Bowl-shaped Particles Research Articles

One-Step Preparation of Both Micron and Nanoparticles.

The complex materials comprised of both micron and nanometer-sized particles (MNPs) present special properties different from conventional single-size particles due to their special size effect. In this study, the MNPs could be simultaneously synthesized in a one-pot medium by soap-free emulsion polymerization, without harsh preparation conditions and material waste. In the whole process, the amphipathic siloxane oligomers would migrate to the mixed monomer droplet surface to reduce the surface energy of the system and further complete hydrolysis-condensation to obtain the SiO2 shell at the water-oil interface. On the one hand, the mixed monomers inside the above shell would migrate outward driven by the capillary force generated at the shell mesopore and be further initiated by the water-soluble initiator potassium persulfate (KPS), resulting in the formation of bowl-shaped micron particles with "lunar surface" structure. On the other hand, the residual mixed monomers dissolve in water and could be polymerized by initiating free radicals in the water phase to obtain popcorn-like nano-sized particles. The above two particles are clearly displayed in the SEM photos, and the DLS characterization further shows that the sizes of two particles are concentrated at 1.4 μm and 130 nm, respectively. Interestingly, the uniformity of obtained particles has a great relationship with the added amount of BA, and the perfect MNPs would appear when the St/BA feed mass ratio is 1:2. Moreover, the MNPs exhibit film-forming property, and the SiO2 component is evenly distributed in the formed coating. Thus, this study is not only beneficial to the theoretical research of soap-free emulsion polymerization but also to the application of multifunctional coatings.

Arrays of Bowl-Shaped Janus Particle Film with Structured Colors.

Structural colors generated via total internal reflection (TIR) using nanostructure-free micro-concave shapes have garnered increasing attention. However, the application of large micro-concave structures for structural coloration remains limited. Herein, a flexibly tunable structural color film fabricated by casting polydimethylsiloxane (PDMS) on an array of large poly(glycidyl methacrylate) (PGMA) bowl-shaped particles is reported. The resultant film exhibits tunable red to green structural colors with changing observation angles. Moreover, the color can be further tailored by altering the shape of the film itself. The incorporation of the PDMS layer not only facilitates a shift in the locus of TIR from the bottom surface to the top concave surface of the particles, thereby enabling the generation of structural color, but also confers enhanced flexibility to the film. Further decoration with silver nanoparticles imparts antimicrobial properties, yielding a novel antimicrobial coating material with structural colors. The simple and cost-effective strategy for the production of structural color films provides potential applications in antimicrobial coatings, enabling accessible and customizable structural coloration using big-size micro-concave particles.

Construction of Polysiloxane Induced Multilevel Bowl-shaped Janus Particles for Fabrication of Photoluminescent, Enhanced, Heat-insulative Poly(styrene-co-butyl acrylate) Latex Coating

Silica-based nanoparticles (SNPs) are highly regarded as advantageous nanofillers for composite coating, owing to their high surface area, robust mechanical properties, chemical stability, and adaptability for surface modification. Recent studies have unveiled the potential photoluminescence of SNPs induced by intrinsic defect sites, eliminating the need for additional fluorescein molecules. However, the inadequate quantum yield and complex preparation processes for generating defect sites within SNPs have constrained their broader applications. Herein, we propose a facile method to prepare Janus silicon-based nanoparticles with a hierarchical bowl-shaped structure (JHSNPs) through the emulsification of methyltriethoxysilane hydrolysis and condensation products, coupled with the capillary force during nanoparticle formation. The distinctive structure enhances the formation of dioxasilyrane (=Si(O2)) and silylene (=Si:) defects, thereby exhibiting strong blue photoluminescence. The JHSNPs then serve as nanofillers for commonly used poly(styrene-co-butyl acrylate) (SA) waterborne coatings, significantly enhancing their mechanical properties, abrasion resistance, and UV radiation resistance compared to the original SA coatings. Moreover, with just a 1% addition of JHSNPs, the composite coating exhibits visible fluorescence intensity, conferring the self-detecting monitoring properties for external scratches. Due to the hierarchical air-entrapping void structure, JHSNPs composite coatings demonstrate excellent thermal isolation performance, with a 22% reduction in thermal conductivity. The design of JHSNPs opens new avenues to expand the versatility of silica-based nanoparticles in composite coatings, especially in the optical, safety, and energy-saving fields.

Preparation of Hirudin-Loaded Chitosan/Polycaprolactone Bowl-Shaped Particles and an Application for a Drug Delivery System

Atherosclerosis, a disease that mainly affects human blood vessels, can cause various cerebral ischaemic diseases such as coronary heart disease and peripheral arterial disease. However, conventional drugs for the treatment of atherosclerosis have the disadvantages of low bioavailability and high toxicity. Bowl-shaped particles not only have the excellent properties of traditional spherical particles, such as improved drug distribution, increased drug absorption, reduced drug toxicity and side effects, but also are easier to circulate in the blood for a long time, have reduced immune rejection and have a larger specific surface area. Chitosan/polycaprolactone bowl-shaped particles were prepared via electrostatic spraying, and the effects of precursor solution concentration and polymer ratio on particle morphology were investigated. Chitosan/polycaprolactone composite bowl-shaped particles containing hirudin were prepared under optimal parameters for sustained anticoagulation. The anticoagulant molecules of hirudin could be continuously released from the composite scaffold as the bowl particles degraded. The biocompatibility and haemocompatibility of the composite particles were assessed using mouse glial cells and rabbit blood, and the results showed that the cell viability of the drug-loaded particles was overall above 90% and the haemolysis rate was below 2%. By controlling the release rate of hirudin, bowl-shaped particles can achieve a long-term anticoagulant drug delivery system and have wider application potential as a novel blood contact material.

Synthesis of bimetallic-nanocrystal-decorated rice bowl-shaped polymer particles for catalytic Cr(VI) remediation

Rice-bowl shaped polymer particles with convex and concave surfaces have emerged as promising noble metal catalyst supports. However, their synthesis and integration with catalytic materials using environmentally friendly methods have remained a challenge. This study presents a sustainable and efficient approach for synthesizing rice-bowl-shaped polystyrene (PS) particles and explores their potential as catalyst supports. The key to achieving this morphology lies in the utilization of anisotropic PS seeds, specifically hollow dimpled PS seeds. Uniform rice-bowl-shaped PS particles are obtained by dispersing these seeds in an oil-in-water (O/W) emulsion and allowing them to dry under ambient conditions. Non-toxic reducing agents and environmentally friendly solvents are employed for the in-situ chemical reduction process and galvanic displacement reaction to synthesize bimetallic (Ag/Pd) nanocrystals on the surfaces of the PS particles. The resulting Ag/Pd-coated PS particles exhibit excellent catalytic activity as microreactors for Cr(VI) reduction in water, while demonstrating remarkable stability during repeated use without significant loss of activity. Furthermore, the shape of the rice-bowl particles facilitates efficient packing and stacking, leading to enhanced catalytic performance not only in bulk solutions but also in confined spaces. This study highlights the potential of rice-bowl-shaped polymer particles as efficient and environmentally friendly catalyst supports, paving the way for the development of green catalytic applications.

Amphiphilic Bowl-Shaped Janus Particles Prepared via Thiol-Ene Click Reaction for Effective Oil-Water Separation.

Janus particles for oil-water separation have attracted widespread attention in recent years. Herein, we prepared a bowl-shaped Janus particle that could rapidly separate oil and water through a thiol-ene click reaction and selective etching. Firstly, snowman-like composite microspheres based on silica and mercaptopropyl polysilsesquioxane (SiO2@MPSQ) were prepared by a hydrolytic condensation reaction and phase separation, and the effects of the rotational speed and molar ratios on their microscopic morphologies were investigated. Subsequently, bowl-shaped Janus particles with convex hydrophilic and concave oleophilic surfaces were prepared via a thiol-ene click reaction followed by HF etching. Our amphiphilic bowl-shaped Janus particles could remarkably separate micro-sized oil droplets from an n-heptane-water emulsion with a separation efficiency of >98% within 300 s. Based on the experimental and theoretical results, we proposed the underlying mechanism for the coalescence of oil droplets upon the addition of the amphiphilic bowl-shaped Janus particles.

Fabrication of AgNPs@Bowl-shaped structure with excellent antibacterial activity

Bacterial infection has been attracted significant attention as it became an austere menace to public health systems. In this work, a novel thin-wall bowl-shaped particles (BSPs) were prepared by the solvent-induced phase separation method. Firstly, the copolymerization of methacrylic acid (MAA) and methyl methacrylate (MMA) were employed to synthesize amphipathic poly(methacrylic acid-co-methyl methacrylate) (PMA) chains in a solvent of EtOH/H2O. Secondly, hydrophobic hard monomer and hydrophilic soft monomer were introduced into the amphiphilic PMA solution to polymerize and assemble within polyvinylpyrrolidone (PVP) aqueous solution, which afforded a thin-wall BSPs. Its micromorphology and composition were characterized by SEM, FT-IR, TGA and DLS. Furthermore, Ag nanoparticles (AgNPs) were loaded to the surface of thin-wall BSPs through in situ reduction of silver ion (Ag+). Notably, the obtained Ag@BSPs exhibited excellent antibacterial properties against E. coli and S. aureus, which has enormous application prospects in the prevention and treatment of bacterial infections.

Large-scale synthesis of colloidal bowl-shaped particles.

We describe a general procedure for the large-scale fabrication of bowl-shaped colloidal particles using an emulsion templating technique. Following this method, single polymeric seed particles become located on individual oil droplet surfaces. The polymer phase is subsequently plasticized using an appropriate solvent. In this critical step, the compliant seed is deformed by surface tension, with the droplet serving as a templating surface. Solvent evaporation freezes the desired particle shape and the oil is subsequently removed by alcohol dissolution. The resulting uniformly-shaped colloidal particles were studied using scanning electron and optical microscopy. By adjusting the droplet size and the seed particle diameter, we demonstrate that the final particle shape can be controlled precisely, from shallow lenses to deep bowls. We also show that the colloid's uniformity and abundant quantity allowed the depletion-mediated assembly of flexible colloidal chains and clusters.

Polymerization in Shear Flow: From Bowl-Shaped Glyco-Microcarriers to Self-Propelled Micromotors.

We report a simple and effective method to synthesize composite bowl-shaped colloidal particles composed of a magnetic bottom and polymer wall. The bowl-shape is determined by the stirring and the resulting centrifugal force acting on the components during the synthesis. By systematically varying the stirring speed, we have found the lower and upper bounds for the bowl formation. Moreover, the size and thickness of the bowl can be tuned by changing the amount of the TPM monomer during synthesis. Functional groups can be easily introduced in the solidifying step through the polymerization of TPM by adding initiators and functional monomers. For example, by copolymerization of glycomonomer with TPM, bowl-shaped particles with biological activity can be obtained. In addition, such composite particles can be further modified to produce micromotors with well-controlled motions.

Hollow Multihole Carbon Bowls: A Stress-Release Structure Design for High-Stability and High-Volumetric-Capacity Potassium-Ion Batteries.

Potassium-ion batteries are potential alternatives to lithium-ion batteries for large-scale energy storage considering the low cost and high abundance of potassium. However, it is challenging to obtain stable electrode materials capable of undergoing long-term potassiation/depotassiation due to the high accumulated stress associated with the huge volume variation of the electrode. Here, we simulate the von Mises stress distributions of four different carbon three-dimensional models under an isotropic initial stress by the finite element method and reveal the critical role of the structure of a hollow multihole bowl on the strain-relaxation behavior. In this regard, nitrogen/oxygen codoped carbon hollow multihole bowls (CHMBs) are synthesized via hydrothermal carbonization coupled with an emulsion-templating strategy using biomass as the carbon source. Consistent with our simulation results, the CHMB anode remains stable for over 1000 cycles and delivers a high reversible capacity of 304 mAh g-1 at 0.1 A g-1. In addition to the reduced stress accumulation, the good electrochemical performances are also attributed to the surface capacitive mechanism and the shortened electron/ion transport distance in CHMBs. In particular, the CHMB composite electrode has a volumetric specific capacity 56% higher than that of hollow spheres due to the high tapped density of the bowl-shaped particles.

Revisiting the Classical Emulsion Polymerization: An Intriguing Occurrence of Monodispersed Bowl-Shaped Particles

An intriguing phenomenon is found that monodispersed bowl-shaped rather than spherical poly(styrene-co-butyl acrylate) [P(St-co-BA)] particles can be obtained by one pot traditional emulsion polymerization without using any template or redundant process and the cavity size is controllable. The facile implementation method is beneficial to large-scale fabrication of the bowl-shaped particles. Herein, the amphiphilic oligomeric radical with hydrophobic P(St-co-BA) chains and hydrophilic sulfate groups ([−OSO3]−) from water-soluble potassium persulfate could migrate to surface of primary latex particles to act as an emulsifier when amount of the additional emulsifier is so low, which causes an imbalance between inside and outside osmotic pressures of the latex particles to result in bowl-shaped particles for the kinetic stability. This advances the understanding of classical emulsion polymerization mechanism.

The interfacial photoreaction: an efficient strategy to create functional polymer particles

Functionalized colloidal particles are fascinating due to their huge range of potential and reported applications. In this focus review, the recent development of a novel “interfacial photoreaction” for the preparation of functional polymer particles is summarized. Recently, we discovered the phenomenon of the interfacial selective cross-linking of spherical polymer particles bearing photoreactive groups, and this reaction was successfully used to synthesize hollow polymer particles. As these hollow polymer particles have a cross-linked shell, solvent exchange can lead to the posteriori encapsulation of various molecules, yielding capsule particles. Functionalization of hollow/capsule particles was successfully achieved by introducing functional groups to the parent spherical polymer particles. In addition, the spatially controlled interfacial photoreaction enabled the formation of non-spherical bowl-shaped polymer particles. Furthermore, the photoinduced interfacial cross-linking strategy was successfully combined with molecular imprinting, and functional polymer particles with a molecular recognition capability were developed by utilizing the novel photoinduced post-cross-linked molecular imprinting method. We believe that photoinduced interfacial cross-linking will allow for the creation of new functional polymer particles suitable for a range of versatile applications. Functionalized colloidal particles are fascinating due to their huge range of potential and reported applications. In this focus review, the recent development of a novel “interfacial photoreaction” for the preparation of functional polymer particles is summarized. This approach allows for the direct fabrication of hollow, capsular, non-spherical polymer particles from spherical polymer particles. Furthermore, the ability of this approach to synthesize morphology controlled particles possessing sophisticated functions, such as stimuli responsiveness and molecular recognition capability, was also described in this paper.

10 Years of Soft Nanomaterials Research and Training at the Adolphe Merkle Institute

10 Years of Soft Nanomaterials Research and Training at the Adolphe Merkle Institute

Morphology control of shell-crosslinked polymer particles prepared by photo-induced shell-selective crosslinking approach via dispersed state control

HypothesisMorphology control of polymer particles is of great importance for creating functional particulate materials. Photoinduced shell-selective crosslinking approach with spherical polymer particles has been previously developed in a dispersed state, in which the polymer particles could rotate freely, yielding hollow polymer particles after removal of non-crosslinked polymers because photoinduced crosslinking occurred for the entire particle surface. This insight prompted the question of whether non-spherical particles can be obtained if particle rotation is restricted and photoirradiation occurs for only part of the shell region. ExperimentsHerein, we developed a facile approach for morphology control of polymer particles prepared by photoinduced shell-selective crosslinking of spherical polymer particles bearing photoreactive cinnamoyl groups by regulating the dispersed state. The morphology of the polymer particles obtained from the photo-induced shell-selective crosslinking approach in dispersed or non-dispersed states was confirmed. In-situ real time observation of forming the non-spherical polymer particles was also performed by optical microscope. FindingsHollow and bowl-shaped polymer particles were successfully obtained from same spherical polymer particles bearing photo-crosslinking groups in dispersed and non-dispersed states, respectively. The versatility of the approach was confirmed by using various comonomers. Furthermore, post-functionalization for the polymer particles was also successfully performed using functional groups derived from the comonomers.

Solvent Mixing To Induce Molecular Motor Aggregation into Bowl-Shaped Particles: Underlying Mechanism, Particle Nature, and Application To Control Motor Behavior.

Control over dynamic functions in larger assemblies is key to many molecular systems, ranging from responsive materials to molecular machines. Here we report a molecular motor that forms bowl-shaped particles in water and how confinement of the molecular motor affects rotary motion. Studying the aggregation process in a broader context, we provide evidence that, in the case of bowl-shaped particles, the structures are not the product of self-assembly, but a direct result of the mixing a good solvent and a (partial) non-solvent and highly independent of the molecular design. Under the influence of the non-solvent, droplets are formed, of which the exterior is hardened due to the increase in the glass transition temperature by the external medium, while the interior of the droplets remains plasticized by the solvent, resulting in the formation of stable bowl-shaped particles with a fluid interior, a glass-like exterior, and a very specific shape: dense spheres with a hole in their side. Applying this to a bulky first-generation molecular motor allowed us to change its isomerization behavior. Furthermore, the motor shows in situ photo-switchable aggregation-induced emission. Strong confinement prohibits the thermal helix inversion step while altering the energy barriers that determine the rotary motion, such that it introduces a reverse trans–cis isomerization upon heating. These studies show a remarkable control of forward and backward rotary motion by simply changing solvent ratios and extent of confinement.

Hollow porous bowl-shaped lithium-rich cathode material for lithium-ion batteries with exceptional rate capability and stability

Although lithium-rich layered composite cathode materials can meet the requirements of high discharge capacities and energy densities of lithium-ion batteries (LIBs), the drawbacks of encountering structural reconstruction, sharp voltage decay during cycling as well as low packing density still exist, which retard their further commercial development. This paper presents a novel approach to construct hollow porous bowl-shaped Li1.2Mn0.54Ni0.13Co0.13O2 (denoted as HPB-LMNCO) particles, which involves bowl-shaped carbonaceous particles as the predominant template and polyvinylpyrrolidone as an assistant soft template. One crucial step during the synthetic process is the controlled growth of metal ions with specific molar ratios in the bowl-shaped carbonaceous particles, and the key control parameter is the heating rate to ensure the prepared particles own the desired hollow porous bowl-shaped morphology. Of particular note is the desirable architecture which not only inherits the merits of hollow structures but also facilitates the tight particles packing. Owing to these advantages, utilizing this HPB-LMNCO as a cathode material manifests impressive rate capability and exceptional cycling stability at high rates with capacity retention of above 82% over 100 cycles. These results reveal that structural design of cathode materials play a pivotal role in developing high-performance LIBs.

Solvent On-Film Annealing (SOFA): Morphological Evolution of Polymer Particles on Polymer Films via Solvent Vapor Annealing

Over the past few decades, anisotropic polymer particles are of significant interest because of their unique properties which can be applied in various areas, such as drug delivery, biotechnology, and electronics. Most approaches to synthesize anisotropic polymer particles, however, are complicated, and the three-dimensional shapes of the anisotropic particles are usually difficult to be controlled. In this work, we develop a solvent on-film annealing (SOFA) method to fabricate anisotropic polymer particles by studying the morphological evolution of polystyrene (PS) microspheres on poly(methyl methacrylate) (PMMA) films annealed in toluene vapor. At different annealing stages, the isotropic PS microspheres gradually transform to anisotropic PS particles with different morphologies, such as UFO-, cymbal-, peanut-, and bowl-shaped particles. The morphology evolution is driven by the surface and interfacial tensions during the annealing processes and can be confirmed by a selective removal technique. Acetic ...

Anisotropic responsive microgels with tuneable shape and interactions.

Highly monodisperse polystyrene/poly(N-isopropylmethacrylamide) (PS-PNIPMAM) core-shell composite microgels were synthesized and further nanoengineered in either ellipsoidal, faceted or bowl-shaped particles. Beside their anisotropy in shape, the microgel design enables an exquisite control of the particle conformation, size and interactions from swollen and hydrophilic to collapsed and hydrophobic using temperature as an external control variable. The post-processing procedures and the characterization of the different particles are first presented. Their potential as model systems for the investigation of the effects of anisotropic shape and interactions on the phase behavior is further demonstrated. Finally, the self-assembly of bowl-shaped composite microgel particles is discussed, where the temperature and an external AC electric field are employed to control the interactions from repulsive to attractive and from soft repulsive to dipolar, respectively.

Growth of Semimetals Bismuth and Antimony Films on Reactive Substrate

Semimetal Bi and Sb thin films with novel hierarchical structures were synthesized on zinc substrate via a hydrothermal method. X‐ray diffraction (XRD) analysis confirmed the formation of pure semimetals Bi and Sb. Scanning electron microscopy images showed that Bi films constructed with microtube arrays and hierarchical microspheres can be obtained selectively by altering the concentration of Bi3+ ions. The synthesized Sb films were constructed with bowl‐shaped particles. The growth process of these semimetal architectures was briefly discussed.

A novel chemical synthesis of bowl-shaped polypyrrole particles

This paper describes a novel approach for chemical polymerization procedure of bowl-shaped polypyrrole (PPy) particles using ferric chloride as oxidant and iodine as dopant. The bowl-shaped PPy particles can be easily synthesized by adding N-methylpyrrole (NMPy) in pyrrole solution. Analyzed by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectrometer (XPS) and differential scanning calorimetry (DSC), the bowl-shaped PPy particles were revealed as a circular opening and hemispherical profile morphology. The results suggested that poly(N-methylpyrrole) (PNMPy) was present in the bowl-shaped PPy particles and interacted with PPy molecules during polymerization process. The as-prepared bowl-shaped PPy particles showed potential applications in drug delivery and catalyst supports.