On the Size Evolution of Monolayer-Protected Gold Clusters during Ligand Place-Exchange Reactions: The Effect of Solvents

Facile Generation of Surface Diversity in Gold Nanoparticles

Surface chemistry is a key determinant of the physico-chemical and biological properties of gold nanoparticles (AuNPs). The introduction of chemical diversity in the surface of AuNPs is usually accomplished by place-exchange reactions using incoming ligands containing the desired terminal functional groups. As an alternative approach, we present here a simple, practical methodology to modify the surface of gold nanoparticles that allows the preparation of AuNPs stabilized with polyethyleneglycol (PEG) ligands with different surface chemistries using AuNPs stabilized with thiol-PEG-amino ligands as starting material. The surface modification reaction involves the acylation of the terminal amino groups in the ligand with an organic acid anhydride in an aqueous buffer. In addition to a full surface modification, this method also allows the synthesis of AuNPs with tailored mixed surfaces, containing two or more different functional groups, each of them at the desired extent. The ease of the experimental conditions for the reaction, purification, and for determining the level of surface modification makes this strategy an attractive alternative to current methods for the preparation of AuNPs with diverse surface chemistry.

Post-synthetic modification mechanism for 1D spin crossover coordination polymers

Suitable solvent os crucial to achieve a quantitative PSM reaction. Then, this method is not restricted to porous materials.

Janus Graphene Oxide Sheets with Fe3O4 Nanoparticles and Polydopamine as Anodes for Lithium-Ion Batteries

In this study, a one-step process to fabricate "Janus"-structured nanocomposites with iron oxide (Fe₃O₄) nanoparticles (Fe₃O₄ NPs) and polydopamine (PDA) on each side of a graphene oxide (GO) nanosheet using the Langmuir-Schaefer technique has been proposed. The Fe₃O₄ NPs-GO hybrid is used as a high-capacity active material, while PDA is added as a binder due to its unique wet-resistant adhesive property. The transmission electron microscopy image shows a superlattice-like out-of-plane section of the multilayered nanocomposite, which maximizes the density of the composite materials. Grazing-incidence small-angle X-ray scattering results combined with scanning electron microscopy images confirm that the multilayered Janus composite exhibits an in-plane hexagonal array structure of closely packed Fe₃O₄ NPs. This Janus multilayered structure is expected to maximize the amount of active material in a specific volume and reduce volume changes caused by the conversion reaction of Fe₃O₄ NPs. According to the electrochemical results, the Janus multilayer electrode delivers an excellent capacity of ∼903 mAh g^-1 at a current density of 200 mA g^-1 and a reversible capacity of ∼639 mAh g^-1 at 1 A g^-1 up to the 1800th cycle, indicating that this Janus composite can be a promising anode for Li-ion batteries.