Microcapsules with macroholes prepared by the competitive adsorption of surfactants on emulsion droplet surfaces

Free-Standing Metal Films Prepared via Electroless Plating at Liquid-Liquid Interfaces

We report a simple preparation of free-standing metal films via electroless plating (ELP) at the liquid-liquid (L-L) interface between an aqueous electroless plating solution and an organic solvent. The use of ELP does not require any external energy in the form of heating and stirring. We find that the affinity of the organic solvent for the palladium nanoparticles (PdNPs) as catalysts and the vertical position of the organic and aqueous phases in the biphasic system are important considerations for synthesizing a robust copper film. Specifically, 1,2-dichloroethane which has an appropriate affinity for PdNPs and a higher density than water was found to be a good candidate for use as the organic phase in this system. However, a poor-quality copper film was obtained in the system with 1-hexanol as the organic phase. We also controlled the microscale surface structure of the copper films by using different concentrations of the injected PdNP dispersion. A high density of PdNPs caused smaller regions of metal growth, which contributed to the formation of smoother metal films. Moreover, under the optimal synthesis condition, we confirmed the electrical conductivity of the obtained copper film to be 1.16 × 10^-7 Ωm. We believe that this metal film preparation represents a promising way to produce a range of metal film structures through the use of flexible L-L interfaces as templates.

One-Step Synthesis of Cagelike Hollow Silica Spheres with Large Through-Holes for Macromolecule Delivery

A facile, one-step method to prepare cagelike hollow silica nanospheres with large through-holes (HSNLs) using a lysozyme-assisted O/W miniemulsion technique is presented. The tetraethoxysilane (TEOS)-xylene mixture forms oil droplets which are stabilized by the cationic surfactant cetyltrimethylammonium bromide (CTAB), cosurfactant hexadecane (HD), and protein lysozyme. HSNLs (with diameter of 300-460 nm) with large through-holes (10-30 nm) were obtained directly after ultrasonic treatment and aging. Lysozyme can not only stabilize the oil/water interface, assist the hydrolysis of TEOS, and interact with silica particles to assemble into silica-lysozyme clusters but also contribute to the formation of through-holes due to its hydrophilicity variation at different pH conditions. A possible new mechanism called the interface desorption method is proposed to explain the formation of the through-holes. To confirm the effectiveness of large through-holes in delivering large molecules, bovine serum albumin (BSA, 21 × 4 × 14 nm³) was chosen as a model guest molecule; HSNLs showed much higher loading capacity compared with common hollow mesoporous silica nanospheres (HMSNs). The release of BSA can be well controlled by wrapping HSNLs with a heat-sensitive phase change material (1-tetradecanol). Cell toxicity was also conducted with a Cell Counting Kit-8 (CCK-8) assay to roughly evaluate the feasibility of HSNLs in biomedical applications.

Syntheses and biomedical applications of hollow micro-/nano-spheres with large-through-holes

This review mainly discussed the syntheses and biomedical applications of hollow micro-/nano-spheres with large-through-holes in shells.

A Self-Assembling Octahedral Aggregate of Poly(methyl methacrylate) Nanospheres on a Silver Substrate

A large-area, self-assembling, octahedral aggregate composed of poly(methyl methacrylate) nanospheres (PMMA-NS) was constructed by using a one-step electrodeposition approach from an aqueous solution containing AgNO₃ and PMMA-NS as sacrificial electrolytes. The surface chain geometry of the product was revealed by Raman spectroscopy. The results revealed that the orientation of chains of the PMMA-NS octahedron is different from that of the nonaggregated PMMA-NS because of the interfacial interactions between the polymer chain and Ag metal. This can be explained by the crystal surface free energy of the octahedral Ag substrate, which gives rise to diverse conformations of the PMMA molecular chain at different surface regions of the silver substrate. In addition, the adsorptive properties of PMMA-NS octahedra are such that the adsorbent-adsorbate system is cost-effective, efficient and fast for the removal of dyes from contaminated wastewater.

Microfluidic preparation of polymer nanospheres

In this work, solid polymer nanospheres with their surface tailored for drug adhesion were prepared using a V-shaped microfluidic junction. The biocompatible polymer solutions were infused using two channels of the microfluidic junction which was also simultaneously fed with a volatile liquid, perfluorohexane using the other channel. The mechanism by which the nanospheres are generated is explained using high speed camera imaging. The polymer concentration (5-50 wt%) and flow rates of the feeds (50-300 µl min^-1) were important parameters in controlling the nanosphere diameter. The diameter of the polymer nanospheres was found to be in the range of 80-920 nm with a polydispersity index of 11-19 %. The interior structure and surfaces of the nanospheres prepared were studied using advanced microscopy and showed the presence of fine pores and cracks on surface which can be used as drug entrapment locations.

Advances in membrane emulsification. Part A: recent developments in processing aspects and microstructural design approaches

Modern emulsion processing technology is strongly influenced by the market demands for products that are microstructure-driven and possess precisely controlled properties. Novel cost-effective processing techniques, such as membrane emulsification, have been explored and customised in the search for better control over the microstructure, and subsequently the quality of the final product. Part A of this review reports on the state of the art in membrane emulsification techniques, focusing on novel membrane materials and proof of concept experimental set-ups. Engineering advantages and limitations of a range of membrane techniques are critically discussed and linked to a variety of simple and complex structures (e.g. foams, particulates, liposomes etc.) produced specifically using those techniques.

Preparation of monodisperse chitosan microcapsules with hollow structures using the SPG membrane emulsification technique

We describe herein successful preparations of monodisperse chitosan microcapsules with hollow structures using the SPG membrane emulsification technique. Two preparation procedures were examined in this study. In the first method, monodisperse calcium alginate microspheres were prepared and then coated with unmodified chitosan. Subsequently, tripolyphosphate treatment was conducted to physically cross-link chitosan and solubilize the alginate core at the same time. In the second method, photo-cross-linkable chitosan was coated onto the monodisperse calcium alginate microspheres, followed by UV irradiation to chemically cross-link the chitosan shell and tripolyphosphate treatment to solubilize the core. For both methods, it was determined that the average diameters of the chitosan microcapsules depended on those of the calcium alginate microparticles and that the microcapsules have hollow structures. In addition, the first physical cross-linking method using tripolyphosphate was found to be preferable to obtain the hollow structure, compared with the second method using chemical cross-linking by UV irradiation. This was because of the difference in the resistance to permeation of the solubilized alginate through the chitosan shell layers.