Two-Dimentional Materials and their Biomedical Applications
Two-dimensional (2D) materials, from graphene to transition metal dichalcogenides (TMDCs), have attracted tremendous attention from researchers in various fields owing to their exceptional properties. This dissertation shows basic properties of some 2D materials and their biomedical applications. Exciton dynamic plays an important role in TMDCs based optoelectronics. When the photon energy is above the A exciton energy, the maximum photocurrent response occurs for the light polarization direction parallel to the metal electrode edge, suggesting that electrons in the valence band of WSe2 prefer to absorb photons with the polarization direction perpendicular to their momentum direction. The photocurrent peak can be controlled by an electric field via the quantum confined Stark effect. This resonance peak can also be shifted by adjusting environment temperatures due to the temperature-dependent nature of the WSe2 band gap. For biomedical application, I demonstrate: (1) the biocompatibility of graphene with primary cultured retinal ganglion cells with various substrate configuration; (2) a unique biosensor combining graphene field- effect transistors and scanning photocurrent microscopy with microfluidic platforms for investigating electrical signals in mouse retina; (3) flexible graphene probes for detecting neuron activity in mouse brain in-vivo and in-vitro.