This paper unravels the role played by charge transfer to and from Ag nanoparticles in their plasmonic catalytic activities.

Hybrid materials in which reduced graphene oxide (rGO) is decorated with Au nanoparticles (rGO-Au NPs) were obtained by the in situ reduction of GO and AuCl4(-)(aq) by ascorbic acid. On laser excitation, rGO could be oxidized as a result of the surface plasmon resonance (SPR) excitation in the Au NPs, which generates activated O2 through the transfer of SPR-excited hot electrons to O2 molecules adsorbed from air. The SPR-mediated catalytic oxidation of p-aminothiophenol (PATP) to p,p'-dimercaptoazobenzene (DMAB) was then employed as a model reaction to probe the effect of rGO as a support for Au NPs on their SPR-mediated catalytic activities. The increased conversion of PATP to DMAB relative to individual Au NPs indicated that charge-transfer processes from rGO to Au took place and contributed to improved SPR-mediated activity. Since the transfer of electrons from Au to adsorbed O2 molecules is the crucial step for PATP oxidation, in addition to the SPR-excited hot electrons of Au NPs, the transfer of electrons from rGO to Au contributed to increasing the electron density of Au above the Fermi level and thus the Au-to-O2 charge-transfer process.

Nanomaterials properties are deeply dependent on several features, being easily tuned according to its composition, shape, and dimensionality. Graphene, a two-dimensional (2D) material has outstanding properties that may be tailored by turning its shape to 3D conformations, similar to crumpled paper ball-like structures. Thus, some drawbacks related to graphene restacking could be avoided, besides enlightening a way to explore the properties of graphene-based materials. Herein, we synthesize crumpled graphene structures fully decorated by manganese ferrite (MnFe2O4) nanoparticles in one single step. The samples were produced using an aerosol-assisted capillary compression process and the crumpled paper-ball-like shape of the composites could be adjusted to incorporate increasing amounts of manganese ferrite nanoparticles. We explored two different applications for the obtained materials: as an electrochemical sensor for hydrogen peroxide, and electrochemical supercapacitors. As a proof-of-concept, we synthesized bare manganese ferrite and a composite of flat rGO:MnFe2O4, which assisted us to certify that the best performance is related to the synergistic effect between components, the ratio between them, and the proper shape of the composite.

By ac ombination of theoretical and experimental design, we probed the effect of aq uasi-single electron on the surface plasmon resonance (SPR)-mediated catalytic activities of Ag nanoparticles.S pecifically,w es tarted by theoretically investigating how the E-field distribution around the surface of aAgnanosphere was influenced by static electric field induced by one,t wo,o rt hree extra fixede lectrons embedded in graphene oxide (GO) next to the Ag nanosphere.W ef ound that the presence of the extra electron(s) changed the E-field distributions and led to higher electric field intensities.T hen, we experimentally observed that aq uasi-single electron trapped at the interface between GO and Ag NPs in Ag NPs supported on graphene oxide (GO-Ag NPs) led to higher catalytic activities as compared to Ag and GO-Ag NPs without electrons trapped at the interface,r epresenting the first observation of catalytic enhancement promoted by aq uasisingle electron.