The unique properties of carbon and silicon-based nanomaterials, including their mechanical, electronic, thermal, and optical properties, have led to rapid advancements in nanotechnology. However, producing large-scale low-dimensional nanomaterials with desired structures remains challenging due to difficulties in controlling atomic-scale physical and chemical reactions during synthesis and a lack of understanding of the underlying mechanisms. Our group is dedicated to developing novel synthesis processes for nanocarbon materials, such as nanotubes, graphene, and nanoporous graphitic film, using chemical vapor deposition and nano-template synthesis methods. We aim to apply these extreme nanocarbon materials in multifunctional energy storage systems and high-performance, low-power nano/microsensors. Additionally, we are investigating a novel catalyst-free chemical vapor etching process to synthesize ultra-high-density and vertically aligned sub-5nm silicon nanowires directly on Si wafers. These ultra-narrow nanowires show an unusual lattice reduction of up to 20% and a direct optical bandgap of 4.16 eV and quasi-particle bandgap of 4.75 eV, indicating significant phonon and electronic confinement for their potential uses in nanoelectronics, optoelectronics, and energy systems.