In this paper, we demonstrate the seeded growth of graphene under a plasma chemical vapor deposition condition. First, we fabricate graphene nanopowders (~5 nm) by ball-milling commercial multi-wall carbon nanotubes. The graphene nanoparticles were subsequently subject to a direct current plasma generated in a 100 Torr 10%CH4 - 90%H2 gas mixture. The plasma growth enlarged, over one hour, the nuclei to graphene sheets larger than one hundred nm2 in area. Characterization by electron and X-ray diffraction, high-resolution transmission electron microscopy images provide evidence for the presence of monolayer graphene sheets.

Over the history of carbon, it is generally acknowledged that Bernal AB stacking of the sp2 carbon layers is the unique crystalline form of graphite. The universal graphite structure is synthesized at 2,600~3,000 °C and exhibits a micro-polycrystalline feature. In this paper, we provide evidence for a metastable form of graphite with an AA’ structure. The non-Bernal AA’ allotrope of graphite is synthesized by the thermal- and plasma-treatment of graphene nanopowders at ~1,500 °C. The formation of AA’ bilayer graphene nuclei facilitates the preferred texture growth and results in single-crystal AA’ graphite in the form of nanoribbons (1D) or microplates (2D) of a few nm in thickness. Kinetically controlled AA’ graphite exhibits unique nano- and single-crystalline feature and shows quasi-linear behavior near the K-point of the electronic band structure resulting in anomalous optical and acoustic phonon behavior.

Evidence is presented in this paper that certain single-wall carbon nanotubes are not seamless tubes, but rather adopt a graphene helix resulting from the spiral growth of a nano-graphene ribbon. The residual traces of the helices are confirmed by high-resolution transmission electron microscopy and atomic force microscopy. The analysis also shows that the tubular graphene material may exhibit a unique armchair structure and the chirality is not a necessary condition for the growth of carbon nanotubes. The description of the structure of the helical carbon nanomaterials is generalized using the plane indices of hexagonal space groups instead of using chiral vectors. It is also proposed that the growth model, via a graphene helix, results in a ubiquitous structure of single-wall carbon nanotubes.

Anisotropic metal nanostructures (e.g., Au–Ag, Au–Cu) are emerging for biomedical and catalytic applications in recent years. Herein, we report a modified synthesis of Cu–Au tripod nanocrystals through the controlled nucleation and growth process with judicious purification for photothermal based anticancer therapy. The distribution of nanocrystals in tripod was analyzed by STEM-EDX mapping, indicating the formation of Cu–Au alloy nanocrystals. Theoretical calculations showed the possible formation of alloy structures, that is, Cu3Au, Cu–Au, and CuAu3 and confirmed that their stability in the following order: CuAu3 < Cu–Au < Cu3Au. These stable tripods exhibited a well pronounced photothermal effect as demonstrated by experimental and simulation photothermal studies. Cancer cells treated with nanocrystals upon NIR laser exposure showed promising therapeutic effects.

One of the unsolved fundamental issues of graphene is establishing an appropriate way to discern layers of graphene structures. We report a simple methodology to analyze graphene structures using Raman signals in the range of ∼100 to ∼500 cm comprising clear 118 or 175 cm peaks. We demonstrate that the low-energy signals on Raman spectra of plasma-seeded grown graphene sheets originated from nanocurvature (c) of mono- (175 and 325-500 cm signals) (c ≈ 1 nm) and bilayer (118 cm peak) (c ≈ 2 nm) graphene with Raman simulations, based on Raman radial mode (RM) Eigen vectors. Our RM model provides a standard way of identifying and evaluating graphene structures.