Ostwald Ripening Growth Mechanism of Gold Nanotriangles in Vesicular Template Phases

Abstract

The mechanism of nanotriangle formation in multivesicular vesicles (MMV) is investigated by using time dependent SAXS measurements in combination with UV-vis spectroscopy, light and transmission electron microscopy. In the first time period 6.5 nm sized spherical gold nanoparticles are formed inside of the vesicles, which build up soft nanoparticle aggregates. In situ SAXS experiments show a linear increase of the volume and molar mass of nanotriangles in the second time period. The volume growth rate of the triangles is 16.1 nm3/min and the growth rate in vertical direction only 0.02 nm/min. Therefore, flat nanotriangles with a thickness of 7 nm and diameters of 23 nm are formed. This process can be described by a diffusion-limited Ostwald ripening growth mechanism. TEM micrographs visualize soft coral-like structures with thin nanoplatelets at the periphery of the aggregates, which disaggregate in the third time period into nanotriangles and spherical particles. The 16 times faster growth of nanotriangles in lateral than that in vertical direction is related to the adsorption of symmetry breaking components, i.e., AOT and the polyampholyte PalPhBisCarb, on the {111} facets of the gold nanoplatelets in combination with confinement effects of the vesicular template phase.

Spiked gold nanotriangles: formation, characterization and applications in surface-enhanced Raman spectroscopy and plasmon-enhanced catalysis

“…79% of the nanoplatelets (including hexagonal and triangular nanoprisms) are long-term stable AOT-coated AuNTs with an average edge length of 175 AE 17 nm. 8 A special feature of the ultrathin nanoplatelets with a thickness of 7.5 AE 1 nm, calculated by different methods, i.e., X-ray reectivity, TEM tomography, 46 SAXS measurements, 30 and veried in ultrafast X-ray diffraction experiments, 47 is their long-term-stability up to a laser uence of 2.9 mJ cm À2 , 47 and their ability to form monolayers. 8,31 In the following we call these ultrathin nanoplatelets AuNTs, because of the fact that 79% of the platelets are triangularlyshaped.…”

“…Here we present a new family of spiked gold nanotriangles (SAuNTs) based on ultra-at (7.5 nm) nanotriangles 8,30 decorated with gold spikes. The idea is to crystallize gold nanoparticles directly on the {111} gold surface of nanotriangles under similar conditions already used for making nanostars.…”

Controlled Assembly of Hierarchical Metal Catalysts with Enhanced Performances

“…Recently, triangular metals have attracted increasing attention owing to their excellent properties from the extremely high anisotropy. [24][25][26][27] However, fabrication of a highly anisotropic structure is not thermodynamically favorable since most of the bulk metals display a face-centered cubic shape. Controlled colloid chemistry reaction is one of the main techniques for synthesizing triangular metals in which the capping ligand has proven to be critical.…”

One Dimensional AuAg Nanostructures as Anodic Catalysts in the Ethylene Glycol Oxidation

“…This accounts for the size difference between the NWs formed after aging at 20 and 25 • C. It is clear that, as the temperature was elevated, it played a more significant role. In the case of the highest studied temperature (40 • C), Oswald ripening completely dominated the growth process, resulting in only nanoparticles [62,63], while at 30 and 35 • C, we saw that the final structures were composed of both NW and nanoparticle features. Given that the lower temperatures favoured nanowires and the highest temperature produced nanoparticles, it is expected that this morphology change occurred.…”