Method for green synthesis of nano-silver from purple cabbage extract

Abstract

The invention discloses a method for green synthesis of nano-silver from a purple cabbage extract, which belongs to the field of nanotechnology, and comprises the following steps: 1) washing purple cabbage with distilled water, airing, chopping, weighing 50-60g of purple cabbage, adding 100mL of distilled water, heating and boiling for 5 minutes, cooling to the temperature, and carrying out vacuum filtration to obtain purple water extract; the method comprises the following steps of (1) preparing a purple cabbage water extract, (2) adding distilled water to dilute the purple cabbage water extract to 250mL, and storing the purple cabbage water extract and 0.001 mol / L silver nitrate at 4 DEG C for later use, and (3) mixing the purple cabbage water extract and 0.001 mol / L silver nitrate according to a volume ratio of (1-9): (9-1), placing the mixture under the irradiation of a xenon lamp light source under magnetic stirring, and reacting for 1-40min. Nano-silver particles are spherical or ellipsoidal, part of the nano-silver particles are slightly agglomerated, the particle diameter is about 10nm, the particle size is relatively uniform, and the nano-silver yield is 99.96%.

Description

Technical Field

[0001] The invention belongs to the field of micro-nano technology, and particularly relates to a method for green synthesis of nano silver from purple cabbage extract. Background Art

[0002] Silver nanoparticles (Ag-NPs) are known as the new generation of antibacterial agents in the 21st century. They have broad-spectrum and efficient antibacterial properties, long-lasting antibacterial properties, strong permeability, safety and non-toxicity, repair and regeneration, and are not easy to make microorganisms resistant. Nanosilver has been widely used in various medical materials, such as wound dressings, surgeons' masks, medical catheters, medical surgical instruments, implanted human tissues, etc. Based on the excellent antibacterial properties of nanosilver, its application prospects are broad, and there is a wide market demand in the fields of daily necessities, medical and health fields, building materials fields, and electronic industries. Common methods for preparing nanosilver include chemical reduction, physical reduction, and biological reduction. Chemical methods include: liquid phase chemical reduction, adsorption in situ reduction, ethylene glycol hydrothermal reduction, electrochemical method, photochemical reduction, and other chemical methods; physical methods include: reduction ball milling, ultrasonic reduction, microwave-assisted reduction, photoquantum reduction, evaporation condensation, and atomization; biological reduction uses natural plant extracts as reducing agents and stabilizers to prepare nanosilver. Among them, chemical methods are more common, but the reducing agents and stabilizers used are mostly toxic reagents, which seriously pollute the environment. At the same time, the reaction conditions need to be strictly controlled, and the preparation technology requirements are very high. Summary of the invention

[0003] The purpose of the present invention is to solve the above problems and provide a method for green synthesis of nanosilver from purple cabbage extract.

[0004] The method for green synthesis of nanosilver using purple cabbage extract comprises:

[0005] 1) Rinse the purple cabbage with distilled water, dry it, chop it, weigh 50-60 grams, add 100 mL of distilled water, heat and boil for 5 minutes, cool to room temperature, and vacuum filter to obtain the purple water extract;

[0006] 2) Dilute to 250 mL with distilled water and store at 4°C for later use;

[0007] 3) Mix the purple cabbage water extract and 0.001 mol∙L -1 Silver nitrate, mixed in a volume ratio of 1-9:9-1, placed under a xenon lamp light source under magnetic stirring, and reacted for 1-40 minutes;

[0008] The light intensity is 1W∙cm 2 , react for 1 to 20 minutes;

[0009] The volume ratio is 8:2, and the reaction time is 20 minutes.

[0010] The present invention provides a method for green synthesis of nanosilver from purple cabbage extract, which comprises: 1) rinsing the purple cabbage with distilled water, drying it, chopping it, weighing 50-60 grams, adding 100 mL of distilled water, heating and boiling it for 5 minutes, cooling it to room temperature, and vacuum filtering it to obtain a purple water extract; 2) diluting it to 250 mL with distilled water, and storing it at 4°C for later use; 3) mixing the purple cabbage water extract with 0.001 mol∙L -1 Silver nitrate is mixed in a volume ratio of 1-9:9-1, and placed under a xenon light source under magnetic stirring for 1-40 minutes. The nanosilver particles are spherical or ellipsoidal, and some nanosilver particles are slightly agglomerated. The particle diameter is about 10nm, and the particle size is relatively uniform. The yield of nanosilver is 99.96%. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 UV-visible absorption spectra of synthesized nanosilver with different volume ratios of reaction solution;

[0012] Figure 2 UV-visible absorption spectra of silver nanoparticles at different reaction time intervals (every 5 min);

[0013] Figure 3 UV-visible absorption spectra of synthesized nanosilver under different light intensities;

[0014] Figure 4 Infrared spectrum of purple cabbage extract;

[0015] Figure 5 TEM electron microscope image of nanosilver;

[0016] Figure 6 XRD pattern of nanosilver. DETAILED DESCRIPTION

[0017] Example 1 Green Synthesis of Nanosilver

[0018] Purple cabbage was purchased from a local supermarket. Silver nitrate was produced by Sinopharm Chemical Reagent Co., Ltd. All experimental water was ultrapure water (resistivity 18.2 MΩ∙cm).

[0019] BBZM-I xenon lamp, Anhui Langxi Bobei Lighting Appliance Factory; TGL16 desktop high-speed centrifuge, Jiangsu Gaoke Instrument Factory; TU1901 UV spectrophotometer, Beijing Spectrum General Instrument Co., Ltd.; (EDS X-MAX50) emission scanning electron microscope (SEM), FEI-NOVA NANOSEM 230, USA; X-ray polycrystal diffraction (XRD), BRUKER D8ADVANCE, Germany; ZDF-6020 vacuum drying oven, Lichen Technology Co., Ltd.

[0020] Calculation of nanosilver yield:

[0021] Purple cabbage water extract and 0.001 mol∙L -1 50 mL of nanosilver sol generated by the silver nitrate solution with a volume ratio of 8:2 was centrifuged at 10000 r / min for 30 min. The supernatant was taken and the concentration of the remaining silver ions was determined by ICP spectrometer. The yield of nanosilver was calculated by the following formula:

[0022] Yield = (1- )×100%

[0023] 1. Green synthesis of nanosilver

[0024] After the purple cabbage was rinsed with distilled water, it was dried and chopped. 50 g of the purple cabbage was weighed, and 100 mL of distilled water was added to boil for 5 min. The purple water extract was obtained by vacuum filtration, and then diluted to 250 mL with distilled water and stored at 4 °C for later use. -1 Silver nitrate and purple cabbage water extract were mixed in different volume ratios (1:9, 2:8, 3:7, 4:6, 5:5, 6:4, 7:3, 8:2, 9:1) and irradiated under a 350W xenon lamp light source for a certain period of time (0-40min) under magnetic stirring. When the reaction was completed, the mixed solution changed from light purple to reddish brown, and the product was verified by UV-visible absorption spectroscopy.

[0025] 2. Optimization of Nanosilver Preparation Conditions

[0026] 1) Effect of reactant volume ratio

[0027] The purple cabbage extract and 0.001 mol∙L -1 The volume ratios of AgNO3 were 9:1, 8:2, 7:3, 6:4, 5:5, 4:6, 3:7, 2:8 and 1:9, respectively, and the illumination intensity was 1 W∙cm 2 After 20 minutes of reaction, the UV-visible absorption spectrum of the solution was measured. Figure 1 As shown. In the wavelength range of 400-450nm, nanosilver will have a typical absorption peak. Figure 1It can be observed that the surface plasmon resonance absorption peak of nanosilver is in the wavelength range of 407nm-437nm, which proves that nanosilver is generated under the above reaction conditions. When the volume ratio of purple cabbage to silver nitrate solution is 9:1, the absorption peak of the generated nanosilver is located at 407nm. When the reaction ratio of the two is gradually reduced to 1:9, the absorption peak of nanosilver gradually red-shifts from 407nm to 437nm, indicating that the particle size of nanosilver gradually increases. This may be due to the reduction in the proportion of purple cabbage water extract, and the generated nanosilver particles agglomerate close to the silver core, making the nanosilver particle size larger and the ultraviolet-visible absorption peak red-shifted. When the volume of purple cabbage water extract and silver nitrate is 8:2, the ultraviolet-visible spectrum absorbance value of nanosilver is the largest, at 414nm, and from Figure 1 It can also be seen from the color illustration that the color of the nanosilver solution is the darkest at this reaction ratio, indicating that the concentration of nanosilver in the solution is the highest. Therefore, the volume ratio of purple cabbage water extract to silver nitrate was determined to be 8:2 as the optimal reaction ratio for subsequent research.

[0028] 2) Impact of reaction time

[0029] After mixing the purple cabbage water extract and silver nitrate in a volume ratio of 8:2, the light intensity was 1W∙cm 2 2 mL of the reaction solution was taken out every 5 minutes for UV-visible spectrum scanning. The results are as follows Figure 2 As shown. 5 minutes after the reaction started, the characteristic absorption peak of nanosilver appeared at 414nm. As the reaction time increased, the absorbance value gradually increased. This is because the amount of nanosilver generated increased gradually with the extension of the reaction time. Figure 2 It can also be seen that the absorbance value of nanosilver increases rapidly when the reaction time is short from 5min to 20min. After 20min, the absorbance growth rate of nanosilver slows down, indicating that the reaction between purple cabbage water extract and silver nitrate is mainly concentrated in the 0-20min time period of illumination. Considering the time efficiency factor, the optimal reaction time is determined to be 20min

[0030] 3) Effect of light intensity on the reaction

[0031] The purple cabbage water extract was mixed with silver nitrate in a volume ratio of 8:2 and the samples were exposed to different light intensities (1.5 W∙cm 2 , 1W∙cm 2 , 500mW∙cm 2 After 20 minutes of reaction, the UV-visible scanning spectrum of the reaction solution was measured. The results are as follows Figure 3 When the light intensity is 500mW∙cm 2 When the light intensity is 1 W∙cm 2When the light intensity increases to 1.5 W∙cm 2 When the absorbance of the nanosilver solution was 0.872, the increase was not large. Therefore, considering the light utilization rate, the optimal light intensity for the reaction was determined to be 1 W∙cm 2 .

[0032] 4) Calculation of Nanosilver Yield

[0033] The silver ion concentration before the reaction was 21.6 mol∙L -1 (0.001 mol / L×108×1000×2mL÷10 mL). After the reaction, the ICP spectrum measured the silver ion concentration to be 0.009856 mol∙L -1 The calculated nanosilver yield was 99.96%.

[0034] 3) Characterization of Nanosilver

[0035] 1) Infrared spectroscopy

[0036] The infrared spectrum of purple cabbage extract is as follows Figure 4 As shown, 3386cm -1 The stretching vibration of hydroxyl group is 2928cm -1 is the stretching vibration of methylene -CH2-, 1626cm -1 Related to the stretching vibration of carbon-carbon double bond, 1412 cm -1 The methyl group has an angle-variable vibration, 1052 cm -1 The stretching vibration of CO bond and the skeleton vibration of CC single bond are at 800cm -1 Nearby is the out-of-plane bending vibration of the CH bond. These characteristic peaks confirm the presence of flavonoids and phenolic compounds in the purple cabbage water extract, which have reducing properties and can reduce the silver ions in silver nitrate to nanosilver.

[0037] 2) TEM images

[0038] From the transmission electron microscope image of nanosilver ( Figure 5 ) It can be seen that the nanosilver particles are spherical or ellipsoidal, some of the nanosilver particles are slightly agglomerated, the particle diameter is about 10nm, and the particle size is relatively uniform.

[0039] 3) X-ray diffraction analysis

[0040] From the XRD spectrum of nanosilver ( Figure 6 ) It can be seen that the 2θ angle is located at 38.17 ◦ , 44.23 ◦ , 64.57 ◦ , 77.27 ◦ and 81.37◦ There are five diffraction peaks, corresponding to the five crystal planes of nanosilver (111), (200), (220), (311), and (222). In the figure, there is a slight noise, which is due to the presence of a small amount of plant extract on the surface of nanosilver.

Claims

1. A method for green synthesis of nanosilver using purple cabbage extract, comprising: 1) Rinse the purple cabbage with distilled water, dry it, chop it, weigh 50-60 grams, add 100 mL of distilled water, heat and boil for 5 minutes, cool to room temperature, and vacuum filter to obtain the purple water extract; 2) Dilute to 250 mL with distilled water and store at 4°C for later use; 3) Mix the purple cabbage water extract and 0.001 mol∙L -1 Silver nitrate is mixed in a volume ratio of 1-9:9-1, placed under a xenon lamp light source under magnetic stirring, and reacted for 1-40 minutes.

2. The method for green synthesis of nanosilver from purple cabbage extract according to claim 1, characterized in that: The light intensity is 1W∙cm 2 , reaction time 1 to 20 minutes.

3. The method for green synthesis of nanosilver from purple cabbage extract according to claim 2, characterized in that: The volume ratio is 8:2, and the reaction time is 20 minutes.

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