Radiation Induced Surface Modification of Nanoparticles and their Dispersion in the Polymer Matrix

Polymer grafted inorganic nanoparticles attract significant attention, but pose challenges because of the complexity. In this work, a facile strategy to the graft polymer onto the surface of nanoparticles have been introduced. The vinyl functionalized SiO2 nanoparticles (NPs) were first prepared by the surface modification of the unmodified SiO2 using γ-methacryloxy propyl-trimethoxylsilane. The NPs were then mixed with polyvinylidene fluoride (PVDF), which was followed by the Co-60 Gamma radiation at room temperature. PVDF molecular chains were chemically grafted onto the surface of SiO2 nanoparticles by the linking of the double bond on the NPs. The graft ratio of PVDF on SiO2 NPs surface can be precisely controlled by adjusting the absorbed dose and reactant feed ratio (maximum graft ratio was 31.3 wt%). The strategy is simple and it should be applied to the surface modification of many other nanoparticles. The prepared PVDF-grafted SiO2 NPs were then dispersed in the PVDF matrix to make the nanocomposites. It was found that the modified NPs can be precisely dispersed into the PVDF matrix, as compared with pristine silica. The filling content of modifications SiO2 NPs on the PVDF nanocomposites is almost doubled than the pristine SiO2 counterpart. Accordingly, the mechanical property of the nanocomposites is significantly improved.

Colloidal capsules: nano- and microcapsules with colloidal particle shells

This review provides a comprehensive overview of the synthesis strategies and the progress made so far of bringing colloidal capsules closer to technical and biomedical applications.

Surfactant Behavior of Amphiphilic Polymer-Tethered Nanoparticles

In recent years, an emerging research area has been the surfactant behavior of polymer-tethered nanoparticles. In this feature article, we have provided a general introduction to the synthesis, self-assembly, and interfacial activity of polymer-tethered inorganic nanoparticles, polymer-tethered organic nanoparticles, and polymer-tethered natural nanoparticles. In addition, applications of the polymer-tethered nanoparticles in colloidal and materials science are briefly reviewed. All research demonstrates that amphiphilic polymer-tethered nanoparticles exhibit surfactant behavior and can be used as elemental building blocks for the fabrication of advanced structures by the self-assembly approach. The polymer-tethered nanoparticles provide new opportunities to engineer materials and biomaterials possessing specific functionality and physical properties.

Polystyrene-Core-Silica-Shell Hybrid Particles Containing Gold and Magnetic Nanoparticles

Polystyrene-core-silica-shell hybrid particles were synthesized by combining the self-assembly of nanoparticles and the polymer with a silica coating strategy. The core-shell hybrid particles are composed of gold-nanoparticle-decorated polystyrene (PS-AuNP) colloids as the core and silica particles as the shell. PS-AuNP colloids were generated by the self-assembly of the PS-grafted AuNPs. The silica coating improved the thermal stability and dispersibility of the AuNPs. By removing the "free" PS of the core, hollow particles with a hydrophobic cage having a AuNP corona and an inert silica shell were obtained. Also, Fe3O4 nanoparticles were encapsulated in the core, which resulted in magnetic core-shell hybrid particles by the same strategy. These particles have potential applications in biomolecular separation and high-temperature catalysis and as nanoreactors.

Interface-directed self-assembly of gold nanoparticles and fabrication of hybrid hollow capsules by interfacial cross-linking polymerization

Amphiphilic gold nanoparticles (AuNPs) were produced at liquid-liquid interface via ligand exchange between hydrophilic AuNPs and disulfide-containing polymer chains. By using oil droplets as templates, hybrid hollow capsules with AuNPs on the surfaces were obtained after interfacial cross-linking polymerization. The volume ratio of toluene to water exerts an important effect on the size of capsules. The average size of the capsules increases with the volume ratio. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), and atomic force microscopy (AFM) were used to characterize the hollow structures. In this research, not only one-component but also multicomponent hollow capsules were prepared by copolymerization of acrylamide and hybrid AuNPs at liquid-liquid interface. Because of the improvement in hydrophilicity of the hollow capsules, the average size of multicomponent capsules is bigger than one-component ones in aqueous solution.

Hydrophobic gold nanoparticle self-assembly with phosphatidylcholine lipid: membrane-loaded and janus vesicles

Hybrids of hydrophobic sub-2-nm-diameter dodecanethiol-coated Au nanoparticles and phosphatidylcholine (PC) lipid vesicles made by extrusion were examined by cryogenic transmission electron microscopy (cryoTEM). The nanoparticles loaded the vesicles as a dense monolayer in the hydrophobic core of the lipid bilayer, without disrupting their structure. Nanoparticle-vesicle hybrids could also be made by a dialysis process, mixing preformed vesicles with detergent-stabilized nanoparticles, but this approach led to vesicles only partially loaded with nanoparticles that segregated into hemispherical domains, forming a Janus vesicle-nanoparticle hybrid structure.

Thermoresponsive nanohydrogels cross-linked by gold nanoparticles

Thermoresponsive nanohydrogels cross-linked by gold nanoparticles (AuNPs) were prepared by 1,3-dipolar cycloaddition reactions and in situ reversible addition-fragmentation chain-transfer (RAFT) polymerization. In order to synthesize thermoresponsive nanohydrogels, AuNPs decorated with azide groups (AuNPs-N(3)) were prepared through ligand exchange. Click reactions between AuNPs-N(3) and dialkynetrithiocarbonate yielded cross-linked AuNP aggregates. The size and cross-linking density of AuNP aggregates increased with the molar ratio of acetylene groups to azide groups. After click reactions, the absorption maximum of the plasmon band of AuNPs red-shifted to a long wavelength. Thermoresponsive nanohydrogels were prepared by in situ RAFT polymerization of N-isopropylacrylamide (NIPAM) using trithiocarbonate in the cross-linked AuNP aggregates as chain-transfer agents. The thermoresponsive nanohydrogels presented a low critical solution temperature at around 32 degrees C due to the "coil-to-globule" transition of connecting PNIPAM chains in the nanohydrogels. The size of the thermoresponsive nanohydrogels was determined by the molar ratio of acetylene groups to azide groups.

Self-assembly of gold nanoparticles and polystyrene: a highly versatile approach to the preparation of colloidal particles with polystyrene cores and gold nanoparticle coronae

Colloidal particles with polystyrene (PS) cores and gold nanoparticle (AuNP) coronae were prepared on the basis of the self-assembly of AuNP's and PS. Citrate-stabilized AuNP's were dispersed in aqueous solution, and PS with thiol terminal groups (PS-SH) was dissolved in toluene. A stable emulsion was obtained by mixing the two solutions. Optical microscope images indicate that after grafting of PS-SH to the citrate-stabilized AuNP's at liquid-liquid interface, the interfacial tension is reduced and the average size of toluene droplets in the emulsion decreases. Transmission electron microscope (TEM) results also prove the grafting of PS-SH to AuNP's and the location of the hybrid nanoparticles at the liquid-liquid interface. Colloidal particles with PS cores and AuNP coronae were prepared by adding the emulsion to excess methanol. The weight ratio of PS-SH to AuNP exerts a significant effect on the size of colloidal particles. TEM and dynamic light scattering results both indicate that the size of colloidal particles increases with the weight ratio. The application of the core-shell-structured colloidal particles to protein separation was also investigated in this research. Colloidal particles with PS-coated magnetic nanoparticles in the cores were also prepared by this strategy.