Plasmonic Oligomers with Tunable Conductive Nanojunctions

Abstract

Engineering plasmonic hot spots is essential for applications of plasmonic nanoparticles. A particularly appealing route is to weld plasmonic nanoparticles together to form more complex structures sustaining plasmons with symmetries targeted to given applications. However, control of the welding and subsequent hot spot characteristics is still challenging. Herein, we demonstrate an original method that connects gold particles to their neighbors by another metal of choice. We first assemble gold bipyramids in a tip-to-tip configuration, yielding short chains of variable length, and grow metallic junctions in a second step. We follow the chain formation and the deposition of the second metal (i.e., silver or palladium) via UV/vis spectroscopy, and we map the plasmonic properties using electron energy loss spectroscopy. The formation of silver bridges leads to a huge red shift of the longitudinal plasmon modes into the mid-infrared region, while the addition of palladium results in a red shift accompanied by significant plasmon damping.

Real-Time In Situ Observations Reveal a Double Role for Ascorbic Acid in the Anisotropic Growth of Silver on Gold

“…Silver and gold nanostructures are technologically relevant because of their exceptional light–matter interactions that originate from localized surface plasmon resonances (LSPR). Core@shell Au@Ag nanoparticles (NPs) have recently emerged as a convenient synthetic pathway to obtain anisotropic NPs with well-defined shape and optical properties. − Depending on the gold seed crystallinity, the silver shell will grow at different locations, changing the overall morphology of the particle which results from a competition between the rate of atom deposition and NP faceting driven by possible preferential adsorption sites and surface diffusion, in other words kinetics versus thermodynamics. , …”

Noble-Metal Nanorod Cryoaerogels with Electrocatalytically Active Surface Sites

“…Silver NRs were prepared following a multistep growth method partially adapted from the work of Li et al and Sánchez-Iglesias et al The four-step synthesis route includes the preparation of small, single-crystalline Au seeds, a thermal treatment to induce their pentatwinning followed by the growth of Au bipyramids (BPs), and finally the overgrowth of the BPs into rod-shaped AgNRs (extinction spectra of the intermediate particles and the fine tuning of the AuBP sizes can be seen in Figures S1 and S2). Gold bipyramids were synthesized in uniform shape and narrow size distribution (Figure S3) to ensure the preparation of high-quality AgNRs.…”

“…Pentatwinned Au seeds are synthesized using the method of Li et al Precursor solution of HAuCl 4 ·3H 2 O (25 mM, 200 μL) and sodium citrate solution (50 mM, 2 mL) are dissolved in CTAC solution (60.6 mM, 16.5 mL) under stirring in a water bath tempered at 30 °C. The solution is gently stirred for 10 min followed by the swift addition of the ice-cold NaBH 4 solution (10 mM, 1.2 mL, freshly prepared) under vigorous stirring.…”

“…Pentatwinned Au seeds are used to grow gold bipyramids using an upscaled protocol of Li et al In a 500 mL bottle, precursor solution of HAuCl 4 ·3H 2 O (25 mM, 4 mL), AgNO 3 solution (10 mM, 2 mL), HCl solution (1 M, 4 mL), and AA solution (100 mM, 1.6 mL) are sequentially added to CTAB solution (100 mM, 200 mL) under stirring at 30 °C. After obtaining a colorless solution, pentatwinned seeds (1.8 mL) are added under stirring, the stirring bar is removed, and the solution is kept in an oven at 30 °C for 4 h and afterward at room temperature overnight.…”

Single Gold Bipyramid Nanoparticle Orientation Measured by Plasmon-Resonant Scattering Polarimetry

“…For instance, color routing has been achieved by manipulating the scattering diagram of two interacting metallic nanoparticles. , In assembled NPs, both optical and mechanical interactions strongly depend on the relative orientation between the NPs. The arising coupled modes have been widely studied and identified by optical measurements. − Another wide range of examples may be found in controlling the spontaneous emission of single emitters with NPs by tailoring their local electromagnetic environment with applications in nanoantennas, , light-emitting devices, Raman spectroscopy, and biosensors. − It is then crucial that the emitter and the metallic NPs are well aligned to maximize their coupling.…”