Poly(methyl methacrylate)/silica nanocomposite fibers by electrospinning

Comparison of AFM Nanoindentation and Gold Nanoparticle Embedding Techniques for Measuring the Properties of Polymer Thin Films

The surfaces of polymer and interfaces between polymer and inorganic particles are of particular importance for the properties of polymers and composites. However, the determination of the properties of surfaces and interfaces poses many challenges due to their extremely small dimensions. Herein, polystyrene and polymethyl methacrylate thin film on silicon wafer was used as a model system for the measurement of the properties of the polymer near free surface and at the polymer-solid interface. Two different methods, i.e., nanoindentation using atomic force microscopy (AFM) and the gold nanoparticle embedding technique, were used for these measurements. The results showed the elastic modulus of PS near the free surface determined by nanoindentation was lower than the bulk value. Based on contact mechanics analysis, nanoparticle embedding also revealed the existence of a lower-modulus, non-glassy layer near the free surface at temperatures below the bulk glass transition temperature (Tg). However, near the polymer-solid interface, the AFM nanoindentation method is not applicable due to the geometry confinement effect. On the other hand, the nanoparticle embedding technique can still correctly reflect the interactions between the polymer and the substrate when compared to the ellipsometry results.

Nanobead-on-string composites for tendon tissue engineering

The bead-on-string topography of electrospun nanocomposite scaffolds improves fibroblast response in terms of cell spreading and proliferation.

Synergistic effect of graphene and silicon dioxide hybrids through hydrogen bonding self-assembly in elastomer composites

A novel graphene–silicon dioxide hybrid (HGS) was prepared by plant polyphenol-tannic acid (TA) functionalized pristine graphene (G-TA) and primary amine-containing silane coupling agent modified SiO₂ (Si–NH₂). Through strong hydrogen-bonding interaction between the phenolic hydroxyl groups on G-TA and primary amine groups on Si–NH₂, SiO₂ was uniformly loaded to the surface of graphene. Due to the synergistic dispersion effect of graphene and SiO₂, which prevents restacking and re-aggregating of both graphene and SiO₂, HGS hybrids were distributed evenly in the natural rubber (NR) matrix (HGS@NR). Simultaneously, the surface roughness of graphene after loading SiO₂ and the interfacial interaction between the HGS hybrid and NR matrix were substantially improved. Due to the good dispersion and strong interface, the overall properties of HGS@NR nanocomposites are drastically enhanced compared with those of GS@NR nanocomposites prepared by dispersing the blend of unmodified graphene and SiO₂ (GS) in NR. The HGS@NR nanocomposites possess the highest tensile strength up to 27.8 MPa at 0.5 wt% and tear strength of 60.2 MPa at 0.5 wt%. Thermal conductivities of the HGS@NR nanocomposites were found to be 1.5-fold better than that of the GS@NR nanocomposites. Also, the HGS@NR nanocomposites exhibit excellent abrasive resistant capacity that is nearly 2-fold better than that of the GS@NR nanocomposites. These results suggest that HGS has great potential in high-performance nanocomposites and a new strategy of constructing the efficient graphene–SiO₂ hybrid fillers has been established.

A novel graphene–silicon dioxide hybrid (HGS) was prepared by plant polyphenol-tannic acid (TA) functionalized pristine graphene (G-TA) and primary amine-containing silane coupling agent modified SiO₂ (Si–NH₂).

Engineering of nanoparticle size via electrohydrodynamic jetting

Engineering the physical properties of particles, especially their size, is an important parameter in the fabrication of successful carrier systems for the delivery of therapeutics. Here, various routes were explored for the fabrication of particles in the nanosize regime. It was demonstrated that the use of a charged species and/or solvent with high dielectric constant can influence the size and distribution of particles, with the charged species having a greater effect on the size of the particles and the solvent a greater effect on the distribution of the particles. In addition to the fabrication of nanoparticles, their fractionation into specific size ranges using centrifugation was also investigated. The in vitro particle uptake and intracellular transport of these nanoparticles was studied as a function of size and incubation period. The highest level of intralysosomal localization was observed for the smallest nanoparticle group (average of 174 nm), followed by the groups with increasing sizes (averages of 378 and 575 nm), most likely due to the faster endosomal uptake of smaller particles. In addition, the internalization of nanoparticle clusters and number of nanoparticles per cell increased with longer incubation periods. This work establishes a technological approach to compartmentalized nanoparticles with defined sizes. This is especially important as relatively subtle differences in size can modulate cell uptake and determine intercellular fate. Future work will need to address the role of specific targeting ligands on cellular uptake and intracellular transport of compartmentalized nanoparticles.

Recent advances in electrospun metal-oxide nanofiber based interfaces for electrochemical biosensing

Synthesis of various electrospun metal-oxide nanofibers and their application towards electrochemical enzymatic and enzyme-free biosensor platforms has been critically discussed.

Hierarchically structured metal oxide/silica nanofibers by colloid electrospinning

We present herein a new concept for the preparation of nanofibrous metal oxides based on the simultaneous electrospinning of metal oxide precursors and silica nanoparticles. Precursor fibers are prepared by electrospinning silica nanoparticles (20 nm in diameter) dispersed in an aqueous solution of poly(acrylic acid) and metal salts. Upon calcination in air, the poly(acrylic acid) matrix is removed, the silica nanoparticles are cemented, and nanocrystalline metal oxide particles of 4-14 nm are nucleated at the surface of the silica nanoparticles. The obtained continuous silica fibers act as a structural framework for metal oxide nanoparticles and show improved mechanical integrity compared to the neat metal oxide fibers. The hierarchically nanostructured materials are promising for catalysis applications, as demonstrated by the successful degradation of a model dye in the presence of the fibers.

Facile and large-scale fabrication of anisometric particles from fibers synthesized by colloid-electrospinning

A new top-down approach is proposed to form large amounts of anisometric particles. Multicompartment fibers that present different domains composed of silica nanoparticles and larger polystyrene nanoparticles are fabricated by colloid-electrospinning and are subsequently calcinated and broken. The obtained fibers containing voids are subsequently cut via sonication to yield anisometric particles. It is shown that the majority of the fibers can be broken at the voids.

Controllable fabrication of soap-bubble-like structured polyacrylic acid nano-nets via electro-netting

Soap-bubble-like structured polyacrylic acid (PAA) nano-nets that comprise interlinked ultrathin nanowires with diameters of 10-35 nm are controllably prepared by a one-step electro-netting process.