Pabitra Choudhury

Reaction of the Basal Plane of Graphite with the Methyl Radical

The reaction of methyl radicals with the basal plane of graphite has been observed to occur with an activation energy of less than 0.3 eV. This reaction is initiated by Li-induced CH3Cl dissociation to produce CH3 radicals on the graphite surface. It is found that ∼3/4 of the methyl radicals remain on the graphite surface up to 700 K at puckered sp(3) carbon sites, while 1/4 of the CH3 radicals participate in CH4 formation and small amounts of C2 and C3 hydrocarbon formation. CH3 radicals become mobile over an activation energy barrier of ∼0.7 eV.

In Situ Observation of Initial Stage in Dielectric Growth and Deposition of Ultrahigh Nucleation Density Dielectric on Two-Dimensional Surfaces.

Several proposed beyond-CMOS devices based on two-dimensional (2D) heterostructures require the deposition of thin dielectrics between 2D layers. However, the direct deposition of dielectrics on 2D materials is challenging due to their inert surface chemistry. To deposit high-quality, thin dielectrics on 2D materials, a flat lying titanyl phthalocyanine (TiOPc) monolayer, deposited via the molecular beam epitaxy, was employed to create a seed layer for atomic layer deposition (ALD) on 2D materials, and the initial stage of growth was probed using in situ STM. ALD pulses of trimethyl aluminum (TMA) and H2O resulted in the uniform deposition of AlOx on the TiOPc/HOPG. The uniformity of the dielectric is consistent with DFT calculations showing multiple reaction sites are available on the TiOPc molecule for reaction with TMA. Capacitors prepared with 50 cycles of AlOx on TiOPc/graphene display a capacitance greater than 1000 nF/cm(2), and dual-gated devices have current densities of 10(-7)A/cm(2) with 40 cycles.

Ni-induced destabilization dynamics of crystalline zinc borohydride

Fundamental understanding of the role of Ni additives in promoting the dehydrogenation mechanism of hydrogen desorption in zinc borohydride [Zn(BH4)2] is a key factor for using this material in hydrogen storage. A systematic theoretical study of the energetics and hydrogen dynamics was carried out to understand this dehydrogenation mechanism. The energetic calculations reveal that Ni substitutes Zn in preference to B. H atoms are pulled toward these doped Ni atoms, which introduce instability via the breaking of multiple B–H bonds in the complex borohydride. The mechanistic understanding gained from this study can be applied to the design of better hydrogen storage materials.

Publisher’s Note: Facile Anhydrous Proton Transport on Hydroxyl Functionalized Graphane [Phys. Rev. Lett. 118 , 186101 (2017)]

This corrects the article DOI: 10.1103/PhysRevLett.118.186101.

Facile Anhydrous Proton Transport on Hydroxyl Functionalized Graphane

Graphane functionalized with hydroxyl groups is shown to rapidly conduct protons under anhydrous conditions through a contiguous network of hydrogen bonds. Density functional theory calculations predict remarkably low barriers to diffusion of protons along a 1D chain of surface hydroxyls. Diffusion is controlled by the local rotation of hydroxyl groups, a mechanism that is very different from that found in 1D water wires in confined nanopores or in bulk water. The proton mean square displacement in the 1D chain was observed to follow Fickian diffusion rather than the expected single-file mobility. A charge analysis reveals that the charge on the proton is essentially equally shared by all hydrogens bound to oxygens, effectively delocalizing the proton.