The growth of large-area bilayer graphene has been of technological importance for graphene electronics. The successful application of graphene bilayers critically relies on the precise control of the stacking orientation, which determines both electronic and vibrational properties of the bilayer system. Toward this goal, an effective characterization method is critically needed to allow researchers to easily distinguish the bilayer stacking orientation (i.e., AB stacked or turbostratic). In this work, we developed such a method to provide facile identification of the stacking orientation by isotope labeling. Raman spectroscopy of these isotopically labeled bilayer samples shows a clear signature associated with AB stacking between layers, enabling rapid differentiation between turbostratic and AB-stacked bilayer regions. Using this method, we were able to characterize the stacking orientation in bilayer graphene grown through Low Pressure Chemical Vapor Deposition (LPCVD) with enclosed Cu foils, achieving almost 70% AB-stacked bilayer graphene. Furthermore, by combining surface sensitive fluorination with such hybrid (12)C/(13)C bilayer samples, we are able to identify that the second layer grows underneath the first-grown layer, which is similar to a recently reported observation.

Trace level identification of explosive molecules are very important not only for security screening but also for the environment and human health. Driven by the need, the current article reports for the first time gold nanocage–graphene oxide hybrid platform for the spectral fingerprint and the trace level identification of RDX and TNT. Reported experimental data using RDX show that the surface-enhanced Raman spectroscopy (SERS) enhancement factor for graphene oxide (GO) attached gold nanocage assembly is 4 orders of magnitude higher than only nanocage, and it is due to the enormous field enhancement for the nanocage assembly. The current article demonstrates that label-free nitro-explosive identification limits using hybrid platform can be as low as 10 fM for TNT and 500 fM for RDX, which indicate that gold nanocage–graphene oxide assembly can be very attractive for a variety of practical applications.

This paper reports for the first time the development of a large-scale SERS substrate from a popcorn-shaped gold nanoparticle-functionalized single walled carbon nanotubes hybrid thin film for the selective and highly sensitive detection of explosive TNT material at a 100 femtomolar (fM) level.

The interaction of gold nanoclusters (Au n , n ) 2, 4, 6, 8, 10, 12) with nucleic acid purine base guanine (G) and the Watson-Crick guanine-cytosine (GC) base pair through the major groove site (N7 site of guanine) of DNA was investigated theoretically. Geometries of complexes were optimized at the density functional theory (DFT) level employing the hybrid B3LYP functional. The 6-31G(d) basis set was used for all atoms except gold, for which the LANL2DZ effective core potential (ECP) was used. Natural population analysis was performed to determine NBO charges. The vertical first ionization potential and electron affinity of guanine and the guanine-cytosine base pair and their complexes with gold nanoclusters were also analyzed. It was revealed that gold clusters interact more strongly with the GC base pair than with isolated guanine. It was found that consequent to the binding of gold nanoclusters a substantial amount of electronic charge was transferred from guanine (or the guanine-cytosine base pair) to the gold clusters. Furthermore, the amount of the electronic charge transferred to the gold cluster was found to be larger for GC-Au n complexes than that in the G-Au n complexes. The vertical ionization potential, electron affinity, and biological significance of the interaction of gold nanoclusters with nucleic acid building blocks have also been discussed.