Layered core-satellite particles and methods of making same

Abstract

A method of making layered core-satellite particles, the method comprising: contacting charged particles comprising a first charge, charged nanoparticles comprising a second charge, and a charged binding material selected from the group consisting of charged small molecules and charged polymers, wherein the charged small molecule or the charged polymer comprises a third charge in a solvent, whereby the layered core-satellite particle is formed, where the first charge and the second charge are both positively or negatively charged, the third charge being the opposite charge of the first charge and the second charge, and the second charge being the opposite charge of the first charge and the second charge. The average size of the charged particles is at least about 103 times greater than the average size of the charged nanoparticles.

Description

Technical Field

[0001] The present disclosure relates to a method for preparing hierarchical core - satellite particles. Background Art

[0002] Assembling simple building blocks into functional superstructures with long - range ordered hierarchical structures has broad significance for constructing engineering materials. After decades of innovation, sequential electrostatic layer - by - layer (LbL) assembly has proven to be a general method for fabricating long - range ordered and uniform multi - layer architectures on substrates. These LbL multi - layer structures exhibit nanoscale resolution, with controlled thickness, hierarchical structure, and customized physical / chemical properties, and are applicable to drug delivery, optoelectronics, chemical sensing, energy storage, and catalysis, etc. However, laboratory - intensive protocols are usually required, namely sequential addition of oppositely charged components and cyclic rinsing steps, to avoid contamination between the adsorbed layers, which may lead to over - compensation or over - charging of the opposite components and result in unnecessary aggregation. Although many automated platforms have been developed to fabricate sequential LbL assemblies, the complex deposition cycles and frequent rinsing steps seriously hinder their industrial applications for large - scale production. In fact, the frequent rinsing steps may reduce the adsorbed components, leading to waste of raw materials. Approximately 10% of the loosely adsorbed charged layers are washed away by water in 5 minutes, which may lead to inevitable assembly defects and reduced yields. In fact, one - pot dispersion - based single - step electrostatic LbL nanotechnology can spontaneously drive oppositely charged components and mediate their assembly on substrates in an LbL manner without complex solution replacement and without wasting raw materials, which is ideal for large - scale hierarchical assembly and still poses challenges in materials science.

[0003] The hierarchical core-satellite particles are constructed by combining microparticles (MPs) as the core and nanoparticles (NPs) as the shell, and are novel hybrid materials with enhanced multifunctionality. First, the function of the hybrid material is determined by the morphology of the nano-coated shell, such as NP density, NP geometry, NP arrangement, and the structure of the multilayer nano-coating. Notably, although a sequential layer-by-layer (LbL) method can be used to prepare hierarchical core-satellite particles with a uniform and thickness-controllable multilayer nano-coating on the MP core, the NP geometry and the multilayer shell arrangement cannot be controlled during the assembly process. This is because, during mixing, the oppositely charged pairs precipitate and deposit on the MP core rapidly and randomly, without sufficient reaction time to alter the geometry and arrangement. Second, by using sequential LbL electrostatic assembly, NPs are typically limited to coating on spherical MP cores. The challenge of forming conformal and uniform LbL nano-coatings on non-spherical MP cores with geometric asymmetry still remains. The surface tension of the dispersion and the capillary forces generated during the repeated rinsing process may cause NP aggregation, ultimately resulting in non-conformal and non-uniform outer coatings in the restricted and irregular nanostructured regions of non-spherical MP cores. These two limitations restrict the current sequential LbL nanotechnology from further constructing diverse multi-scale long-range ordered core-satellite superstructures with rich morphology and multifunctionality.

[0004] Generally, building units with opposite charges (such as molecules, polymers, NPs, and MPs) can attract and aggregate with each other when mixed. This principle guides the rapid alternating adsorption of oppositely charged components. For example, in the classical sequential electrostatic LbL assembly of polyanion (sodium poly(styrene sulfonate) (PS)) and polycation (poly(diallyldimethylammonium chloride) (PDDA)) on the MP core, the rapid assembly of highly overlapping polyelectrolyte multilayers from solution typically requires oppositely charged components on a similar length scale, thereby allowing equal charges and a 1:1 stoichiometry ( Figure 1 a-b). However, this traditional multi-step procedure for sequential electrostatic LbL assembly is labor-intensive in the laboratory and usually requires many rinsing steps, which inevitably leads to non-uniform geometric features or defects on the substrate.

[0005] Therefore, improved methods for preparing hierarchical core-satellite particles are needed to address at least some of the above-mentioned drawbacks. SUMMARY OF THE INVENTION

[0006] Sequential layer-by-layer (LbL) processes typically require similarly sized oppositely charged pairs to ensure that electrically neutral solids precipitate readily from solution. In contrast, relatively little attention has been focused on studying electrostatic interactions at interfaces across length scales, namely, the electrostatic interactions between oppositely charged charged MPs, NPs, and small molecules with different specific surface areas. Here, we find that electrostatic interactions at interfaces with specific surface area spanning approximately 10 10 orders of magnitude exhibit some remarkable differences, namely, that mixtures of NPs (≈80 nm) or MPs (≈10 μm) with the same charge and oppositely charged small molecules (≈0.1 nm) can remain stable over time without forming aggregates at a range of NP / MP ratios and concentrations. On this basis, the interparticle attraction between NPs and molecules mediated by small molecules via a gradually decreasing equipotential difference (EPD) results in the spontaneous alternating assembly of NPs and molecules around the corresponding MP cores in a single-step LbL manner, and further the preparation of 3D core–satellite superstructures with uniformly and precisely thickness-controlled submicrometer-scale nanocoated shells. In addition, two unique advantages of single-step LbL assembly are demonstrated. First, this strategy allows for the variation of NP shape in the dispersion, from spherical geometry to nonspherical geometry. Nanoparticles are simultaneously assembled onto the MP cores, thus controlling the arrangement of the nanocoated shells, from dense to porous stacks with uniform multilayers. Second, the single-step LbL process eliminates the repeated rinsing and the surface tension and capillary forces generated in sequential LbL assembly, avoiding the nonconformal and nonuniform outer coatings assembled in the confined and irregular nanostructured regions of nonspherical MPs, and thus enabling the successful loading of conformal and uniform multilayer nanocoated shells on nonspherical MP cores. Therefore, the single-step LbL method described herein is a flexible method for constructing core–satellite structures with different morphologies in the form of NP shells and MP cores. A rich variety of superstructures with diverse and controllable internal structures are achieved through programmable combinatorial assembly procedures.

[0007] Notably, due to the sedimentation tendency of MPs under gravity, batch assembly of superstructures may lead to nonuniformity, thus affecting the yield. To overcome this challenge, monodisperse water-in-oil microdroplets (≈30 μm in diameter) are generated by microfluidics as a conditionally uniform microreactor for one-pot LbL assembly for large-scale production (≈10 4 particles per experiment). By loading various charged components (wires, polymers, and metal oxide particles) inside the droplets, high-quality hierarchical core–satellite particles composed of different compositions are obtained. By exploring the single-step LbL technique of microfluidics, simple building blocks are constructed and assembled in a long-range ordered manner to form hybrid materials with hierarchical structures on a large scale for different technological applications.

[0008] In a first aspect, provided herein is a method for preparing hierarchical core-satellite particles, the method comprising: contacting a charged microparticle comprising a first charge, a charged nanoparticle comprising a second charge, and a charged binding material selected from the group consisting of charged small molecules and charged polymers, wherein the charged small molecule or charged polymer comprises a third charge in a solvent, whereby:

[0009] (a) the charged binding material self-assembles on the surface of the charged microparticle, thereby forming a first self-assembled monolayer of charged binding material comprising the charged binding material disposed on the surface of the charged microparticle;

[0010] (b) the charged nanoparticle self-assembles on the surface of the self-assembled monolayer of charged binding material, thereby forming a first self-assembled monolayer of charged nanoparticles comprising the charged nanoparticles disposed on the surface of the first self-assembled monolayer of charged binding material;

[0011] (c) the charged binding material optionally self-assembles on the first self-assembled monolayer of charged nanoparticles, thereby forming a second self-assembled monolayer of charged binding material comprising the charged binding material disposed on the surface of the first self-assembled monolayer of charged nanoparticles;

[0012] (d) the charged nanoparticle optionally self-assembles on the surface of the second self-assembled monolayer of charged binding material, thereby forming a second self-assembled monolayer of charged nanoparticles comprising the charged nanoparticles disposed on the surface of the second self-assembled monolayer of charged binding material; and

[0013] (e) optionally repeating step (c) or repeating steps (c) and (d) one or more times; thereby forming the hierarchical core-satellite particles, wherein the first charge and the second charge are both positively charged or negatively charged, the third charge is the opposite charge of the first charge and the second charge, and the average size of the charged microparticle is at least about 10 3 times larger than the average size of the charged nanoparticle.

[0014] In certain embodiments, the method is carried out in a single step in one reaction vessel.

[0015] In certain embodiments, the charged microparticle and the charged nanoparticle independently comprise charged silica, metal oxide, or a polymer comprising at least one of a cationic functional group and an anionic functional group.

[0016] In certain embodiments, the cationic functional group is selected from the group consisting of: ammonium, iminium, guanidinium, phosphonium, sulfonium, imidazolium, thiazolium, pyrazolium, pyridinium, pyrrolidinium, piperidinium, pyridazinium, pyrazinium, and pyrimidinium; and the anionic functional group is selected from the group consisting of: carboxylate, sulfate, and phosphate.

[0017] In certain embodiments, the polymer includes poly(dimethyldiallylamine), poly(allylamine); poly(diallylmethylamine); poly(ethyleneimine), polyornithine, polyarginine, polylysine, protamine, chitosan, protein, poly(styrenesulfonic acid), poly(styrenecarboxylic acid), poly(styrenephosphoric acid), poly(acrylic acid), poly(methacrylic acid), poly(vinylsulfonic acid), poly(vinylphosphoric acid), poly(itaconic acid), polyglutamic acid, alginic acid, dextran sulfate, hyaluronic acid, hydroxypropylmethylcellulose pectin, heparin, carrageenan, polynucleic acid, protein, or a charged dendrimer.

[0018] In certain embodiments, the metal oxide is an oxide of a Group 3-16 metal.

[0019] In certain embodiments, the charged small molecule is an alkylsilane comprising a cationic functional group or an anionic functional group.

[0020] In certain embodiments, the cationic functional group is selected from the group consisting of: ammonium, iminium, guanidinium, phosphonium, sulfonium, imidazolium, thiazolium, pyrazolium, pyridinium, pyrrolidinium, piperidinium, pyridazinium, pyrazinium, and pyrimidinium; and the anionic functional group is selected from the group consisting of: carboxylate, sulfate, sulfonate, phosphate, and phosphonate.

[0021] In certain embodiments, the alkylsilane has the formula Y(CR 1 2) m Si(R 2 )(OR 3 )2, where m is an integer selected from 1-10; Y is -COO - 、-(P=O)(O - )2、-O(P=O)(O - )2、-(S=O)2O - 、-O(S=O)2O - 、-NR3 + 、-SR2 + 、-PR3 +, or a cationic heteroaryl, where R is independently hydrogen or alkyl in each case; R 1 is independently hydrogen or alkyl in each case; R 2 is alkyl or -OR 3 ; and R 3 is independently alkyl in each case; or two R 3 together with the oxygen to which they are bonded form a 5- to 6-membered heterocycle.

[0022] In certain embodiments, the alkylsilane has the formula NH3 + (CH2) m Si(R 2 )(OR 3 )2, where m is an integer selected from 1 to 10; R 2 is alkyl or -OR 3 ; and R 3 is independently alkyl in each case.

[0023] In certain embodiments, the alkylsilane undergoes a sol-gel reaction.

[0024] In certain embodiments, the charged microparticles and charged nanoparticles are polymers containing sulfonate or -NR3 + , and the charged small molecule is an alkylsilane having the formula NH3(CH2) m Si(OR 3 )3, where m is an integer selected from 1 to 10 and R 3 is independently alkyl in each case; or the charged microparticles and charged nanoparticles are negatively charged silica and the charged polymer contains -NR3 + , where R is independently hydrogen or alkyl in each case.

[0025] In certain embodiments, the charged binding material is present in the solvent at a lower concentration of at least one-tenth of the concentration of the charged microparticles or charged nanoparticles. 3

[0026] In certain embodiments, the solvent is water.

[0027] In certain embodiments, the solvent is an oil continuous phase containing one or more water-in-oil microdroplets, the water-in-oil microdroplets containing charged microparticles, charged nanoparticles, charged binding material, and water.

[0028] In certain embodiments, one or more water-in-oil microdroplets are generated by a microfluidic device.

[0029] In certain embodiments, the charged microparticles and charged nanoparticles are independently spheres, hollow, ellipsoidal, polyhedral, rod-shaped, plate-shaped, irregularly shaped, or a mixture thereof. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The foregoing aspects and many of the attendant advantages of the present invention will become more readily appreciated and understood when considered in conjunction with the following detailed description, taken in conjunction with the accompanying drawings.

[0031] Figure 1 Schematic diagrams are depicted to illustrate the differences between single-step LbL assembly and sequential LbL assembly. a, Sequential electrostatic LbL assembly of polyanions and polycations on the MP core. b, Rapid aggregation of oppositely charged polyelectrolytes in a 1:1 stoichiometry on a similar length scale. c, Various MPs, NPs, and small molecules with different specific surface areas and geometries (A1, B1, C1, A2, B2, and C2) are stably mixed for single-step LbL assembly. d, Negatively charged PS MPs (10 μm), NPs (80 nm), and positively charged small molecules such as 3-aminopropyltriethoxysilane (APTES) (≈0.1 nm) are used to construct superstructures. e, APTES-mediated interparticle potential difference (PD) serves as the driving force for PS NPs to attach around the PS MP core. f, Single-step LbL assembly of NPs (80 nm) and APTES (≈0.1 nm) on the PS MP core. g-h, Single-step LbL assembly of aggregated NPs and APTES (≈0.1 nm) on the PS MP core to obtain dense or porous nanoshells. i-k, Various core-satellite superstructures assembled from programmable ternary systems.

[0032] Figure 2 Assembly of NPs around the MP core driven by molecule-mediated PD is depicted. a, Schematic diagram showing that PS NPs and MPs adsorb APTES to form PS NP@APTES and PS MP@APTES. b, Schematic diagram showing that with the assembly time and APTES (C APTES)The increase in concentration leads to different adsorption abilities of PD and APTES on the surfaces of the two types of particles. c, Schematic diagram showing that each binary system experiences a transition from a stable, metastable to an unstable state. d, e, Variation of the average particle size and Zeta (ζ) potential of the PS NP / APTES dispersion with time and APTES concentration. f, Variation of the average Zeta potential of the PS MP / APTES dispersion with time and APTES concentration. g, h, TEM images and EDS analysis of the three states 63 hours after adding 100 μL of APTES solution. i, Infrared reflection spectrum of PS@APTES NP 63 h after adding 100 μL of APTES solution. j, The addition of 100 μL of APTES solution mediates interparticle PD between PS MP and PS NP. k, QCM-D results using a mixed dispersion of negatively charged PS NP and 100 μL APTES on a negatively charged chip deposited with PS MP. l, Surface SEM image of PS MP@APTES assembled with sparse PS NP when the mixed dispersion is injected into the QCM-D cell for 800 minutes.

[0033] Figure 3 Depicts a one-step LbL assembly of PS NP around a PS MP core in a ternary model. a, Schematic diagrams I, II, III, and IV show the preparation of MP@poly(silsesquioxane) and its chemical structure. b, Schematic diagrams I, II, and III show the one-step LbL isopotential configuration and assembly mechanism. c, QCM-D results using a mixed dispersion of PS NP and APTES; and d, QCM-D results using a PS NP dispersion on a chip deposited with positively charged PS MP@poly(silsesquioxane). e, QCM-D results using a mixed dispersion of PS NP and APTES on a chip deposited with uncharged MP. f, Zeta potentials of carboxyl-functionalized MP, PS MP@APTES, and PS MP@poly(silsesquioxane). g, Variation of the Zeta potential of the assembled MP and PS NP@APTES with assembly time. h, XPS results and corresponding measurement spectra of the PS nanocoating assembled on a chip deposited with PS MP@poly(silsesquioxane) at 0 h, 10 h, and 20 h. i, QCM-D results using mixed dispersions containing 100 μL, 130 μL, and 150 μL of APTES solution, respectively. j - o, SEM images of the resulting PS nanocoating on the PS MP core at different stages in (c - e). Detailed implementation

[0034] Definition

[0035] Throughout this disclosure and the claims, unless the context requires otherwise, the word "comprising" will be understood to imply the inclusion of the stated integer or group of integers but not the exclusion of any other integer or group of integers.

[0036] Unless otherwise expressly stated, nouns without a specified quantity in this document include singular or plural amounts. Additionally, if the term "about" is used before a numerical value, this teaching also includes the specific numerical value itself, unless otherwise specifically stated. As used herein, unless otherwise stated or inferred, the term "about" refers to a variation of ±10%, ±7%, ±5%, ±3%, ±1%, or ±0% of the nominal value.

[0037] As used herein, "polymeric compound" (or "polymer") refers to a molecule comprising a plurality of one or more repeating units connected by covalent chemical bonds. The polymeric compound can be represented by the general formula I:

[0038] *-(-(Ma) x —(Mb) y —) z *

[0039] General formula I

[0040] where each Ma and Mb is a repeating unit or monomer. The polymer can have only one type of repeating unit or two or more different types of repeating units. When the polymer has only one type of repeating unit, it can be called a homopolymer. When the polymeric compound has two or more different types of repeating units, the terms "copolymer" or "copolymeric compound" can be used instead. For example, the copolymeric compound can include repeating units, where Ma and Mb represent two different repeating units. Unless otherwise stated, the assembly of the repeating units in the copolymer can be head-to-tail, head-to-head, or tail-to-tail. Additionally, unless otherwise stated, the copolymer can be a random copolymer, an alternating copolymer, or a block copolymer. For example, the general formula I can be used to represent a copolymer of Ma and Mb, where the mole fraction of Ma is x and the mole fraction of Mb is y, where the repeating pattern of the comonomers Ma and Mb can be alternating, random, locally random, locally regular, or block, where there are up to z comonomers. In addition to its composition, the polymer can also be characterized by its degree of polymerization (n) and molar mass (e.g., number-average molecular weight (M) and / or weight-average molecular weight (Mw), depending on the measurement technique). The polymers described herein can exist in a variety of stereochemical configurations, such as isotactic, syndiotactic, atactic, or combinations thereof.

[0041] The present invention provides a method for preparing hierarchical core-satellite particles, the method comprising: contacting a charged microparticle having a first charge, a charged nanoparticle having a second charge, and a charged binding material selected from the group consisting of charged small molecules and charged polymers, wherein the charged small molecule or the charged polymer has a third charge in a solvent, whereby:

[0042] (a) the charged binding material self-assembles on the surface of the charged microparticle to form a first self-assembled monolayer of charged binding material, which comprises the charged binding material disposed on the surface of the charged microparticle;

[0043] (b) the charged nanoparticle self-assembles on the surface of the self-assembled monolayer of charged binding material to form a first self-assembled monolayer of charged nanoparticles, which comprises the charged nanoparticles disposed on the surface of the first self-assembled monolayer of charged binding material;

[0044] (c) the charged binding material optionally self-assembles on the first self-assembled monolayer of charged nanoparticles to form a second self-assembled monolayer of charged binding material, which comprises the charged binding material disposed on the surface of the first self-assembled monolayer of charged nanoparticles;

[0045] (d) the charged nanoparticle optionally self-assembles on the surface of the second self-assembled monolayer of charged binding material to form a second self-assembled monolayer of charged nanoparticles, which comprises the charged nanoparticles disposed on the surface of the second self-assembled monolayer of charged binding material; and

[0046] (e) optionally repeating step (c) or steps (c) and (d) one or more times;

[0047] thereby forming the hierarchical core-satellite particles, wherein the first charge and the second charge are both positively charged or negatively charged, the third charge is the opposite charge of the first charge and the second charge, and the average size of the charged microparticle is at least about 10 3 times larger than the average size of the charged nanoparticle.

[0048] In the case where both steps (c) and (d) are repeated one or more times, step (c) can be optionally repeated once.

[0049] In certain embodiments, the first charge and the second charge are both positively charged; and the third charge is negatively charged. In certain embodiments, the first charge and the second charge are both negatively charged; and the third charge is positively charged.

[0050] The charged microparticle and the charged nanoparticle can independently comprise charged silica, metal oxide, or a polymer comprising at least one of a cationic functional group and an anionic functional group.

[0051] The charged silica can be prepared according to any method known in the art and can contain a net negative charge or a net positive charge. The charge of the charged silica can be altered by the appropriate application of surface functionalization and / or coating. Methods for preparing charged silica are well known in the art.

[0052] The metal oxide is not particularly limited and can include any negatively or positively charged metal oxide. In certain embodiments, the metal oxide is an oxide of a Group 1, Group 2, Group 3, Group 4, Group 5, Group 6, Group 7, Group 8, Group 9, Group 10, Group 11, Group 12, Group 13, Group 14, Group 15, or Group 16 metal. The metal oxide can include alkali metals such as lithium, sodium, potassium, rubidium, and cesium; alkaline earth metals such as beryllium, magnesium, calcium, strontium, and barium, transition metals such as scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, yttrium, zirconium, niobium, molybdenum, technetium, ruthenium, rhodium, palladium, silver, cadmium, lutetium, hafnium, tantalum, tungsten, rhenium, osmium, iridium, platinum, gold, and mercury, post-transition metals such as aluminum, gallium, indium, thallium, tin, lead, bismuth, polonium, astatine, and metalloids such as boron, silicon, germanium, arsenic, antimony, and tellurium. The metal oxide can contain Group 1-16 metals in +1, +2, +3, +4, +5, +6, or +7 oxidation states. In certain embodiments, the metal oxide includes noble metal catalysts (such as Ru, Rh, Pd, Ag, Os, Ir, Pt, and Ag) or non-noble metal catalysts (such as Fe, Co, Ni, and Cu). In certain embodiments, the metal oxide contains V 2+ 、V 3+ 、V 4+ 、V 5+ 、Cr 2+ 、Cr 3+ 、Cr 6+ 、Fe 2+ 、Fe 3+ 、Co 2+ 、Co 3+ 、Ni 2+ 、Ni 3+ 、Cu 1+ 、Cu 2+ 、Zn 1+ 、Mo 2+ 、Mo 3+ 、Mo 4+ 、Mo 5+ 、Mo 6+ 、Se 2+ 、Se 4+ 、Sn 2 + 、Sn 4+ 、Pt 2+ 、Pt 4+ 、Ru 2+ 、Ru3+ , Ru 4+ , Ru 5+ , Ru 6+ , Pd 2+ , Pd 4+ , W 2+ , W 3+ , W 4+ , W 5+ , W 6+ , Ir 1+ , Ir 3+ , Os 3+ , Os 4 + , Os 5+ , Os 6+ , Rh 1+ , Rh 3+ , Nb 3+ , Nb 4+ , Nb 5+ , Ta 3+ , Ta 4+ , Ta 5+ , Pb 2+ , Pb 4+ , Bi 1+ , Bi 2+ , Au 1+ , Au 3+ , Ag 1+ , Sc 3+ or Y 3+ . Exemplary metal oxides include, but are not limited to, CoO3, Co3O4, CoO, CuO, Cu2O, NiO, Ni2O3, Ag2O, AgO, FeO, Fe2O3, Fe3O4, ZnO, PdO, PdO2, PtO, and PtO2.

[0053] The polymers used in the methods described herein are not particularly limited and encompass all types of polymers that contain negative or positive charges. In certain embodiments, the polymer is a zwitterionic substance that contains a negatively charged moiety and a positively charged moiety, and that contains a net positive or net negative charge.

[0054] The polymer can be a linear polymer, a branched polymer, or a dendritic polymer. In certain embodiments, the polymer is crosslinked.

[0055] The polymer may comprise one or more repeating units selected from the group consisting of ethylene, propylene, butadiene, styrene, acrylonitrile, carbonate, lactate, acrylate, methacrylate, ethylene glycol, propylene glycol, and vinyl chloride. Exemplary polymers include polymer moieties selected from the group consisting of polyurethane, styrene-ethylene-butene-styrene block thermoplastic elastomer, polyolefin elastomer, thermoplastic polyester elastomer, polyethylene, polypropylene, polystyrene, styrene-acrylonitrile copolymer, acrylonitrile-butadiene-styrene terpolymer, terephthalic acid-tetramethylcyclo butanediol-cyclohexanediol copolymer, polylactic acid, polymethyl methacrylate, polyethylene terephthalate, polycarbonate, polymethylpentene, polyamide, polyvinyl chloride, ethylene-vinyl acetate copolymer, styrene-methacrylate copolymer, methyl methacrylate-butadiene-styrene terpolymer, and mixtures thereof, and copolymers thereof.

[0056] The polymer may comprise cationic functional groups selected from the group consisting of ammonium, iminium, guanidinium, phosphonium, sulfonium, imidazolium, thiazolium, pyrazolium, pyridinium, pyrrolidinium, piperidinium, pyridazinium, pyrazinium, and pyrimidinium.

[0057] The polymer may comprise anionic functional groups selected from the group consisting of carboxylate, sulfate, and phosphate.

[0058] Exemplary polymers containing cationic functional groups include, but are not limited to, poly(dimethyldiallylamine), poly(allylamine); poly(diallylmethylamine); poly(ethyleneimine), polyornithine, polyarginine, polylysine, protamine, chitosan, charged dendrimers, and proteins. In certain embodiments, the polymer comprises poly(diallyldimethylammonium).

[0059] Exemplary polymers containing anionic functional groups include, but are not limited to, poly(styrenesulfonic acid), poly(styrenecarboxylic acid), poly(styrenephosphoric acid), poly(acrylic acid), poly(methacrylic acid), poly(vinylsulfonic acid), poly(vinylphosphoric acid), poly(itaconic acid), polyglutamic acid, alginic acid, dextran sulfate, hyaluronic acid, hydroxypropylmethylcellulose pectin, heparin, carrageenan, polynucleic acids, proteins, charged dendrimers, charged polymethacrylates, charged silica, metal oxides. In certain embodiments, the polymer comprises poly(p-styrenesulfonate).

[0060] Charged microparticles, charged nanoparticles, and charged small molecules or charged polymers must be charge-balanced and coexist with one or more counterions.

[0061] In the case where the charged microparticles, charged nanoparticles, charged small molecules or charged polymers contain a negative charge or a net negative charge, the counterions can be selected from one or more cations. The type of cation is not particularly limited, and the present disclosure encompasses all cations. Exemplary cations include, but are not limited to, NR4, lithium, sodium, potassium, rubidium, cesium, beryllium, magnesium, calcium, strontium, barium, zinc, silver, iron, copper, lead, tin, mercury, nickel, cobalt, and aluminum, etc., where R is independently hydrogen, alkyl, cycloalkyl, aralkyl, aryl or heteroaryl in each case; or two Rs together with the nitrogen to which they are attached form a 3-7 membered heterocyclic or heteroaryl ring.

[0062] In the case where the charged microparticle, charged nanoparticle, charged small molecule or charged polymer contains a positive charge or a net positive charge, the counterion can be selected from one or more anions. The type of anion is not particularly limited, and the present disclosure encompasses all anions. Exemplary anions include, but are not limited to, halide ions (e.g., fluoride ion, chloride ion, bromide ion, and iodide ion), hydroxide, oxide, peroxide ion, monohydrogen peroxide ion, sulfide ion, hydrosulfide ion, selenide ion, azide ion, carbonate, hydrogencarbonate, nitrite, nitrate, sulfate, hydrogensulfate, thiosulfate, phosphate, hydrogenphosphate, dihydrogenphosphate, phosphite, silicate, arsenate, chromate, dichromate, permanganate, hypochlorite, chlorite, chlorate, perchlorate, bromate, iodate, cyanate ion, thiocyanate ion, cyanide, formate, acetate, oxalate, tetrahaloborate, tetrahaloaluminate, adipate, alginate, ascorbate, aspartate, benzenesulfonate, besylate, benzoate, hydrogensulfate, borate, butyrate, camphorate, camphorsulfonate, citrate, cyclopentanepropionate, digluconate, dodecyl sulfate, ethanesulfonate, formate, fumarate, glucoheptonate, glycerophosphate, gluconate, hemisulfate, heptanoate, hexanoate, hydroiodide, 2-hydroxyethanesulfonate, lactobionate, lactate, laurate, lauryl sulfate, malate, maleate, malonate, methanesulfonate, 2-naphthalenesulfonate, nicotinate, oleate, oxalate, palmitate, pamoate, pectinate, persulfate, 3-phenylpropionate, phosphate, picrate, pivalate, propionate, stearate, succinate, sulfate, tartrate, p-toluenesulfonate, undecanoate, valerate, etc.

[0063] The charged small molecule can be an alkylsilane containing a cationic functional group or an anionic functional group. In the case where the alkylsilane contains a cationic functional group, the cationic functional group can be selected from the group consisting of ammonium, iminium ion, guanidinium, phosphonium, sulfonium, imidazolium, thiazolium, pyrazolium, pyridinium, pyrrolidinium, piperidinium, pyridazinium, pyrazinium, and pyrimidinium. In the case where the alkylsilane contains an anionic functional group, the anionic functional group can be selected from the group consisting of carboxylate, sulfate, sulfonate, phosphate, and phosphonate.

[0064] In certain embodiments, the alkylsilane has the formula Y(CR 1 2) m Si(R 2 )(OR 3 )2, where m is an integer selected from 1 - 10, 1 - 9, 1 - 8, 1 - 7, 1 - 6, 1 - 5, 1 - 4, 1 - 3, 1 - 2, 2 - 6, 2 - 5, 2 - 4, or 2 - 3; Y is -COO - , -(P=O)(O - )2, -O(P=O)(O - )2, -(S=O)2O - , -O(S=O)2O - , -NR3 + , -SR2 + , -PR3 + , or a cationic heteroaryl, where R is independently hydrogen or alkyl (e.g., C1 - C6 alkyl, C1 - C5 alkyl, C1 - C4 alkyl, C1 - C3 alkyl, or C1 - C2 alkyl) in each case; R 1 is independently hydrogen or alkyl in each case; R 2 is alkyl (e.g., C1 - C6 alkyl, C1 - C5 alkyl, C1 - C4 alkyl, C1 - C3 alkyl, or C1 - C2 alkyl) or -OR 3 ; and R 3 is independently alkyl (e.g., C1 - C6 alkyl, C1 - C5 alkyl, C1 - C4 alkyl, C1 - C3 alkyl, or C1 - C2 alkyl) in each case; or two R 3 together with the oxygen to which they are bonded form a 5 - 6 membered heterocycle.

[0065] In certain embodiments, the alkylsilane has the formula NH3 + (CH2) m Si(R 2 )(OR 3 )2, where m is an integer selected from 1 - 10, 1 - 9, 1 - 8, 1 - 7, 1 - 6, 1 - 5, 1 - 4, 1 - 3, 1 - 2, 2 - 6, 2 - 5, 2 - 4, or 2 - 3; R 2 is alkyl (e.g., C1 - C6 alkyl, C1 - C5 alkyl, C1 - C4 alkyl, C1 - C3 alkyl, or C1 - C2 alkyl) or -OR 3 ; and R 3 is independently alkyl (e.g., C1 - C6 alkyl, C1 - C5 alkyl, C1 - C4 alkyl, C1 - C3 alkyl, or C1 - C2 alkyl) in each case. In certain embodiments, the alkylsilane is 3 - aminopropyltriethoxysilane or 3 - aminopropyltrimethoxysilane.

[0066] In the case where the charged small molecule contains an alkylsilane, when forming a self-assembled monolayer of charged small molecules, at least some or all of the alkylsilanes can undergo a sol-gel reaction to form a self-assembled monolayer of charged small molecules containing charged polysiloxanes.

[0067] The charged polymers used in the methods described herein are not particularly limited, and all types of charged polymers that contain negative or positive charges and are soluble in solvents are contemplated. In certain embodiments, the charged polymer is a zwitterionic substance that contains negatively charged moieties and positively charged moieties, and it contains a net positive charge or a net negative charge.

[0068] The charged polymer can be a linear charged polymer, a branched charged polymer, or a charged dendrimer. In certain embodiments, the charged polymer is crosslinked.

[0069] The charged polymer can contain one or more repeating units selected from the group consisting of ethylene, propylene, butadiene, styrene, acrylonitrile, carbonate, lactate, acrylate, methacrylate, ethylene glycol, propylene glycol, and vinyl chloride. Exemplary charged polymers contain polymeric moieties selected from the group consisting of polyurethane, styrene-ethylene-butene-styrene block thermoplastic elastomer, polyolefin elastomer, thermoplastic polyester elastomer, polyethylene, polypropylene, polystyrene, styrene-acrylonitrile copolymer, acrylonitrile-butadiene-styrene terpolymer, terephthalic acid-tetramethylcyclobutanediol-cyclohexanediol copolymer, polylactic acid, polymethyl methacrylate, polyethylene terephthalate, polycarbonate, polymethylpentene, polyamide, polyvinyl chloride, ethylene-vinyl acetate copolymer, styrene-methacrylate copolymer, methyl methacrylate-butadiene-styrene terpolymer, and mixtures thereof, and copolymers thereof.

[0070] The charged polymer can contain cationic functional groups selected from the group consisting of ammonium, iminium, guanidinium, phosphonium, sulfonium, imidazolium, thiazolium, pyrazolium, pyridinium, pyrrolidinium, piperidinium, pyridazinium, pyrazinium, and pyrimidinium.

[0071] The charged polymer can contain anionic functional groups selected from the group consisting of carboxylate, sulfate, and phosphate. In certain embodiments, the charged polymer contains poly(diallyldimethylammonium).

[0072] The volume ratio of the charged nanoparticle solution to the charged microparticle solution in the solvent can be 10 3 -300:1.

[0073] The charged binding material is present in the solvent at a concentration that is at least 28 times higher than the concentration of the charged particles or charged nanoparticles. In certain embodiments, the mass ratio of the charged binding material to the charged particles can be in the range of 100 - 1,000:1 or 300 - 1,000:1, respectively.

[0074] The average size of the charged particles is at least 1.25 times, 1.5 times, 2 times, 3 times, 4 times, 5 times, 6 times, 7 times, 8 times, 9 times, 10 times, 50 times, 100 times, 200 times, 300 times, 400 times, 500 times, 600 times, 700 times, 800 times, 900 times, 1,000 times, 1,500 times, 2,000 times, 5,000 times, 7,000 times, 10,000 times, 15,000 times, 20,000 times, 25,000 times, or 30,000 times larger than the average size of the charged nanoparticles. In certain embodiments, the average size of the charged particles is 10 - 30,000 times, 100 - 30,000 times, 1,000 - 30,000 times, 10,000 - 30,000 times, 15,000 - 30,000 times, 20,000 - 30,000 times, 5,000 - 15,000 times, 10 - 1,000 times, 50 - 1,000 times, 100 - 1,000 times, 200 - 1,000 times, 300 - 1,000 times, 400 - 1,000 times, 500 - 1,000 times, 600 - 1,000 times, 700 - 1,000 times, 800 - 1,000 times, 900 - 1,000 times, 10 - 900 times, 10 - 800 times, 10 - 700 times, 10 - 600 times, 10 - 500 times, 10 - 400 times, 10 - 300 times, 10 - 200 times, 10 - 100 times, 50 - 900 times, 100 - 800 times, 200 - 700 times, 300 - 600 times, 400 - 500 times, 2 - 100 times, 2 - 90 times, 2 - 80 times, 2 - 70 times, 2 - 60 times, 2 - 50 times, 2 - 40 times, 2 - 30 times, 2 - 20 times, 10 - 70 times, 10 - 60 times, 10 - 50 times, 10 - 40 times, 10 - 30 times, 10 - 20 times, 20 - 70 times, 20 - 60 times, 20 - 40 times, 20 - 30 times larger than the average size of the charged nanoparticles.

[0075] Since the methods provided herein can be used in combination with charged particles and charged nanoparticles of any shape, their shape is not particularly limited. Exemplary shapes include, but are not limited to, spheres, hollow, oval, polyhedra, rod-shaped, plate-shaped, irregular shapes, or mixtures thereof.

[0076] Since the charged nanoparticles have a charge opposite to that of the charged binding material, in certain embodiments, the method may further include depositing the charged binding material on the surface of the charged microparticles, thereby forming a self-assembled monolayer of the charged binding material that includes the charged binding material disposed on the surface of the charged microparticles. In certain embodiments, the deposition of the monolayer of the charged binding material can change the shape of the charged nanoparticles. For example, the deposition of the monolayer of the charged binding material can change the shape of spherical or irregularly shaped charged nanoparticles to elliptical, polyhedral, rod-shaped, or plate-shaped charged nanoparticles.

[0077] The preparation of the hierarchical core-satellite particles can be carried out in any solvent in which the charged microparticles and the charged nanoparticles are insoluble and the charged binding material is soluble. The choice of the appropriate solvent will depend on the physical / chemical properties of the charged microparticles, the charged nanoparticles, and the charged binding material. In certain embodiments, the solvent comprises water.

[0078] In certain embodiments, the solvent is an oil continuous phase that includes one or more water-in-oil microdroplets that contain the charged microparticles, the charged nanoparticles, the charged binding material, and water.

[0079] Advantageously, it has been found that when the methods described herein are carried out in monodisperse water-in-oil microdroplets prepared using a microfluidic device, up to 10 4 hierarchical core-satellite particles can be prepared per batch.

[0080] The oil continuous phase that can be used in the step can be any oil phase that is substantially immiscible with water and capable of producing stable water-in-oil droplets. In certain embodiments, the oil phase is oil, a nonpolar solvent, a fluorinated oil, a silicone oil, rapeseed oil, mineral oil, a fluorinated surfactant, a fluorocarbon, a silicone oil, decane, tetradecane, hexadecane, a commercially available droplet oil (also known as droplet-forming oil), such as Biorad droplet-forming oil, etc., or any combination thereof. Suitable oil phases are known to those skilled in the art, in which the aqueous phase spontaneously results in the formation of water droplets or isolated volumes or compartments surrounded by the oil phase.

[0081] In certain embodiments, the oil phase further includes one or more surfactants. The surfactant can be a sorbitan-based carboxylic acid ester, such as sorbitan monolaurate (Span 20), sorbitan monopalmitate (Span 40), sorbitan monostearate (Span 60), sorbitan monooleate (Span 80), Tween 20 (polysorbate 20), and Tween 40 (polysorbate 40), a polyoxyethylated alkylphenol, such as Triton X-100, a polyoxyethylated straight-chain alcohol, a polyoxyethylated polyoxypropylene glycol, a polyoxyethylated thiol, a long-chain carboxylic acid ester, Triton X-100, etc., or a fluorinated surfactant.

[0082] Here, a novel steady state was explored to generate various suspended functional components without forming aggregates when mixing oppositely charged building blocks with different specific surface areas and geometries ( Figure 1 c). On this basis, we further explored the general mechanism of single-step LbL assembly to achieve a high level of morphological control over the above-mentioned building blocks, where NPs and molecules spontaneously assemble around the MP core to form multi-component core-satellite superstructures, and the core geometry, nanoshell uniformity, thickness, and arrangement can be configured in a programmable manner according to needs. A ternary system consisting of negatively charged PS MPs (10 μm) and PS NPs (80 nm) and positively charged small molecules (APTES ~0.1 nm) was implemented to illustrate the assembly mechanism because the specific surface areas among them have different length scales (about 10 10 orders of magnitude)( Figure 1 c-d). The interfacial electrostatic interactions at different length scales of about 10 10 orders of magnitude were studied, revealing that when the concentration of APTES is about 10 4 times lower than the concentration of MPs or NPs, adding oppositely charged small molecules does not lead to the rapid aggregation of each binary mixed dispersion of PS NPs / APTES or PS MPs / APTES. Significantly, negatively charged MPs and NPs continuously adsorb APTES on their surfaces until their charges are reversed to be positively charged, resulting in the gradual transformation of each mixed dispersion from a stable suspension to a suspension aggregate of multiple particles and finally to an unstable sedimentation state. Since the specific surface area of individual NPs is approximately 10 4 times larger than that of individual MPs, the surface charge of MPs is preferentially reversed to positive in a solution with homogeneous APTES. At the same time, since the surface charge of NPs remains negative, small molecule-mediated interparticle PD causes NPs to assemble around MPs, forming a superstructure with a core (MP)-satellite (NP) structure through single-step LbL assembly( Figure 1 e). To demonstrate the generality of this method, various core-satellite structures were constructed by assembling different building blocks, such as positively charged polymer PDDA, negatively charged silica MPs (1 μm, 2 μm), and charged silica NPs (30 nm, 200 nm, 500 nm, 800 nm).

[0083] It should be noted that the PD driving force mediated only by small molecules does not allow many NPs to assemble around the MP core to form a uniform LbL structure. In fact, it is necessary to precoat a dense network of crosslinked poly(silsesquioxane) on the MP, which endows a positive zeta potential density on the outermost layer to induce a well-defined LbL zeta potential configuration, consisting of a uniform multi-layer of APTES (positive zeta potential) and NP coating (negative zeta potential) around the MP core. In addition, since APTES is continuously consumed from the dispersion during the assembly process, the zeta potential difference (EPD) between APTES and the nano-coating decreases with the increase in the number of layers to form an assembly with a well-defined multi-layer structure. As the EPD gradually decreases, NPs tend to assemble on the previously assembled APTES layer rather than other layers, which ensures that the oppositely charged NPs and APTES are spontaneously and alternately deposited around the MP core in a LbL manner with the increase in assembly time, resulting in a superstructure with a conformal, uniform and thickness-controllable nanoshell ( Figure 1 f).

[0084] By using aggregated NPs to replace the PS NPs in the above ternary system, another ternary system consisting of negatively charged PS MPs (10 μm), positively charged small molecules (APTES ~0.1 nm) and aggregated NPs was obtained. Since the aggregated NPs are electrostatically complexed by APTES and PS, a low concentration of APTES not only provides a reduced EPD to facilitate spontaneous LbL assembly, but also can electrostatically complex with the aggregated NPs in the dispersion to change the geometry of the NPs from spherical to rod-like, thus forming different multi-layer nanoshells with a dense to porous arrangement ( Figure 1 g-h). In addition, the one-step LbL process eliminates the repeated rinsing and the resulting surface tension and capillary forces, making it more versatile and allowing programmable combinations of different cores and multi-layer nanoshells to form novel LbL coating structures without restricting the composition and geometry of NPs and MPs. Various core-satellite superstructures assembled from programmable ternary systems composed of non-spherical building blocks have been demonstrated, such as nanofibers as the shell, or spiky, skeletonized porous MPs as the core ( Figure 1 i-k).

[0085] First, the one-step LbL mechanism of the binary hybrid dispersions of PS NPs / APTES or PS MPs / APTES was illustrated. The positively charged APTES can continuously adsorb on the surfaces of negatively charged PS MPs and NPs and form PS MP@APTES and PS NP@APTES through electrostatic attraction ( Figure 2 a). The charges of the two kinds of particles tend to gradually reverse to positive charges, and their suspension states change with time and the introduced APTES concentration ( Figure 2b). Each binary system undergoes (I) a stable suspension state: no charge inversion and particle sedimentation, (II) metastable: charge inversion and suspension assembly of multiple particles, and (III) an unstable state: charge inversion and sedimentation of most particles Figure 2 c). Due to the different specific surface areas of PS MPs and NPs, the adsorption capacity of APTES on their surfaces is different. Therefore, it is possible to find a specific concentration range of APTES that causes the charge of PS MP@APTES to invert to a positive charge in the metastable state (II), while PS NP@APTES remains negatively charged in the stable state (I). Therefore, the APTES-mediated interparticle PD between PSMP@APTES and PS NP@APTES is the main driving force for assembly Figure 2 a, b).

[0086] In the case of the NP / APTES binary system, when a low concentration of APTES (about 100 μL) is added, the Zeta potential of the mixed dispersion rapidly increases from -21.1 ± 0.2 mV to -14.3 ± 0.3 mV, indicating the formation of PS NP@APTES. Then, the Zeta potential of PSNP@APTES continuously increases from -14.3 ± 0.3 mV to -10.9 ± 0.2 mV within 100 hours, while the size of PS NP@APTES remains constant over time, with a diameter of about 106 ± 0.3 nm. This indicates that 100 μL of APTES solution is not sufficient to invert the charge of PSNP@APTES to a positive charge, PS NP@APTES remains negatively charged, and interparticle electrostatic repulsion results in a stable suspension without any aggregation Figure 2 c, state I). When the concentration of the APTES solution is increased from 200 μL to 500 μL, more APTES is adsorbed on the surface of PS NP@APTES. The Zeta potential of the mixed dispersion increases to near zero but remains negative within 100 hours Figure 2 d). In addition, a large negatively charged region is observed in the Zeta potential distribution curve, indicating that a small amount of negatively charged PSNP@APTES is inverted to positively charged, while most PS NP@APTES still remain negatively charged. The electrostatic attraction between positively charged PS NP@APTES and negatively charged PS NP@APTES results in aggregation. Since the average size of the aggregates (about 258 ± 12 nm) is almost twice the size of individual PS NPs (about 106 ± 0.3 nm) Figure 2 d), their gravity is not sufficient to cause them to sink, but rather keeps them in a suspended assembly state Figure 2c, state II). When the APTES concentration increases to a certain range (600 μL to 2000 μL), the adsorption of sufficient APTES helps to reverse most of the negatively charged PS NP@APTES to positively charged, and a large positively charged region is observed in the Zeta potential distribution curve. The Zeta potential of the mixed dispersion often crosses zero within 100 hours ( Figure 2 e). The strong electrostatic attraction between most of the positively charged PS NP@APTES and the negatively charged PS NP@APTES results in obvious aggregates with an irregular size distribution ( Figure 2 e), further leading to an unstable sedimentation state ( Figure 2 c, state III).

[0087] PS NP@APTES in different states was recorded under a transmission electron microscope (TEM) ( Figure 2 g). When the amount of APTES is less than 500 μL (state I), well-dispersed nanoparticles (about 50 nm in diameter) are observed. When the amount of APTES reaches the metastable state (state II) in the range of 600 - 2000 μL, small aggregates (200 - 500 nm in diameter) are observed. However, when the amount of APTES exceeds 2000 μL approaching the unstable sedimentation state (state III), large irregular aggregates (about 1000 nm in diameter) are observed. In addition, the surface roughness of PS NP@APTES was measured by TEM, indicating that the surface roughness of the NP increases when adsorbing APTES over time. The EDS results show the elemental distribution of N, Si, O, and C in PS@APTES NP ( Figure 2 h). The attenuated total reflection (ATR)-FTIR spectrum of PS@APTES NP shows that there is a Si - O - Si bond on the particle surface at 1080 cm -1 −1 ( Figure 2 i), indicating that the adsorbed APTES on the NP leads to the above three states of the binary system.

[0088] For the binary system of PS MPs / APTES, a similar three - state situation was observed ( Figure 2 c). However, since the specific surface area of individual PS NPs is about 10 4 times larger than that of PS MPs, when the same APTES concentration is added, the APTES density on the surface of PS MPs is higher than that of PS NPs. Therefore, compared with PS NP@APTES, PS MP@APTES preferentially reverses from negative to positive to reach the metastable state (state II), but the charge of PS NP@APTES remains negative (state I). For example, in the NP / APTES system, adding a small amount of APTES solution (100 μL) is not sufficient to reverse the Zeta potential (Figure 2 d), while in the MP / APTES system, this is sufficient to reverse the Zeta potential ( Figure 2 f). The Zeta potential of PS MP@APTES increased to -1.06 ± 0.3 mV within 5 hours and started to cross zero after the next 63 hours, reaching a positive value of +2.72 ± 0.5 mV ( Figure 2 f).

[0089] For the ternary system of NP / MP / APTES, the addition of 100 μL of APTES solution is ideal for mediating interparticle PD between positively charged PS MP@APTES and negatively charged PS NP@APTES ( Figure 2 j). APTES-mediated interparticle PD can drive the assembly of negatively charged PS NP@APTES around the positively charged PS MP@APTES core to form core-shell structure assemblies. A quartz crystal microbalance with dissipation function (QCM-D) was used to monitor the ternary assembly process in real time. As the mass of the crystal chip increased due to adsorption, the resonance frequency (Δf) decreased, while the energy dissipation parameter (ΔD) provided information about the viscoelastic energy of the adsorbed layer. 360 minutes after injecting the mixed dispersion of APTES and PS NP into the compartment, the QCM-D results showed that Δf continued to decrease with a significant slope, indicating that the positively charged APTES was rapidly adsorbed by the negatively charged PS MP deposited on the chip ( Figure 2 k). Thereafter, the slope of the Δf decrease became gentle because APTES-mediated PD was formed and the driving force decreased due to PD. As a result, the NPs were driven to slowly assemble on the outermost layer of PS MP@APTES ( Figure 2 l). ΔD increased correspondingly during the assembly process ( Figure 2 k). The PD formation time of 360 minutes in the ternary system ( Figure 2 k) was roughly consistent with the charge reversal time of 6 hours in the PS MP / APTES binary system ( Figure 2 f), further demonstrating that PD is mediated by APTES.

[0090] It is worth noting that the non-uniform distribution of carboxyl groups on the surface of PS MP endows the outermost layer with non-equipotential negative densities, which further leads to non-equipotential positive densities on the outermost layer of PS MP@APTES after adsorbing APTES. The PS NPs are sparsely and randomly assembled on the surface of PS MP ( Figure 2l), uneven layers are formed over time. Experimental results show that molecule-mediated PD can provide the driving force for assembling NPs on MPs, while other processing procedures are required to construct NP / MP / APTES ternary assemblies with a uniform layer-by-layer (LbL) structure.

[0091] To induce a well-defined LbL configuration of NPs around the MP core, it is necessary to construct initial equipotential sites on the outermost layer of the PS MPs ( Figure 3 a). Therefore, positively charged APTES molecules are polymerized on the PS MPs into a poly(silsesquioxane) network before assembling the NPs ( Figure 3 a, I-II). As a result, the negatively charged PS MP surface is modified with a positively charged poly(silsesquioxane) APTES network ( Figure 3 a, III). Due to the electrostatic attraction and condensation reaction of the Si-O-Si bonds, a stable, uniform, and dense poly(silsesquioxane) network is coated on the PS MP surface ( Figure 3 a, IV), thus forming PS MP@poly(silsesquioxane). This thin layer of APTES poly(silsesquioxane) with positive equipotential sites will ensure equal negative potentials between the nth and n+1th layers of the NP coating, thus mediating a uniform LbL coating.

[0092] The resulting thin layer of APTES poly(silsesquioxane) has a thickness of several tens of nanometers after being soaked in water for 100 hours. During the coating process, the Zeta potential of the PS Mp@poly(silsesquioxane) gradually increased from -45.5±2 mV to +21.6±0.2 mV within 24 hours and remained at +26.6±0.5 mV after being soaked for 100 hours. Notably, the Zeta potential of the PS MP@poly(silsesquioxane) is higher than that of the raw PS MPs mediated by APTES (+2.72±0.5 mV) ( Figure 3 f). The dense and uniform poly(silsesquioxane) network provides equipotential sites on the PS MP@poly(silsesquioxane) to ensure a uniform structure for the subsequent LbL NP coating.

[0093] Figure 3 Certain embodiments of the method described herein are shown in b. When mixing PS MP@poly(silsesquioxane), PS NPs, and APTES, the LbL equipotential structure is spontaneously constructed in three steps: First, the PSMP@poly(silsesquioxane) with positive equipotential sites adsorbs a uniform monolayer of negatively charged PS NP@APTES nanocoatings, and then negative equipotential sites are formed around the outermost layer ( Figure 3b, I). Second, the formed nano - coating with negative equipotential sites adsorbs a positively charged APTES monolayer in the dispersion for charge inversion, ensuring positive equipotential sites for assembling the next uniform nano - coating. Figure 3 b II). Third, alternating positive and negative equipotential sites are continuously constructed around the core to spontaneously form an LbL structure. Figure 3 b, II - III). The alternating positive and negative equipotential sites between each APTES layer and the nano - coating contribute to the formation of an interlayer equipotential difference (EPD) to ensure the uniformity of the assembled nano - coating. When the number of NP layers increases, the coated APTES gradually reduces the positive potential, resulting in the coated NP layer gradually reducing the EPD, i.e., EPD1 > EPD N > EPD N+1 . It should be noted that the gradually decreasing EPD plays an important role in the spontaneous assembly of PS NPs and APTES around the PS MP@poly(silsesquioxane) core without forming random aggregates, thus forming an LbL structure.

[0094] QCM - D is used to monitor the nano - coating assembly process in real - time. By measuring the dynamic changes in the QCM frequency to indicate the driving force of the interlayer EPD, three stages are shown: 1. Rapid deposition of a single - layer nano - coating (stage bI); 2. Multilayer nano - coatings gradually assembled by NPs (stage bII); 3. Stable LbL structure (stage b III). Figure 3 c). When PS NPs and APTES (100 μL) are mixed in stage bI, due to the positively charged poly(silsesquioxane) network, a high interlayer EPD is established between the outermost layer of PS MP@poly(silsesquioxane) and NP@APTES, which promotes significant electrostatic attraction to construct a single - layer NP@APTES. A sharp decrease in Δf is observed within a few minutes, indicating the rapid adsorption of negatively charged NP@APTES by positively charged PS MP@poly(silsesquioxane). Therefore, a uniform single - layer of PS NP@APTES assembled on the surface of PS MP@poly(silsesquioxane) is observed under SEM. Figure 3 j). After that, in stage bII, the interlayer EPD forms an LbL structure mediated by positive APTES. The APTES - mediated EPD provides a weak electrostatic attraction for the continuous assembly of PS NP@APTES on the MPs, showing a slow decrease in Δf. Therefore, ΔD continuously increases, and a thick and uniform nano - coating is observed. Figure 3 k). Finally, in stage bIII, the EPD approaches zero, showing a slight decrease in Δf, indicating the formation of a stable LbL coating.

[0095] In phases bII and bIII, when assembling negatively charged NP@APTES, the Zeta potential of positively charged MP@poly(silsesquioxane) gradually decreases. As the number of nanocoating layers increases, the consumption of APTES molecules during the coating formation leads to a gradual decrease in the interlayer EPD (EPD N >EPD N+1 ). Since EPD N is greater than EPD N+1 , the electrostatic attraction between the nth layer of APTES and NP@APTES is greater than that on the (n + 1)th layer. Therefore, NP@APTES will spontaneously anchor on the nth layer rather than the (n + 1)th layer to construct a well-defined LbL structure around the MP core. Thus, the Zeta potential of MP with a nanocoating decreases over time but remains positive( Figure 3 g, the upper line).

[0096] In addition, the Zeta potential of NPs in the APTES dispersion system gradually increases over time. Positively charged APTES molecules continuously adsorb on negatively charged NPs to reduce the interlayer EPD between MPs and NPs( Figure 3 g, the lower line), and the trend is consistent with our LbL assembly model( Figure 3 b). It should be noted that depending on the specific surface area between MPs and NPs, 100 μL of APTES is the optimal choice to ensure that MPs are positively charged (metastable state) while keeping NPs negatively charged (stable state) for assembly. The composition of the formed nanocoating shell was studied by XPS at 10 h and 20 h respectively( Figure 3 h), showing an increase in nitrogen content, further verifying the assembly mechanism of decreasing EPD with the consumption of APTES over time. In the QCM test, when increasing the amount of APTES, the EPD between MPs and NPs is enhanced, thus increasing the assembly rate and showing a sharp decrease in Δf over time in phases bII - bIII( Figure 3 i).

[0097] Control experiments were carried out by characterizing two systems (NP / MP@poly(silsesquioxane) and NP / MP / APTES) through QCM tests to verify the mechanism of APTES-mediated assembly. In the case of NP / MP@poly(silsesquioxane), due to the electrostatic attraction between NPs and MP@poly(silsesquioxane), a single-layer nanocoating is formed around the MP core, and no LbL structure is formed. When NPs are dispersed onto the chip surface deposited with PS MP@poly(silsesquioxane), a decrease in Δf is observed within a few minutes( Figure 3 d), indicating the formation of a single-layer nanocoating in phase bI. The morphology of the single-layer nanocoating on the MP core was observed under SEM( Figure 3l). Compared with the previously introduced MP@poly(silsesquioxane) / NP / APTES system ( Figure 3 c), in the stage bII-bIII, Δf and the thickness of the nanocoating did not change with time ( Figure 3 m). The Zeta potential of MP@poly(silsesquioxane) / NP remained negatively charged. In fact, without APTES to mediate the EPD between MP and NP, there would be no driving force to attract MP and NP in the outermost layer, and the LbL structure could not be formed.

[0098] In the case of NP / MP / APTES, when NP and APTES were loaded onto the surface of the hip deposited with unmodified MP, no sharp drop in Δf was observed in the stage bI ( Figure 3 e). Instead, a smooth decrease in Δf with time was obtained, and no boundary distinguishing different stages was observed. Therefore, it was found by SEM that most NPs were sparsely deposited on MP ( Figure 3 n). Consistently, the thickness of the nanocoating hardly changed after 40 hours of incubation ( Figure 3 o). It is worth noting that without modifying the MP surface with an APTES-coated poly(silsesquioxane) network, the EPD mediated only by APTES suspended in the solution was not sufficient to construct the LbL structure, resulting in the inability to adsorb NPs around the MP core. By systematically characterizing NP / MP@poly(silsesquioxane) and NP / MP / APTES, it was found that the suspended APTES and the APTES-coated poly(silsesquioxane) network present on the MP surface were crucial for forming the LbL structure around the MP core and forming a well-defined multi-layer superstructure.

Claims

1. A method for preparing layered core-satellite particles, the method comprising: Contacting a charged microparticle comprising a first charge, a charged nanoparticle comprising a second charge, and a charged binding material selected from the group consisting of charged small molecules and charged polymers, wherein the charged small molecule or the charged polymer comprises a third charge in a solvent, whereby: (a) The charged binding material self-assembles on the surface of the charged microparticle, thereby forming a first self-assembled monolayer of charged binding material that comprises the charged binding material disposed on the surface of the charged microparticle; (b) The charged nanoparticle self-assembles on the surface of the first self-assembled monolayer of charged binding material, thereby forming a first self-assembled monolayer of charged nanoparticles that comprises the charged nanoparticles disposed on the surface of the first self-assembled monolayer of charged binding material; (c) The charged binding material optionally self-assembles on the first self-assembled monolayer of charged nanoparticles, thereby forming a second self-assembled monolayer of charged binding material that comprises the charged binding material disposed on the surface of the first self-assembled monolayer of charged nanoparticles; (d) The charged nanoparticle optionally self-assembles on the surface of the second self-assembled monolayer of charged binding material, thereby forming a second self-assembled monolayer of charged nanoparticles that comprises the charged nanoparticles disposed on the surface of the second self-assembled monolayer of charged binding material; and (e) Optionally repeat step (c) or repeat steps (c) and (d) one or more times; thereby forming the layered core-satellite particles, wherein both the first charge and the second charge are positively charged or negatively charged, the third charge is the opposite charge of the first charge and the second charge, and the average size of the charged microparticles is at least about 10 3 times larger.

2. The method of claim 1, wherein the method is carried out in a single step in a reaction vessel.

3. The method of claim 1, wherein the charged microparticle and the charged nanoparticle independently comprise charged silica, a metal oxide, or a polymer comprising at least one of a cationic functional group and an anionic functional group.

4. The method of claim 3, wherein the cationic functional group is selected from the group consisting of ammonium, iminium, guanidinium, phosphonium, sulfonium, imidazolium, thiazolium, pyrazolium, pyridinium, pyrrolidinium, piperidinium, pyridazinium, pyrazinium, and pyrimidinium; and the anionic functional group is selected from the group consisting of carboxylate, sulfate, and phosphate.

5. The method of claim 3, wherein the polymer comprises poly(dimethyldiallylammonium), poly(allylamine); poly(diallylmethylamine); poly(ethyleneimine), polyornithine, polyarginine, polylysine, protamine, chitosan, a protein, poly(styrenesulfonic acid), poly(styrenecarboxylic acid), poly(styrenephosphoric acid), poly(acrylic acid), poly(methacrylic acid), poly(vinylsulfonic acid), poly(vinylphosphoric acid), poly(itaconic acid), polyglutamic acid, alginic acid, dextran sulfate, hyaluronic acid, hydroxypropylmethylcellulose pectin, heparin, carrageenan, a polynucleic acid, a protein, or a charged dendrimer.

6. The method of claim 3, wherein the metal oxide is an oxide of a Group 3-16 metal.

7. The method of claim 1, wherein the charged small molecule is an alkylsilane comprising a cationic functional group or an anionic functional group.

8. The method according to claim 7, wherein the cationic functional group is selected from the group consisting of ammonium, iminium, guanidinium, phosphonium, sulfonium, imidazolium, thiazolium, pyrazolium, pyridinium, pyrrolidinium, piperidinium, pyridazinium, pyrazinium, and pyrimidinium; and the anionic functional group is selected from the group consisting of carboxylate, sulfate, sulfonate, phosphate, and phosphonate.

9. The method according to claim 7, wherein the alkylsilane has the formula Y(CR 1 2) m Si(R 2 )(OR 3 )2, where m is an integer selected from 1 - 10; Y is -COO - , -(P=O)(O - )2, -O(P=O)(O - )2, -(S=O)2O - , -O(S=O)2O - , -NR3 + , -SR2 + , -PR3 + , or a cationic heteroaryl, where R is independently hydrogen or alkyl in each case; R 1 is independently hydrogen or alkyl in each case; R 2 is alkyl or -OR 3 ; and R 3 is independently alkyl in each case; or two R 3 together with the oxygen to which they are bonded form a 5 - 6 membered heterocycle.

10. The method according to claim 7, wherein the alkylsilane has the formula NH3 + (CH2) m Si(R 2 )(OR 3 )2, where m is an integer selected from 1 - 10; R 2 is alkyl or -OR 3 ; and R 3 is independently alkyl in each case.

11. The method according to claim 9, wherein the alkylsilane undergoes a sol-gel reaction.

12. The method according to claim 1, wherein the charged fine particles and the charged nanoparticles are polymers containing sulfonate groups or -NR3 + and the charged small molecule is an alkylsilane having the formula NH3(CH2) m Si(OR 3 )3, where m is an integer selected from 1 to 10 and R 3 is independently an alkyl in each case; or the charged fine particles and the charged nanoparticles are negatively charged silica and the charged polymer contains -NR3 + , where R is independently hydrogen or an alkyl in each case.

13. The method according to claim 1, wherein the charged binding material is present in the solvent at a lower concentration of at least one tenth of the concentration of the charged fine particles or the charged nanoparticles. 3 ​ 14. The method according to claim 1, wherein the solvent is water.

15. The method according to claim 1, wherein the solvent is an oil continuous phase comprising one or more water-in-oil microdroplets, the water-in-oil microdroplets comprising the charged microparticles, the charged nanoparticles, the charged binding material, and water.

16. The method according to claim 15, wherein the one or more water-in-oil microdroplets are generated by a microfluidic device.

17. The method according to claim 1, wherein the charged microparticles and the charged nanoparticles are independently spheres, hollow, ellipsoidal, polyhedral, rod-shaped, plate-shaped, irregularly shaped, or a mixture thereof.

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