Polycations that absorb protons in response to the acidification of endosomes can theoretically disrupt these vesicles via the “proton sponge” effect. To exploit this mechanism, we created ...nanoparticles with a segregated core−shell structure for efficient, noncytotoxic intracellular drug delivery. Cross-linked polymer nanoparticles were synthesized with a pH-responsive core and hydrophilic charged shell designed to disrupt endosomes and mediate drug/cell binding, respectively. By sequestering the relatively hydrophobic pH-responsive core component within a more hydrophilic pH-insensitive shell, nontoxic delivery of small molecules and proteins to the cytosol was achieved in dendritic cells, a key cell type of interest in the context of vaccines and immunotherapy.
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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 V–IX–IV 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 Ta–Co–Sn 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.
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To accelerate the design and discovery of novel functional materials, here, p‐type transparent conducting oxides, an inverse design approach is formulated, integrating three steps: i) articulating ...the target properties and selecting an initial pool of candidates based on “design principles”, ii) screening this initial pool by calculating the “selection metrics” for each member, and iii) laboratory realization and more‐detailed theoretical validation of the remaining “best‐of‐class” materials. Following a design principle that suggests using d55 cations for good p‐type conductivity in oxides, the Inverse Design approach is applied to the class of ternary Mn(II) oxides, which are usually considered to be insulating materials. As a result, Cr2MnO4 is identified as an oxide closely following “selection metrics” of thermodynamic stability, wide‐gap, p‐type dopability, and band‐conduction mechanism for holes (no hole self‐trapping). Lacking an intrinsic hole‐producing acceptor defect, Li is further identified as a suitable dopant. Bulk synthesis of Li‐doped Cr2MnO4 exhibits at least five orders of magnitude enhancement of the hole conductivity compared to undoped samples. This novel approach of stating functionality first, then theoretically searching for candidates that merits synthesis and characterization, promises to replace the more traditional non‐systematic approach for the discovery of advanced functional materials.
The Modality 2 inverse design is applied to the search for good p‐type TCO from the well‐documented compounds. Guided by the d5 design principle, 13 Mn(II) ternary oxides from the ICSD are selected and narrowed to two “best‐of‐class” candidates by high‐throughput first‐principles computational screening. In the end, Li‐doped Cr2MnO4 is obtained, as a novel p‐type TCO by design.
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Given the emerging role of oxide spinels as hole conductors, we discuss in this article the traditional vs. new methodologies of determining the type of conduction mechanism at play––localized ...polaronic vs. band‐like transport. Applying (i) traditional small polaron analysis to our in‐situ high temperature four‐point conductivity and thermopower measurements, we previously found an activated mobility, which is indicative of the small polaron mechanism. However, (ii) employing the recent developments in correcting density functional methodologies for hole localization, we predict that the self‐trapped hole is unstable and that Rh2ZnO4 is instead a band conductor with a large effective mass. The hole mobility measured by high‐field room temperature Hall effect also suggests band rather than polaron conduction. The apparent contradiction between the conclusion of the traditional procedure (i) and first‐principles theory (ii) is resolved by taking into account in the previous transport analysis the temperature dependence of the effective density of states, which leads to the result that the mobility is actually temperature‐independent in Rh2ZnO4. Our case study on Rh2ZnO4 illustrates the range of experimental and theoretical approaches at hand to determine whether the transport mechanism of a semiconductor is band or small polaron conduction.
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BFBNIB, DOBA, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UILJ, UKNU, UL, UM, UPUK
Self-doping of cations on the tetrahedral and octahedral sites in spinel oxides creates “anti-site” defects, which results in functional optical, electronic, magnetic, and other materials properties. ...Previously, we divded the III–II spinel family into four doping types (DTs) based on first-principle calculations in order to understand their electrical behavior. Here, we present experimental evidence on two prototype spinels for each major doping type (DT1 and DT4) that test the first principles calculations. For the DT-1 Ga2ZnO4 spinel, we show that the anti-site defects in a stoichiometric film are equal in concentration and compenstate each other, whereas, for nonstoichiometric Cr2MnO4, a representative DT-4 spinel, excess Mn on the tetrahedral sites becomes electrically inactive as the Mn species switch from (III) to (II). The agreement between experiment and theory validates the Doping Rules distilled from the theoretical framework and significantly enhances our understanding of the defect chemistry of spinel oxides.
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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, Cr2MnO4 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 d5 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) ∼ 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 Cr2MnO4 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.
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Transparent conductors combine two generally contradictory physical properties, but there are numerous applications where both functionalities are crucial. Previous searches focused on doping ...wide-gap metal oxides. Focusing instead on the family of 18 valence electron ternary ABX compounds that consist of elements A, B and X in 1:1:1 stoichiometry, we search theoretically for electronic structures that simultaneously lead to optical transparency while accommodating intrinsic defect structures that produce uncompensated free holes. This leads to the prediction of a stable, never before synthesized TaIrGe compound made of all-metal heavy atom compound. Laboratory synthesis then found it to be stable in the predicted crystal structure and p-type transparent conductor with a strong optical absorption peak at 3.36 eV and remarkably high hole mobility of 2,730 cm(2) V(-1) s(-1) at room temperature. This methodology opens the way to future searches of transparent conductors in unexpected chemical groups.
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