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

Abstract

The invention belongs to the technical field of inorganic light-storing multimode fluorescent communication materials, and particularly relates to a self-activated long-afterglow one-dimensional crystal rod luminescent material as well as a preparation method and application thereof. The self-activated long-afterglow one-dimensional crystal rod luminescent material is in a one-dimensional crystal rod-shaped geometric configuration, the chemical expression is MZnOS, and M is Ca, Ba or Sr. The self-activated long-afterglow one-dimensional crystal rod luminescent material breaks through the limitation of an existing powder system in luminescent mechanism research, an ideal material platform is provided for deep analysis of a long-afterglow mechanism, and the self-activated long-afterglow one-dimensional crystal rod luminescent material forms an infinitesimal chemical primary battery positive and negative electrode trap unit in crystal lattices, so that the self-activated long-afterglow one-dimensional crystal rod luminescent material has the advantages that the self-activated long-afterglow one-dimensional crystal rod luminescent material has a wide application prospect. Bistable high-density traps and effective quality regulation and control of current carriers can be realized, so that high-capacity current carrier storage is realized, and a stimulus-responsive optical function material with quadruple light emitting modes of photoluminescence, long afterglow, light stimulus luminescence and thermal stimulus luminescence is obtained.

Description

Technical Field

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

[0002] Long afterglow refers to the phenomenon that a solid material can continue to emit light for several minutes to hours after being excited by a high-energy excitation light source. This property makes it have important application value in optical data storage, medical imaging, multi-level encryption, photocatalysis and solar energy conversion. Currently, researchers have developed a variety of long afterglow materials doped with rare earth ions, such as CaAl2O4:Eu 2+ ,Nd 3+ and Sr2MgSi2O7:Eu 2+ ,Dy 3+ etc. and have been successfully applied in commercial applications.

[0003] Long-lasting glow materials are weak luminescent materials whose luminescence mechanism relies on the storage and release of charge carriers by trap centers in the matrix. However, due to the lack of clarity on the type and state of the traps, the mechanism of long-lasting glow remains incompletely elucidated, which severely restricts the design and development of new long-lasting glow materials.

[0004] Existing research shows that the core components of long afterglow materials usually include three parts: matrix, luminescent center and trap center. The luminescent center mainly determines the luminescent wavelength, while 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 may come from lattice defects, such as oxygen vacancies or F centers, or from impurity ions or artificially introduced doping ions, such as Dy 3+ 、Nd 3+ or Cr 3+ In some cases, the luminescence center itself can also serve as a trap, such as Cr 3+ Or Bi 3+ However, in actual research, it is often difficult to identify the trap types involved in a specific afterglow luminescence process, and the details of the carrier migration pathway are also difficult to detect. As a result, the development of new long-afterglow materials currently relies mainly on traditional trial-and-error methods, and the performance optimization of existing long-afterglow phosphors also faces many technical challenges that need to be overcome.

[0005] Furthermore, due to the weak luminescence characteristics of long-lasting materials, current commercially available materials are primarily doped powder systems synthesized via high-temperature solid-state reactions. However, these doped powder systems, due to their disordered morphology, cannot control the anisotropic properties of the crystals. Existing spectral analysis can only capture the average effect of a large number of powder particles, making it difficult to reveal the intrinsic luminescence behavior of single crystals. Summary of the Invention

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

[0007] Compared with the average fluorescence spectrum, single-particle in situ microscopic spectroscopy can reveal richer local and individual spectral fine structure characteristics in long-afterglow materials; considering the shortcomings of the existing technology, the self-activated long-afterglow one-dimensional crystal rod luminescent material provided by the present invention can be used to reveal the potential physical mechanism of long afterglow and further study the transport properties of optoelectronic devices.

[0008] To achieve the above objectives, the technical solutions of the present invention are as follows.

[0009] A first aspect of the present invention provides a self-activated long-afterglow one-dimensional crystal rod luminescent material, the chemical expression of the self-activated long-afterglow one-dimensional crystal rod luminescent material being MZnOS, wherein M is Ca, Ba or Sr; the self-activated long-afterglow one-dimensional crystal rod luminescent material having a one-dimensional crystal rod-shaped geometric configuration; the lattice parameters of the self-activated long-afterglow one-dimensional crystal rod luminescent material being as follows: when M is Ca, the lattice parameters are a=5.6Å, b=3.7Å, c=9.8Å; when M is Sr, the lattice parameters are a=5.7Å, b=3.8Å, c=10.0Å; when M is Ba, the lattice parameters are a=5.9Å, b=3.9Å, c=10.3Å.

[0010] The self-activated long afterglow one-dimensional crystal rod luminescent material of the present invention has a one-dimensional crystal rod-shaped geometric configuration, can regulate the anisotropic properties of the crystal, clearly reveal the intrinsic luminescence behavior of the single crystal, break through the limitations of the existing powder system in the study of luminescence mechanism, and provide 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 of the present invention forms microelement chemical primary battery positive and negative electrode trap units in the crystal lattice, that is, forms a spatially separated sandwich-type NPN layered trap structure, thereby realizing bistable high-density traps and effective carrier mass control, thereby realizing high-capacity carrier storage and obtaining a stimulus-responsive optical functional material with quadruple mode luminescence of photoluminescence, long afterglow, light-stimulated luminescence and thermally stimulated luminescence.

[0012] In the sandwich NPN layered trap structure, NPN represents an alternating semiconductor layer structure, specifically: N-type layer-P-type layer-N-type layer, where the main carriers of the N-type layer are electrons and the main carriers of the P-type layer are holes.

[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 by vertices to form a chain structure parallel to the a-axis and the c-axis, and stacked into ZnO2S2 tetrahedron layers, and the interlayers of the ZnO2S2 tetrahedron layers are formed by octa-coordinated Ba 2+ Ions are separated to form a three-dimensional layered crystal structure of the 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, with a diameter of 5.0×10 2 μm.

[0016] A second aspect of the present invention provides a method for preparing a self-activated long-lasting one-dimensional crystal rod luminescent material, comprising the following steps: M 2+ The inorganic acid salt corresponding to the ion and ZnS are used as raw materials, which are ground and then annealed in an inert atmosphere to obtain the self-activated long afterglow one-dimensional crystal rod luminescent material; wherein M is Ca, Ba or Sr.

[0017] Preferably, the inert atmosphere is a nitrogen atmosphere.

[0018] During the preparation process, the present invention utilizes an inert atmosphere, such as nitrogen, to protect the defect creator ions, allowing the coexistence of variable-valence ions while effectively protecting the bistable defect density. This improves overall energy storage capacity and yields a self-activated, long-lasting one-dimensional crystal rod luminescent material with a one-dimensional crystal rod geometry. In the present invention, stable electron-hole defects and reduced system energy create the conditions for the formation of one-dimensional crystal rods.

[0019] Preferably, the annealing temperature is 850° C. to 1000° C., preferably 950° C., and the annealing time is 5 h to 6 h.

[0020] Preferably, M 2+ The inorganic acid salt corresponding to the ion is M 2+ ions corresponding to carbonate or nitrate.

[0021] The third aspect of the present invention provides a self-activated long-lasting one-dimensional crystal rod luminescent material as a stimulus-responsive optical functional material for multi-mode luminescence, wherein the self-activated long-lasting one-dimensional crystal rod luminescent material is the self-activated long-lasting one-dimensional crystal rod luminescent material described in the first aspect.

[0022] Preferably, the multimode luminescence is photoluminescence, long afterglow, light-stimulated luminescence and heat-stimulated luminescence.

[0023] In the present invention, the stimulus-responsive optical functional material is a light-to-light conversion functional material or a light-to-electricity conversion functional material. The mechanism of multi-mode luminescence originates from the spatially separated sandwich-type NPN layered trap structure and the carriers with a large effective mass along the length of the crystal rod, which provides a new perspective for explaining the long afterglow mechanism. The self-activated long afterglow one-dimensional crystal rod luminescent material described in the present invention has an extremely low density, which is less than that of water, so that it can float on the water surface, and in the water environment, the photoluminescence and afterglow performance are completely unaffected. This shows that the self-activated long afterglow one-dimensional crystal rod luminescent material of the present invention can operate stably under harsh environmental conditions such as high temperature and high humidity, and can also be easily picked up by a single electrode, showing excellent controllability and integration characteristics, and can be used in the field of optoelectronic communication materials.

[0024] Beneficial effects of the present invention: 1. The self-activated long-afterglow material of the present invention has a one-dimensional rod-shaped crystal geometric configuration, and its single-crystal anisotropic electronic structure characteristics provide intrinsic traps for the intrinsic afterglow luminescence behavior. The self-activated long-afterglow one-dimensional crystal rod luminescent material of the present invention, based on the anisotropic electronic structure combined with the layered characteristics, forms micro-element chemical primary battery positive and negative electrode layered trap structural units along the length of the rod within the lattice, thereby achieving bistable high-density traps and effective carrier mass control, thereby realizing high-capacity carrier storage and serving as a stimulus-responsive optical functional material for multi-mode luminescence. The present invention breaks the limitation of the solid-state reaction method that it is difficult to prepare single-crystal self-activated long-afterglow materials with regular morphology, and achieves a major breakthrough.

[0025] 2. The self-activated long-afterglow one-dimensional crystal rod luminescent material of the present invention has an extremely low density and can operate stably under harsh environmental conditions such as high temperature and high humidity. It can also be easily picked up by a single electrode, showing excellent controllability and integration characteristics, and can be applied in the field of optoelectronic materials.

[0026] 3. In the process of preparing the self-activated long-afterglow one-dimensional crystal rod luminescent material, the present invention adopts an inert atmosphere to protect the defect creator ions so that the variable valence ions can coexist, while effectively protecting 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-shaped geometric configuration.

[0027] 4. The self-activated long afterglow one-dimensional crystal rod luminescent material of the present invention is prepared by a traditional high-temperature solid-phase method, which has a simple preparation process, high output, and low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1The X-ray diffraction patterns of the samples of Examples 1 to 3 are shown. (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.

[0029] Figure 2 The following are scanning electron microscope images and energy-dispersive X-ray spectroscopy elemental distribution maps of the sample of Example 2. (a) to (c) are scanning electron microscope images of the sample of Example 2 at different magnifications; (d) to (g) are energy-dispersive X-ray spectroscopy elemental distribution maps of the sample of Example 2.

[0030] Figure 3 The photoluminescence images and afterglow images of the samples of Examples 1 to 3 are shown in Figures a and b.

[0031] Figure 4 The electronic band structure and state density distribution diagram of the sample of Example 2. (a) is the electronic band structure; (b) is the state density distribution diagram.

[0032] Figure 5 The electronic band structure and state density distribution diagram of the sample of Example 3. (a) is the electronic band structure; (b) is the state density distribution diagram.

[0033] Figure 6 The electronic band structure and state density distribution diagram of the sample of Example 1. (a) is the electronic band structure; (b) is the state density distribution diagram.

[0034] Figure 7 are the effective masses of electrons and holes of the sample of Example 2, where (a) is the effective mass of electrons and (b) is the effective mass of holes.

[0035] Figure 8 are the effective masses of electrons and holes of the sample of Example 3, where (a) is the effective mass of electrons and (b) is the effective mass of holes.

[0036] Figure 9 are the effective masses of electrons and holes of the sample of Example 1, where (a) is the effective mass of electrons and (b) is the effective mass of holes.

[0037] Figure 10 The effective masses of electrons and holes in the sample of Example 2 under 10% c-axis stress, where (a) is the effective mass of electrons and (b) is the effective mass of holes.

[0038] Figure 11 The effective masses of electrons and holes for the sample of Example 3 under 10% c-axis stress, where (a) is the effective mass of electrons and (b) is the effective mass of holes.

[0039] Figure 12 The effective masses of electrons and holes in the sample of Example 1 under 10% c-axis stress, where (a) is the effective mass of electrons and (b) is the effective mass of holes.

[0040] Figure 13 These are the thermal release curves of the samples of Examples 1 to 3.

[0041] Figure 14 The photoluminescence photographs of the sample of Example 2 under 254nm ultraviolet light irradiation and the afterglow photograph after irradiation are shown in Figure 2. (a) is the photoluminescence photograph under 254nm ultraviolet light irradiation; (b) is the afterglow photograph after irradiation.

[0042] Figure 15 These are the photoluminescence emission and afterglow luminescence images of the sample of Example 2. a is the fluorescence image under 254 nm excitation; b is the fluorescence image under 365 nm excitation; c is the afterglow image 10 seconds after the 365 nm UV light was turned off; d is the afterglow image 10 minutes after the 365 nm UV light was turned off; and d is the afterglow image 30 minutes after the 365 nm UV light was turned off.

[0043] Figure 16 The following are the photoluminescence transport diagrams of the sample of Example 2 under 365nm ultraviolet light irradiation on the end of the crystal rod, as well as the thermally stimulated fluorescence transport diagrams and optically stimulated fluorescence transport diagrams of one end of the crystal rod under thermal stimulation after the 365nm ultraviolet light is turned off. Among them, a is the photoluminescence transport diagram of fluorescence transmission in a single crystal rod bend; b is the photoluminescence transport diagram of fluorescence transmission in physical contact between crystal rods; c is the photoluminescence transport diagram of fluorescence waveguide transmission in a single crystal rod; d is the photoluminescence transport diagram of fluorescence transmission in a ring-shaped ring; e is the thermally stimulated fluorescence transport diagram of one end of the crystal rod under thermal stimulation after the 365nm ultraviolet light is turned off; f is the thermally stimulated fluorescence transport diagram of one end of the semi-ring crystal rod under thermal stimulation after the 365nm ultraviolet light is turned off; g is the optically stimulated fluorescence transport diagram of one end of the crystal rod under laser stimulation after the 365nm ultraviolet light is turned off.

[0044] Figure 17 Graphs showing the photoluminescence emission spectra of the sample of Example 2 under light excitation at different wavelengths.

[0045] Figure 18 This is a photoluminescence excitation spectrum of the sample of Example 2 when monitoring at 472 nm and 536 nm.

[0046] Figure 19 These are the afterglow emission spectra of the sample of Example 2 after charging at different pre-irradiation wavelengths.

[0047] Figure 20 This is the temperature-dependent emission spectrum of the sample of Example 2.

[0048] Figure 21 This is the temperature-dependent afterglow emission spectrum of the sample of Example 2.

[0049] Figure 22 After the sample of Example 2 was pre-irradiated with 365 nm ultraviolet light for 5 minutes, the temperature-dependent afterglow decay curve of the afterglow emission at 515 nm was monitored.

[0050] Figure 23 After the sample of Example 2 was pre-irradiated with 365 nm ultraviolet light for 5 minutes, the temperature dependence of the afterglow emission at 515 nm was monitored.

[0051] Figure 24 This is a dynamic photoluminescence spectrum of the sample of Example 2 when monitoring fluorescence at 472 nm.

[0052] Figure 25 This is a dynamic photoluminescence spectrum of the sample of Example 2 when monitoring fluorescence at 536 nm.

[0053] Figure 26 Schematic diagram of the crystal growth mechanism of the sample of Example 2. (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; and (c) is a scanning electron microscope photograph of the sample of Example 2.

[0054] 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 a single positively charged oxygen vacancy; V O •• represents a doubly positively charged oxygen vacancy; V S represents a sulfur vacancy; V S • represents a single positively charged sulfur vacancy; V S •• represents a doubly positively charged sulfur vacancy; V Zn ” indicates a doubly negatively charged zinc vacancy; VB indicates valence band.

[0055] Figure 28These are fluorescence images of the sample from Example 2 under 365nm UV irradiation with different bandpass filters. (a) is a fluorescence image taken with a 500nm-600nm green bandpass filter; (b) is a fluorescence image taken with a 400nm-500nm blue bandpass filter; and (c) is a fluorescence image taken with a 600nm-700nm red bandpass filter.

[0056] Figure 29 These are fluorescence photographs of the sample of Example 2 in a water environment. a is a photograph of the sample of Example 2 floating on the water surface; b is a photoluminescence photograph of the sample of Example 2 floating on the water surface under 365nm ultraviolet light; c is an afterglow photograph of the sample of Example 2 floating on the water surface after the 365nm ultraviolet light is turned off; d is an afterglow photograph of the sample of Example 2 floating on the water surface 10 minutes after the 365nm ultraviolet light is turned off. DETAILED DESCRIPTION

[0057] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0058] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative work shall fall within the scope of protection of the present invention.

[0059] The present invention provides a self-activated long afterglow one-dimensional crystal rod luminescent material, which constructs a spatially separated sandwich-type NPN layered trap structure, that is, a microelement chemical galvanic cell trap structure unit for layered storage of photogenerated carriers is formed in the crystal lattice. An inert atmosphere is coupled with a suitable melting and boiling point precursor to induce the formation of double anion vacancy bistable high-density defects, which serve as long-life luminescence centers and trap centers respectively. The unique carrier effective quality control is coupled to achieve high-capacity carrier storage and obtain multi-mode luminescence, including a stimulus-responsive optoelectronic functional material with four modes of photoluminescence, long afterglow, light-stimulated luminescence and thermally stimulated luminescence, for example, application materials for communication devices or application materials for sensing micro devices.

[0060] The self-activated long afterglow one-dimensional crystal rod luminescent material of the present invention is based on M 2+ The inorganic acid salt corresponding to the ion and ZnS are used as raw materials, and a defect structure is formed in situ by a solid phase reaction method under an inert atmosphere; its chemical expression is MZnOS, where M is Ca, Sr or Ba.

[0061] The present invention takes into account the lattice structure and band gap adjustable factors, preferably Sr 2+ Complete replacement of Ca 2+The self-activated long afterglow one-dimensional crystal rod luminescent material has a chemical expression of SrZnOS.

[0062] To ensure thorough mixing of the components, the present invention preferably employs manual or ball milling until all chemicals are thoroughly mixed. For example, the milling time is 0.5 to 1.0 hours, resulting in a mixed powder with a particle size of ≤2 μm and a smooth, fine feel. Ethanol is added as a lubricant during the milling process.

[0063] In order to ensure that each component can fully react during the annealing process, the present invention preferably performs annealing in an inert atmosphere, such as a nitrogen atmosphere, and the preferred annealing temperature is 950°C, which is lower than the sublimation temperature of the precursor raw materials, and the preferred sintering time is 6 hours, so as to achieve the purpose of full reaction of each component. The present invention controls the annealing atmosphere, that is, replaces the inert atmosphere with a reducing atmosphere and an air atmosphere respectively, and compares the products under different annealing atmospheres. Its core purpose is to control the trap type and valence. The results show that an inert atmosphere is the optimal atmosphere, which avoids the high-valence trap from being reduced and suppresses oxygen vacancies, which is a key step in achieving the regulation of traps in the present invention. The inert atmosphere used can be a nitrogen atmosphere.

[0064] The technical solution of the present invention is further described below through specific embodiments.

[0065] In the following examples, the methods described are conventional methods unless otherwise specified; the reagents and materials described are commercially available unless otherwise specified.

[0066] Example 1 A self-activated, long-lasting one-dimensional crystal rod luminescent material, chemically expressed as CaZnOS, is prepared as follows: 0.2022g of CaCO3 and 0.1959g of ZnS are weighed according to the stoichiometric ratio in CaZnOS. The CaCO3 and ZnS are mixed and ground for 0.5h to obtain a mixed powder. The mixed powder is sintered at 950°C for 6h under a nitrogen atmosphere and then cooled to room temperature before being collected to obtain a self-activated, long-lasting one-dimensional crystal rod luminescent material, referred to as a CaZnOS crystal rod.

[0067] Example 2 A self-activated long afterglow one-dimensional crystal rod luminescent material, the chemical expression of which is SrZnOS. The difference between Example 2 and Example 1 is that Sr 2+ Completely replaces Ca 2+The specific preparation method is as follows: 0.2982g of SrCO3 and 0.1959g of ZnS were weighed according to the stoichiometric ratio in SrZnOS. The SrCO3 and ZnS were mixed and ground for 0.5h to obtain a mixed powder. The mixed powder was sintered at 950°C for 6h under a nitrogen atmosphere and collected after cooling to room temperature to obtain a self-activated long-lasting one-dimensional crystal rod luminescent material, referred to as SrZnOS crystal rod.

[0068] Example 3 A self-activated long afterglow one-dimensional crystal rod luminescent material, the chemical expression of which is BaZnOS. The only difference between Example 3 and Example 1 is that Sr 2+ Completely replaces Ca 2+ The specific preparation method is as follows: According to the stoichiometric ratio in BaZnOS, 0.3987g of BaCO3 and 0.1959g of ZnS were weighed. The BaCO3 and ZnS were mixed and ground for 0.5h to obtain a mixed powder. The mixed powder was sintered at 950°C for 6h under a nitrogen atmosphere and collected after cooling to room temperature to obtain a self-activated long-lasting one-dimensional crystal rod luminescent material, referred to as BaZnOS crystal rod.

[0069] Comparative Example 1 A self-activated long-lasting one-dimensional crystal rod luminescent material, the chemical formula of which is SrZnOS. The difference between Comparative Example 1 and Example 2 is that the nitrogen atmosphere of Example 2 is replaced by a mixed atmosphere of nitrogen and hydrogen, wherein the volume ratio of nitrogen to hydrogen is 95:5.

[0070] Comparative Example 2 A self-activated long-lasting one-dimensional crystal rod luminescent material, the chemical formula of which is SrZnOS. The difference between Comparative Example 2 and Example 2 is that the nitrogen atmosphere in Example 2 is replaced by air atmosphere.

[0071] The self-activated long afterglow one-dimensional crystal rod luminescent materials prepared in Examples 1 to 3 were used as samples to test their structure, morphology and fluorescence properties. The results are as follows: Figures 1 to 29 shown.

[0072] Test 1: Structural Analysis.

[0073] The samples of Examples 1 to 3 were subjected to X-ray diffraction tests, and the results were as follows: Figure 1 shown. Figure 1In (a) to (c), the PDF number of the standard hexagonal CaZnOS phase is 01-076-3819, the ICSD number of the hexagonal SrZnOS phase is 431819, and the ICSD number of the orthorhombic BaZnOS phase is 171239. Comparison with the standard hexagonal CaZnOS, hexagonal SrZnOS, and orthorhombic BaZnOS phases reveals that the samples of Examples 1 to 3 are all pure phases, with no secondary phases formed. Furthermore, the samples of Examples 1 and 2 both belong to the non-centrosymmetric hexagonal space group P63mc, while the sample of Example 3 belongs to the space group Cmcm.

[0074] like Figure 1 In (d) and (e), the samples of Examples 1 to 3 all present a regular one-dimensional rod-like structure. Among them, the samples of Examples 1 and 2 both have a hexagonal layered crystal structure.

[0075] The samples of Examples 1 and 2 are three-dimensional layered crystal structures of a hexagonal system formed by connecting ZnS3O tetrahedra and distorted MO3S3 octahedra. Taking the sample of Example 2 as an example, the ZnS3O tetrahedron is formed by one Zn atom, three S atoms, and one O atom, while the distorted SrO3S3 octahedron is formed by one Sr atom, three S atoms, and three O atoms. These tetrahedra are connected by shared vertices to form a layered structure, with Sr ions located between the layers, acting as separators and stabilizing the structure.

[0076] There are also two cation coordination environments in the sample of Example 3, namely, eight-coordinated Ba 2+ Lattice site and four-coordinate Zn 2+ Among them, Zn atoms are tetrahedral coordinated, with 2 O and 2 S atoms as the coordinating atoms. Adjacent ZnO2S2 tetrahedra are connected by vertices to form a chain structure parallel to the a-axis and c-axis, and stacked into [ZnO2S2] tetrahedral layers. The interlayers of [ZnO2S2] tetrahedral layers are composed of octa-coordinated Ba 2+ Ions separate to form a three-dimensional layered crystal structure of the orthorhombic system. 2+ The coordination environment is a deformed triangular prism, specifically an isosceles triangular prism of BaO4S2 with two larger rectangular faces covered by the remaining two S atoms. Specific crystal parameters are shown in Table 1.

[0077] Table 1 Crystal parameters of samples of Examples 1 to 3

[0078] In the crystal structure of the sample of Example 1, the bond length of Ca-O is approximately 2.3-2.5 Ǻ; the bond length of Ca-S is 2.7-3.0 Ǻ; the bond length of Zn-O is 1.9-2.1 Ǻ; and the bond length of Zn-S is 2.2-2.4 Ǻ. In the crystal structure of the sample of Example 2, the bond length of Sr-O is 2.60-2.80 Ǻ; the bond length of Sr-S is 3.00-3.20 Ǻ; the bond length of Zn-O is 1.95-2.10 Ǻ; and the bond length of Zn-S is 2.40-2.55 Ǻ. In the crystal structure of the sample of Example 3, the bond length of Ba-O is 2.7Ǻ~2.95Ǻ; the bond length of Ba-S is 3.15-3.30Ǻ; the bond length of OS is 2.95Ǻ~3.10Ǻ; the bond length of Zn-O is 1.95Ǻ~2.10Ǻ; and the bond length of Zn-S is 2.25Ǻ~2.40Ǻ.

[0079] Taking the sample of Example 2 as an example, the morphology and element distribution of the sample of Example 2 were tested by scanning electron microscopy. The results showed that the sample of Example 2 exhibited a regular rod-shaped crystal structure with an average length of about 8×10 3 μm~12×10 3 μm, with a diameter of about 5×10 2 μm, such as Figure 2 .

[0080] like Figure 1 As shown in (e), the crystal structure of the sample of Example 2 exhibits polar layered structural characteristics on the ab plane, which has a significant impact on the rod-shaped growth pattern of the crystal. Some crystal rods with thinner diameters exhibit spontaneous bending to form ring-shaped or semi-ring-shaped 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 one-dimensionally preferentially along the c-axis direction, rather than being formed by two-dimensional sheet curling. Further observation revealed that the MZnOS crystal rods exhibited a typical hexagonal prism geometry with clear and sharp edges, which further proved from a morphological perspective that the MZnOS crystal rods tended to grow one-dimensionally preferentially along the c-axis direction. Energy dispersive X-ray spectroscopy element mapping confirmed that Sr, Zn, O and S were uniformly distributed in the MZnOS crystal rods, proving that their chemical composition was uniformly distributed.

[0081] Test 2: Fluorescence performance analysis.

[0082] Photoluminescence emission spectra, photoluminescence excitation spectra, afterglow emission spectra, afterglow decay curves, and thermoelectric curves were recorded using a spectrometer. In addition to a xenon lamp, various other illumination sources were used, including a 5W 365nm UV lamp, an 808nm laser with adjustable power from 0W to 2W, and a 980nm laser with adjustable power from 0W to 5W. Thermoelectric curves were measured over a temperature range of 25°C to 300°C, with a heating rate of 1°C / s. Prior to measuring the afterglow decay and thermoelectric curves, the sample was heated to 500°C to thermally clean the traps and ensure that trapped carriers were emptied. All spectra were corrected for the spectral morphology of the light source. All thermoelectric curve measurements were performed under identical test conditions for comparison. Images of the samples and the luminescence phenomena were captured using a Canon camera. Spectral measurements during the analysis and detection process were performed at room temperature. Prior to measuring the afterglow emission spectra, afterglow decay curves, and thermoelectric curves, the sample was pre-irradiated with UV light of the corresponding wavelength for 5 minutes.

[0083] The optical photographs of the blue-green photoluminescence and green afterglow luminescence of the samples of Examples 1 to 3 under ultraviolet light excitation were compared and analyzed. Figure 3 The results show that under and after 254nm UV light irradiation, the sample of Example 2 exhibits the strongest photoluminescence and long afterglow intensity; while the sample of Example 1 has almost no visible afterglow phenomenon, which may be attributed to its relatively wide band gap and higher carrier mobility.

[0084] The electronic band structure and state density distribution of the samples of Examples 1 to 3 were analyzed. Figures 4 to 6 . The results show that the samples of Example 1 and Example 2 have direct band gaps, while the sample of Example 3 has an indirect band gap. M = Ca, Sr or Ba, and as the atomic number of the alkaline earth metal M increases, the bandwidth decreases from 3.79 eV to 3.58 eV and 3.29 eV. From the orbital components of the three samples in the total density of states, 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 tend to be 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 exhibit energy windows of approximately 2 eV and 1 eV, respectively, indicating that electrons and holes have smaller effective masses and larger ion mobility.

[0085] The effective masses of electrons and holes of the samples of Examples 1 to 3 are further calculated, as Figures 7 to 9 , where m e represents the effective mass of the electron; m hThe results show that the effective mass of electrons and holes in the three samples exhibit strong anisotropy. The effective mass observed along the c-axis is the smallest. When a 10% stress is applied along the c-axis, the effective mass of carriers along the c-axis increases sharply due to structural distortion, as shown in Figure 2. Figures 10 to 12 , which means that the applied stress may lead to direct recombination of interlayer electron-hole pairs to emit light.

[0086] In order to reveal the trap characteristics and control mechanism of the afterglow characteristics of the samples of Examples 1 to 3, the samples were pre-irradiated with 365nm ultraviolet light for 5 minutes, and then the charging light source was turned off and the thermal release curve of the samples was measured for 1 minute. Figure 13 The results show that the sample of Example 2 has the highest trap density and deeper trap distribution, which explains why the strongest and brightest afterglow is obtained in the sample of Example 2 due to its high density of energy storage traps. The thermoluminescence properties of the samples of Examples 1 to 3 are shown in Table 2.

[0087] Table 2 Thermoluminescence properties of samples of Examples 1 to 3

[0088] After irradiating the sample of Example 2 with 254 nm ultraviolet light, it was found that some of the thinner rods, rings, or half-rings emitted bright blue light, while other thicker rods emitted green light, such as Figure 14 After the excitation light is turned off, all SrZnOS crystal rods emit green afterglow, as shown in Figure a. Figure 14 Figure b.

[0089] 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 showed blue luminescence, such as Figure 15 Figure a shows that after aging in air for a period of time, the number of blue crystal rods of SrZnOS crystal rods gradually decreases, while the number of green crystal rods increases. In addition, under 365nm ultraviolet light, in addition to the blue-green photoluminescent crystal rods, several orange photoluminescent crystal rods or zero-dimensional particles can also be observed, such as Figure 15 After the irradiation source is turned off, all individual crystal rods or particles will emit a green afterglow, such as Figure 14 and Figure 15 .

[0090] Considering photon communication, the photon transmission characteristics of single crystal rod, physically contacted crystal rod, crystal rod ring, half ring or broken spliced ​​ring in the sample of Example 2 are further studied. Figure 16 As shown. The excitation wavelength and pre-irradiation wavelength are 365nm. Figure 16When 365nm ultraviolet light is applied to a single crystal rod or to one end of a crystal rod that is physically in contact with it, the naked eye can observe that photoluminescence is smoothly transported within the crystal rod and at its intersection. Similarly, photoluminescence in the ring is transmitted unimpeded along the waveguide ring. Even after the charging light source is turned off, when heating or laser stimulation is applied to a single crystal rod, the junction of two crystal rods, or the ring, half ring, or spliced ​​ring formed by the crystal rods, the long afterglow, thermally stimulated luminescence, and optically stimulated luminescence follow the same transport laws along the waveguide. That is, multimode fluorescence can all be transmitted from the excitation point along the length of the crystal rod without significant leakage, indicating the great application potential of these crystal rods in photonic devices such as optical fibers, waveguides, and laser crystals.

[0091] The specific spectral components are analyzed as follows: Figure 17 The photoluminescence emission spectrum of the sample of Example 2 consists of a green band with a peak at 536 nm / 2.31 eV and a blue band at 472 nm / 2.62 eV. Therefore, these single crystal rods produce blue-green emission under light excitation in the range of 350 nm to 450 nm.

[0092] exist Figure 18 In the example 2, the photoluminescence at 536 nm was monitored, and the excitation spectrum had two peaks at 365 nm / 3.39 eV and 400 nm / 3.10 eV; while the photoluminescence at 472 nm was monitored, the excitation spectrum had a peak at 365 nm. Figure 19 The afterglow emission spectrum shown in Figure 3 has only a single peak emission at 515 nm / 2.41 eV. To facilitate comparison of the multimode fluorescence of the sample in Example 2, including the peak characteristics of the photoluminescence emission spectrum, photoluminescence excitation spectrum, and afterglow emission spectrum, the various spectral peaks are shown along with the afterglow duration in Table 3. Table 3 shows that the peaks of the afterglow emission spectrum and the photoluminescence emission spectrum are inconsistent, suggesting that the afterglow center and the photoluminescence center may be different centers or transitions between different fluorescence energy levels of the same center. Furthermore, when monitoring different photoluminescence fluorescence peaks, the peaks of the photoluminescence excitation spectrum are also inconsistent, suggesting that each photoluminescence peak also originates from different luminescence centers or transitions between different energy levels of the same luminescence center. Based on spectral analysis and electronic band structure, the multimode fluorescence originates from transitions between two specific energy levels of a specific luminescence center, which are indicated in the figure in the abstract.

[0093] Table 3 Comparison of spectral peaks and afterglow luminescence time of the samples of Example 2

[0094] Note: “-” means no or not tested. mon Indicates the fluorescence wavelength of fluorescence monitoring; λ ex represents the excitation wavelength; λ charge Indicates the pre-irradiation wavelength.

[0095] The sample of Example 2 was pre-irradiated with 365nm ultraviolet light for 5 minutes and then the temperature-dependent luminescence characteristics were tested. Figures 20 to 23 As shown in Figure 2. Within the temperature range studied, the fluorescence with a photoluminescence emission peak at 472 nm and the afterglow emission spectrum with a peak at 515 nm decrease monotonically with increasing temperature, while the fluorescence with a photoluminescence emission peak at 536 nm reaches a peak at 50 ° C and then decreases with increasing temperature, as shown in Figure 2. Figure 20 and Figure 21 The different temperature dependences mean that these emission peaks originate from different energy level transitions. The afterglow decay curve is related to temperature and decays the slowest at 80°C. Figure 22 The thermal release curve of the afterglow of the sample of Example 2 at 515nm is monitored. The thermal release curve shows a single peak characteristic with a peak at about 80°C. Figure 23 This explains why the afterglow decay rate is slowest at 80°C. As the temperature rises, the peak of the thermal emission curve gradually moves toward higher temperatures, and the thermally stimulated luminescence intensity decreases rapidly.

[0096] In order to further prove the trap type, the precursor powders of SrCO3 and ZnS mixed and ground thoroughly according to the chemical proportion were placed in a high-temperature annealing furnace, the annealing atmosphere was adjusted to a reducing atmosphere or an air atmosphere, and then annealed at 900°C for 10 hours to prepare 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 showed that both samples did not obtain long afterglow, and it was visible to the naked eye that these precursor powders did not grow into one-dimensional long rods under an inert atmosphere, suggesting the importance of the annealing atmosphere. By comparing the samples of Example 2, Comparative Example 1 and Comparative Example 2 prepared under the three atmosphere conditions, it can be inferred that thermal Schottky oxygen vacancies, i.e., V O •• and V Zn "Coexisting defects are responsible for afterglow energy storage, which enables them to compensate each other's charges, reduce the system energy, and make the compound more stable. The oxygen vacancy contains three defect state energy levels, namely 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 gain a deeper understanding of the charge and discharge process of the trap, such as Figure 24 and Figure 25The intensities of both blue and green photoluminescence emissions slowly increase with increasing illumination time. This confirms that the recombination probabilities of the conduction band → oxygen vacancy defect state and the doubly positively charged oxygen vacancy defect state → singly positively charged oxygen vacancy defect state increase due to the increase in the number of electrons in the conduction band and doubly positively charged oxygen vacancy defect state. These results indicate that the valence state of the doubly positively charged oxygen vacancy does not change or changes negligibly during the afterglow process, indirectly supporting the conclusion that the afterglow originates from the transition from the doubly positively charged sulfur vacancy defect state to the doubly negatively charged zinc vacancy defect state.

[0097] Structure determines properties. The crystal growth mechanism of the sample of Example 2 was studied. Figure 26 The sample of Example 2 has a layered polar structure similar to a micro-unit NPN diode. The micro-unit NPN type is represented by double positively charged oxygen vacancies-double negatively charged zinc vacancies-double positively charged sulfur vacancies, that is, V O •• -V Zn "-V S •• The photogenerated carriers are stored in different NPN layers. Under external disturbances, electrons jump from high energy levels to low energy levels, recombine with holes, and emit light.

[0098] The schematic diagram of the mechanism of the photoluminescence, long afterglow, thermally stimulated luminescence and light-stimulated luminescence of the sample of Example 2 is shown in Figure 27 Under 254nm / 365nm ultraviolet light irradiation, electrons from the valence band, zinc vacancy defect state or ground state V O Transition to the conduction band, which is recorded as process ①. Some of these electrons return from the conduction band to oxygen-related defect states through charge transfer, resulting in CB-V O and V O • -VB vacancy transition, namely process ② and process ③, produces blue and green photoluminescence, respectively. Another part of the electrons are captured by the doubly positively charged sulfur vacancy; under thermal stimulation or light stimulation, the charge is transferred from the doubly positively charged sulfur vacancy defect state to the doubly negatively charged zinc vacancy defect state, producing green long afterglow emission, recorded as process ④. Therefore, the photoluminescence mainly comes from the correlation transition between the conduction band and the oxygen vacancy defect energy level. The long afterglow is produced by the electron transfer transition between the doubly positively charged sulfur vacancy defect state to the doubly negatively charged zinc vacancy defect state. Therefore, photoluminescence and long afterglow occur through different carrier transport pathways. Therefore, it can be respectively from CB→V O 、V O •• →V O and V O • → The VB transition vacancy is allocated to blue, green and weak red photoluminescence. With the help of bandpass filters, the three primary colors of blue, green and red can be obtained respectively, such as Figure 28 As shown. The long afterglow originates from the transition from the doubly positively charged sulfur vacancy defect state to the doubly negatively charged zinc vacancy defect state. Therefore, it can be concluded that in the thick crystal rod, V O •• is the main form of defects, and in thin crystal rods, V O • There has been an increase.

[0099] Considering the optoelectronic properties and one-dimensional transport properties of one-dimensional crystal rods, these crystal rods have great application potential in optoelectronic materials. Figure 29 The study found that when these crystal rods were placed in a water environment and subjected to sound waves, they completely floated on the water surface, indicating that they have extremely low density. Furthermore, in a water environment, their photoluminescence and afterglow properties were completely unaffected, demonstrating that they can function normally in harsh environments such as high heat and high humidity. Therefore, the sample of Example 2 is lightweight and easy to pick up with a single electrode, making it suitable for use in device components.

[0100] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A self-activated long afterglow one-dimensional crystal rod luminescent material, characterized in that: The chemical expression 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-shaped geometric configuration; 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=5.6Å, b=3.7Å, c=9.8Å; When M is Sr, the lattice parameters are a = 5.7Å, b = 3.8Å, c = 10.0Å; When M is Ba, the lattice parameters are a=5.9Å, b=3.9Å, and c=10.3Å.

2. The self-activated long afterglow one-dimensional crystal rod luminescent material according to claim 1, 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 a hexagonal system formed by connecting ZnS3O tetrahedrons and distorted MO3S3 octahedrons.

3. The self-activated long afterglow one-dimensional crystal rod luminescent material according to claim 1, characterized in that: 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 by vertices to form a chain structure parallel to the a-axis and the c-axis, and stacked into ZnO2S2 tetrahedron layers, and the interlayers of the ZnO2S2 tetrahedron layers are composed of eight-coordinated Ba 2+ Ions are separated to form a three-dimensional layered crystal structure of the orthorhombic system.

4. The self-activated long afterglow one-dimensional crystal rod luminescent material according to claim 1, characterized in that: 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, with a diameter of 5.0×10 2 μm.

5. A method for preparing a self-activated long-lasting one-dimensional crystal rod luminescent material, characterized in that: The following steps are involved: M 2+ The inorganic acid salt corresponding to the ion and ZnS are used as raw materials, which are ground and then annealed in an inert atmosphere to obtain the self-activated long afterglow one-dimensional crystal rod luminescent material according to any one of claims 1 to 4; wherein M is Ca, Ba or Sr.

6. The method for preparing the self-activated long afterglow one-dimensional crystal rod luminescent material according to claim 5, characterized in that: The inert atmosphere was a nitrogen atmosphere.

7. The method for preparing the self-activated long afterglow one-dimensional crystal rod luminescent material according to claim 5, characterized in that: The annealing temperature is 850° C. to 1000° C., and the annealing time is 5 h to 6 h.

8. The method for preparing the self-activated long afterglow one-dimensional crystal rod luminescent material according to claim 5, characterized in that: M 2+ The inorganic acid salt corresponding to the ion is M 2+ ions corresponding to carbonate or nitrate.

9. Application of a self-activated long-lasting one-dimensional crystal rod luminescent material as a stimulus-responsive optical functional material for multi-mode luminescence, characterized in that: The self-activated long-lasting one-dimensional crystal rod luminescent material is the self-activated long-lasting one-dimensional crystal rod luminescent material according to any one of claims 1 to 4.

10. Use of the self-activated long afterglow one-dimensional crystal rod luminescent material according to claim 9 as a stimulus-responsive optical functional material for multi-mode luminescence, characterized in that: The multi-mode luminescence includes photoluminescence, long afterglow, light-stimulated luminescence and thermally stimulated luminescence.

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