Fig. 2

a Schematic diagram of the localized surface plasmon resonance (LSPR) shift on Au nanomaterials depending on their different shapes (nanosphere, prism, cube, star, or rod). Reproduced with permission from [30], copyright MDPI, 2020. b Schematic images of the structures of representative allotropes of carbon nanomaterials. Reproduced with permission from [34], copyright American Chemical Society, 2015. c Schematic illustration of the crystal structure of MoS₂, which consists of a transitional metal (Mo) atomic layer sandwiched between two chalcogen (S) atomic layers. Reproduced with permission from [37], copyright American Chemical Society, 2015. d Schematic illustration of the atomic structure and constituting elements of the Ti₃C₂T_x MXene. Reproduced with permission from [39], copyright American Chemical Society, 2018