Synthesis, Separation, and Hypermethod Characterization of Gold Nanoparticle Dimers Connected by a Rigid Rod Linker

Abstract

Bonding individual metallic nanoparticles at small separation distances to let them form dimers and making them available in large quantities is a key requirement for various applications that wish to exploit the tremendous enhancement of electromagnetic fields in plasmonic junctions. Although progress has been witnessed in the past concerning the fabrication of dimers mediated by rigid molecular linkers, the exact bonding mechanism remains unclear.Here, we describe the fabrication of a rigid linker molecule and demonstrate its feasibility to achieve dimers made from closely spaced metallic nanoparticles in large quantities. Although the topography of the dimers proofs the success of the fabrication method, we use what we call a hypermethod characterization approach to study the optical properties of dimers from various perspectives. Measuring the surface enhanced Raman scattering signal of the linker molecule enables tracing directly the optical environment it perceives. By reaching a strong field enhancement in the gap of the dimers, we are able to investigate optical and geometrical properties of the linker. Moreover, upon isolation of the dimers, we use single particle extinction spectroscopy to study the optical response of a fabricated dimer directly. Full wave numerical simulations corroborate the experimental results and provide insights into quantities, which cannot be accessed directly in experiments. The ability to fabricate and to characterize rigidly linked nanoparticles will pave the way towards various plasmonic applications such as sensors, photocatalysis, and plexcitonics.

Computing the T-matrix of a scattering object with multiple plane wave illuminations

“…We take established experimental data for the dispersive permittivity of silver [43]. Such objects can be fabricated in large quantities by self assembly methods, e.g., by connecting commercially available metal nanospheres with a linker molecule [44]. …”

Metal-enhanced upconversion luminescence of NaYF4:Yb/Er with Ag nanoparticles

“…Local field enhancement including excitation and emission enhancement, energy transfer and non-radiative decay process are the mostly common considered reasons in understanding the mechanism of the enhancement [23]. To understand the observed experimental phenomena, it is necessary to study the property of the local EM field around the Ag particles through numerical simulation.…”

“…According to published study, results of experimental observation on the fluorescence enhancement are diversified and specific enhancement mechanism is still need to be investigated carefully. In most of experimental study, optical measurements are performed with ensemble of many particle system, for example in solution or powder system [21][22][23][24][25][26][27]. Therefore, it is necessary to establish a clear and effective system to investigate the fluorescence enhancement effect in a rather clear and precise manner.…”

Shape-Dependent Relaxivity of Nanoparticle-Based T1 Magnetic Resonance Imaging Contrast Agents

“…11,12 Density gradient centrifugation (DGC) is an emerging postsynthetic separation method that has been used to refine structural distributions of nanomaterials. 12–19 Anisotropic Au NPs that have been sorted by DGC have primarily been coated with cetyltrimethylammonium bromide (CTAB) 14–16 or cetyltrimethylammonium chloride (CTAC), 12 which hinder conjugation with ligands. 20–22 Expanding DGC to separate anisotropic Au NPs without these strongly bound surfactants is crucial for investigating shape-dependent properties of functionalized nanoconjugates.…”