioseparation in case of NPs. This shows the potential of the material for multimodal (optical and magnetic both) imaging application. These magnetoluminescence particles were found safe up to 1 mg/mL dose as assessed by cytotoxicity measurement in human cervical cancer (HeLa) and lung cancer (A549) cells. Ultrafine nanoparticles, transparent, and stable colloidal solution and the unique red UC emission endow these NPs as optical probe for imaging applications.

Tunable color and energy transfer of Tm3+ and Ho3+ co-doped NaGdF4 nanoparticles

NaGdF₄:Tm³⁺, Ho³⁺ nanoparticles with luminescence properties were synthesized by a hydrothermal method. The hues could be tuned from blue through to light blue and ultimately to bluish green.

Highly efficient NIR to visible upconversion in a ZnO:Er,Yb thin film deposited by a AACVD atmospheric pressure process

A ZnO:Er,Yb hexagonal wurtzite phase structured thin film with highly efficient NIR to visible upconversion emissions.