“…Based on the sensing mechanism model [ 8 ], there are three reasonably effective strategies for increasing the sensitivity and selectivity of SnO 2 : nanostructure modification, heterojunction structure building, and noble metal elements doping. For instance, a slew of remarkable research works is devoted to synthesizing SnO 2 with various nano-morphologies, such as nanowires [ 9 ], nanoflower [ 10 , 11 ], nanofibers [ 12 ], nano hollow [ 13 ], 2D flakes [ 14 ], nanosphere [ 15 , 16 ], 3D mesoporous [ 17 ], hollow sphere [ 18 ], and 3D microporous spheres [ 19 , 20 ]. However, it is extremely hard to find out the mechanisms of how the morphologies changing affects the sensing properties, and the nanostructures of the materials seem extremely difficult to be designed and predicted.…”