Cr < 3 + >-doped scandium tungstate for heat-quenching-resistant up-conversion luminescence and application thereof

Abstract

The chemical composition of the Cr < 3 + > doped scandium tungstate SWO: Yb / Cr is Sc2 (WO4) 3: x% Yb < 3 + > / y% Cr < 3 + >, x is greater than or equal to 20 and greater than or equal to 1, y is greater than or equal to 0.1 and greater than or equal to 10, Yb < 3 + > is a sensitizer ion, and Cr < 3 + > is an activator ion. The Cr < 3 + > doped scandium tungstate SWO: Yb / Cr is applied to construct a ratio type fluorescence temperature sensor, and tests show that the relative sensitivity of the fluorescence temperature sensing of the ratio type fluorescence temperature sensor constructed by the invention reaches 4% K <-1 >, the absolute sensitivity reaches 7.4% K <-1 >, and the temperature measurement range is 300-440K.

Description

Technical Field

[0001] The present invention relates to the field of luminescent materials and fluorescence sensing technology, and in particular to a Cr 3+ Doped scandium tungstate and its applications. Background Art

[0002] Cr 3+ It has many excellent optical properties, including wide emission wavelength range, long fluorescence lifetime, and high quantum efficiency. 3+ The optical properties of Cr are affected by the local chemical environment, temperature, applied pressure or stress, external electric field and magnetic field. In addition, the matrix material, doping concentration and preparation process will affect the 3+ Based on these special properties, Cr 3+ Doped fluorescent materials are widely used in solid-state lasers, photocatalysis, solar cells, long afterglow luminescent materials and optical sensors, especially Cr 3+ Down-shifted near-infrared luminescent materials as activators have become the focus of scientific researchers in recent years and have been widely studied and applied in many fields such as night vision and lossless imaging. 3+ / Cr 3+ Cr co-doped phosphor 3+ Ion upconversion luminescence is generally achieved through Yb 3+ The synergistic sensitization energy transfer process of ions is realized, and its excitation and emission wavelengths are both in the near-infrared band. It has the advantages of low background noise and high biological tissue penetration, and has excellent application prospects in the fields of optical sensing and deep tissue imaging.

[0003] Therefore, the new Cr 3+ The development and application of doped luminescent materials are of great research significance. However, like other types of luminescent materials, Cr 3+ Luminescence is also affected by thermal quenching of fluorescence, that is, the luminescence intensity decreases as the temperature increases. From the perspective of the design and application of fluorescent materials, the ability of fluorescent materials to resist thermal quenching is one of the key factors in evaluating their performance and is an important factor in determining their application prospects and applicability. 3+ The thermal quenching of luminescence seriously limits its research and application in high-power LEDs and some high-temperature environments. Therefore, it is urgent to develop Cr with good anti-thermal quenching performance. 3+ Although researchers have reported in the past that various methods such as matrix structure rigidity enhancement, band gap regulation, trap assistance, ion co-doping and multi-site occupancy can be used to improve Cr 3+ However, the thermal stability of fluorescence achieved by the above methods is still very limited, and they all focus on Cr 3+ The down-shifted luminescence of Cr3+ Research on upconversion luminescence resistant to thermal quenching.

[0004] Therefore, the prior art has defects and needs to be improved. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a Cr 2+ luminescent material which is resistant to thermal quenching upconversion luminescence in view of the shortcomings of the prior art. 3+ Doped scandium tungstate and its application to solve the problem of Cr in the prior art 3+ The luminescence performance of doped phosphors is limited by thermal quenching resistance and Cr 3+ The problem of the lack of up-conversion luminescence performance of the doped phosphor is that the phosphor is resistant to thermal quenching. 3+ Scandium tungstate doped material is a Sc2(WO4)3(SWO)-based luminescent system that resists thermal quenching. It utilizes the energy reservoir in the matrix material to compensate the energy of the activator ions and realizes the Yb 3+ The heat-resistant luminescence of Yb 3+ -Cr 3+ The synergistic sensitized energy transfer of Cr 3+ The upconversion luminescence of the nanostructured carbon nanotubes was resistant to thermal quenching, and based on this, the optical application of fluorescence temperature sensing was developed.

[0006] The technical solution of the present invention is as follows:

[0007] A Cr-based upconversion luminescent material with resistance to thermal quenching 3+ Doped Scandium Tungstate, Cr 3+ The chemical composition of scandium tungstate doped SWO:Yb / Cr is: Sc2(WO4)3:x%Yb 3+ / y%Cr 3+ , where 20≥x≥1, 0.1≥y≥10, where Yb 3+ is the sensitizer ion, Cr 3+ is the activator ion.

[0008] The Cr luminescent material with resistance to thermal quenching upconversion 3+ Doped with scandium tungstate, x=8, y=0.1.

[0009] The Cr 3+ Application of scandium tungstate-doped nanostructured luminescence in thermally quenched upconversion luminescence.

[0010] The Cr 3+ Application of scandium tungstate-doped materials in fluorescence temperature sensing.

[0011] In the application, SWO:Yb / Cr phosphor and SWO:Er phosphor are mixed to prepare composite phosphor; the anti-thermal quenching upconversion luminescence of SWO:Yb / Cr at 700-800nm ​​and the thermal quenching upconversion luminescence of SWO:Er at 510-570nm have opposite intensity variation trends as the temperature rises; the intensity ratio of the two is selected as the temperature sensitive parameter to construct a ratio-type fluorescence temperature sensing application.

[0012] The anti-thermal quenching upconversion luminescence: During the solid-phase sintering process of the sample, some intrinsic WO4 groups in the SWO matrix will be twisted into the lattice gap to form non-intrinsic WO4 groups. The energy level coupling of the intrinsic and non-intrinsic WO4 groups plays the role of an energy storage pool. Under 976nm excitation, Yb 3+ The ions absorb the excitation light energy and transfer it to the energy storage tank. After the energy storage tank absorbs and stores the energy, it continuously compensates the energy to the doped Yb 3+ ions, making Yb 3+ ions have the ability to resist thermal quenching. 3+ Ions pass through Yb 3+ -Cr 3+ Synergistically sensitize the energy transfer process, continuously compensating energy to Cr 3+ ions, achieving Cr 3+ Thermal quenching-resistant upconversion luminescence.

[0013] The application of the ratiometric fluorescence temperature sensor, the test shows that the relative sensitivity of the fluorescence temperature sensor of the ratiometric fluorescence temperature sensor constructed by the present invention reaches 4%K -1 , absolute sensitivity reaches 7.4%K -1 , the temperature measurement range is 300-440K. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 : X-ray diffraction data of SWO:8%Yb / 0.1%Cr.

[0015] Figure 2 : Scanning electron microscope and elemental analysis of SWO:8%Yb / 0.1%Cr.

[0016] Figure 3 :Up-conversion luminescence spectrum of SWO:8%Yb / 0.1%Cr under 980nm excitation.

[0017] Figure 4 : Double logarithmic coordinate diagram of the luminescence intensity of SWO:8%Yb / 0.1%Cr varying with pump power.

[0018] Figure 5 :Yb 3+ -Cr 3+Two-photon upconversion luminescence process.

[0019] Figure 6 :Variable temperature near-infrared luminescence spectrum of SWO:8%Yb.

[0020] Figure 7 :SWO: 8% Yb / 0.1% Cr in Yb 3+ Temperature-dependent near-infrared luminescence spectrum.

[0021] Figure 8 :SWO:8%Yb / 0.1%Cr 3+ Temperature-dependent upconversion luminescence spectrum.

[0022] Fig. 9 :Temperature-dependent upconversion luminescence spectra of SWO:2%Er & SWO:8%Yb / 0.1%Cr composites

[0023] Fig.10 : Fluorescence intensity ratio I Cr / I Er (FIR) variation trend with temperature.

[0024] Fig.11 : Absolute sensitivity of ratiometric fluorescence thermometer.

[0025] Fig.12 : Relative sensitivity of ratiometric fluorescence thermometer. DETAILED DESCRIPTION

[0026] The present invention is described in detail below in conjunction with specific embodiments.

[0027] Example 1: Preparation of SWO:Yb / Cr (8 / 0.1 mol%)

[0028] First, based on a specific stoichiometric ratio, weigh Sc2O3 (0.919mmol), Yb2O3 (0.08mmol), Cr2O3 (0.001mmol) and WO3 (3mmol). Next, pour these raw materials into an agate mortar, mix and grind them for 30 minutes in a dry state, add ethanol and continue grinding for 30 minutes until all the ethanol evaporates to ensure that the various raw materials are fully mixed. Then, transfer the mixed powder to an alumina crucible and place it in a muffle furnace, heat it to 800℃ at a rate of 5℃ per minute for about 160 minutes, and then heat it to 1100℃ at a rate of 3℃ per minute for about 100 minutes, and keep it at 1100℃ for 6 hours. After the reaction is completed, take out the sample, cool it to room temperature, and then grind it again for 30 minutes to obtain a fine and uniform fluorescent powder. Finally, collect the powder in a 5ml small centrifuge tube for subsequent use.

[0029] The performance of the samples was tested and characterized using X-ray diffractometer, scanning electron microscope, Edinburgh FLS1000 instrument and Oxford DN2 variable temperature device. XRD data ( Figure 1 ), SEM images and EDS element scans ( Figure 2 ) all indicate that Cr 3+ Successfully doped into the SWO lattice.

[0030] Example 2Cr 3+ Characterization of upconversion luminescence performance

[0031] In order to characterize the upconversion luminescence performance of SWO:Yb / Cr, the luminescence spectrum of SWO:Yb / Cr was tested under 976nm excitation. As expected, under 976nm excitation light, Yb 3+ will absorb a near-infrared photon to reach an excited state, and then two Yb 3+ ions can simultaneously transfer energy to Cr 3+ ions, namely the cooperative sensitization energy transfer process, making Cr 3+ After reaching the excited state, it emits a broad peak upconversion luminescence at 750nm ( Figure 3 ). In order to further study the upconversion luminescence mechanism of SWO:Yb / Cr, the power dependence of upconversion luminescence under 976nm laser excitation was studied in detail. The emission intensity increases with the increase of excitation power. The slope of the variation of the near-infrared emission intensity of the sample with the pump power is about 1.8 after linear fitting. Figure 4 ), confirming the above Yb 3+ -Cr 3+ Two-photon cooperative sensitized upconversion luminescence process ( Figure 5 ).

[0032] Example 3 Characterization of the thermal quenching resistance upconversion luminescence performance of SWO:Yb / Cr

[0033] In order to characterize the anti-thermal quenching upconversion luminescence performance of SWO:Yb / Cr, the temperature-dependent upconversion luminescence spectra of SWO:Yb and SWO:Yb / Cr were tested respectively, and the test temperature range was 300-500K. Under 976nm excitation, as the test temperature continued to increase, the luminescence intensity of SWO:Yb continued to increase ( Figure 6 ). When co-doped with Cr 3+ After ionization, Yb 3+ The fluorescence thermal enhancement effect is significantly suppressed ( Figure 7 ), prove that Yb 3+ Continuously transfer energy to Cr 3+ ions. Therefore, the Cr 3+ The thermal quenching-resistant upconversion luminescence of Cr 3+The luminous intensity increases with the temperature, and the enhancement factor reaches 16 times at 460K ( Figure 8 ).

[0034] Example 4 Ratio-type fluorescence temperature sensor based on SWO:Yb / Cr & SWO:Er composite materials

[0035] Taking advantage of the fact that the upconversion luminescence intensity of SWO:Yb / Cr (8 / 0.1 mol%) increases with increasing temperature, a ratiometric fluorescence temperature sensing application can be designed. 3+ It is easier to measure temperature by changing the integral intensity of a single fluorescence peak with temperature. However, the luminescence intensity of fluorescent materials will also be affected by various factors such as the external environment, instrument and human operation errors, and the structure and composition of the material itself may also change slightly. Therefore, we physically mixed SWO:2%Er phosphor and SWO:8%Yb / 0.1%Cr phosphor in a mass ratio of 2:1 to prepare a composite material. Under 976nm laser excitation, as the temperature continues to rise, the Cr in the composite material 3+ The upconversion luminescence intensity (I Cr ) increases with increasing temperature, while Er 3+ The green light intensity (I Er ) is gradually weakening ( Fig. 9 ). By monitoring the fluorescence intensity ratio of the composite material in the temperature range of 300-440K Cr / I Er (FIR)( Fig.10 ), realizing ratiometric fluorescence temperature sensing. The relative sensitivity of fluorescence temperature sensing reaches 4%K -1 ( Fig.11 ), the absolute sensitivity reaches 7.4%K -1 ( Fig.12 ).

[0036] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all these improvements and changes should fall within the scope of protection of the appended claims of the present invention.

Claims

1. A Cr-based upconversion luminescent material with resistance to thermal quenching 3+ Doped scandium tungstate, characterized in that Cr 3+ The chemical composition of scandium tungstate doped SWO:Yb / Cr is: Sc2(WO4)3:x%Yb 3+ / y%Cr 3+ , where 20≥x≥1, 0.1≥y≥10, where Yb 3+ is the sensitizer ion, Cr 3+ is the activator ion.

2. The Cr-based luminescent material with thermal quenching resistance according to claim 1 3+ Doped scandium tungstate, characterized in that x=8, y=0.

1.

3. The Cr according to claim 1 or 2 3+ Application of scandium tungstate-doped nanostructured luminescence in thermally quenched upconversion luminescence.

4. The Cr according to claim 1 or 2 3+ Application of scandium tungstate-doped materials in fluorescence temperature sensing.

5. The use according to claim 4, characterized in that: SWO:Yb / Cr phosphor and SWO:Er phosphor were mixed to prepare composite phosphor. The anti-thermal quenching upconversion luminescence of SWO:Yb / Cr at 700-800nm ​​and the thermal quenching upconversion luminescence of SWO:Er at 510-570nm had opposite intensity variation trends as the temperature increased. The intensity ratio of the two was selected as the temperature sensitive parameter, and a ratiometric fluorescence temperature sensing application was constructed.

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