Pratibha L. Gai

Structural and compositional studies of nanomaterials of technological importance have been carried out using advanced electron microscopy methods, including aberration‐corrected transmission electron microscopy (AC‐TEM), AC‐high angle annular dark field scanning TEM (AC‐HAADF‐STEM), AC‐energy filtered TEM, electron‐stimulated energy dispersive spectroscopy in the AC‐(S)TEM and high‐resolution TEM (HRTEM) with scanning tunneling microscopy (STM) holder. The AC‐EM data reveal improvements in resolution and minimization in image delocalization. A JEOL 2200FS double‐AC field emission gun TEM/STEM operating at 200 kV in the Nanocentre at the University of York has been used to image single metal atoms on crystalline supports in catalysts, grain boundaries in nanotwinned metals, and nanostructures of tetrapods. Joule heating studies using HRTEM integrated with an STM holder reveal in situ crystallization and edge reconstruction in graphene. Real‐time in situ AC‐HAADF‐STEM studies at elevated temperatures are described. Dynamic in‐column energy filtering in an AC environment provides an integral new approach to perform dynamic in situ studies with aberration correction. The new results presented here open up striking new opportunities for atomic scale studies of nanomaterials and indicate future development directions. Microsc. Res. Tech., 2011.

A synergetic Fe–Al effect in Fe₂O₃ nanoparticles supported on mesoporous aluminosilicates compared to pure siliceous silicates has been demonstrated, for the first time, by a remarkably superior catalytic activity of the former in the microwave-assisted selective oxidation of benzyl alcohol to benzaldehyde. This significant finding, that also deeply influences the acidity of the materials (increasing total and particularly Lewis acidity), can have important consequences in the improved efficiency of these systems in related oxidations as well as in acid catalysed processes.

An efficient protocol for the hydrogenation of platform molecules (e.g.succinic acid) in aqueous environments using supported metal nanoparticles on polysaccharide derived mesoporous carbonaceous materials is reported for the first time.

Advances in atomic resolution in situ environmental transmission electron microscopy for direct probing of gas‐solid reactions, including at very high temperatures (∼2000°C) are described. In addition, recent developments of dynamic real time in situ studies at the Angstrom level using a hot stage in an aberration corrected environment are presented. In situ data from Pt/Pd nanoparticles on carbon with the corresponding FFT/optical diffractogram illustrate an achieved resolution of 0.11 nm at 500°C and higher in a double aberration corrected TEM/STEM instrument employing a wider gap objective pole piece. The new results open up opportunities for dynamic studies of materials in an aberration corrected environment. Microsc. Res. Tech., 2009.

Size-controlled MgO nanocrystals were synthesised via a simple sol-gel method and their bulk and surface properties characterised by powder XRD, HRTEM and XPS. Small, cubic MgO single crystals, generated by low temperature processing, expose weakly basic (100) surfaces. High temperature annealing transforms these into large, stepped cuboidal nanoparticles of periclase MgO which terminate in more basic (110) and (111) surfaces. The size dependent evolution of surface electronic structure correlates directly with the associated catalytic activity of these MgO nanocrystals towards glyceryl tributyrate transesterification, revealing a pronounced structural preference for (110) and (111) facets.