The effect of heat treatment on the morphology and mobility of Au nanoparticles

Abstract

In the present paper, we investigate the effect of heat treatment on the geometry and mobility of Au nanoparticles (NPs) on a Si substrate. Chemically synthesized Au NPs of diameter ranging from 5 to 27 nm were annealed at 200, 400, 600 and 800 °C for 1 h. A change in the geometry from faceted to more rounded shapes were observed with increasing annealing temperature. Kinetic Monte Carlo simulations indicate that the NPs become rounded due to the minimization of the surface area and the transition to lower energy surface types {111} and {100}. The NPs were manipulated on a silica substrate with an atomic force microscope (AFM) in tapping mode. Initially, the NPs were immovable by AFM energy dissipation. However, annealed NPs became movable, and less energy was required to displace the NPs annealed at higher temperature. However, after annealing at 800 °C, the particles became immovable again. This effect was attributed to the diffusion of Au into the Si substrate and to the growth of the SiO2 layer.

Straightforward synthesis of gold nanoparticles by adding water to an engineered small dendrimer

“…The absence of gold outside the nanoparticles, according to the EDX results for the background, indicated that the gold nanoparticles were obtained in a quantitative yield. The conditions for clustering the gold NPs were recently studied [ 66 ] and it was shown that heating the gold NPs at a very high temperature (800 °C) yielded NPs with a pentagonal symmetry [ 67 ]. In this work a very similar structure was obtained, as shown in Fig.…”

Heat-Induced Fragmentation and Adhesive Behaviour of Gold Nanowires for Surface-Enhanced Raman Scattering Substrates

“…It is well known that the adhesion and static friction of metal nanostructures decrease significantly after annealing due to the rounding and decreasing of the contact area with the substrate [27]. The atomic force microscopy (AFM) manipulation approach can be successfully applied to probe the adhesion/static friction magnitude and to estimate the fraction of movable NPs [28], which, for example, can be displaced or washed away during the drop-casting of the investigated chemical solution due to capillary forces. This understanding becomes critical when examining techniques like heat-induced nanowire (NW) fragmentation, which could potentially be used for creating SERS substrates.…”

Heat-induced morphological changes in silver nanowires deposited on a patterned silicon substrate

“…In practical applications, the diameters of Ag NWs are typically significantly larger. However, during prolonged heat treatment (lasting minutes or more), surface atom diffusion can lead to morphological changes in NWs even at temperatures several hundred degrees below the melting point of the material [ 26 – 27 ]. Sintering of Ag and Au NWs at intersections can occur at temperatures as low as 125–200 °C within minutes [ 27 – 28 ].…”