Electrostatic force microscopy measurements of CdSe-PS nanoparticles and CdSe-PS/poly(styrene-b-butadiene-b-styrene) nanocomposites

Tailoring the in situ conformation of bacterial cellulose-graphene oxide spherical nanocarriers

Bacterial cellulose (BC)/graphene oxide (GO) sphere-like hydrogels have been biosynthesized by in situ route in dynamic cultivation. The GO concentration during BC biosynthesis (0.01 and 0.05 mg mL^-1) was the determining factor for the conformation of the final hydrogels: encapsulation (BC/GO 0.01) or distribution through all the body of the spheres (BC/GO 0.05). The as-prepared sphere hydrogels were characterized in terms of physico-chemical properties, thermal stability, microstructure, and swelling capacity in different media. In addition, a chemical treatment with ascorbic acid was performed in order to obtain reduced graphene oxide (rGO) into the spheres (BC/rGO). After the chemical treatment, electrostatic force microscopy (EFM) revealed electrical interactions due to the presence of rGO inside the spheres and resistivity values in the range of semiconductive materials were obtained (10⁶ Ω·cm), making BC/rGO spheres promising for the development of electro-stimulated systems. The in vitro release study of ibuprofen (IB), showed that the reduction process led to an increase of 73 and 92% of drug release with respect to BC/GO 0.05 and BC/GO 0.01 spheres, respectively. Moreover, the encapsulation conformation showed more homogeneous porous structure and thus, a cumulative drug release of 63% was reached after 6 h.

Segregation of Maghemite Nanoparticles within Symmetric Diblock Copolymer and Triblock Terpolymer Patterns under Solvent Vapor Annealing

Block copolymers (BCPs), through their self-assembly, provide an excellent guiding platform for precise controlled localization of maghemite nanoparticles (MNPs). Diblock copolymers (di/BCP) represent the most applied matrix to host filler components due to their morphological simplicity. A series of nanocomposites based on diblock copolymer or triblock terpolymer matrices and magnetic nanoparticles were prepared to study and compare the influence of an additional block into the BCP matrix. MNPs were grafted with low molecular weight polystyrene (PS) chains in order to be segregated in a specific phase of the matrix to induce selective localization. After the mixing of the BCPs with 10% w/v PS-g-MNPs, nanocomposite thin films were formed by spin coating. Solvent vapor annealing (SVA) enabled the PS-g-MNPs selective placement within the PS domains of the BCPs, as revealed by atomic force microscopy (AFM). The recorded images have proven that high amounts of functionalized MNPs can be controllably localized within the same block (PS), despite the architecture of the BCPs (AB vs. ABC). The adopted lamellar structure of the “neat” BCP thin films was maintained for MNPs loading approximately up to 10% w/v, while, for higher content, the BCP adopted lamellar morphology is partially disrupted, or even disappears for both AB and ABC architectures.

Synthesis and characterization of nanostructured PS-b-P4VP/Fe2O3 thin films with magnetic properties prepared by solvent vapor annealing

In this work hybrid organic/inorganic nanocomposites with magnetic properties, based on a PS-b-P4VP block copolymer and Fe₂O₃ maghemite nanoparticles have been prepared.