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There is significant interest in earth-abundant plasmonic materials, but whether or not their performance can match or even surpass their noble metal counterparts remains to be established. An impo...

Catalytic and optical properties can be coupled by combining different metals into nanoscale architectures in which both the shape and the composition provide fine-tuning of functionality. Here, discrete, small Pt nanoparticles (diameter = 3-6 nm) were grown in linear arrays on Au nanoprisms, and the resulting structures are shown to retain strong localized surface plasmon resonances. Multidimensional electron microscopy and spectroscopy techniques (energy-dispersive X-ray spectroscopy, electron tomography, and electron energy-loss spectroscopy) were used to unravel their local composition, three-dimensional morphology, growth patterns, and optical properties. The composition and tomographic analyses disclose otherwise ambiguous details of the Pt-decorated Au nanoprisms, revealing that both pseudospherical protrusions and dendritic Pt nanoparticles grow on all faces of the nanoprisms (the faceted or occasionally twisted morphologies of which are also revealed), and shed light on the alignment of the Pt nanoparticles. The electron energy-loss spectroscopy investigations show that the Au nanoprisms support multiple localized surface plasmon resonances despite the presence of pendant Pt nanoparticles. The plasmonic fields at the surface of the nanoprisms indeed extend into the Pt nanoparticles, opening possibilities for combined optical and catalytic applications. These insights pave the way toward comprehensive nanoengineering of multifunctional bimetallic nanostructures, with potential applications in plasmon-enhanced catalysis and in situ monitoring of chemical processes via surface-enhanced spectroscopy.

Interfacial electron transfer between sensitizers and semiconducting nanoparticles is a crucial yet poorly understood process. To address this problem, we have used transient absorption (TA) and femtosecond stimulated Raman spectroscopy (FSRS) to investigate the photoexcited dynamics of a series of triphenylamine–coumarin dye/TiO2 conjugates. The TA decay is multiexponential, spanning time scales from 100 fs to 100 ps, while the characteristic transient Raman spectrum of the radical cation decays biexponentially with a dominant ∼3 ps component. To explain these observations, we propose a model in which the decay of the TA is due to hot electrons migrating from surface trap states to the conduction band of TiO2 while the decay of the Raman signature is due to internal conversion of the dye molecule. Furthermore, the S1 Raman spectrum of TPAC3, a dye wherein a vinyl group separates the triphenylamine and coumarin moieties, is similar to the S1 Raman spectrum of trans-stilbene; we conclude that their S1 pote...

The synthesis of silica-encapsulated gold nanoprisms (AuNP@SiO2) is reported. These nanostructures are remarkably stable and resist etching and rounding of their sharp vertices (a process which begins on unprotected Au nanoprisms in a matter of hours) in many chemical environments (water, ethanol, dimethyl sulfoxide, and tetrahydrofuran). The silica growth process has been studied and occurs according to the shape of the particle, where the edges of the prisms are coated less than the large triangular facets. The AuNP@SiO2 particles have dielectric sensitivities that are as large as 737 nm/RIU. Discrete dipole approximation calculations have been used to investigate the effects of this variable thickness on dielectric sensitivity and show that for the anisotropic coatings it is significantly higher than for a uniform coating due to the location of electromagnetic hot spots near the tips and edges of the particles. These calculations also show that dipole resonances exhibit greater sensitivity than multipo...