Mildred S. Dresselhaus

It is quite challenging to prepare subnanometer porous materials from traditional porous precursors, and use of supramolecules as carbon sources was seldom reported due to the complex preparation and purification processes. We explore a facile one-pot method to fabricate supramolecular coordination compounds as carbon sources. The resultant CB[6]-derived carbons (CBC) have a high N content of 7.0–22.0%, surface area of 552–861 m2 g–1, and subnano/mesopores. The CBC electrodes have a narrow size distribution at 5.9 Å, and the supercapacitor exhibits an energy density of 117.1 Wh kg–1 and a potential window of over 3.8 V in a two-electrode system in the ionic liquid (MMIMBF4) electrolyte with appropriate cationic (5.8 Å) and anionic (2.3 Å) diameter. This work presents the facile fabrication of novel supermolecule cucurbituril subnanoporous carbon materials and the smart design of “pores and …

Monolayer short period (EuTe) n /(PbTe) 3n superlattices (SL) with alternating magnetic EuTe and non-magnetic PbTe layers were grown by molecular beam epitaxy. For 2D layer-by-layer heteroepitaxial growth, only a narrow regime of growth conditions can be used in order to prevent surface roughening due to strain-induced coherent islanding. For such growth conditions, scanning tunneling microscopy reveals a very smooth surface morphology. The structural properties of the SL samples were studied by x-ray diffraction and transmission electron microscopy. Magnetization measurements show an antiferromagnetic-like phase transition for an even number n of EuTe monolayers and a ferrimagnetic-like transition for odd n. In addition, neutron diffraction data indicate the existence of a long-range interlayer coupling between the magnetic layers across the …

Inter-allotropic transformations of carbon are provided using moderate conditions including alternating voltage pulses and modest temperature elevation. By controlling the pulse magnitude, small-diameter single-walled carbon nanotubes are transformed into larger-diameter single-walled carbon nanotubes, multi-walled carbon nanotubes of different morphologies, and multi-layered graphene nanoribbons.

The stacking and bending of graphene are trivial but extremely powerful agents of control over graphene's manifold physics. By changing the twist angle, one can drive the system over a plethora of exotic states via strong electron correlation, thanks to the moiré superlattice potentials, while the periodic or triaxial strains induce discretization of the band structure into Landau levels without the need for an external magnetic field. We fabricated a hybrid system comprising both the stacking and bending tuning knobs. We have grown the graphene monolayers by chemical vapor deposition, using 12 C and 13 C precursors, which enabled us to individually address the layers through Raman spectroscopy mapping. We achieved the long-range spatial modulation by sculpturing the top layer (13 C) over uniform magnetic nanoparticles (NPs) deposited on the bottom layer (12 C). An atomic force microscopy study revealed …