Fig. 1

(i) a–c Morphological analysis of the 5 Tb–SnO₂ yolk–shell spheres; d EDS elemental mapping of Sn, Tb, and O in 5 Tb–SnO₂; e–g SEM and TEM images of 15 Tb–SnO₂; and h EDS elemental mapping of Sn, Tb, and O in 15 Tb–SnO₂. (ii) Gas sensing transients of the (a) pure SnO₂, (b) 1 Tb–SnO₂, (c) 5 Tb–SnO₂, and (d) 15 Tb–SnO₂ sensors to 20 ppm of acetone at 450 ℃ under dry and humid conditions (RH = 20, 50, 80%). Gas responses of (e) pure SnO₂, (f) 1 Tb–SnO₂, (g) 5 Tb–SnO₂, and (h) 15 Tb–SnO₂ sensors to various gases (concentration: 20 ppm) at 350, 375, 400, 425, and 450 ℃ under dry condition. Reprinted from [79] with permission from American Chemical Society