Metal nanoclusters stabilized by pH-responsive microgels: Preparation and evaluation of their catalytic potential

Microgels as Soluble Scaffolds for the Preparation of Noble Metal Nanoparticles Supported on Nanostructured Metal Oxides

“…Transmission electron microscopy (TEM) analysis of the samples (see, e.g., Figure ) confirmed the data obtained from XRD and also pointed out that the noble metal/metal oxide NPs after calcination exhibited a rather broad size distribution and significant aggregation. It needs to be recalled that results previously obtained in the generation of Pd or Au NPs inside microgels − generally indicate the production of more monodisperse NPs in the range 3–5 nm. Indeed, the determination of the average size and size distribution of Pd NPs inside microgel MG2 (Figure S2) as well as inside composites before calcination confirmed that the NPs before calcination are much more monodisperse and in the size range 5–10 nm, irrespective of their generation before (Figure , top left) or after (Figure , top right) the formation of the metal oxide inside the microgel.…”

“…Methyl methacrylate was employed as a nonfunctional comonomer and ethylene dimethacrylate as a cross-linker (Table ). The microgels were synthesized by our well-established radical polymerization in dilute solution, , using N , N -dimethylformamide (DMF) as the solvent (Scheme ), and conveniently isolated by precipitation in diethyl ether.…”

“…Having established the possibility to produce crystalline inorganic oxide samples by this mean, we then investigated on the production of ternary microgels featuring both an inorganic oxide phase and noble metal NPs. As mentioned in Introduction, noble metal NPs can be conveniently generated inside microgels by anchoring suitable metal precursors, followed by chemical reduction (Scheme , second reaction). − In principle, the generation of the noble metal NPs can precede or follow the anchoring of the metal oxide precursors and the consequent formation of the metal oxide phase within the microgel by hydrolysis. The preference for either approach depends on the need for the intermediate isolation of the hybrid microgel containing the noble metal NPs.…”

“…We have a long-standing experience in the chemistry of functional micro- and nanogels, in particular, on their use as soluble scaffolds for the production of hybrid colloids containing noble metal nanoparticles (NPs) to be used as quasi-homogeneous catalysts. − Together with other groups, we have pioneered the preparation of these colloids by exploiting the functional groups contained in the microgel to anchor simple metal salts or complexes as precursors, which are subsequently reduced to produce metal NPs within the microgel; in particular, our group was the first to demonstrate that using this strategy it was possible to tailor the final average size of the metal nanoparticles by acting on the morphology of the microgel scaffold through the cross-linking degree . In principle, a similar strategy can also be employed for generating other kinds of inorganic components, possibly with the same degree of control on the morphology of the inorganic phase.…”

Synthesis and Characterization of Tunable, pH-Responsive Nanoparticle–Microgel Composites for Surface-Enhanced Raman Scattering Detection

“…Enthalpic penalties associated with exposure of PS segments to water are reflected in the overall p K a of the microgel. Utilizing hydrophobic PS content for tuning the pH-responsive properties of pyridinyl groups in microgels represents a novel method and one that may allow for better matching of the conditions and specificity needed for various applications such as pH-reporting, , catalysis, − and molecular detection via SERS. , …”