Pd Nanoparticles/Au@SiO₂ Core–Shell Nanostructures for Hydrogen Sensing

Abstract

Herein, a multistep synthesis method was implemented to prepare nanoscale core@shell spherical heterostructures for H2 optical detection. The resulting nanoheterostructures are built with gold cores and silica shells further coated by a thin layer of spherical palladium nanoparticles. Samples with various thicknesses of silica and densities of palladium nanoparticles were synthesized and characterized by transmission electron microscopy. In particular, the three-dimensional core@shell configuration was confirmed by electron tomography. The optical properties of the obtained nanostructures were first analyzed by optical absorbance measurements, and their potential use for H2 detection was evaluated by simulations based on the discrete dipole approximation method. Thus, the optical response of the studied nanostructures is investigated theoretically when the Pd layer is hydrogenated, showing the great sensitivity achievable with these nanostructures.

Synergy Between LSPR and Energy Transfer in Ultrasmall Au Nanoclusters Stabilized on Plasmonic Ag@SiO2 Nanoantenna Supports: Implication for Photocatalysis

“…The Ag NTs show two SPR peaks, with an intense peak at 627 nm from in-plane dipole oscillation and a weak shoulder at 418 nm due to in-plane quadruple oscillation. ,, However, the peak at 340 nm is due to out-plane-dipole oscillations. − These features are commonly observed in metal nanotriangles. Subsequent functionalization with 16-MHA and silica coating showed a redshift in the plasmonic peak due to a change in the refractive index or dielectric environment around the Ag NTs. ,− As expected, the magnitude of the redshift increases with an increase in the thickness of dielectric SiO 2 . Generally, this high dielectric SiO 2 can affect the frequency of plasmonic oscillations; accordingly, the SPR peak shifts in the absorption spectra.…”

“…Ultrafine nanoclusters, which consist of a few atoms, have garnered considerable attention across various scientific and technological disciplines due to their exceptional physical and chemical characteristics. − Among the diverse range, gold nanoclusters (Au NCs) have emerged as a prominent area of research in recent years. Their distinctive size, composition, and remarkable physicochemical properties make them highly suitable for bioimaging, sensing, and catalytic applications. − In particular, the synthesis of thiol-capped Au NCs in recent years has gained significant momentum in photocatalysis applications owing to their intriguing optical properties. − However, one major drawback is their low stability due to their unique sizes. ,− The stability, usually affected by factors such as the geometry and shell, is critical to their applications. To address this limitation, various groups have focused on strategies such as rigidifying cluster shells by encapsulating in polymer, inducing aggregation, or using metal oxide or mesoporous supports to stabilize and reduce the nonradiative relaxation process, which has shown promise in increasing its stability and quantum yield. − For instance, Ziarati et al demonstrated the role of graphene as support in enhancing the stability of Au clusters.…”

“…Plasmonic metal nanoparticles, typically composed of noble metals like gold or silver, exhibit localized surface plasmon resonance (LSPR)the collective oscillation of free electrons in the metal nanoparticles when excited by incident lightthat gives rise to their distinctive optical behavior. ,− The optical properties of these nanoparticles are predominantly determined by their size, shape, composition, and local environment. , These enable efficient excitation of collective electron oscillations and tunability of the resonance frequency to tailor the nanoparticles’ optical properties for specific applications. ,− The impact of plasmonic particles on the optical properties of Au NCs remains unclear. − While some studies have reported an increase in photoluminescence (PL) intensity, indicating enhancement, others have observed a combination of both enhancement and quenching effects. For instance, Zhao et al demonstrated a plasmonic-enhanced photoelectrochemical biosensor utilizing Au NCs, where the distance between Au NCs-decorated Ag@SiO 2 nanocomposites played a crucial role in enhancing the photocurrent of Au NCs.…”

Lattice-Expanded PdAg Spatial Nanodendrites as Catalysts for the Ethanol Oxidation Reaction

“…The study found that the nanocrystal assembly structure, which is characterized by high porosity and lattice expansion due to the introduction of silver elements, significantly enhances the electrocatalytic activity and stability. 46,47 Under the appropriate catalytic reaction temperature and with the right concentrations of OH − and C 2 H 5 OH, the electrocatalytic conditions promote the EOR process. 30,48,49 Figure 6a delineates the influence of Pd 9 Ag 1 NDs on the current density across a spectrum of catalytic temperatures, concomitant with the modulation of KOH/C 2 H 5 OH concentration from 0.1 to 1.0 mol/L.…”

“…The results of long-term CV tests revealed that the Pd 9 Ag 1 NDs maintained 43% MA after 500 potentiation cycles. The study found that the nanocrystal assembly structure, which is characterized by high porosity and lattice expansion due to the introduction of silver elements, significantly enhances the electrocatalytic activity and stability. , …”