Centrifugal Shape Sorting and Optical Response of Polyhedral Gold Nanoparticles

Abstract

A centrifugal route for separating small {110}-faceted gold nanostructures, namely rhombic dodecahedra (RD) and triangular bipyramids (BPs), which form simultaneously during synthesis and cannot be separated by means of conventional filtration methods, is presented. The centrifuged solution shows two distinct bands: i) RD and ii) BPs, as verified in the corresponding scanning electron microscopy images. The sorted BPs show a refractive index dependence 2.5 times that of the as-synthesized, unsorted mixture.

Assembly and Electronic Applications of Colloidal Nanomaterials

“…[165] One method for releasing these polymers is to trigger their conformation change by acids [166] or chelating agents. This strategy has been successfully applied to separate gold rhombic dodecahedra from gold bipyramids in a density-gradient medium of iodixanol, [173] which results in visibly colored bands in the centrifuge tube ( Figure 3A-C). These sacrificial bonds can be selectively cleaved with acid treatments, leading to the flocculation of relatively pristine SWCNTs.…”

“…[132,189] For example, SWCNTs with metallic or semiconducting purities in excess of 99% have been prepared and are available commercially. [121] www.advmat.de www.advancedsciencenews.com [173] Copyright 2013, Wiley-VGH. A key innovation for 2D nanomaterial sorting was the replacement of the small-molecule surfactant sodium cholate with bulkier Pluronic block-copolymer surfactants, whose larger hydration-layer thicknesses reduce the buoyant density of the nanomaterials in aqueous density-gradient media, leading to effective isopycnic sorting of 2D TMDs [125] and multilayer h-BN.…”

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

“…9,10 As-synthesized anisotropic Au NPs are polydisperse in size and shape, however, which prevents detailed analysis of shape-dependent phenomena in ensemble measurements. 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.…”

“…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.…”

Micro-Extinction Spectroscopy (MExS): a versatile optical characterization technique

“…d Representative point spectra extracted as shown in a for absorbance, reflectance, and darkfield scattering decahedra, bipyramids, and other shapes, and, together with the NP's LSPR energy and stability, are critical design rules for plasmon sensors [37][38][39][40][41]. An even more powerful expression is the sensing figure of merit (FOM), [42] defined as the RIS divided by the LSPR full width at half maximum (FWHM) in eV, i.e.,…”