Each month, the ISGS Newsletter features an interesting and striking micrograph (or series of micrographs) chosen from a recent issue of the Journal of Sol-Gel Science and Technology or from unpublished sources such as PhD theses, etc (with full attribution given). If you know of any interesting images that might be suitable, please contact the ISGS Newsletter Editor for inclusion. The micrographs can be optical, SEM, TEM, AFM, etc, and a brief description of the samples should be provided.
This month’s images are taken from three different papers in the latest issue of JSST and once again highlight the breadth of sol-gel science and technology, together with the areas in which our community is making an impact.
The first is taken from the work of Atay and Gultepe entitled “The effect of spinning cycle on structural, optical, surface and photocatalytic properties of sol–gel derived ZnO films” (JSST, (2021), https://doi.org/10.1007/s10971 -021-05661-4), which explores the effect of the number of spinning cycles on the photocatalytic performance of ZnO films deposited by spin coating. It was found that the structural, optical and surface properties of the films was significantly modulated by increasing the number of layers deposited from three to five, due both to the formation of higher-surface-area arrays of nanosized particles aligned in columnar arrays and to a decrease in the number of defect states, leading to enhanced photocatalytic activity.
The second series of micrographs is from the work of Ramallo, Morrone, Lionello , Angelomé and Fuertes. This paper, entitled “Mechanical properties and structural integrity of devices based on sol–gel mesoporous oxides thin films” (JSST, (2021), https://doi.org/10.1007/s10971-021-05636-5), explores the mechanical properties of porous and multi-layered titania/silica coatings and the process parameters that impact on their structural integrity. Nanoindentation studies demonstrated that mesoporous bilayer silica films exhibited a plastic behaviour with out delamination during penetration throughout the entire film cross-section, while the bilayer titania coatings (with similar thickness) fractured and delaminated under such conditions. In the case of silica/titania and titania/ silica bilayer films, the failure during indentation was controlled by the properties of the more brittle titania layer. For example, in the case of the titania/silica coating, delamination of the top mesoporous silica layer is promoted by the stresses generated during failure of the titania layer.