7 research outputs found
Experimental Characterization of a Theoretically Designed Candidate pâType Transparent Conducting Oxide: Li-Doped Cr<sub>2</sub>MnO<sub>4</sub>
The development of a p-type transparent
conducting oxide (p-TCO)
requires the deliberate design of a wide band gap and high hole conductivity.
Using high-throughput theoretical screening, Cr<sub>2</sub>MnO<sub>4</sub> was earlier predicted to be a p-TCO when doped with lithium.
This constitutes a new class of p-TCO, one based on a tetrahedrally
coordinated d<sup>5</sup> cation. In this study, we examine and experimentally
validate a few central properties of this system. Combined neutron
diffraction and anomalous X-ray diffraction experiments give site
occupancy that supports the theoretical prediction that lithium occupies
the tetrahedral (Mn) site. The lattice parameter of the spinel decreases
with lithium content to a solubility limit of [Li]/([Li] + [Mn]) âŒ
9.5%. Diffuse reflectance spectroscopy measurements show that at higher
doping levels the transparency is diminished, which is attributed
to both the presence of octahedral Mn and the increased hole content.
Room-temperature electrical measurements of doped samples reveal an
increase in conductivity of several orders of magnitude as compared
to that of undoped samples, and high-temperature measurements show
that Cr<sub>2</sub>MnO<sub>4</sub> is a band conductor, as predicted
by theory. The overall agreement between theory and experiment illustrates
the advantages of a theory-driven approach to materials design
Theoretical Prediction and Experimental Realization of New Stable Inorganic Materials Using the Inverse Design Approach
Discovery of new
materials is important for all fields of chemistry.
Yet, existing compilations of all known ternary inorganic solids still
miss many possible combinations. Here, we present an example of accelerated
discovery of the missing materials using the inverse design approach,
which couples predictive first-principles theoretical calculations
with combinatorial and traditional experimental synthesis and characterization.
The compounds in focus belong to the equiatomic (1:1:1) ABX family
of ternary materials with 18 valence electrons per formula unit. Of
the 45 possible VâIXâIV compounds, 29 are missing. Theoretical
screening of their thermodynamic stability revealed eight new stable
1:1:1 compounds, including TaCoSn. Experimental synthesis of TaCoSn,
the first ternary in the TaâCoâSn system, confirmed
its predicted zincblende-derived crystal structure. These results
demonstrate how discovery of new materials can be accelerated by the
combination of high-throughput theoretical and experimental methods.
Despite being made of three metallic elements, TaCoSn is predicted
and explained to be a semiconductor. The band gap of this material
is difficult to measure experimentally, probably due to a high concentration
of interstitial cobalt defects
Expanding the Solvent Chemical Space for Self-Assembly of Dipeptide Nanostructures
Nanostructures composed of short, noncyclic peptides represent a growing field of research in nanotechnology due to their ease of production, often remarkable material properties, and biocompatibility. Such structures have so far been almost exclusively obtained through self-assembly from aqueous solution, and their morphologies are determined by the interactions between building blocks as well as interactions between building blocks and water. Using the diphenylalanine system, we demonstrate here that, in order to achieve structural and morphological control, a change in the solvent environment represents a simple and convenient alternative strategy to the chemical modification of the building blocks. Diphenylalanine (FF) is a dipeptide capable of self-assembly in aqueous solution into needle-like hollow micro- and nanocrystals with continuous nanoscale channels that possess advantageous properties such as high stiffness and piezoelectricity and have so emerged as attractive candidates for functional nanomaterials. We investigate systematically the solubility of diphenylalanine in a range of organic solvents and probe the role of the solvent in the kinetics of self-assembly and the structures of the final materials. Finally, we report the crystal structure of the FF peptide in microcrystalline form grown from MeOH solution at 1 Ă
resolution and discuss the structural changes relative to the conventional materials self-assembled in aqueous solution. These findings provide a significant expansion of the structures and morphologies that are accessible through FF self-assembly for existing and future nanotechnological applications of this peptide. Solvent mediation of molecular recognition and self-association processes represents an important route to the design of new supramolecular architectures deriving their functionality from the nanoscale ordering of their components
Self-Assembly-Mediated Release of Peptide Nanoparticles through Jets Across Microdroplet Interfaces
The release of nanoscale
structures from microcapsules, triggered by changes in the capsule
in response to external stimuli, has significant potential for active
component delivery. Here, we describe an orthogonal strategy for controlling
molecular speciesâ release across oil/water interfaces by modulating
their intrinsic self-assembly state. We show that although the soluble
peptide Boc-FF can be stably encapsulated for days, its self-assembly
into nanostructures triggers jet-like release within seconds. Moreover,
we exploit this self-assembly-mediated release to deliver other molecular
species that are transported as cargo. These results demonstrate the
role of self-assembly in modulating the transport of peptides across
interfaces
Self-Assembly-Mediated Release of Peptide Nanoparticles through Jets Across Microdroplet Interfaces
The release of nanoscale
structures from microcapsules, triggered by changes in the capsule
in response to external stimuli, has significant potential for active
component delivery. Here, we describe an orthogonal strategy for controlling
molecular speciesâ release across oil/water interfaces by modulating
their intrinsic self-assembly state. We show that although the soluble
peptide Boc-FF can be stably encapsulated for days, its self-assembly
into nanostructures triggers jet-like release within seconds. Moreover,
we exploit this self-assembly-mediated release to deliver other molecular
species that are transported as cargo. These results demonstrate the
role of self-assembly in modulating the transport of peptides across
interfaces
Self-Assembly-Mediated Release of Peptide Nanoparticles through Jets Across Microdroplet Interfaces
The release of nanoscale
structures from microcapsules, triggered by changes in the capsule
in response to external stimuli, has significant potential for active
component delivery. Here, we describe an orthogonal strategy for controlling
molecular speciesâ release across oil/water interfaces by modulating
their intrinsic self-assembly state. We show that although the soluble
peptide Boc-FF can be stably encapsulated for days, its self-assembly
into nanostructures triggers jet-like release within seconds. Moreover,
we exploit this self-assembly-mediated release to deliver other molecular
species that are transported as cargo. These results demonstrate the
role of self-assembly in modulating the transport of peptides across
interfaces
Capturing Anharmonicity in a Lattice Thermal Conductivity Model for High-Throughput Predictions
High-throughput,
low-cost, and accurate predictions of thermal
properties of new materials would be beneficial in fields ranging
from thermal barrier coatings and thermoelectrics to integrated circuits.
To date, computational efforts for predicting lattice thermal conductivity
(Îș<sub>L</sub>) have been hampered by the complexity associated
with computing multiple phonon interactions. In this work, we develop
and validate a semiempirical model for Îș<sub>L</sub> by fitting
density functional theory calculations to experimental data. Experimental
values for Îș<sub>L</sub> come from new measurements on SrIn<sub>2</sub>O<sub>4</sub>, Ba<sub>2</sub>SnO<sub>4</sub>, Cu<sub>2</sub>ZnSiTe<sub>4</sub>, MoTe<sub>2</sub>, Ba<sub>3</sub>In<sub>2</sub>O<sub>6</sub>, Cu<sub>3</sub>TaTe<sub>4</sub>, SnO, and InI as well
as 55 compounds from across the published literature. To capture the
anharmonicity in phonon interactions, we incorporate a structural
parameter that allows the model to predict Îș<sub>L</sub> within
a factor of 1.5 of the experimental value across 4 orders of magnitude
in Îș<sub>L</sub> values and over a diverse chemical and structural
phase space, with accuracy similar to or better than that of computationally
more expensive models