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Abstract Laser-assisted atom probe tomography (APT) is a relatively new, powerful technique for sub-nanometric mineral and biomineral analysis. However, the laser-assisted APT analysis of highly anisotropic and chemically diverse minerals, such as phyllosilicates, may prove especially challenging due to the complex interaction between the crystal structure and the laser pulse upon applying a high electric field. Micas are a representative group of nonswelling clay minerals of relevance to a number of scientific and technological fields. In this study, a Mg-rich biotite was analyzed by APT to generate preliminary data on nonisotropic minerals and to investigate the effect of the crystallographic orientation on mica chemical composition and structure estimation. The difference in results obtained for specimens extracted from the (001) and (hk0) mica surfaces indicate the importance of both experimental parameters and the crystallography. Anisotropy of mica has a strong influence on the physicochemical properties of the mineral during field evaporation and the interpretation of APT data. The promising results obtained in the present study open the way to future innovative APT applications on mica and clay minerals and contribute to the general discussion on the challenges for the analysis of geomaterials by atom probe tomography. 

Abstract Although challenging, assembling and orienting non-spherical nanomaterials into two- and three-dimensional (2D and 3D) ordered arrays can facilitate versatile collective properties by virtue of their shape-dependent properties that cannot be realized with their spherical counterparts. Here, we report on the self-assembly of gold nanorods (AuNRs) into 2D films at the vapor/liquid interface facilitated by grafting them with poly(ethylene glycol) (PEG). Using surface sensitive synchrotron grazing incidence small angle X-ray scattering (GISAXS) and specular X-ray reflectivity (XRR), we show that PEG-AuNRs in aqueous suspensions migrate to the vapor/liquid interface in the presence of salt, forming a uniform monolayer with planar-to-surface orientation. Furthermore, the 2D assembled PEG functionalized AuNRs exhibit short range order into rectangular symmetry with side-by-side and tail-to-tail nearest-neighbor packing. The effect of PEG chain length and salt concentration on the 2D assembly are also reported.