Manganese ion-activated green long afterglow nanoparticles and preparation method thereof

Abstract

This invention discloses a manganese ion-activated green long afterglow nanoparticle and its preparation method, belonging to the field of afterglow material technology. The method includes: dissolving zinc acetate in water to obtain solution A; dissolving germanium oxide and sodium hydroxide in water at a molar ratio of 1:4 to obtain solution B; adding solution B dropwise to solution A, adjusting the pH to 7.5-9, placing the solution in a high-pressure reactor, heating to 175-190℃, and obtaining initial zinc germanate nanoparticles through a hydrothermal reaction; mixing and grinding the initial zinc germanate nanoparticles with manganese dioxide at a mass ratio of 400:0.3-1, then heat-treating the mixture at 650-750℃ under vacuum and inert gas protection, and finally grinding it after cooling to obtain manganese ion-activated green long afterglow nanoparticles. The zinc manganese germanate rod-shaped long afterglow nanoparticles prepared by this invention do not contain rare earth elements, have a diameter of 50-70 nm and a length of 50-800 nm, and can produce green light long afterglow emission for more than 240 minutes after X-ray irradiation, with the emission peak located at 530 nm. They have broad application prospects in the fields of non-destructive testing, nanomedicine and micro-nano optoelectronic devices.

Description

Technical Field

[0001] This invention relates to the field of afterglow materials technology, specifically to a manganese ion-activated zinc germanate-based green long afterglow nanoparticle and its preparation method. Background Technology

[0002] Afterglow materials are a class of luminescent materials capable of storing light energy under excitation by different wavelengths of light (such as ultraviolet-visible-near-infrared light and high-energy photons) and slowly releasing the stored light energy after excitation stops, forming a continuous light emission. Based on this unique energy storage and slow release characteristic, afterglow materials have broad application prospects in emergency indication, safety signage, optical information storage, bioimaging, and optoelectronic devices. In particular, combining afterglow materials with organic polymers can yield flexible afterglow films. Using X-ray transmission excitation, the delayed afterglow emission of these films can achieve non-destructive imaging of equipment or biological organs with irregular curved surfaces, providing a non-destructive testing technique for reverse engineering of military equipment and high-precision instruments. Furthermore, afterglow materials can also serve as in-situ "photocells." Under repeated excitation and charging by highly penetrating X-rays, they can penetrate deep biological tissues to achieve long-term photodynamic therapy and drug metabolism tracking. They can also provide continuous in-situ driving energy for enclosed equipment systems without the need for complex power supply systems. Therefore, afterglow materials based on X-ray irradiation can be used to develop green, rechargeable in-situ energy systems, which have significant application potential in the fields of nanobiomedicine and optoelectronic device manufacturing.

[0003] Currently, rare earth-based afterglow materials exhibit high brightness and stable luminescence properties, such as Eu. 2+ Dy 3+ 、Tb 3 + Fluoride-doped afterglow materials, etc. However, rare earth elements are non-renewable. In order to conserve rare earth resources and meet the demand for afterglow materials in the above-mentioned application fields, it is urgent to develop a series of high-performance afterglow materials that do not contain rare earth elements.

[0004] Furthermore, to meet the demands of nanomedicine and the fabrication of advanced micro-nano devices (nanorobotics) for afterglow-driven small-sized, long-lasting nanomedicines and small-sized photovoltaic cells, there is an urgent need to develop high-performance afterglow nanomaterials. Existing research indicates that divalent manganese ions (Mn...) 2+ Activated germanate oxide materials typically exhibit long green light persistence, and their sustained high-energy photon output offers the potential for efficiently driving nanomedicines and optoelectronic devices. However, to achieve long-term driving of nanomedicines and micro / nano devices, nano-sized Mn... 2+The afterglow performance of activated afterglow materials still needs further improvement. Generally, high-temperature heat treatment above 1000℃ is an effective method to increase the number of internal traps and improve the luminescence performance of afterglow materials. However, excessively high heat treatment temperatures can lead to the agglomeration and growth of nanoparticles, making it difficult to obtain small-sized afterglow nanomaterials with regular morphology and uniform size. Meanwhile, tetravalent manganese ions have a relatively stable valence state, and their oxides are commonly used manganese sources. They generally require high temperatures above 1000℃ and strong reducing conditions to be reduced to the lower valence state of divalent manganese ions. Therefore, how to obtain small-sized divalent manganese ions (Mn²⁺) at lower temperatures is a key challenge. 2+ The activation of high-brightness afterglow materials remains a technical challenge that urgently needs to be addressed.

[0005] In summary, a Mn catalyst with low reaction temperature, uniform particle size, no rare earth elements, and excellent long afterglow performance with green light has been developed. 2+ The preparation method of ion-activated nanoparticles has important scientific research significance and practical application value. Summary of the Invention

[0006] The technical problem to be solved by this invention is: how to prepare non-rare earth-based zinc manganese germanate nanoparticles with uniform morphology, small size and strong afterglow emission by combining the improvement of heat treatment process with the adjustment of impurity doping strategy.

[0007] To address the aforementioned technical problems, this invention provides a method for preparing manganese ion-activated green long-afterglow nanoparticles, comprising the following steps:

[0008] (1) Dissolve zinc acetate in deionized water and stir thoroughly until zinc acetate is fully dissolved to obtain solution A; place germanium oxide and sodium hydroxide in deionized water, heat to 75-85℃ and stir continuously until germanium oxide and sodium hydroxide are completely dissolved to obtain solution B;

[0009] (2) Add solution B dropwise to solution A and stir continuously to obtain a pre-reaction solution; then adjust the pH of the pre-reaction solution to between 7.5 and 9 and stir continuously until a uniform white suspension is formed;

[0010] (3) The white suspension was transferred into a high-pressure reactor with a Teflon liner, heated to 175-190°C, and kept at the temperature for 4-24 hours. After the reactor was cooled to room temperature, the reaction product was taken out, washed, dried, and ground to obtain the initial zinc germanate nanoparticles (Zn2GeO4).

[0011] (4) Take the initial zinc germanate nanoparticles obtained in step (3) and mix them with manganese dioxide (MnO2) at a mass ratio of 400: 0.3~1. Grind the mixed powder material to make the nanoparticles and manganese dioxide powder evenly mixed.

[0012] (5) Place the mixed powder obtained in step (4) in a vacuum tube furnace and evacuate to a vacuum degree of 7×10⁻⁶. -4 After the pressure drops below Pa, the temperature is gradually increased, and heat treatment is carried out at 650–750℃ for 0.8–1.6 hours under inert gas protection, with the vacuum level maintained at 5 × 10⁻⁶ throughout the heat treatment process. -2 Below Pa;

[0013] (6) After heat treatment, the furnace is cooled to room temperature under inert gas protection, with the vacuum level maintained at 5×10⁻⁶ during the cooling process. -2 Below Pa;

[0014] (7) Grind the cooled product to obtain Mn 2+ Activated zinc manganese germanate rod-shaped long afterglow nanoparticles (Zn2GeO4:Mn 2+ ).

[0015] Further, in step (1), germanium oxide and sodium hydroxide are prepared in a molar ratio of 1:4.

[0016] Further, in step (2), solution B is added dropwise to solution A so that the molar ratio of Zn ions to Ge ions in the mixed solution is 2:1; the pH value is preferably adjusted to 8.

[0017] Further, in step (4), the mass ratio of zinc germanate nanoparticles to manganese dioxide powder is any one of 400:0.3, 400:0.4, 400:0.5, 400:0.6, 400:0.7, 400:0.8, 400:0.9, or 400:1.

[0018] Furthermore, in step (4), the grinding time is 10 to 30 minutes.

[0019] Furthermore, the inert gas mentioned in steps (5) and (6) is argon.

[0020] Furthermore, in step (7), the grinding time is 5 to 10 minutes.

[0021] The zinc manganese germanate rod-shaped long afterglow nanoparticles prepared by the above method have a diameter of 50-70 nm and a length in the range of 50 nm-800 nm. After being irradiated with X-rays for 5 minutes, they can obtain green light long afterglow emission for more than 240 minutes, with the emission peak located at 530 nm.

[0022] The working principle of this invention is as follows:

[0023] (1) Based on the low saturated vapor pressure under vacuum heat treatment conditions, heat treatment of zinc germanate nanoparticles at a lower temperature can cause a large amount of zinc and germanium elements to volatilize and form defects inside the material, thereby improving the afterglow emission performance and avoiding the aggregation and growth of nanoparticles.

[0024] (2) Relying on the reducing ionic atmosphere formed by the volatilized zinc and germanium elements within the zinc germanate nanoparticles and the weak reducing environment of the vacuum, supplemented by argon as a protective gas, the tetravalent manganese ions (Mn) in manganese dioxide are reduced. 4+ ) is reduced to divalent manganese ions (Mn 2+ The zinc germanate nanoparticles are introduced into the zinc germanate long afterglow nanoparticle matrix through a cation diffusion process, thereby enabling the zinc germanate manganese nanoparticles to exhibit ultra-long green afterglow emission after X-ray excitation, with the strongest afterglow emission peak located at approximately 530 nm.

[0025] The present invention has the following beneficial effects:

[0026] (1) The zinc manganese germanate rod-shaped long afterglow nanoparticles prepared by the present invention can produce green light long afterglow emission for more than 240 minutes after being irradiated with X-rays for 5 minutes. The strongest position of the afterglow emission peak is located at 530 nm, and the afterglow performance is excellent.

[0027] (2) The present invention employs a low-vacuum environment with an inert gas as a protective gas for low-temperature heat treatment during the preparation process. Relying on the reducing ion atmosphere formed by the volatilized zinc and germanium elements within the zinc germanate nanoparticles and the weak reducing environment of the vacuum, the tetravalent manganese ions in manganese dioxide can be effectively reduced to divalent manganese ions. While improving the afterglow performance of the nanoparticles, the present invention effectively controls the aggregation phenomenon of rod-shaped nanoparticles, resulting in rod-shaped nanoparticles with a diameter of less than 70 nm, a length of less than 800 nm, and a regular morphology.

[0028] (3) The zinc manganese germanate long afterglow nanoparticles prepared by this invention do not contain rare earth elements, thus avoiding the consumption of rare earth resources and having the advantages of low cost and environmental friendliness. At the same time, this invention reduces the heat treatment temperature for preparing high-brightness afterglow materials and reducing tetravalent manganese ions to divalent manganese ions by more than 200°C, which has the advantage of energy saving.

[0029] (4) Based on the ultralong green light long-afterglow characteristics of the rod-shaped long-afterglow nanoparticles of zinc manganese germanate prepared in this invention, these nanoparticles can be applied to medical applications such as afterglow-driven long-term photodynamic therapy and related nanomedicines. This series of afterglow nanomedicines has low cost and long-term effects, which can provide new technology references for daily home physiotherapy, which is conducive to reducing the burden and improving the efficiency of the public medical security system and improving the quality of daily life of patients. At the same time, it can continuously output high-energy photons without real-time excitation, and can be used as an in-situ "photocell" to drive micro-nano optoelectronic devices. Based on the high-penetration excitation of X-rays, this in-situ "photocell" can achieve non-contact in-situ charging without complex electromagnetic induction circuits, and is not limited by the obstruction of general biological tissues, plastic polymers and thin iron sheets. Therefore, the rod-shaped long-afterglow nanoparticles of zinc manganese germanate prepared in this invention can be used as a carrier for the development of multifunctional drugs and diagnostic and therapeutic technologies, and can also be used as an in-situ energy donor for micro-nano devices. Attached Figure Description

[0030] Figure 1 The X-ray diffraction pattern of zinc manganese germanate long afterglow nanoparticles with a Zn2GeO4:MnO2 mixed mass ratio of 400:0.4 (x=0.4) prepared in Example 1 is shown.

[0031] Figure 2 Scanning electron microscope (SEM) image of zinc manganese germanate long afterglow nanoparticles with a Zn2GeO4:MnO2 mixed mass ratio of 400:0.4 (x=0.4) prepared in Example 1;

[0032] Figure 3 The emission spectrum of zinc manganese germanate long afterglow nanoparticles with a Zn2GeO4:MnO2 mixed mass ratio of 400:0.4 (x=0.4) prepared in Example 1 under X-ray excitation;

[0033] Figure 4 The green light long afterglow decay curve of the zinc manganese germanate long afterglow nanoparticles with a Zn2GeO4:MnO2 mixed mass ratio of 400:0.4 (x=0.4) prepared in Example 1 after X-ray irradiation for 5 minutes.

[0034] Figure 5 The X-ray diffraction pattern of zinc manganese germanate long afterglow nanoparticles with a Zn2GeO4:MnO2 mixed mass ratio of 400:1 (x=1) prepared in Example 2 is shown.

[0035] Figure 6 The image shows a scanning electron microscope (SEM) image of zinc manganese germanate long afterglow nanoparticles with a Zn2GeO4:MnO2 mixed mass ratio of 400:1 (x=1) prepared in Example 2.

[0036] Figure 7The emission spectrum of zinc manganese germanate long afterglow nanoparticles with a Zn2GeO4:MnO2 mixed mass ratio of 400:1 (x=1) prepared in Example 2 under X-ray excitation;

[0037] Figure 8 The image shows the green light long afterglow decay curve of the zinc manganese germanate long afterglow nanoparticles prepared in Example 2 with a Zn2GeO4:MnO2 mixed mass ratio of 400:1 (x=1) after irradiation with X-rays for 5 minutes. Detailed Implementation

[0038] The technical solution of the present invention will be described in detail below with reference to specific embodiments. It should be understood that these embodiments are only for illustrating the present invention and are not intended to limit the scope of the present invention. All technologies implemented based on the above content of the present invention fall within the scope of the present invention.

[0039] Example 1

[0040] (1) Take 7.3392g of zinc acetate and place it in a beaker containing 200mL of deionized water. Stir at room temperature for 10 minutes until the zinc acetate is fully dissolved to obtain a transparent solution A. According to the molar ratio of germanium oxide to sodium hydroxide of 1:4, take 2.0928g of germanium oxide and 0.8g of sodium hydroxide and place them in a beaker containing 100mL of deionized water. Stir at 80℃ for 10 minutes until the germanium oxide is completely dissolved to obtain a clear solution B.

[0041] (2) Slowly add solution B to solution A to make the molar ratio of Zn ions to Ge ions in the mixed solution 2:1, and obtain the pre-reaction solution. Then, slowly add ammonia solution to the reaction solution to adjust the pH value of the reaction solution to 8, and continue stirring until the reaction solution becomes a uniform white suspension.

[0042] (3) The white suspension was transferred into a high-pressure reactor with a Teflon liner. The suspension in the reactor was heated to 185°C and kept at that temperature for 8 hours. After the reactor cooled naturally to room temperature, the reaction product was taken out, washed with water three times, dried and ground to obtain the initial zinc germanate nanoparticles (Zn2GeO4).

[0043] (4) Take 0.003g of manganese dioxide and 3g of initial zinc germanate nanoparticles in a mortar and grind for 20 minutes in a mass ratio of 400:0.4 to make the nanoparticles and manganese dioxide powder evenly mixed.

[0044] (5) Place the ground mixed powder in a vacuum tube furnace and evacuate to a vacuum level of 6×10⁻⁶. -4 After the pressure drops below Pa, the temperature is increased, and heat treatment is carried out at 700℃ for 1 hour, with the vacuum level maintained at 3×10⁻⁶ throughout the heat treatment process. -2 The pressure is below Pa, and high-purity argon is introduced as a protective gas.

[0045] (6) After the heat treatment, the sample was cooled to room temperature in the furnace, and the vacuum degree inside the furnace was maintained at 3×10 during the cooling process. -2 The pressure is below Pa, and high-purity argon is introduced as a protective gas.

[0046] (7) Place the powder sample cooled to below 25°C in an agate mortar and grind for 5 minutes to obtain Mn. 2+ Activated zinc manganese germanate rod-shaped long afterglow nanoparticles (Zn2GeO4:Mn 2+ ).

[0047] See appendix Figures 1 to 4 As shown, the rod-shaped nanoparticles prepared in this embodiment have narrow X-ray diffraction peaks and good crystallinity; their diameter is about 50-60 nm and their length is in the range of 50 nm-300 nm; under X-ray excitation, they can obtain green light emission with the maximum emission intensity at 530 nm; after X-ray irradiation for 5 minutes, they can obtain green light long afterglow emission for more than 240 minutes.

[0048] Example 2

[0049] (1) Take 11.0088g of zinc acetate and place it in a beaker containing 300mL of deionized water. Stir at room temperature for 10 minutes until the zinc acetate is completely dissolved to obtain a clear solution A. Then, according to the molar ratio of germanium oxide to sodium hydroxide of 1:4, take 3.1392g of germanium oxide and 1.2g of sodium hydroxide and place them in a beaker containing 150mL of deionized water. Stir at 85℃ for 15 minutes until the germanium oxide is completely dissolved to obtain a clear solution B.

[0050] (2) Slowly add solution B to solution A to make the molar ratio of Zn ions to Ge ions in the mixed solution 2:1, and obtain the pre-reaction solution. Then, slowly add ammonia solution to the reaction solution to adjust the pH value of the reaction solution to 8.5, and continue stirring until the reaction solution becomes a uniform white suspension.

[0051] (3) The white suspension was transferred into a high-pressure reactor with a Teflon liner. The suspension in the reactor was heated to 180°C and kept at that temperature for 10 hours. After the reactor cooled naturally to room temperature, the reaction product was taken out, washed with water three times, dried and ground to obtain the initial zinc germanate nanoparticles (Zn2GeO4).

[0052] (4) Take 0.01g of manganese dioxide and 4g of initial zinc germanate nanoparticles in a mortar and grind them for 30 minutes at a mass ratio of 400:1 to make the nanoparticles and manganese dioxide powder evenly mixed.

[0053] (5) Place the ground mixed powder in a vacuum tube furnace and evacuate to a vacuum level of 5×10⁻⁶. -4After the pressure drops below Pa, the temperature is increased, and heat treatment is carried out at 750℃ for 1.2 hours. During the heat treatment process, the vacuum degree is maintained at 4×10⁻⁶. -2 The pressure is below Pa, and high-purity argon is introduced as a protective gas.

[0054] (6) After the heat treatment, the sample was cooled to room temperature in the furnace, and the vacuum degree inside the furnace was maintained at 4×10 during the cooling process. -2 The pressure is below Pa, and high-purity argon is introduced as a protective gas.

[0055] (7) Place the powder sample cooled to below 25°C in an agate mortar and grind for 10 minutes to obtain Mn. 2+ Activated zinc manganese germanate rod-shaped long afterglow nanoparticles (Zn2GeO4:Mn 2+ ).

[0056] See appendix Figures 5 to 8 As shown, the rod-shaped nanoparticles prepared in this embodiment have a narrower half-width at half-maximum (WHM) in X-ray diffraction, indicating better crystallinity; their diameter is approximately 50–60 nm, and their length is in the range of 100 nm–800 nm; under X-ray excitation, they can obtain green light emission with the maximum emission intensity at 530 nm; after 5 minutes of X-ray irradiation, the long afterglow emission of green light is also more than 240 minutes.

[0057] In step 5, the heat treatment temperature and time directly affect the morphology of the nanoparticles. Under the preparation conditions of this invention, the higher the temperature and the longer the time, the larger the synthesized particles, that is, the longer the length of the rod-shaped nanoparticles.

Claims

1. A method for preparing manganese ion-activated green long-afterglow nanoparticles, characterized in that: Includes the following steps: (1) Dissolve zinc acetate in deionized water and stir thoroughly until zinc acetate is fully dissolved to obtain solution A; place germanium oxide and sodium hydroxide in deionized water, heat to 75-85℃ and stir continuously until germanium oxide and sodium hydroxide are completely dissolved to obtain solution B; (2) Add solution B dropwise to solution A and stir continuously to obtain a pre-reaction solution; then adjust the pH of the pre-reaction solution to between 7.5 and 9 and stir continuously until a uniform white suspension is formed; (3) Transfer the white suspension into a high-pressure reactor, heat it to 175-190 °C, and keep it at the temperature for 4-24 hours. After the reactor is cooled to room temperature, take out the reaction product, wash, dry, and grind it to obtain the initial zinc germanate nanoparticles. (4) Take the initial zinc germanate nanoparticles obtained in step (3) and mix them with manganese dioxide at a mass ratio of 400: 0.3~1. Grind the mixed powder material to make the nanoparticles and manganese dioxide powder evenly mixed. (5) The mixed powder obtained in step (4) is placed in a vacuum tube furnace, vacuumed to a vacuum degree of 7 x 10 -4 Pa or below, and heated at 650-750°C for 0.8-1.6 hours under inert gas protection, with the vacuum degree maintained at 5 x 10 -2 Pa or below during the heat treatment. (6) After the heat treatment, the furnace is cooled to room temperature under the protection of inert gas, and the vacuum degree is maintained at 5 x 10 -2 Pa during the cooling process. Pa below; (7) grinding the cooled product to obtain Mn 2+ Activated zinc-germanate manganese rod-like long afterglow nanoparticles.

2. The method for preparing manganese ion-activated green long-afterglow nanoparticles according to claim 1, characterized in that: In step (1), germanium oxide and sodium hydroxide are prepared in a molar ratio of 1:

4.

3. The method for preparing manganese ion-activated green long-afterglow nanoparticles according to claim 1, characterized in that: In step (2), solution B is added dropwise to solution A so that the molar ratio of Zn ions to Ge ions in the mixed solution is 2:

1.

4. The method for preparing manganese ion-activated green long-afterglow nanoparticles according to claim 1, characterized in that: In step (4), the mass ratio of zinc germanate nanoparticles to manganese dioxide powder is any one of 400:0.3, 400:0.4, 400:0.5, 400:0.6, 400:0.7, 400:0.8, 400:0.9, or 400:

1.

5. The method for preparing manganese ion-activated green long-afterglow nanoparticles according to claim 1, characterized in that: The inert gas mentioned in steps (5) and (6) is argon.

6. A manganese ion-activated green long-afterglow nanoparticle, characterized in that: It is prepared by any one of the preparation methods according to claims 1-5.

7. The manganese ion-activated green long-afterglow nanoparticles according to claim 6, characterized in that: The nanoparticles are rod-shaped with a diameter of 50-70 nm and a length in the range of 50 nm-800 nm. After being irradiated with X-rays for 5 minutes, they can produce a long green afterglow emission of more than 240 minutes, with the strongest afterglow emission peak located at 530 nm.

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