Time Dependence and Signs of the Shift of the Surface Plasmon Resonance Frequency in Nanocages Elucidate the Nanocatalysis Mechanism in Hollow Nanoparticles

Abstract

Surface plasmon resonance (SPR) wavelength of plasmonic nanoparticles is sensitive to changes in the dielectric function of its exposed surface to the medium. Gold nanocages (AuNCs) have two surfaces (inner and outer) and thus two plasmon fields., When the dielectric of the medium changes around the outer surface only, the SPR shifts to different extent from that observed when the dielectric constant of the medium changes around both surfaces. This property of plasmonic AuNCs was used to elucidate the mechanism of the catalytic reduction of 4-nitro to 4-amino phenol, whether it is occurring within the cavity or on the exterior surface of the nanocages. For this purpose two types of nanocages were prepared, one with two plasmonic surfaces and the other with Au/Pt shell-shell nanocages, where only the external surface is plasmonic as gold is outside and Pt is inside. By following the time dependence of the plasmonic band shift resulting from the addition of the reactants and comparing the reaction kinetic parameters for two types of nanocages with those of the pure single metallic nanocages, it was concluded that the catalysis is taking place within the cavity in both types of hollow nanoparticles.

Hollow metal nanostructures for enhanced plasmonics: synthesis, local plasmonic properties and applications

“…Another field of application where hollow nanostructures perform better than their solid counterparts is catalysis [14,93,111,184,194,[228][229][230][231][232]. It should be noted here that the Pt-or Pd-based nanostructures have better catalytic activity or the addition of these elements to the AuAg nanostructures increase their catalytic activity, yet they have poor plasmonic properties [14,93,111,194,224,226].…”

“…It should be noted here that the Pt-or Pd-based nanostructures have better catalytic activity or the addition of these elements to the AuAg nanostructures increase their catalytic activity, yet they have poor plasmonic properties [14,93,111,194,224,226]. In the following, we focus on the application of plasmonic, Au-based hollow catalysts.…”

“…Wu et al [232] studied the catalytic activity of different AgAu bimetallic hollow nanoshells and solid nanoparticles and reported that the hollow nanostructures exhibit higher catalytic activity than the solid nanoparticles even though solid nanoparticles have higher Au content, indicating the dominant effect of the morphology for the catalysis. El-Sayed and co-workers [184,194,224,226] reported that enhanced catalytic activity of the hollow nanostructures can be attributed to the so-called nanocage effect, where the catalytic reaction takes place inside the nanocage. Figure 9B shows the schematic representation of a photocatalytic reaction that takes place inside the nanocage [184].…”

Bottom-Up Synthesis of Gold Octahedra with Tailorable Hollow Features

“…(1,2) The ability to control the dimensions of the hollow cavities within such noble metal nanoparticles allows for tailorable control of these unique plasmonic, catalytic, and electronic properties. (3)(4)(5)(6)(7)(8)(9) Consequently, hollow nanostructures have been used in numerous applications, functioning as nanoscale reactors for chemical reactions, (6)(7)(8) capsules for material containment, (10) substrates for generating surface-enhanced Raman scattering, (11)(12)(13) and for a variety of biomedical applications. (14)(15)(16)(17) While there are many methods for generating nanostructures with hollow interiors, (1,2) the vast majority of these procedures require a synthetic step where a sacrificial material is removed to generate the hollow features, as is the case for reactions based on galvanic replacements (18) and selective etchings.…”

Engineering of Au/Ag Nanostructures for Enhanced Electrochemical Performance

“…35,36 Moreover, the electron transport process is directly influenced by the level of how well the electrocatalysts are protected and consequently how accessible the catalytic sites are during the electrochemical measurements. 34,37 As such, the degree of ligand passivation on the nanostructure surface provides another rational for the proportional increase in measured peak current from using the Au NPs to transitioning to the Au/Ag NB and NC morphologies as shown in Fig. 2a.…”