CN114101656A

CN114101656A - Preparation method and application of silver nanoparticles with universal dispersion characteristics

Info

Publication number: CN114101656A
Application number: CN202111485278.9A
Authority: CN
Inventors: 杨士宽; 刘悦; 赵丽妍; 彭娜; 乐敏
Original assignee: Zhejiang University ZJU
Current assignee: Zhejiang University ZJU
Priority date: 2021-12-07
Filing date: 2021-12-07
Publication date: 2022-03-01
Anticipated expiration: 2041-12-07
Also published as: CN114101656B

Abstract

The invention discloses a preparation method and application of silver nanoparticles with universal dispersion characteristics. The invention can conveniently prepare the silver nano particles which can be randomly dispersed in water phase, oil phase, even biological liquid and other complex environments by a one-step electrochemical deposition process. The anionic groups electrochemically anchored to the nanoparticle surface are able to sense and reorient to adapt to the surrounding liquid environment. Such "smart" nanoparticles can be produced by continuous electrodeposition in an electrolyte. The method breaks through the limitation that the traditional electrodeposition method limits the deposit on the surface of the electrode, realizes the high-efficiency preparation of the nano particles, and simultaneously constructs full-automatic electrodeposition equipment to verify the practical applicability of the continuous preparation process of the nano particles. The intelligent silver nanoparticles have excellent colloidal stability, so the intelligent silver nanoparticles have extremely strong antibacterial effect, and can be applied to various actual places (such as rough microporous surfaces of furniture, wood and the like) according to needs.

Description

Preparation method and application of silver nanoparticles with universal dispersion characteristics

Technical Field

The invention relates to a novel particle material, in particular to a silver nanoparticle with universal dispersion characteristic and a preparation method and application thereof.

Background

Colloidal solutions composed of dispersed nanoparticles in a continuous liquid medium have important application values in the fields of opto-electronics, self-assembly, sensing and biomedicine. Generally, the surface of the nanoparticle needs to be coated with macromolecules, other particles or ions to increase the affinity of the colloidal nanoparticle for a solvent and the repulsive force between particles, thereby forming a stable colloid. Electrostatic repulsion between charged nanoparticles is critical for the formation of stable colloids in polar solvents, whereas the surrounding electric double layer of nanoparticles is highly susceptible to collapse and flocculation when exposed to non-polar solvents. Modifying alkane chains (or surface ligands) on the surface of the nanoparticles can increase the repulsion force between the nanoparticles in a nonpolar solvent to form a space-stable nano colloid, and when the nanoparticles are in a polar environment, the surface ligands of the particles tend to shrink, so that the nanoparticles are easy to aggregate and precipitate. Therefore, the surface of the nano-particles can be grafted with a specific type of ligand only to disperse the nano-particles in a certain solvent range, or the nano-particles have a certain dispersion limit. The trade-off for expanding the type of nanoparticle dispersible solvent is to anchor surface ligands of different nature or ligands with complex structures (e.g. amphiphilic ligands) modified at different sites of the nanoparticles at the same time, however, due to the limited degree of conformational structural changes of the ligands, this trade-off also only slightly expands the type of nanoparticle dispersible solvent. Therefore, it is desirable to find a simple way of preparing nanoparticles while achieving natural dispersion of nanoparticles in any phase.

Disclosure of Invention

The invention aims to solve the technical problem of the prior art and provides silver nanoparticles with universal dispersion characteristics, a preparation method and application thereof.

The technical scheme provided by the invention is as follows:

silver nanoparticles with universal dispersion characteristics, wherein an anionic group is chemically bonded to the surface of the silver nanoparticles, and the anionic group has the following structural formula: (C)_nH_2n+1—R)^—In which C is_nH_2n+1Is alkane chain, n is more than or equal to 10, R is acid radical ion, and the acid radical ion and silver salt solution are mixed to form slightly soluble or insoluble salt. Preferably, n.ltoreq.18.

The dispersion medium of the silver nanoparticles may be an oil phase, an aqueous phase or a biological liquid. Because the anion group is fixed on the silver nano-particles through acid radical ion chemical bonding, the alkane chain at the other end can self-adaptively rotate by sensing surrounding liquid so as to adapt to the surrounding environment. In an aqueous phase environment, due to the hydrophobicity of the alkane chain, the alkane chain tends to be close to the surface of the nano particles, and the heads of acid radical ions are exposed, so that an electrostatic repulsion effect among the nano particles is formed, and the nano particles can be stably dispersed in a solvent system. In the organic solvent (oil phase) environment, the alkane chain tends to extend into the organic solvent environment, so that the stable dispersion of the nanoparticles in an organic solvent system is realized through the steric hindrance effect, the universal dispersion characteristic is realized, the stability of the nanoparticles can be maintained for more than several months, and the original colloidal solution can still maintain better stability even if external temperature change (such as temperature rise to 90 ℃ or freezing dissolution) is applied or inorganic salt (such as sodium nitrate) is added.

Further, the organic solvent may be any organic solvent, such as paraffin, olefin, alcohol, aldehyde, amine, ester, ether, ketone, aromatic hydrocarbon, hydrogenated hydrocarbon, terpene hydrocarbon, halogenated hydrocarbon, heterocyclic compound, nitrogen-containing compound, sulfur-containing compound, and the like, and the concentration may be any concentration. The biological fluid is human plasma, and the concentration of the biological fluid is 6.67 percent of the concentration of the normal human plasma.

A preparation method of the silver nanoparticles with universal dispersion characteristics comprises the following steps:

taking an aqueous solution containing silver ions and an anionic surfactant as an electrolyte for electrodeposition, wherein the molar ratio of the silver ions to the anionic surfactant is less than or equal to 1, and acid ions in the anionic surfactant are mixed with a silver salt solution to form a slightly soluble or slightly soluble salt. The electrodeposition voltage is 10V or more.

In the electrolytic solution composed of silver ions and anionic surfactant, unlike traditional electrolytic deposition, which deposits on the surface of electrode, silver nanoparticles will be sprayed into the electrolytic solution from the electrode continuously, forming yellow fog track, because anionic surfactant has strong interaction with silver ions (such as dodecyl sulfate and silver) in the electrolytic solution, when silver ions are reduced to small silver nanoparticles on the surface of cathode electrode, the head of acid radical ion from anionic surfactant will be fixed on silver nanoparticles, making the surface of silver particles carry negative charge, thus forming electrostatic repulsion effect with the cathode surface, and in addition, bubbles (hydrogen, oxygen) generated and detached from the surface of electrode form shearing force to small silver particles, and at the same time, the nanoparticles still have adhesion force with the surface of electrode, thus, three main forces are in competition on the nanoparticles. When the electrode voltage is increased and the concentration of the anionic surfactant is increased, the electrostatic repulsion force borne by the nano particles is increased, so that the formed silver nano particles can be quickly separated from the surface of the electrode and are directly sprayed into a bulk phase solution before the nano particles grow to form a stable colloid dispersion system.

In the electrodeposition system, an arbitrary conductive material is used as a cathode, and a carbon rod is used as an anode. Preferably, the cathode material includes a carbon rod, an aluminum foil, and the like.

Further, the larger the electrodeposition voltage, the smaller the silver nanoparticle size.

Furthermore, the molar ratio of the silver ions to the anionic surface activity is 1: 1-10. The electrodeposition voltage is 10V-100V.

Further, the anionic surfactant is one or more of sodium decyl sulfate, sodium dodecyl sulfate, sodium hexadecyl sulfate and the like which are mixed according to any proportion. The silver salt solution is formed by mixing one or more of silver nitrate solution, silver acetate solution and the like according to any proportion.

Further, the metal salt solution is silver nitrate solution, the anionic surfactant is sodium dodecyl sulfate, and the electrodeposition voltage is 30V.

Further, the method for forming the transferring dispersed silver nano particles obtained by the electro-deposition preparation into colloidal solutions under various environments comprises the following steps: standing the silver colloidal solution obtained by electrodeposition for 10min, taking supernatant, placing the supernatant in a centrifuge, centrifuging the supernatant for 10min at the rotating speed of 18000rpm, carefully removing the supernatant, adding a corresponding dispersion medium into the bottom precipitate, and placing the precipitate in an ultrasonic machine for 5min by ultrasound to obtain a corresponding colloidal dispersion system.

Further, based on the preparation method and universal dispersion characteristics of the silver nanoparticles, it is foreseen that a continuous preparation apparatus may be used to continuously prepare the nanoparticles:

the device for continuously preparing the nano particles mainly comprises four parts, wherein the first part is an electrolytic bath and is used for directly synthesizing the nano particles in a bulk phase solution and forming a colloidal solution system. The second part is a water pump which is used for transferring the formed liquid phase colloidal solution to suction filtration equipment. And the third part is suction filtration equipment for filtering the liquid part and trapping the nano-particle part on the ultrafiltration membrane. The fourth part is a reflux device which is used for partially refluxing the filtered electrolyte to the original electrolytic cell for further electrodeposition. And the operation is repeated in a cycle.

Further, the silver nanoparticles can be applied to sterilization, photoelectric device preparation, 3D printing and colloid chemistry.

The specific application of the sterilization field is as follows: the universal dispersed silver nano-particles can be used for resisting the aggregation caused by flagellin secreted from various bacteria flagella, and the concentration of the flagellin is less than 2.5 mu g/ml. The universal dispersed silver nanoparticles prepared by electrodeposition are more beneficial to the silver nanoparticles to enter bacteria to generate the sterilization effect, and the Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) values of various common bacteria are more than 10 times lower than those of the silver nanoparticles prepared by traditional wet chemistry. Furthermore, the universal dispersed silver nanoparticles can be dispersed in various organic solvents, so that the universal dispersed silver nanoparticles can be sprayed and infiltrated on the surfaces of various materials, and the silver nanoparticles dispersed as required can better permeate into various materials, thereby achieving the long-term, stable and efficient sterilization effect.

The above-mentioned bacteria include: staphylococcus aureus, enterococcus faecium, Streptococcus pneumoniae, Listeria, Salmonella newbauer, Salmonella typhimurium, Salmonella enteritidis, Pseudomonas aeruginosa, Escherichia coli, Klebsiella, Yersinia colitis, Yersinia pseudotuberculosis, and the like.

The invention also provides an intelligent pen which comprises a pen holder, a pen point, a cathode and an anode, wherein the pen holder is filled with the aqueous solution containing the silver ions and the anionic surfactant, and the aqueous solution can be controllably output to the pen point. The anode is arranged in the aqueous solution, the cathode is positioned near the pen point, and the cathode is contacted with the aqueous solution when the aqueous solution is controllably output to the pen point to form liquid drops. Wherein the molar ratio of the silver ions to the anionic surface activity is more than or equal to 1, and the acid radical ions in the anionic surfactant and the silver salt solution are mixed to form slightly soluble or difficultly soluble salt. When the intelligent pen works, the voltage between the cathode and the anode is 10V or more.

Furthermore, the intelligent pen device mainly takes a 100 mL-specification injector as a main body, takes a copper conducting wire as a cathode and an anode, and the cathode copper conducting wire is fixed outside the injector and the tail end of the cathode copper conducting wire is fixed near the injection needle opening. The anode copper wire extends to the inside filled with the electrolyte. When the power is on, the injection rod is pushed, and the nano particles are continuously formed in the liquid drop, so that the track formed by the nano particles can be written on any surface like a pen.

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

the silver nanoparticles prepared by the electrodeposition method can adapt to the surrounding environment through the rotation of the surface ligand, break the dispersion limit of the nanoparticles and allow the silver nanoparticles to be dispersed in a wide solvent range. Meanwhile, the silver nanoparticles can be prepared by continuous electrodeposition, and a low-flux electrodeposition method limited to electrode surface deposition is converted into an efficient and large-scale nanoparticle preparation method. The excellent colloid stability also endows the universal dispersed silver nano-particles with outstanding antibacterial activity. The rotatable surface ligand can be expanded to nanoparticles of other materials, and has wide application prospects in the fields of colloid chemistry, photoelectric devices, 3D printing, biomedicine and the like.

Drawings

FIG. 1 is a graph showing the preparation process and characterization results of the omnipotent dispersed silver nanoparticles of example 1; wherein, a, silver nanoparticles are continuously formed in a schematic view in an aqueous environment under 30V. b, absorption spectrum of silver nano colloid in water. Illustration is shown: the tyndall effect occurs when the laser passes through a colloidal solution. c, transmission electron microscopy of silver nanoparticles. d, average size statistical plots of silver nanoparticles synthesized at different electrodeposition voltages. e, under the deposition voltage of 30V, the relation graph of different concentrations of sodium dodecyl sulfate contained in the electrolyte solution and the efficiency of preparing the silver nano particles is shown. f, a large number of photographs of silver nanoparticles were retained on the ultrafiltration membrane.

Fig. 2 is a schematic view of the principle of silver nanoparticle formation, wherein a, silver nanoparticle formation is illustrated. The process I: during the nucleation process of the silver particles on the surface of the electrode, dodecyl sulfate ions are attached to the silverThe surface of the core. And (II) a process: the silver nanoparticles are attached with dodecyl sulfate and negatively charged. Process III: the silver nanoparticles are detached from the electrode surface into the electrolyte solution. b, force diagram of silver nanoparticles on the electrode surface. f. of₁、f₂、f₃Respectively representing the shearing force generated by the formation and release of the electrokinetic force and the hydrogen bubbles, the electrostatic repulsion between the nano particles and the electrodes, and the adhesion between the silver nano particles and the electrodes.

FIG. 3 shows the dispersion of silver nanoparticles in different solvents and their corresponding absorption spectra of the silver nanoparticles prepared by the wet chemical method (a) and (b) of the present invention.

Fig. 4 shows an infrared absorption spectrum (a) and a raman spectrum (b) of silver nanoparticles and sodium lauryl sulfate powder according to the present invention.

FIG. 5 shows 1298cm from the alkane chain when the silver nanoparticles of the invention are transferred from the aqueous phase to the oil phase (toluene)^-1With 961cm from sulfate^-1And (b) a graph illustrating the mechanism of changes in orientation of ligands by dodecyl sulfate ion ligand orientation and by surface enhanced raman scattering, wherein the statistical data are from ten different samples.

Fig. 6 is a schematic diagram showing the morphology of the silver nanoparticles of the present invention in an aqueous phase in which the hydrophilic sulfate head of the omnipotent dispersing nanoparticles is exposed and an oil phase in which the hydrophobic alkane chain extends into the oil.

Fig. 7 is a schematic diagram of a molecular dynamics simulation of silver nanoparticles of the present invention in aqueous and oil phases, wherein a, the distance of the carbon atom at the tail end of the dodecyl chain from the surface of silver is defined; b, in a water phase environment, under the two states of the initial state of an alkane chain being close to the surface of the silver nano particles and extending into oil, the evolution situation diagram of the d value along with time is shown; c, under the environment of an oil phase (toluene), the initial state of an alkane chain is a graph of the evolution of the d value with time under the conditions of 300K and 350K and close to the surface of the silver nano particles.

FIG. 8 is a graph comparing the diffusion of silver nanoparticles from water into toluene before and after one month of standing according to the present invention (a) and wet chemical process (b); wherein silver nanoparticles prepared by electrodeposition are partially diffused from the aqueous phase into the toluene phase, and silver nanoparticles prepared by wet chemistry are precipitated at the bottom and cannot enter the toluene phase.

Fig. 9 is a schematic diagram of an automated system for continuous electrodeposition of silver nanoparticles of the present invention. a, a schematic diagram of a system for automatically preparing silver nanoparticles, which consists of four parts. b, a real object picture. c, a first part, a structure diagram of an electrochemical cell for preparing silver nanoparticles. d, a second part, a water pump device structure diagram. And e, a structure diagram of a suction filtration device system. f, the filtered electrolyte is re-pumped back into the electrochemical cell for further electrodeposition.

Fig. 10 is a schematic structural diagram (a) of the smart pen, a result diagram (b) of arbitrarily writing a "ZJU" letter on a different substrate, and a repair breaking result diagram (c).

Fig. 11 is a comparison of silver nanoparticle colloidal solutions prepared by the present invention and wet chemistry methods with different concentrations of flagellin added.

FIG. 12 is a graph showing the bactericidal effect of the silver nanoparticles of the present invention; and a, in the sterilization process of the silver nanoparticles under the sub-bacteriostatic concentration, observing the silver nanoparticles prepared by electrodeposition in escherichia coli. b, the minimum inhibitory concentration and the minimum bactericidal concentration value of the silver nanoparticles prepared by electrodeposition and the silver nanoparticles prepared by wet chemistry against different bacteria. Wherein, I: staphylococcus aureus MY 0184. II: enterococcus faecium SAL 05040. III: enterococcus faecium SAL 05041. IV: streptococcus pneumoniae MY 0312. V: listeria L0019. VI: listeria L0020. VII: salmonella newborns MY 0180. VIII: salmonella typhimurium MY 0198. IX: salmonella enteritidis MY 0199. X: pseudomonas aeruginosa MY 0182. XI: escherichia coli MY 0183. XII: klebsiella sp SAL 05042. XIII: klebsiella SAL 05043. XIV: yersinia colitis MY 0125. XV: yersinia pseudotuberculosis MY 0126. The first six of these are gram-positive bacteria, the remainder are gram-negative bacteria. And c, comparing the antibacterial effect of the silver particles which are scraped from the surface of the electrode and are not loaded by dodecyl sulfate ions with the antibacterial effect of the silver nanoparticles which are prepared by electrodeposition and have universal dispersion characteristics.

Fig. 13 is a graph of the bactericidal kinetics of electrodeposited silver nanoparticles and wet chemical preparation of silver nanoparticles (a), where CFU/mL refers to colony forming units per mL. After the wood material is treated with silver nanoparticles dispersed in toluene (b) and water phase (c), scanning electron micrographs of the top and longitudinal sections of the wood (5 mm from the top surface) and a comparison graph (d) of the antibacterial performance of the wood after treatment with silver colloidal solutions dispersed in water phase and oil phase, without treatment, water rinsing and sanding are shown.

Detailed Description

Example 1 preparation of silver nanoparticles with Universal Dispersion characteristics

(1) A glass sheet with the diameter of 75mm and the thickness of 25mm is taken as a support, an aluminum foil paper is used for wrapping the glass sheet to form an aluminum foil sheet as a cathode, a carbon rod with the diameter of 5mm and the height of 75mm is taken as an anode, and the carbon rod and the aluminum foil are sequentially placed into ethanol and deionized water for ultrasonic cleaning for 10 min.

(2) 30mM silver nitrate and 90mM sodium lauryl sulfate were dissolved in 30ml of deionized water to obtain an electrolyte.

(3) In a two-electrode system, the aluminum foil electrode prepared in (1) was used as a working electrode, a carbon rod was used as a counter electrode, the distance between the working electrode and the counter electrode was maintained at 5cm, and electrodeposition was carried out at room temperature (25 ℃). In a two-electrode system, a constant voltage mode is selected, and a large amount of yellow fog tracks can be quickly obtained by deposition for 15s at 30V, as shown in figure 1a, the high efficiency of the method for preparing the nano particles is proved. And then carrying out further electrodeposition for 5min, taking out the liquid part after electrodeposition, standing for 10min, centrifuging the supernatant for 10min at 18000rpm, pouring the supernatant, adding 10ml of deionized water into the bottom precipitate part to obtain a silver colloid solution (with the concentration of 5mg/ml) dispersed in an aqueous environment, wherein the absorption spectrum of the silver colloid solution is shown in figure 1b, and the silver nanoparticles precipitated under the condition of 30V are approximately spherical and have the size of about 25nm and are shown in figure 1 c. Experiments prove that when the molar ratio of the silver ions to the anionic surface activity is less than or equal to 1, the electrodeposition voltage is 10V or more, and acid radical ions and a silver salt solution can form slightly soluble or insoluble salt, the acid radical ions can be anchored on the surface of the silver nanoparticles through chemical bonding by the method, and the size of the electrodeposited silver nanoparticles and the efficiency of silver nanoparticle generation can be controlled as required by regulating the deposition voltage or the concentration of a surfactant in the electrodeposition process as shown in fig. 1d and 1 e.

Fig. 2 is a schematic diagram illustrating the principle of silver nanoparticle formation, in an electrolyte solution, dodecyl sulfate ions strongly interact with silver ions, and when silver ions are reduced to a cathode surface to form small silver nanoparticles, dodecyl sulfate is fixed on the silver nanoparticles as shown in fig. 2a as I, and dodecyl sulfate also makes the silver nanoparticle surface negatively charged as shown in fig. 2a as II. FIG. 2b reflects the force experienced by the silver nanoparticles, wherein the shear force f₁Caused by bubbles generated on the surface of the electrodes, f₂Denotes electrostatic repulsion, f₃Referring to the adhesion force, the time for connecting the silver nanoparticles to the surface of the electrode is the growth time of the silver nanoparticles, and the final size of the silver nanoparticles is also the result of the mutual competition of the three forces. Shear force f when deposition voltage is increased₁Strengthening, resulting in the formation of smaller silver nanoparticles. When the surfactant concentration is increased, the electrostatic repulsion f is thereby enhanced₂. Therefore, the effect of regulating and controlling the silver nano-particle size and the forming efficiency according to the requirements by the electrodeposition parameters and conditions is realized.

Example 2 Structure and Dispersion characteristics of silver nanoparticles

The liquid fraction obtained in example 1 after 5min of electrodeposition at 30V was left to stand for 10min in 6 portions, and the supernatant was centrifuged at 18000rpm for 10min and then poured off. The bottom precipitate was sequentially added with 10ml OF ethylene glycol, toluene, N, N-dimethylformamide, acrylic acid, cyclohexane, AND plasma to obtain an environmentally dispersed silver colloid solution (5 mg/ml) as shown in FIG. 3a, whereas the silver nanoparticles prepared by the conventional wet chemistry method (Lee, P.C. & D. Meisel ADSORPTION AND SURFACE-ENHANCED RAMAN OF DYES ON SILVER AND GOLD SOLS. J. Phys. chem.86,3391-3395 (1982)) could not be dispersed in the above organic solution AND rapidly agglomerated AND precipitated as shown in FIG. 3 b.

961cm on silver nanoparticles prepared using infrared and Raman test spectroscopy^-1The results are shown in fig. 4a and b, and the existence of dodecyl sulfate on the surface of the silver nano-particles is proved. Further, 961cm was produced from silver dodecyl sulfate^-1Can be used as a reference because its intensity is not affected by changes in orientation of the dodecyl sulfate ion. FIG. 5a shows a cross-section of a cross-section derived from an alkane chain 1298cm^-1And 961cm from silver dodecyl sulfate^-1The ratio of the raman peak intensities of the two raman peak intensities is also reduced from 1 to 0.15, i.e. the raman peak intensity of the alkane chain is significantly reduced, indicating that the orientation of the dodecyl sulfate ion is indeed changed, since the electromagnetic field around the silver nanoparticles is sharply reduced far away from the surface of the nanoparticles as shown in fig. 5b, demonstrating the behavior of the alkane chain in self-adaptive rotation in different phases. Therefore, the silver nanoparticles prepared by the invention comprise silver particles and dodecyl sulfate ions, one end of each dodecyl sulfate ion is a hydrophilic sulfate head, the other end of each dodecyl sulfate ion is a hydrophobic alkane chain tail, and the dodecyl sulfate ions are fixed on the surfaces of the silver nanoparticles through non-directional ionic bonds and can sense the surrounding liquid medium environment and rotate to adapt. In an aqueous phase environment, hydrophobic alkane chains are attached to the surfaces of the nano particles, and hydrophilic sulfate head parts are exposed in water, so that the stability of the colloidal particles is maintained in a mode of electrostatic repulsion among the particles. In contrast, in the oil phase environment, the hydrophobic alkane chain tail extends into the oil, masking the hydrophilic sulfate ion, and forming stable colloidal solution with steric hindrance effect as shown in fig. 6.

Further, by means of molecular dynamics simulation, the self-adaptive behavior of alkane chain rotation in water phase and oil phase (represented by toluene reagent) environment is further proved from theory. Fig. 7a is a schematic diagram for monitoring the change of the perpendicular distance of the carbon atom at the end of dodecyl group from the silver surface under different solvents. In an aqueous environment, whether the initial state is the surface ligand far away from or close to the surface of the silver nanoparticles, the surface ligand will be close to the surface of the silver nanoparticles finally as shown in fig. 7 b. In an oil phase environment, as shown in fig. 7c, the surface ligand which is in an initial state and is close to the surface of the particles still adheres to the surface at 300K, but at 350K, the ligand is vibrated after 150ns and is changed into a state away from the surface and extends into the oil phase, and the repulsive force between the silver nanoparticles is increased by the dynamic vibration of the ligand, so that the stability of the colloidal particles is promoted. The temperature difference between the simulation result and the experimental result may be caused by a shorter simulation time or a more ideal system. The above fully demonstrates the adaptive spinning behavior of alkane chains on silver nanoparticles under different environments.

Example 3 dispersion stability of silver nanoparticles

After the liquid portion obtained in example 1 after 5min of electrodeposition at 30V was allowed to stand for 10min, the supernatant was centrifuged at 18000rpm for 10min, the supernatant was decanted, 5ml of deionized water was added to the precipitated portion to obtain a silver colloidal aqueous solution, 5ml of a toluene reagent (5 mg/ml in concentration) was added thereto, and the mixture was allowed to stand. A conventional wet chemical aqueous silver nanoparticle solution was similarly prepared, to which 5ml of toluene reagent was added, and left to stand as shown in fig. 8. After about one month, the silver nanoparticles prepared by electrodeposition can gradually diffuse into the oil phase as shown in fig. 8a, while the silver nanoparticles prepared by conventional wet chemistry can be agglomerated and precipitated and cannot diffuse into the oil phase as shown in fig. 8 b.

Example 4 continuous preparation of silver nanoparticles

(3) Then, a device for continuously preparing universal dispersed silver nano particles is built according to a schematic diagram designed as shown in FIG. 9. The electrolyte was poured into a 50ml size electrolytic cell as the first part of a continuous nanoparticle preparation apparatus as shown in fig. 9c for deposition of universal dispersed silver nanoparticles. One end of a water pump is connected with the electrolytic cell, the other end of the water pump is connected with a suction filtration device to serve as a second part as shown in figure 9d, the prepared aqueous phase silver micelle solution is transferred to the upper part of the suction filtration device, the third part mainly comprises a whole suction filtration system as shown in figure 9e, the suction filtration is mainly carried out on the formed silver colloid solution, nano particles are retained on the ultrafiltration membrane as shown in figure 1f, and the electrolyte is partially filtered. The fourth part consists of a return pipe, which is mainly used for returning the filtered electrolyte to the electrolytic cell for further electrodeposition as shown in fig. 9f, and so on. The whole apparatus for continuously preparing nanoparticles is shown in fig. 9b, and under the condition that the electrolyte is sufficiently supplemented, the production efficiency of silver nanoparticles can reach about 7g/h by using the apparatus for continuously preparing nanoparticles, and further, if a plurality of thick cathode carbon rods and more electrolyte are used, the production efficiency of silver nanoparticles of the automatic apparatus can be improved to the level of kg/h.

Application example 1 Intelligent pen

(1) 30mM silver nitrate and 90mM sodium lauryl sulfate were dissolved in 30ml of deionized water to obtain an electrolyte.

(2) And (3) taking a 10ml injection syringe as a pen body part of the intelligent pen, and adding the electrolyte obtained in the step (1) into the injection syringe. Two copper wires are taken, one end of the copper wire is inserted into the injection needle cylinder along the push rod part, and the exposed copper wire part is fully contacted with the electrolyte and is used as an anode. The other end of the copper wire is fixed on the shell part of the syringe, and the exposed copper wire part is fixed near the injection needle opening, so that the liquid drop extruded from the injection needle opening can just contact with the copper wire, and the copper wire is used as a cathode as shown in figure 10 a. The copper wire is connected with a voltage, a voltage of 30V is applied, and when the power is on, the push rod of the injection syringe is pressed by fingers, so that the electrolyte drops hung on the needle point are connected with each other. The universal dispersed silver nano particles are generated in electrolyte liquid drops as shown in figure 10a, and the universal dispersed silver nano particles can be printed on the surfaces of any materials such as glass, plastics, ceramics, metal nets, silicon wafers and the like by slowly moving and pushing an injector as shown in figure 10 b. The broken circuit can also be easily repaired by the smart pen as shown in fig. 10 c.

Application example 2 Sterilization

The liquid fraction obtained in example 1 after electrodeposition at 30V for 5min was allowed to stand for 10min, the supernatant was centrifuged at 18000rpm for 10min, the supernatant was decanted, and 6ml of deionized water was added to the precipitated fraction to obtain a silver colloidal aqueous solution (concentration: 5mg/ml) which was divided into 6 portions each of 1 ml. Similarly, 6 parts of 1ml of an equal concentration silver colloid aqueous solution was prepared by a conventional wet chemical method, and flagellin was sequentially added to the silver colloid aqueous solutions prepared by the two preparation methods to give final concentrations of 0.05 ng/. mu.l, 0.10 ng/. mu.l, 0.37 ng/. mu.l, 0.73 ng/. mu.l, 1.67 ng/. mu.l, and 2.50 ng/. mu.l, respectively, and the stable state of the silver colloid solution after 7 days was as shown in FIG. 11. Previous studies have shown that bacteria can produce resistance to silver nanoparticles by producing flagellin or other species to initiate aggregation of the silver nanoparticles, reducing or even eliminating their antibacterial activity. The silver nanoparticles prepared by electrochemical deposition can resist flagellin with the concentration as high as 2.50 ng/microliter, and compared with the silver nanoparticles prepared by wet chemistry, the silver nanoparticles are easy to agglomerate when meeting flagellin.

Since the surfactant ligand on the surface of the silver nanoparticles prepared by electrodeposition is very similar to the structure of the bacterial membrane, it is easy to help the silver nanoparticles to enter the interior of the bacteria as shown in fig. 12 a. Further, silver nanoparticles prepared by electrodeposition showed better antibacterial ability than those prepared by conventional wet chemistry as shown in fig. 12 b. For fifteen kinds of bacteria tested, including staphylococcus aureus, enterococcus faecium, streptococcus pneumoniae, listeria, salmonella newbauer, salmonella typhimurium, salmonella enteritidis, pseudomonas aeruginosa, escherichia coli, klebsiella, yersinia colitis, yersinia pseudotuberculosis, and the like, the Minimum Bactericidal Concentration (MBC) and the Minimum Inhibitory Concentration (MIC) of the electrodeposited silver nanoparticles are both lower than those of the silver nanoparticles prepared by traditional wet chemistry by more than 10 times, and fig. 13a also reveals that the bactericidal efficiency of the electrodeposited silver nanoparticles is greatly improved. Fig. 12c is a comparison graph of the antibacterial effect of silver particles without dodecyl sulfate ion loading (electrolyte without surfactant) scraped from the electrode surface and silver nanoparticles with universal dispersion characteristics prepared by electrodeposition, further reflecting that dodecyl sulfate ligand significantly enhances the antibacterial activity of silver nanoparticles. Statistics show that the silver nanoparticles prepared by electrodeposition have higher bactericidal capacity on gram-negative bacteria (bacterial membrane films), while the silver nanoparticles prepared by wet chemistry have similar bactericidal effects on gram-positive bacteria (bacterial membrane thicknesses) and gram-negative bacteria, which further indicates that the excellent antibacterial activity of the universal dispersed silver nanoparticles is derived from the enhanced colloidal stability and the surface ligand camouflage thereof and assists the silver nanoparticles to enter the bacteria.

Further, in order to exert excellent antibacterial ability of the electrodeposited silver nanoparticles in combination with daily life needs, in order to wet the surface and feed the silver nanoparticles into small cracks and pores, it is a preferred choice to disperse the silver nanoparticles having universal dispersion characteristics in the oil phase agent. Often, to obtain colloidal particles dispersed in an oil phase, the nanoparticles are chemically modified, often in combination with valuable, environmentally hazardous chemical agents. The silver nanoparticles with universal dispersion characteristics prepared by a green electrochemical deposition mode can be naturally dispersed in an oil phase environment, the silver nanoparticles are dispersed in toluene (with the concentration of 5mg/ml) and coated on the surface of wood, a toluene solvent instantly infiltrates the surface of the wood and conveys the silver nanoparticles to the surface of the wood and various cracks, and fig. 13b and c show microscopic photographs of the section of the wood after the wood is treated by using an oil-phase silver colloid solution and a water-phase silver colloid solution, thereby verifying that the silver colloid solution with toluene as a carrier well conveys the silver nanoparticles to various parts of pore cracks of the wood. The wood treated with the oil phase silver colloid solution exhibited higher antibacterial activity by rinsing with ultrapure water or sanding as shown in fig. 13 d.

It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. This need not be, nor should all embodiments be exhaustive. And obvious variations or modifications of the invention may be made without departing from the scope of the invention.

Claims

1. Silver nanoparticles with universal dispersion characteristics are characterized in that anion groups are chemically bonded to the surface of the silver nanoparticles, and the anion groups have the structural formula: (C)_nH_2n+1—R)^—In which C is_nH_2n+1Is alkane chain, n is more than or equal to 10, R is acid radical ion, and the acid radical ion and silver salt solution are mixed to form slightly soluble or insoluble salt.

2. The silver nanoparticles according to claim 1, wherein the dispersion medium of the silver nanoparticles is an oil phase, an aqueous phase or a biological liquid.

3. A method for preparing silver nanoparticles with universal dispersion characteristics according to any one of claims 1-2, comprising:

the aqueous solution containing silver ions and an anionic surfactant is used as electrolyte for electrodeposition, and silver nanoparticles with universal dispersion characteristics are directly generated on the surface of a cathode and sprayed into a liquid phase environment for uniform dispersion. Wherein the molar ratio of the silver ions to the anionic surface activity is less than or equal to 1, and the acid radical ions in the anionic surfactant and the silver salt solution are mixed to form slightly soluble or difficultly soluble salt. The electrodeposition voltage is 10V or more.

4. The method according to claim 3, wherein any conductive material is used as a cathode and a carbon rod is used as an anode.

5. The production method according to claim 3, wherein the larger the electrodeposition voltage is, the smaller the silver nanoparticle size is.

6. The method according to claim 3, wherein the molar ratio of the silver ion to the anionic surface activity is 1:1 to 10. The electrodeposition voltage is 10V-100V.

7. The method for preparing the anionic surfactant according to claim 3, wherein the anionic surfactant is one or more of sodium decyl sulfate, sodium dodecyl sulfate, sodium hexadecyl sulfate and the like, and the anionic surfactant is mixed and composed according to any proportion. The silver salt solution is formed by mixing one or more of silver nitrate solution, silver acetate solution and the like according to any proportion.

8. The method according to claim 7, wherein the metal salt solution is a silver nitrate solution, the anionic surfactant is sodium lauryl sulfate, and the electrodeposition voltage is 30V.

9. Use of the silver nanoparticles according to any one of claims 1-2 in sterilization, optoelectronic device fabrication, 3D printing, colloidal chemistry.

10. The intelligent pen is characterized by comprising a pen holder, a pen point, a cathode and an anode, wherein an aqueous solution containing silver ions and an anionic surfactant is filled in the pen holder, and the aqueous solution can be controllably output to the pen point. The anode is arranged in the aqueous solution, the cathode is positioned near the pen point, and the cathode is contacted with the aqueous solution when the aqueous solution is controllably output to the pen point to form liquid drops. Wherein the molar ratio of the silver ions to the anionic surface activity is more than or equal to 1, and the acid radical ions in the anionic surfactant and the silver salt solution are mixed to form slightly soluble or difficultly soluble salt. When the intelligent pen works, the voltage between the cathode and the anode is 10V or more.