Ratiometric Thermometer Research Articles

Novel Type of Non‐Toxic, Degradable, Luminescent Ratiometric Thermometers Based on Dyes Embedded in Disulfide‐Bridged Periodic Mesoporous Organosilica Particles

AbstractDespite the excellent thermometric performance of many developed luminescent nanomaterials, their use has not gone beyond proof‐of‐concept in vivo experiments to date. An important issue that needs to be resolved before moving toward true biomedical applications of engineered nanothermometers is their potential toxicity and bioaccumulation in the human body considering the ultimate objective of clinical applications. Since most reported nanothermometers currently are not degradable materials and are mainly based on the incorporation of heavy metal ions, these aspects remain of genuine concern in the fields of nanomedicine, nanobiotechnology, nanotoxicology, and nanopharmacology. This work explores the possibility of designing visible, as well as near‐infrared, emitting luminescent ratiometric nanothermometers based on appropriate organic dye mixtures embedded in hollow disulfide‐bridged periodic mesoporous organosilica (PMO) particles. Such hybrid particles show excellent thermometric performance in the physiological temperature range (20–50 °C), favorable degradability in simulated physiological conditions, as well as no toxicity to healthy normal human dermal fibroblast (NHDF) cells in a wide concentration range. Considering the simplicity of the approach from the synthetic point of view, and the large available library of known fluorescent dyes emitting in various regions of the electromagnetic range, this motif renders a very promising approach to designing novel non‐toxic, decomposable, luminescent ratiometric thermometers.

Regulating thermometric properties of single-band ratiometric luminescent thermometers based on Eu3+-activated Y2W3O12·3H2O nanoparticles via controlling doping content and excitation model

Series of Eu3+-activated Y2W3O12·3H2O nanoparticles were designed to realize high-sensitive optical thermometry. The resultant nanoparticles can emit bright visible emission from Eu3+ upon the excitation of 296 nm (charge-transfer state (CTS) of O2- → W6+), 394 nm (ground state absorption (GSA)) and 536 nm (excitation state absorption (ESA)), of which the fluorescence intensities were influenced by dopant content. The negative thermal expansion properties of studied nanoparticles were clarified via temperature-dependent X-ray diffraction patterns. Moreover, the thermal quenching behaviors of final products were also investigated through temperature-related emission spectra. Specifically, upon the CTS and GSA processes, the developed nanoparticles underwent significant thermal quenching effect, whereas the thermally enhanced luminescence was observed under ESA process. Herein, through using the single-band ratiometric (SBR) method to investigate the fluorescence intensity ratio of the red emission from 5D0 → 7F2 transition of Eu3+ at high temperature, the thermometric properties of prepared nanoparticles were studied. It was found that maximum absolute and relative sensitivities of Eu3+-activated Y2W3O12·3H2O nanoparticles reached up to 0.061 and 4.944 % K−1, respectively, and they can be regulated by changing Eu3+ dopant and SBR models (i.e., ESA+CTS and ESA+GSA combinations), realizing high-sensitive optical thermometry. Our findings may provide some guidelines for manipulating the thermometric properties of rare-earth ions activated materials and developing new SBR luminescence thermometers.

Triple-Decker Hexaazamacrocyclic Lanthanide(III) Complexes: Structure, Magnetic Properties, and Temperature-Dependent Luminescence.

The reaction of fluoride anions with mononuclear rare-earth(III) complexes of the hexaazamacrocycle derived from 2,6-diformylpyridine and ethylenediamine affords trinuclear coordination compounds [Ln3L3(μ2-F)4(NO3)2](NO3)3. The X-ray crystal structures of these complexes show triplex cationic complexes where the three roughly parallel macrocyclic lanthanide(III) units are linked by bis-μ2-F bridges. The detailed analysis of the photophysical properties of the [Eu3L3(μ2-F)4(NO3)2](NO3)3·2H2O and [Tb3L3(μ2-F)4(NO3)2](NO3)3·3H2O complexes reveals different temperature dependence of luminescence intensity and luminescence decay time of the Eu(III) and Tb(III) derivatives. The spectra of mixed species of average composition [Eu1.5Tb1.5L3(μ2-F)4(NO3)2](NO3)3·3H2O are in accordance with the ratiometric luminescent thermometer behavior. Measurements of the direct-current (dc) magnetic susceptibility of the [Dy3L3(μ2-F)4(NO3)2](NO3)3·2H2O complex indicate possible ferromagnetic interactions between the Dy(III) ions. Alternating current (ac) susceptibility measurements of this complex indicate single-molecule magnet behavior in zero dc field with magnetic relaxation dominated by Orbach mechanism and an effective energy barrier Ueff = 12.3 cm-1 (17.7 K) with a pre-exponential relaxation time, τ0 of 7.3 × 10-6 s. A similar reaction of mononuclear macrocyclic complexes with a higher number of fluoride equivalents results in polymeric {[Ln3L3(μ2-F)5](NO3)4}n complexes. The X-ray crystal structure of the Nd(III) derivative of this type shows trinuclear units that are additionally linked by single fluoride bridges to form a linear coordination polymer.

A novel Y/Eu co-doped Ln-MOF for ratiometric luminescent thermometer of high sensitivity

Lanthanide metal-organic frameworks (Ln-MOFs) co-doped by mixed lanthanide ions is a preeminent candidate for ratiometric luminescence thermometers. In recent years, there are few studies on the synthesis of such MOFs by introducing Ln3+ ions of no luminescent properties such as Y3+. Herein, a novel Y/Eu co-doped Ln-MOF (Y0.95Eu0.05NDPA, H4NDPA = 5,5′-naphthalene-1,4-diyl-diisophthalic acid) was synthesized via solvothermal methods, which showed good phase purity and thermal stability. Compared with EuNDPA, the Y3+ ions in Y0.95Eu0.05NDPA dilute the molar concentration of Eu3+, causing the emerge of ligand emission band. The luminescence intensity ratio of organic ligands and Eu3+ owns a good exponential dependence on temperature variation. As investigated, Y0.95Eu0.05NDPA owns the merits including a wide temperature sensing range (303–423 K), high relative sensitivity (3.04 %·K-1 at 423 K), good spectral repeatability (>92 %) and distinct emission color change from red to blue. This novel Y0.95Eu0.05NDPA ratiometric thermometer is expected to promote the application and development of dual-emission MOF materials in the field of microelectronic temperature measurement.

Improper Background Treatment Underestimates Thermometric Performance of Rare Earth Vanadate and Phosphovanadate Nanocrystals.

Luminescence thermometry is the state-of-the-art technique for remote nanoscale temperature sensing, offering numerous promising cutting-edge applications. Advancing nanothermometry further requires rational design of phosphors and well-defined, comprehensive mathematical treatment of spectral information. However, important questions regarding improper signal processing in ratiometric luminescence thermometry are continuously overlooked in the literature. Here, we demonstrate that systematic errors arising from background/signal superposition impact the calculated thermometric quality parameters of ratiometric thermometers. We designed ultraviolet-excitable (Y,Eu)VO4 and (Y,Eu)(P,V)O4 nanocrystals showing overlapped VO4 3- and Eu3+ emissions to discuss systematically how uncorrected background emissions cause magnified (∼10×) temperature uncertainties and undervalued (∼60%) relative thermal sensitivities. Adequate separation of spectral contributions from the VO4 3- background and the Eu3+ signals via baseline correction is necessary to prevent underestimation of the thermometric performances. The described approach can be potentially extended to other luminescent thermometers to account for signal superposition, thus enabling to circumvent computation of apparent, miscalculated thermometric parameters.

High sensitive ratiometric optical thermometer based on different multi-photon processes of upconversion luminescence in scheelite Ca1-xMgxWO4:Er3+/Yb3+ phosphors

The relative fluorescence intensity from different multi-photon processes is affected by the excitation light source fluctuation, which reduces the anti-interference and sensitivity of thermometers based on fluorescence intensity ratio (FIR) in upconversion (UC) luminescence. Ca1-xMgxWO4: Yb3+, Er3+ phosphors with scheelite structure were synthesized to investigate their anti-interference and higher temperature sensitivity. With x increasing from 0 to 1, the Bragg angle shifted toward higher angle, indicating that the larger disorders were introduced into the phosphors. The emissions assigned to Er3+ were enhanced with Mg2+ concentration increasing, attributed to oxygen vacancies according to the results of electron paramagnetic resonance. The photon numbers of upconversion luminescence assigned to 2H11/2 → 4I15/2, 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2 transitions of Er3+ were three- and two-photon processes, respectively. The ratio between the cube of 4S3/2 and the square of 2H11/2 emissions revealed higher temperature sensing performance and anti-interference on the excitation source power than the that between 4S3/2 and 2H11/2. The maximum relative sensitivity was 0.66 % K−1 at 300 K based on the common optical ratiometric thermometry. The maximum relative sensitivity based on the emissions assigned to different multi-photon processes was 7.2 % K−1 at 573 K. The dopants of Mg2+ composited of oxygen vacancies in CaWO4 crystals improved the luminous intensity and temperature sensing performance. This suggested the potential application of optical ratiometric thermometers based on different multi-photons of UC luminescence in temperature sensing field.

Temperature-Dependent Luminescence of Nd3+-Doped Carbon Nanodots for Nanothermometry.

Noncontact optical nanothermometers operating within the biological transparency windows are required to study temperature-sensitive biological phenomena at the nanoscale. Nanoparticles containing rare-earth ions such as Nd3+ have been reported to be efficient luminescence-based ratiometric thermometers, however often limited by poor water solubility and concentration-related quenching effects. Herein, we introduce a new type of nanothermometer, obtained by employing low-dimensional carbon nanodots (CNDs) as matrices to host Nd3+ ions (NdCNDs). By means of a one-pot procedure, small (∼7-12 nm), water-soluble nanoparticles were obtained, with high (15 wt %) Nd3+ loading. This stable metal-CND system features temperature-dependent photoluminescence in the second biological window (BW II) upon irradiation at 808 nm, thereby allowing accurate and reversible (heating/cooling) temperature measurements with good sensitivity and thermal resolution. The system possesses remarkable biocompatibility in vitro and promising performance at a high penetration depth in tissue models.

Ratiometric visualization fluorescence temperature sensing based on dual-lanthanide metal-organic frameworks

High-performance optical temperature sensors play an important role in various fields, and lanthanide metal-organic frameworks (Ln-MOFs) are expected to be luminescent temperature sensors due to their distinctive luminescent properties. Herein, a new three-dimensional (3D) Ln-MOF [Tb(TCA)(Phen)]·DEF (1) (H3TCA = 4,4′,4′'-nitrilotribenzoic acid, Phen = 1,10-phenanthroline, DEF= N, N-diethylformamide) is constructed with a rtl topology based on {Tb2(COO)4} secondary building units (SBUs). Meanwhile, dual-lanthanide Ln-MOFs [TbxEu1-x(TCA)(Phen)]·DEF (2-6) are also synthesized by varying the ratio of Tb3+: Eu3+ in the reaction mixture, which can be applied in practical LED applications originating from their visual luminescent color changes. Among them, 4 is an efficient ratiometric fluorescent thermometer over a wide temperature range from 283 to 393 K and has a large relative sensitivity Sr of 4.2407 % K−1 at 393 K with good repeatability. Furthermore, the emission color of 4 gradually changes from yellow (283 K) to orange-red (393 K) as temperature increases for visual colorimetric temperature measurements, which attributed to the energy transfer between Tb3+ and Eu3+ ions.

Role of host matrix on NIR emission and ratiometric thermometry properties in Nd3+/Yb3+ co-doped CaGd2(MO4)4 (M = W, Mo) phosphors

The development of ultrasensitive thermometric phosphors has become an active area of research due to their appealing applications in the contactless temperature detection field. Herein, the scheelite-related compounds—CaGd2(WO4)4: Nd3+, Yb3+ and CaGd2(MoO4)4: Nd3+, Yb3+, which exhibit high sensing capacity—are successfully prepared and systematically characterized. The X-ray diffraction analysis reveals that CaGd2(WO4)4: Nd3+, Yb3+ exhibits the monoclinic structure, whereas CaGd2(MoO4)4: Nd3+, Yb3+ is in the tetragonal phase. The maximum phonon cut-off energy of CaGd2(WO4)4: Nd3+, Yb3+ is 929 cm−1, slightly larger than that of CaGd2(MoO4)4: Nd3+, Yb3+ (904 cm−1). Irradiated by 980 nm laser, PL spectra consist of the Nd3+: 4Fj → 4I9/2 (j = 7/2, 5/2, 3/2) and Yb3+: 2F5/2 → 2F7/2 emissions located in the near-infrared (NIR) range. Negative and positive thermal quenching behaviors are observed for the emissions of Nd3+ (754, 802, and 868 nm) and Yb3+ (1008 nm), respectively, attributed to the cooperative effects of the phonon-assisted energy transfer process of Yb3+ → Nd3+ and excited state absorption process of Nd3+. Moreover, the host material can affect the luminescence properties, thermal enhancement factor of the NIR anti-Stokes emission, and thermal sensing performance of the Nd3+-Yb3+ pair. Consequently, CaGd2(MoO4)4: Nd3+, Yb3+ exhibits higher sensing sensitivity (Sr-max = ∼6.00%K−1) than CaGd2(WO4)4: Nd3+, Yb3+ (Sr-max = ∼5.56%K−1). This study provides useful information for the construction of high-performance ratiometric thermometers based on the inverse thermal dependence of the NIR emissions of Nd3+ and Yb3+ ions.

High-sensitivity ratiometric thermometers of Yb3+/Er3+/Tm3+ co-doped LuScO3 single crystal fibers based on non-thermally coupled energy levels

Fluorescence thermometry manifests tremendous attention for their potential applications in the temperature sensing, especially for combining wide operating temperature range with high sensitivity. However, the use of thermally coupled energy levels (TCLs) for temperature measurement has strict requirements for energy difference, which limits the sensitivity of detection. In order to satisfy higher sensitivity sensing, the pair of non-thermally coupled energy levels (NTCLs) of 4S3/2 and 3H4 has been innovatively designed. Herein, the sesquioxide Yb,Er,Tm co-doped LuScO3 single crystal fibers (SCFs) had been delicately grown by Laser Heated Pedestal Growth (LHPG) method. The fluorescence intensity ratio (FIR) thermometry was realized based on the Er3+:4S3/2→4I15/2 (545–593 nm) and Tm3+:3H4→3H6 (750–850 nm) NTCLs. Such an obvious FIR-temperature change through the NTCLs presents an outstanding optical thermometric performance, yielding the high temperature sensing with wide range. The maximum value of absolute sensitivity was 2 orders of magnitude higher than the temperature measurement using TCLs. More importantly, the sesquioxide Yb,Er,Tm:LuScO3 SCFs exhibit superior thermal stability that will be helpful to obtain high precision temperature measurement. Hence, our findings might offer some useful inspiration for exploring high-sensitivity luminescent thermometers and enriching the research of temperature measuring materials.

Interfacial compatible PolyMOF membranes as ratiometric fluorescence temperature sensors

Cryogenic temperature sensors play significant roles in manufacturing, metallurgy, and aerospace. Metal-organic frameworks (MOFs) as emerging crystal materials exhibited inherent advantages as fluorescence temperature sensors and researchers have shifted their focus toward incorporating MOFs materials into mixed matrix membranes (MMMs) for broader practical applications. However, the poor interfacial compatibility between MOFs particles and the polymer matrix would cause aggregation-induced fluorescence quenching and reduced energy transfer efficiency, thereby compromising temperature sensing performances. Herein, we adopt a post-synthetic copolymerization strategy to realize an interfacial-compatible membranous ratiometric luminescent thermometer based on the emissions of ligands and lanthanide ions. Benefiting from the controllable covalent cross-linking structures, the designed polyMOF membrane exhibited excellent interfacial compatibility and avoided MOFs irregular morphology agglomeration and phase separation, which contributed to outstanding fluorescence temperature sensing performance with excellent sensitivity ranging from 0.300 to 0.745 %·K−1 within the temperature range of 80–300 K, superior to recent reported MOFs-based thermometers. This research presents a promising approach for the design and fabrication of interfacial compatible MOFs-based membranes with excellent fluorescence temperature sensing properties, advancing the understanding of structure-property relationships and accelerating the practical applications.

Visible TADF and NIR Quenching Emission of Chromium Activated Zirconium‐Halide Perovskite Toward Ultra‐High‐Sensitive Ratiometric Fluorescent Thermometer

AbstractWith the development of science and technology, the measurement of temperature is receiving more and more attention. However, ratiometric fluorescent thermometers based on thermally coupled energy levels remain challenging because of their low relative sensitivity (Sr). In this work, chromium activated zirconium‐halide perovskite Cs2ZrCl6 microcrystals are successfully synthesized via a simple co‐precipitation method at room temperature. Interestingly, the host Cs2ZrCl6 exhibits reverse thermal quenching due to its thermal‐activated delayed fluorescence (TADF) behavior, while the Cr3+ dopant shows normal thermal quenching. Leveraging the difference in their temperature‐dependent luminescent properties, a ratiometric fluorescent thermometer is ingeniously developed, whose Sr reaches a maximum of 4.23% K−1. Besides, the as‐synthesized thermometer is demonstrated for mobile phone remote temperature measurement. This finding offers a new approach for the design of high‐sensitivity ratiometric fluorescent temperature sensors.

Temperature imaging inside fluid devices using a ratiometric near infrared (NIR-II/III) fluorescent Y2O3: Nd3+, Yb3+, Er3+ nanothermometer

Luminescence thermometry is a non-contact method that can measure surface temperatures and the temperature of the area where the fluorescent probe is located, allowing temperature distribution visualizations with a camera. Ratiometric fluorescence thermometry, which uses the intensity ratio of fluorescence peaks at two wavelengths with different fluorescence intensity dependencies, is an excellent method for visualizing temperature distributions independent of the fluorophore spatial concentration, excitation light intensity and absolute fluorescence intensity. Herein, Nd3+/Yb3+/Er3+-doped Y2O3 nanomaterials with a diameter of 200 nm were prepared as phosphors for temperature distribution measurement of fluids at different temperatures. The advantages of this designed fluorescent material include non-aggregation in water and the fact that its near-infrared (NIR) fluorescence excitation (808 nm) is not absorbed by water, thereby minimizing sample heating upon irradiation. Under optical excitation at 808 nm, the ratio of the fluorescence intensities of Yb3+ (IYb; 975 nm) and Er3+ (IEr; 1550 nm), which exhibited different temperature responses, indicated the temperature distribution inside the fluid device. Thus, this technique using Nd3+/Yb3+/Er3+-doped Y2O3 is expected to be applied for temperature distribution mapping analysis inside fluidic devices as a ratiometric NIR fluorescence thermometer, which is unaffected by laser-induced heating.Graphical abstract

Luminescent Ln3+-based silsesquioxanes with a β-diketonate antenna ligand: toward the design of efficient temperature sensors.

We report the synthesis and single-crystal X-ray diffraction, magnetic, and luminescence measurements of a novel family of luminescent cage-like tetranuclear silsesquioxanes (PhSiO1.5)8(LnO1.5)4(O)(C5H8O2)6(EtOH)2(CH3CN)2⋅2CH3CN (where Ln = Tb, 1; Tb/Eu, 2; and Gd, 3), featuring seven-coordinated lanthanide ions arranged in a one-capped trigonal prism geometry. Compounds 1 and 2 exhibit characteristic Tb3+ and Tb3+/Eu3+-related emissions, respectively, sensitized by the chelating antenna acetylacetonate (acac) ligands upon excitation in the UV and visible spectral regions. Compound 3 is used to assess the energies of the triplet states of the acac ligand. For compound 1, theoretical calculations on the intramolecular energy transfer and multiphonon rates indicate a thermal balance between the 5D4 Stark components, while the mixed Tb3+/Eu3+ analog 2, with a Tb:Eu ratio of 3:1, showcases intra-cluster Tb3+-to-Eu3+ energy transfer, calculated theoretically as a function of temperature. By utilizing the intensity ratio between the 5D4→7F5 (Tb3+) and 5D0→7F2 (Eu3+) transitions in the range 11-373K, we demonstrate the realization of a ratiometric luminescent thermometer with compound 2, operating in the range 11-373K with a maximum relative sensitivity of 2.0% K-1 at 373K. These findings highlight the potential of cage-like silsesquioxanes as versatile materials for optical sensing-enabled applications.

Insights into dual-emitting Eu-doped Mn–organic framework with 1D helical chain SBUs as a ratiometric thermometer for temperature sensing

The development and construction of smart luminescent MOF materials are highly desired. For the construction of luminescent MOF with new network and smart responsiveness, the introduction of Ln3+ into porous materials by the post-synthetic modification approach is one of the most effective strategies. Herein, a new anionic Mn–organic framework with 1D helical chain SBUs, [(CH3)2NH2][Mn3(OH)(TATB)2] (SQNU-24, H3TATB = 4,4′,4″-s-triazine-2,4,6-triyltribenzoic acid, SQNU = Shangqiu Normal University), was successfully prepared under a DMF/CH3CN solvent system. Benefitting from the anionic skeleton, high porosity, double-walled structure and 1D helical chain SBUs within SQNU-24, the dual-emitting Eu@SQNU-24 was successfully constructed by a post-synthetic modification approach. This work demonstrates the TATB3− ligand as an “antenna” can effectively sensitize Eu3+ ions. Interestingly, the dual-emitting Eu@SQNU-24 as a ratiometric thermometer exhibits a good temperature-responsive property.

Energy transfer enabled multiemission KBaLu(BO3)2:Ce3+,Mn2+,Tb3+ phosphors for ratiometric thermometers and WLED

Phosphors with multiband emissions have unique applications in thermometers and white LED, which can be readily realized by energy transfer. In this work, the energy transfers from Ce3+ to Mn2+/Tb3+ have been successfully constructed to achieve multiband emission in the KBaLu(BO3)2 (KBLBO) phosphors. KBLBO:Ce3+ can be efficiently excited by the near-ultraviolet light and shows a broad emission band at 453 nm. On the basis of the energy transfer from the Ce3+ to Mn2+/Tb3+ ions, KBLBO:Ce3+,Mn2+/Tb3+ exhibits a multiband emission consists of blue and red bands/green bands. The KBLBO:0.02Ce3+,0.03Mn2+ phosphor can function as a ratiometric thermometer with high temperature sensing performance by taking use of the differences in the thermal quenching behavior between the Ce3+ and Mn2+ ions. Moreover, a single-phase white light emitting phosphor KBLBO:0.02Ce3+,0.03Mn2+,0.01 Tb3+ was obtained. Meanwhile, the as-prepared WLED device exhibits CRI of 87.1 and CCT of 5090 K. Our work not only reveals the multifunctionality of the new KBLBO phosphors, but also points out the design and utilization strategies of multiband emission phosphors based on energy transfer.

Customizing thermometry: Optimizing the operating temperature range of phase transition-based ratiometric luminescence thermometers

Phase transition-based thermometers, which are widely known for their remarkable sensitivity to temperature changes, exhibit a narrow temperature range owing to the stoichiometry of the host material. This limits the applicability of optical sensors utilizing structural phase transitions. In this study, we introduce a co-doping method for modulating the properties of phase transition-based luminescent thermometers to influence the phase transition temperature. We demonstrate that by adjusting the ionic radius of the dopant and its concentration, the transition temperature can be finely tuned across a broad temperature spectrum. The proposed technique enables the customization of luminescent thermometers with enhanced sensitivities and practical temperature ranges tailored to specific user requirements. This study represents a crucial advancement towards the development of personalized luminescence thermometers.

Enhanced temperature sensing properties in LiYGeO4: Eu3+ phosphors via Bi3+ doping

Luminescent thermometry has been irreplaceable role in non-contact temperature sensing. However, the relative sensitivity (Sr) in some rare earths doped fluoride up-conversion materials still limited below 1% K−1. Herein, Eu3+ doping LiYGeO4 (LYGO) phosphors enabled ratio-metric thermometer based on thermal enhancement of Eu−O charge transfer band (CTB) and thermal quenching of 4f-4f transition. The Sr was achieved 0.64% K−1 in LYGO: Eu3+ at 313 K. Furthermore, we presented a temperature-responsive phosphor through Bi3+/Eu3+ co-doped LYGO, the excitation intensities of Bi3+ ions decreased significantly with rising temperature, which realized more than twice of magnitude changes in the Sr (1.76% K−1). In addition, LYGO: Eu3+ phosphors also featured excellent red emission and high thermal stability. All the results indicated that LYGO: Eu3+ and LYGO: Eu3+, Bi3+ phosphors can be potentially candidate for white light-emitting diode (WLED) and temperature sensing.

Novel GdAlGe2O7:Bi3+,Eu3+ phosphors with anti-thermal quenching properties for high sensitivity optical temperature measurement

The thermometry technique based on fluorescence intensity ratio has attracted much attention for its advantages of fast response, high accuracy, and non-contact. Here, we report a series of novel GdAlGe2O7:Bi3+,Eu3+ phosphors with anti-thermal quenching properties for high sensitivity optical temperature measurement. By constructing the energy transfer between Bi3+ and Eu3+ ions, the GdAlGe2O7:Bi3+,Eu3+ exhibits a rare anti-thermal quenching performance upon 285 nm excitation due to the redshift of the charge transfer band. Therefore, we designed ratiometric optical thermometers with high sensitivity based on the intense thermal quenching behavior of the Bi3+ ions and the anti-thermal quenching property of the Eu3+ ions with a relative sensitivity of 1.06% K−1 at 483 K and an absolute sensitivity of up to 0.0447 K−1 at 573 K. Our results not only reveal the optical behaviors of the Bi3+ and Eu3+ ions in GdAlGe2O7:Bi3+,Eu3+, but also propose that the synthesized phosphors have significant potential applications in the field of optical temperature measurement.

Construction of Highly Luminescent Lanthanide Coordination Polymers and Their Visualization for Luminescence Sensing.

NaH2SIP was selected as an organic ligand (NaH2SIP = 5-sulfoisophthalic acid monosodium salt). We successfully constructed a new class of lanthanide coordination polymers Ln-HS ([Ln(SIP)(DMF)(H2O)4]DMF·H2O; Ln = Eu, Tb, Sm, and Dy) by a simple solvothermal synthesis method. They exhibited excellent photoluminescence properties for Ln3+ ions, where Eu-HS and Tb-HS exhibited high quantum yields of 13.70 and 42.38%, respectively. The codoped lanthanide coordination polymers obtained by doping with different ratios of Eu3+/Tb3+ serve as excellent ratiometric thermometers with high sensitivities in the physiological temperature range, with values of 16.8, 7.0, and 14.5%·K-1, respectively. The luminescent colors of Tb0.95Eu0.05-HS and Tb0.94Eu0.06-HS exhibit variations from green to yellow to orange, achieving visualized luminescence in a narrow temperature range. The composite film material Tb0.94Eu0.06-HS@PMMA demonstrates this color variation. Next, Tb0.5Sm0.5-HS obtained by Tb3+/Sm3+ codoping was investigated. The difference in the luminescence colors visible to the naked eye at different excitation wavelengths and the change in luminescence colors occur in a very narrow temperature range. All of them show the great value of the visualized luminescence in practical anticounterfeiting, with double anticounterfeiting function and high security.