Self-activated long afterglow one-dimensional crystal rod luminescent material, preparation method and application thereof

Abstract

The application belongs to the technical field of inorganic light-storing multi-mode fluorescent communication materials, and particularly relates to a self-activated long-afterglow one-dimensional crystal rod luminescent material, a preparation method and application. The self-activated long-afterglow one-dimensional crystal rod luminescent material has a one-dimensional crystal rod geometry, and a chemical formula of MZnOS, wherein M is Ca, Ba or Sr. The self-activated long-afterglow one-dimensional crystal rod luminescent material breaks through the limitation of the existing powder system in the study of the luminescence mechanism, and provides an ideal material platform for in-depth analysis of the long-afterglow mechanism. The self-activated long-afterglow one-dimensional crystal rod luminescent material forms micro-element chemical primary and secondary trap units in the crystal lattice, can realize double-stable high-density trap and effective mass regulation of carriers, and further realize a high-capacity carrier storage and a four-mode luminescence stimulation response type light functional material of photoluminescence, long-afterglow, light-stimulated luminescence and heat-stimulated luminescence.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of inorganic storage light multi-mode fluorescent communication materials, and particularly relates to a self-activated long afterglow one-dimensional crystal rod luminescent material, a preparation method and application thereof. BACKGROUND

[0002] Long afterglow refers to the phenomenon that a solid material can continuously emit light for several minutes to several hours after being excited by a high-energy excitation light source and the external excitation is removed. This characteristic has important application value in the fields of optical data storage, medical imaging, multi-level encryption, photocatalysis and solar energy conversion. At present, researchers have developed various long afterglow materials doped with rare earth ions, such as CaAl2O4:Eu 2+ ,Nd 3+ and Sr2MgSi2O7:Eu 2+ ,Dy 3+ , etc., and have achieved success in commercial applications.

[0003] Long afterglow materials belong to weak light-emitting materials, and their light-emitting mechanism depends on the storage and release of carriers by trap centers in the matrix. However, since the trap types and states are not clear, the mechanism of long afterglow has not been fully explained, which seriously restricts the design and development of new long afterglow materials.

[0004] Existing research shows that the core composition of long afterglow materials usually includes three parts: matrix, luminescent center and trap center. The luminescent center mainly determines the light-emitting wavelength band, and some characteristics of the trap center, such as trap depth, trap density or concentration, usually determine the intensity and duration of the long afterglow. The trap center can be derived from lattice defects such as oxygen vacancies or F centers, or from impurity ions or artificially introduced dopant ions, such as Dy 3+ ,Nd 3+ or Cr 3+ . In some cases, the luminescent center itself can also have a trap function, such as Cr 3+ or Bi 3+ . However, in actual research, the trap type in a specific afterglow light-emitting process is often difficult to determine, and the details of the carrier migration path are also difficult to detect. This leads to the fact that the development of new long afterglow materials currently mainly relies on the traditional trial-and-error method, and the performance optimization of existing long afterglow fluorescent powders also faces many technical challenges that need to be broken through.

[0005] In addition, due to the weak light-emitting characteristics of long afterglow materials, current commercial afterglow materials are mainly doped powder systems synthesized by high-temperature solid-state reaction method. However, this kind of doped powder system cannot control the anisotropy characteristics of the crystal due to the disordered morphology of the powder. And the existing spectral analysis can only obtain the average effect of a large number of powder particles, and it is difficult to reveal the intrinsic light-emitting behavior of single crystals. SUMMARY

[0006] In order to solve the above problems, the application provides a self-activated long afterglow one-dimensional crystal rod luminescent material, a preparation method and application thereof.

[0007] Compared with the average fluorescence spectrum, the single particle in-situ micro-spectrum can reveal more abundant local and individual spectral fine structure characteristics of the long afterglow material; considering the defects of the prior art, the self-activated long afterglow one-dimensional crystal rod luminescent material provided by the application can be used to reveal the potential physical mechanism of the long afterglow, and further study the transport properties of the optoelectronic device.

[0008] In order to achieve the above-mentioned purposes, the technical scheme of the application is as follows.

[0009] The application provides a self-activated long afterglow one-dimensional crystal rod luminescent material, and the chemical formula of the self-activated long afterglow one-dimensional crystal rod luminescent material is MZnOS, wherein M is Ca, Ba or Sr; the self-activated long afterglow one-dimensional crystal rod luminescent material has a one-dimensional crystal rod geometry; and the lattice parameters of the self-activated long afterglow one-dimensional crystal rod luminescent material are as follows: when M is Ca, the lattice parameters are a=5.6 Å, b=3.7 Å and c=9.8 Å; when M is Sr, the lattice parameters are a=5.7 Å, b=3.8 Å and c=10.0 Å; and when M is Ba, the lattice parameters are a=5.9 Å, b=3.9 Å and c=10.3 Å.

[0010] The self-activated long afterglow one-dimensional crystal rod luminescent material has a one-dimensional crystal rod geometry, can regulate the anisotropic properties of the crystal, clearly reveals the intrinsic luminescence behavior of the single crystal, breaks through the limitations of the existing powder system in the study of the luminescence mechanism, and provides an ideal material platform for in-depth analysis of the long afterglow mechanism.

[0011] The self-activated long afterglow one-dimensional crystal rod luminescent material forms micro-element chemical primary and secondary battery trap units in the crystal lattice, that is, forms a sandwich type NPN layered trap structure, thereby realizing the regulation of the double-stable high-density trap and the effective mass of the carrier, and further realizing the high-capacity carrier storage and the stimulation response type optical functional material with four modes of photoluminescence, long afterglow, photo-stimulated luminescence and thermal-stimulated luminescence.

[0012] In the sandwich type NPN layered trap structure, NPN represents an alternating semiconductor layer structure, specifically: N-type layer-P-type layer-N-type layer, wherein the main carrier of the N-type layer is an electron, and the main carrier of the P-type layer is a hole.

[0013] Preferably, when M is Ca or Sr, the crystal structure of the self-activated long afterglow one-dimensional crystal rod luminescent material is a three-dimensional layered crystal structure of a hexagonal system formed by connecting ZnS3O tetrahedrons and distorted MO3S3 octahedrons.

[0014] Preferably, when M is Ba, the crystal structure of the self-activated long afterglow one-dimensional crystal rod luminescent material is formed by adjacent ZnO2S2 tetrahedrons connected through vertexes to form a chain structure along a-axis and c-axis, and stacked into ZnO2S2 tetrahedron layers, and the interlayer of the ZnO2S2 tetrahedron layers is formed by eight-coordinated Ba 2+ The ions are separated to form a three-dimensional layered crystal structure of an orthorhombic system.

[0015] Preferably, the average length of the self-activated long afterglow one-dimensional crystal rod luminescent material is 8.0*10 3 μm~1.2*10 4 μm, and the diameter is 5.0*10 2 μm.

[0016] The second aspect of the present application provides a preparation method of a self-activated long afterglow one-dimensional crystal rod luminescent material, comprising the following steps:

[0017] using inorganic acid salts corresponding to M 2+ ions and ZnS as raw materials, and after grinding treatment, performing annealing treatment under an inert atmosphere to obtain the self-activated long afterglow one-dimensional crystal rod luminescent material; wherein M is Ca, Ba or Sr.

[0018] Preferably, the inert atmosphere is a nitrogen atmosphere.

[0019] In the preparation process, the present application protects the defect creator ions by using an inert atmosphere such as a nitrogen atmosphere, so that the variable valence ions can coexist, and effectively protects the bistable defect density, thereby comprehensively improving the energy storage capacity and obtaining a self-activated long afterglow one-dimensional crystal rod luminescent material with a one-dimensional crystal rod geometry. In the present application, stable electron hole defects and reduced system energy create conditions for the formation of one-dimensional crystal rods.

[0020] Preferably, the temperature of the annealing treatment is 850°C~1000°C, preferably 950°C, and the time of the annealing treatment is 5h~6h.

[0021] Preferably, the inorganic acid salt corresponding to M 2+ ions is a carbonate or nitrate corresponding to M 2+ ions.

[0022] The third aspect of the present application provides a self-activated long afterglow one-dimensional crystal rod luminescent material as a multi-mode luminescent stimulus-responsive optical functional material, and the self-activated long afterglow one-dimensional crystal rod luminescent material is the self-activated long afterglow one-dimensional crystal rod luminescent material described in the first aspect.

[0023] Preferably, the multi-mode luminescence is photoluminescence, long afterglow, light stimulus luminescence and heat stimulus luminescence.

[0024] In the present application, the stimulus-responsive optical functional material is a light-light conversion functional material or a light-electricity conversion functional material.

[0025] Advantages of the present application:

[0026] 1. The self-activated long afterglow material of the present application has a one-dimensional rod-like crystal geometry, and the anisotropic electronic structure characteristics of the single crystal provide intrinsic traps for the intrinsic afterglow luminescence behavior.

[0027] 2. The self-activated long afterglow one-dimensional crystal rod luminescent material has extremely low density, can stably operate in harsh environmental conditions such as high temperature and high humidity, can be easily picked up by a single electrode, and exhibits excellent manipulability and integration characteristics, and can be applied in the field of optoelectronic materials.

[0028] 3. In the process of preparing the self-activated long afterglow one-dimensional crystal rod luminescent material, the defect creator ions are protected by inert atmosphere, so that the variable valence ions can coexist, and the bistable defect density is effectively protected, thereby improving the energy storage capacity and obtaining the self-activated long afterglow one-dimensional crystal rod luminescent material with one-dimensional crystal rod geometry.

[0029] 4. The self-activated long afterglow one-dimensional crystal rod luminescent material is prepared by a traditional high-temperature solid-phase method, which has simple preparation process, large yield and low cost. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1X-ray diffraction patterns of samples of Examples 1-3. Wherein, (a) is the X-ray diffraction pattern of the sample of Example 1; (b) is the X-ray diffraction pattern of the sample of Example 2; (c) is the X-ray diffraction pattern of the sample of Example 3; (d) and (e) are schematic diagrams of the crystal structure of the sample of Example 2 at different viewing angles.

[0031] Figure 2 Scanning electron microscope images and energy dispersive X-ray spectroscopy element distribution maps of the sample of Example 2. Wherein, (a)-(c) are scanning electron microscope photos of the sample of Example 2 at different magnifications; (d)-(g) are energy dispersive X-ray spectroscopy element distribution maps of the sample of Example 2.

[0032] Figure 3 Photoluminescence and afterglow photos of the samples of Examples 1-3. Wherein, a is the photoluminescence photo of the samples of Examples 1-3; b is the afterglow photo of the samples of Examples 1-3.

[0033] Figure 4 Electronic band structure and density of states distribution maps of the sample of Example 2. Wherein, (a) is the electronic band structure; (b) is the density of states distribution map.

[0034] Figure 5 Electronic band structure and density of states distribution maps of the sample of Example 3. Wherein, (a) is the electronic band structure; (b) is the density of states distribution map.

[0035] Figure 6 Electronic band structure and density of states distribution maps of the sample of Example 1. Wherein, (a) is the electronic band structure; (b) is the density of states distribution map.

[0036] Figure 7 Effective mass of electrons and holes of the sample of Example 2. Wherein, (a) is the effective mass of electrons; (b) is the effective mass of holes.

[0037] Figure 8 Effective mass of electrons and holes of the sample of Example 3. Wherein, (a) is the effective mass of electrons; (b) is the effective mass of holes.

[0038] Figure 9 Effective mass of electrons and holes of the sample of Example 1. Wherein, (a) is the effective mass of electrons; (b) is the effective mass of holes.

[0039] Figure 10 Effective mass of electrons and holes of the sample of Example 2 under the action of 10% c-axis stress. Wherein, (a) is the effective mass of electrons; (b) is the effective mass of holes.

[0040] Figure 11 Effective mass of electron and hole of the sample of Example 3 under 10% c-axis stress. Wherein (a) is the effective mass of electron; (b) is the effective mass of hole.

[0041] Figure 12 Effective mass of electron and hole of the sample of Example 1 under 10% c-axis stress. Wherein (a) is the effective mass of electron; (b) is the effective mass of hole.

[0042] Figure 13 Thermal release curve of the sample of Example 1-Example 3.

[0043] Figure 14 Photoluminescence photo and afterglow photo of the sample of Example 2 under 254nm ultraviolet light irradiation. Wherein, a is the photoluminescence photo under 254nm ultraviolet light irradiation; b is the afterglow photo after irradiation.

[0044] Figure 15 Photoluminescence emission photo and afterglow photo of the sample of Example 2. Wherein, a is the fluorescence photo under 254nm light excitation; b is the fluorescence photo under 365nm light excitation; c is the afterglow photo 10 seconds after turning off 365nm ultraviolet light; d is the afterglow photo 10 minutes after turning off 365nm ultraviolet light; d is the afterglow photo 30 minutes after turning off 365nm ultraviolet light.

[0045] Figure 16 Photoluminescence transport map of the sample of Example 2 under 365nm ultraviolet light irradiation crystal rod end point, and thermal excitation fluorescence transport map and light excitation fluorescence transport map of one end of the crystal rod under thermal stimulation after turning off 365nm ultraviolet light. Wherein, a is the photoluminescence transport map of single crystal rod bending fluorescence transmission; b is the photoluminescence transport map of physical contact fluorescence transmission between crystal rods; c is the photoluminescence transport map of single crystal rod fluorescence waveguide transmission; d is the photoluminescence transport map of ring fluorescence transmission; e is the thermal excitation fluorescence transport map of one end of the crystal rod under thermal stimulation after turning off 365nm ultraviolet light; f is the thermal excitation fluorescence transport map of one end of the half-ring crystal rod under thermal stimulation after turning off 365nm ultraviolet light; g is the light excitation fluorescence transport map of one end of the crystal rod under laser stimulation after turning off 365nm ultraviolet light.

[0046] Figure 17 Photoluminescence emission spectrum map of the sample of Example 2 under light excitation of different wavelengths.

[0047] Figure 18 Photoluminescence excitation spectrum map of the sample of Example 2 at monitoring 472nm and 536nm.

[0048] Figure 19 Temperature dependent emission spectra of the sample of Example 2.

[0049] Figure 20 Temperature dependent emission spectra of the sample of Example 2.

[0050] Figure 21 Temperature dependent emission spectra of the sample of Example 2.

[0051] Figure 22 Temperature dependent emission spectra of the sample of Example 2.

[0052] Figure 23 Temperature dependent emission spectra of the sample of Example 2.

[0053] Figure 24 Dynamic photoluminescence spectra of the sample of Example 2.

[0054] Figure 25 Dynamic photoluminescence spectra of the sample of Example 2.

[0055] Figure 26 Schematic diagram of the crystal growth mechanism of the sample of Example 2. Wherein (a) is a simulated structure diagram of the sample of Example 2; (b) is a three-dimensional crystal structure diagram of the sample of Example 2; (c) is a scanning electron microscope photograph of the sample of Example 2.

[0056] Figure 27 Schematic diagram of the mechanism of the multimode fluorescence process of the sample of Example 2. Wherein CB represents the conduction band; V O represents the oxygen vacancy defect state; V O • represents the single positive charge oxygen vacancy; V O •• represents the double positive charge oxygen vacancy; V S represents the sulfur vacancy; V S • represents the single positive charge sulfur vacancy; V S •• represents the double positive charge sulfur vacancy; V Zn ” represents the double negative charge zinc vacancy; VB represents the valence band.

[0057] Figure 28The fluorescence photos of the sample of example 2 under irradiation of 365nm ultraviolet light with the assistance of different band-pass filters are shown in the figure. Wherein, a is the fluorescence photo under the assistance of 500nm-600nm green band-pass filter; b is the fluorescence photo under the assistance of 400nm-500nm blue band-pass filter; c is the fluorescence photo under the assistance of 600nm-700nm red band-pass filter.

[0058] Figure 29 The fluorescence photos of the sample of example 2 in water environment are shown in the figure. Wherein, a is the photo of the sample of example 2 floating on the water surface; b is the photo of the sample of example 2 floating on the water surface under irradiation of 365nm ultraviolet light; c is the afterglow photo of the sample of example 2 floating on the water surface after turning off the 365nm ultraviolet light; d is the afterglow photo of the sample of example 2 floating on the water surface after turning off the 365nm ultraviolet light for 10 minutes. DETAILED DESCRIPTION

[0059] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application is further described in detail below in combination with examples. It should be understood that the specific examples described herein are only used to explain the present application, and are not used to limit the present application.

[0060] Based on the examples in the present application, all other examples obtained by those skilled in the art without making creative efforts belong to the protection scope of the present application.

[0061] The present application provides a self-activated long-afterglow one-dimensional crystal rod luminescent material, which is obtained by constructing a space-separated sandwich type NPN layered trap structure, i.e. forming a micro-unit chemical battery type trap structure unit for layered storage of photo-generated carriers in the crystal lattice, coupling suitable melting point precursors in an inert atmosphere, inducing formation of a bistable high-density defect of a double anion vacancy, serving as a long-lifetime luminescence center and a trap center respectively, coupling unique carrier effective mass regulation, and then realizing high-capacity carrier storage and obtaining a multi-mode luminescence, including four modes of stimulation response type optoelectronic functional materials, such as communication device application materials or sensing micro-device application materials.

[0062] The self-activated long-afterglow one-dimensional crystal rod luminescent material of the present application is prepared by using M 2+ inorganic acid salt corresponding to the ion and ZnS as raw materials, and in-situ forming a defect structure by a solid phase reaction method under an inert atmosphere; and the chemical expression is MZnOS, wherein M is Ca, Sr or Ba.

[0063] The present application considers the adjustable factors of lattice structure and band gap, and preferably is Sr 2+ all instead of Ca 2+SrZnOS.

[0064] In order to fully grind and mix the components, the present application preferably adopts manual / ball milling to grind until all chemicals are fully mixed, for example, the grinding time is 0.5h-1.0h, the mixed powder with particle size ≤2μm is obtained, and the obtained mixed powder has smooth and delicate hand feeling. Ethanol is added as a lubricant during the grinding process.

[0065] In order to ensure that the components can fully react during the annealing process, the present application preferably performs the annealing process in an inert atmosphere, such as a nitrogen atmosphere, and the annealing temperature is preferably 950℃, which is lower than the sublimation temperature of the precursor raw material, and the sintering time is preferably 6h to achieve the purpose of fully reacting the components. In addition, the present application compares the products under different annealing atmospheres by controlling the annealing atmosphere, i.e., replacing the inert atmosphere with a reducing atmosphere and an air atmosphere. The core purpose is to control the trap type and valence. The results show that the inert atmosphere is the optimal atmosphere, which avoids the reduction of high-valence traps and inhibits oxygen vacancies, which is a key step to realize trap control in the present application. The inert atmosphere can be selected as a nitrogen atmosphere.

[0066] The technical solutions of the present application are further described below through specific examples.

[0067] In the following examples, the methods are conventional methods unless otherwise specified; and the reagents and materials are commercially available unless otherwise specified.

[0068] Example 1

[0069] A self-activated long afterglow one-dimensional crystal rod luminescent material with a chemical formula of CaZnOS. The specific preparation method is as follows: according to the stoichiometric ratio in CaZnOS, 0.2022g of CaCO3 and 0.1959g of ZnS are weighed. After mixing CaCO3 and ZnS, grinding for 0.5h, the mixed powder is obtained. The mixed powder is sintered at 950℃ for 6h under a nitrogen atmosphere, and after cooling to room temperature, a self-activated long afterglow one-dimensional crystal rod luminescent material, referred to as CaZnOS crystal rod, is collected.

[0070] Example 2

[0071] A self-activated long afterglow one-dimensional crystal rod luminescent material with a chemical formula of SrZnOS. The difference between Example 2 and Example 1 is only that Sr 2+ completely replaces Ca 2+The preparation method is as follows: 0.2982 g of SrCO3 and 0.1959 g of ZnS are weighed according to the stoichiometric ratio in SrZnOS. After mixing the SrCO3 and ZnS, the mixture is ground for 0.5 h to obtain a mixed powder. The mixed powder is sintered at 950 ℃ for 6 h under a nitrogen atmosphere, and the self-activated long afterglow one-dimensional crystal rod luminescent material, referred to as SrZnOS crystal rod, is collected after cooling to room temperature.

[0072] Example 3

[0073] A self-activated long afterglow one-dimensional crystal rod luminescent material has a chemical formula of BaZnOS. The difference between Example 3 and Example 1 is that Sr 2+ is completely replaced by Ca 2+ The preparation method is as follows: 0.3987 g of BaCO3 and 0.1959 g of ZnS are weighed according to the stoichiometric ratio in BaZnOS. After mixing the BaCO3 and ZnS, the mixture is ground for 0.5 h to obtain a mixed powder. The mixed powder is sintered at 950 ℃ for 6 h under a nitrogen atmosphere, and the self-activated long afterglow one-dimensional crystal rod luminescent material, referred to as BaZnOS crystal rod, is collected after cooling to room temperature.

[0074] Comparative Example 1

[0075] A self-activated long afterglow one-dimensional crystal rod luminescent material has a chemical formula of SrZnOS. The difference between Comparative Example 1 and Example 2 is that a mixed gas atmosphere of nitrogen and hydrogen is used instead of the nitrogen atmosphere in Example 2, and the volume ratio of nitrogen to hydrogen is 95:5.

[0076] Comparative Example 2

[0077] A self-activated long afterglow one-dimensional crystal rod luminescent material has a chemical formula of SrZnOS. The difference between Comparative Example 2 and Example 2 is that an air atmosphere is used instead of the nitrogen atmosphere in Example 2.

[0078] The self-activated long afterglow one-dimensional crystal rod luminescent materials prepared in Examples 1-3 are used as samples, and structure, morphology and fluorescence performance tests are performed, and the results are shown in Table 1. Figures 1-29

[0079] Test 1: Structure analysis

[0080] The samples of Examples 1-3 are subjected to X-ray diffraction tests, and the results are shown in Table 2. Figure 1 Figure 1 ​​In (a)-(c) of FIG. 1, the PDF number of the standard hexagonal phase CaZnOS is 01-076-3819, the ICSD number of the hexagonal phase SrZnOS is 431819, and the ICSD number of the orthorhombic phase BaZnOS is 171239. Compared with the standard hexagonal phase CaZnOS, the hexagonal phase SrZnOS and the orthorhombic phase BaZnOS, it can be seen that the samples of Examples 1-3 all show pure phases, and no second phase is generated. Moreover, the samples of Examples 1 and 2 all belong to the non-centrosymmetric hexagonal space group P63mc, and the sample of Example 3 belongs to the space group Cmcm.

[0081] As shown in (d) and (e) of FIG. 1, the samples of Examples 1-3 all have regular one-dimensional rod-like structures. Among them, the samples of Examples 1 and 2 are both hexagonal layered crystal structures. Figure 1

[0082] The samples of Examples 1 and 2 are connected by ZnS3O tetrahedrons and distorted MO3S3 octahedrons to form a three-dimensional layered crystal structure of the hexagonal system. Taking the sample of Example 2 as an example, the ZnS3O tetrahedron is formed by 1 Zn atom and 3 S atoms and 1 O atom, and the distorted SrO3S3 octahedron is formed by 1 Sr atom and 3 S atoms and 3 O atoms; these tetrahedrons are connected by sharing vertices to form a layered structure, and the Sr ions are located between the layers to play a role in separating and stabilizing the structure.

[0083] In the sample of Example 3, there are also two cation coordination environments, which are octahedral Ba 2+ and tetrahedral Zn 2+ . Among them, the Zn atom is tetrahedrally coordinated, and the coordination atoms are 2 O and 2 S. Adjacent ZnO2S2 tetrahedrons are connected by vertices to form a chain-like structure parallel to the a axis and the c axis, and are stacked into [ZnO2S2] tetrahedral layers; the layers of [ZnO2S2] tetrahedrons are separated by octahedral Ba 2+ ions to form a three-dimensional layered crystal structure of the orthorhombic system. The coordination environment of Ba 2+ is a distorted triangular prism, specifically, two larger rectangular faces of the isosceles triangular prism BaO4S2 are covered by the remaining two S atoms. The specific crystal parameters are shown in Table 1.

[0084] Table 1 Crystal parameters of the samples of Examples 1-3

[0085]

[0086] ​In the crystal structure of the sample of Example 1, the Ca-O bond length is approximately 2.3 μm to 2.5 μm; the Ca-S bond length is 2.7 μm to 3.0 μm; the Zn-O bond length is 1.9 μm to 2.1 μm; and the Zn-S bond length is 2.2 μm to 2.4 μm. In the crystal structure of the sample of Example 2, the Sr-O bond length is 2.60 μm to 2.80 μm; the Sr-S bond length is 3.00 μm to 3.20 μm; the Zn-O bond length is 1.95 μm to 2.10 μm; and the Zn-S bond length is 2.40 μm to 2.55 μm. In the crystal structure of the sample in Example 3, the bond lengths of Ba-O are 2.7 Ǻ to 2.95 Ǻ; the bond lengths of Ba-S are 3.15 to 3.30 Ǻ; the bond lengths of OS are 2.95 Ǻ to 3.10 Ǻ; the bond lengths of Zn-O are 1.95 Ǻ to 2.10 Ǻ; and the bond lengths of Zn-S are 2.25 Ǻ to 2.40 Ǻ.

[0087] Taking the sample from Example 2 as an example, the morphology and elemental distribution of the sample from Example 2 were tested using scanning electron microscopy. The results showed that the sample from Example 2 exhibited a regular rod-shaped crystal structure with an average length of approximately 8 × 10⁻⁶. 3 μm~12×10 3 μm, approximately 5×10 μm in diameter 2 μm, such as Figure 2 .

[0088] like Figure 1 As shown in (e), the crystal structure of the sample in Example 2 exhibits a polar layered structure on the ab plane, which significantly influences the rod-like growth pattern of the crystal. Some of the thinner crystal rods show spontaneous bending to form ring or semi-ring structures. The discreteness of the crystal rod length distribution and the coexistence of sporadic granular structures indicate that the MZnOS crystal rods tend to grow preferentially along the c-axis in one dimension, rather than being formed by the curling of two-dimensional sheets. Further observation revealed that the MZnOS crystal rods exhibit a typical hexagonal prism geometry with clear and sharp edges, further demonstrating from a morphological perspective that the MZnOS crystal rods tend to grow preferentially along the c-axis in one dimension. Energy-dispersive X-ray spectroscopy elemental mapping confirmed that Sr, Zn, O, and S are uniformly distributed in the MZnOS crystal rods, proving that its chemical composition is uniformly distributed.

[0089] Test 2: Fluorescence performance analysis.

[0090] A spectrometer was used to record photoluminescence emission spectra, photoluminescence excitation spectra, afterglow emission spectra, afterglow decay curves, and thermal release curves. In addition to the xenon lamp, a variety of other illumination sources were used, including a 365 nm ultraviolet lamp with a power of 5 W, an 808 nm laser with a power of 0 W-2 W adjustable, and a 980 nm laser with a power of 0 W-5 W adjustable. The temperature range of the thermal release curve measurement was 25 °C-300 °C, and the temperature rise rate was 1 °C / s. Before measuring the afterglow decay curve and the thermal release curve, the traps were thermally cleaned by heating the sample to 500 °C to ensure that the trap carriers were emptied. All spectra were corrected according to the spectral shape of the light source. All thermal release curve measurements were performed under the same test conditions for comparison. A Canon camera was used to take images of the samples and the luminescence phenomenon. The spectral measurements of the analysis detection process were all completed at room temperature. Before measuring the afterglow emission spectrum, the afterglow decay curve, and the thermal release curve, the sample had been pre-irradiated with ultraviolet light of the corresponding wavelength for 5 minutes.

[0091] The optical photographs of the blue-green photoluminescence and green afterglow luminescence of the samples of Example 1-Example 3 under ultraviolet light excitation were analyzed and compared, as shown in Figure 3 The results showed that the sample of Example 2 exhibited the strongest photoluminescence and long afterglow intensity under 254 nm ultraviolet light irradiation and after irradiation; while the sample of Example 1 had almost no visible afterglow phenomenon, which could be attributed to its relatively wide band gap and high carrier mobility.

[0092] The electronic band structure and state density distribution of the samples of Example 1-Example 3 were analyzed, as shown in Figures 4-6 The results showed that the samples of Example 1 and Example 2 were direct band gap, while the sample of Example 3 was indirect band gap. M = Ca, Sr, or Ba, as the atomic number of the alkaline earth metal M increased, the band width decreased from 3.79 eV to 3.58 eV and 3.29 eV. From the orbital components of the three samples in the total state density, it can be observed that the maximum valence band is composed of S-3p and O-2p states, and the minimum conduction band is composed of Zn-4s states, indicating that Zn-O and Zn-S are biased towards ionic bonds, and O-2p and S-3p provide electrons to Zn-4s. In addition, in the samples of Example 1 and Example 2, the conduction band minimum and the valence band maximum exhibited energy windows of about 2 eV and 1 eV, respectively, indicating that the electrons and holes had small effective masses and large ionic mobility.

[0093] The effective mass of the electrons and holes of the samples of Example 1-Example 3 was further calculated, as shown in Figures 7-9 where m e represents the effective mass of the electron; m hEffective mass of hole. The results show that the effective mass of electron and hole in the three samples shows strong anisotropy. The effective mass observed along the c-axis is the smallest, and when a stress of 10% is applied along the c-axis, the effective mass of the carrier along the c-axis increases sharply due to structural distortion, as shown in Figures 10-12 , which means that the application of stress can lead to direct recombination luminescence of interlayer electron-hole pairs.

[0094] In order to reveal the trap characteristics and control mechanism of the back afterglow characteristics of the samples of embodiment 1 to embodiment 3. First, the samples were pre-irradiated with 365 nm ultraviolet light for 5 minutes, and after the charging light source was turned off, the sample was measured for 1 minute, and the thermoluminescence curve was measured, as shown in Figure 13 The results show that the sample of embodiment 2 has the highest trap density and deeper trap distribution, which explains why the sample of embodiment 2 obtains the strongest and brightest afterglow due to its high-density energy storage traps. The thermoluminescence properties of the samples of embodiment 1 to embodiment 3 are shown in Table 2.

[0095] Table 2 Thermoluminescence properties of the samples of embodiment 1 to embodiment 3

[0096]

[0097] After the sample of embodiment 2 was irradiated with 254 nm ultraviolet light, it was found that some thin rods or rings or half rings emitted bright blue light, while some thicker rods emitted green light, as shown in Figure 14 a figure. After stopping the excitation light, all the SrZnOS crystal rods emitted green afterglow, as shown in Figure 14 b figure.

[0098] Comparing the newly prepared SrZnOS crystal rods with the SrZnOS crystal rods aged in air for a period of time, it was found that the newly prepared SrZnOS crystal rods mainly emitted blue light, as shown in Figure 15 a figure, while the number of blue crystal rods gradually decreased and the number of green crystal rods increased in the SrZnOS crystal rods aged in air for a period of time. In addition, under 365 nm ultraviolet light irradiation, in addition to the blue-green photoluminescence crystal rods, several orange photoluminescence crystal rods or zero-dimensional particles can also be observed, as shown in Figure 15 b figure. After turning off the irradiation source, all the single crystal rods or particles emitted green afterglow, as shown in Figure 14 and Figure 15 .

[0099] Considering photon communication, the photon transport properties of single crystal rods, physically contacted crystal rods, and crystal rod rings, half rings or broken spliced rings in the sample of embodiment 2 were further studied, as shown in Figure 16 . The excitation wavelength and pre-irradiation wavelength are 365 nm. As shown in Figure 16a and b of the sample of Example 2, the photoluminescence fluorescence can be observed to transport smoothly in the crystal rod and the junction under naked eyes when a single crystal rod or one end of the crystal rod in physical contact is irradiated by 365 nm ultraviolet light. Similarly, the photoluminescence can be transmitted along the waveguide ring without any obstacle in the ring. Even after the charging light source is turned off, the long afterglow, the thermally stimulated luminescence and the photo-stimulated luminescence of the single crystal rod or the junction of the two crystal rods and the ring, the semi-ring or the spliced ring formed by the crystal rods comply with the same waveguide transport rule, i.e. the multi-mode fluorescence can be transmitted from the excitation point along the length direction of the crystal rod without obvious leakage, which indicates the great application potential of the crystal rods in photonic devices such as optical fibers, waveguides and laser crystals.

[0100] The specific spectral component analysis is as follows: in the photoluminescence emission spectrum of the sample of Example 2, Figure 17 , the photoluminescence emission spectrum is composed of a green waveband with a peak value of 536 nm / 2.31 eV and a blue waveband with a peak value of 472 nm / 2.62 eV, so the single crystal rods produce blue-green emission under the photo-excitation of light in the range of 350 nm to 450 nm.

[0101] In the afterglow emission spectrum of the sample of Example 2, Figure 18 , the photoluminescence excitation spectrum has two peaks at 365 nm / 3.39 eV and 400 nm / 3.10 eV when monitoring the photoluminescence at 536 nm; and the photoluminescence excitation spectrum has a peak at 365 nm when monitoring the photoluminescence at 472 nm. In addition to the photoluminescence emission, the afterglow emission spectrum shown in Figure 19 , has only a single peak emission at 515 nm / 2.41 eV. In order to compare the multi-mode fluorescence of the sample of Example 2, the peak values of the spectra including the photoluminescence emission spectrum, the photoluminescence excitation spectrum and the afterglow emission spectrum are shown in Table 3 with the afterglow duration. It can be found from Table 3 that the peak values of the afterglow emission spectrum and the photoluminescence emission spectrum are not consistent, which implies that the afterglow center and the photoluminescence center may be different centers or different fluorescence energy level transitions of the same center. In addition, the peak values of the photoluminescence excitation spectrum are not consistent when monitoring different photoluminescence fluorescence peak values, which implies that the photoluminescence peak fluorescence also originates from different luminescence centers or different energy level transitions of the same luminescence center. Based on the spectral analysis and the electronic energy band structure, the multi-mode fluorescence originating from the transition between two specific energy levels of a specific luminescence center is marked in the summary drawing.

[0102] Table 3 Comparison of the spectral peak values of the sample of Example 2 and the afterglow emission time

[0103]

[0104] Note: "-" represents none or undetected. mon λ represents the fluorescence monitoring fluorescence wavelength; λ ex λ represents the excitation wavelength; λ chargedenotes the pre-irradiation wavelength.

[0105] The temperature dependent luminescence properties of the sample of Example 2 were tested after pre-irradiation at 365 nm UV light for 5 minutes, as shown in Figures 20-23 . In the temperature range studied, the photoluminescence emission peak at 472 nm and the afterglow emission peak at 515 nm monotonically decrease with increasing temperature, while the photoluminescence emission peak at 536 nm reaches a peak at 50 °C and then decreases with increasing temperature, as shown in Figure 20 and Figure 21 . The different temperature dependence means that these emission peaks originate from different energy level transitions. The afterglow decay curves are temperature dependent, with the slowest decay rate at 80 °C, as shown in Figure 22 . The thermal release curve of the afterglow at 515 nm of the sample of Example 2 was monitored, and the thermal release curve shows a single peak feature with a peak at around 80 °C, as shown in Figure 23 , which explains why the afterglow decay rate is slowest at 80 °C. With increasing temperature, the thermal release curve peak gradually moves to higher temperature, and the thermally stimulated luminescence intensity rapidly decreases.

[0106] To further prove the trap type, the precursor powders of SrCO3 and ZnS were mixed in a chemical ratio and ground thoroughly, and then placed in a high-temperature annealing furnace, with the annealing atmosphere adjusted to a reducing atmosphere or an air atmosphere, and then annealed at 900 °C for 10 h to prepare the samples of Comparative Example 1 and Comparative Example 2; the reducing atmosphere is a mixed gas of N2 and H2 with a volume ratio of 95:5. The results show that both samples do not obtain long afterglow, and the precursor powders are not grown into one-dimensional long rods in an inert atmosphere, which implies the importance of the annealing atmosphere. By comparing the samples of Example 2, Comparative Example 1 and Comparative Example 2 prepared under three atmosphere conditions, it can be concluded that the thermal Schottky oxygen vacancies, i.e. V O •• and V Zn coexist in the sample of Example 2 prepared in an inert atmosphere, which are responsible for the afterglow energy storage, which enables them to compensate for charges with each other, reduce the system energy, and make the compound more stable. The oxygen vacancies contain three defect state energy levels, which are V O •• , V O • and V O . Stable electron hole defects and reduced system energy create conditions for the formation of one-dimensional crystal rods. In order to further understand the charging and discharging process of the traps, as shown in Figure 24 and Figure 25, the intensity of blue and green photoluminescence emission increases slowly with the increase of illumination time. This confirms that the transition recombination probability of conduction band→oxygen vacancy defect state and double positive charge oxygen vacancy defect state→single positive charge oxygen vacancy defect state increases due to the increase of the number of electrons in conduction band and double positive charge oxygen vacancy defect state. These results show that the valence state of double positive charge oxygen vacancy does not change or its change is negligible during the afterglow process, which indirectly supports the conclusion that the afterglow originates from the transition of double positive charge sulfur vacancy defect state→double negative charge zinc vacancy defect state.

[0107] The crystal growth mechanism of the sample of Example 2 was studied, as Figure 26 The sample of Example 2 has a layered polar structure similar to that of a microcell NPN diode layer, microcell NPN, denoted as double positive charge oxygen vacancy-double negative charge zinc vacancy-double positive charge sulfur vacancy, i.e. V O •• -V Zn "-V S •• The photo-generated carriers are stored in different NPN layers, respectively. Under external disturbance, electrons transition from high energy level to low energy level and recombine with holes to emit light.

[0108] The mechanism schematic diagram of the processes of photoluminescence, long afterglow, thermally stimulated luminescence and photo-stimulated luminescence of the sample of Example 2 is shown in Figure 27 Under 254 nm / 365 nm ultraviolet light irradiation, electrons transition from valence band, zinc vacancy defect state or ground state V O to conduction band, denoted as process ①. Part of these electrons return to oxygen-related defect state from conduction band through charge transfer, resulting in the transformation of CB-V O and V O • -VB vacancy, i.e. process ② and process ③, respectively, generating blue and green photoluminescence. Another part of the electrons are captured by double positive charge sulfur vacancy; under thermal stimulation or light stimulation, the charge transfers from double positive charge sulfur vacancy defect state to double negative charge zinc vacancy defect state, generating green afterglow emission, denoted as process ④. Therefore, photoluminescence mainly originates from the related transition between conduction band and oxygen vacancy defect energy level. Afterglow is generated by the transformation of electron transfer between double positive charge sulfur vacancy defect state to double negative charge zinc vacancy defect state. Therefore, photoluminescence and afterglow occur through different carrier transport paths. Therefore, blue, green and weak red photoluminescence can be allocated from CB→V O , V O •• →V O and V O • →VB transition vacancy, respectively. With the aid of a band-pass filter, three primary colors of blue, green and red can be obtained, respectively, asFigure 28 The long afterglow is attributed to the transition from double positive charge sulfur vacancy defect state to double negative charge zinc vacancy defect state. Therefore, it can be concluded that in the coarse crystal rods, V O •• is the main form of defects, while in the fine crystal rods, V O • is increased.

[0109] Considering the photoelectric properties and one-dimensional transport properties of the one-dimensional crystal rods, these crystal rods have great application potential in photoelectric materials. Further test the working ability of the sample of example 2 in water environment, such as Figure 29 . It is found that these crystal rods float completely on the water surface after being put into the water environment and emitting sound waves, which indicates that these crystal rods have very low density. In addition, the photoluminescence and afterglow performance are completely unaffected in the water environment, which indicates that they can work normally in harsh environments such as high heat and high humidity. Therefore, the sample of example 2 has the characteristics of light weight and easy to be picked up with a single electrode, and can be applied to device components.

[0110] The above is only the preferred embodiment of the present application, and is not used to limit the present application, any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. The application of a self-activated long-persistence one-dimensional crystal rod luminescent material as a stimulus-responsive photofunctional material with multimode luminescence, characterized in that, The chemical formula of the self-activated long-afterglow one-dimensional crystal rod luminescent material is MZnOS, where M is Ca, Ba or Sr; the self-activated long-afterglow one-dimensional crystal rod luminescent material has a one-dimensional crystal rod geometric configuration. When M is Ca or Sr, the self-activated long-afterglow one-dimensional crystal rod luminescent material belongs to space group P63mc; when M is Ba, the self-activated long-afterglow one-dimensional crystal rod luminescent material belongs to space group Cmcm. The average length of the self-activated long-persistence one-dimensional crystal rod luminescent material is 8.0 × 10⁻⁶. 3 μm~1.2×10 4 μm, with a diameter of 5.0 × 10 2 μm.

2. The application of the self-activated long-afterglow one-dimensional crystal rod luminescent material according to claim 1 as a stimulus-responsive photofunctional material with multimode luminescence, characterized in that, When M is Ca or Sr, the crystal structure of the self-activated long afterglow one-dimensional crystal rod luminescent material is a three-dimensional layered crystal structure of hexagonal crystal system formed by connecting ZnS3O tetrahedra and distorted MO3S3 octahedra.

3. The application of the self-activated long-persistence one-dimensional crystal rod luminescent material according to claim 1 as a stimulus-responsive photofunctional material with multimode luminescence, characterized in that... When M is Ba, the crystal structure of the self-activated long-afterglow one-dimensional crystal rod luminescent material consists of adjacent ZnO2S2 tetrahedra connected by vertices to form a chain-like structure parallel to the a-axis and c-axis, which are then stacked into ZnO2S2 tetrahedral layers. The interlayer structure of the ZnO2S2 tetrahedral layers is composed of eight-coordinated Ba atoms. 2+ Ions separate the crystals, forming a three-dimensional layered crystal structure with an orthorhombic crystal system.

4. The application of the self-activated long-afterglow one-dimensional crystal rod luminescent material according to claim 1 as a stimulus-responsive photofunctional material with multimode luminescence, characterized in that... The preparation method of self-activated long-afterglow one-dimensional crystal rod luminescent material includes the following steps: With M 2+ Using inorganic acid salts corresponding to ions and ZnS as raw materials, after grinding, the MZnOS crystal rods are annealed under an inert atmosphere. The MZnOS crystal rods tend to grow in one dimension preferentially along the c-axis direction to obtain the self-activated long afterglow one-dimensional crystal rod luminescent material; wherein, M is Ca, Ba or Sr.

5. The application of the self-activated long-afterglow one-dimensional crystal rod luminescent material according to claim 4 as a stimulus-responsive photofunctional material with multimode luminescence, characterized in that... The inert atmosphere is nitrogen.

6. The application of the self-activated long-afterglow one-dimensional crystal rod luminescent material according to claim 4 as a stimulus-responsive photofunctional material with multimode luminescence, characterized in that... The annealing temperature is 850℃~1000℃, and the annealing time is 5h~6h.

7. The application of the self-activated long-persistence one-dimensional crystal rod luminescent material according to claim 4 as a stimulus-responsive photofunctional material with multimode luminescence, characterized in that, M 2+ The inorganic acid salt corresponding to the ion is M. 2+ The carbonate or nitrate corresponding to the ion.

8. The application of the self-activated long-afterglow one-dimensional crystal rod luminescent material according to claim 1 as a stimulus-responsive photofunctional material with multimode luminescence, characterized in that, The multimode emission includes photoluminescence, long afterglow, photo-excited emission, and thermally excited emission.

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