Micrograph of the Month(s) from the Journal of Sol-Gel Science and Technology January to March 2023

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(or series of micrographs) chosen from a recent issue of the Journal of Sol-Gel Science and Technology or from unpublished sources such as PhD theses, etc (with full attribution given).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 series is taken from the work of Wang, Zou, Huang, Xu, Chen, Yan, Zhu, Cao and Lin entitled “Efficient prevention of cracking of external gelation-made thorium oxide microspheres by hydrothermal treatment” (JSST (2023) 105, 709-720; https://doi.org/10.1007/s10971-023-06046-5). This work explores the effect of synthesis conditions on the structural evolution of relatively large, uniform ThO2 “microspheres” prepared via external gelation, for potential applications in nuclear fuel rods. The as prepared spheres (top-left image) were prepared from a colloidal ThO2 solution containing PVA, using a vibrating needle to generate droplets which were subsequently gelled and aged in an ammonia solution. Hydrothermal treatment of the as prepared spheres resulted in the product shown in the top-right image. Subsequent heat treatment of the as prepared and hydrothermally processed samples at elevated temperatures led to a cracked product in the former case, compared to high quality, crack free spheres in the latter case. The effect of hydrothermal treatment on the structure and composition of the spheres is elucidated. 


The second series of micrographs is from the work of Patel and Joshi. This paper, entitled “Green and chemical approach for synthesis of Ag2O nanoparticles and their antimicrobial activity” (JSST, (2023) 105, 814-826; https:// doi.org/10.1007/s10971-023-06036-7), investigates different approaches for the synthesis of silver oxide nano-particles and their associated antibacterial activity. The nanoparticles were synthesised by either (a) the dropwise addition of an extract obtained by boiling the leaves of the Salix Integra plant to a solution of AgNO3; or (b) addi-tion of aqueous ammonia solution to a solution of AgNO3 followed by addition of citric acid. The latter synthesis yielded an intriguing fibrous aggregate structure, as shown in the micrograph on the right. At higher magnifi-cation, arrays of Ag2O nanoparticles are evident (see image on the left). Both samples exhibited antimicrobial activity towards M. tuberculosis H37Rv, M. fortuitum and M. chelonae, but were essentially inactive against M. abscessus. 


The third series of images is from the work of Liu, Wang, Du, Song, Zhang, Li, and Chang entitled “Significantly boosting the visible light activity of BiOCl by facile solvothermal doping with chromium” (JSST, (2023) 105, 793-803; https://doi.org/10.1007/s10971-023-06047-4). This paper explores the effect of doping BiOCl photocatalysts with metal ions such as Cr(III), Zn(II), Mn(II), Cu(II) and Ni(II), with the best results being obtained with Cr(III) doping. In the micrographs below, the images in the lefthand column illustrate the flowerlike structure of undoped BiOCl, while the other columns illustrate the effect of doping with 0.5 % (b,f), 5 % (c,g) and 10 % Cr(III) (d,h). The incorporation of Cr(III) within BiOCl significantly enhanced the photocatalytic activity of the material, with over 99 % of a model pollutant (rhodamine B) being decomposed within four minutes under the conditions used in the study. In contrast, only 60% degradation was obtained in the case of the undoped catalysts under the same conditions. 

The final series of images is from the work of Hashemi, Ataollahi, Hasani, and Seifoddini. This paper, entitled “Synthesis of the cobalt ferrite magnetic nanoparticles by sol–gel auto combustion method in the presence of egg white (albumin)” ((JSST, (2023) 106, 23-36; https://doi.org/10.1007/s10971-023-06073-2), describes the synthesis of cobalt ferrite nanoparticles, via auto combustion, in the presence of varying quantities of egg white albumin. Such proteins are known to form stable complexes with metal ions in aqueous solution, and intriguing variations in the morphology (size and shape) of the CoFe2O4 particles are evident as the quantity of albumin in the precursor solutions is varied from 0 (micrograph (a)) to 0.25 (b), 0.5 (c) or 0.75 g (d). The results obtained indicated that the saturation magnetization and coercivity were significantly enhanced in samples processed with the albumin.