TEM images of (a) gold nanoparticle of 8 nm, (b) triangular Ag nanoparticles, (c) Co pthalocyanine/GCN/CNT. Part (a) reproduced from ref. 37 with permission from American Chemical Society, Copyright 2013. Part (b) reproduced from ref. 38 with permission from American Chemical Society, Copyright 2017. Part (c) reproduced from ref. 47 with permission from American Chemical Society, Copyright 2020 respectively.