2017 New's Items

Voltage Dependence of Molecule–Electrode Coupling in Biased Molecular Junctions

Z-F. Liu
J. B. Neaton
2017

Biased interfaces between individual molecules and metallic electrodes are central in many nanoscale devices. A key quantity that governs the nature of the metal–molecule interface is the degree of hybridization between frontier orbitals of the molecule and electrode continuum states. This hybridization leads to the broadening of molecular resonances, a measure of the electronic coupling to the surface. In this work, we present detailed ab initio calculations of the evolution of this electronic coupling for selected frontier orbitals with bias voltage in molecular junctions,...

Oxidative Coupling of Methane (OCM): Effect of Noble Metal (M = Pt, Ir, Rh) Doping on the Performance of Mesoporous Silica MCF-17 Supported MnxOy-Na2WO4 Catalysts

W-C. Liu
W. T. Ralston
G. Melaet
G. A. Somorjai
2017

Noble metal doped M-MnxOy-Na2WO4/SiO2 (M=Pt, Ir, Rh) catalysts were prepared via a wet impregnation method using mesoporous silica MCF-17 as support, and their performance in the oxidative coupling of methane (OCM) was studied in a fixed-bed flow reactor. The reaction was carried out at 750°C under atmospheric pressure with a gas feed composition of CH4:O2=...

Knots Can Impair Protein Degradation by ATP-Dependent Proteases

A. San Martin
P. Rodriguez-Aliaga
J. A. Molina
A. Martin
C. Bustamante
M. Baez
2017

ATP-dependent proteases translocate proteins through a narrow pore for their controlled destruction. However, how a protein substrate containing a knotted topology affects this process remains unknown. Here, we characterized the effects of the trefoil-knotted protein MJ0366 from Methanocaldococcus jannaschii on the operation of the ClpXP protease from Escherichia coli. ClpXP completely degrades MJ0366 when pulling from the C-terminal ssrA-tag. However, when a GFP moiety is appended to the N terminus of MJ0366, ClpXP releases intact GFP with...

A Synthetic Route for Crystals of Woven Structures, Uniform Nanocrystals, and Thin Films of Imine Covalent Organic Frameworks

Y. Zhao
L. Guo
F. Gándara
Y. Ma
Z. Liu
C. Zhu
H. Lyu
C. A. Trickett
E. A. Kapustin
O. Terasaki
O. M. Yaghi
2017

Developing synthetic methodology to crystallize extended covalent structures has been an important pursuit of reticular chemistry. Here, we report a homogeneous synthetic route for imine covalent organic frameworks (COFs) where crystallites emerge from clear solutions without forming amorphous polyimine precipitates. The key feature of this route is the utilization of tert-butyloxycarbonyl group protected amine building blocks, which are deprotected in situ and gradually nucleate the crystalline framework. We demonstrate the utility...

Hydroisomerization of n‑Hexane Using Acidified Metal−Organic Framework and Platinum Nanoparticles

K. Sabyrov
J. Jiang
O. M. Yaghi
G. A. Somorjai
2017

Exceptionally high surface area and ordered nanopores of a metal−organic framework (MOF) are exploited to encapsulate and homogeneously disperse a considerable amount of phosphotungstic acid (PTA). When combined with platinum nanoparticles positioned on the external surface of the MOF, the construct shows a high catalytic activity for hydroisomerization of n-hexane, a reaction requiring hydrogenation/dehydrogenation and moderate to strong Brønsted acid sites. Characterization of the catalytic activity and acidic sites as a function...

Resolving and Controlling Photoinduced Ultrafast Solvation in the Solid State

M. Delor
D. G. McCarthy
B. L. Cotts
T. D. Roberts
R. Noriega
D. D. Devore
S. Mukhopadhyay
T. S. De Vries
N. S. Ginsberg
2017

Solid-state solvation (SSS) is a solid-state analogue of solvent–solute interactions in the liquid state. Although it could enable exceptionally fine control over the energetic properties of solid-state devices, its molecular mechanisms have remained largely unexplored. We use ultrafast transient absorption and optical Kerr effect spectroscopies to independently track and correlate both the excited-state dynamics of an organic emitter and the polarization anisotropy relaxation of a small polar dopant embedded in an amorphous polystyrene matrix. The results demonstrate that the...

Mechanism of Ion Adsorption to Aqueous Interfaces: Graphene/Water vs. Air/Water

D. L. McCaffrey
S. C. Nguyen
S. J. Cox
H. Weller
A. P. Alivisatos
P. L. Geissler
R. J. Saykally
2017

The adsorption of ions to aqueous interfaces is a phenomenon that profoundly influences vital processes in many areas of science, including biology, atmospheric chemistry, electrical energy storage, and water process engineering. Although classical electrostatics theory predicts that ions are repelled from water/hydrophobe (e.g., air/water) interfaces, both computer simulations and experiments have shown that chaotropic ions actually exhibit enhanced concentrations at the air/water interface. Although mechanistic pictures have been developed to explain this counterintuitive...

The Chemistry of CO2 Capture in an Amine-Functionalized Metal− Organic Framework under Dry and Humid Conditions

R. W. Flaig
T. M. O. Popp
A. M. Fracaroli
E. A. Kapustin
M. J. Kalmutzki
R. M. Altamimi
F. Fathieh
J. A. Reimer
O. M. Yaghi
2017

The use of two primary alkylamine functionalities covalently tethered to the linkers of IRMOF-74-III results in a material that can uptake CO2 at low pressures through a chemisorption mechanism. In contrast to other primary amine-functionalized solid adsorbents that uptake CO2 primarily as ammonium carbamates, we observe using solid state NMR that the major chemisorption product for this material is carbamic acid. The equilibrium of reaction products also shifts to ammonium carbamate when water vapor is present; a new ...

Ultralow Thermal Conductivity in All-Inorganic Halide Perovskites

W. Lee
H. Li
A. B. Wong
D. Zhang
M. Lai
Y. Yu
Q. Kong
E. Lin
J. J. Urban
J. C. Grossman
P. Yang
2017

Controlling the flow of thermal energy is crucial to numerous applications ranging from microelectronic devices to energy storage and energy conversion devices. Here, we report ultralow lattice thermal conductivities of solution-synthesized, single-crystalline all-inorganic halide perovskite nanowires composed of CsPbI3 (0.45 ± 0.05 W·m−1·K−1), CsPbBr3 (0.42 ± 0.04 W·m−1·K−1), and CsSnI3 (0.38 ± 0.04 W·m...

Simulation-Based Study of Hybrid Fin/Planar LDMOS Design for FinFET-Based System-on-Chip Technology

Y-T. Wu
F. Ding
D. Connelly
P. Zheng
M-H. Chiang
J. F. Chen
T-J. King Liu
2017

A hybrid fin/planar lateral double-diffused MOSFET (LDMOS) design (hybrid FET) is proposed for the high-voltage input-output devices in a FinFETbased system-on-chip (SoC) technology. 3-D technology computer-aided design simulations show that a planar drift region and a planar drain region are advantageous for higher breakdown voltage (BV) to specific on-state resistance (R on_sp ) ratio (BV 2 /Ron_sp ). By slightly extending the planar portion of the semiconductor active region into the gated channel region...