Silica-based janus particles, methods of making and using the same

Abstract

The application discloses a kind of silica-based Janus particles and its preparation method and application, its preparation method includes the following steps: the molar ratio of 1:0.007~0.014 of silicate and alkoxysilane is dissolved in solvent, after stirring, a certain amount of weak alkaline solution is added, after 20~30 ℃ reaction 6~12 h, after centrifugation, dry and obtain silica-based Janus particles.The method needs lower temperature for reaction, mild condition, reaction step is less, and the Janus particles prepared are uniform spherical shape, the surface of the ball has obvious different morphology, one side is smooth and the other side is rough, the smooth surface has hydrophilicity and the rough surface has lipophilicity, which can be applied to stable emulsion, catalyst loading, drug controlled release and other fields.

Description

Technical Field

[0001] This invention relates to the field of inorganic functional nanoparticle technology, and more specifically, to a silica-based Janus particle, its preparation method, and its application. Background Technology

[0002] Janus particles are amphiphilic, asymmetrical solid particles, meaning one side of the particle is hydrophilic and the other side is hydrophobic. These solid particles, which have localized oleophilicity and localized hydrophilicity, are similar to surfactants and can be adsorbed at the interface between the aqueous and oil phases. They are mainly used as stabilizers, thickeners, and catalysts in Pickering emulsions.

[0003] The advantages of Janus particles are: (1) The concentration of colloidal particles required for emulsion is much lower than that of surfactant, which can reduce the amount of emulsifier used and save costs; (2) The toxicity of colloidal particles to the human body and the environment is much less than that of surfactants; (3) The emulsion system with stable Janus particles is not easily affected by external acidity, alkalinity, salt concentration, temperature and oil phase composition, and has stronger stability; (4) Janus particles can be easily modified to have acid-base, temperature or magnetic responsiveness, and the separation and recovery of particles can be achieved by changing the stimulation conditions.

[0004] Currently, the main methods for preparing Janus particles based on inorganic compound particles include topologically selected surface modification, microfluidic technology, and controlled nucleation growth. Among these, topologically selected surface modification is cumbersome to operate, microfluidic technology has high equipment requirements and produces ions of uniform size, while controlled nucleation growth is simple to operate and allows for adjustable ion size.

[0005] Chinese patent CN201210347232.5 discloses a method for preparing modified nano-silica, which is a selective surface modification method. It employs a sol-gel method with acid-base co-catalysis to prepare nano-silica, and uses a silane coupling agent to modify the nano-silica in situ, changing its hydrophilicity to oleophilicity. However, this method is cumbersome, requires high reaction temperatures, and the resulting particles do not possess the regional amphiphilicity characteristic of Janus particles. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the defects and shortcomings of the existing preparation of silica-based Janus particles, which have high reaction temperatures and complicated reaction steps. The present invention provides a method for preparing silica-based Janus particles, which achieves regional modification of silica particles by controlling the amount of precursor and modifier, with lower reaction temperature, milder conditions and fewer preparation steps.

[0007] Another object of the present invention is to provide a silicon dioxide-based Janus particle.

[0008] Another object of the present invention is to provide the application of silica-based Janus particles in the preparation of emulsions.

[0009] The above-mentioned objective of this invention is achieved through the following technical solution:

[0010] A method for preparing silica-based Janus particles includes the following steps:

[0011] A silicate ester and an alkoxysilane with a molar ratio of 1:0.007 to 0.014 are dissolved in a solvent, stirred, and then a weak alkaline solution with a volume of 1 to 3 times that of the silicate ester is added. The mixture is reacted at 20 to 30°C for 6 to 12 hours, and then centrifuged and dried to obtain silica-based Janus particles.

[0012] This invention provides a method for preparing silica-based Janus particles. The method involves adding a weakly alkaline solution to a mixed solution of silicate ester and modifier to provide the most suitable reaction environment by adjusting the ratio of silicate ester to modifier. After the reaction, silica-based Janus particles can be generated. The preparation method of this invention does not require high temperature conditions and has fewer steps.

[0013] Preferably, the molar ratio of the silicate ester to the alkoxysilane is 1:0.01.

[0014] Preferably, the silicate ester is one of tetraethyl silicate, tetramethoxysilane, propyl orthosilicate, or isopropyl orthosilicate, as a precursor for the reaction.

[0015] More preferably, the silicate ester is tetraethyl silicate.

[0016] Preferably, the alkoxysilane is one of hexadecyltrimethoxysilane, octadecyltrimethoxysilane, octadecyltriethoxysilane, and n-octyltrimethoxysilane, used as a modifier for the reaction.

[0017] More preferably, the alkoxysilane is hexadecyltrimethoxysilane.

[0018] Preferably, the solvent is one of isopropanol, methanol, ethanol, n-propanol, ethylene glycol, and tert-butanol.

[0019] More preferably, the solvent is isopropanol, which is cheaper, more environmentally friendly, and has the best water and oil solubility.

[0020] Preferably, the weakly alkaline solution is an ammonia solution with a mass fraction of 25% to 30%.

[0021] Preferably, the reaction temperature is 20–30°C and the reaction time is 6–12 h.

[0022] More preferably, the reaction temperature is 30°C and the reaction time is 6 hours.

[0023] Preferably, after centrifugation, the particles are washed three times with ethanol and distilled water respectively, and then dried to obtain silicon dioxide-based Janus particles.

[0024] More preferably, after the reaction is complete, the system presents a white emulsion. After centrifugation, the supernatant is discarded, and the solid residue is washed three times with ethanol and distilled water respectively. After washing, it is dried to constant weight to obtain silicon dioxide-based Janus particles.

[0025] This invention also protects the silicon dioxide-based Janus particles prepared by the above-described method.

[0026] This invention also protects the use of the aforementioned silica-based Janus particles in the preparation of emulsions.

[0027] Janus particles are amphiphilic and can be dispersed at the oil-water interface, similar to small molecule surfactants, resulting in emulsion systems with better stability.

[0028] Compared with the prior art, the beneficial effects of the present invention are:

[0029] This invention discloses a method for preparing silica-based Janus particles. The method involves adding a weakly alkaline solution to a mixed solution of silicate ester and modifier to generate silica-based Janus particles, achieving regional modification. This method requires a low reaction temperature, mild conditions, and few steps. The prepared Janus particles are uniform spheres with distinct morphologies on their surfaces, one side being smooth and the other rough. The smooth surface is hydrophilic, while the rough surface is oleophilic. These silica-based Janus particles can be applied in fields such as stabilizing emulsions, supporting catalysts, and controlled drug release. Attached Figure Description

[0030] Figure 1 Scanning electron microscope (SEM) images of silica-based Janus particles prepared in Example 1, Comparative Example 1, and Comparative Example 2. Figure 1 a. Example 1; Figure 1 b. Comparative Example 1; Figure 1 c. Comparative Example 2).

[0031] Figure 2 This is a microscopic image of the Janus particle-stabilized emulsion prepared in Example 1. Detailed Implementation

[0032] The present invention will be further described below with reference to specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise stated, the raw materials and reagents used in the embodiments of the present invention are conventionally purchased raw materials and reagents.

[0033] Example 1

[0034] A method for preparing silica-based Janus particles includes the following steps:

[0035] Add 8 mL of tetraethyl silicate and 0.1 mL of hexadecyltrimethoxysilane to 100 mL of isopropanol, wherein the molar ratio of tetraethyl silicate to hexadecyltrimethoxysilane is 1:0.007. After stirring for 10 minutes, maintain the temperature in a water bath at 30°C and add 24 mL of ammonia water (mass fraction of 25%) dropwise. The addition is completed in 1 hour, and the temperature is maintained and stirring is continued for 6 hours.

[0036] After the reaction was completed, the system was in the form of a white emulsion. After centrifugation, the supernatant was discarded, and the solid residue was washed three times with ethanol and distilled water respectively. After washing, it was dried to constant weight to obtain silicon dioxide-based Janus particles.

[0037] Example 2

[0038] The preparation method of this embodiment is the same as that of Example 1, except that isopropanol is replaced with methanol, tetraethyl silicate is replaced with tetramethoxysilane, and 0.1 mL of hexadecyltrimethoxysilane is replaced with 0.15 mL of octadecyltrimethoxysilane, wherein the molar ratio of tetramethoxysilane to octadecyltrimethoxysilane is 1:0.01.

[0039] Example 3

[0040] The preparation method of this embodiment is the same as that of Example 1, except that isopropanol is replaced with n-propanol, tetraethyl orthosilicate is replaced with propyl orthosilicate, and 0.1 mL of hexadecyltrimethoxysilane is replaced with 2 mL of octadecyltriethoxysilane, wherein the molar ratio of propyl orthosilicate to octadecyltriethoxysilane is 1:0.014.

[0041] Example 4

[0042] The preparation method in this embodiment is the same as in Example 1, except that the water bath temperature is replaced with 20°C, the stirring time is replaced with 12 hours, isopropanol is replaced with ethylene glycol, and the 25% ammonia solution is replaced with 30% ammonia solution.

[0043] Example 5

[0044] The preparation method in this embodiment is the same as that in Example 1, except that the water bath temperature is controlled at 25°C and the mixture is stirred for 9 hours, and isopropanol is replaced with tert-butanol.

[0045] Example 6

[0046] The preparation method of this embodiment is the same as that of Example 1, except that isopropanol is replaced with ethanol, tetraethyl silicate is replaced with isopropyl orthosilicate, and hexadecyltrimethoxysilane is replaced with n-octyltrimethoxysilane.

[0047] Comparative Example 1

[0048] The preparation method of this comparative example is the same as that of Example 1, except that 0.1 mL of hexadecyltrimethoxysilane is not added to this comparative example.

[0049] Comparative Example 2

[0050] The preparation method of this comparative example is the same as that of Example 1, except that 0.1 mL of hexadecyltrimethoxysilane is replaced with 3 mL of hexadecyltrimethoxysilane, wherein the molar ratio of tetraethyl silicate to hexadecyltrimethoxysilane is 1:0.021.

[0051] Comparative Example 3

[0052] The preparation method of this comparative example is the same as that of Example 1, except that 25% ammonia water is used instead of 0.05 mol / L sodium hydroxide solution.

[0053] Comparative Example 4

[0054] The preparation method of this comparative example is the same as that of Example 1, except that 25% ammonia water is used instead of 10% ammonia water.

[0055] Scanning electron microscope image of the silica-based Janus particles prepared in Example 1 is shown below. Figure 1 As described in example a, the particles are uniformly spherical with a diameter ranging from 450 ± 20 nm, with one side rough and the other smooth, exhibiting amphiphilic properties. The Janus particles prepared in Examples 1–6 all possess amphiphilic properties and can therefore be dispersed at the oil-water interface, similar to small molecule surfactants.

[0056] Scanning electron microscopy of the silica particles prepared in Comparative Example 1 is shown below. Figure 1 As shown in b, the diameter is 1180±20nm, the particle surface is completely smooth, and it is a hydrophilic particle.

[0057] Scanning electron microscopy (SEM) images of the silica particles prepared in Comparative Example 2 are shown below. Figure 1 As shown in c, the diameter is 480±20nm, the particle surface is entirely rough, and it is a hydrophobic particle.

[0058] The silica particles prepared in Comparative Example 3 have uneven particle size distribution and rough surfaces, making them hydrophobic particles.

[0059] The silica particles prepared in Comparative Example 4 have a small particle size and rough surfaces, making them hydrophobic.

[0060] The four types of particles prepared in Comparative Examples 1 to 4 were hydrophilic particles, hydrophobic particles, hydrophobic particles, and hydrophobic particles, respectively.

[0061] Based on the aforementioned characteristics of Janus particles, this invention uses the Janus particles prepared in Example 1 as an emulsifier to prepare a high internal phase water-in-oil emulsion. The external phase is a mixture of styrene and divinylbenzene, and the internal phase is water, with an internal phase volume ratio as high as 90%. Furthermore, after two months of storage, no significant oil-water separation was observed, indicating the strong stability of the Janus particles in Example 1. An optical microscope image of the obtained emulsion is shown below. Figure 2 As shown.

[0062] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing silica-based Janus particles, characterized in that, Includes the following steps: A silicate ester and an alkoxysilane with a molar ratio of 1:0.007 were dissolved in a solvent and stirred. Then, a weak alkaline solution with a volume of 1 to 3 times that of the silicate ester was added dropwise. The addition was completed in 1 hour. After reacting at 20 to 30°C for 6 to 12 hours, the silica-based Janus particles were obtained by centrifugation and drying. The weakly alkaline solution is an ammonia solution with a mass fraction of 25% to 30%; The alkoxysilane is one of hexadecyltrimethoxysilane, octadecyltrimethoxysilane, octadecyltriethoxysilane, and n-octyltrimethoxysilane; The solvent is one of isopropanol, methanol, ethanol, n-propanol, ethylene glycol, and tert-butanol.

2. The preparation method according to claim 1, characterized in that, The molar ratio of the silicate ester to the alkoxysilane is 1:0.

01.

3. The preparation method according to claim 1 or 2, characterized in that, The silicate ester is one of tetraethyl silicate, tetramethoxysilane, propyl orthosilicate, and isopropyl orthosilicate.

4. The preparation method according to claim 1, characterized in that, The reaction temperature was 30℃ and the reaction time was 6 hours.

5. The preparation method according to claim 1, characterized in that, After centrifugation, the particles were washed three times with ethanol and distilled water, and then dried to obtain silicon dioxide-based Janus particles.

6. Silica-based Janus particles prepared by the preparation method according to any one of claims 1 to 5.

7. The use of the silica-based Janus particles of claim 6 in the preparation of emulsions.

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