Due to strong interlayer coupling and quantum confinement, the electronic band structure of the 2D materials is highly dependent on the thickness of the layer. The strong increment in the Coulomb interactions among charge carriers and defects are observed in the semiconducting 2D materials due to significantly reduced dielectric screening and the quantum confinement. In general, the mobility of any 2D materials increases with decreasing number of layers, however, some exceptions are also there. Similarly, the charge carrier mobility of 2D materials depends on the number of layers, charge carrier polarity, charge impurities, localized states, defects, temperature, substrate, contacts, and device geometry. Due to the absence of surface groups or dangling bonds, the charge carrier scattering is also reduced in the 2D materials as compared to the bulk. The layered 2D materials have comparatively weaker interlayer vdW interaction and therefore, the stacked layers are weakly bound to each others. This large dimension ratio of lateral to the transverse makes 2D layered materials more interesting as compared to their bulk counterpart. ĢD materials are crystalline solids with relatively very large lateral dimensions as compared to their thickness. The most striking features of optical biochemical sensors based on 2D materials are ultra-sensitivity and ultrafast response, thereby posing the potential to replace some of the current electrical sensors used for biochemical sensing applications. Therefore, 2D materials have become widespread in biochemical sensing, diagnostics, and health-care applications. Moreover, the 2D materials of interest possess excellent biocompatibility, exceptional fluorescence-quenching ability, broadband light absorption, high chemical stability, outstanding robustness and flexibility. Second, the large surface-to-volume ratio allows high-energy transfer efficiency and fast response time due to ultrafast carrier mobility. First, due to the atomic-thin layer structure and large surface area, they are excellent substrates for adsorption of biomolecules via π–π stacking. Qiaoliang Bao, in Fundamentals and Sensing Applications of 2D Materials, 2019 10.2 Biochemical Optical Sensing Properties of 2D MaterialsĢD materials have exceptional biochemical optical sensing properties.