Behavior of Au Nanoparticles under Pressure Observed by In Situ Small-Angle X-ray Scattering

Abstract

The mechanical properties and stability of metal nanoparticle colloids under high-pressure conditions are investigated by means of optical extinction spectroscopy and small-angle X-ray scattering (SAXS), for colloidal dispersions of gold nanorods and gold nanospheres. SAXS allows us to follow in situ the structural evolution of the nanoparticles induced by pressure, regarding both nanoparticle size and shape (form factor) and their aggregation through the interparticle correlation function S(q) (structure factor). The observed behavior changes under hydrostatic and nonhydrostatic conditions are discussed in terms of liquid solidification processes yielding nanoparticle aggregation. We show that pressure-induced diffusion and aggregation of gold nanorods take place after solidification of the solvent. The effect of nanoparticle shape on the aggregation process is additionally discussed.

Interparticle Interactions of Dendrimer, Comb, and Linear Grafted Nanoparticles via Coarse-Grained Molecular Dynamics Simulations

“…This agrees with experimentally observed aggregation for NPs compressed under high pressure (>3 GPa). 93 Notably, the increase in PMF (the energy cost to push the two particles toward each other) increases more rapidly for the dendrimer structure as compared to the linear structure for all of the grafting densities with decreasing r (Figure 3). For example, the magnitude and onset of the interparticle repulsion increases with increasing ligand grafting density and is more significant in D3 systems when compared with L-14 systems at any given ligand grafting density.…”

The influence of PEGylated gold nanoparticles on the solidification of alcohols

“…While our study establishes that AuNP are unsuitable for phase transition sensing, it remarkably highlights the suitability of AuNS for refractive index sensing in crystalline phases, as previously proposed. 5,32…”

“…, after pressure solidification. 32,33 Notably, we could use the LSPR wavelength variation with pressure to obtain the pressure dependence of the EtOH refractive index n ( P ), following the procedure already established elsewhere. 3 Since AuNR have a higher spectral sensitivity than AuNS to variations of the refractive index of the surrounding medium, we used the pressure variation of their LLSPR wavelength to obtain the variation of EtOH refractive index with pressure in the hydrostatic regime, from 0 to 3 GPa.…”

“…However, as already mentioned, AuNR undergo aggregation and plastic deformation under non-hydrostatic pressure conditions. 32,33 In this way, we used the plasmonic response of AuNS to obtain the information of n ( P ) in the non-hydrostatic regime, from 3 to 5.5 GPa, where AuNR are no longer valid for this purpose.…”

Theoretical and Experimental Advances in High-Pressure Behaviors of Nanoparticles

“…It was concluded that the solidification of the solvents led to aggregation and deformation of Au NRs, resulting in the significantly broadening and anomalous shift in the surface plasmon bands. However, the solvent solidification had a negligible spectroscopic effect on the SPR shifts in the case of nanospheres, which indicates that Au nanospheres can be used as a suitable high-pressure plasmonic sensor as they are extremely stable, even under severe nonhydrostatic conditions. − So far, variations of the SPR peak wavelengths with pressure have been efficiently used for high-pressure refractive index sensing. , SPR of Cu NRs and Ag decahedron NPs has also been reported recently. In general, for both NPs, the SPR peaks showed redshifts with increasing pressure, but there was an abnormal blue shift observed for Cu NPs between 8 and 15 GPa, and for Ag NPs between 8 and 11 GPa.…”