Rare earth material and preparation method and application thereof

Abstract

The invention discloses a rare earth material and a preparation method and application thereof, the stoichiometric formula of the rare earth material is Bi2WO6: mA < 3 + >, m is more than or equal to 0.005 and less than or equal to 0.1, and A is Nd, Er and Yb. According to the rare earth material disclosed by the invention, high-stability, anti-interference and high-precision non-contact temperature measurement is realized; after the material is soaked in water for a long time or recycled, the fluorescence performance (especially the key ratio parameter of temperature measurement) is kept highly stable, obvious attenuation or drifting is avoided, absorption of a water environment to a fluorescence signal of the material is not obviously reduced, background noise interference is effectively inhibited, and the signal-to-noise ratio is increased; a fluorescence intensity ratio method is used as a temperature measurement parameter, system errors such as excitation light source fluctuation, uneven concentration and influence caused by background noise are eliminated, and absolute temperature measurement precision and repeatability are improved; and low-toxicity or non-toxic rare earth elements and matrix materials are selected, so that the environmental safety is ensured.

Description

Technical Field

[0001] This application relates to the field of rare earth materials technology, and in particular to a rare earth material, its preparation method, and its application. Background Technology

[0002] Near-infrared responsive rare-earth upconversion nanomaterials have advantages such as tunable particle size, good photostability, low background fluorescence interference, and low photodamage, and have broad application potential in fluorescence imaging and fluorescence thermometry in tissues or cells.

[0003] Rare earth ion doping of various matrix materials has attracted widespread attention from researchers in fluorescence thermometry and bioimaging. To expand the application of these materials in aquatic environments, some researchers have optimized the structure of luminescent materials and analyzed the luminescence and fluorescence thermometry performance of different luminescent materials in aquatic environments. However, the fluorescence thermometry sensitivity of these luminescent materials in aquatic environments is not ideal.

[0004] Existing water environment thermometric materials have the following problems: poor adaptability to water environments; most fluorescent thermometric materials (such as organic dyes, quantum dots, and some inorganic phosphors) have poor stability in water, and are prone to aggregation, decomposition, or fluorescence quenching; and they are also susceptible to common ions in water (such as Cl-). - Na + ,K + Ca 2+ Mg 2+ Dissolved oxygen causes fluctuations in fluorescence signals, leading to large temperature measurement errors; severe background interference, such as Raman scattering from water and the autofluorescence of organic matter, can drown out weak temperature fluorescence signals and reduce the signal-to-noise ratio; the temperature measurement mechanism is limited, and materials relying on a single fluorescence intensity are easily affected by factors such as fluctuations in the excitation source, uneven material concentration, and the influence of background noise, resulting in low accuracy. For some fluorescence lifetime-based temperature measurement materials, the lifetime measurement equipment is usually complex and expensive, and the optical path transmission loss is large in water, increasing the measurement difficulty; there is a lack of targeted design, and existing material designs rarely optimize for the special challenges of the aquatic environment (such as ion shielding, hydrophilic / hydrophobic balance, and resistance to biofouling).

[0005] Therefore, developing a stable fluorescent material that can be used for temperature measurement in an aqueous environment is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] In view of this, this application provides a rare earth material that has higher stability in an aqueous environment. After long-term immersion in water or repeated use, its fluorescence performance (especially the ratio parameter that is key to fluorescence thermometry) remains highly stable without significant attenuation or drift.

[0007] Bi₂WO₆ has relatively low phonon energy and good physicochemical stability, making it a good matrix material for upconversion luminescence and temperature sensing. This application prepared Nd... 3+ Er 3+ Yb 3+ The microstructure of Bi2WO6 doped powder materials and their upconversion luminescence and temperature sensing properties in an aqueous environment were analyzed, aiming to obtain Bi2WO6-based fluorescent thermometric materials with higher stability and better temperature sensitivity for use in aqueous fluorescent thermometry.

[0008] This application provides a rare earth material, the stoichiometric formula of which is Bi2WO6:mA 3+ Where 0.005≤m≤0.1, and A represents Nd, Er, and Yb. 3+ The optimal selection of thermally coupled and non-thermally coupled energy levels is the main approach to achieving high-sensitivity FIR. Alternatively, Ho can be selected. 3+ Tm 3+ Eu 3+ Dy 3+ The anion is tungstate.

[0009] Rare earth ions with temperature-dependent energy transfer relationships were carefully selected as fluorescence centers. The efficient and innovative choice is Nd... 3+ / Er 3+ The thermal coupling of energy levels can enable high-sensitivity FIR temperature measurement.

[0010] In some specific implementations, 0.05 ≤ m ≤ 0.09 can be 0.05, 0.06, 0.08, or 0.09. The thermally coupled energy level of rare-earth ion energy levels can achieve high-sensitivity FIR temperature measurement, by introducing Nd... 3+ Utilizing Nd 3+ To Er 3+ The energy transfer process can provide a highly sensitive temperature measurement channel (based on the fluorescence intensity ratio of the non-thermally coupled energy level pairs of the luminescent center), and the emission wavelength is located in the low absorption window of water (such as Er). 3+ (540nm) to reduce water absorption interference. The ion doping concentration is the molar concentration. In some specific implementations, 0.005≤m≤0.09, and B is Nd, Er, and Yb. Nd 3+ Yb has a large absorption cross-section for 808nm laser, and serves as a main sensitizer and near-infrared absorber. 3+ As a bridging sensitizer, it can promote the transfer of energy from the excited state to the activator ion Er. 3+ This increases the luminescence intensity of the activator and improves the fluorescence signal-to-noise ratio. In some specific implementations, the stoichiometric formula of the rare earth material is Bi2WO6:x%Nd. 3+ y%Er3+ ,z%Yb 3+ 0.5≤x≤3, y=1.5, 0.5≤z≤9. In some specific implementations, the stoichiometric formula of the rare earth material is Bi2WO6:0.5%Nd 3+ 1.5% Er 3+ 3% Yb 3+ In some specific implementations, the particle size of the rare earth material is from 1 μm to 5 μm, specifically 1 μm, 1.5 μm, 2 μm, 3 μm, 4 μm, or 5 μm. The rare earth material is controlled to ensure good dispersibility in water and potential application possibilities. Precise control of the crystal phase (e.g., Bi₂WO₆ has an orthorhombic crystal structure) and powder morphology (near-spherical, etc.) optimizes luminescence efficiency. In some specific implementations, bismuth tungstate is preferred as the inorganic matrix. In addition, fluorides, vanadates, phosphates, garnets, oxides, or sulfides can also be used as the inorganic matrix. A rare earth-doped inorganic matrix that is stable to water and has excellent optical properties is selected, with bismuth tungstate (Bi₂WO₆) being preferred due to its good physicochemical stability, good thermal stability within a certain temperature range, and relatively low phonon energy, which helps reduce the non-radiative relaxation probability caused by phonon vibrations and improve upconversion luminescence efficiency.

[0011] In some specific implementations, the rare earth material further includes a surface modification layer, which comprises an inorganic layer, an organic layer, and a bifunctional shell. SiO2 is the most commonly used and mature material. Al2O3 (which can achieve ultrathin and uniform coating through atomic layer deposition (ALD)), TiO2, and ZnO can also be used as inorganic layers. Alternatively, biocompatible polymers (such as polyacrylic acid PAA, polyethyleneimine PEI, and chitosan) can be used for encapsulation, or multiple NPs can be encapsulated in polymer microspheres. The advantages are good hydrophilicity and ease of functionalization. PEG, polyacrylamide (PAM), polycarboxylate, and polysaccharides (such as dextran) can also be used for surface modification. A bifunctional shell, for example, first coating a thin layer of SiO2 and then coating a layer of functional polymer, can combine the advantages of both.

[0012] This application also provides a method for preparing rare earth materials, including:

[0013] Bismuth oxide, tungsten oxide and rare earth oxides are mixed and calcined to obtain rare earth materials;

[0014] The rare earth oxides include Er2O3, Yb2O3 and Nd2O3.

[0015] In some specific implementations, the calcination temperature is between 350℃ and 800℃, and can be 350℃, 400℃, 450℃, 500℃, 550℃, 600℃, 650℃, 700℃, 750℃, or 800℃; the calcination time is between 3h and 5h, and can be 3h, 4h, or 5h. In some specific implementations, the calcination includes first heating from 50℃ to 350℃ at a heating rate of 3℃ / min, then heating from 350℃ to 800℃ at a heating rate of 5℃ / min, and finally calcining at 800℃. The preparation method described in this application is a high-temperature solid-state method; hydrothermal / solvothermal methods, thermal decomposition methods, co-precipitation methods (simple but difficult to control particle size and morphology), sol-gel methods, etc., can also be used. In some specific implementations, the mixture of bismuth oxide, tungsten oxide and rare earth oxide is ground and then calcined. The grinding time is 20 to 30 minutes, and the calcination is followed by cooling to room temperature.

[0016] This application also provides a method for measuring the temperature of a water environment, including:

[0017] The emission spectra of rare earth materials and water suspensions at different temperatures were collected under near-infrared excitation light source. The emission peaks of thermally coupled or non-thermally coupled energy level pairs were selected. The fluorescence intensity ratio of the two emission peaks was used to calculate the relationship between the fluorescence intensity ratio and temperature. The temperature was determined based on the fluorescence intensity ratio-temperature curve.

[0018] The rare earth material is the rare earth material described above or prepared by the method described above. In some specific implementations, the wavelength of the near-infrared excitation source is 808 nm. The material is excited using a specific wavelength, and the fluorescence spectrum emitted by the material is collected. The FIR method is used to calculate the intensity ratio of two preset characteristic fluorescence peaks (FIR = I1 / I2). This ratio FIR is a function of temperature T (FIR = f(T)). The FIR-T relationship curve is precisely calibrated beforehand at a known temperature (thermally coupled energy levels are usually fitted using the Boltzmann formula: FIR = I1 / I2 = A exp(-ΔE / kT) + B, and non-thermally coupled energy level pairs are usually fitted using a polynomial: FIR = I1 / I2 = A1 + B1T + B2T). 2 +B3T 3The current temperature T can be deduced from the real-time measured FIR value. Due to the excellent water environment stability and anti-interference properties of the material, the collected FIR mainly reflects the temperature change in the distilled water environment, thus ensuring high accuracy and reliability of the measurement. In some specific implementations, the rare earth material has multiple emission peaks, and two of the best emission peaks are selected for calculation. In some specific implementations, the turbidity of the suspension of the rare earth material with water is 20 NTU to 100 NTU, which can be 20 NTU, 30 NTU, 40 NTU, 50 NTU, 60 NTU, 70 NTU, 80 NTU, 90 NTU, or 100 NTU.

[0019] This application provides a novel rare earth material and its preparation method specifically designed for aquatic environments (especially complex and biological aquatic environments), achieving highly stable, interference-resistant, and high-precision non-contact temperature measurement. After long-term immersion or recycling in water, the fluorescence performance (especially the critical ratio parameter for temperature measurement) remains highly stable, with no significant attenuation or drift, and no significant reduction in the absorption of the material's fluorescence signal by the aquatic environment, effectively suppressing background noise interference and improving the signal-to-noise ratio. The fluorescence intensity ratio method (FIR) uses the excellent stability of fluorescence lifetime as a temperature measurement parameter, eliminating systematic errors such as excitation source fluctuations, concentration unevenness, and the influence of background noise, thereby improving absolute accuracy and repeatability. Low-toxicity or non-toxic rare earth elements and matrix materials are selected to ensure environmental safety. Attached Figure Description

[0020] Figure 1 The X-ray diffraction patterns of the rare earth materials provided in Examples 1-5, 6 and 7 of this application are shown, where 1(a) represents Examples 1, 6 and 7, and 1(b) represents Examples 2-5.

[0021] Figure 2 The emission spectra of rare earth materials provided in Examples 1-4, 6 and 7 of this application under 808 nm excitation, where 2(a) are Examples 1, 6 and 7, and 2(b) are Examples 2-4;

[0022] Figure 3 The energy level transition diagrams of the rare earth materials provided in Examples 1-4, 6, and 7 of this application under 808 nm excitation are shown.

[0023] Figure 4 The rare earth material provided in Example 3 of this application exhibits a temperature-varying upconversion emission spectrum in the temperature range of 298-573K under 808 laser (464mW) excitation.

[0024] Figure 5 Er in Example 3 3+ The graphs show the fluorescence intensity ratios at 525nm and 546nm, and 525nm and 654nm, versus temperature, where 5(a) is based on 525nm (2 H 11 / 2 → 4 I 15 / 2 ) and 546nm ( 4 S 3 / 2 → 4 I 15 / 2 ) fluorescence intensity ratio, 5(b) is based on 525nm ( 2 H 11 / 2 → 4 I 15 / 2 ) and 654nm ( 4 F 9 / 2 → 4 I 15 / 2 Fluorescence intensity ratio;

[0025] Figure 6 This is a graph showing the change in temperature sensitivity of the rare earth material provided in Example 3 of this application, where 6(a) is based on FIR. 525nm / 546nm 6(b) Based on FIR 525nm / 654nm ;

[0026] Figure 7 The upconversion emission spectra of rare earth materials provided in Example 3 of this application in an aqueous environment with 20 NTU, 60 NTU, and 100 NTU suspensions under 808 nm (464 mW) laser excitation;

[0027] Figure 8 The temperature-dependent upconversion emission spectrum of the rare earth material provided in Example 3 of this application in a 100 NTU sample excited in a water environment at 808 nm.

[0028] Figure 9 The graph shows the change in fluorescence intensity ratio at 546 nm / 654 nm for a 100 NTU sample in an 808 nm excited water environment, as a function of temperature, for the rare earth material provided in Example 3 of this application.

[0029] Figure 10 The rare earth material provided in Example 3 of this application was tested in an 808 nm excited water environment with a 100 NTU sample based on FIR. 525nm / 654nm The graph shows the change in temperature sensitivity as a function of temperature.

[0030] Figure 11 This is a temperature resolution map of the rare earth material provided in Example 3 of this application, where 11(a) is a FIR-based image of the rare earth powder material provided in Example 3. 525nm / 546nm FIR 525nm / 654nm Temperature resolution varies with temperature; 11(b) shows the FIR-based resolution of a 100 NTU sample in an aquatic environment. 546nm / 654nm Temperature resolution varies with temperature;

[0031] Figure 12The temperature-varying chromaticity coordinates of a 100 NTU sample of rare earth material provided in Example 3 of this application under 808 nm excitation in air or water are shown; (a) in air, (b) in water. Detailed Implementation

[0032] It should be understood that the expression “one or more of…” individually includes each of the objects described after the expression, as well as various combinations of the different components of the three described objects, unless otherwise understood from the context and usage. The expression “and / or” combined with three or more described objects should be understood to have the same meaning, unless otherwise understood from the context.

[0033] The terms “including,” “having,” or “containing,” including the use of their grammatical synonyms, should generally be understood as open-ended and non-restrictive, for example, not excluding other unstated elements or steps, unless otherwise specifically stated or understood from the context.

[0034] It should be understood that the order of steps or the sequence of actions is not important as long as this application remains operational. Furthermore, two or more steps or actions can be performed simultaneously.

[0035] The use of any and all instances or exemplary language such as “e.g.” or “include” in this document is intended merely to better illustrate the application and does not constitute a limitation on the scope of the application. No language in this specification should be construed as indicating that any unclaimed element is essential to the practice of this application.

[0036] Furthermore, the numerical ranges and parameters used to define this application are approximate values, and the relevant values ​​in the specific embodiments have been presented as precisely as possible. However, any value inevitably contains standard deviations due to individual test methods. Therefore, unless otherwise explicitly stated, it should be understood that all ranges, quantities, values, and percentages used in this disclosure are modified with the word "approximately." Here, "approximately" generally means an actual value within plus or minus 10%, 5%, 1%, or 0.5% of a particular value or range.

[0037] This application provides a rare earth material, the stoichiometric formula of which is Bi2WO6:mA 3+ Where 0.005≤m≤0.1, and A can be Nd, Er, or Yb.

[0038] This application also provides a method for preparing rare earth materials, including:

[0039] Bismuth oxide, tungsten oxide and rare earth oxides are mixed and calcined to obtain rare earth materials;

[0040] The rare earth oxides include Er2O3, Yb2O3 and Nd2O3.

[0041] This application also provides a method for measuring the temperature of a water environment, including:

[0042] The fluorescence intensity at the emission wavelength was collected by exciting an aqueous solution of rare earth material under the excitation light source; the fluorescence intensity ratio was calculated, and the temperature was determined according to the pre-calibrated ratio-temperature curve.

[0043] This application provides a novel rare earth material and its preparation method specifically designed for aquatic environments (especially complex and biological aquatic environments), achieving highly stable, interference-resistant, and high-precision non-contact temperature measurement. After long-term immersion or recycling in water, the material's fluorescence performance (especially the critical ratio parameter for temperature measurement) remains highly stable, with no significant attenuation or drift, and no significant reduction in the absorption of the material's fluorescence signal by the aquatic environment, effectively suppressing background noise interference and improving the signal-to-noise ratio. The fluorescence intensity ratio method or the fluorescence lifetime with excellent stability is used as the temperature measurement parameter to eliminate systematic errors such as excitation light source fluctuations, concentration unevenness, and the influence of background noise, thereby improving absolute accuracy and repeatability. Low-toxicity or non-toxic rare earth elements and matrix materials are selected to ensure environmental safety.

[0044] The present application is further illustrated below with reference to embodiments. The scope of protection of the present application is not limited to the following embodiments.

[0045] Example 1

[0046] This embodiment provides a rare earth material, the preparation method of which includes:

[0047] According to the stoichiometric ratio, the raw materials Bi₂O₃ (99.9%), WO₃ (99.99%), Er₂O₃ (99.99%), Nd₂O₃ (99.99%), and Yb₂O₃ (99.99%) powders were weighed using an AL104 electronic balance, mixed, and ground for 25 min. The mixture was then placed in a muffle furnace (SX-12-16) and calcined in air (increasing the temperature from 50℃ to 350℃ at a rate of 3℃ / min, then from 350℃ to 800℃ at a rate of 5℃ / min) for 3 h at 800℃. After cooling to room temperature in the furnace, the sample was removed, ground for 5 min, and Bi₂WO₆:x%Nd₂O₃ was obtained. 3+ ,y%Er 3+ ,z%Yb 3+ For the powder samples, the doping concentrations are all molar concentrations, where x = 0.5, y = 1.5, z = 0.5, and the corresponding raw material masses are Er2O3: 10.41 mg, Nd2O3: 3.03 mg, Yb2O3: 3.55 mg, Bi2O3: 1656.65 mg, and WO3: 834.6 mg.

[0048] Example 2

[0049] This embodiment provides a rare earth material. The preparation method of the rare earth material differs from that in Example 1 in that z = 1, corresponding to Yb2O3: 7.09 mg, Bi2O3: 1652.46 mg, while the mass of the remaining Er2O3, Nd2O3 and WO3 raw materials remains unchanged.

[0050] Example 3

[0051] This embodiment provides a rare earth material. The preparation method of the rare earth material differs from that in Embodiment 1 in that z = 3, corresponding to Yb2O3: 21.28 mg, Bi2O3: 1635.68 mg, while the mass of the remaining Er2O3, Nd2O3 and WO3 raw materials remains unchanged.

[0052] Example 4

[0053] This embodiment provides a rare earth material. The preparation method of the rare earth material differs from that in Example 1 in that z = 6, corresponding to Yb2O3: 42.56 mg, Bi2O3: 1610.52 mg, while the mass of the remaining Er2O3, Nd2O3 and WO3 raw materials remains unchanged.

[0054] Example 5

[0055] This embodiment provides a rare earth material. The preparation method of the rare earth material differs from that in Example 1 in that z = 9, corresponding to Yb2O3: 63.85 mg, Bi2O3: 1585.35 mg, while the mass of the remaining Er2O3, Nd2O3 and WO3 raw materials remains unchanged.

[0056] Example 6

[0057] This embodiment provides a rare earth material. The preparation method of the rare earth material differs from that in Example 1 in that x = 1, corresponding to Nd2O3: 6.06 mg, Bi2O3: 1652.46 mg, while the mass of the remaining Er2O3, Yb2O3 and WO3 raw materials remains unchanged.

[0058] Example 7

[0059] This embodiment provides a rare earth material. The preparation method of the rare earth material differs from that in Example 1 in that x = 3, corresponding to Nd2O3: 18.18 mg, Bi2O3: 1635.68 mg, while the mass of the remaining Er2O3, Yb2O3 and WO3 raw materials remains unchanged.

[0060] Comparative Example 1

[0061] This comparative example provides a rare earth material. The difference between the preparation method of the rare earth material and that of Example 1 is that the matrix material Bi2WO6 is replaced with LiGd(WO4)2.

[0062] Comparative Example 2

[0063] This comparative example provides a rare earth material. The difference between the preparation method of the rare earth material and that of Example 1 is that the matrix material Bi2WO6 is replaced with Bi4Ti3O. 12 .

[0064] Comparative Example 3

[0065] This comparative example provides a rare earth material. The difference between the preparation method of the rare earth material and that of Example 1 is that the matrix material Bi2WO6 is replaced with La3NdO4, Er 3+ Replace with Ho 3+ .

[0066] Comparative Example 4

[0067] This comparative example provides a rare earth material, the difference between the preparation method of the rare earth material and that of Comparative Example 3 is that Ho is used... 3+ Replace with Tm 3+ .

[0068] Comparative Example 5

[0069] This comparative example provides a rare earth material. The preparation method of the rare earth material differs from that of Example 1 in that the matrix material Bi2WO6 is replaced with GdVO4, and Nd is not added. 3+ .

[0070] Comparative Example 6

[0071] This comparative example provides a rare earth material. The difference between the preparation method of the rare earth material and that of Example 1 is that Bi2WO6 is replaced with NaYF4, Er 3+ Replace with Ho 3+ .

[0072] Comparative Example 7

[0073] This comparative example provides a rare earth material, the preparation method of which differs from that of Example 1 in that Er... 3+ Replace with Ho 3+ Nd 3+ Replace with Tm 3+ .

[0074] The X-ray diffraction patterns of the rare earth materials provided in Examples 1-5, 6, and 7 are as follows: Figure 1 As shown, Figure 1 (a) X-ray diffraction patterns of the rare earth materials provided in Examples 1, 6, and 7. Figure 1(b) X-ray diffraction patterns of the rare earth materials provided in Examples 2-5. The synthesized samples show good agreement with the diffraction peaks of the standard card (JCPDS39-0256) for Bi2WO6, and no other impurity peaks were found. This indicates that a certain amount of Nd... 3+ Er 3+ ,Yb 3+ Doping has virtually no effect on the orthorhombic crystal structure of Bi2WO6.

[0075] The emission spectra of the rare earth materials provided in Examples 1-4, 6, and 7 under 808 nm excitation are shown below. Figure 2 As shown, the emission of the sample is mainly caused by Er 3+ The emission peaks at 525nm, 546nm, and 654nm are composed of three emission peaks: the green emission near 525nm and 546nm is caused by Er. 3+ ( 2 H 11 / 2 → 4 I 15 / 2 / 4 S 3 / 2 → 4 I 15 / 2 The red emission near 654nm, generated by the Er transition, is due to Er 3+ ( 4 F 9 / 2 → 4 I 15 / 2 This is caused by a transition. The emission spectra of the rare earth materials provided in Examples 1, 6, and 7 are as follows: Figure 2 As shown in (a), with Nd 3+ With increasing doping concentration, Bi2WO6:x%Nd 3+ 1.5% Er 3+ 0.5% Yb 3+ The emission intensity of the samples (x = 0.5, 1, 3) continuously decreases, therefore the optimal Nd... 3+ The doping concentration is 0.5%. The emission spectra of the rare earth materials provided in Examples 2-4 are as follows: Figure 2 As shown in (b), under the same excitation conditions, Bi2WO6:0.5% Nd 3+ 1.5% Er 3+ ,z%Yb 3+ Emission spectra of samples (z = 1, 3, 6) Yb 3+ At a concentration of 3%, Er 3+ The emission intensity was highest at (525nm, 546nm, 654nm). The optimal doping concentration sample was ultimately determined to be Bi₂WO₆: 0.5% Nd. 3+ 1.5% Er 3+ 3% Yb 3+ .

[0076] Fluorescence detection of the samples was performed using an FLS920 full-function steady-state / transient fluorescence spectrometer from Edinburgh, UK, with an 808nm diode laser as the excitation source. Upconversion emission spectra were measured at different pump powers. To detect the upconversion luminescence of the samples at different temperatures, the samples were heated in the high-temperature heating device of the spectrometer (temperature control range from room temperature 298K to 573K). To avoid the thermal effect caused by the laser, a suitable low excitation power was used to excite the samples. 10mg, 20mg, and 60mg of the rare earth materials synthesized in Example 3 were mixed with 40mL of distilled water, ultrasonically dispersed, and allowed to settle for 24h to prepare suspensions with turbidities of 20, 60, and 100 NTU (turbidity units), respectively. These suspensions were added to quartz cuvettes, and the liquids were heated to 70°C. The fluorescence temperature sensing properties of the samples in the aqueous environment were tested by cooling the liquids.

[0077] The energy level transition diagrams of the rare earth materials provided in Examples 1-4, 6, and 7 under 808 nm excitation are shown below. Figure 3 As shown. Nd in the ground state 3+ Ions reach an excited state under the excitation of an 808nm laser. 4 F 5 / 2 Corresponding to the transition 4 I 9 / 2 → 4 F 5 / 2 . 4 F 5 / 2 Excited states are unstable; therefore some Nd... 3+ Ions rapidly relax to multiphonon nonradiative relaxation. 4 F 3 / 2 Because Nd 3+ Ions and Yb 3+ Energy transfer (ET) between ions occurs 2 F 7 / 2 (Yb 3+ )+ 4 F 3 / 2 (Nd 3+ → 2 F 5 / 2 (Yb 3+ )+ 4 I 11 / 2 (Nd 3+ Between them, and the energy transfer efficiency between them is very high. As a result, Yb 3+ Ionic 2 F 5 / 2 The state was filled. Subsequently, it was obtained twice from the stimulated Yb. 3+ Ions to Er 3+ The continuous energy transfer of ions causes Er 3+ Ions directly reach 4 F 7 / 2State. Partially in 4 F 7 / 2 state Er 3+ Ions relax to lower levels via multiphonon relaxation. 2 H 11 / 2 , 4 S 3 / 2 and 4 F 9 / 2 state; then 2 H 11 / 2 , 4 S 3 / 2 and 4 F 9 / 2 .at last 2 H 11 / 2 , 4 S 3 / 2 and 4 F 9 / 2 Electron transition from state to ground state 4 I 15 / 2 It emits green light (525nm, 546nm) and red light (654nm).

[0078] The temperature-varying upconversion emission spectrum of the rare earth material provided in Example 3 under 808 laser (464mW) excitation in the temperature range of 298-573K is shown below. Figure 4 As shown, the emission peaks at 525, 546, and 645 nm gradually decrease with increasing temperature. This is because lattice vibrations intensify during the heating process, the number of phonons increases, and the probability of nonradiative relaxation increases significantly, leading to weakened luminescence.

[0079] For Er 3+ The relationship between the three emission peaks and temperature was fitted using a polynomial to the fluorescence intensity ratio (FIR) versus temperature (NTCL-FIR), as shown in formula (1), where I1 and I2 are the fluorescence intensities of the two emission peaks, and A1, B1, B2, and B3 are undetermined coefficients. Absolute temperature sensitivity S a and relative temperature sensitivity S r It is an important parameter for the temperature sensing performance of materials. It allows us to obtain the absolute and relative temperature sensitivity (S) of a material. a and S r As shown in formulas (2) and (3).

[0080] FIR = I1 / I2 = A1 + B1T + B2T 2 +B3T 3 (1)

[0081]

[0082] Figure 5 Er in Example 3 3+The relationship between fluorescence intensity ratios at 525nm and 546nm, and 525nm and 654nm, and temperature. Figure 5 (a) is based on Er 3+ 525nm ( 2 H 11 / 2 → 4 I 15 / 2 ) and 546nm ( 4 S 3 / 2 → 4 I 15 / 2 The relationship between fluorescence intensity ratio and temperature. Figure 5 (b) is based on Er 3+ 525nm and 654nm ( 4 F 9 / 2 → 4 I 15 / 2 The fluorescence intensity ratio (FIR) versus temperature was calculated and fitted for Bi2WO6: the rare earth material provided in Example 3, at 525nm / 546nm and 525nm / 654nm, respectively:

[0083] FIR 525nm / 546nm =3.85145 - 0.335T + 9.8 × 10 -5 T 2 -8.4×10 -8 T 3 (4)

[0084] FIR 525nm / 654nm -7.58252+0.07T-1.6×10 -4 T 2 +1.24×10 -7 T 3 (5)

[0085] Based on the above fitting results, within a temperature range of 298K to 573K, the rare earth material provided in Example 3 was excited at 808nm (464mW) using I... 525nm / 546nm and I 525nm / 654nm The result of the temperature sensitivity change with temperature obtained by fluorescence intensity ratio is shown in the figure below. Figure 6 As shown, Figure 6 (a) is based on FIR 525nm / 546nm The graph shows the change in temperature sensitivity obtained from the fluorescence intensity ratio. Figure 6 (b) is based on FIR 525nm / 654nm The graph shows the change in temperature sensitivity obtained from fluorescence intensity ratio. (Using FIR) 525nm / 546nm The S of the powder sample was calculated. a The maximum value was 0.0046K at 398K. -1 S rAt 323K, it is 0.0081K. -1 Use FIR 525nm / 654nm S was calculated a It reaches a maximum value of 0.0047K at 423K. -1 S r It reaches a maximum value of 0.014K at 573K. -1 .

[0086] The upconversion emission spectra of the rare earth materials provided in Example 3 in an aqueous environment with suspensions of 20 NTU, 60 NTU, and 100 NTU under 808 nm (464 mW) laser excitation are shown below. Figure 7 As shown in the figure. The results indicate that the emission peaks and positions of samples with different turbidities did not change. Under the same excitation conditions, the suspension samples with higher turbidity exhibited stronger luminescence intensity in the aqueous environment. Within this turbidity range, the luminescence intensity was strongest when the turbidity of the sample was 100 NTU.

[0087] The temperature-dependent upconversion emission spectrum of the rare earth material provided in Example 3 for a 100 NTU sample excited in a water environment at 808 nm is shown below. Figure 8 As shown in the figure, the shape and position of the emission peak of the 100 NTU sample in the water environment remained unchanged as the temperature decreased, but the green emission at 525 nm and 545 nm and the red emission at 654 nm both weakened. When the temperature decreases, the number of electrons in the excited state decreases, the probability of radiative transitions decreases, and the emission weakens.

[0088] As the temperature decreases, Er in the 100 NTU sample... 3+ The changes in luminescence intensity at 546nm and 654nm are more pronounced, so FIR is selected here. 546nm / 645nm To fit the FIR at different temperatures, the graph of the fluorescence intensity ratio at 546 nm / 654 nm for a 100 NTU sample of rare earth material provided in Example 3 changing with temperature in an 808 nm excited water environment is shown in Figure 3. Figure 9 As shown, the relationship is:

[0089] FIR 546nm / 645nm = -4513.93 + 43.47T - 0.14T 2 +1.48×10 -4 T 3 (6)

[0090] Use FIR 546nm / 645nm The temperature was characterized, and the absolute thermometric sensitivity S of a 100 NTU sample in an aqueous environment was calculated when the temperature decreased from 323 K to 298 K. a Relative temperature sensitivity S r , Figure 10The rare earth material provided in Example 3 of this application was tested in an 808 nm excited water environment with a 100 NTU sample based on FIR. 525nm / 654nm The graph shows the change in temperature sensitivity as a function of temperature. At this point, S... a The maximum value obtained at 298K was 0.066K. -1 S r It reaches a maximum value of 0.115K at 298K. -1 .

[0091] The temperature sensing performance of the rare earth materials provided in Example 3 and Comparative Examples 1-7 is shown in Table 1.

[0092] Table 1

[0093]

[0094] Temperature resolution δT is one of the parameters for measuring temperature sensing characteristics. It refers to the ability of a temperature sensing material to detect the smallest temperature change, and its definition is as follows:

[0095]

[0096] Where Δ represents the fluorescence intensity ratio (FIR), δI represents the relative uncertainty of the fluorescence intensity ratio, δI corresponds to the fluctuation of the background of the luminescent center, and I represents the intensity of the corresponding emission peak.

[0097] according to Figure 8 The upconversion emission spectra of rare earth material samples at different temperatures (298K-573K) were obtained. The corresponding δI, FIR, and Sr values ​​were substituted into formulas (7) and (8) to calculate the temperature resolution of the rare earth material samples provided in Example 3 within the temperature range of 298K-573K, based on the fluorescence intensity ratios of 525nm / 546nm and 525nm / 654nm at the characterization temperatures. Figure 11 As shown in (a). Figure 11 (b) The temperature resolution of a 100 NTU sample in an aquatic environment was calculated when the temperature was reduced from 323 K to 298 K.

[0098] Figure 11 (a) Example 3 provides rare earth powder materials based on Er 3+ FIR 525nm / 546nm FIR 525nm / 654nm The temperature resolution as a function of temperature was plotted, and the minimum temperature resolution δT was calculated to be 0.54K (298K) and 1.52K (523K).

[0099] Figure 11 (b) is an FIR-based image of a 100 NTU sample in the aquatic environment. 546nm / 654nmThe temperature resolution varies with temperature; under the same excitation conditions, in the range of 323K-298K, using FIR... 546nm / 654nm Characterizing the temperature, the minimum temperature resolution δT was calculated to be 0.85 K (298 K).

[0100] Under 808nm excitation (excitation power 464W), based on the temperature-varying spectra of the rare earth powder material provided in Example 3 tested in air and water environments, the corresponding chromaticity coordinates and color temperatures were calculated as follows:

[0101] CIE (chromaticity) coordinates: standardized parameters used to describe color. Colors are located in a chromaticity diagram using two values ​​(x, y). Color temperature is a physical quantity calculated from the chromaticity coordinates and is used to represent the color temperature of a light source.

[0102] Based on the CIE1931 standard color perception model, using the measured variable temperature spectrum, the XYZ chromaticity coordinate system (X, Y, and Z are the three primary color components) is used, where the x and y values ​​represent the position of the color in the chromaticity diagram, and the Z value is calculated by the formula Z = 1 - (X + Y).

[0103] The results are shown in Table 2 and Figure 12 As shown, Figure 12 The image shows the temperature-varying chromaticity coordinates of a 100 NTU sample of rare earth material provided in Example 3 of this application under 808 nm excitation in air or water. (a) is in air, and (b) is in water.

[0104] Table 2

[0105]

[0106] Under 808nm excitation, 0.5% Nd 3+ 1.5% Er 3+ 3% Yb 3+ Co-doped Bi₂WO₆ was found to be the optimal luminescent sample. Excitation of this powder sample at 808 nm (47-464 mW) yielded Er₂O₆ levels in the sample. 3+ The emission peaks at 525nm, 546nm, and 654nm all originate from two-photon absorption. Using Er... 3+ FIR 525nm / 546nm Characterizing the temperature, the maximum relative temperature sensitivity of this powder sample was calculated to be 0.0081 K. -1 @323K. Using Er 3+ FIR 525nm / 654nm Characterizing the temperature, the maximum relative temperature sensitivity was calculated to be 0.014 K. -1@573K. Within this temperature range, the minimum temperature resolutions obtained by the two methods are 0.54K (298K) and 1.52K (523K), respectively. With the excitation conditions unchanged, a 100 NTU sample in an aqueous environment was analyzed using FIR. 525nm / 654nm Characterizing the temperature, the maximum relative temperature sensitivity was found to be 0.115 K. -1 @298K, with a minimum temperature resolution of 0.85K (298K). Studies have shown that the prepared rare earth materials have potential applications in temperature sensing and thermochromic anti-counterfeiting in aqueous environments.

[0107] The above description is merely a preferred embodiment of this application, but the scope of protection of this application is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in this application, based on the technical solution and application concept of this application, should be included within the scope of protection of this application.

Claims

1. A rare earth material, characterized in that, The stoichiometric formula of the rare earth material is Bi2WO6:mA 3+ , where 0.005≤m≤0.1, and A represents Nd, Er, and Yb.

2. The rare earth material according to claim 1, characterized in that, 0.005≤m≤0.09, B represents Nd, Er, and Yb.

3. The rare earth material according to claim 1, characterized in that, The stoichiometric formula of the rare earth material is Bi2WO6:x%Nd. 3+ y%Er 3+ ,z%Yb 3+ , where 0.5≤x≤3, y=1.5, 0.5≤z≤9.

4. The rare earth material according to claim 1, characterized in that, The stoichiometric formula of the rare earth material is Bi₂WO₆: 0.5%Nd. 3+ 1.5% Er 3+ 3% Yb 3+ .

5. The rare earth material according to claim 1, characterized in that, The particle size of the rare earth material is 1 μm to 5 μm.

6. A method for preparing a rare earth material, characterized in that, include: Bismuth oxide, tungsten oxide and rare earth oxides are mixed and calcined to obtain rare earth materials; The rare earth oxides include Er2O3, Yb2O3 and Nd2O3.

7. The preparation method according to claim 6, characterized in that, The calcination temperature is 350°C to 800°C; the calcination time is 3 hours to 5 hours.

8. The preparation method according to claim 6, characterized in that, The mixture of bismuth oxide, tungsten oxide and rare earth oxide is ground and then calcined. The grinding time is 20 to 30 minutes. After calcination, the mixture is cooled to room temperature.

9. A method for measuring temperature in a water environment, characterized in that, include: The emission spectra of rare earth materials and water suspensions at different temperatures were collected under near-infrared excitation light source. The emission peaks of thermally coupled or non-thermally coupled energy level pairs were selected. The fluorescence intensity ratio of the two emission peaks was used to calculate the relationship between the fluorescence intensity ratio and temperature. The temperature was determined based on the fluorescence intensity ratio-temperature curve. The rare earth material is the rare earth material as described in any one of claims 1 to 5 or the rare earth material prepared by the preparation method as described in any one of claims 6 to 8.

10. The method according to claim 9, characterized in that, The wavelength of the near-infrared excitation source is 808 nm.

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