CN110681875B

CN110681875B - Isosteviol metal gel and preparation method and application thereof

Info

Publication number: CN110681875B
Application number: CN201911100567.5A
Authority: CN
Inventors: 张涛; 白素平; 房立真; 樊高省; 王克杰; 邱培勇; 王亚坤; 吕洁丽; 张明亮
Original assignee: Xinxiang Medical University
Current assignee: Henan Minjian Dental Materials Co ltd
Priority date: 2019-11-12
Filing date: 2019-11-12
Publication date: 2022-05-17
Anticipated expiration: 2039-11-12
Also published as: CN110681875A

Abstract

The invention discloses isosteviol sulfonic acid silver supramolecular gel, a preparation method thereof and application thereof in nano-silver preparation, belonging to the field of functional materials. The gel is prepared from natural product isosteviol through esterification, sulfonation and salification, and has silver sulfonate structural fragments. The structure is shown as formula 1, wherein R is alkyl or aromatic alkyl. The gel has good gel performance, the minimum gel concentration is as low as 0.2% w/v, and the nano-silver can be prepared in situ through a green and convenient photoinduced reduction process. The gel system has simple preparation method, low cost and recyclable solvent. The prepared nano silver has uniform particle size and simple method, and provides a convenient template for the preparation of the nano silver.

Formula 1.

Description

Isosteviol metal gel and preparation method and application thereof

Technical Field

The invention discloses isosteviol sulfonic acid silver supramolecular gel, a preparation method thereof and application thereof in nano-silver preparation, belonging to the field of functional materials.

Background

The nano metal particles are ultra-fine metal particles with the size less than 100nm, and are an important research direction in nano science. The nano silver has good optical, mechanical, thermal and biological activity, so the nano silver has wide application prospect in the fields of optical devices, biomedicine, high-performance electrode materials, coatings, conductive paste, sensors and the like. The preparation of the nano metal particles generally comprises a physical grinding method, an inert gas condensation method, a plasma method, a biological reduction method, a reverse microemulsion method, a liquid phase reduction method and the like. In the currently reported preparation method, dispersing agent, stabilizing agent, reducing agent and the like are needed due to the defects of uneven particle size, easy agglomeration and the like of the nano silver particles, so that the cost is increased, pollution is caused, and the wide application of the prepared nano silver is not facilitated.

Patent CN106180753B discloses a method for preparing nano silver by agarose gel. The method uniformly distributes silver ions into a gel system, and the silver ions are reduced into nano silver particles by utilizing the reducibility of agarose, but the preparation of the gel needs a heating and cooling process, and the self-reduction process even needs 1-15 days. 201810939378.6 patent reports that nano silver is prepared in solution, but the chitosan oligosaccharide-hydrazine hydrate thiourea derivative is used as a reducing agent, which increases the cost and causes pollution.

Compared with the traditional preparation method, the supermolecular gel can prepare the single-component or multi-component mixture (molecular-level mixing) nano metal particles with high purity, uniform particle size distribution and high chemical activity at low temperature. In addition, the size and the shape of the metal nano-particles prepared by the method can be controlled by changing the concentration of the initial solution of the reactants and the post heat treatment process. Therefore, the coordination silver supermolecule gel system is provided, and the coordination silver supermolecule gel system is used as a template to realize the preparation of the nano silver particles under the irradiation of natural light or an external light source, so that the coordination silver supermolecule gel system has important application value.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention aims to provide the isosteviol supramolecular metal gel which has good stability and is not easy to agglomerate; the other purpose is to provide the preparation method, which is simple, mild, low in cost and environment-friendly for preparing the target product.

In order to realize the purpose of the invention, the silver sulfonate supramolecular gel is prepared by taking isosteviol as a raw material and carrying out esterification, sulfonation and salification. In the specific operation, the reaction substrate, the solvent, the temperature, the purification process and the like are optimized, the yield is improved, the cost is reduced, and all the solvents can be recycled.

The technical scheme adopted by the invention is as follows:

the isosteviol supramolecular metal gel disclosed by the invention has a structure shown in a general formula 1:

wherein R is n-propyl, isopropyl, n-butyl, isobutyl, n-pentyl, n-hexyl, n-decyl, n-hexadecyl, phenethyl or benzyl.

Silver isosterviol sulfonate gels represented by formula 2, formula 3 and formula 4 are preferred:

the invention provides a synthesis method of the derivative, which comprises the following reaction processes:

the specific method comprises the following steps:

(1) adding an acid-binding agent, reacting isosteryl alcohol (compound 1) with a halogenated compound in an organic solvent, evaporating the solvent after the reaction is finished, adding dilute hydrochloric acid into the solvent to wash a crude product, filtering and drying to obtain a compound 2.

The solvent is one or more of DMF, DMSO, acetonitrile, ethyl acetate, toluene, xylene, tetrahydrofuran, dioxane or diethyl ether; halo is chlorohydrocarbon, bromohydrocarbon or iodohydrocarbon; the acid-binding agent is KOH, NaOH or K₂CO₃Or N, N-Dimethylaminopyridine (DMAP).

The reaction temperature in the esterification process is 20-60 ℃; preferably, acetonitrile is used as a solvent, and iodohydrocarbon is used as a reaction reagent to react under the reflux state. The molar ratio of the compound 1 to the halogenated hydrocarbon is 1:1.2 to 1:2, preferably 1: 1.5.

(2) Dropwise adding concentrated sulfuric acid into acetic anhydride at low temperature, and after dropwise adding, adding a solvent and the compound 2 into the system to react until the reaction is finished. Evaporating the solvent to obtain a solid, and adding an organic solvent into the system for recrystallization to obtain a compound 3.

The reaction solvent is toluene, xylene or glacial acetic acid, and excessive acetic anhydride can be added as the solvent; the recrystallization solvent is one or more of ethyl acetate, glacial acetic acid, methanol and ethanol.

Preferably, glacial acetic acid is used as a reaction solvent, and ethyl acetate-ethanol 10:1 is used as a recrystallization solvent.

The reaction temperature is 0-30 ℃, and the reaction time is 8-24 hours. Preferably 0 to 5 ℃.

The concentrated sulfuric acid is selected to have a mass percentage concentration of more than 90%, and the molar ratio of the concentrated sulfuric acid to the acetic anhydride is 1: 5-10.

(3) Adding a recrystallization solution into the compound 3, adding a silver salt aqueous solution or an organic solution thereof, separating an organic phase after washing, separating out silver isostaviol sulfonate crystals, carrying out suction filtration, and washing with a small amount of water to remove redundant silver salt and generated acid.

The recrystallization solvent is one or more of ethyl acetate, ethanol, water, methanol or toluene, an ethyl acetate-ethanol system is preferred, and the silver salt is silver nitrate, silver perchlorate, silver tetrafluoroborate, silver hexafluorophosphate or silver fluoride.

The molar ratio of the silver salt to the compound 3 is 3:1 to 1:1, preferably 1.05: 1.

Dispersing silver isosteviol sulfonate into a gel solvent, and standing the gel solvent at room temperature to gelatinize a system; in situ gelation can also be achieved by adding a solution containing a silver salt to a solution of isotretinoin sulfonic acid 3.

The gel solvent is one or more of chloroform, dichloromethane, 1, 2-dichloroethane, 1, 2-dibromoethane, carbon tetrachloride, bromobutane, bromopropane, isopropyl bromide, bromoethane, toluene, xylene and tetrahydrofuran.

The weight volume ratio of the gel water solution is 0.2% w/v-2% w/v.

The preparation process of the nano silver particles comprises the steps of placing silver isosteviol sulfonate gel with different concentrations under natural light or ultraviolet light of 254-365nm for photoinduced reduction, and gradually blackening the system along with the reaction time.

The natural light illumination time is 1-3 days, and the ultraviolet light reduction time of 254-365nm is 10-50 minutes.

Compared with the prior art, the invention has the following advantages:

1. the coordination type supermolecule silver gel is prepared, the gel preparation does not need a heating and cooling process so as to realize in-situ gelation, the preparation method is simple, the cost is low, the pollution is small, and all solvents can be recycled.

2. Because the silver ions participate in the self-assembly of the gel, the gel fiber has good stability, and the prepared nano silver particles have good compatibility with a gel system, thereby effectively avoiding the agglomeration of the nano silver particles.

3. The solvent adopted by the invention has low boiling point and is easy to volatilize, can be removed by natural volatilization or freeze drying, avoids heating removal, and has simple post-treatment.

4. The method adopts the light reduction at room temperature to prepare the nano silver, does not need a chemical reducing agent in the reduction process, is green and pollution-free, and is easy to operate in experiments without special instruments.

5. The nano silver prepared by the method has good stability and uniform particle size, can be freely regulated and controlled within the range of 20-200nm by regulating the gel concentration and the reduction time, and provides a convenient template for the preparation of the nano silver.

Drawings

FIG. 1 is a scanning electron microscope image of a methylene chloride xerogel of silver isostaivol isopropyl sulfonate of the present invention.

FIG. 2 is a scanning electron microscope image of a xerogel prepared by photoreducing a dichloromethane gel of silver isostaivol isopropyl sulfonate of the present invention for 20 minutes.

Detailed Description

The invention will now be further illustrated by way of examples for better carrying out the invention, which are, however, intended to be illustrative only and not limiting.

Example 1 preparation of silver Isosteviol isopropyl sulfonate

Isotretinol (5g 16mmol) was dissolved in acetonitrile (31mL) and K was added₂CO₃(1.79g, 32mmol), the mixture was stirred with a magnetic stirrer in a 100mL flask, after the isosteviol was dissolved, 1.96g of isopropyl bromide was added, the reaction was refluxed for 6 hours, the progress of the reaction was monitored by TLC, and after completion of the reaction, acetonitrile was distilled off. Adding 200mL of dilute hydrochloric acid with the mass percentage content of 5% into the system, stirring, washing, filtering, repeatedly washing with redistilled water, collecting and drying a filter cake to obtain a white solid isopropyl isostearate (compound 2).

Under the ice-bath condition, 1mL of concentrated sulfuric acid is added into a 50mL volumetric flask, acetic anhydride (6mL) is added into the concentrated sulfuric acid dropwise by using a constant-pressure funnel under stirring, stirring is continued for 10min after the dropwise addition is finished, and 3.7g of isopropyl isosteviol is added into an acetic anhydride-concentrated sulfuric acid system. Stirring until the reaction is complete, evaporating the solvent, adding 150mL of ethyl acetate, and recrystallizing to obtain a compound 3. And adding a silver nitrate aqueous solution with the mass percentage of 10%, washing, separating an organic phase, standing the organic phase to separate out a white solid, filtering, washing and drying to obtain the silver isosteviol isopropyl sulfonate with the yield of 90%.¹H NMR(400MHz,DMSO-d6)δ4.81(m,1H),3.29(s,1H),2.77(d,J＝13.5Hz,1H),2.38(d,J＝10.9Hz,1H),2.17(m,1H),2.00(d,J＝13.0Hz,1H),1.75(m,1H),1.66–1.47(m,3H),1.31(m,3H),1.17(m,6H),1.12(s,1H),1.10(s,3H),1.05(m,1H),0.97(m,3H),0.85(m,4H),0.68(s,3H).¹³C NMR(101MHz,DMSO-d6)δ214.3,176.3,72.1,67.1,57.6,56.9,51.5,47.2,43.5,42.8,39.2,38.3,38.3,37.9,36.0,29.0,22.0,21.9,21.9,20.6,19.5,19.0,13.4.

Example 2 preparation of silver Isosteviol isopropyl sulfonate gel

2mg of the silver isostaviol isopropyl sulfonate compound prepared above was weighed, added to a 5mL pressure-resistant sample bottle, dispersed by ultrasonic after adding a chloroform gel solvent, and allowed to stand for 24 hours. The gels were tested for gel formation and minimum gel concentration using the inversion method. And testing the phase transition temperature under different gel concentrations by a gradient temperature raising method.

EXAMPLE 3 preparation of Nano silver

Placing the isosteviol isopropyl sulfonate silver gel in a bottle, and irradiating for 3 days under natural light or irradiating for 30 minutes by using a 365nm ultraviolet lamp, wherein the system gradually turns black to obtain a nano silver gel system. And transferring the prepared gel system containing the nano silver onto a silicon chip, and naturally airing to obtain a xerogel sample. The gel morphology was observed under a scanning electron microscope after 30 seconds of gold blasting. Self-assembly of the gel into ribbon-like nanostructures can be observed. After photo-reduction, the nano silver is uniformly attached to the gel.

Claims

1. A preparation method of nano-silver is characterized by comprising the following steps: the method is realized by the following steps:

dispersing the silver isostaviol sulfonate derivative shown in the structural formula 1 into a gel solvent at room temperature, and carrying out photoreduction on a silver isostaviol sulfonate gel system to prepare nano silver, wherein a light source adopts natural light or an 254-365nm ultraviolet light source;

wherein R is n-propyl, isopropyl, n-butyl, isobutyl, n-pentyl, n-hexyl, n-decyl, n-hexadecyl, phenethyl or benzyl;

the gel solvent is one or more of chloroform, dichloromethane, 1, 2-dichloroethane, 1, 2-dibromoethane, 1, 4-dibromobutane, carbon tetrachloride, bromobutane, bromopropane, isopropyl bromide, bromoethane, n-hexane, toluene and xylene.

2. The method for preparing nano silver according to claim 1, wherein the weight volume ratio of the aqueous gel solution is 0.2% w/v-2% w/v.