Method for preparing small-size silver iodide

Abstract

The invention belongs to the field of preparation and application of nano materials, and discloses a simple method for preparing small-size silver halide (AgX: X = Cl, Br and I) nano particles. The preparation method comprises the following steps: respectively dropwise adding an ethylene glycol solution of silver nitrate and an ethylene glycol solution of sodium iodide into a stirred oleylamine phase; the small-size silver iodide nanoparticles are prepared by a method for controlling precipitation of silver ions and iodide ions in an oleylamine phase. The method has the main advantages that (1) the process is simple, the operation is convenient, and only three steps of solution preparation, stirring control and centrifugal separation are needed; and (2) the preparation process has good repeatability and controllability, and the average size of the synthesized nanoparticles can be controlled within 10nm. And (3) the prepared silver iodide nanoparticles have the characteristics of large specific surface area, high active sites and the like, and are suitable for preparing photocatalysts, artificial rainfall agents, CT contrast agents and the like.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterial preparation and application, and specifically relates to a method for preparing small-sized silver iodide. Background Technology

[0002] In recent years, silver halides (AgX: X = Cl, Br, I) have emerged as a high-performance semiconductor material. Their unique surface plasmon resonance (SPR) provides excellent visible light excitation properties. Furthermore, the unique properties of silver and halogens suggest significant application potential in antibacterial agents, CT contrast agents, biocatalysts, and sensors. Current synthesis methods for silver halides mainly include solvothermal methods, co-precipitation methods, and polyol methods. However, the prepared silver halides often exhibit poor morphology and inhomogeneous sizes, and are accompanied by complex operations and high costs. The active sites and specific surface area of ​​nanoparticles are related to their size. Generally, smaller nanoparticles have larger specific surface areas and more active sites. Therefore, exploring a method for synthesizing silver halide nanoparticles with controllable morphology, simple operation, and fine size is of great significance.

[0003] Typically, small, uniformly shaped inorganic nanoparticles are prepared via thermal decomposition. The principle involves heating a metal-organic precursor in a high-boiling-point organic solvent, causing it to decompose or oxidize to obtain the corresponding element, oxide, or compound. However, due to the high cost of the raw materials and the cumbersome vacuuming and protective gas processes required, thermal decomposition is complex, time-consuming, and costly, making it unsuitable for large-scale industrial production. More importantly, silver halides are easily reduced to elemental silver under organic solvents and high-temperature conditions. Therefore, methods for synthesizing small, uniformly shaped, low-cost, and simple silver halides are rarely reported.

[0004] This invention proposes a simple method for preparing small-sized silver halide (AgX: X = Cl, Br, I) nanoparticles. The principle involves controlling the precipitation reaction of silver nitrate and sodium halide in liquid oleylamine. A specific concentration and ratio of silver nitrate ethylene glycol solution and sodium halide ethylene glycol solution are added dropwise to an oleylamine solution, ensuring a certain stirring time, followed by centrifugation to obtain the nanoparticles. This reaction can be carried out at relatively low heating temperatures and ambient pressures, and the resulting silver halide nanoparticles can be controlled to a size within 10 nm with uniform morphology, providing a simple and rapid method for preparing silver halide nanoparticles. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing small-sized silver halides, thereby improving the problems of complex processes, large size, and uncontrollable morphology in traditional silver halide synthesis.

[0006] To achieve the above technical objectives, the present invention adopts the following technical solution: A method for preparing silver iodide nanoparticles, controlling the space in which ion precipitation occurs, specifically includes the following steps: Step 1: Prepare bismuth nitrate crystals and sodium iodide in ethylene glycol solution.

[0007] Bismuth nitrate crystals were dissolved in an ethylene glycol solution, maintaining the same molar concentration of the bismuth nitrate crystals in the ethylene glycol solution. Similarly, an ethylene glycol solution of sodium iodide with the same molar concentration was prepared.

[0008] Step 2: Control the precipitation of bismuth nitrate in silver nitrate and sodium iodide solution.

[0009] Take oleylamine in a round-bottom flask and stir it in a water bath to ensure that the oleylamine is in a liquid state. While stirring, add dropwise an ethylene glycol solution of bismuth nitrate crystals from step 1. After stirring, add dropwise an ethylene glycol solution of sodium iodide and continue stirring.

[0010] Step 3: Separation of prepared nanoparticles.

[0011] After stirring, place the mixed solution from step 2 into a centrifuge tube and centrifuge at a suitable speed. Then, wash it repeatedly by centrifugation with a mixed solution of n-hexane / ethanol / water, wherein the volume ratio of n-hexane, ethanol, and water is 2:5:3. Finally, disperse it in cyclohexane to obtain small-sized silver iodide nanoparticles.

[0012] Preferably, the molar concentration of the silver nitrate ethylene glycol solution in step 1 is 0.4 mol / L.

[0013] Preferably, the stirring speed of oleylamine in step 2 is 500-1000 rpm.

[0014] Preferably, in step 2, the volume ratio of silver nitrate ethylene glycol solution to oleylamine is 0.5:10.

[0015] Preferably, in step 2, the silver nitrate ethylene glycol solution is added to oleylamine at a rapid dripping rate.

[0016] Preferably, in step 2, an equal volume and concentration of sodium iodide ethylene glycol solution is added.

[0017] Preferably, in step 2, after adding the sodium iodide ethylene glycol solution, stirring is continued for 1 hour.

[0018] Preferably, the centrifugation speed of the mixed solution in step 3 is 5000 rpm.

[0019] Preferably, in step 3, after centrifugation, a mixed solution of n-hexane / ethanol / water is used as the dispersion solvent, and the mixture is repeatedly centrifuged and washed three times.

[0020] Compared with existing technologies, the method for preparing small-sized silver iodide nanoparticles according to the present invention has the following advantages: (1) This invention first describes a method for preparing silver iodide nanoparticles by controlling the precipitation reaction of silver nitrate and sodium iodide in an oleylamine solution. The prepared silver iodide has advantages such as uniform morphology, good monodispersity, small size, high specific surface area, and high active sites.

[0021] (2) The method of the present invention can be carried out at room temperature and pressure, is simple to operate, has low cost, good repeatability, and large output, which is conducive to industrial mass production.

[0022] (3) The small-sized silver iodide nanoparticles prepared by this invention are easy to surface modify and have good application prospects in photocatalysis, electrocatalysis, sensors, contrast agents and other fields. Attached Figure Description

[0023] Figure 1 This is a flowchart of a simplified preparation method for small-sized silver iodide according to the present invention.

[0024] Figure 2 The image shows a 10 nm transmission electron microscope image of silver iodide prepared in Example 1.

[0025] Figure 3 The image shows a 2nm transmission electron microscope image of silver iodide prepared in Example 2.

[0026] Figure 4 The image is a transmission electron microscope (TEM) image of 20 nm silver iodide prepared in Example 3.

[0027] Figure 5 The image shows a 4nm transmission electron microscope image of silver chloride prepared in Example 4.

[0028] Figure 6 The image shows a 3nm transmission electron microscope (TEM) image of silver bromide prepared in Example 5. Detailed Implementation

[0029] To make the objectives and technical solutions of this invention clearer, the invention will be further described below with reference to specific embodiments, but the invention is not limited to the following embodiments.

[0030] Example 1 like Figure 1 As shown, a method for preparing small-sized silver iodide by controlling the precipitation process of silver nitrate and sodium iodide includes the following steps: (1) Preparation of ethylene glycol solution of silver nitrate and sodium iodide: Dissolve silver nitrate in ethylene glycol solution and stir for 1 hour to keep the molar concentration of silver nitrate ethylene glycol solution at 0.4 mol / L. Similarly, prepare ethylene glycol solution of sodium iodide of the same concentration.

[0031] (2) Controlling the precipitation of silver nitrate and sodium iodide in ethylene glycol solution: Take 30 mL of oleylamine in a 50 mL round-bottom flask and stir in a 30 °C water bath to ensure that the oleylamine is in a liquid state. Under the condition of stirring speed of 500 rpm, rapidly add 1 mL of ethylene glycol solution of silver nitrate with a molar concentration of 0.4 mol / L from (1), stir for 10 min, and then add an equal volume of sodium iodide ethylene glycol solution of the same concentration. Keep stirring for 1 hour.

[0032] (3) Separation of nanoparticles: After stirring, the mixed solution from (2) was placed in a 50 mL centrifuge tube and centrifuged at 5000 rpm. Then, the nanoparticles were dispersed in a mixed solution of n-hexane / ethanol / water (volume ratio 2:5:3) and centrifuged repeatedly three times. Finally, the nanoparticles were dispersed in cyclohexane to obtain monodisperse silver iodide nanoparticles. Figure 2 As shown, the obtained silver iodide nanoparticles are in a monodisperse state with an average particle size of 10 nm.

[0033] Example 2 A method for preparing small-sized silver iodide by controlling the precipitation process of silver nitrate and sodium iodide includes the following steps: (1) Preparation of ethylene glycol solution of silver nitrate and sodium iodide: Dissolve silver nitrate in ethylene glycol solution and stir for 1 hour to keep the molar concentration of silver nitrate ethylene glycol solution at 0.4 mol / L. Similarly, prepare ethylene glycol solution of sodium iodide of the same concentration.

[0034] (2) Controlling the precipitation of silver nitrate and sodium iodide in ethylene glycol solution: Take 30 mL of oleylamine in a 50 mL round-bottom flask and stir in a 30 °C water bath to ensure that the oleylamine is in a liquid state. Under the condition of stirring speed of 500 rpm, rapidly add 0.5 mL of ethylene glycol solution of silver nitrate with a molar concentration of 0.4 mol / L in (1), stir for 10 min, and then add an equal volume of sodium iodide ethylene glycol solution of the same concentration. Keep stirring for 1 hour.

[0035] (3) Separation of nanoparticles: After stirring, the mixed solution from (2) was placed in a 50 mL centrifuge tube and centrifuged at 5000 rpm. Then, the nanoparticles were dispersed in a mixed solution of n-hexane / ethanol / water (volume ratio 2:5:3) and centrifuged repeatedly three times. Finally, the nanoparticles were dispersed in cyclohexane to obtain monodisperse silver iodide nanoparticles. Figure 3 As shown, the obtained silver iodide nanoparticles are in a monodisperse state with an average particle size of 2 nm.

[0036] Example 3 A method for preparing small-sized silver iodide by controlling the precipitation process of silver nitrate and sodium iodide includes the following steps: (1) Preparation of ethylene glycol solution of silver nitrate and sodium iodide: Dissolve silver nitrate in ethylene glycol solution and stir for 1 hour to keep the molar concentration of silver nitrate ethylene glycol solution at 0.4 mol / L. Similarly, prepare ethylene glycol solution of sodium iodide of the same concentration.

[0037] (2) Controlling the precipitation of silver nitrate and sodium iodide in ethylene glycol solution: Take 30 mL of oleylamine in a 50 mL round-bottom flask and stir in a 30 °C water bath to ensure that the oleylamine is in a liquid state. Under the condition of stirring speed of 500 rpm, rapidly add 2 mL of ethylene glycol solution of silver nitrate with a molar concentration of 0.4 mol / L from (1), stir for 10 min, and then add an equal volume of sodium iodide ethylene glycol solution of the same concentration. Keep stirring for 1 hour.

[0038] (3) Separation of nanoparticles: After stirring, the mixed solution from (2) was placed in a 50 mL centrifuge tube and centrifuged at 5000 rpm. Then, the nanoparticles were dispersed in a mixed solution of n-hexane / ethanol / water (volume ratio 2:5:3) and centrifuged repeatedly three times. Finally, the nanoparticles were dispersed in cyclohexane to obtain monodisperse silver iodide nanoparticles. Figure 4 As shown, the obtained silver iodide nanoparticles are in an aggregated state with an average particle size of 20 nm.

[0039] Example 4 A method for preparing small-sized silver chloride by controlling the precipitation process of silver nitrate and sodium chloride includes the following steps: (1) Preparation of ethylene glycol solution of silver nitrate and sodium chloride: Dissolve silver nitrate in ethylene glycol solution and stir for 1 hour to maintain the molar concentration of silver nitrate ethylene glycol solution at 0.4 mol / L. Similarly, prepare ethylene glycol solution of sodium chloride of the same concentration.

[0040] (2) Controlling the precipitation of silver nitrate and sodium chloride in ethylene glycol solution: Take 30 mL of oleylamine in a 50 mL round-bottom flask and stir in a 30 °C water bath to ensure that the oleylamine is in a liquid state. Under the condition of stirring speed of 500 rpm, rapidly add 1 mL of ethylene glycol solution of silver nitrate with a molar concentration of 0.4 mol / L from (1), stir for 10 min, and then add an equal volume of sodium chloride ethylene glycol solution of the same concentration. Keep stirring for 1 hour.

[0041] (3) Separation of nanoparticles: After stirring, the mixed solution from (2) was placed in a 50 mL centrifuge tube and centrifuged at 5000 rpm. Then, the nanoparticles were dispersed in a mixed solution of n-hexane / ethanol / water (volume ratio 2:5:3) and centrifuged repeatedly three times. Finally, the nanoparticles were dispersed in cyclohexane to obtain monodisperse silver chloride nanoparticles. Figure 5 As shown, the obtained silver chloride nanoparticles are in a monodisperse state with an average particle size of 4 nm.

[0042] Example 5 A method for preparing small-sized silver bromide by controlling the precipitation process of silver nitrate and sodium bromide includes the following steps: (1) Preparation of ethylene glycol solution of silver nitrate and sodium bromide: Dissolve silver nitrate in ethylene glycol solution and stir for 1 hour to keep the molar concentration of silver nitrate ethylene glycol solution at 0.4 mol / L. Similarly, prepare ethylene glycol solution of sodium bromide of the same concentration.

[0043] (2) Controlling the precipitation of silver nitrate and sodium bromide in ethylene glycol solution: Take 30 mL of oleylamine in a 50 mL round-bottom flask and stir in a 30 °C water bath to ensure that the oleylamine is in a liquid state. Under the condition of stirring speed of 500 rpm, rapidly add 1 mL of ethylene glycol solution of silver nitrate with a molar concentration of 0.4 mol / L from (1), stir for 10 min, and then add an equal volume of sodium bromide ethylene glycol solution of the same concentration. Keep stirring for 1 hour.

[0044] (3) Separation of nanoparticles: After stirring, the mixed solution from (2) was placed in a 50 mL centrifuge tube and centrifuged at 5000 rpm. Then, the nanoparticles were dispersed in a mixed solution of n-hexane / ethanol / water (volume ratio 2:5:3) and centrifuged repeatedly three times. Finally, the nanoparticles were dispersed in cyclohexane to obtain monodisperse silver bromide nanoparticles. Figure 6 As shown, the obtained silver bromide nanoparticles are in a monodisperse state with an average particle size of 3 nm.

Claims

1. A method for preparing silver iodide nanoparticles, characterized in that, Controlling the space in which ion precipitation occurs involves the following steps: Step 1: Preparation of bismuth nitrate crystals and sodium iodide in ethylene glycol solution Bismuth nitrate crystals were dissolved in an ethylene glycol solution, and the molar concentration of the bismuth nitrate crystals in the ethylene glycol solution was maintained. Similarly, an ethylene glycol solution of sodium iodide with the same molar concentration was prepared. Step 2: Controlling the precipitation of bismuth nitrate in silver nitrate and sodium iodide solutions Take oleylamine in a round-bottom flask, and keep the oleylamine in a liquid state by stirring in a water bath. While stirring, add the ethylene glycol solution of bismuth nitrate crystals from step 1 dropwise, stir, and then add the ethylene glycol solution of sodium iodide dropwise. Continue stirring. Step 3: Separation of prepared nanoparticles After stirring, the mixed solution from step 2 is placed in a centrifuge tube and centrifuged at a suitable speed. Then, it is repeatedly centrifuged and washed with a mixed solution of hexane / ethanol / water, wherein the volume ratio of hexane, ethanol, and water is 2:5:

3. Finally, it is dispersed in cyclohexane to obtain small-sized silver iodide nanoparticles.

2. The method for preparing small-sized silver iodide according to claim 1, characterized in that: The molar concentration of the silver nitrate ethylene glycol solution in step 1 is 0.4 mol / L.

3. The method for preparing small-sized silver iodide according to claim 1, characterized in that: In step 2, the stirring speed of oleylamine is 500-1000 rpm.

4. The method for preparing small-sized silver iodide according to claim 1, characterized in that: In step 2, the volume ratio of silver nitrate ethylene glycol solution to oleylamine is 0.5:

10.

5. The method for preparing small-sized silver iodide according to claim 1, characterized in that: In step 2, the silver nitrate ethylene glycol solution is added to oleylamine at a rapid dripping rate.

6. The method for preparing small-sized silver iodide according to claim 1, characterized in that: In step 2, an equal volume and concentration of sodium iodide ethylene glycol solution are added.

7. The method for preparing small-sized silver iodide according to claim 1, characterized in that: In step 2, after adding the sodium iodide ethylene glycol solution, continue stirring for 1 hour.

8. The method for preparing small-sized silver iodide according to claim 1, characterized in that: In step 3, the centrifugation speed of the mixed solution is 5000 rpm.

9. The method for preparing small-sized silver iodide according to claim 1, characterized in that: In step 3, after centrifugation, a mixed solution of n-hexane / ethanol / water is used as the dispersion solvent, and the mixture is centrifuged and washed three times.

10. A method for preparing small-sized silver iodide according to any one of claims 1-9.

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