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At least 1,693 records · Page 94

DIPS-Plus: The enhanced database of interacting protein structures for interface prediction

Abstract In this work, we expand on a dataset recently introduced for protein interface prediction (PIP), the Database of Interacting Protein Structures (DIPS), to present DIPS-Plus, an enhanced, feature-rich dataset of 42,112 complexes for machine learning of protein interfaces. While the original DIPS dataset contains only the Cartesian coordinates for atoms contained in the protein complex along with their types, DIPS-Plus contains multiple residue-level features including surface proximities, half-sphere amino acid compositions, and new profile hidden Markov model (HMM)-based sequence features for each amino acid, providing researchers a curated feature bank for training protein interface prediction methods. We demonstrate through rigorous benchmarks that training an existing state-of-the-art (SOTA) model for PIP on DIPS-Plus yields new SOTA results, surpassing the performance of some of the latest models trained on residue-level and atom-level encodings of protein complexes to date.

59 BASIC BIOLOGICAL SCIENCES↗

Silicon Surface Tethered Polymer as Artificial Solid Electrolyte Interface

Here, we have developed a proof of concept electrode design to covalently graft poly(methyl methacrylate) brushes directly to silicon thin film electrodes via surface-initiated atom transfer radical polymerization. This polymer layer acts as a stable artificial solid electrolyte interface that enables surface passivation despite large volume changes during cycling. Thin polymer layers (75 nm) improve average first cycle coulombic efficiency from 62.4% in bare silicon electrodes to 76.3%. Average first cycle reversible capacity was improved from 3157 to 3935 mAh g -1 , and average irreversible capacity was reduced from 2011 to 1020 mAh g -1 . Electrochemical impedance spectroscopy performed on silicon electrodes showed that resistance from solid electrolyte interface formation increased from 79 to 1508 Ω in untreated silicon thin films over 26 cycles, while resistance growth was lower – from 98 to 498 Ω – in silicon films functionalized with PMMA brushes. The lower increase suggests enhanced surface passivation and lower electrolyte degradation. This work provides a pathway to develop artificial solid electrolyte interfaces synthesized under controlled reaction conditions.

36 MATERIALS SCIENCE↗

Critical role of orbital hybridization in the Dzyaloshinskii-Moriya interaction of magnetic interfaces

Dzyaloshinskii-Moriya interaction (DMI), an interfacial spin-orbit coupling (ISOC)-related effect, has become foundational for spintronic research and magnetic memory and computing technologies. However, the underlying mechanism of DMI, including the quantitative role of ISOC, has remained a long-standing unsettled problem due to the great challenge in quantifying and widely tuning ISOC strength in a strong DMI material system. Here, we find that DMI, ISOC, and orbital hybridization at the model magnetic interface Au 1-x Pt x /Co can be quantified and tuned significantly at the same time through the composition of the Au 1-x Pt x , without varying the bulk SOC and the electronegativity. From this ability, we establish that the widespread expectation that DMI should scale in linear proportion to ISOC breaks down at the Au 1-x Pt x /Co interface where degree of orbital hybridization varies with the Au 1-x Pt x composition and that the unexpected DMI behaviors can be understood well by the critical role of orbital hybridization. Our study provides a quantitative frame for comprehensively understanding interfacial DMI of various magnetic interfaces and establishes orbital hybridization as a new degree of freedom for controlling DMI in high-performance chiral domain wall/skyrmion devices and ultrafast magnetic tunnel junctions.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

Atomic-scale manipulation of buried graphene–silicon carbide interface by local electric field

Abstract Precision of scanning tunneling microscopy (STM) enables control of matter at scales of single atoms. However, transition from atomic-scale manipulation strategies to practical devices encounters fundamental problems in protection of the designer structures formed atop the surface. In this context, STM manipulation of subsurface structures on technologically relevant materials is encouraging. Here, we propose a material platform and protocols for precise manipulation of a buried graphene interface. We show that an electric field from the STM tip reversibly controls breaking and restoring of covalent bonds between the graphene buffer layer and the SiC substrate. The process involves charge redistribution at the atomically sharp interface plane under the epitaxial graphene layer(s). This buried manipulation platform is laterally defined by unit cells from the corresponding (6×6) SiC moiré lattice of the epitaxial graphene. Local and reversible electric-field-induced patterning of graphene heterostructures from the bottom interface creates an alternative architecture concept for their applications.

74 ATOMIC AND MOLECULAR PHYSICS↗

Modeling the electrical double layer at solid-state electrochemical interfaces

Models of the electrical double layer (EDL) at electrode/liquid-electrolyte interfaces no longer hold for all-solid-state electrochemistry. Here we show a more general model for the EDL at a solid-state electrochemical interface based on the Poisson–Fermi–Dirac equation. By combining this model with density functional theory predictions, the interconnected electronic and ionic degrees of freedom in all-solid-state batteries, including the electronic band bending and defect concentration variation in the space-charge layer, are captured self-consistently. Along with a general mathematical solution, the EDL structure is presented in various materials that are thermodynamically stable in contact with a lithium metal anode: the solid electrolyte Li 7 La 3 Zr 2 O 12 (LLZO) and the solid interlayer materials LiF, Li 2 O and Li 2 CO 3 . Here, the model further allows design of the optimum interlayer thicknesses to minimize the electrostatic barrier for lithium ion transport at relevant solid-state battery interfaces.

25 ENERGY STORAGE↗

Atomic and electronic structure of Lomer dislocations at CdTe bicrystal interface

Extended defects are of considerable importance in determining the electronic properties of semiconductors, especially in photovoltaics (PVs), due to their effects on electron-hole recombination. We employ model systems to study the effects of dislocations in CdTe by constructing grain boundaries using wafer bonding. Atomic-resolution scanning transmission electron microscopy (STEM) of a [1–10]/ (110) 4.8° tilt grain boundary reveals that the interface is composed of three distinct types of Lomer dislocations. Geometrical phase analysis is used to map strain fields, while STEM and density functional theory (DFT) modeling determine the atomic structure at the interface. The electronic structure of the dislocation cores calculated using DFT shows significant mid-gap states and different charge-channeling tendencies. Cl-doping is shown to reduce the midgap states, while maintaining the charge separation effects. In conclusion, this report offers novel avenues for exploring grain boundary effects in CdTe-based solar cells by fabricating controlled bicrystal interfaces and systematic atomic-scale analysis.

36 MATERIALS SCIENCE↗

What determines the interfacial configuration of Nb/Al2O3 and Nb/MgO interface

Nb films are deposited on single crystal Al 2 O 3 (1120) and MgO(111) substrates by e-beam evaporation technique. Structure of Nb films and orientation relationships (ORs) of Nb/Al 2 O 3 and Nb/MgO interface are studied and compared by the combination of experiments and simulations. The experiments show that the Nb films obtain strong (110) texture, and the Nb film on Al 2 O 3 (1120) substrate shows a higher crystalline quality than that on MgO(111) substrate. First principle calculations show that both the lattice mismatch and the strength of interface bonding play major roles in determining the crystalline perfection of Nb films and ORs between Nb films and single crystal ceramic substrates. The fundamental mechanisms for forming the interfacial configuration in terms of the lattice mismatch and the strength of interface bonding are discussed.

36 MATERIALS SCIENCE↗

Capturing the transient species at the electrode–electrolyte interface by in situ dynamic molecular imaging

The electrochemical interface between the solid electrode and liquid electrolyte has long been studied because of its importance in electrical energy storage, material synthesis, catalysis, and energy conversions.1 However, such interfaces are complex and extremely difficult to observe directly and are poorly under-stood due to lack of true in situ tools.2 Although electrochemical techniques have been widely used to investigate such interfaces, they are based on macroscopic models or current changes that could not provide direct ionic and molecular information of the interfacial structure. Many in situ and ex situ spectroscopy and microscopy techniques have been used to study the solid–liquid (s–l) interface.3,4 In situ TEM in sealed liquid cells has notably become a popular choice to provide structural information of s–l at the atomic level.5,6 However, real-time spatial mapping of the ionic and molecular intermediate species at the dynamic inter-face still remains a key challenge.

Environmental Molecular Sciences Laboratory↗

Beyond the staple motif: a new order at the thiolate–gold interface

Staple motifs in the form of –RS(AuSR) x – (x = 1, 2, 3, etc.) are the most common structural feature at the interface of the thiolate-protected gold nanoclusters, Au n (SR) m . However, the recently solved structure of Au 92 (SR) 44 , in which the facets of the Au 84 core are protected mainly by the bridging thiolates, challenges the staple hypothesis. Herein, we explore the surface sensitivity of the thiolate–gold interface from first principles density functional theory. We find that the interfacial structures of thiolates on gold are surface sensitive: while a staple motif (such as –RS–Au–SR–) is preferred on Au(111), a bridging motif (–RS–) is preferred on Au(100) and Au(110). We show that this surface sensitivity is closely related to the coordination number of the surface Au atom on the different surfaces. We further confirm the preference of the bridging motif for self-assembled monolayers of two different ligands (methylthiolate and 4-tert-butylbenzenethiolate) on Au(100). With this surface sensitivity, we categorize the structure-known Au n (SR) m clusters into three groups: (1) no bridging; (2) ambiguous bridging; (3) distinct bridging. We further employ the surface sensitivity of the thiolate–Au interface to predict the protecting motifs of face-centered cubic (fcc) gold nanoparticles of different shapes. In conclusion, our study provides a unifying view of the Au n (SR) m structures with guidelines for structure predictions for larger Au n (SR) m clusters of a fcc core.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

The role of the CeO 2 /BiVO 4 interface in optimized Fe–Ce oxide coatings for solar fuels photoanodes

Solar fuel generators entail a high degree of materials integration, and efficient photoelectrocatalysis of the constituent reactions hinges upon the establishment of highly functional interfaces. Our recent application of high throughput experimentation to interface discovery for solar fuels photoanodes has revealed several surprising and promising mixed-metal oxide coatings for BiVO 4 . Furthermore, when using sputter deposition of composition and thickness gradients on a uniform BiVO 4 film, we systematically explore photoanodic performance as a function of the composition and loading of Fe–Ce oxide coatings. This combinatorial materials integration study not only enhances the performance of this new class of materials but also identifies CeO 2 as a critical ingredient that merits detailed study. A heteroepitaxial CeO 2 (001)/BiVO4(010) interface is identified in which Bi and V remain fully coordinated to O such that no surface states are formed. Ab initio calculations of the integrated materials and inspection of the electronic structure reveals mechanisms by which CeO 2 facilitates charge transport while mitigating deleterious recombination. Our results support the observations that addition of Ce to BiVO 4 coatings greatly enhances photoelectrocatalytic activity, providing an important strategy for developing a scalable solar fuels technology.

14 SOLAR ENERGY↗

Interface engineering for a rational design of poison-free bimetallic CO oxidation catalysts

We use density functional theory calculations of Pt@Cu core@shell nanoparticles (NPs) to design bifunctional poison-free CO oxidation catalysts. By calculating the adsorption chemistry under CO oxidation conditions, we find that the Pt@Cu NPs will be active for CO oxidation with resistance to CO-poisoning. The CO oxidation pathway at the Pt–Cu interface is determined on the Pt NP covered with a full- and partial-shell of Cu. The exposed portion of the Pt core preferentially binds CO and the Cu shell binds O2, supplying oxygen for the reaction. The Pt–Cu interface provides CO-oxidation sites that are not poisoned by either CO or O2. Additional computational screening shows that this separation of reactant binding sites is possible for several other core@shell NPs. Our results indicate that the metal–metal interface within a single NP can be optimized for design of bifunctional catalytic systems with improved performance.

Shin, Kihyun↗

Coarse-grained molecular dynamics simulation of the interface behaviour and self-assembly of CTAB cationic surfactants

Here, we study the behaviour at interfaces and the micelle self-assembly of a cationic surfactant (CTAB) by Molecular Dynamics (MD) simulations of coarse-grained models. We consider both the standard (with explicit water) Martini force field and the implicit solvent version of the Martini force field (Dry Martini). First, we study the behaviour of CTAB at a water/vacuum interface, at a water/organic solvent interface and in a pre-assembled CTAB micelle using both standard and Dry Martini and all-atomic simulations. Our results indicate that there are significant quantitative differences between the predictions of the two models. Interestingly, implicit solvent simulations with Dry Martini show good quantitative agreement with all-atomic MD simulations, better than explicit solvent Martini MD simulations. The computational efficiency of the Martini and Dry Martini models allowed us to study the self-assembly of CTAB in a large system with many micelles. We observe the self-assembly of CTAB into micelles and also the exchange of CTAB molecules between micelles by events such as micelle fusion and fission which are difficult to observe in all-atomic MD simulations due to the time and length scales involved. Under the studied conditions, both Martini models predict a rather different self-assembly behaviour. The standard Martini model predicts a final equilibrium state with spherical micelles with an average size of ≈70 CTAB molecules. In contrast, the Dry Martini model predicts the formation of large tubular micelles with ≈330 CTAB molecules. Compared with experiments, standard Martini and Dry Martini underestimate and overestimate, respectively, the micelle size.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Lifetime and linewidth of individual quantum dots interfaced with graphene

Here, we report on luminescence lifetimes and linewidths from an array of individual quantum dots (QDs) that were either interfaced with graphene surface guides or dispersed on aluminum electrodes. The observed fluorescence quenching is consistent with screening by charge carriers. Fluorescence quenching is typically mentioned as a sign that chromophores are interfacing with a conductive surface (metal or graphene); we find that the QDs interfaced with the metal film exhibit shortened lifetime and line-broadening but not necessarily fluorescence quenching as the latter may be impacted by molecular concentration, reflectivity and conductor imperfections. We also comment on angle-dependent lifetime measurements, which we postulate depend on the specifics of the local density-of-states involved.

77 NANOSCIENCE AND NANOTECHNOLOGY↗

Atomic layer deposition for membrane interface engineering

In many applications, interfaces govern the performance of membranes. Structure, chemistry, electrostatics, and other properties of interfaces can dominate the selectivity, flux, fouling resistance, and other critical aspects of membrane functionality. Control over membrane interfacial properties, therefore, is a powerful means of tailoring performance. In this minireview, we discuss the application of atomic layer deposition (ALD) and related techniques in the design of novel membrane interfaces. We discuss recent literature in which ALD is used to 1) modify the surface chemistry and interfacial properties of membranes, 2) tailor the pore sizes and separation characteristics of membranes, and 3) enable novel advanced functional membranes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Correlation at two-dimensional charge-transfer FeSe interface

The charge transfer and spin coupling effects are explored at the interface of two-dimensional (2D) superconducting FeSe nanosheets and molecular photochromic potassium-7,7,8,8-tetracyanoquinodimethane (KTCNQ). Light-induced conductivity in 2D FeSe nanosheets is enhanced by the electron doping from KTCNQ by the destabilized spin-Peierls phase through their interface. Furthermore, the spin coupling at the interface of FeSe and KTCNQ shifts the dimerization transition temperature of KTCNQ. Our results suggest 2D exfoliated FeSe nanosheets as a versatile strongly correlated platform for the study of interfacial electron doping and spin coupling.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Giant spin Seebeck effect through an interface organic semiconductor

Interfacing an organic semiconductor C 60 with a non-magnetic metallic thin film (Cu or Pt) has created a novel heterostructure that is ferromagnetic at ambient temperature, while its interface with a magnetic metal (Fe or Co) can tune the anisotropic magnetic surface property of the material. Here, we demonstrate that sandwiching C60 in between a magnetic insulator (Y 3 Fe 5 O 12 :YIG) and a non-magnetic, strong spin–orbit metal (Pt) promotes highly efficient spin current transport via the thermally driven spin Seebeck effect (SSE). Experiments and first principles calculations consistently show that the presence of C 60 reduces significantly the conductivity mismatch between YIG and Pt and the surface perpendicular magnetic anisotropy of YIG, giving rise to enhanced spin mixing conductance across YIG/C 60 /Pt interfaces. As a result, a 600% increase in the SSE voltage (V LSSE ) has been realized in YIG/C 60 /Pt relative to YIG/Pt. Temperature-dependent SSE voltage measurements on YIG/C 60 /Pt with varying C 60 layer thicknesses also show an exponential increase in V LSSE at low temperatures below 200 K, resembling the temperature evolution of spin diffusion length of C 60 . Our report emphasizes the important roles of the magnetic anisotropy and the spin diffusion length of the intermediate layer in the SSE in YIG/C 60 /Pt structures, providing a new pathway for developing novel spin-caloric materials.

36 MATERIALS SCIENCE↗

Designing nanoparticle interfaces for inner-sphere catalysis

Interfaces are an intrinsic component of nanoparticle catalysts and play a critical role in directing their function. Our understanding of the complexity of the nanoparticle interface and how to manipulate it at the molecular level has advanced significantly in recent years. Given this, attention is shifting towards the creation of designer nanoparticle interfaces that impact the activity and direct the mechanisms of inner-sphere catalytic reactions. In this perspective, we seek to highlight and contextualize these efforts. First, methods to alter nanoparticle surfaces are presented, including annealing and plasma treating, as well as more mild chemical treatments, including ligand exchange, etching, and addition (via covalent functionalization). Then interfacial chemistry developed to alter catalytic activity, selectivity, and reaction environment will be highlighted. Finally, we look forward to the challenges that remain to be overcome for realizing the true potential of colloidal nanoparticle catalysis.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Charging-driven coarsening and melting of a colloidal nanoparticle monolayer at an ionic liquid–vacuum interface

In this work, we induce and investigate the coarsening and melting dynamics of an initially static nanoparticle colloidal monolayer at an ionic liquid–vacuum interface, driven by a focused, scanning electron beam. Coarsening occurs through grain interface migration and larger-scale motions such as grain rotations, often facilitated by sliding dislocations. The progressive decrease in area fraction that drives melting of the monolayer is explained using an electrowetting model whereby particles at the interface are solvated once their accumulating charge recruits sufficient counterions to subsume the particle. Subject to stochastic particle removal from the monolayer, melting is recapitulated in simulations with a Lennard-Jones potential. This new driving mechanism for colloidal systems, whose dynamical timescales we show can be controlled with the accelerating voltage, opens the possibility to manipulate particle interactions dynamically without need to vary particle intrinsic properties or surface treatments. Furthermore, the decrease in particle size availed by electron imaging presents opportunities to observe force and time scales in a lesser-explored regime intermediate between typical colloidal and molecular systems.

36 MATERIALS SCIENCE↗