Hollow core-shell particles via NR latex seeded emulsion polymerization

Applications of hollow nanostructures in water treatment considering organic, inorganic, and bacterial pollutants

One of the major issues of modern society is water contamination with different organic, inorganic, and contaminants bacteria. Finding cost-effective and efficient materials and methods for water treatment and environment remediation is among the scientists' most important considerations. Hollow-structured nanomaterials, including hollow fiber membranes, hollow spheres, hollow nanoboxes, etc., have shown an exciting capability for wastewater refinement approaches, including membrane technology, adsorption, and photocatalytic procedure due to their extremely high specific surface area, high porosity, unique morphology, and low density. Diverse hollow nanostructures could potentially eliminate organic contaminants, including dyes, antibiotics, oil/water emulsions, pesticides, and other phenolic compounds, inorganic pollutants, such as heavy metal ions, salts, phosphate, bromate, and other ions, and bacteria contaminations. Here, a comprehensive overview of hollow nanostructures' fabrication and modification, water contaminant classification, and recent studies in the water treatment field using hollow-structured nanomaterials with a comparative attitude have been provided, indicating the privilege abd detriments of this class of nanomaterials. Eventually, the future outlook of employing hollow nanomaterials in water refinery systems and the upcoming challenges arising in scaling up are also propounded.

Shape-Tunable Hollow Polysiloxane Nanoparticles Based on a Surfactant-Free Soft Templating Method and Their Application as a Drug Carrier

A surfactant-free soft-templating method has been used to prepare polysiloxane hollow nanoparticles with a controllable shape. This method is simple and has the potential for large-scale preparation. For the first time, we successfully obtained hollow polysiloxane nanoparticles with different shapes, including eccentric hollow polysiloxane microspheres (EHPM), apple-like hollow polysiloxane microparticles (AHPM), and bowl-like hollow polysiloxane microparticles (BHPM), by simply changing the solvent. In this method, the hydrolyzed methyltriethoxysilane (MTES) not only stabilizes the system as a surfactant but also acts as a reactant for subsequent reactions, so no additional surfactant is needed. In addition, the formation mechanism of hollow polysiloxane microparticles with different shapes is also proposed: that is, MTES hydrolyzed under acidic conditions to form a surfactant, which changes the system from suspension to a stable oil-in-water emulsion. Then, under alkaline conditions, the hydrolyzed MTES polycondenses and nucleates at the oil-water interface. At the same time, with the process of polycondensation, the hydrolyzed MTES will migrate to the nucleation site driven by surface tension, thus forming an eccentric core/shell (solvent/polysiloxane) structure. Due to the different forces between hydrolyzed MTES and different solvents, the deviation degree of hollow in microspheres is different, thus forming particles with various morphologies. This synthesis method provides a new idea for the preparation of shapeable anisotropic hollow structures. Finally, we use AHPM to study the application of the drug load. The results show that the prepared hollow polysiloxane particles have a good drug loading capacity and release performance. It can be predicted that the shape-tunable hollow polysiloxane particles prepared by this method have broad application prospects in the field of drug delivery.

Surface Tension-Induced Eccentric Hollow Polysiloxane Microspheres in a Surfactant-Free System and Their Applications as a Nanoreactor and Nanomotor

Eccentric hollow polysiloxane microspheres (EHPMs) have attracted significant attention due to their potential in energy storage, drug delivery, and heterogeneous catalysis applications. However, their preparation pathways are often particularly complex. Therefore, it is critical to find a simple method for preparing EHPMs. In this study, a surfactant-free emulsification method is proposed to prepare EHPM. Under acidic conditions, methyl triethoxysilane (MTES) is hydrolyzed at the oil-water interface, with the hydrolyzed MTES demonstrating amphiphilic properties, and it could be anchored on the xylene surface to form an oil-in-water emulsion. The solution, when adjusted to alkaline, nucleated from a point at the oil-water interface. Driven by the surface tension, the hydrolyzed MTES migrated to the nucleation site with decreasing hydrophilicity. As a result, an EHPM formed. This process provides a simple, low cost, and environmentally friendly strategy for the preparation of EHPM, which demonstrated potential in catalytic and nanomotor applications.

Preparation of Polypropylene-Composite Particles by Dispersion Polymerization

Polypropylene (PP)/poly(benzyl methacrylate) (PBzMA) composite particles were prepared by dispersion polymerization of benzyl methacrylate (BzMA) in the presence of PP particles without a conventional dispersant. The polymerization process yielded a stable emulsion of composite particles with a "currant bun"-like morphology consisting of a PBzMA core and PP bumps, indicating that the PP particles operate as colloidal stabilizers. Conversely, when BzMA was replaced with styrene as the monomer, dispersion polymerization yielded a large amount of aggregates. Finally, a stable emulsion was formed by copolymerizing a small amount of methyl methacrylate (MMA) with styrene. This result suggested that PP must interact with a second polymer to prepare stable composite particles. The surfaces of the PP particles, which are highly hydrophilic due to their carboxyl groups, were involved in the attachment and stabilization of the polymer precipitated in the medium. A film prepared from the obtained PP/PBzMA composite particles was highly hydrophobic and strongly adhesive to a PP sheet.

Liquid Nanoparticles: Manipulating the Nucleation and Growth of Nanoscale Droplets

By manipulating the nucleation and growth of solid materials, the synthesis of various sophisticated nanostructures has been achieved. Similar methodology, if applied to liquids, could enable the mass-production and control of ultra-small droplets at the scale of nanoparticles (10^-18  L or below). It would be highly desirable since droplets play a fundamental role in numerous applications. Here we present a general strategy to synthesize and manipulate nanoscale droplets, similar to what has been done to solid nanoparticles in classic solution-synthesis. It was achieved by a solute-induced phase separation which initiates the nucleation of droplets from a homogeneous solution. These liquid nanoparticles have great potentials to be manipulated like their solid counterparts, borrowing from the vast methodologies of nanoparticle synthesis, such as burst nucleation, seeded growth, and co-precipitation. Liquid nanoparticles also serve as a general synthetic platform, to fabricate nanoreactors, drug-loaded carriers, and other hollow nanostructures with a variety of shell materials.

Well Defined Poly(Methyl Methacrylate)-Fe3O4/Poly(Vinyl Pivalate) Core-Shell Superparamagnetic Nanoparticles: Design and Evaluation of In Vitro Cytotoxicity Activity Against Cancer Cells

The objective of this work is to develop and characterize polymeric nanoparticles with core-shell morphology through miniemulsion polymerization combined with seeded emulsion polymerization, aiming at the application in the treatment of vascular tumors via intravascular embolization. The synthesis of the core-shell nanocomposites was divided into two main steps: (i) Formation of the core structure, consisting of poly(methyl methacrylate)/magnetic oxide coated with oleic acid (OM-OA) via miniemulsion and (ii) shell structure produced through seeded emulsion polymerization of vinyl pivalate. Nanocomposites containing about 8 wt.% of OM-OA showed high colloidal stability, mean diameter of 216.8 nm, spherical morphology, saturation magnetization (Ms) of 4.65 emu·g-1 (57.41 emu·g-1 of Fe3O4), preserved superparamagnetic behavior and glass transition temperature (Tg) of 111.8 °C. TEM micrographs confirmed the obtaining of uniformly dispersed magnetic nanoparticles in the PMMA and that the core-shell structure was obtained by seeded emulsion with Ms of 1.35 emu·g-1 (56.25 emu·g-1 of Fe3O4) and Tg of 114.7 °C. In vitro cytotoxicity assays against murine tumor of melanoma (B16F10) and human Keratinocytes (HaCaT) cell lines were carried out showing that the core-shell magnetic polymeric materials (a core, consisting of poly(methyl methacrylate)/Fe3O4 and, a shell, formed by poly(vinyl pivalate)) presented high cell viabilities for both murine melanoma tumor cell lines, B16F10, and human keratinocyte cells, HaCaT.

The controlled synthesis of complex hollow nanostructures and prospective applications†

Functionality in nanoengineered materials has been usually explored on structural and chemical compositional aspects of matter that exist in such solid materials. It is well known that the absence of solid matter is also relevant and the existence of voids confined in the nanostructure of certain particles is no exception. Indeed, over the past decades, there has been great interest in exploring hollow nanostructured materials that besides the properties recognized in the dense particles also provide empty spaces, in the sense of condensed matter absence, as an additional functionality to be explored. As such, the chemical synthesis of hollow nanostructures has been driven not only for tailoring the size and shape of particles with well-defined chemical composition, but also to achieve control on the type of hollowness that characterize such materials. This review describes the state of the art on late developments concerning the chemical synthesis of hollow nanostructures, providing a number of examples of materials obtained by distinct strategies. It will be apparent by reading this progress report that the absence of solid matter determines the functionality of hollow nanomaterials for several technological applications.

Preparation of Polyacrylate Hollow Microspheres via Facile Spray Drying

Polyacrylate microspheres with a hollow structure were prepared by a facile spray drying method. The effects of spray drying process parameters, including inlet temperature, atomizer rotational speed, and feed speed, on the particle size, bulk density, and morphology of the resultant polyacrylate hollow microspheres were investigated and discussed. The mechanism for the formation of the polyacrylate hollow microspheres was proposed. This facile and scalable method for preparing hollow polymer microspheres is expected to be valuable to prepare various polymer hollow structures for widespread application.

Hollow polymer nanocapsules: synthesis, properties, and applications

Hollow polymer nanocapsules (HPNs) have gained tremendous interest in recent years due to their numerous desirable properties compared to their solid counterparts.

Hollow polymer particles: a review

Herein, the basic principles, such as the definitions, classifications, and properties, of hollow polymer particles (HPPs) are critically investigated.