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(or series of micrographs) chosen from a recent issue of the Journal of Sol-Gel Science and Technology or from unpublished sources such as PhD theses, etc (with full attribution given).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 Xiao, Wang, Liu, Wei, Luo, Zeng and Yi entitled “Promising pure gold aerogel: in situ preparation by composite sol–gel and application in catalytic removal of pollutants and SERS” (JSST, (2021) 99, 614-626, https://doi.org/10.1007/s10971-021-05597-9), which describes the preparation of high-purity gold aerogels via reduction of Au(III) salts in the presence of a cellulose triacetate template. The as-prepared aerogels appear black in colour to the naked eye (consistent with highly dispersed, 10– to 15-nm-sized crystallites) and exhibit densities of 0.3-0.35 g.cm-3 (> 98 % porosity). Under Xe-lamp irradiation, they demonstrate good photocatalytic activity for the degradation of Congo red, 4-nitrophenol and rhodamine B. Following pressing at 1 MPa, porous gold-coloured disks were obtained which were shown to be excellent substrates for acquiring surface-enhanced Raman spectra from rhodamine B solutions with concentrations as low as 10-7 M.
The second series of micrographs is from the work of Liu, Ma, Tao, Cui, Tian, Liu, He, Dong, Song and Zhang entitled “A facile approach to the synthesis of Er3+ –Yb3+ –Mo6+ co-doped TiO2 /Yb2 Ti2 O7 electrospun nanofibers and high thermal sensitivity” (JSST, (2021), 99, 557-564, https://doi.org/10.1007/s10971-021-05598-8). This paper describes the synthesis of luminescent nanofibers via electrospinning for potential applications in optical up-conversion. The SEM micrographs on the left show the structure of the fibres before (A-D) and after (E-H) annealing at 1000oC for Er:Yb:Mo:Ti molar ratios of 0:0:0:100 (A,E); 1:10:2:100 (B,F); 2:20:4:100 (C,G); and 5:50:10:100 (D,H). The TEM EDX elemental maps for the latter system are included on the right.
The final series of micrographs is from the work of Güler, Selen, Başgöz, Safa and Yahia entitled “Adsorption properties and synthesis of silica aerogel-hollow silica microsphere hybrid (sandwich) structure” (JSST, (2021), https://doi.org/10.1007/ s10971-021-05622-x), which explores the uptake of methylene blue on a hierarchical silica structure in which silica aerogels are supported on hollow silica microspheres. The use of the hollow microspheres to produce a “sandwich” structure enhances the mechanical strength of the adsorbent, thus facilitating its removal from solutions once the sorbent becomes saturated and its subsequent reuse. The SEM micrograph (20 nm scale bar) illustrate the morphology of the system after uptake of methylene blue, while the optical images illustrate the colour of the hybrid before and after uptake.