Preparation method of Ag / AgBr nanoparticles with monodisperse double-sided structure
Ag/AgBr nanoparticles with double-sided god structures were prepared by one-pot method, which solved the problems of high preparation cost and complexity in the prior art, and achieved nanoparticles with uniform particle size and good dispersion, and were used in the fields of surface enhancement Raman detection and antibacterial.
Patent Information
- Application Number
- CN202510340989.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-21
- Publication Date
- 2025-06-10
AI Technical Summary
The prior art is difficult to prepare Ag/AgBr nanoparticles with good monodispersity and good monosided structures on a large scale through a simple and easy-to-use one-pot method, and the traditional methods are costly or require expensive reagents and equipment.
Using the one-pot method, cetyl trimethyl ammonium bromide (CTAB) and gallic acid were used to form an emulsion at room temperature, silver nitrate was added for reduction reaction, and left to stand in a constant temperature water bath. Ag/AgBr nanoparticles with double-sided structure were prepared through primary reduction and secondary reaction.
The prepared Ag/AgBr nanoparticles have uniform particle size and good dispersion, and have surface-enhanced Raman effect and broad-spectrum antibacterial properties. They are suitable for surface-enhanced Raman detection and antibacterial fields.
Smart Images
Figure CN120115684A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of nanocomposites and their applications, and particularly relates to a method for preparing monodisperse Janus-structured Ag / AgBr nanoparticles. Background Art
[0002] The concept of "Janus" comes from the Roman god "Janus", who has two different faces looking forward and backward respectively. "Janus" nanoparticles refer to a special type of nanoparticles composed of two or more components with different properties and having two different surfaces, that is, particles with two or more surface regions in a single particle, showing different properties and arranged asymmetrically. In 1985, Professor Lee and his colleagues first synthesized Janus particles by using the seed emulsion method to polymerize an asymmetric polystyrene / polymethyl methacrylate (PS / PMMA) lattice under specific conditions (Reference: J. Appl. Polym. Sci. 1985, 1903 - 1926). In 1988, Casagrande and Veyssi prepared "Janus beads" with one hydrophilic side and the other hydrophobic side through selective surface modification (Reference: Europhys. Lett. 1989, 251 - 255). However, it was not until 1991 that the concept of "Janus" was first proposed by Professor Pierre-Gilles de Gennes at his Nobel Prize awarding ceremony. Janus particles contain at least two different compounds, functions or polarities, and their chemical asymmetry endows Janus particles with two or more different properties. This anisotropy and the diversity of particle morphology and composition enable a single Janus particle to integrate multiple physical and chemical properties, thus showing different properties in the same particle. Even many units with incompatible functions / characteristics can be assembled in spatially separated regions of a single Janus nanoparticle without interfering with each other, such as polar and non-polar, hydrophilic and hydrophobic, magnetic and fluorescent, anionic and cationic, which are functions that traditional uniform nanoparticles cannot achieve. Therefore, Janus particles have special application values in various fields such as electronics, biology, optics, catalysis, etc., showing good application prospects.
[0003] In the past few decades, the exploration of the preparation strategies and unique properties of Janus nanoparticles has been active. A variety of synthetic strategies have been developed for the preparation of Janus nanoparticles. These methods include sputtering, microfluidic synthesis, Pickering emulsion, self-assembly, phase separation, etc. Generally speaking, the synthesis methods of Janus nanoparticles can be divided into three categories: masking, phase separation, and self-assembly. The basic principle of the masking method is to mask one side of a uniform particle with a masking agent, modify the unshielded side by physical or chemical methods, and then remove the masking coating on the other side to form anisotropic Janus nanoparticles. The advantage of the masking method is its flexibility and directness in synthesis. However, in each step, it is necessary to protect the active groups in multifunctional compounds and then deprotect them, resulting in low yields and large workloads (References: Adv. Mater. 2019, 1807507; Adv. Mater. 2021, 2100288). The phase separation method utilizes the difference in compatibility between substances. By mixing two substances with poor compatibility but that can be co-dissolved in the same highly volatile solvent, after co-dissolving in the solvent, phase separation is induced by changing the temperature to evaporate the solvent to generate different regions, forming Janus nanoparticles (References: Langmuir 2022, 6882 - 6895;. Am. Chem. Soc. 2025, https: / / doi.org / 10.1021 / jacs.4c18003). Both microfluidics and seed-mediated polymerization belong to the phase separation method. The former requires special equipment, which is expensive, prone to clogging, complex to maintain, unable to precisely control particle sizes below the micron scale, and is also limited by material selection and the equipment pressure range. The latter requires the pre-preparation of suitable seeds and cannot be completed in one step. The self-assembly method is a technique that enables basic structural units to spontaneously form an ordered structure in solution or at the interface. It is a simple and effective method for constructing materials with fine structures. However, this method requires the pre-preparation of nanoparticles and the use of relatively expensive block copolymers and volatile solvents with certain toxicity (such as chloroform), and thus cannot be completed in one step in a one-pot preparation system (References: Adv. Mater. 2024, 2309966; Nanoscale 2024, 17549 - 17558). In summary, although certain achievements have been made in traditional methods for preparing Janus nanoparticles, they are generally technically complex, have low yields, and cannot be used for large-scale production. Designing a reasonable preparation system to synthesize nanoparticles with a Janus structure through a simple and scalable one-pot route remains a very challenging task, which can also bring more inspiration to the synthesis and application of nanomaterials while providing multifunctional nanomaterials.
[0004] Ag / AgBr heterostructure nanomaterials are widely used in the field of photocatalysis, but the combination of the two in existing reports is either a core-shell structure or a particle hybrid multi-interface structure. The Ag / AgBr heterojunction with a Janus structure is very rare, and reports of preparation using a one-pot route are even rarer. The only work that can be found is that Gurbir Singh et al. used nicotine-based surfactant ionic liquids as surface capping agents and bromine sources to prepare Ag / AgBr Janus nanoparticles by photoreduction and applied them to photocatalytic degradation of organic dyes (reference: J. Mater. Chem. A, 2019, 5185-5189). However, the ionic liquid used was homemade by the research group, with limited production and high cost. Another similar work is the AuAg alloy @AgBr Janus nanoparticles prepared by Kanica Sharma et al. They used hexadecyltrimethylammonium bromide (CTAB) as a template to first generate a white precipitate, which is AgBr nanoparticles, and then added AuCl 4 − or Au(OH) 4 − Brown AuAg alloy@AgBr Janus nanoparticles were prepared under the synergistic effect of ascorbic acid and light irradiation, and the product was used as a photocatalyst and antibacterial agent (reference: Nanoscale, 2024, 17549-17558). However, this work requires the participation of expensive gold salts, and chemical reduction and photoreduction must act simultaneously to achieve the formation of the Janus structure.
[0005] In summary, developing a simpler and more feasible one-pot route to prepare Ag / AgBr heterojunction nanoparticles with good monodispersity and multifunctional Janus structure at the nanoscale is a challenging new task. Summary of the invention
[0006] The present invention provides a method for preparing monodisperse Janus-structured Ag / AgBr nanoparticles. The method is completed by a one-pot route, is simple and easy to operate, and does not require special reagents. The Janus Ag / AgBr nanoparticles prepared by the method have the characteristics of good dispersibility, uniform particle size, and being in the nanoscale range, and can be used in the fields of surface enhanced Raman trace detection and antibacterial.
[0007] The technical solution of the present invention is: a method for preparing monodisperse Janus-structured Ag / AgBr nanoparticles, characterized by the following steps: (1)At room temperature, 0.006 g - 0.012 g of cetyltrimethylammonium bromide (CTAB) was added to 9 - 12 mL of deionized water to form a translucent emulsion A by stirring; then 0.01 - 0.04 g of gallic acid was weighed and added to 9 - 12 mL of deionized water, and its complete dissolution was promoted by stirring to form a transparent solution B.
[0008] (2)0.04 - 0.1 g of silver nitrate (AgNO 3 ) was added to solution A in step (1), and the translucent emulsion became a clear and transparent solution C, and no milky white AgBr precipitate was formed.
[0009] (3)The gallic acid solution B prepared in step (1) was poured into solution C obtained in step (2) for the first reduction. The mixed solution sequentially showed pink, pink - purple, and dark blue colors in a short time and gradually became an opaque blue - black suspension. The obtained product was a worm - like one - dimensional Ag nanostructure after the reduction of silver ions by gallic acid (see attached Figure 3 —0 min picture).
[0010] (4)The suspension obtained in step (3) was transferred to a constant temperature water bath at 40 - 80 °C and allowed to stand and react for 2 - 20 h. The color of the suspension gradually changed and finally became a khaki suspension; during this process, the one - dimensional Ag nanoworms gradually became shorter, and at the same time, new flaky nanostructures appeared at their edges, indicating that a secondary reaction occurred (between Ag and Br ions in the solution). As the reaction time passed, the worm - like structure disappeared and was completely transformed into Janus nanoparticle structures (the entire secondary reaction process is shown in the attachment Figure 3 ). Steps (3) and (4) together reflect the preparation principle of combining the first reduction and the secondary reaction.
[0011] (5)The suspension obtained in step (4) was centrifuged, and the obtained solid was washed 1 - 3 times with deionized water to obtain Ag / AgBr nanoparticles with Janus structures; in the same near - spherical nanoparticle, one side was hemispherical Ag nanoparticles and the other side was hemispherical AgBr nanoparticles (see attached Figure 1 ).
[0012] The centrifugation speed was: 5000 - 8000 rpm, and the time was 8 - 10 min.
[0013] The advantages of the present invention are: (1)The present invention adopts a one - pot preparation route, with simple steps, no need for special reagents and equipment, and low cost.
[0014] (2)The Janus - structured Ag / AgBr nanoparticles obtained by the present invention have uniform particle sizes (about 100 nm), good dispersibility, and no aggregation phenomenon (see attachedFigure 1 ).
[0015] (3) Due to the special structure of Janus, it combines the characteristics and functions of noble metal Ag and semiconductor AgBr. When this material is used as a surface-enhanced Raman (SERS) substrate, it exhibits a good Raman enhancement effect, and the detection limit can reach 1×10 -10 mol / L when p-mercaptobenzoic acid is used as the probe molecule, and it exhibits good broad-spectrum antibacterial performance when used as an antibacterial agent.
[0016] The present invention will be further described below in conjunction with specific embodiments. The embodiments are only used to illustrate the present invention and not to limit the protection scope of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS
[0017] Figure 1 Transmission electron microscope image of monodisperse Janus-structured Ag / AgBr nanoparticles prepared according to the present invention (reacted at 60 °C for 6 h).
[0018] Figure 2 X-ray powder diffraction pattern of monodisperse Janus-structured Ag / AgBr nanoparticles prepared according to the present invention (reacted at 60 °C for 6 h).
[0019] Figure 3 Transmission electron microscope images of products at different reaction times during the secondary reaction in the preparation process of the present invention (i.e., after the blue-black suspension enters the constant temperature water bath) (under the condition of 60 °C constant temperature).
[0020] Figure 4 Ultraviolet-visible absorption spectra of products at different reaction times during the secondary reaction in the preparation process of the present invention (i.e., after the blue-black suspension enters the constant temperature water bath) (under the condition of 60 °C constant temperature).
[0021] Figure 5 Raman spectra of monodisperse Janus-structured Ag / AgBr nanoparticles prepared in Example 1 of the present invention as a surface-enhanced Raman substrate for detecting p-mercaptobenzoic acid probe molecules at different concentrations.
[0022] Figure 6 Antibacterial effect diagrams of monodisperse Janus-structured Ag / AgBr nanoparticles prepared in Example 2 of the present invention against Gram-negative bacterium Escherichia coli ( E. Coli ) and Gram-positive bacterium Staphylococcus aureus ( S. aures ). The left pictures are the experimental effect diagrams with deionized water as the control respectively. DETAILED DESCRIPTION OF THE INVENTION EXAMPLE
[0023] A preparation method of monodisperse Janus-structured Ag / AgBr nanoparticles, the steps are as follows: (1)At room temperature, 0.012 g of CTAB was added to 10 mL of deionized water and stirred to form a translucent emulsion A; then 0.02 g of gallic acid was weighed and added to 10 mL of deionized water, and stirred to promote its complete dissolution to form a transparent solution B.
[0024] (2)0.08 g of silver nitrate (AgNO 3 ) was added to the solution A in step (1), and the translucent emulsion became a clear and transparent solution C.
[0025] (3)The gallic acid solution B prepared in step (1) was poured into the solution C obtained in step (2) to obtain a dark blue opaque suspension.
[0026] (4)The suspension obtained in step (3) was transferred to an 80 °C constant temperature water bath and allowed to stand and react for 2 h. After the reaction, a khaki suspension was obtained.
[0027] (5)The suspension obtained in step (4) was centrifuged (5000 rpm, 10 min), and the obtained solid was washed with deionized water 1 - 3 times to obtain Janus - structured Ag / AgBr nanoparticles. Example
[0028] A method for preparing monodisperse Janus - structured Ag / AgBr nanoparticles, the steps are as follows: (1)At room temperature, 0.012 g of CTAB was added to 10 mL of deionized water and stirred to form a translucent emulsion A; then 0.01 g of gallic acid was weighed and added to 10 mL of deionized water, and stirred to promote its complete dissolution to form a transparent solution B.
[0029] (2)0.04 g of silver nitrate (AgNO 3 ) was added to the solution A in step (1), and the translucent emulsion became a clear and transparent solution C.
[0030] (3)The gallic acid solution B prepared in step (1) was poured into the solution C obtained in step (2) to obtain a dark blue opaque suspension.
[0031] (4)The suspension obtained in step (3) was transferred to an 80 °C constant temperature water bath and allowed to stand and react for 4 h. After the reaction, a khaki suspension was obtained.
[0032] (5)The suspension obtained in step (4) was centrifuged (5000 rpm, 10 min), and the obtained solid was washed with deionized water 1 - 3 times to obtain Janus - structured Ag / AgBr nanoparticles. Example
[0033] A preparation method of monodisperse Janus - structured Ag / AgBr nanoparticles is as follows: (1) At room temperature, 0.012 g of CTAB is added to 10 mL of deionized water to form a translucent emulsion A by stirring; then, 0.02 g of gallic acid is weighed and added to 10 mL of deionized water, and its complete dissolution is promoted by stirring to form a transparent solution B.
[0034] (2) 0.08 g of silver nitrate (AgNO 3 ) is added to the solution A in step (1), and the translucent emulsion becomes a clear and transparent solution C.
[0035] (3) The gallic acid solution B prepared in step (1) is poured into the solution C obtained in step (2) to obtain a dark blue opaque suspension.
[0036] (4) The suspension obtained in step (3) is transferred to a 60 °C constant temperature water bath and left to stand for reaction for 6 h. After the reaction ends, a khaki suspension is obtained.
[0037] (5) The suspension obtained in step (4) is centrifuged (5000 rpm, 10 min), and the obtained solid is washed 1 - 3 times with deionized water to obtain Janus - structured Ag / AgBr nanoparticles.
[0038] It is as follows: (1) Less than 1 mL of deionized water is added to a test tube containing Janus Ag / AgBr nanoparticles. After sufficient ultrasonic dispersion, a drop of the suspension is sucked with a Pasteur pipette and dropped on a glass slide, and then it is left to dry naturally or dried in an 80 °C oven to promote its drying process, forming a film of Janus Ag / AgBr nanoparticles. Multiple glass slide samples can be made simultaneously in this step.
[0039] (2) Ethanol solutions of p - mercaptobenzoic acid with different concentrations (1×10 -3 ~ 1×10 -10 mol / L) are prepared.
[0040] (3) Ethanol solutions of p - mercaptobenzoic acid with different concentrations prepared in step (2) are respectively sucked and dropped onto the film of Janus Ag / AgBr nanoparticles prepared in step (1), and then left to dry naturally or dried in an 80 °C oven to promote its drying process.
[0041] (4) The samples prepared in step (3) are used to obtain Raman spectra on a Thermo Scientifi DXR Raman spectrometer and all data are compared and analyzed (Table 1). It can be found that even when the concentration is as low as 1×10 -10 mol / L, the Raman characteristic peaks of p - mercaptobenzoic acid are still clearly distinguishable in the spectrum (see attachment Figure 5, (Raman enhancement spectra of solutions of p-mercaptobenzoic acid with different concentrations were detected for the product obtained in Example 1), indicating that the Janus Ag / AgBr nanoparticles prepared have good surface Raman enhancement effect.
[0042] Table 1 Statistics of the detection limits (lowest detection concentrations) for detecting p-mercaptobenzoic acid when the products obtained in Examples 1 to 3 are used as surface Raman enhancement substrates
[0043] The steps are as follows: (1) Prepare a culture medium with agar, beef extract, peptone, and NaCl and perform high-temperature sterilization.
[0044] (2) Uniformly coat the culture medium surface with the strains of Escherichia coli or Staphylococcus aureus.
[0045] (3) Place a sterilized filter paper with a diameter of 1 cm on the culture medium in step (2).
[0046] (4) Drop a drop of moderately diluted Janus Ag / AgBr nanoparticle suspension onto the filter paper, and at the same time, drop an equal amount of deionized water onto the surface of the control filter paper.
[0047] (5) Place the culture medium prepared in step (4) in an incubator at 37 °C for 24 - 48 h, and it can be found that an obvious antibacterial zone is generated around the filter paper dropped with Janus Ag / AgBr nanoparticles (attached Figure 6 ), while there is no antibacterial zone around the control filter paper, indicating that the Janus Ag / AgBr nanoparticles prepared by the present invention have good antibacterial properties.
[0048] Table 1 Statistics of the antibacterial effects (antibacterial zone sizes) when the products obtained in Examples 1 to 3 are used as antibacterial agents.
[0049]
[0050] Figure 1 This is a transmission electron microscope image of the monodisperse Janus-structured Ag / AgBr nanoparticles prepared by the present invention (reacted at 60 °C for 6 h). It can be seen from the figure that each nanoparticle presents two different faces, that is, the Janus structure, and the size is about 100 nm, indicating uniform particle size and no aggregation phenomenon, indicating good dispersibility.
[0051] Figure 2X-ray powder diffraction pattern of monodisperse Janus-structured Ag / AgBr nanoparticles prepared by the present invention (reacted at 60 °C for 6 h). As can be seen from the figure, the X-ray powder diffraction pattern of the obtained product shows both the characteristic peaks of Ag and the characteristic peaks of AgBr, indicating that the product is a complex of Ag and AgBr.
[0052] Figure 3 Transmission electron microscope images of products at different reaction times during the secondary reaction in the preparation process of the present invention (i.e., after the blue-black suspension enters the thermostatic water bath) (under the condition of constant temperature at 60 °C). It can be seen that the initial (0 min) blue-black suspension shows a one-dimensional worm-like nanostructure. As time goes by, light-colored flake nanostructures gradually appear at the edges of the worm structure. Then, the length of the worm structure gradually shortens and finally forms Figure 1 the Janus structure. This shows that after gallic acid is added to solution C, silver nitrate is first reduced to form a worm-like nanostructure and a blue-black precipitate (primary reduction). During the subsequent constant temperature treatment stage, Br ions in the solution react with the worm-like Ag again, gradually generating Janus-structured Ag / AgBr nanoparticles.
[0053] Figure 4 Ultraviolet-visible absorption spectra of products at different reaction times during the secondary reaction in the preparation process of the present invention (i.e., after the blue-black suspension enters the thermostatic water bath) (under the condition of constant temperature at 60 °C). It can be seen that as the reaction proceeds, the absorption peak gradually redshifts from the initial about 380 nm, indicating that the morphology and particle size of the product are changing, which is consistent with Figure 3 the results.
[0054] Figure 5 Raman spectra of monodisperse Janus-structured Ag / AgBr nanoparticles prepared in Example 1 of the present invention as a surface-enhanced Raman substrate for detecting p-mercaptobenzoic acid probe molecules at different concentrations. It can be seen that even when the concentration is as low as 1×10 -10 mol / L, the characteristic peaks of p-mercaptobenzoic acid at 1078 cm -1 and 1581 cm -1 are still clearly visible, indicating that the prepared Janus-structured Ag / AgBr nanoparticles have good surface Raman enhancement effect.
[0055] Figure 6 Images of monodisperse Janus-structured Ag / AgBr nanoparticles prepared in Example 2 of the present invention against Gram-negative bacterium Escherichia coli ( E. Coli ) and Gram-positive bacterium Staphylococcus aureus ( S. auresThe antibacterial effect diagrams in ( ) are shown. The left pictures are the experimental effect diagrams with deionized water as the control. It can be seen that there are obvious antibacterial zones around the filter papers loaded with Janus structure Ag / AgBr nanoparticles, and the antibacterial zones are relatively large, indicating that the prepared product has good antibacterial effects.
[0056] The above description is only the specific implementation manner of the present invention, and various examples do not constitute a limitation to the essence of the present invention.
Claims
1. A method for preparing monodisperse Janus-structured Ag / AgBr nanoparticles, characterized in that The steps are as follows: (1) At room temperature, add 0.006 g to 0.012 g of hexadecyltrimethylammonium bromide to 9 to 12 mL of deionized water and stir to form a translucent emulsion A. Then weigh 0.01 to 0.04 g of gallic acid and add it to 9 to 12 mL of deionized water and stir to promote its complete dissolution to form a transparent solution B. (2) Weigh 0.04-0.1 g of silver nitrate and add it to solution A in step (1). The translucent emulsion becomes a clear transparent solution C, and no milky white AgBr precipitate is generated. (3) pouring the gallic acid solution B prepared in step (1) into the solution C obtained in step (2) for a primary reduction, and the resulting product is a worm-like one-dimensional Ag nanostructure after silver ions are reduced by gallic acid; (4) The suspension obtained in step (3) is placed in a constant temperature water bath at 40 to 80 °C and allowed to react for 2 to 20 h. The color of the suspension gradually changes and eventually becomes a khaki suspension. (5) The suspension obtained in step (4) is centrifuged and the obtained solid is washed with deionized water for 1 to 3 times to obtain Ag / AgBr nanoparticles with a Janus structure; in the same nearly spherical nanoparticle, one side is a hemispherical Ag nanoparticle and the other side is a hemispherical AgBr nanoparticle.
2. Ag / AgBr nanoparticles with a Janus structure prepared according to the method of claim 1.