Synthesis of iron oxide nanoparticles in a polyimide matrix

Microstructure and photocatalytic properties of polyimide/heterostructured NiO–Fe2O3–ZnO nanocomposite films via an ion-exchange technique

An innovative photocatalytic PI/heterostructured NiO–Fe₂O₃–ZnO nanocomposite was proposed.

Universal route to fabricate facile and flexible micro-supercapacitors with gold-coated silver electrodes

For the first time, a facile, cost-effective and universal route to fabricate the flexible Ag@Au MSCs was proposed. Au protective layer improves the performances of MSCs. This technique combines surface ion-exchange process with immersion plating.

Preparation and magnetic and thermal properties of flexible polyimide films with iron nitrophthalocyanine-coated magnetite microspheres

To effectively utilize the one-step solvent–thermal route to prepare iron (Fe)–nitrophthalocyanine/magnetite (Fe3O4) hybrid microspheres, we have developed a novel series of flexible Fe3O4/Fe-phthalocyanine (FePc)/polyimide (PI) composite films with various Fe3O4/FePc nanoparticle loadings (15, 27, and 40 wt%) and imidized at different temperatures (200°C and 300°C). The morphology and structure of the composite films were monitored using scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction, and the hybrid microspheres were found uniformly dispersed in the polymer matrices without any agglomeration. Mechanical and thermal properties of the composites were also investigated. The observed results indicated enhanced thermal stabilities, dramatically increased tensile modulus, and increased glass transition temperatures of the composite films, with the increment in the content of inorganic nanoparticles. Besides that, the Fe3O4/FePc/PI magnetic films showed higher saturation magnetization (24.33 emu g−1, 27 wt% Fe3O4/FePc loading) with high-temperature treatment compared with that of the Fe3O4/PI film (18.79 emu g−1, 27 wt% Fe3O4 loading). It proved to be an effective way to prevent Fe3O4 nanoparticles from oxidizing by coating the nanoparticles with organic layer. The flexible composite films can easily be moved under a relatively low magnetic field, indicating them to be the high-performance absorbing materials in potential applications.

One step continuous hydrothermal synthesis of very fine stabilized superparamagnetic nanoparticles of magnetite

Stable suspensions of citrated SPIO nanoparticles were synthesised in one step using a hydrothermal continuous process. Citrates control the crystallite size and the oxidation degree of metallic ions despite the very short reaction time (4 s). Magnetite particles, Fe(2.94)O(4), with an average size of 4 nm and good monodispersity were obtained.

Synthesis of iron nanoparticles via chemical reduction with palladium ion seeds

We report on the synthesis of highly monodisperse iron nanoparticles, using a chemical reduction method. Iron nanoparticles with an average diameter of 6 nm and a geometric standard deviation of 1.3 were synthesized at a pH of 9.50 from ferric chloride precursor with sodium borohydride as the reducing agent, polyacrylic acid as the dispersing agent, and palladium ions as seeds for iron nanoparticle nucleation. The resulting nanoparticles were ferromagnetic at 5 K and superparamagnetic at 350 K. The dispersing agent polyacrylic acid (PAA) was shown to prevent iron nanoparticles and possibly palladium clusters from aggregating; in the absence of PAA, only aggregated iron nanoparticles were obtained. The addition of palladium ions decreased the diameter of iron nanoparticles presumably by providing sites for heterogeneous nucleation onto palladium clusters. In the absence of palladium ions, the mean diameter of iron nanoparticles was approximately 110 nm and the standard deviation increased to 2.0. The pH of the solution also was found to have a significant effect on the particle diameter, likely by affecting PAA ionization and altering the conformation of the polymer chains. At lower pH (8.75), the PAA is less ionized and its ability to disperse palladium clusters is reduced, so the number of palladium seeds decreases. Therefore, the resulting iron nanoparticles were larger, 59 nm in diameter, versus 6 nm for nanoparticles formed at a pH of 9.50.

Co–Pt alloy nanoparticles produced using a template of nanoparticle array

A monolayer of Co-Pt alloy nanoparticles in the nanometer-size regime was fabricated using a nanotemplate approach. 1.7-nm-thick Co46Pt54 film was deposited onto a preexisting array of Ni seed particles embedded in a polyimide film. During subsequent annealing, the deposited Co46Pt54 film coalesced onto the seed particles to produce a monolayer of Co-Pt alloy particles. Deposition and annealing were repeated to increase both average particle size and volume fraction of the alloy particles. It was also shown that the annealing temperature was critical in controlling the particle size distribution and the final composition of the nanoparticles. This method of forming a single layer of vertically aligned nanoparticles can be easily extended to a large area as well as to produce a different combination of alloy particles on a polymer film.

Mono-layer of Ni(100-x)Fe(x) nanoparticles fabricated on a polyimide film under different curing atmospheres

A mono-layer of nano-sized metal particles was prepared on the surface of a polyimide film by simply depositing a thin film of Ni80Fe20 on top of the polyamic acid that was spin coated onto a Si wafer. During thermal imidization of the polyamic acid film, Fe was selectively etched by reacting with the carbonyl group of the polyamic acid to leave behind uniformly distributed Ni-rich metallic particles. The average diameter of the particles was 4 nm and the particles were confined into a single layer on top of the polymer film. Moreover, it was also shown that the morphology of the nanoparticles can be substantially altered by curing the precursor film in a hydrogen atmosphere, without significantly damaging the polymer film. Thus produced nanoparticles lay exposed on top of the electrically insulating and chemically stable polymer film so that it is possible that the nanoparticles can be directly used for fabricating a nonvolatile flash memory device or as a template for building functional nano-structures.

Nanoparticles fabricated by selective reaction of Fe100−xPtx alloy films during imidization of polyamic acid

Nanoparticles with different morphology and composition were fabricated inside a polyimide (PI) matrix based on selectively oxidizing a layer of Fe(100-x)Pt(x) alloy metal film sandwiched between two PI precursor layers. Gamma-Fe2O3, Pt, and Fe3Pt nanoparticles were formed in a monolayer between two PI layers, depending on the alloy film composition and curing conditions. These particles were well-crystallized and sized between 4 and 10 nm. X-ray photoelectron spectroscopy confirmed that Fe in the film preferentially reacted with the organic matrix whereas Pt remained metallic throughout the curing process, which enabled fabrication of particles different morphology and composition. This process can be easily extended to other alloy films, which provides an opportunity to fabricate nanoparticles relatively easily with desired composition and morphology embedded in an inert organic matrix.