Short-wave infrared luminescent material and application thereof

Abstract

The application discloses a short-wave infrared light-emitting material and application thereof, and relates to the technical field of light-emitting materials.The chemical formula of the short-wave infrared light-emitting material is: Ca2A 1‑x Er x MgSc 1‑y Cr y Ge3O 12 , wherein A is Lu element and / or Y element, and the value range of x and y is as follows: 0

Description

Technical Field

[0001] This invention relates to the field of luminescent materials technology, and more specifically, to a short-wave infrared luminescent material and its applications. Background Technology

[0002] Against the backdrop of the global transition to a circular economy, the efficient recycling and high-value utilization of plastic waste has become an important way to alleviate environmental pollution and resource shortages. Currently, hyperspectral imaging sorting technology based on near-infrared (NIR) reflectance spectroscopy has been widely applied in the field of automated waste plastic sorting, demonstrating high sorting efficiency and industrial application potential. However, in actual complex waste plastic systems, the above technology still has certain limitations: on the one hand, carbon black, often added to black plastics, has a strong absorption effect on near-infrared light, resulting in a lack of reflectance signals, making effective identification difficult; on the other hand, this technology mainly relies on molecular vibrational information for discrimination, making it difficult to distinguish between homogeneous and heterogeneous plastics with the same chemical structure but different uses; in addition, oil or ink contamination on the plastic surface can also interfere with its characteristic spectral signals, significantly reducing sorting accuracy and reliability.

[0003] To overcome the aforementioned problems, researchers have proposed a sorting technique based on short-wave infrared (SWIR, 900–2500 nm) fluorescent tracers. This method introduces specific fluorescent markers into plastic products, which then generate characteristic emission signals upon excitation by an external light source, thereby enabling the coded identification of plastic categories or recycling paths. Because this identification process does not depend on the intrinsic spectral properties of the material, it effectively avoids the interference problems present in traditional near-infrared sorting techniques, exhibiting high identification accuracy and stability.

[0004] In the prior art, luminescent materials with emission peaks in the 900–1300 nm range and capable of generating short-wave infrared emission under visible light excitation have been widely reported in existing published non-patent or patent literature. For example, luminescent materials produced by Cr... 3+ / Yb 3+ The co-doped system can achieve emission at approximately 1030 nm under blue light excitation (non-patent literature). Laser Photonics Rev. , 2024, 18, 2300993, Chinese patents CN114836204B, CN115058247B and CN111423881B); through Cr 3+ / Ni 2+ Co-doped systems can achieve emission at approximately 1250 nm (non-patent literature). J. Mater. Chem. C(referring to patents CN110093155A and 2023, 11, 11046). However, such materials often suffer from limited luminescence efficiency or broad emission bands. On the other hand, to achieve longer wavelengths (e.g., ~1550 nm) to improve the signal-to-noise ratio during spectral detection, existing tracers typically rely on high-power near-infrared lasers (e.g., 980 nm) as excitation sources (non-patent literature). ACS Appl. Mater. Interfaces ,2023, 15, 43985; J. Mater. Chem. C (2025, 13, 4605), limiting its application in low-cost, portable sorting systems. Furthermore, some visible-light-excited long-wavelength SWIR tracers (such as Cr) 3+ / Er 3+ Co-doped systems typically exhibit multi-band emission (e.g., ~820 nm and ~1550 nm), with a higher proportion of short-wavelength emission components (non-patent literature). J. Lumin. (2026, 293, 121762 and international patent WO2019144933A1) can easily interfere with the identification signal, thus affecting the sorting accuracy.

[0005] Therefore, there is still a lack of a luminescent material system in the current technology that can achieve efficient short-wave infrared emission with the main peak concentrated in 1400-1650nm under visible light excitation, so as to meet the needs of high-precision and low-cost plastic sorting applications. Summary of the Invention

[0006] To overcome the shortcomings of the prior art, this invention provides a short-wave infrared luminescent material and its application that can achieve high efficiency under visible light excitation with a main peak concentrated in the 1400-1650nm range, thereby solving the problems of multiple overlapping emission bands, reliance on near-infrared laser excitation, and insufficient sorting and identification accuracy of existing luminescent materials.

[0007] The first aspect of this invention provides a short-wave infrared luminescent material, wherein the chemical formula of the short-wave infrared luminescent material is: Ca2A 1-x Er x MgSc 1-y Cr y Ge3O 12 Where A is the Lu element and / or the Y element, and the values ​​of x and y are in the following ranges: 0 <x<0.3,0.2<y<0.7; The short-wave infrared luminescent material is prepared by the following steps: According to the stoichiometric ratio, inorganic raw materials containing Ca, A, Mg, Sc, Ge, Cr and Er are weighed and mixed. The mixture is first sintered in an air atmosphere and then sintered in a mixed atmosphere of nitrogen and hydrogen to obtain the short-wave infrared luminescent material. The main crystal phase of the short-wave infrared luminescent material has a garnet structure and belongs to the cubic crystal system.

[0008] This technical solution limits Ca2A 1-x Er x MgSc 1-y Cr y Ge3O 12 This specific chemical formula and elemental range of the garnet structure, combined with a two-step sintering process of "primary sintering in air atmosphere + secondary sintering in a nitrogen-hydrogen mixed atmosphere," prevents the reduction and volatilization of Mg and Ge elements, ensuring the integrity of the chemical composition and structure. This structural design can simultaneously accommodate Cr. 3+ Ions and Er 3+ doping, utilizing high Cr 3+ The concentration quenching effect of ion doping significantly suppressed Cr 3+ Intrinsic strong emission of ions in the 800–1000 nm wavelength range; utilizing Cr 3+ To Er 3+ The high energy transfer efficiency of the medium allows the fluorescence energy generated by excitation to be highly concentrated in the target wavelength band of 1400–1650 nm, thus fundamentally solving the problem of strong crosstalk in multiple bands of traditional tracers and meeting the dual requirements of high-precision plastic sorting for signal purity and industrial production.

[0009] In one possible implementation, the inorganic raw material is selected from oxides, carbonates, nitrates, or fluorides of the corresponding element.

[0010] Compared with existing technologies, this invention selects oxides, carbonates, nitrates, or fluorides of corresponding elements as inorganic raw materials, taking advantage of the characteristics of these compounds being easily decomposed at high temperatures and having high reactivity. This raw material selection strategy not only ensures the accuracy of the stoichiometry of the final product but also reduces raw material costs, making the preparation process more environmentally friendly and easier to control, which is beneficial for obtaining high-purity target luminescent materials.

[0011] In one possible implementation, the process further includes adding a flux and mixing it thoroughly before performing a sintering process; The flux is selected from boric acid, lithium carbonate, magnesium fluoride and barium fluoride, and the amount of flux added accounts for 1-10 wt% of the mass of the mixture.

[0012] Compared with existing technologies, this invention selects specific types of fluxes such as boric acid and lithium carbonate, and strictly controls the amount added to 1-10 wt% of the total raw material mass. The mineralization effect of the flux lowers the activation energy of the solid-phase reaction. Specifically, this not only effectively suppresses the volatilization of raw materials at high temperatures but also promotes atomic diffusion and grain boundary migration, thereby improving the microstructure and luminescence uniformity of the final product and avoiding the negative impact of excessive flux residue on the material's luminescence performance.

[0013] In one possible implementation, the parameters for a single sintering process are as follows: temperature 1000-1250℃, time 7-10h.

[0014] Compared with existing technologies, this invention sets the temperature of the primary sintering process to 1000-1250℃ and the time to 7-10h in an air atmosphere. This parameter range ensures the complete decomposition of carbonates and other components in the raw materials, and allows for sufficient solid-state chemical reactions of each component at high temperatures to initially form a garnet structure. The air atmosphere in this step effectively increases the vapor pressure of elements such as Mg and Ge, avoiding the volatilization loss of elements during high-temperature sintering, and facilitating the subsequent suppression of Cr under a reducing atmosphere. 3+ The transformation of ions to Cr4+ ions lays the foundation and avoids material sintering and caking caused by excessively high temperature or long time.

[0015] In one possible implementation, the parameters for the secondary sintering process are as follows: temperature 950-1100℃, time 3-10h.

[0016] Compared with existing technologies, this invention performs secondary sintering at 950-1100℃ in a nitrogen-hydrogen mixed atmosphere. This step is crucial for controlling the Cr content. 3+ and Er 3+ The valence state and coordination environment are crucial. This heat treatment process further eliminates lattice defects inside the material and optimizes the occupancy of rare earth ions in the garnet lattice, which is a key process step to achieve efficient, peak emission of the material in the 1400-1650nm wavelength range.

[0017] In one possible implementation, a post-processing step is performed after the secondary sintering, comprising sequential grinding, washing, and grading / screening. This combined grinding, washing, and grading / screening post-processing effectively removes impurities and unreacted substances that may have been generated during sintering, and allows for precise control of particle size. This not only yields micron-sized luminescent powder with uniform particle size distribution but also improves the material's dispersibility in the plastic matrix, enabling it to meet the stringent requirements of industrial sorting systems for powder flowability and optical consistency.

[0018] The second objective of this invention is to provide an application of the aforementioned short-wave infrared emitting material in the sorting of plastic products, the application specifically including the following steps: The short-wave infrared luminescent material is added to the plastic products to be sorted, and then transported to the testing station; The plastic product containing short-wave infrared luminescent material is irradiated with a visible light source with a wavelength of 400–700 nm, which excites the plastic product containing short-wave infrared luminescent material to generate a fluorescence signal with an emission peak located at 1400–1650 nm. The fluorescence signal is collected, and the material category of the plastic product to be sorted containing short-wave infrared emitting material is identified based on the signal characteristics to complete the sorting.

[0019] Compared with existing technologies, this invention introduces short-wave infrared luminescent materials as tracers into plastic products. Utilizing the strong absorption of visible light and the highly penetrating short-wave infrared emission characteristics of these materials, plastic identification is transformed into the capture of fluorescence signals at specific wavelengths. This method overcomes the limitation of traditional near-infrared sorting technology, which relies on the intrinsic spectrum of plastics, and enables rapid and accurate encoding, identification, and classification of plastic materials against complex backgrounds without contact with the plastic.

[0020] In one possible implementation, the material of the plastic product to be sorted is selected from polyethylene, polypropylene, polyethylene terephthalate, polyvinyl chloride, and polystyrene. This short-wave infrared luminescent material maintains stable luminescence performance in both polar and non-polar plastic matrices, enabling unified identification and efficient sorting of various common plastic wastes, thus possessing extremely high industrial application value. Attached Figure Description

[0021] Figure 1 The XRD pattern of the short-wave infrared luminescent material in Embodiment 1 of the present invention; Figure 2 The excitation spectra of the short-wave infrared luminescent material in Example 1 of the present invention, and the luminescent samples in Comparative Example 1 and Comparative Example 2 are shown. Figure 3 The emission spectra of the short-wave infrared luminescent material in Example 1 of the present invention, and the luminescent samples in Comparative Example 1 and Comparative Example 2 are shown. Figure 4 This is a graph showing the trend of luminescence thermal stability of the short-wave infrared luminescent material in Embodiment 1 of the present invention; Figure 5 This is a demonstration diagram of the plastic sorting application in Embodiment 1 of the present invention.

[0022] Explanation of reference numerals in the attached drawings: 1-Conveyor belt; 2-Feeding device; 3-Visible light source; 4-Multi-channel hyperspectral camera; 5-Automatic sorting device. Detailed Implementation

[0023] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described in detail below. It should be noted that the following embodiments are only used to illustrate the implementation methods and typical parameters of the present invention, and are not intended to limit the parameter range described in the present invention. Reasonable variations derived therefrom are still within the protection scope of the claims of the present invention.

[0024] It should be noted that the endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0025] Unless otherwise defined, all terms, symbols, and other scientific terms used herein are intended to have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In some instances, terms having a conventional meaning are defined herein for clarification or ease of reference, and such definitions should not be construed as indicating a significant difference from conventional understanding in the art. The technical methods described or referenced herein are generally well understood by those skilled in the art and employed by conventional methods. Unless otherwise stated, the use of commercially available kits, reagents, and instruments shall be performed according to the manufacturer's instructions and parameters.

[0026] like Figure 5 As shown, this invention further provides an example of a plastic sorting application method based on short-wave infrared luminescent materials. It mainly consists of a conveyor belt 1, a feeding device 2, a visible light source 3, a multi-channel hyperspectral camera 4, and an automatic sorting device 5. The specific implementation steps are as follows: 1. Addition of short-wave infrared luminescent material: The short-wave infrared luminescent material of the present invention is added to the plastic product to be sorted by means of internal doping in extrusion injection molding or surface printing, so that the short-wave infrared luminescent material is evenly distributed inside the plastic product or attached to the surface of the product, and the plastic product to be sorted is marked with short-wave infrared luminescent material. The plastic products to be sorted are selected from: polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polyvinyl chloride (PVC), and polystyrene (PS). 2. Conveying and feeding: The plastic products to be sorted, marked with short-wave infrared luminescent material, are placed in the unloading device 2 and conveyed to the detection station at a constant speed by the conveyor belt 1 to achieve continuous online conveying; 3. Excitation and Signal Acquisition: At the detection station, a visible light source 3 (LED or OLED) with a wavelength of 400-700nm is used to irradiate the plastic products to be sorted, exciting the short-wave infrared luminescent material within them to generate a short-wave infrared fluorescence signal with a main peak concentrated at 1400–1650nm, and without obvious Cr. 3+ Ion visible-near-infrared clutter interference. Simultaneously, a multi-channel hyperspectral camera (4 channels) is used to acquire fluorescence signals in real time, converting the optical signals into electrical signals and transmitting them to the intelligent sorting system. 4. Identification and Sorting Execution: The intelligent sorting system identifies the material category of plastic products based on the collected 1400–1650nm characteristic fluorescence signal and issues an execution command to the automatic sorting device 5; the automatic sorting device 5 sorts different plastic products into corresponding classification boxes according to the material category, completing high-precision automated sorting.

[0027] It is worth mentioning that this sorting method is applicable to the stable identification and sorting of carbon black-containing black plastics, homogeneous plastics, and plastics with surface oil / ink contamination.

[0028] The following examples further illustrate this point.

[0029] Example 1

[0030] This embodiment provides a short-wave infrared luminescent material, which is prepared by the following method: Step S1, press Ca2Lu 0.95 Er 0.05 MgSc 0.6 Cr 0.4 Ge3O 12 According to the stoichiometric ratio in the text, high-purity CaCO3, Lu2O3, Er2O3, MgO, Sc2O3, Cr2O3 and GeO2, as well as H3BO3 accounting for 3wt% of the total weight as a flux, are accurately weighed and thoroughly ground to obtain a mixture; Step S2: Sinter the obtained mixture at 1100℃ in air atmosphere for 8 hours, cool it down and grind it again to obtain mixed powder; Step S3: Sinter the obtained mixed powder at 1000℃ in a mixed atmosphere of nitrogen and hydrogen for 4 hours; after cooling, grind, wash and classify the sintered product to obtain the short-wave infrared luminescent material.

[0031] Figure 1 The XRD pattern of the short-wave infrared luminescent material obtained in this embodiment is shown below. Figure 1 It can be seen that the crystal structure of this short-wave infrared luminescent material is designed based on the garnet structure and belongs to the cubic crystal system; Figure 4 This is a graph showing the trend of luminescence thermal stability of the short-wave infrared luminescent material prepared in this embodiment. From... Figure 4 It can be seen that the fluorescence thermal quenching of the prepared short-wave infrared luminescent material is very small, and the luminescence integral intensity can still maintain more than 90% of that at room temperature at 150℃.

[0032] Example 2

[0033] This embodiment provides a short-wave infrared luminescent material, which is prepared by the following method: Step S1, press Ca2Lu 0.9 Er 0.1 MgSc 0.6 Cr 0.4 Ge3O 12 According to the stoichiometric ratio in the text, high-purity CaCO3, Lu2O3, Er2O3, MgO, Sc2O3, Cr2O3 and GeO2, as well as barium fluoride accounting for 2wt% of the total weight as a flux, are accurately weighed and thoroughly ground to obtain a mixture; Step S2: Sinter the obtained mixture at 1250℃ in air atmosphere for 7 hours, cool it down and grind it again to obtain mixed powder; Step S3: Sinter the obtained mixed powder at 1100℃ in a mixed atmosphere of nitrogen and hydrogen for 3 hours; after cooling, grind, wash and classify the sintered product to obtain the short-wave infrared luminescent material.

[0034] Example 3

[0035] This embodiment provides a short-wave infrared luminescent material, which is prepared by the following method: Step S1, press Ca2Lu 0.95 Er 0.05 MgSc 0.6 Cr 0.4 Ge3O 12 According to the stoichiometric ratio in the text, high-purity CaF2, Lu2O3, Er2O3, Mg(NO3)2, Sc2O3, Cr2O3 and GeO2, as well as H3BO3 accounting for 3wt% of the total weight as a flux, are accurately weighed and thoroughly ground to obtain a mixture; Step S2: Sinter the obtained mixture at 1100℃ in air atmosphere for 8 hours, cool it down and grind it again to obtain mixed powder; Step S3: Sinter the obtained mixed powder at 1000℃ in a mixed atmosphere of nitrogen and hydrogen for 4 hours; after cooling, grind, wash and classify the sintered product to obtain the short-wave infrared luminescent material.

[0036] Example 4

[0037] This embodiment provides a short-wave infrared luminescent material, which is prepared by the following method: Step S1, press Ca2Y 0.82 Er 0.18 MgSc 0.5 Cr 0.5 Ge3O 12 According to the stoichiometric ratio in the text, high-purity CaCO3, Y2O3, Er2O3, MgO, Sc2O3, Cr2O3 and GeO2, as well as magnesium fluoride accounting for 3wt% of the total weight as a flux, are accurately weighed and thoroughly ground to obtain a mixture; Step S2: Sinter the obtained mixture at 1000℃ in air atmosphere for 9 hours, cool it down and grind it again to obtain mixed powder; Step S3: Sinter the obtained mixed powder at 1050℃ in a mixed atmosphere of nitrogen and hydrogen for 5 hours; after cooling, grind, wash and classify the sintered product to obtain the short-wave infrared luminescent material.

[0038] Example 5

[0039] This embodiment provides a short-wave infrared luminescent material, which is prepared by the following method: Step S1, press Ca2Lu 0.85 Y 0.1 Er 0.05 MgSc 0.5 Cr 0.5 Ge3O 12 The stoichiometric ratios in the mixture are as follows: high-purity CaCO3, Lu2O3, Y2O3, Er2O3, MgO, Sc2O3, Cr2O3 and GeO2, and H3BO3 accounting for 5wt% of the total weight as a flux are accurately weighed and thoroughly ground to obtain a mixture. Step S2: Sinter the obtained mixture at 1100℃ in air atmosphere for 8 hours, cool it down and grind it again to obtain mixed powder; Step S3: Sinter the obtained mixed powder at 1000℃ in a mixed atmosphere of nitrogen and hydrogen for 4 hours; after cooling, grind, wash and classify the sintered product to obtain the short-wave infrared luminescent material.

[0040] Example 6

[0041] This embodiment provides a short-wave infrared luminescent material, which is prepared by the following method: Step S1, press Ca2Lu 0.15 Er 0.25 MgSc 0.35 Cr 0.65 Ge3O 12According to the stoichiometric ratio in the text, high-purity CaF2, Lu2O3, Er2O3, MgO, Sc2O3, Cr2O3 and GeO2, as well as lithium carbonate accounting for 4wt% of the total weight as a flux, are accurately weighed and thoroughly ground to obtain a mixture; Step S2: Sinter the obtained mixture at 1100℃ in air atmosphere for 8 hours, cool it down and grind it again to obtain mixed powder; Step S3: Sinter the obtained mixed powder at 1000℃ in a mixed atmosphere of nitrogen and hydrogen for 4 hours; after cooling, grind, wash and classify the sintered product to obtain the short-wave infrared luminescent material.

[0042] Example 7

[0043] This embodiment provides a short-wave infrared luminescent material, which is prepared by the following method: Step S1, press Ca2Y 0.9 Er 0.1 MgSc 0.79 Cr 0.21 Ge3O 12 According to the stoichiometric ratio in the text, high-purity CaCO3, Y2O3, Er2O3, MgO, Sc2O3, Cr2O3 and GeO2, as well as H3BO3 accounting for 4wt% of the total weight as a flux, are accurately weighed and thoroughly ground to obtain a mixture; Step S2: Sinter the obtained mixture at 1100℃ in air atmosphere for 8 hours, cool it down and grind it again to obtain mixed powder; Step S3: Sinter the obtained mixed powder at 1000℃ in a mixed atmosphere of nitrogen and hydrogen for 4 hours; after cooling, grind, wash and classify the sintered product to obtain the short-wave infrared luminescent material.

[0044] Example 8

[0045] This embodiment provides a short-wave infrared luminescent material, which is prepared by the following method: Step S1, press Ca2Lu 0.81 Er 0.19 MgSc 0.45 Cr 0.55 Ge3O 12 According to the stoichiometric ratio in the text, high-purity CaCO3, Lu2O3, Er2O3, MgO, Sc2O3, Cr2O3 and GeO2, as well as H3BO3 accounting for 3wt% of the total weight as a flux, are accurately weighed and thoroughly ground to obtain a mixture; Step S2: Sinter the obtained mixture at 1100℃ in air atmosphere for 8 hours, cool it down and grind it again to obtain mixed powder; Step S3: Sinter the obtained mixed powder at 1000℃ in a mixed atmosphere of nitrogen and hydrogen for 4 hours; after cooling, grind, wash and classify the sintered product to obtain the short-wave infrared luminescent material.

[0046] Comparative Example 1 This comparative example provides a luminescent sample, which is prepared by the following method: Step S1, press Ca2LuMgSc 0.6 Cr 0.4 Ge3O 12 According to the stoichiometric ratio in the text, high-purity CaCO3, Lu2O3, MgO, Sc2O3, Cr2O3 and GeO2, as well as H3BO3 accounting for 3wt% of the total weight as a flux, are accurately weighed and thoroughly ground to obtain a mixture; Step S2: Sinter the obtained mixture at 1100℃ in air atmosphere for 8 hours, cool it down and grind it again to obtain mixed powder; Step S3: Sinter the obtained mixed powder at 1000℃ in a mixed atmosphere of nitrogen and hydrogen for 4 hours; after cooling, grind, wash, and classify the sintered product to obtain the luminescent sample.

[0047] Comparative Example 2 This comparative example provides a luminescent sample, which is prepared by the following method: Step S1, press Ca2Lu 0.95 Er 0.05 MgScGe3O 12 According to the stoichiometric ratio in the text, high-purity CaCO3, Lu2O3, Er2O3, MgO, Sc2O3 and GeO2, as well as H3BO3 accounting for 3wt% of the total weight as a flux, are accurately weighed and thoroughly ground to obtain a mixture; Step S2: Sinter the obtained mixture at 1100℃ in air atmosphere for 8 hours, cool it down and grind it again to obtain mixed powder; Step S3: Sinter the obtained mixed powder at 1000℃ in a mixed atmosphere of nitrogen and hydrogen for 4 hours; after cooling, grind, wash, and classify the sintered product to obtain the luminescent sample.

[0048] Figure 2 The images show the excitation spectra of the short-wave infrared luminescent material in Example 1 of this invention, and the luminescent samples in Comparative Examples 1 and 2. Figure 2It can be seen that the excitation of the short-wave infrared luminescent material prepared in Example 1 is located in the blue light region of 400–500 nm and the red light region of 600–700 nm in the visible light band. The excitation of the luminescent sample prepared in Comparative Example 1 is located in the blue light region of 400–500 nm and the red light region of 600–700 nm in the visible light band. The excitation of the luminescent sample prepared in Comparative Example 2 is located in the ultraviolet region below 400 nm and the visible light band at 530 nm. The absorption band exhibits narrow band weak absorption.

[0049] Figure 3 The images show the emission spectra of the short-wave infrared luminescent material in Example 1 of this invention, and the luminescent samples in Comparative Examples 1 and 2. Figure 3 It can be seen that the short-wave infrared luminescent material prepared in Example 1 has an emission spectrum with a main peak covering 1400-1650nm under 450nm blue light excitation, and a main peak wavelength of 1536nm; the luminescent sample prepared in Comparative Example 1 has an emission spectrum covering 650-1000nm under 450nm blue light excitation, and a peak wavelength of ~800nm; the luminescent sample prepared in Comparative Example 2 has an emission spectrum with a main peak covering 1400-1650nm under 380nm ultraviolet light excitation, and a main peak wavelength of 1536nm.

[0050] While the present invention has been disclosed above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of this disclosure, and all such changes and modifications will fall within the scope of protection of this invention.

Claims

1. A short-wave infrared luminescent material, characterized in that, The chemical formula of the short-wave infrared luminescent material is: Ca2A 1- x Er x MgSc 1-y Cr y Ge3O 12 , wherein A is Lu element and / or Y element, and the value ranges of x and y are as follows: 0.05<x<0.15, 0.4≤y≤0.65; the short-wave infrared luminescent material is prepared by the following steps: according to the stoichiometric ratio, the inorganic raw materials containing Ca, A, Mg, Sc, Ge, Cr and Er are respectively weighed and mixed, then subjected to a primary sintering treatment in an air atmosphere, and then subjected to a secondary sintering treatment in a mixed atmosphere of nitrogen and hydrogen, to obtain the short-wave infrared luminescent material; the main crystal phase of the short-wave infrared luminescent material has a garnet structure and belongs to the cubic crystal system; The parameters for the first sintering process are as follows: temperature 1000-1250℃, time 7-10h; The parameters for the secondary sintering process are as follows: temperature 950-1100℃, time 3-10h.

2. The short-wave infrared luminescent material as described in claim 1, characterized in that, The inorganic raw materials are selected from oxides, carbonates, nitrates or fluorides of the corresponding elements.

3. The short-wave infrared luminescent material as described in claim 1, characterized in that, Before the first sintering process, the process includes adding a flux and mixing it evenly; the flux is selected from boric acid, lithium carbonate, magnesium fluoride and barium fluoride, and the amount of flux added accounts for 1-10 wt% of the mass of the mixture.

4. The short-wave infrared luminescent material as described in claim 1, characterized in that, After the secondary sintering process, a post-processing is performed, which includes grinding, washing and grading screening in sequence.

5. The application of a short-wave infrared luminescent material as described in any one of claims 1-4 in the sorting of plastic products, characterized in that, The application specifically includes the following steps: adding the short-wave infrared luminescent material to the plastic product to be sorted, and then conveying it to the detection station; irradiating the plastic product containing the short-wave infrared luminescent material with a visible light source of wavelength 400–700 nm to excite the plastic product to generate a fluorescence signal with an emission peak located at 1400–1650 nm; collecting the fluorescence signal, and identifying the material category of the plastic product containing the short-wave infrared luminescent material according to the signal characteristics to complete the sorting.

6. The application as described in claim 5, characterized in that, The plastic products to be sorted are made of one of polyethylene, polypropylene, polyethylene terephthalate, polyvinyl chloride, and polystyrene.

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