METAL-ORGANIC HYBRID LATTICE MATERIAL AND USE THEREOF IN DETECTION OF RADIATION SOURCES

Abstract

The present invention relates to a metal-organic hybrid lattice material and the application in the detection of radiation sources. In the invention, a water-soluble thorium salt and 2,2′:6′,2′-terpyridine-4′-carboxylic acid are subjected to a solvothermal reaction in water and an organic mixed solvent to obtain a metal-organic hybrid lattice material. The crystalline material produces radiation-induced discoloration and photoluminescence change under ultraviolet light, X-ray, γ-ray, β-ray, and so on. The material is useful for qualitative and quantitative detection and calibration after high-dose irradiation. Compared with the traditional radiation-induced color change indicator labels, the material achieves the visual qualitative and quantitative detection and has strong radiation stability, high reuse rate, wide detection range, and good linear relationship, to solve the problem of traditional materials relying on professional optical equipment to quantify the radiation dose.

Claims

1. A method for preparing a metal-organic hybrid lattice material, comprising the following steps: subjecting a water-soluble thorium salt and 2,2′:6′,2″-terpyridine-4′-carboxylic acid to a solvothermal reaction in a mixed solvent of water and an organic solvent at 80-120° C., to obtain a crystal comprising the metal-organic hybrid lattice material after complete reaction, wherein the mixed solvent also comprises 1.6-2.5 wt % of hydrochloric acid, and the molar ratio of the water-soluble thorium salt to 2,2′:6′,2″-terpyridine-4′-carboxylic acid is 1-2: 1-2.

2. The method according to claim 1, wherein the water-soluble thorium salt is thorium nitrate.

3. A metal-organic hybrid lattice material prepared by the method according to claim 1, having a chemical formula of [Th.sub.6O.sub.4(OH).sub.4(H.sub.2O).sub.6](H.sub.10C.sub.16N.sub.3O.sub.2).sub.8(COOH).sub.4.

4. Use of the metal-organic hybrid lattice material according to claim 3 in the detection of radiation sources including ultraviolet light and/or ionizing radiation beams.

5. The application according to claim 4, wherein the wavelength of ultraviolet light is 400 nm-10 nm, and the photon energy is 3.10-124 eV.

6. The application according to claim 4, wherein the ionizing radiation beams include one or more of X-ray, γ-ray, and β-ray.

7. The application according to claim 6, wherein in qualitative detection, the detectable dose of X-ray is greater than 200 kGy, in quantitative detection, the detectable range for the dose of γ-ray is below 80 kGy, and in qualitative detection, the detectable dose of β-ray is greater than 200 kGy.

8. A method for detecting a radiation source, the radiation source including ultraviolet light and/or ionizing irradiation beams, the method comprising a step of establishing a detection standard and a detection step, wherein the step of establishing a detection standard comprises irradiating the metal-organic hybrid lattice material according to claim 3 with a radiation source of known wavelength or intensity, and establishing a detection standard according to the color change or the change of the optical signal intensity of the metal-organic hybrid lattice material before and after irradiation; the detection step comprises irradiating the metal-organic hybrid lattice material with a radiation source of unknown wavelength or intensity, and comparing the color change or the change of the optical signal intensity of the metal-organic hybrid lattice material before and after irradiation with the detection standard, and qualitatively or quantitatively analyzing the radiation source of unknown wavelength or intensity.

9. Use of the metal-organic hybrid lattice material according to claim 3 in the preparation of a photoluminescence change indicator label, wherein the photoluminescence change indicator label comprises at least one transparent quartz container and the metal-organic hybrid lattice material encapsulated in the quartz container.

10. A photoluminescence change indicator label, comprising at least one transparent quartz container and the metal-organic hybrid lattice material according to claim 3 encapsulated in the quartz container.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0055] FIG. 1 is a schematic diagram showing the structure of a crystal material prepared in Example 1 of the present invention;

[0056] FIG. 2 is a powder diffraction pattern of the crystal material tested before and after irradiation in Example 1 of the present invention;

[0057] FIG. 3 is a thermogravimetric analysis (TGA) curve of the crystal material tested in Example 2 of the present invention;

[0058] FIG. 4 shows the results of the photoluminescence stability test of the crystal material tested after irradiation in Example 3 of the present invention;

[0059] FIG. 5 shows the radiation detection device designed and the cyclic radiation-induced fluorescence in Example 4 of the present invention;

[0060] FIG. 6 shows the free radical signals from the crystal tested before and after irradiation with UV light in Example 4 of the present invention;

[0061] FIG. 7 shows the color change of the crystal under irradiation by various radiation sources in Example 5 of the present invention;

[0062] FIG. 8 shows the photoluminescence of the crystal tested before and after irradiation with β-ray at 200 kGy in Example 6 of the present invention;

[0063] FIG. 9 shows the photoluminescence of the crystal tested before and after irradiation with γ-ray at 200 kGy in Example 6 of the present invention;

[0064] FIG. 10 shows the photoluminescence of the crystal tested before and after irradiation with X-ray at 200 kGy in Example 6 of the present invention;

[0065] FIG. 11 shows the radiation-induced photoluminescence indicator label after irradiation with various doses of γ-ray and quantification of the dose by linear fitting in Example 7 of the present invention;

[0066] FIG. 12 is a schematic diagram showing the radiation detection in an X-ray radiation field of BL14W1 beamline of Shanghai Synchrotron Radiation Facility in Example 8 of the present invention;

[0067] FIG. 13 shows the ultraviolet-visible absorption by the crystal tested after irradiation with various energy of UV light in Example 9 of the present invention;

[0068] FIG. 14 shows photoluminescence images of the crystal tested after irradiation with various energy of UV in Example 9 of the present invention;

[0069] FIG. 15 shows the photoluminescence spectra tested after irradiation with various energy of UV in Example 9 of the present invention;

[0070] FIG. 16 is a CIE diagram tested after irradiation with various energy of UV in Example 9 of the present invention;

[0071] FIG. 17 shows the linear relationship between the dose and the intensity of the spectral characteristic peak tested after irradiation with various energy of UV in Example 9 of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0072] The specific embodiments of the present invention will be described in further detail with reference to embodiments. The following embodiments are intended to illustrate the present invention, instead of limiting the scope of the present invention.

Example 1. Material Synthesis and Test of Structural Stability Before and After Irradiation

[0073] In this example, the material was synthesized and the stability of the crystal structure was tested under various irradiation conditions to verify that the material of the present invention can be practically used in various large-dose irradiation conditions without radiation damage to the material.

[0074] 0.05 mmol of solid Th(NO.sub.3).sub.4.6H.sub.2O, 0.05 mmol of solid 2,2′:6′,2″-terpyridine-4′-carboxylic acid, and 1.6-2.5 wt % hydrochloric acid, 1 mL of H.sub.2O, and 1 mL of DMF were added to a 5 ml glass vial, sealed, heated to 100° C., and reacted for 1-2 days under heating. After the reaction, a transparent bulk crystal product was obtained. The crystal product was taken out of the vial and washed with ethanol, and then air dried at room temperature, to obtain a metal-organic hybrid lattice material, which was hereinafter referred to as crystal material. The reaction route is as follows:

##STR00001##

[0075] FIG. 1 is a schematic diagram showing the structure of the crystal material. The crystal is composed of 0-dimensional cluster structures. The tetravalent thorium ions form a hexanuclear thorium cluster center [Th.sub.6(OH).sub.4(O).sub.4(H.sub.2O).sub.6].sup.12+ through hydrolysis and polymerization, in which the thorium ions are linked by O.sup.2− and OH.sup.−. The hexanuclear thorium cluster center is further modified and attached with eight 2,2′:6′,2″-terpyridine-4′-carboxylic acid ligands and four carboxylic acid anions. The 0-dimensional clusters are periodically alternately arranged such that a strong π-π interaction is formed between pyridine rings.

[0076] After the crystal material was obtained following the above method, the material was respectively irradiated with exciting UV light at 254 nm for more than 2 h, γ-ray from a Co.sup.60 radiation source at a dose of 200 kGy, or β-ray generated by an electron accelerator at a dose of 200 kGy.

[0077] The crystal before and after irradiation was characterized by a powder diffractometer, as shown in FIG. 2. In FIG. 2, the Simulated curve is a pattern of the structure of the [Th.sub.6O.sub.4(OH).sub.4 (H.sub.2O).sub.6](H.sub.10C.sub.16N.sub.3O.sub.2).sub.8(HCOO).sub.4 crystal powder simulated by software, the As synthesized curve represents the powder diffraction pattern of the crystal material before irradiation, UV, γ-ray, and β-ray represents the powder diffraction patterns obtained after the crystal material is irradiated by the corresponding rays. In the figure, their main characteristic peak profiles are the same, which objectively shows that the purity of the synthesized crystal is very high and the crystal morphology is kept unchanged after irradiation. Therefore, the crystal material is useful in the research of radiation detection materials.

Example 2. Thermogravimetric Analysis of Crystal Material

[0078] In this example, the synthesized crystal material was tested for thermal stability to verify the heat resistance of the material of the present invention. Therefore, the fluorescence signal value could be restored by heating at an appropriate temperature, to enable the material to be recycled.

[0079] The crystal produced in Example 1 was characterized by a thermogravimetric analyzer. As shown in FIG. 3, the result shows that the skeleton of the crystal material does not collapse before 150° C., ensuring the stability of the structure; and only the water and DMF molecules in the structure of the crystal material are lost before 150° C. (3.55% weight loss). The weight loss of 9.70% before 300° C. is attributed to the free water, DMF, coordinated water molecules, and carboxylic acid in the structure. Therefore, it is possible to find a suitable temperature before 150° C. to restore the fluorescence signal intensity of the crystal material without causing the structure to be destroyed.

Example 3. Fluorescence Stability after Irradiation

[0080] In this example, the crystal material was irradiated under UV to verify that the fluorescence signal of the material of the present invention after irradiation can be stable for a long time at room temperature. The quantitative detection limit of UV light is 4.21 mJ, when it exceeds 4.21 mJ, the fluorescence will reach saturation and the fluorescence signal will not change. Therefore, the energy that exceeds the quantitative detection limit is used for the stability test.

[0081] The crystal material prepared in Example 1 was irradiated under UV at 254 nm (5.26 mJ) for 2 h or more, stored in a dark chamber, and tested for luminescence stability at different time within two days.

[0082] The fluorescence signal of the crystal was characterized by a solid-state spectrometer (FIG. 4). FIGS. 4a and b respectively show the test results of the fluorescence signal intensity of the crystal material under UV light at different times and the relationship between the fluorescence signal intensity and the irradiation time. FIG. 4 shows that the fluorescence signal of the crystal material changes after UV irradiation, resulting in radiation-induced photoluminescence change, and the fluorescence signal has no obvious change within two days (except for the pre-irradiation curve, other curves are basically overlapped in FIG. 4a), suggesting that the fluorescence stability of the material after irradiation is very good, and will not deteriorate or change over time.

Example 4. Design of Packaged Radiation Detection Device and Test of Reuse Rate

[0083] In this example, the material in a packaged device was irradiated and then heated to restore the fluorescence signal. The operations were repeated several times to verify the practicability and reuse rate of the material of the present invention.

[0084] The crystal material prepared in Example 1 was ground into a powder, compacted, and fed to a notch of a single-side notched quartz sheet (where the single-side notched quartz sheet has a size of 2.5 cm×2.5 cm and a thickness of 0.2 cm, a notch is provided at the center of the single-side notched quartz sheet, and the notch has a size of 0.5 cm×0.5 cm, and a depth of 0.1 cm), the notch was sealed with a quartz sheet has a thickness of 0.1 cm, and the four sides of the quartz sheet were fixed and sealed to prepare a radiation detection device.

[0085] The fluorescence signal intensity of the crystal material before irradiation was tested. The radiation detection device was irradiated under UV at 254 nm for more than 2 h, and then the fluorescence signal intensity of the crystal material in the radiation detection device was tested. After the test, the radiation detection device was heated at 120° C. for 1 day, and then the fluorescence signal intensity of the crystal material in the radiation detection device was tested. These operations were one cycle, and five cycles of operations were performed. A schematic diagram of one of the cycles is shown in FIGS. 5a-c.

[0086] The photoluminescence signal intensity of the material was characterized by a solid-state spectrometer (FIG. 5d). With the same instrument parameters, a fluorescence spectrum of the crystal material was obtained. The signal intensities of the fluorescence emission peaks at 532 nm were compared. By using the results of the five rounds of tests, the intensities were fitted and plotted. The result is shown in FIG. 5d. The result shows that the fluorescence intensity of the crystal material prepared in the present invention is restored after heating, proving that the material can be cyclically used in the detection of high-dose radiation.

[0087] FIG. 6 shows the difference of the free radical signals before and after the crystal material is irradiated with UV at 254 nm, indicating that the irradiation causes the production of a free radical signal by the ligand, and the presence of the free radical signal changes the characteristic peak of the fluorescence signal, resulting in radiation-induced color change and radiation-induced photoluminescence change.

Example 5. Visualized Qualitative Detection of Radiation-Induced Color Change

[0088] In this example, individual crystal materials were irradiated with various rays. The color change of the crystal before and after irradiation was compared by naked eyes to verify that the radiation-induced color change of the material of the present invention is useful for the visualized qualitative detection of rays.

[0089] Four original crystal samples were imaged under a microscopic imaging system, and then irradiated with UV at 254 nm for 2 h, and γ-, β-, and X-ray at a dose of 200 kGy, 200 kGy, and 200 kGy respectively. Next, each of the crystal samples was imaged under the microscopic imaging system. The results are shown in FIG. 7. FIG. 7 shows that the crystal changes from white-pink to yellow after UV light and X-ray irradiation, and the crystal changes from pink to yellow-brown after γ- and β-ray irradiation.

Example 6. Visualized Qualitative Detection of Photoluminescence Change

[0090] In this example, individual crystal materials were irradiated with various rays. The photoluminescence change of the crystal before and after irradiation was compared to verify that the radiation-induced photoluminescence change of the material of the present invention is useful for the visualized qualitative detection of rays.

[0091] The photoluminescence spectra of four original crystal samples were obtained and then the samples were irradiated with γ-, β-, and X-rays at a dose of 200 kGy, 200 kGy, and 200 kGy respectively. Then the photoluminescence spectrum of each crystal after irradiation was obtained. A merged photoluminescence spectrum was drawn, and the fluorescence change was read from the merged spectrum. The photoluminescence signal spectrum was tested by a solid-state spectrometer (FIG. 8-10), where the UV excitation wavelength is 365 nm. FIGS. 8-10 shows that the emission peak of the crystal is at 432 nm before β-, γ-, and X-ray irradiation, and the peak position of the emission peak changes from 432 to 532 nm after irradiation, indicating that the crystal material has visible fluorescence changes after irradiation.

[0092] In addition to drawing a merged photoluminescence spectrum and reading the fluorescence change from the merged spectrum, the crystal material can also be excited by a handheld fluorescent lamp and then the change in fluorescent color of the material is visually observed.

Example 7. Design of γ-Ray Radiation-Induced Photoluminescence Quantitative Indicator Label

[0093] In this example, the crystal sample was irradiated with γ-ray, and a radiation-induced photoluminescence quantitative indicator label was simulated by a radiation detection device designed in the present invention, to verify the method visually quantifying the radiation dose and effect thereof in the present invention.

[0094] According to the method in Example 4, the crystal material prepared in Example 1 was respectively packaged in a single-side notched quartz sheet provided with multiple notches, such as 3×3 notches, to complete the preparation of a radiation-induced photoluminescence quantitative indicator label (FIG. 11a). The photoluminescence images at various doses of γ-rays are shown in FIG. 11b.

[0095] In addition, a quartz sheet with more notches can be designed, to design a standard radiation detection device. The packaged standard radiation detection device was tested by irradiating the samples with γ-rays from a Co.sup.60 radiation source at a dose of 1 kGy, 3 kGy, 5 kGy, 7 kGy, 10 kGy, 30 kGy, 50 kGy, 80 kGy, 100 kGy, and 200 kGy respectively. The samples in the irradiated devices were excited in the ZF-II UV analyzer under UV light at 365 nm, and a photoluminescence image of the samples after irradiation was taken by ordinary photographic equipment in a dark chamber, that is, a standard radiation-induced photoluminescence indicator label. The fluorescent color of an irradiated material was visually observed with naked eyes and compared with the radiation-induced photoluminescence indicator label photographed in the experiment, to semi-quantitatively determine the radiation dose received by the material (FIG. 11c).

[0096] The color was extracted from the photographed radiation-induced photoluminescence indicator label and analyzed by the color extraction function in photoshop and other image processing software (FIG. 11D). The color rendering index of the fluorescent color in the image was read, and the color rendering index of green in the three primary colors was linearly fitted to the radiation dose, to obtain the linear relationship between the dose and the color rendering index (FIG. 11e). After that, a sample irradiated at an unknown dose was imaged under the same imaging conditions, and the color in the image was extracted by the same software. The green rendering index was read, and interpolated in the fitted linear relationship, to quantitatively read the radiation dose of the material.

[0097] In the present invention, the detectable range of the radiation dose of γ-ray is 0-80 kGy. After irradiation at a dose above 80 kGy, the color rendering indexes of green, red, and blue in the three primary colors tend to be stable, so the radiation dose cannot be read from the standard radiation-induced photoluminescence indicator label by comparing the colors. FIG. 11 shows that a linear relationship between the dose and the green rendering index is fitted in the dose range of 0-10 kGy (FIG. 11f), and another linear relationship between the dose and the green rendering index is fitted in the dose range of 10-80 kGy (FIG. 11G). Therefore, by using the fluorescent color of the irradiated material of the present invention in combination with the two linear relationships, the radiation dose of γ-rays in the range of 0-80 kGy can be accurately quantified.

Example 8. Use of X-Ray Radiation-Induced Photoluminescence Quantitative Indicator Label

[0098] In this example, the sample material was irradiated with a beam of X-rays, and the position of the beam of X-rays was determined by obvious photoluminescence change and the color change of the material to verify the ability and effect of the present invention in the qualitative detection of high-dose X-rays.

[0099] The crystal material was positioned in the center of a sample platform in an ionization chamber of BL14W1 beamline of Shanghai Synchrotron Radiation Facility, the line path of the light source was adjusted, and the crystal material was irradiated by X-rays. The color of the crystal material appeared yellow at the irradiated position (FIG. 12a). The irradiated area was irradiated with UV light of 365 nm from a flashlight and emitted a green fluorescence signal, proving that the crystal in this area has radiation-induced photoluminescence change. The crystal material of the present invention is used in a standard color change indicator label paper, and can be used to calibrate the emission position of the light source. Compared with the commercial radiation-induced color change indicator label paper (FIG. 12B) in the beamline of Shanghai Synchrotron Radiation Facility, the material of the present invention can be recycled, and has certain effects and practical application value.

Example 9. Study on UV-Induced Photoluminescence and Color Change

[0100] In this example, the crystal material was irradiated with UV light at 365 nm, to verify the color change and photoluminescence change of the material of the present invention.

[0101] The crystal material was irradiated with UV light at 365 nm in a solid-state spectrometer, and the luminescence spectrum and ultraviolet-visible absorption spectrum signals were collected at various times within 0-2 h (FIG. 13). Images of fluorescence changes at various times were taken, and the trend of changes in CIE of the fluorescence spectrum was fitted by CIE1931 software. Also, the linear relationship between the energy of UV light and the intensity ratio (I.sub.532/I.sub.432) of spectral characteristic peaks was fitted. As shown in FIGS. 14-17, the detectable range of the dose when the material is irradiated with UV light at 365 nm is 0-4.2 mJ. In the ranges of 0-0.04 mJ, 0.04-1.5 mJ, and 1.5-4.2 mJ, there are three linear trends of changes. After 60 s (0.04 mJ) of irradiation, the characteristic fluorescence peak at 432 nm is almost quenched, and the blue fluorescence signal is the weakest. After 60 s, the characteristic fluorescence peak at 532 nm becomes strong, and the fluorescence gradually changes from blue to blue-green and then to green fluorescence. The trend in color change is shown in the CIE diagram in FIG. 16.

[0102] FIG. 13 shows the changes in UV-Vis absorption spectrum after different energy of UV light. FIGS. 13a and b show that under irradiation with UV light at 365 nm in a solid-state spectrometer, the intensity of the absorption peak at 340 nm in the UV-Vis absorption spectrum decreases continuously in 60 s, and the intensities of the absorption peaks at 410 nm and 580 nm increase continuously; in 60 s-2 h, the intensity of the absorption peak at 340 nm continues to decrease, and the intensity of the absorption peak at 580 nm starts to decrease continuously, showing two-stage regular trends of change. At the same time, the color of the crystal turns yellow gradually, indicating that the adsorption of the crystal in the visible region changes and more energy of UV light absorbed also leads to the continuous increase of the fluorescence intensity.

[0103] The above results show that the crystal material of the present invention also has a good effect on the detection of high-frequency UV light. The energy of UV light can be qualitatively analyzed utilizing the radiation-induced color change, or quantitatively analyzed by the intensity of the luminescence signal.

[0104] While preferred embodiments of the present invention have been described above, the present invention is not limited thereto. It should be appreciated that some improvements and variations can be made by those skilled in the art without departing from the technical principles of the present invention, which are also contemplated to be within the scope of the present invention.