Micrograph of the Month(s) from the Journal of Sol-Gel Science and Technology

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(or series of micrographs) chosen from a recent issue of the Journal of Sol-Gel Science and Technology or from unpublished sources such as PhD theses, etc (with full attribution given).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.

The first micrographs are taken from the work of Wang, Long Su, Jiang Zheng, Yang, Li and Zou entitled “Study on preparation of SiO2/PTFE aerogel-like materials via atmospheric drying and their thermal insulation performance” ((JSST (2024) 109, 204-214; https://doi.org/10.1007/s10971-023-06261-0). This work explores the synthesis and characterisation of hybrid SiO2/PTFE aerogels with densities as low as 0.087 g/cm3 obtained via a low -temperature ambient pressure drying strategy. As illustrated in the left-hand photograph (page 12), the materials exhibit excellent mechanical properties, with essentially no thermal decomposition at temperatures below 500oC. They remained hydrophobic even after exposure to 1 M HCl for one week, with contact angles of 140 o being ob-served (middle photograph). The thermal conductivity of the optimum material was ~ 64 mW/mK, which is slightly higher than that of similar aerogel materials prepared from precursors such as MTMS. However, as illustrated in the right-hand photograph, the SiO2/PTFE aerogel still exhibits excellent thermal insulation properties. 


The second series of micrographs is from the work of Yan, Liang, Liu, Zhang, Zeng, Bai, Zhu and Li. This paper, entitled “Synthesis of PANI@α-Fe2O3/Al2O3 photo-Fenton composite for the enhanced efficient methylene blue removal” (JSST, (2024) 109, 137-149; https://doi.org/10.1007/s10971-023-06253-0), explores the hydrothermal-assisted sol-gel synthesis of nanocomposite photocatalysts based on Fe2O3 supported on flat α-Al2O3 plates. Following heat-treatment at selected temperatures, the Fe2O3/Al2O3 plates were coated with polyaniline and used as anodes in an electric-field-assisted photo-Fenton reactor. At processing temperatures under 500oC, the Fe2O3 formed nanorods on the surface of the Al2O3 plates, with the width and length of the rods increasing with temperature. At 550oC, α-Fe3O3 nanotubes were formed. Under optimal conditions, up to 98% decomposition of methylene blue dyes were obtained in the electric-field-assisted reactor over a wide pH range (pH 4-9). 

The third series of images is from the work of Li, Xu, Xu, Zhu, Wang, Jiang and Jin entitled “Universal and facile sol-gel approach for fabrication of multitudinous yolk-shell architectures” (JSST, (2024) 109, 421-432; https://doi.org/10.1007/s10971-023-06289-2). This paper explores the synthesis and optical properties of hollow yolk shell architectures consisting of mesoporous silica shells containing “yolks” consisting of species such as PtOx, IrOx, FeOx and titanosilicate zeolites. An example of the intriguing morphologies obtained is shown in the micro-graphs below, which illustrate the structure of particles with an IrOx yolk and a mesoporous silica shell. 

The final series of images is from the work of Peng, Liu, Zeng, Cui, Wang, Li, Liu, Wang and Liu. This paper, en-titled “Low temperature deep eutectic solvents-assisted synthesis of amorphous MnO2 cathode for zinc ion bat-teries” (JSST, (2024) 109, 695-706; https://doi.org/10.1007/s10971-023-06308-2), describes the synthesis and characterisation of cathode materials for zinc ion batteries. The cathode material was synthesised in a deep eu-tectic solvent consisting of urea and betaine, from which MnO2 was produced via the ambient-temperature reduc-tion of KMnO4. The micrographs illustrate changes in the structure of the amorphous MnO2 during charge/discharge cycles of the zinc ion battery. Platelets identified as Zn4SO4(OH)6.5H2O are formed during discharge, which subsequently disappear during charging. This indicates that Zn2+/H+ could be reversibly associated with/dissociated from the MnO2 electrode during cycling, accompanied by the formation/dissolution of Zn4SO4(OH)6.5H2O.