Nanoselenium, preparation method and application thereof

Abstract

This invention provides a nano-selenium, its preparation method, and its applications, relating to the field of nano-selenium fertilizer technology. Using sodium selenate or sodium selenite as raw material A and thiol-functionalized graphene as raw material B, raw material A and raw material B are mixed and reacted for a certain period to obtain nano-selenium, which can be used in fertilizers, food anti-oxidation and preservation, industrial catalysis, or chemical analysis. This invention uses inorganic selenium and thiol-functionalized graphene as raw materials. Through a simple solution mixing, reaction, and settling process, the in-situ reduction of selenite by thiol-functionalized graphene and the stable loading of nano-selenium are achieved, completing the conversion from inorganic selenium to nano-selenium in one step without the need for reducing agents.

Description

Technical Field

[0001] This invention relates to the fields of fertilizer and nano-selenium materials, specifically to a nano-selenium, its preparation method, and its application. Background Technology

[0002] Currently, the selenium content in agricultural products can only be controlled through exogenous selenium application, primarily through soil application, foliar spraying, and selenium immersion. However, inorganic selenium, such as sodium selenite, is easily adsorbed and fixed by the soil after application, making it difficult for plants to absorb, resulting in low plant utilization and high biotoxicity. Foliar spraying of selenium fertilizer is a relatively rapid way to increase the selenium content of crops. Therefore, current selenium enrichment research mainly employs foliar spraying.

[0003] Exploring highly bioactive and safe selenium sources is a current research focus. A mainstream approach involves using microorganisms to reduce sodium selenite to prepare selenium nanoparticles. For example, sodium selenite is added to a Bacillus subtilis culture solution for cultivation, and the precipitate is separated to obtain nano-selenium. Another approach uses nano-adsorbents containing inorganic selenium solution as carriers, with selenium-reducing bacteria as the loading medium. After encapsulation and static incubation, the selenium-reducing bacteria convert the inorganic selenium within the carrier into nano-bio-selenium, resulting in functional nano-bio-selenium microspheres. Additionally, existing technologies utilize sodium selenite and copper-zinc-aluminum silicate microspheres as raw materials, leveraging the unique porous structure of these microspheres to provide precise physical confinement for the directional growth of nano-selenium.

[0004] However, the existing technologies for preparing nano-selenium are all quite complex. Therefore, this application aims to propose a simpler and easier method for preparing nano-selenium, along with its preparation method and applications. Summary of the Invention

[0005] This invention addresses the aforementioned problems in the prior art by providing a nano-selenium, its preparation method, and its application.

[0006] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: On one hand, the present invention provides a method for preparing nano-selenium, characterized by comprising the following steps: Using sodium selenate or sodium selenite as raw material A and mercaptographene as raw material B, raw material A and raw material B are mixed and reacted for a certain period of time to obtain nano-selenium.

[0007] Furthermore, raw material A and raw material B are mixed in solution form.

[0008] Furthermore, the thiol graphene is thiol-modified graphene or graphene oxide.

[0009] Furthermore, the preparation method of mercaptographene involves mixing and reacting a dispersion of graphene or graphene oxide with a silanizing agent containing mercapto groups to obtain mercaptographene.

[0010] The thiol-containing silanizing agent is a mercaptosilane or a thiol reagent. The mercaptosilane is preferably (3-mercaptopropyl)trimethoxysilane, mercapto-polyethylene glycol-silane, or 3-mercaptopropyltriethoxysilane, and the thiol reagent is preferably mercaptoethylamine, L-cysteine, or dithiothreitol, used in the form of a 0.1% to 50% ethanol solution.

[0011] The graphene or graphene oxide dispersion is a dispersion of graphene or graphene oxide in water, ethanol or methanol.

[0012] On the other hand, the present invention provides a nano-selenium, characterized in that it is prepared by the preparation method described above.

[0013] In another aspect, the present invention provides an application of nano-selenium, characterized in that it is prepared by the preparation method described above, and the nano-selenium is used as an effective ingredient in fertilizers, food anti-oxidation and preservation, industrial catalysis or chemical analysis.

[0014] The beneficial effects of this invention are as follows: Using inorganic selenium and thiol-functionalized graphene as raw materials, this invention achieves in-situ reduction of selenite and stable loading of nano-selenium by thiol-functionalized graphene through a simple solution mixing, reaction, and settling process. This allows for the one-step conversion of inorganic selenium to nano-selenium without the need for reducing agents. This method has the following outstanding advantages: Compared with traditional inorganic selenium salts, it has significant advantages such as low toxicity and safety, high stability, good dispersibility, high bioavailability, and multifunctional synergy; Simple and environmentally friendly process: No complex equipment or harsh conditions are required; aqueous phase reaction; easy to scale up. Controllable structure and adjustable performance: The size and loading of nano-selenium can be controlled by adjusting the type of graphene, the type and concentration of thiol reagent, and the reaction temperature and time. Wide range of applications: The product combines the carrier advantages of graphene with the bioactivity of nano-selenium, making it suitable for multiple fields such as agriculture, food, and industry. Its application value and market prospects are far superior to traditional selenium salts.

[0015] Good stability: The composite material is stable in water dispersion, making it easy to store, transport and use. Attached Figure Description

[0016] Figure 1 Here is a SEM image of the nano-selenium prepared in Example 2; Figure 2This is a SEM image of the nano-selenium prepared in Comparative Example 2. Detailed Implementation

[0017] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto. The following embodiments are only used to explain the present invention and are not intended to limit the scope of the present invention. Those skilled in the art can make appropriate modifications and substitutions to the following embodiments without departing from the spirit of the present invention, and such modifications and substitutions all fall within the protection scope of the present invention.

[0018] Example 1: Preparation of selenium nanoparticles supported on graphene modified with mercaptosilane Step 1: Preparation of Thiol-based Graphene 1) Prepare 100 ml of 0.001% graphene aqueous solution; 2) Prepare 100 ml of 0.1% (3-mercaptopropyl)trimethoxysilane ethanol-water (ethanol-water ratio 2:8); 3) Under magnetic stirring, slowly add the solution from step 2 dropwise into the graphene aqueous solution; 4) Heat to 85 degrees and react for 1 hour to obtain a mercaptographene dispersion.

[0019] Step 2: Generation and Loading of Nano-Selenium 5) Take 100 ml of a 0.011% sodium selenate aqueous solution; 6) Under high-speed stirring conditions, slowly add the sodium selenate aqueous solution to the mercaptographene dispersion prepared in step 4; 7) Let the mixture stand overnight.

[0020] Example 2: Preparation of selenium nanoparticles supported on graphene oxide modified with thiol-polyethylene glycol-silane Step 1: Preparation of thiolized graphene oxide 1) Prepare 100 mL of a 1% graphene oxide ethanol solution; 2) Prepare 100 mL of a 3% mercapto-polyethylene glycol-silane ethanol-water mixed solution (alcohol-water volume ratio 2:8). 3) Under magnetic stirring, slowly add the solution from step 2 dropwise to the graphene oxide ethanol solution; 4) Heat to 5℃ and react for 24 hours to obtain a mercapto-modified graphene oxide dispersion.

[0021] Step 2: Generation and Loading of Nano-Selenium 5) Prepare 100 mL of a 10% sodium selenite aqueous solution; 6) While stirring at high speed, slowly add the sodium selenite aqueous solution to the dispersion in step 4; 7) Let the mixture stand overnight.

[0022] Example 3: Preparation of 3-mercaptopropyltriethoxysilane-modified graphene oxide supported on selenium nanoparticles Step 1: Preparation of thiolized graphene oxide 1) Prepare 100 mL of a 30% graphene oxide methanol solution; 2) Prepare 100 mL of a 0.1% 3-mercaptopropyltriethoxysilane ethanol solution; 3) Under magnetic stirring, the 3-mercaptopropyltriethoxysilane ethanol solution was slowly added dropwise to the graphene oxide methanol solution; 4) Heat to 70℃ and react for 14 hours to obtain a dispersion of 3-mercaptopropyltriethoxysilane-functionalized graphene oxide.

[0023] Step 2: Generation and Loading of Nano-Selenium 5) Prepare 100 mL of a 20% sodium selenate aqueous solution; 6) While stirring at high speed, slowly add the sodium selenate aqueous solution to the above dispersion; 7) Let the mixture stand overnight.

[0024] Example 4: Preparation of selenium nanoparticles supported on graphene oxide modified with mercaptoethylamine Step 1: Preparation of thiolized graphene oxide 1) Prepare 100 mL of a 5% graphene oxide aqueous solution; 2) Prepare 100 mL of a 50% mercaptoethylamine ethanol solution; 3) Under magnetic stirring, slowly add the mercaptoethylamine ethanol solution dropwise to the graphene oxide aqueous solution; 4) Heat to 65℃ and react for 10 hours to obtain a thiol-functionalized graphene oxide dispersion.

[0025] Step 2: Generation and Loading of Nano-Selenium 5) Prepare 100 mL of a 10% sodium selenate aqueous solution; 6) While stirring at high speed, slowly add the sodium selenate aqueous solution to the above dispersion; 7) Let the mixture stand overnight.

[0026] Example 5: Preparation of L-cysteine-modified graphene oxide supported selenium nanoparticles Step 1: Preparation of thiolized graphene oxide 1) Prepare 100 mL of a 5% graphene oxide aqueous solution; 2) Prepare 100 mL of a 10% L-cysteine ​​ethanol solution; 3) Under magnetic stirring, the L-cysteine ​​solution was slowly added dropwise to the graphene oxide aqueous solution; 4) Heat to 50℃ and react for 15 hours to obtain a thiol-functionalized graphene oxide dispersion.

[0027] Step 2: Generation and Loading of Nano-Selenium 5) Prepare 100 mL of a 10% sodium selenate aqueous solution; 6) While stirring at high speed, slowly add the sodium selenate aqueous solution to the above dispersion; 7) Let the mixture stand overnight.

[0028] Results and Characterization The phenomena observed after the final reaction in Examples 1-5 were consistent: the system presented as a red sol, which, after filtration and drying, yielded a free-flowing red solid powder. This powder could be redispersed in water to form a stable nano-dispersion system and exhibited a clear Tyndall effect, indicating the successful preparation of graphene-supported selenium nanocomposite materials.

[0029] Comparative Example 1: Reaction of unfunctionalized graphene with sodium selenite The preparation method of the comparative example of nano-selenium material is basically the same as that of Example 1, except that steps 2, 3, and 4 are not performed, that is, the unfunctionalized graphene oxide from step 1 is combined with sodium selenate.

[0030] Results: Unfunctionalized graphene oxide could not be effectively reduced and loaded with nano-selenium, resulting in severe product agglomeration, poor dispersibility, and low stability.

[0031] Comparative Example 2: Reverse feeding sequence (first mix graphene and sodium selenite, then add thiol reagent) The preparation method of the comparative example of selenium nanomaterials is basically the same as that of Example 1, except that a functionalization followed by reduction process is adopted. The steps are as follows: 1) Prepare 100 mL of 1% graphene oxide aqueous solution, 100 mL of 10% sodium selenite aqueous solution, and 100 mL of 0.1% (3-mercaptopropyl)trimethoxysilane ethanol-water (ethanol-water ratio 2:8) solution; 2) Mix the sodium selenite aqueous solution with the graphene oxide aqueous solution, and let the mixture stand overnight; 3) Add 100 mL of 0.1% (3-mercaptopropyl)trimethoxysilane ethanol-water solution (ethanol-water ratio 2:8) to the above mixture.

[0032] 4) Heat to 85 degrees Celsius and let stand for 1 hour after reaction.

[0033] Results: The obtained nano-selenium composite material exhibited severe selenium particle agglomeration, weak bonding with the graphene oxide substrate, and easy detachment. The material's dispersibility, structural stability, and interfacial bonding strength were significantly worse than in Example 1. This was mainly because this comparative example used a reverse feeding sequence: first mixing graphene oxide with sodium selenite, then adding a mercapto reagent. Sodium selenite only undergoes physical adsorption on the unfunctionalized graphene oxide surface, resulting in disordered adsorption sites and weak interactions, failing to form a stable pre-assembled structure. The subsequently added (3-mercaptopropyl)trimethoxysilane, acting as both a reducing agent and a modifying agent, struggled to homogeneously, controllably, and in-situ reduce the physically adsorbed selenium source, easily leading to excessively rapid local reduction rates. The generated elemental selenium lacked anchoring and dispersion of functional groups on the graphene oxide surface, making it highly susceptible to agglomeration and growth. Furthermore, its bond with graphene oxide was only weak, lacking stable chemical bonding, ultimately resulting in deterioration of the material's structure and performance.

[0034] Comparative Example 3 The preparation method of this comparative example is basically the same as that of Example 1, except that (3-mercaptopropyl)trimethoxysilane is replaced with an equimolar amount of benzyl mercaptan. The other processes, concentrations, temperatures, and times are the same.

[0035] Results: Benzyl mercaptan (Ph-CH2-SH) contains only the -SH group and lacks the functional group to covalently react with GO. Therefore, it exists only on the graphene oxide surface through physical adsorption and cannot form covalent bonds with graphene. It is easily detached and lost during the reaction. The generated nano-selenium cannot be stably loaded onto the graphene sheets; the system quickly precipitates and separates. Its dispersibility, stability, and loading rate are far inferior to those of Example 1, and it lacks practical application value.

[0036] The samples obtained from the above embodiments and comparative examples were subjected to a series of tests, and the results are shown in Table 1.

[0037] Table 1

[0038] 1. Detection of biocompatibility and antioxidant properties of nano-selenium composite materials 1) In vitro biocompatibility testing (cell viability) Test method: The MTT assay was used, referring to GB / T 16886.5-2017 Biological evaluation of medical devices Part 5: In vitro cytotoxicity test. Wheat root cap cells were used as the test object. The composite material was prepared into a culture medium with a selenium concentration of 100 μg / mL. After culturing for 24 hours, the cell viability was detected.

[0039] 2) Antioxidant performance testing (DPPH free radical scavenging rate) Test method: Referring to GB / T 31740.2-2015 Determination of antioxidant activity of plant extracts Part 2: DPPH method, the product was prepared into a solution with a selenium concentration of 50 μg / mL, and its scavenging rate of DPPH free radicals was determined. The results are shown in Table 2.

[0040] Table 2

[0041] As shown in the table above, the DPPH free radical scavenging rate of Examples 1-5 is 75%-88%, indicating excellent antioxidant performance; while the scavenging rate of Comparative Examples 1-3 is ≤25%, with no obvious antioxidant activity.

[0042] The cell viability of Examples 1-5 was ≥85%, demonstrating good biocompatibility; the cell viability of Comparative Examples 1-3 was ≤40%, indicating high biotoxicity.

[0043] 2. Detection of the foliar fertilizer application effect of nano-selenium composite materials: Foliar fertilizer preparation: The graphene-supported nano-selenium samples obtained in Examples 1–5 were mixed with NPK compound fertilizer (N:P:K=15:15:15), and the amount of composite material added was controlled so that the final concentration of selenium in the foliar fertilizer was 200 mg / kg, and a foliar fertilizer aqueous solution with a mass fraction of 0.5% was prepared.

[0044] Application method: Use conventional agricultural spraying equipment to evenly spray the foliar fertilizer solution onto the surface of the leaves of crops such as wheat, rice, and broccoli. Spray once every 7 days for a total of 3 times. Spray before 9 am or after 5 pm and avoid strong sunlight.

[0045] The selenium content of crops after maturity was tested according to the national food safety standard GB 5009.93-2017, "Determination of Selenium in Food". The results showed that the selenium content of crops sprayed with the nano-selenium composite foliar fertilizer of this invention was 0.15-0.35 mg / kg, which met the national standard for selenium-enriched agricultural products (GB / T 22499-2008), and the crops grew well and had significantly improved stress resistance. In contrast, the selenium content of crops sprayed with sodium selenite aqueous solution of equal selenium content was 0.05-0.12 mg / kg, and some crops showed mild poisoning symptoms such as yellowing leaves.

[0046] 3. Application of nano-selenium composite materials in food anti-oxidation and preservation The graphene oxide-supported selenium nanocomposite material obtained in Example 2 was prepared into an aqueous solution with a selenium concentration of 100 μg / mL. Fresh strawberries were soaked in the solution for 5 minutes, then removed, air-dried, and stored in a sealed container at room temperature. Strawberries soaked in water served as a blank control group, while strawberries soaked in sodium selenite aqueous solution (selenium concentration of 100 μg / mL) served as a positive control group.

[0047] On the 7th day of storage, the rot rate and vitamin C content of strawberries were tested according to the "GB 2760-2021 National Food Safety Standard for the Use of Food Additives". The results showed that the rot rate of strawberries treated with the composite material of the present invention was ≤10%, and the vitamin C retention rate was ≥70%; the rot rate of strawberries in the positive control group was ≥35%, and the vitamin C retention rate was ≤45%; the rot rate of strawberries in the blank control group was ≥60%, and the vitamin C retention rate was ≤30%. This indicates that the nano-selenium composite material of the present invention has excellent antioxidant and preservation effects on food.

Claims

1. A method for preparing nano-selenium, characterized in that, Includes the following steps: Using sodium selenate or sodium selenite as raw material A and mercaptographene as raw material B, raw material A and raw material B are mixed and reacted for a certain period of time to obtain nano-selenium.

2. The preparation method according to claim 1, characterized in that, Raw material A and raw material B are mixed in solution form.

3. The preparation method according to claim 1, characterized in that, The thiol graphene is thiol-modified graphene or graphene oxide.

4. The preparation method according to claim 3, characterized in that, The preparation method of mercaptographene is to mix and react a dispersion of graphene or graphene oxide with a mercapto-containing reagent to obtain mercaptographene.

5. The preparation method according to claim 4, characterized in that, The thiol-containing silanizing agent is a mercaptosilane, a thiol reagent, or a thiourea reagent.

6. The preparation method according to claim 5, characterized in that, The mercaptosilane is (3-mercaptopropyl)trimethoxysilane, mercapto-polyethylene glycol-silane, or 3-mercaptopropyltriethoxysilane.

7. The preparation method according to claim 5, characterized in that, The thiol reagent is mercaptoethylamine or L-cysteine, and it is used in the form of an ethanol solution with a concentration of 0.1% to 50%.

8. The preparation method according to claim 4, characterized in that, The graphene or graphene oxide dispersion is a dispersion of graphene or graphene oxide in water, ethanol or methanol.

9. A nano-selenium, characterized in that, It is prepared by the preparation method described in any one of claims 1-8.

10. An application of nano-selenium, characterized in that, The nano-selenium is prepared by any one of the preparation methods described in claims 1-8 and is used as an effective ingredient in fertilizers, food anti-oxidation and preservation, industrial catalysis, or chemical analysis.

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