Preparation method and application of nano-cutting flower fresh-keeping liquid of selenium atom doped carbon quantum dots

Abstract

The application belongs to the field of fresh flower preservation technology, and relates to a preparation method and application of a nano-cut flower preservation liquid of selenium atom doped carbon quantum dots, the preservation liquid comprising a bactericide, a growth regulator and selenium atom doped carbon quantum dots, and water being used as a solvent. The Se-CQDs are prepared through hydrothermal reaction of citric acid and selenomethionine. In the preparation, Se-CQDs powder is mixed with water to adjust pH to obtain a mother liquor, and then the mother liquor is compounded with the growth regulator and the bactericide. In the application, the cut flower stem base is first inserted into the preservation liquid for pretreatment, and then inserted into the same or diluted preservation liquid for preservation. The application utilizes the endogenous antioxidant function of Se-CQDs and the exogenous antibacterial effect of the bactericide to form a synergistic preservation mechanism, can effectively inhibit flower stem conduit microbial blockage, remove active oxygen free radicals, reduce membrane lipid peroxidation damage, significantly delay cut flower aging, prolong the vase life and improve the ornamental quality, is simple to operate, and is suitable for industrial application.

Description

Technical Field

[0001] This invention belongs to the field of flower preservation technology, and relates to a method for preparing and applying a nano-cut flower preservation liquid doped with selenium atoms and carbon quantum dots. Background Technology

[0002] As an important ornamental agricultural product, maintaining the quality of cut flowers after harvest and extending their shelf life are key issues for the industry's development. After being separated from the parent plant, cut flowers are subject to multiple stresses, including water imbalance, microbial infection, nutrient depletion, and endogenous hormone disorders, which cause them to wilt rapidly, age quickly, and lose their commercial value.

[0003] Currently, commercial cut flower preservative solutions mainly rely on combinations of the following conventional ingredients: 1) carbohydrates (such as sucrose) as a respiratory matrix and osmotic regulator; 2) bactericides (such as 8-hydroxyquinoline salt and hypochlorite) to inhibit vascular blockage and microbial growth; 3) organic acids (such as citric acid) to lower pH, inhibit bacteria, and stabilize the solution; and 4) plant growth regulators (such as cytokinin 6-BA) to delay senescence. However, these traditional formulations have significant limitations: firstly, long-term use of chemical bactericides may lead to pathogen resistance and is not environmentally friendly; secondly, they are insufficient in specifically inhibiting oxidative senescence processes such as membrane lipid peroxidation caused by the accumulation of reactive oxygen species (ROS); and thirdly, the ingredients are relatively simple, with limited synergistic effects, and there is still considerable room for improvement in the preservation effect of cut flowers such as anthuriums whose stems are prone to lignification and blockage.

[0004] In recent years, nanomaterials have shown great potential in the field of agricultural preservation. Carbon quantum dots (CQDs), as carbon-based zero-dimensional nanomaterials with dimensions typically less than 10 nm, possess excellent water solubility, biocompatibility, low toxicity, and ease of surface functionalization. Current technologies for the preservation of cut flowers primarily focus on nano-silver (antibacterial) and nano-titanium dioxide (photocatalysis). However, research on carbon-based nanomaterials with multiple functions, including antioxidant, antibacterial, and potential promotion of water absorption / conduction, especially selenium-doped carbon quantum dots (Se-CQDs), is relatively lacking. How to efficiently and environmentally prepare stable Se-CQDs, and how to scientifically combine them with traditional high-efficiency preservatives (such as hypochlorous acid) to construct a synergistic composite system, is a pressing issue that needs to be addressed to solve problems such as blueing of the spathe, stem bending, water imbalance, and short vase life that commonly occur in anthurium cut flowers after harvest. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a method for preparing and applying a nano-cut flower preservative solution doped with selenium atoms and carbon quantum dots. The nano-cut flower preservative solution comprises 10-200 mg / L of bactericide, 10.0505-51 g / L of growth regulator, and 0.05-5 mg / mL of Se-CQDs (based on selenium atomic mass), with water as the solvent.

[0006] Preferably, the growth regulator comprises 10-50 g / L sucrose, 50-500 mg / L citric acid, and 0.5-10 mg / L 6-benzylaminopurine (6-BA).

[0007] Preferably, the bactericide is one or more selected from hypochlorite, 8-hydroxyquinoline salt, and thiabendazole. Most preferably, the bactericide is sodium hypochlorite and 8-hydroxyquinoline salt.

[0008] The preparation method of the nano-cut flower preservative liquid includes the following steps: Se-CQDs powder was mixed with ultrapure water, and the pH was adjusted to 6.5-7.5 with alkali solution to obtain Se-CQDs stock solution. The Se-CQDs stock solution, growth regulator, and bactericide were then mixed to obtain nano-cut flower preservative solution.

[0009] Preferably, the alkaline solution is a 0.1-1 mol / L NaOH solution.

[0010] Preferably, the Se-CQDs powder is prepared by dissolving citric acid and selenomethionine in water at a molar ratio of (2.5-3):1, with a total mass concentration of 180-220 mg / mL. The mixture is stirred at 20-30°C until dissolved, sonicated at 100-300 W for 10-20 min, heated at 2-3°C / min to 195-205°C, and reacted at a constant temperature for 4.5-5.5 h. After cooling to room temperature, the mixture is centrifuged at 2-8°C and 8000-12000 rpm for 10-20 min. The supernatant is collected and dialyzed in a dialysis bag with a molecular weight cutoff of 8000-12000 Da for 24-72 h, with the dialysate being replaced every 6 h. The dialysate is water. After dialysis, the mixture is frozen at -80°C for 12 h and freeze-dried at -80°C and <10 Pa for 24-72 h to obtain selenium-doped carbon quantum dots (Se-CQDs).

[0011] This invention also provides a method for using nano-cut flower preservation liquid. Taking anthurium cut flowers as an example, within 2 hours after harvesting the anthurium cut flowers, the base of the flower stem is inserted into the nano-cut flower preservation liquid to a depth of 5-10cm and treated at 12-18℃ for 2-8 hours. The cut flowers are then removed and inserted into the same or 1 / 2 concentration of nano-cut flower preservation liquid for preservation.

[0012] The present invention has the following advantages: (1) Constructing a complete technology chain from nanomaterials to application products. This invention provides a novel green preparation method for selenium-doped carbon quantum dots (Se-CQDs), and based on this, develops a dedicated core mother liquor and compound preservation liquid for cut flowers. By atomically doping, selenium, which has a clear antioxidant physiological function, is stably bound to the carbon quantum dot framework, creatively introducing highly efficient and stable nanoscale antioxidant active ingredients for cut flower preservation.

[0013] (2) The preservation mechanism is highly efficient and significantly superior to traditional formulas. The prepared compound preservation solution cleverly combines the intrinsic antioxidant function of Se-CQDs with the external antibacterial effect of chemical bactericides (such as hypochlorous acid), forming a dual synergistic preservation mechanism of "internal antioxidant" and "external antibacterial". This system can not only effectively inhibit the blockage of flower stem vascular bundles by microorganisms, but also remove reactive oxygen free radicals accumulated during aging at the cellular level, reducing membrane lipid peroxidation damage, thereby significantly extending the vase life and comprehensively improving the ornamental quality of various cut flowers such as anthuriums and roses.

[0014] (3) The product system is systematic and standardized, facilitating industrial application. This invention establishes a standardized product system of "Se-CQDs powder → core mother liquor → terminal compound solution". The core mother liquor has good stability, is easy to store and transport, and end users can quickly dilute and compound according to their needs, making the operation simple. For specific flowers such as Anthurium, the corresponding postharvest processing parameters have also been optimized to form a complete solution that is replicable and easy to promote, greatly reducing the threshold for large-scale application. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0016] Figure 1 Characterization map of Se-CQDs Figure 1 a is a transmission electron microscope image. Figure 1 b is the infrared spectrum. Figure 1 c represents the state of the Se-CQDs aqueous solution under sunlight and ultraviolet light. Figure 1 d is the X-ray photoelectron spectrum.

[0017] Figure 2 The fluorescence spectrum of Se-CQDs is shown.

[0018] Figure 3 This is a diagram showing the sensory changes of cut anthurium flowers during their shelf life.

[0019] Figure 4 This is a rating chart for the shelf life of Anthurium cut flowers.

[0020] Figure 5 The spathe and spadix of Anthurium cut flowers L * Value change graph.

[0021] Figure 6 The spathe and spadix of Anthurium cut flowers a * Value change graph.

[0022] Figure 7 The spathe and spadix of Anthurium cut flowers b* Value change graph. Detailed Implementation

[0023] The technical solutions in the embodiments of the invention are described clearly and completely below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] The Se-CQDs in the following examples and comparative examples were prepared by the following methods: Step 1: Dissolve 5g of citric acid and 2g of selenomethionine (molar ratio approximately 2.55:1) in 30mL of ultrapure water, with a total mass concentration of approximately 233mg / mL. Stir magnetically at 25℃ and 500rpm for 30min until the solid is completely dissolved, resulting in a clear and transparent mixed solution. Ultrasonically treat the solution at 200W for 15min to remove dissolved gases and further homogenize the solution.

[0025] Step 2: Transfer the above solution to a 50 mL polytetrafluoroethylene liner, seal it in a stainless steel reactor, place the reactor in an oven, raise the temperature to 200°C at a rate of 2.5°C / min, and keep the temperature constant at 200±2°C for 5 hours.

[0026] Step 3: After the reaction is complete, allow it to cool naturally to room temperature. Centrifuge the reaction solution at 4°C and 10,000 rpm for 15 minutes, collect the supernatant, and place it in a dialysis bag with a molecular weight cutoff of 10 kDa. Dialyze the bag in 4 L of ultrapure water using a magnetic stirrer, changing the dialysis solution every 6 hours for a total of 48 hours to thoroughly remove unreacted small molecules and ions. After dialysis, pre-freeze at -80°C for 12 hours and dry at -80°C and <10 Pa for 4 hours to obtain a loose, pale yellow solid powder, which is Se-CQDs. Store it in a sealed container away from light.

[0027] Characterization results and analysis Morphology and particle size: such as Figure 1 As shown in a, the prepared Se-CQDs are approximately spherical, well dispersed, and without obvious agglomeration. The statistical particle size distribution is mainly in the range of 2-5 nm, with an average particle size of about 3.5 nm, which is consistent with the dynamic light scattering results.

[0028] (2) Elemental composition and chemical state: such as Figure 1 As shown in Figure d, the sample contains C, O, and Se elements. Peak fitting of the high-resolution Se 3d spectrum revealed two binding energy peaks at 53.90 eV and 54.71 eV, corresponding to Se 3d3 / 2 and Se 3d5 / 2, respectively. These binding energies are lower than elemental selenium (~55.0 eV) but higher than Se(VI) in selenates, confirming that selenium exists in a valence state between 0 and +4, successfully doping sp into carbon quantum dots. 2 In the carbon skeleton, C-Se bonds are formed, rather than through physical adsorption.

[0029] (3) Optical properties: Under 365 nm ultraviolet light irradiation, Figure 1 As shown in c, the Se-CQDs aqueous solution emits bright blue fluorescence. Fluorescence spectrum ( Figure 2 The results show that its optimal excitation wavelength is 300 nm, and under this excitation, the maximum emission wavelength is 418 nm. This strong fluorescence property originates from the quantum confinement effect of the carbon nucleus and its surface states; selenium doping may modulate its electronic structure.

[0030] (4) Surface groups: Figure 1 b is displayed at 3400cm -1 (-OH / NH), 1720cm -1 (C=O) and 1400cm -1 The presence of characteristic absorption peaks near CO indicates that the surface of Se-CQDs is rich in hydrophilic functional groups such as carboxyl and hydroxyl groups, which is also an important reason for its excellent water solubility.

[0031] Example 1 1. Preparation of Se-CQDs core mother liquor (component A) Accurately weigh 250 mg of the prepared Se-CQDs powder, dissolve it in 10 mL of ultrapure water to prepare a stock solution of 25 mg / mL (based on solids), adjust the pH to 6.5-7.5 with 0.5 mol / L NaOH solution, and store at 4 °C protected from light.

[0032] 2. Preparation of the basic preservative solution (component B) Prepare two base solutions: (1) Basic solution I: Dissolve 30g sucrose, 300mg citric acid, 25mg 8-hydroxyquinoline citrate and 20mg 6-BA in 1L deionized water, stir until clear, and adjust the pH to 3.8 with 0.5mol / L hydrochloric acid aqueous solution.

[0033] (2) Base solution II: Add sodium hypochlorite solution to 1L of deionized water to adjust its effective chlorine concentration to 50mg / L, and adjust the pH to 4.0 with 0.5mol / L dilute hydrochloric acid aqueous solution.

[0034] 3. Preparation of Nano-cut Flower Preservative Solution Using 1L of basic preservation solution (component B) as the matrix (basic solution I:basic solution II = 1:1 (v / v)), 10mL of Se-CQDs standard stock solution (component A:component B = 1:100 (v / v)) was added to prepare a nano-compound preservation solution with a final concentration (based on selenium atoms) of 0.25mg / L, which was then sealed in a bottle for later use.

[0035] Example 2 The difference between this embodiment and Example 1 is that the volume of Se-CQDs standard stock solution added is 20 mL (component A:component B = 1:50 (v / v)), which prepares a nano-compound preservation solution with a final concentration (calculated as selenium atoms) of 0.5 mg / mL.

[0036] Example 3 The difference between this embodiment and Example 1 is that the volume of Se-CQDs standard stock solution added is 60 mL (component A:component B≈1:16.7 (v / v)), which prepares a nano-compound preservation solution with a final concentration (calculated as selenium atoms) of 1.5 mg / L.

[0037] Example 4 The difference between this embodiment and Example 1 is that the volume of Se-CQDs standard stock solution added is 100 mL (component A:component B = 1:10 (v / v)), which prepares a nano-compound preservation solution with a final concentration (calculated as selenium atoms) of 2.5 mg / L.

[0038] Example 5 The difference between this embodiment and Example 1 is that the volume of Se-CQDs standard stock solution added is 200 mL (component A:component B = 1:5 (v / v)), which prepares a nano-compound preservation solution with a final concentration (calculated as selenium atoms) of 5 mg / L.

[0039] Experimental Example 1 Step 1: Select cut flowers of the 'Feliceta' variety of Anthurium and harvest them in the early morning. The criteria are: the spathe is fully open, the color is bright red, the lower 2 / 3 of the florets of the spadix are open, and the flower stalk is upright (40-50cm in length). Transport them back to the laboratory within 1 hour after harvesting.

[0040] Step two: Make a 2cm oblique cut at the base of the flower stems to refresh the cut, and insert each of the five stems into the nano-cut flower preservation solution prepared in Examples 1-5, using tap water as a control, immersing them to a depth of 7cm. Treat them in a cold room at 14℃ and 85% humidity for 6 hours.

[0041] Step 3: Remove the cut flowers and place them into clean vases containing a new nano-preservative solution (concentration same as in Step 2), using tap water as a control, with 500mL of solution in each vase. Place them in an indoor environment with a temperature of 20±1℃, relative humidity of 60±5%, and light exposure of 12h / d (light intensity of 1500-2000 lux). Change the vase solution every 7 days and measure the sensory indicators of the anthurium cut flowers. The results are shown below. Figure 3-7 .

[0042] The indicator method: Every 10 days, industrial cameras are used to photograph and record the sensory changes of freshly cut anthuriums.

[0043] A standard for evaluating the ornamental quality of Anthurium cut flowers was established (Table 2). Based on phenotypic observations, the ornamental quality grades of cut flowers during their vase life were determined. Color difference: The color difference was measured using a CR-400 fully automatic colorimeter. Five cut anthurium flowers were randomly selected from each group, and measurements were taken at the center of the spathe and the stigma of the spadix. L * , a * , b * value.

[0044] Table 2 Evaluation Criteria for Ornamental Quality of Freshly Cut Anthurium The spathe is brightly colored with a beautiful luster, making it highly ornamental. І Approximately 10%-19% of spathes show discoloration or wilting at the edges. Ⅱ Approximately 20%-29% of the spathes exhibit discoloration, wilting, curling, or drying at the edges, with a significant decrease in gloss. Ⅲ Approximately 30%-49% of spathes show discoloration, wilting, curling, or drying at the edges, losing their luster. Ⅳ Approximately 50% of the spathes showed discoloration, wilting, curling, or drying at the edges, with large areas of browning and rotting. Ⅴ The results are as follows (Note: Since the same batch of samples was used for the day 0 measurements, the same day 0 measurements of the same sample were selected for easier comparison of changes in cut flowers. Some fluctuations in the data during the experiment are normal): Depend on Figure 3It can be seen that, in Comparative Example 1, which only used tap water for treatment, the spathe of the anthurium cut flowers obtained in Example 1 maintained a bright red color, had a small wilting area, and had an intact spadix morphology. In contrast, the spathe of the comparative example showed obvious fading and curling in the later stages of vase arrangement, indicating that the compound solution of the present invention can effectively delay the aging of petals and water loss. Further observation of Examples 2-5 with increased Se-CQDs concentration showed that the spathe preservation effect first increased slightly and then decreased: Example 2 was similar to Example 1, but in Examples 3 to 5, local browning of the spathe edge and premature wilting of the inflorescence gradually appeared with increasing concentration, indicating that the appropriate concentration of Se-CQDs has a synergistic effect of antioxidation and antibacterial activity, while excessively high concentrations may cause oxidative stress and accelerate tissue damage.

[0045] Depend on Figure 4 The sensory scores (including flower stalk uprightness, inflorescence morphology, and leaf condition) showed a decreasing trend over time. Example 1 consistently had the highest score throughout the observation period, indicating its best overall preservation performance. Comparative Example 1 showed the fastest score decline, indicating a lack of active ingredients that prevented the maintenance of the cut flowers' physiological vitality. While Examples 3-5 had acceptable scores initially, their scores rapidly declined in the later stages due to the potential toxicity of high selenium concentrations, which accelerated flower stalk softening and leaf yellowing.

[0046] Depend on Figure 5 , Figure 6 and Figure 7 As shown in the color difference curves, Example 1 exhibited the slowest color difference change throughout the entire vase life, demonstrating significantly better color stability than Comparative Example 1 (tap water) and all high-concentration Se-CQDs treatment groups (Examples 3-5). The color difference value of the spathe in the Comparative Example decreased rapidly on day 7, indicating severe color deterioration. While Examples 4-5 showed little change in color difference initially, significant fluctuations occurred later, possibly related to abnormal pigment degradation caused by metabolic disorders at high selenium concentrations. This result further confirms that the 0.25 mg / L Se-CQDs compound solution provides optimal sustained-release protection in maintaining the vibrant red color of the anthurium spathe.

[0047] In summary, this invention utilizes a basic preservative solution containing sugar acid, growth regulators, and bactericides as a matrix, supplemented with 0.25 mg / L (based on selenium atoms) of Se-CQDs to create a nano-compound preservative system. This system synergistically maintains the moisture balance of cut anthurium flowers, inhibits microbial proliferation, and delays oxidative browning and pigment degradation, thereby significantly extending vase life and maintaining excellent ornamental quality. This effect is significantly superior to single water treatments and treatments with excessively high or low Se-CQDs concentrations, demonstrating the advantages of this invention in the design and concentration optimization of the nano-selenium carbon quantum dot compound preservative solution, which can extend the ornamental period of fresh-cut anthuriums to 14 days.

[0048] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A selenium-doped carbon quantum dot nano-flower preservative solution, characterized in that, It includes 10-200 mg / L of bactericide, 10.0505-51 g / L of growth regulator, and 0.05-5 mg / mL of Se-CQDs based on the atomic mass of selenium, with water as the solvent.

2. The selenium-doped carbon quantum dot nano-flower preservative liquid according to claim 1, characterized in that, The growth regulators include 10-50 g / L sucrose, 50-500 mg / L citric acid, and 0.5-10 mg / L 6-BA.

3. The selenium-doped carbon quantum dot nano-flower preservative liquid according to claim 1, characterized in that, The bactericide is one or more of hypochlorite, 8-hydroxyquinoline salt, and thiabendazole.

4. The selenium-doped carbon quantum dot nano-flower preservative liquid according to claim 3, characterized in that, The bactericide is sodium hypochlorite and 8-hydroxyquinoline salt.

5. The selenium-doped carbon quantum dot nano-flower preservative liquid according to claim 1, characterized in that, The Se-CQDs powder is prepared by dissolving citric acid and selenomethionine in water at a molar ratio of (2.5-3):1, with a total mass concentration of 180-220 mg / mL. The mixture is stirred until dissolved, sonicated, and reacted at 195-205℃ for 4.5-5.5 h. After cooling to room temperature, the mixture is centrifuged, the supernatant is collected and dialyzed, and then freeze-dried to obtain Se-CQDs powder.

6. The method for preparing the nano-cut flower preservative liquid according to any one of claims 1-5, characterized in that, Se-CQDs powder is mixed with ultrapure water, and the pH is adjusted to 6.5-7.5 to obtain Se-CQDs stock solution. Se-CQDs stock solution, growth regulator and bactericide are mixed to obtain nano-cut flower preservation solution.

7. The preparation method according to claim 6, characterized in that, Adjust the pH using 0.1-1 mol / L NaOH solution.

8. The application of the nano-cut flower preservative liquid according to any one of claims 1-5 in the field of flower preservation.

9. The application according to claim 8, characterized in that, Within 2 hours of harvesting Anthurium cut flowers, insert the base of the flower stem into a nano-cut flower preservation solution to a depth of 5-10cm and treat at 12-18℃ for 2-8 hours. Then, remove the cut flowers and insert them into the same or half concentration of the nano-cut flower preservation solution for preservation.

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