Hydroxyapatite nanowires coated with metal ion-rich amorphous layers and methods of making the same

Abstract

The application provides a hydroxyapatite nanowire coated with a metal ion-rich amorphous layer and a preparation method thereof, and belongs to the technical field of nanometer material preparation, comprising a hydroxyapatite nanowire and a metal ion-rich amorphous layer coated on the surface of the hydroxyapatite nanowire, wherein the length-diameter ratio of the hydroxyapatite nanowire is 500-10000, and the ratio of the diameter of the hydroxyapatite nanowire to the thickness of the metal ion-rich amorphous layer is (5-50):1. The application learns the unique structure of natural tooth enamel, coats a layer of amorphous layer containing iron, aluminum, copper, manganese or zinc metal ions on the outer layer of the hydroxyapatite nanowire, so as to simulate the multi-level structure of the hydroxyapatite nanowire in the natural tooth enamel, and make the hydroxyapatite nanowire have some excellent performances endowed by the metal ions, such as good thermal stability, corrosion resistance and wear resistance.

Description

Technical Field

[0001] This invention relates to the field of nanomaterial preparation technology, specifically to hydroxyapatite nanowires coated with a metal ion-rich amorphous layer and their preparation method. Background Technology

[0002] Tooth enamel is the hardest material in the human body, composed of 96 wt% hydroxyapatite and 4 wt% hydrated protein. Covering the tooth surface, a few millimeters thick, enamel is renowned for its high rigidity, hardness, and viscoelasticity, while also possessing excellent toughness to resist vibrations and impacts during chewing. It achieves a combination of seemingly contradictory mechanical properties such as high hardness, high elasticity, high strength, and high toughness, protecting teeth from external physical and chemical damage. Tooth enamel has a typical multi-level structure, mainly composed of enamel prisms and interenamel matrix. The smallest structural unit of the enamel prism is a single hydroxyapatite nanocrystal, which grows along the c-axis to form linear hydroxyapatite nanocrystals. Between the enamel prisms, there exists a protein-rich organic layer called the "sheath," where the hydroxyapatite crystals are "bound" together by the organic matrix. Further research revealed that there is also an inorganic amorphous interlayer between the hydroxyapatite nanowires. This interface characterization indicates that there are strong chemical bonds between the amorphous layer and the nanowires, which enhances the interfacial connectivity. This multi-level micro-nano structure is the key to the excellent mechanical properties of tooth enamel.

[0003] The fabrication of artificial enamel or enamel restorative materials by mimicking the structure of tooth enamel has great application potential in the biomedical field. Currently, the preparation and morphology control of inorganic amorphous nanomaterials remain quite difficult, and introducing an amorphous interstitial layer that plays a crucial role in mechanical properties to mimic the multi-level structure of tooth enamel remains a significant challenge. Patent publication number CN117246991A discloses a fluorapatite nanorod with a magnesium amorphous layer and its preparation method. This method involves dissolving a soluble salt in water and adding it dropwise. As the nanoclusters randomly attach and crystallize, magnesium ions are displaced to the edges of the nanorods, forming fluorapatite nanorods coated with a magnesium amorphous layer. Professor Guo Lin's research group at Beihang University has developed a method for coating hydroxyapatite nanowires with an amorphous zirconia layer. Using the controlled growth theory based on ice crystals, and with this crystalline / amorphous composite nanowire as the basic structural unit, they achieved macroscopic-scale directed assembly of the amorphous / crystalline composite nanowire and polyvinyl alcohol polymer using a self-designed device. This resulted in the fabrication of HA-based composite materials with an enamel-like structure, thus producing enamel-like materials. However, these methods are all relatively complex, highly susceptible to environmental factors, and have low controllability. Summary of the Invention

[0004] In view of the technical problems existing in the background art, this application provides a hydroxyapatite nanowire coated with a metal ion-rich amorphous layer and its preparation method, aiming to solve the technical problem that the preparation and morphology control of hydroxyapatite nanowire coated with a metal ion-rich amorphous layer are still relatively difficult.

[0005] In a first aspect, embodiments of this application provide a hydroxyapatite nanowire coated with a metal ion-rich amorphous layer, comprising a hydroxyapatite nanowire and a metal ion-rich amorphous layer coated on its surface, wherein the aspect ratio of the hydroxyapatite nanowire is 500~10000, and the ratio of the diameter of the hydroxyapatite nanowire to the thickness of the metal ion-rich amorphous layer is (5~50):1.

[0006] Preferably, the hydroxyapatite nanowires have a diameter of 10~100nm and a length of 100~500μm; the thickness of the metal ion-rich amorphous layer is 1~5nm.

[0007] Preferably, the metal ion includes one of iron, aluminum, copper, manganese, and zinc.

[0008] Secondly, embodiments of this application provide a method for preparing hydroxyapatite nanowires coated with a metal ion-rich amorphous layer, comprising the following steps:

[0009] S1. Disperse hydroxyapatite nanowires in a buffer solution to obtain a hydroxyapatite nanowire suspension.

[0010] S2. Add soluble metal salts to the hydroxyapatite nanowire suspension, stir and react. After the reaction is complete, wash, centrifuge, and freeze-dry to obtain hydroxyapatite nanowires coated with a metal ion-rich amorphous layer.

[0011] Preferably, the buffer solution is an ammonium formate-formic acid buffer solution or a glycine-sodium hydroxide buffer solution, and the pH of the buffer solution is 5.0~9.0.

[0012] Preferably, the concentration of hydroxyapatite nanowires in the hydroxyapatite nanowire suspension is 2~5 g / L.

[0013] Preferably, the dispersion step in step S1 includes placing hydroxyapatite nanowires in a buffer solution, stirring at room temperature for 12-24 hours, and then ultrasonically dispersing them for 30-60 minutes using a power of 600-800W.

[0014] Preferably, in step S2, the metal ion concentration is 0.0001~0.025 mol / L, and the metal ions react with Ca in hydroxyapatite. 2+ The molar ratio is 1:(2~10).

[0015] Preferably, the stirring conditions in step S2 are: stirring at room temperature for 3~24h, and stirring speed of 400~800rpm.

[0016] Thirdly, embodiments of this application provide a tooth enamel restoration material prepared from hydroxyapatite nanowires coated with a metal ion-rich amorphous layer.

[0017] The advantages of this application, which differ from existing technical solutions, include:

[0018] 1. This application, by studying the unique structure of natural tooth enamel, coats the outer layer of hydroxyapatite nanowires with an amorphous layer containing iron-, aluminum-, copper-, manganese-, and zinc-rich metal ions, respectively. This simulates the multi-level structure of hydroxyapatite nanowires in natural tooth enamel, endowing them with some of the excellent properties imparted by metal ions, such as good thermal stability and wear resistance. The nanowires can be further processed to obtain artificial tooth enamel, tooth enamel restorative materials, etc., which can be used for basic research and clinical applications in biomaterials and tissue engineering.

[0019] 2. This application discloses a method for preparing hydroxyapatite nanowires coated with a metal ion-rich amorphous layer. This method allows for the rapid synthesis of hydroxyapatite nanowires coated with a metal ion-rich amorphous layer at room temperature. The hydroxyapatite nanowires possess a high aspect ratio, and the outer amorphous layer is formed by the interaction of metal ions with the hydroxyl and Ca atoms of the hydroxyapatite nanowires. 2+ Ion substitution occurs around the nanowires. Due to the strong chemical bonds between the amorphous phase and the nanowires, the material is strengthened and toughened, which can improve the mechanical properties of the hydroxyapatite nanowires. At the same time, due to a small amount of ion exchange between metal ions and calcium ions in the hydroxyapatite nanowires, an amorphous layer is generated around the nanowires. This metal ion-rich amorphous layer increases the stability of the hydroxyapatite nanowires under high temperature conditions, giving them some of the excellent properties imparted by metal ions to the hydroxyapatite nanowires, such as improved thermal stability and wear resistance.

[0020] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of this application, the accompanying drawings used in this application will be briefly described below. Obviously, the drawings described below are merely some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without any creative effort.

[0022] Figure 1 This is a TEM image of Al-HAP nanowires from Example 1.

[0023] Figure 2 The images show the XRD patterns of Al-HAP nanowires and pure hydroxyapatite nanowires from Example 1.

[0024] Figure 3 XPS images of Al-HAP nanowires and pure hydroxyapatite nanowires from Example 1.

[0025] Figure 4 This is a SEM image of the Al-HAP nanowires from Example 1, magnified 10,000 times.

[0026] Figure 5 This is a TEM image of the Mn-HAP nanowires in Example 2.

[0027] Figure 6 The images show the XRD patterns of Mn-HAP, HAP, and Mn-HAP-900℃ nanowires from Example 2.

[0028] Figure 7 XPS test images of Mn-HAP and HAP nanowires in Example 2.

[0029] Figure 8 This is a SEM image of Mn-HAP at 10,000x magnification in Example 2.

[0030] Figure 9 This is a TEM image of the Fe-HAP nanowires in Example 3.

[0031] Figure 10 The images show the XRD patterns of Fe-HAP, HAP, and Fe-HAP-900℃ nanowires from Example 3.

[0032] Figure 11 XPS test images of Fe-HAP and HAP nanowires in Example 3.

[0033] Figure 12 This is a SEM image of Fe-HAP in Example 3 at 10,000x magnification.

[0034] Figure 13 The thermogravimetric analysis diagram of Al-HAP in Example 1 is shown.

[0035] Figure 14 This is a TEM image of the Mn-HAP nanowires in Comparative Example 1.

[0036] Figure 15 This is a TEM image of the Mn-HAP nanowires in Comparative Example 2.

[0037] Figure 16This is a TEM image of the Mn-HAP nanowires in Comparative Example 3. Detailed Implementation

[0038] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0040] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0041] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0042] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0043] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0044] The fabrication of artificial enamel or enamel restorative materials by mimicking the structure of tooth enamel has great potential applications in the biomedical field. Currently, the preparation and morphology control of inorganic amorphous nanomaterials remain challenging, and introducing an amorphous interstitial layer that plays a crucial role in mechanical properties to mimic the multi-level structure of tooth enamel remains a significant challenge.

[0045] To address the remaining technical challenges in the preparation and morphology control of inorganic amorphous nanomaterials, this application provides a hydroxyapatite nanowire coated with a metal ion-rich amorphous layer and its preparation method. Specifically, by studying the unique structure of natural tooth enamel, a previously unreported metal ion-rich amorphous layer is introduced into the outer layer of the hydroxyapatite nanowire, constructing a novel amorphous-coated hydroxyapatite nanowire. This nanowire can be further processed to obtain artificial tooth enamel, enamel restorative materials, etc., and can be used for basic research and clinical applications in biomaterials and tissue engineering.

[0046] In a first aspect, embodiments of this application provide a hydroxyapatite nanowire coated with a metal ion-rich amorphous layer, comprising hydroxyapatite nanowires and a metal ion-rich amorphous layer coated on their surface, wherein the hydroxyapatite nanowires have a diameter of 10~100nm and a length of 100~500μm, and the metal ion-rich amorphous layer has a thickness of 1~5nm.

[0047] Preferably, the metal ion includes one of iron, aluminum, copper, manganese, and zinc.

[0048] Secondly, embodiments of this application provide a method for preparing hydroxyapatite nanowires coated with a metal ion-rich amorphous layer, comprising the following steps:

[0049] S1. Disperse hydroxyapatite nanowires in a buffer solution to obtain a hydroxyapatite nanowire suspension.

[0050] S2. Add soluble metal salts to the hydroxyapatite nanowire suspension, stir and react. After the reaction is complete, wash, centrifuge, and freeze-dry to obtain hydroxyapatite nanowires coated with a metal ion-rich amorphous layer.

[0051] Preferably, the buffer solution is an ammonium formate-formic acid buffer solution or a glycine-sodium hydroxide buffer solution, and the pH of the buffer solution is 5.0~9.0.

[0052] In the technical solution of this application embodiment, ammonium formate-formic acid or glycine-sodium hydroxide is used as a buffer solution for adjusting pH, which can avoid excessive pH changes during the reaction process and make it easier to stabilize the pH within the required range.

[0053] Preferably, the concentration of hydroxyapatite nanowires in the hydroxyapatite nanowire suspension is 2~5 g / L.

[0054] Preferably, the dispersion step in step S1 includes placing hydroxyapatite nanowires in a buffer solution, stirring at room temperature for 12-24 hours, and then ultrasonically dispersing them for 30-60 minutes using a power of 600-800W.

[0055] Preferably, the concentration of metal ions in step S2 is 0.0001~0.025 mol / L.

[0056] Preferably, metal ions react with Ca in hydroxyapatite. 2+ The molar ratio is 1:(2~10).

[0057] Preferably, the stirring conditions in step S2 are: stirring at room temperature for 3~24 hours.

[0058] Thirdly, embodiments of this application provide a tooth enamel restoration material prepared from hydroxyapatite nanowires coated with a metal ion-rich amorphous layer.

[0059] In the technical solution of this application embodiment, hydroxyapatite nanowires coated with a metal ion-rich amorphous layer are used through methods such as ice template and self-assembly to prepare multi-scale ordered structural materials based on hydroxyapatite nanowires. Due to the coating of the metal ion-rich amorphous layer, the material has better mechanical properties and can be used in hard tissue repair, such as dental enamel and other biomedical fields, with good application prospects.

[0060] The following are some specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0061] I. Preparation Method

[0062] Example 1

[0063] Preparation method of hydroxyapatite nanowires coated with aluminum-rich amorphous layers:

[0064] (1) 0.125g of HAP (hydroxyapatite) nanowires were placed in an ammonium formate-formic acid buffer solution with a pH of 5.0. The solution was stirred overnight at room temperature and then ultrasonically dispersed at 600W for 30min to obtain a milky white suspension of 2.5g / L. The hydroxyapatite nanowires used were mainly dispersed in diameter of 10-50nm and length of about 100µm.

[0065] The preparation method of hydroxyapatite nanowires is as follows: Hydroxyapatite nanowires are prepared by a solvothermal method. First, solutions of sodium hydroxide, calcium chloride, and sodium dihydrogen phosphate, and a mixed solution of oleic acid, water, and anhydrous ethanol are prepared separately. Then, sodium hydroxide solution is added to the oleic acid mixed solution by a peristaltic pump and reacted at 700-1100 rpm for half an hour. Calcium chloride solution and sodium dihydrogen phosphate solution are then added separately at half-hour intervals. Finally, the mixture is poured into a polytetrafluoroethylene container, which is placed in a reaction vessel and reacted at 180℃ for 24 hours to prepare nanowires.

[0066] (2) Add 0.042g Al2(SO4)3·18H2O to the solution in step (1) and stir at room temperature for 3h; the ratio of aluminum ions to calcium ions in hydroxyapatite in the system is 1:10.

[0067] (3) After the reaction is complete, the product is centrifuged three times with ultrapure water to obtain a white precipitate. The white precipitate is placed in a refrigerator and frozen for more than 6 hours, and then dried in a freeze dryer for 24 hours to obtain Al-HAP nanowires.

[0068] Example 2

[0069] Preparation method of hydroxyapatite nanowires coated with manganese-rich amorphous layer:

[0070] (1) 0.125g HAP nanowires were placed in a glycine-sodium hydroxide buffer solution with a pH of 9, stirred overnight at room temperature, and ultrasonically dispersed at 600W for 30min to obtain a milky white suspension of 2.5g / L; the hydroxyapatite nanowires were mainly dispersed in diameter of 10-50nm and length of about 100µm.

[0071] The preparation method of hydroxyapatite nanowires is as follows: Hydroxyapatite nanowires are prepared by a solvothermal method. First, solutions of sodium hydroxide, calcium chloride, and sodium dihydrogen phosphate, and a mixed solution of oleic acid, water, and anhydrous ethanol are prepared separately. Then, sodium hydroxide solution is added to the oleic acid mixed solution by a peristaltic pump and reacted at 700-1100 rpm for half an hour. Calcium chloride solution and sodium dihydrogen phosphate solution are then added separately at half-hour intervals. Finally, the mixture is poured into a polytetrafluoroethylene container, which is placed in a reaction vessel and reacted at 180℃ for 24 hours to prepare nanowires.

[0072] (2) Add 0.025g MnCl2· 4H2O to the solution in step (1) and stir at room temperature for 12h; the ratio of manganese ions to calcium ions in hydroxyapatite in the system is 1:10.

[0073] (3) After the reaction is complete, the product is centrifuged three times with ultrapure water to obtain a light brown precipitate. The light brown precipitate is placed in a refrigerator and frozen for more than 6 hours, and then dried in a freeze dryer for 24 hours to obtain Mn-HAP nanowires.

[0074] Example 3

[0075] Preparation method of hydroxyapatite nanowires coated with iron-rich amorphous layer:

[0076] (1) 0.125g HAP nanowires were placed in a glycine-sodium hydroxide buffer solution with a pH of 5, stirred overnight at room temperature, and ultrasonically dispersed at 600W for 30min to obtain a milky white suspension of 2.5g / L; the hydroxyapatite nanowires were mainly dispersed in diameter of 10-50nm and length of about 100µm.

[0077] The preparation method of hydroxyapatite nanowires is as follows: Hydroxyapatite nanowires are prepared by a solvothermal method. First, solutions of sodium hydroxide, calcium chloride, and sodium dihydrogen phosphate, and a mixed solution of oleic acid, water, and anhydrous ethanol are prepared separately. Then, sodium hydroxide solution is added to the oleic acid mixed solution by a peristaltic pump and reacted at 700-1100 rpm for half an hour. Calcium chloride solution and sodium dihydrogen phosphate solution are then added separately at half-hour intervals. Finally, the mixture is poured into a polytetrafluoroethylene container, which is placed in a reaction vessel and reacted at 180℃ for 24 hours to prepare nanowires.

[0078] (2) Add 0.0135g FeCl3·6H2O to the solution in step (1) and stir for 3h at room temperature. The concentration of iron ions in the solution is 0.0001M.

[0079] (3) After the reaction is complete, the product is centrifuged three times with ultrapure water to obtain a light yellow precipitate. The light yellow precipitate is placed in a refrigerator and frozen for more than 6 hours. It is then dried in a freeze dryer for 24 hours to obtain Fe-HAP nanowires.

[0080] Example 4

[0081] Preparation method of hydroxyapatite nanowires coated with copper-rich amorphous layers:

[0082] (1) 0.125g HAP nanowires were placed in a glycine-sodium hydroxide buffer solution with a pH of 9, stirred overnight at room temperature, and ultrasonically dispersed at 600W for 30min to obtain a milky white suspension of 2.5g / L; the hydroxyapatite nanowires were mainly dispersed in diameter of 10-50nm and length of about 100µm.

[0083] The preparation method of hydroxyapatite nanowires is as follows: Hydroxyapatite nanowires are prepared by a solvothermal method. First, solutions of sodium hydroxide, calcium chloride, and sodium dihydrogen phosphate, and a mixed solution of oleic acid, water, and anhydrous ethanol are prepared separately. Then, sodium hydroxide solution is added to the oleic acid mixed solution by a peristaltic pump and reacted at 700-1100 rpm for half an hour. Calcium chloride solution and sodium dihydrogen phosphate solution are then added separately at half-hour intervals. Finally, the mixture is poured into a polytetrafluoroethylene container, which is placed in a reaction vessel and reacted at 180℃ for 24 hours to prepare nanowires.

[0084] (2) Add 0.021g CuCl2·2H2O to the solution in step (1) and stir at room temperature for 24h; the ratio of copper ions to calcium ions in hydroxyapatite in the system is 1:10.

[0085] (3) After the reaction is complete, the product is centrifuged three times with ultrapure water to obtain a light blue precipitate. The light blue precipitate is placed in a refrigerator and frozen for more than 6 hours, and then dried in a freeze dryer for 24 hours to obtain Cu-HAP nanowires.

[0086] Example 5

[0087] Preparation method of hydroxyapatite nanowires coated with zinc-rich amorphous layer:

[0088] (1) 0.125g HAP nanowires were placed in a glycine-sodium hydroxide buffer solution with a pH of 7, stirred overnight at room temperature, and ultrasonically dispersed at 600W for 30min to obtain a milky white suspension solution of 2.5g / L; the hydroxyapatite nanowires were mainly dispersed in diameter of 10-50nm and length of about 100µm.

[0089] The preparation method of hydroxyapatite nanowires is as follows: Hydroxyapatite nanowires are prepared by a solvothermal method. First, solutions of sodium hydroxide, calcium chloride, and sodium dihydrogen phosphate, and a mixed solution of oleic acid, water, and anhydrous ethanol are prepared separately. Then, sodium hydroxide solution is added to the oleic acid mixed solution by a peristaltic pump and reacted at 700-1100 rpm for half an hour. Calcium chloride solution and sodium dihydrogen phosphate solution are then added separately at half-hour intervals. Finally, the mixture is poured into a polytetrafluoroethylene container, which is placed in a reaction vessel and reacted at 180℃ for 24 hours to prepare nanowires.

[0090] (2) Add 0.1788g ZnSO4·7H2O to the solution in step (1) and stir at room temperature for 3h; the ratio of zinc ions to calcium ions in hydroxyapatite in the system is 1:2.

[0091] (3) After the reaction is complete, the product is centrifuged three times with ultrapure water to obtain a white precipitate. The white precipitate is placed in a refrigerator and frozen for more than 6 hours, and then dried in a freeze dryer for 24 hours to obtain Zn-HAP nanowires.

[0092] Comparative Example 1

[0093] The difference between Comparative Example 1 and Example 2 is that NaOH was used to adjust the pH to 9, while other conditions were the same as in Example 2.

[0094] Comparative Example 2

[0095] The difference between Comparative Example 2 and Example 2 is that the pH is 7, while all other conditions are the same as in Example 2.

[0096] Comparative Example 3

[0097] The difference between Comparative Example 3 and Example 2 is that the manganese ion content in the system is increased so that the ratio of manganese ions to calcium ions in hydroxyapatite is 1:1. All other conditions are the same as in Example 2.

[0098] II. Testing Methods

[0099] 1. Morphological test:

[0100] (1) Ultra-high resolution field emission scanning electron microscope (SEM), working principle: using an electron beam to irradiate the sample surface, and obtaining a magnified image of the micro-morphology through the secondary electrons and backscattered electrons generated by the interaction between electrons and the sample; model: Hitachi Regulus 8230; test conditions: the sample to be tested is attached to the sample stage with conductive adhesive and metal platinum particles are sputtered for 40-80 s according to the conductivity of the sample, with an accelerating voltage of 5 kV.

[0101] (2) Cryo-transmission electron microscope (TEM) working principle: An accelerated and focused electron beam is projected onto a very thin sample. The electrons collide with atoms in the sample and change direction, thus producing solid angle scattering. The size of the scattering angle is related to the density and thickness of the sample, so images of different brightness can be formed; Model: JEM-F200; Test conditions: Dilute the powder sample to be tested with alcohol, disperse it ultrasonically, and drop it onto an ultrathin carbon film copper grid. After the alcohol on the copper grid has evaporated, it can be used for testing.

[0102] 2. Crystal Structure Testing: X-ray Diffraction (XRD) Working Principle: When a beam of X-rays is incident on a crystal, the X-rays scattered by different atoms interfere with each other, producing strong X-ray diffraction in certain specific directions; Model: Bruker D8 Advance (Germany); Testing Conditions: X-ray target material is Cu-palladium, Kα line wavelength is λ=0.15406nm; Testing angle is 10-80°; Testing voltage V=40 kV, current I=40 mA.

[0103] 3. Material chemical properties and composition testing: Working principle: Using X-rays, such as Al Ka ​​= 1486.6eV, the X-rays interact with the sample surface and utilize the photoelectric effect to excite the sample surface to emit photoelectrons. The photoelectron kinetic energy (KE) is measured using an energy analyzer. According to BE = hv - KE - WF, the binding energy (BE) of the excited electrons is obtained. Model: ESCALAB 250Xi.

[0104] 4. Thermal stability test: Simultaneous Thermal Analyzer (TG / DSC). Working principle: TG: Thermogravimetric analysis is based on the principle of studying the relationship between the mass of the test substance and temperature (or time) under programmed temperature control. By analyzing the thermogravimetric curve, it can be determined at what temperature the test substance changes, and the mass lost can be calculated based on the weight loss. The rate of change of the mass of the test substance can be analyzed through the first derivative curve of mass and temperature.

[0105] III. Analysis of Test Results for Each Embodiment and Comparative Example

[0106] (1) Figure 1 The image shows a TEM image of the hydroxyapatite (Al-HAP) nanowires coated with an aluminum-rich amorphous layer in Example 1. As can be seen from the image, the hydroxyapatite nanowires prepared by the method in Example 1 are coated with an amorphous coating. Figure 5 and Figure 9 The images show TEM images of Mn-HAP nanowires and Fe-HAP nanowires, respectively. As can be seen from the images, the hydroxyapatite nanowires prepared by the methods in Examples 2 and 3 are coated with an amorphous coating.

[0107] In Comparative Example 1, pH was directly adjusted using an alkaline solution, resulting in the prepared Mn-HAP nanowires as shown in the figure. Figure 14 As shown, no amorphous layer was found, indicating that a buffer solution was used to ensure that the pH remained stable during the reaction process in order to generate an amorphous layer.

[0108] In Comparative Example 2, the pH was adjusted to 7 using a buffer solution, and the resulting Mn-HAP nanowires were as follows: Figure 15As shown, no amorphous layer was found, indicating that pH 9 is more suitable for preparing Mn-HAP nanowires.

[0109] In Comparative Example 3, the manganese ion content in the system was increased to match the calcium ion content in the solution. Transmission electron microscopy revealed small particles attached to the nanowires, such as... Figure 16 The reason is that the high concentration of manganese ions prevents the formation of an amorphous layer, resulting in the formation of small crystalline particles.

[0110] (2) Figure 2 The images show the XRD patterns of Al-HAP nanowires and pure hydroxyapatite (HAP) nanowires in Example 1. By comparing the XRD patterns of pure hydroxyapatite nanowires and nanowires calcined at 900℃, the position and intensity of the crystallization peaks of Al-HAP are similar to those of pure hydroxyapatite nanowires. However, the aluminum-rich nanowires calcined at 900℃ show new crystallization peaks, which are Ca9Al(PO4)7 crystalline phases, and the intensity of the crystallization peaks is significantly improved. This is because the outer amorphous layer of the nanowires is transformed into a crystalline phase at 900℃. Figure 6 , Figure 10 The images show TEM images of Mn-HAP, HAP, Mn-HAP-900℃ and Fe-HAP, HAP, Fe-HAP-900℃ nanowires, respectively. As can be seen from the images, the hydroxyapatite nanowires prepared by the methods in Examples 2 and 3 are coated with the corresponding amorphous coatings.

[0111] (3) Figure 3 The XPS images of Al-HAP nanowires and HAP nanowires from Example 1 show that pure HAP nanowires contain Ca, P, and O elements. Compared to pure HAP, the XPS images of Al-HAP nanowires show the presence of Al, indicating that Al is present in the ion exchange process of HAP nanowires. 3+ It has been successfully incorporated into nanowires. Figure 7 XPS spectra of Mn-HAP and HAP nanowires. Figure 11 XPS spectra of Fe-HAP and HAP nanowires indicate that Mn 2+ Fe 3+ They were introduced into the nanowires respectively.

[0112] (4) Figure 4 , Figure 8 and Figure 12 The images show SEM images of Al-HAP, Mn-HAP, and Fe-HAP nanowires magnified 10,000 times. It can be seen that Al-HAP, Mn-HAP, and Fe-HAP nanowires still maintain the morphology of nanowires and have a high aspect ratio. Coating the outer periphery of the nanowires with an amorphous layer did not destroy the original structure of the nanowires.

[0113] (5) Figure 13 The thermogravimetric analysis (TGA) diagram of Al-HAP in Example 1 shows that the decomposition temperature of Al-HAP is 824℃, while that of pure HAP is 701℃, indicating that the thermal stability is greatly improved.

[0114] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A hydroxyapatite nanowire coated with a metal ion-rich amorphous layer, characterized in that, It includes hydroxyapatite nanowires and a metal ion-rich amorphous layer coated on their surface, wherein the metal ions are selected from one of iron, aluminum, copper, manganese, and zinc; The preparation method of the hydroxyapatite nanowires coated with a metal ion-rich amorphous layer includes the following steps: S1. Hydroxyapatite nanowires are dispersed in a buffer solution to obtain a hydroxyapatite nanowire suspension, wherein the buffer solution is an ammonium formate-formic acid buffer solution or a glycine-sodium hydroxide buffer solution; wherein, when the metal ion is iron and aluminum, the pH of the buffer solution is 5.0, when the metal ion is copper and manganese, the pH of the buffer solution is 9.0, and when the metal ion is zinc, the pH of the buffer solution is 7.

0. S2. Add soluble metal salt to the hydroxyapatite nanowire suspension solution, stir and react. After the reaction is completed, wash, centrifuge and freeze dry to obtain hydroxyapatite nanowires coated with a metal ion-rich amorphous layer. The hydroxyapatite nanowires have a diameter of 10-100 nm and a length of 100-500 μm; the metal ion-rich amorphous layer has a thickness of 1-5 nm. The concentration of hydroxyapatite nanowires in the hydroxyapatite nanowire suspension solution is 2~5 g / L; The concentration of the metal ions in step S2 is 0.0001~0.025 mol / L, and the metal ions react with Ca in hydroxyapatite. 2+ The molar ratio is 1:(2~10).

2. The hydroxyapatite nanowires coated with a metal ion-rich amorphous layer according to claim 1, characterized in that, The dispersion step in step S1 includes placing hydroxyapatite nanowires in a buffer solution, stirring at room temperature for 12-24 hours, and then ultrasonically dispersing them for 30-60 minutes using a power of 600-800W.

3. The hydroxyapatite nanowires coated with a metal ion-rich amorphous layer according to claim 1, characterized in that, The stirring conditions described in step S2 are: stirring at room temperature for 3 to 24 hours, with a stirring speed of 400 to 800 rpm.

4. A dental enamel restoration material, characterized in that, It is prepared from hydroxyapatite nanowires coated with a metal ion-rich amorphous layer according to any one of claims 1 to 3.

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