Design, synthesis and characterization of metallic nanoparticles for catalysis and sensing

Se llevará a cabo la fabricación y caracterización de nuevos materiales nanoestructurados basados en nanopartículas metálicas de oro, plata y paladio con propiedades bien definidas para su posterior aplicación en catálisis y detección.Levarase a cabo a fabricación e caracterización de novos materiais nanostructurados basados en nanopartículas metálicas de ouro, prata e paladio con propiedades ben definidas para a súa posterior aplicación en catálise e detección.We will carry out the fabrication and characterization of new nanomaterials based on gold, silver and palladium nanoparticles with properties for their applications in catalysis and detection

Light Scattering versus Plasmon Effects: Optical Transitions in Molecular Oxygen near a Metal Nanoparticle

The localized surface plasmon of a metal nanoparticle can influence the optical properties of a molecule in the plasmon field. In a previous study of molecular oxygen adjacent to nanodisks on a flat substrate, we showed that a plasmon field can increase the probability of the O₂(a¹Δ_g) → O₂(X³Σ_g^–) radiative transition at 1275 nm. For the present study, we set out to ascertain if metal nanoparticles suspended in a liquid solvent could likewise induce measurable plasmonic effects on optical transitions in oxygen. Metal nanoparticles were prepared with the intent of selectively perturbing the 765 nm O₂(X³Σ_g^–) → O₂(b¹Σ_g⁺) absorption transition. Because O₂(b¹Σ_g⁺) efficiently decays to O₂(a¹Δ_g), we used the spectrally distinct O₂(a¹Δ_g) → O₂(X³Σ_g^–) phosphorescent transition at 1275 nm to probe the potential plasmon effects at 765 nm. Although we indeed observed nanoparticle-mediated effects on the O₂(X³Σ_g^–) → O₂(b¹Σ_g⁺) transition, our present data are readily explained in terms of a nanoparticle-dependent change in the path length of light propagation through the sample. We modeled the latter using features of radiative transfer theory. As such, we cannot claim to observe a plasmonic effect on oxygen from these nanoparticles suspended in solution. Instead, our results point to the general importance of considering the effects of light scattering, certainly for experiments on suspended metal nanoparticles. Indeed, the extent to which light scattering can influence such optical experiments leads us to infer that many claims of a plasmonic effect could be misassigned

An expanded surface-enhanced raman scattering tags library by combinatorial rncapsulation of reporter molecules in metal nanoshells

Raman-encoded gold nanoparticles (NPs) have been widely employed as photostable multifunctional probes for sensing, bioimaging, multiplex diagnostics, and surfaceenhanced Raman scattering (SERS)-guided tumor therapy. We report a strategy toward obtaining a particularly large library of Au nanocapsules encoded with Raman codes defined by the combination of different thiol-free Raman reporters, encapsulated at defined molar ratios. The fabrication of SERS tags with tailored size and predefined codes is based on the in situ incorporation of Raman reporter molecules inside Au nanocapsules during their formation "via" galvanic replacement coupled to seeded growth on Ag NPs. The hole-free closedshell structure of the nanocapsules is confirmed by electron tomography. The unusually wide encoding possibilities of the obtained SERS tags are investigated by means of either wavenumber-based encoding or Raman frequency combined with signal intensity, leading to an outstanding performance as exemplified by 26 and 54 different codes, respectively. We additionally demonstrate that encoded nanocapsules can be readily bioconjugated with antibodies for applications such as SERS-based targeted cell imaging and phenotyping.Ministerio de Ciencia, Innovación y Universidades | Ref. MDM-2017-0720Ministerio de Economía, Industria y Competitividad | Ref. MAT2016-77809-RAgencia Estatal de Investigación | Ref. PID2019-108954RB-100Xunta de Galicia | Ref. ED431G 2019/07Fundación Ramón Areces | Ref. SERSforSAFETYResearch Foundation Flanders | Ref. G038116

Highly porous palladium nanodendrites : wet-chemical synthesis, electron tomography and catalytic activity

A simple procedure to obtain highly porous hydrophilic palladium nanodendrites in one-step is described. The synthetic strategy is based on the thermal reduction of a Pd precursor in the presence of a positively charged polyelectrolyte such as polyethylenimine (PEI). Advanced electron microscopy techniques combined with X-ray diffraction (XRD), thermogravimetry and BET analysis demonstrate the polycrystalline nature of the nanodendrites as well as their high porosity and active surface area, facilitating a better understanding of their unique morphology. Besides, catalytic studies performed using Raman scattering and UV-Vis spectroscopies revealed that the nanodendrites exhibit a superior performance as recyclable catalysts towards hydrogenation reaction compared to other noble metal nanoparticles

Galvanic Replacement Coupled to Seeded Growth as a Route for Shape-Controlled Synthesis of Plasmonic Nanorattles

Shape-controlled synthesis of metal nanoparticles (NPs) requires mechanistic understanding toward the development of modern nanoscience and nanotechnology. We demonstrate here an unconventional shape transformation of Au@Ag core–shell NPs (nanorods and nanocubes) into octahedral nanorattles via room-temperature galvanic replacement coupled with seeded growth. The corresponding morphological and chemical transformations were investigated in three dimensions, using state-of-the-art X-ray energy-dispersive spectroscopy (XEDS) tomography. The addition of a reducing agent (ascorbic acid) plays a key role in this unconventional mechanistic path, in which galvanic replacement is found to dominate initially when the shell is made of Ag, while seeded growth suppresses transmetalation when a composition of Au:Ag (∼60:40) is reached in the shell, as revealed by quantitative XEDS tomography. This work not only opens new avenues toward the shape control of hollow NPs beyond the morphology of sacrificial templates, but also expands our understanding of chemical transformations in nanoscale galvanic replacement reactions. The XEDS electron tomography study presented here can be generally applied to investigate a wide range of nanoscale morphological and chemical transformations

Plasmonic Au@Pd Nanorods with Boosted Refractive Index Susceptibility and SERS Efficiency: A Multifunctional Platform for Hydrogen Sensing and Monitoring of Catalytic Reactions

Palladium nanoparticles (NPs) have received tremendous attention over the years due to their high catalytic activity for various chemical reactions. However, unlike other noble metal nanoparticles such as Au and Ag NPs, they exhibit poor plasmonic properties with broad extinction spectra and less scattering efficiency, and thus limiting their applications in the field of plasmonics. Therefore, it has been challenging to integrate tunable and strong plasmonic properties into catalytic Pd nanoparticles. Here we show that plasmonic Au@Pd nanorods (NRs) with relatively narrow and remarkably tunable optical responses in the NIR region can be obtained by directional growth of Pd on penta-twinned Au NR seeds. We found the presence of bromide ions facilitates the stabilization of facets for the directional growth of Pd shell to obtain Au@Pd nanorods (NR) with controlled length scales. Interestingly, it turns out the Au NR supported Pd NRs exhibit much narrow extinction compared to pure Pd NRs, which makes them suitable for plasmonic sensing applications. Moreover, these nanostructures display, to the best of our knowledge, one of the highest ensemble refractive index sensitivity values reported to date (1067 nm per refractive index unit, RIU). Additionally, we showed the application of such plasmonic Au@Pd NRs for localized surface plasmon resonance (LSPR)-based sensing of hydrogen both in solution as well as on substrate. Finally, we demonstrate the integration of excellent plasmonic properties in catalytic palladium enables the <i>in situ</i> monitoring of a reaction progress by surface-enhanced Raman scattering. We postulate the proposed approach to boost the plasmonic properties of Pd nanoparticles will ignite the design of complex shaped plasmonic Pd NPs to be used in various plasmonic applications such as sensing and <i>in situ</i> monitoring of various chemical reactions