“…In the NiO nanoparticles, four Raman scattering peaks were observable at 510, 742, 1085, and 1490 cm −1 , and those could be ascribed to the first-order longitudinal optical (LO 1 ) phonon mode of the Ni-O lattice vibration, the second-order transverse (TO 2 ), the second-order longitudinal optical (LO 2 ) phonon modes [ 39 , 57 ], and the two-magnon (2 M) mode of the NiO [ 31 ], respectively. Different from the NiO nanoparticles, the AC-NiO nanotablets revealed three additional Raman peaks at 1360, 1586, and 2856 cm −1 , attributing to D, G, and 2D bands of AC nanosponges [ 58 , 59 ] (see also Figure S3 ). From the Raman intensity ratio between D and G peaks (I D /I G = 0.99), one may also confirm that our biomass-AC was well graphitized [ 44 ].…”