Abstract: Synthesis of low-dimensional nanomaterials, including plasmonic nanostructures, two-dimensional (2-D) material graphene, and beyond, will be discussed.  Also discussed will be a variety of sensing, electronic, and energy applications of these low-dimensional nanomaterials.

Hollow and porous metal nanostructures, a novel class of plasmonic nanostructures, exhibit extraordinary optical and catalytic properties compared with their solid counterparts due to a higher surface to volume ratio and the facile tunability of the localized surface plasmon resonance (LSPR) wavelength over a broad range from visible to parts of near-infrared.

This talk will explore design and synthesis, and comprehensively characterize the optical properties of hollow plasmonic nanostructures, including plasmonic nanocages and nanorattles comprised of gold nanostructures as cores and porous gold cube as shells. The significantly higher refractive index sensitivity of hollow plasmonic nanostructures compared with that of other solid nanostructures of similar size leads to LSPR sensors with higher sensitivity and lower limit-of-detection compared with biosensors based on solid counterparts. Furthermore, plasmonic nanorattles host electromagnetic hot spots between the core and the shell, offering significantly higher surface-enhanced Raman scattering (SERS) enhancement as compared with other solid nanostructures of similar size.

In the second part of this talk, methods for the synthesis of 2-D materials including graphene and transition metal dichalcogenide (TMDC) materials will be presented,and their electronic and energy applications will be discussed. Chemical vapor deposition (CVD) methods have allowed the production of large-area graphene on metal substrates (e.g., copper and nickel foil). Direct formation of graphene on insulating substrates can eliminate the wet-transfer processes that generally involve metal substrate etching and undesirable polymer residue. Methods for the direct formation of wafer-scale graphene thin layers on insulating substrates will be discussed.

Furthermore, molybdenum disulfide (MoS₂), a semiconducting 2-D layered material in the TMDC family, exhibits unique electrical, optical, and mechanical properties. Synthesis of wafer-scale and highly crystalline MoS₂ nanosheets using thermal decomposition and CVD methods has been achieved. The MoS₂ devices exhibit a high on/off current ratio and excellent carrier mobility. The promising performance of MoS₂ devices prove them to be potential candidates in electronics and optoelectronics applications in the near future.