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Lithium-ion batteries are the leading energy storage technology for portable electronics and vehicle electrification. However, demands for enhanced energy density, safety, and scalability necessitate solid-state alternatives to traditional liquid electrolytes. Moreover, the rapidly increasing utilization of lithium-ion batteries further requires that next-generation electrolytes are derived from earth-abundant raw materials in order to minimize supply chain and environmental concerns. Toward these ends, clay-based nanocomposite electrolytes hold significant promise since they utilize earth-abundant materials that possess superlative mechanical, thermal, and electrochemical stability, which suggests their compatibility with energy-dense lithium metal anodes. Despite these advantages, nanocomposite electrolytes rarely employ kaolinite, the most abundant variety of clay, due to strong interlayer interactions that have historically precluded efficient exfoliation of kaolinite. Overcoming this limitation, here we demonstrate a scalable liquid-phase exfoliation process that produces kaolinite nanoplatelets (KNPs) with high gravimetric surface area, thus enabling the formation of mechanically robust nanocomposites. In particular, KNPs are combined with a succinonitrile (SN) liquid electrolyte to form a nanocomposite gel electrolyte with high room-temperature ionic conductivity (1 mS cm–1), stiff storage modulus (>10 MPa), wide electrochemical stability window (4.5 V vs Li/Li+), and excellent thermal stability (>100 °C). The resulting KNP-SN nanocomposite gel electrolyte is shown to be suitable for high-rate rechargeable lithium metal batteries that employ high-voltage LiNi0.8Co0.15Al0.05O2(NCA) cathodes. While the primary focus here is on solid-state batteries, our strategy for kaolinite liquid-phase exfoliation can serve as a scalable manufacturing platform for a wide variety of other kaolinite-based nanocomposite applications.

High-entropy semiconductors are now an important class of materials widely investigated for thermoelectric applications. Understanding the impact of chemical and structural heterogeneity on transport properties in these compositionally complex systems is essential for thermoelectric design. In this work, we uncover the polar domain structures in the high-entropy PbGeSnSe1.5Te1.5system and assess their impact on thermoelectric properties. We found that polar domains induced by crystal symmetry breaking give rise to well-structured alternating strain fields. These fields effectively disrupt phonon propagation and suppress the thermal conductivity. We demonstrate that the polar domain structures can be modulated by tuning crystal symmetry through entropy engineering in PbGeSnAgxSbxSe1.5+xTe1.5+x. Incremental increases in the entropy enhance the crystal symmetry of the system, which suppresses domain formation and loses its efficacy in suppressing phonon propagation. As a result, the room-temperature lattice thermal conductivity increases from ?L= 0.63 Wm–1K–1(x= 0) to 0.79 Wm–1K–1(x= 0.10). In the meantime, the increase in crystal symmetry, however, leads to enhanced valley degeneracy and improves the weighted mobility from µw= 29.6 cm2V–1s–1(x= 0) to 35.8 cm2V–1s–1(x= 0.10). As such, optimal thermoelectric performance can be achieved through entropy engineering by balancing weighted mobility and lattice thermal conductivity. This work, for the first time, studies the impact of polar domain structures on thermoelectric properties, and the developed understanding of the intricate interplay between crystal symmetry, polar domains, and transport properties, along with the impact of entropy control, provides valuable insights into designing GeTe-based high-entropy thermoelectrics.

Mixed metal oxyhalides are an exciting class of photocatalysts, capable of the sustainable generation of fuels and remediation of pollutants with solar energy. Bismuth oxyhalides of the types Bi4MO8X (M = Nb and Ta; X = Cl and Br) and Bi2AO4X (A = most lanthanides; X = Cl, Br, and I) have an electronic structure that imparts photostability, as their valence band maxima (VBM) are composed of O 2p orbitals rather than X np orbitals that typify many other bismuth oxyhalides. Here, flux-based synthesis of intergrowth Bi4NbO8Cl–Bi2GdO4Cl is reported, testing the hypothesis that both intergrowth stoichiometry and M identity serve as levers toward tunable optoelectronic properties. X-ray scattering and atomically resolved electron microscopy verify intergrowth formation. Facile manipulation of the Bi4NbO8Cl-to-Bi2GdO4Cl ratio is achieved with the specific ratio influencing both the crystal and electronic structures of the intergrowths. This compositional flexibility and crystal structure engineering can be leveraged for photocatalytic applications, with comparisons to the previously reported Bi4TaO8Cl–Bi2GdO4Cl intergrowth revealing how subtle structural and compositional features can impact photocatalytic materials.

Platinum (Pt) thin films are useful in applications requiring high-conductivity electrodes with excellent thermal and chemical stability. Ultrasmooth and epitaxial Pt thin films with single-crystalline domains have the added benefit of providing ideal templates for the subsequent growth of heteroepitaxial structures. Here, we grow epitaxial Pt (111) electrodes (ca. 30 nm thick) on sapphire (α-Al2O3(0001)) substrates with pulsed laser deposition. This versatile technique allows control of the growth process and fabrication of films with carefully tailored parameters. X-ray scattering, atomic-force microscopy, and electron microscopy provide structural characterization of the films. Various gaseous atmospheres and temperatures were explored to achieve epitaxial growth of films with low roughness. A two-step (500 °C/300 °C) growth process was developed, yielding films with improved epitaxy without compromising roughness. The resulting films possess ultrasmooth interfaces (<3 Å) and high electrical conductivity (6.9 × 106S/m). Finally, Pt films were used as current collectors and templates to grow lithium manganese oxide (LiMn2O4(111)) epitaxial thin films, a cathode material used in Li-ion batteries. Using a solid-state ionogel electrolyte, the films were highly stable when electrochemically cycled in the 3.5–4.3 V vs Li/Li+range.

Compressive strain engineering improves perovskite stability. Two-dimensional compressive strain along the in-plane direction can be applied to perovskites through the substrate; however, this in-plane strain results in an offsetting tensile strain perpendicular to the substrate, linked to the positive Poisson ratio of perovskites. Substrate-induced strain engineering has not yet resulted in state-of-the-art operational stability. Here, we seek instead to implement hydrostatic strain in perovskites by embedding lattice-mismatched perovskite quantum dots (QDs) into a perovskite matrix. QD-in-matrix perovskites show a homogeneously strained lattice as evidenced by grazing-incidence X-ray diffraction. We fabricate mixed-halide wide-band-gap (Eg; 1.77 eV) QD-in-matrix perovskite solar cells that maintain >90% of their initial power conversion efficiency (PCE) after 200 h of one-sun operation at the maximum power point (MPP), a significant improvement relative to matrix-only devices, which lose 10% (relative) of their initial PCE after 5 h of MPP tracking.

Scanning transmission electron microscopy tomography with ChromEM staining (ChromSTEM), has allowed for the three-dimensional study of genome organization. By leveraging convolutional neural networks and molecular dynamics simulations, we have developed a denoising autoencoder (DAE) capable of postprocessing experimental ChromSTEM images to provide nucleosome-level resolution. Our DAE is trained on synthetic images generated from simulations of the chromatin fiber using the 1-cylinder per nucleosome (1CPN) model of chromatin. We find that our DAE is capable of removing noise commonly found in high-angle annular dark field (HAADF) STEM experiments and is able to learn structural features driven by the physics of chromatin folding. The DAE outperforms other well-known denoising algorithms without degradation of structural features and permits the resolution of α-tetrahedron tetranucleosome motifs that induce local chromatin compaction and mediate DNA accessibility. Notably, we find no evidence for the 30 nm fiber, which has been suggested to serve as the higher-order structure of the chromatin fiber. This approach provides high-resolution STEM images that allow for the resolution of single nucleosomes and organized domains within chromatin dense regions comprising of folding motifs that modulate the accessibility of DNA to external biological machinery.

We investigate the usage of polyelectrolyte complex materials for water remediation purposes, specifically their ability to remove nanoplastics from water, on which there is currently little to no prior research. We demonstrate that oppositely charged random copolymers are effective at quantitatively removing nanoplastic contamination from aqueous solution. The mechanisms underlying this remediation ability are explored through computational simulations, with corroborating quartz crystal microbalance adsorption experiments. We find that hydrophobic nanostructures and interactions likely play an important role.

The carbon dioxide and carbon monoxide electroreduction reactions, when powered using low-carbon electricity, offer pathways to the decarbonization of chemical manufacture1,2. Copper (Cu) is relied on today for carbon–carbon coupling, in which it produces mixtures of more than ten C2+chemicals3–6: a long-standing challenge lies in achieving selectivity to a single principal C2+product7–9. Acetate is one such C2compound on the path to the large but fossil-derived acetic acid market. Here we pursued dispersing a low concentration of Cu atoms in a host metal to favour the stabilization of ketenes10—chemical intermediates that are bound in monodentate fashion to the electrocatalyst. We synthesize Cu-in-Ag dilute (about 1 atomic per cent of Cu) alloy materials that we find to be highly selective for acetate electrosynthesis from CO at high *CO coverage, implemented at 10 atm pressure. Operando X-ray absorption spectroscopy indicates in situ-generated Cu clusters consisting of <4 atoms as active sites. We report a 12:1 ratio, an order of magnitude increase compared to the best previous reports, in the selectivity for acetate relative to all other products observed from the carbon monoxide electroreduction reaction. Combining catalyst design and reactor engineering, we achieve a CO-to-acetate Faradaic efficiency of 91% and report a Faradaic efficiency of 85% with an 820-h operating time. High selectivity benefits energy efficiency and downstream separation across all carbon-based electrochemical transformations, highlighting the importance of maximizing the Faradaic efficiency towards a single C2+product11.

We have developed a new method for synthesizing mono- and bimetallic two-dimensional selenophosphates by using a reactive flux technique with powder precursors dissolved in a P2Se5melt. This method allows us to bypass the difficulties commonly encountered in synthesizing these materials. M2P2Se6(M = Mn, Fe, Cr, Cd, Mg, and Zn) and bimetallic MM′P2Se6(M = Cu, Ag; M′ = Cr, In) powders were synthesized over 60 h using a P2Se5reactive flux. As a further demonstration of potential optimization, Mn2P2Se6powder with minor MnSe impurity was synthesized in 30 min. Reactions of Mn and Cr in P2Se5flux were analyzed in situ using variable-temperature powder X-ray diffraction to investigate the formation reaction pathways, suggesting single-step formation of Cr2P2Se6at 775 °C and formation of Mn2P2Se6at 575 °C through an intermediate MnSe phase. Follow-up experimental syntheses generated crystals of the monometallic family M2P2Se6(M = Mn, Fe, and Cd) and bimetallic family MM′P2Se6(M = Li, Cu, Ag; M′ = Cr, In) with area dimensions of several square millimeters using heating profiles of just over 60 h. The homogeneity of bimetallic selenophosphates MM′P2Se6was confirmed using scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Rietveld refinement. The crystallinity of the selected materials was characterized by transmission electron microscopy and atomic force microscopy measurements. The work functions of flakes were determined and ranged from 5.25 to 5.72 eV.

Entropy-engineered materials are garnering considerable attention owing to their excellent mechanical and transport properties, such as their high thermoelectric performance. However, understanding the effect of entropy on thermoelectrics remains a challenge. In this study, we used the PbGeSnCdxTe3+xfamily as a model system to systematically investigate the impact of entropy engineering on its crystal structure, microstructure evolution, and transport behavior. We observed that PbGeSnTe3crystallizes in a rhombohedral structure at room temperature with complex domain structures and transforms into a high-temperature cubic structure at ∼373 K. By alloying CdTe with PbGeSnTe3, the increased configurational entropy lowers the phase-transition temperature and stabilizes PbGeSnCdxTe3+xin the cubic structure at room temperature, and the domain structures vanish accordingly. The high-entropy effect results in increased atomic disorder and consequently a low lattice thermal conductivity of 0.76 W m–1K–1in the material owing to enhanced phonon scattering. Notably, the increased crystal symmetry is conducive to band convergence, which results in a high-power factor of 22.4 μW cm–1K–1. As a collective consequence of these factors, a maximum ZTof 1.63 at 875 K and an average ZTof 1.02 in the temperature range of 300–875 K were obtained for PbGeSnCd0.08Te3.08. This study highlights that the high-entropy effect can induce a complex microstructure and band structure evolution in materials, which offers a new route for the search for high-performance thermoelectrics in entropy-engineered materials.

The class I–III–VI2diamondoid compounds with tetrahedral bonding are important semiconductors widely applied in optoelectronics. Understanding their heat transport properties and developing an effective method to predict the diamondoid solid solutions’ thermal conductivity will help assess their impact as thermoelectrics. In this work, we investigated in detail the heat transport properties of CuGa1–xInxTe2and Cu1–xAgxGaTe2and found that in the Ag-alloyed solid solutions, the Ag atom off-centering effect results in crystallographic distortion and extra strong acoustic–optical phonon scattering and an extremely low lattice thermal conductivity. Moreover, we integrate the alloy scattering and the off-centering effect with the crystallographic distortion parameter to develop a modified Klemens model that predicts the thermal conductivity of diamondoid solid solutions. Finally, we demonstrate that Cu1–xAgxGaTe2solid solutions are promising p-type thermoelectric materials, with a maximum ZTof 1.23 at 850 K for Cu0.58Ag0.4GaTe2.

The tunable bandgaps and facile fabrication of perovskites make them attractive for multi-junction photovoltaics1,2. However, light-induced phase segregation limits their efficiency and stability3–5: this occurs in wide-bandgap (>1.65 electron volts) iodide/bromide mixed perovskite absorbers, and becomes even more acute in the top cells of triple-junction solar photovoltaics that require a fully 2.0-electron-volt bandgap absorber2,6. Here we report that lattice distortion in iodide/bromide mixed perovskites is correlated with the suppression of phase segregation, generating an increased ion-migration energy barrier arising from the decreased average interatomic distance between the A-site cation and iodide. Using an approximately 2.0-electron-volt rubidium/caesium mixed-cation inorganic perovskite with large lattice distortion in the top subcell, we fabricated all-perovskite triple-junction solar cells and achieved an efficiency of 24.3 per cent (23.3 per cent certified quasi-steady-state efficiency) with an open-circuit voltage of 3.21 volts. This is, to our knowledge, the first reported certified efficiency for perovskite-based triple-junction solar cells. The triple-junction devices retain 80 per cent of their initial efficiency following 420 hours of operation at the maximum power point.

A library of compositionally and structurally well-defined Au–Cu alloy nanocrystals has been prepared via scanning probe block copolymer lithography. These libraries not only allow one to map compositional and structure space but also the conditions (e.g., cooling rate) required to access specific structures. This approach enabled the realization of a previously unobserved architecture, an intermetallic nanoprism, that is a consequence of hierarchical atom stacking. These structures exhibit distinctive diffraction patterns characterized by non-integer-index, forbidden spots, which serve as a diagnostic indicator of such structures. Inspection of the library’s pseudospherical particles reveals a high-strain cubic–tetragonal interfacial configuration in the outer regions of the intermetallic nanocrystals. Since it is costly and time-consuming to explore the nanomaterials phase space via conventional wet-chemistry, this parallel kinetic-control approach, which relies on substrate- and positionally isolated particles, may lead to the rapid discovery of complex nanocrystals that may prove useful in applications spanning catalysis and plasmonic sensing.

Although tremendous advances have been made in preparing porous crystals from molecular precursors1,2, there are no general ways of designing and making topologically diversified porous colloidal crystals over the 10–1,000 nm length scale. Control over porosity in this size range would enable the tailoring of molecular absorption and storage, separation, chemical sensing, catalytic and optical properties of such materials. Here, a universal approach for synthesizing metallic open-channel superlattices with pores of 10 to 1,000 nm from DNA-modified hollow colloidal nanoparticles (NPs) is reported. By tuning hollow NP geometry and DNA design, one can adjust crystal pore geometry (pore size and shape) and channel topology (the way in which pores are interconnected). The assembly of hollow NPs is driven by edge-to-edge rather than face-to-face DNA–DNA interactions. Two new design rules describing this assembly regime emerge from these studies and are then used to synthesize 12 open-channel superlattices with control over crystal symmetry, channel geometry and topology. The open channels can be selectively occupied by guests of the appropriate size and that are modified with complementary DNA (for example, Au NPs).

Superconducting thin films of niobium have been extensively employed in transmon qubit architectures. Although these architectures have demonstrated improvements in recent years, further improvements in performance through materials engineering will aid in large-scale deployment. Here, we use information retrieved from secondary ion mass spectrometry and electron microscopy to conduct a detailed assessment of the surface oxide that forms in ambient conditions for transmon test qubit devices patterned from a niobium film. We observe that this oxide exhibits a varying stoichiometry with NbO and NbO2found closer to the niobium film/oxide interface and Nb2O5found closer to the surface. In terms of structural analysis, we find that the Nb2O5region is semicrystalline in nature and exhibits randomly oriented grains on the order of 1–3 nm corresponding to monoclinic N–Nb2O5that are dispersed throughout an amorphous matrix. Using fluctuation electron microscopy, we are able to map the relative crystallinity in the Nb2O5region with nanometer spatial resolution. Through this correlative method, we observe that the highly disordered regions are more likely to contain oxygen vacancies and exhibit weaker bonds between the niobium and oxygen atoms. Based on these findings, we expect that oxygen vacancies likely serve as a decoherence mechanism in quantum systems.

The metal thiophosphates (MTP), M2P2S6, are a versatile class of van der Waals materials, which are notable for the possibility of tuning their magnetic properties with the incorporation of different transition-metal cations. Further, they also offer opportunities to probe the independent and synergistic role of the magnetically active cation sublattice when coupled to P2Q6polyhedra. Herein, we report the structural, magnetic, and electronic properties of the series of MTPs, MnxCo2–xP2S6(x= 0.25, 0.5, 1, 1.5, 1.75) synthesized by the P2S5flux method. Structural and elemental analysis indicates a homogeneous stoichiometry in the MnxCo2–xP2S6compounds. We observe that a correlation is apparent between the intensities of specific Raman modes and Raman shifts with respect to the alloying ratio between Mn and Co. Magnetic susceptibility measurements indicate that the alloyed systems adopt an ordered antiferromagnetic (AFM) configuration with a dependence of the Néel temperature on the alloying ratio. A possible magnetic frustration behavior was observed for the composition MnCoP2S6due to magnetic moment compensation as the alloying ratio between Mn and Co approaches parity. Interestingly, mixed oxidation states of the metal cation species are also observed in MnxCo2–xP2S6along with a linear dependence of the work function on the alloying ratio of Mn and Co.

Electron microscopy of soft and biological materials, or “soft electron microscopy”, is essential to the characterization of macromolecules. Soft microscopy is governed by enhancing contrast while maintaining low electron doses, and sample preparation and imaging methodologies are driven by the length scale of features of interest. While cryo-electron microscopy offers the highest resolution, larger structures can be characterized efficiently and with high contrast using low-voltage electron microscopy by performing scanning transmission electron microscopy in a scanning electron microscope (STEM-in-SEM). Here, STEM-in-SEM is demonstrated for a four-lobed protein assembly where the arrangement of the proteins in the construct must be examined. STEM image simulations show the theoretical contrast enhancement at SEM-level voltages for unstained structures, and experimental images with multiple STEM modes exhibit the resolution possible for negative-stained proteins. This technique can be extended to complex protein assemblies, larger structures such as cell sections, and hybrid materials, making STEM-in-SEM a valuable high-throughput imaging method.

Heteroanionic materials exhibit great structural diversity with adjustable electronic, magnetic, and optical properties that provide immense opportunities for materials design. Within this material family, perovskite oxynitrides incorporate earth-abundant nitrogen with differing size, electronegativity, and charge into oxide, enabling a unique approach to tuning metal-anion covalency and energy of metal cation electronic states, thereby achieving functionality that may be inaccessible from their perovskite oxide counterparts, which have been widely studied as electrocatalysts. However, it is very challenging to directly obtain such materials due to the poor thermal stability of late transition metals coordinated with N and/or at high valence states. Herein, we introduce an effective strategy to prepare a perovskite oxynitride with a small fraction of sites substituted with Ir and adopt it as the first electrocatalyst in this material family, thereby enabling high activity and efficient utilization of precious metal content. From a series of characterization techniques, including X-ray absorption spectroscopy, atomic resolution electron microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction, we prove the successful incorporation of Ir into a strontium tungsten oxynitride perovskite structure and discover the formation of a unique Ir–N/O coordination structure. Benefitting from this, the material exhibits a high activity toward the hydrogen evolution reaction, which exhibits an ultralow overpotential of only 8 mV to reach 10 mA/cm2geoin 0.5 M H2SO4and 4.5-fold enhanced mass activity compared to commercial Pt/C. This work opens a new avenue for oxynitride material synthesis as well as pursuit of a new class of high-performance electrocatalysts.

New platforms for the rapid and sensitive detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants of concern are urgently needed. Here we report the development of a nanomechanical sensor based on the deflection of a microcantilever capable of detecting the SARS-CoV-2 spike (S) glycoprotein antigen using computationally designed multivalent minibinders immobilized on a microcantilever surface. The sensor exhibits rapid (<5 min) detection of the target antigens down to concentrations of 0.05 ng/mL (362 fM) and is more than an order of magnitude more sensitive than an antibody-based cantilever sensor. Validation of the sensor with clinical samples from 33 patients, including 9 patients infected with the Omicron (BA.1) variant observed detection of antigen from nasopharyngeal swabs with cycle threshold (Ct) values as high as 39, suggesting a limit of detection similar to that of the quantitative reverse transcription polymerase chain reaction (RT-qPCR). Our findings demonstrate the use of minibinders and nanomechanical sensors for the rapid and sensitive detection of SARS-CoV-2 and potentially other disease markers.

Inspired by the scanning probe block copolymer lithography process, hollow silica shells were loaded with polymer─metal ink mixtures and investigated as solution-based nanoreactors for the synthesis of gold nanoparticles. The incorporation of poly(ethylene oxide) (PEO) into these hollow silica nanoreactors (approximately 40 nm in size) and the use of a two-step reductive annealing process (first at 200 °C and then at 600 °C) results in a high yield (76%) of larger (∼6 nm) single nanoparticles; when the polymer is not used, smaller (∼3 nm) particles dominate, and the yield of single particles is only 6%. It was determined that particle coarsening mostly occurs in the temperature range where the polymer is present and not degraded (i.e., <400 °C for PEO), as indicted by correlative in situ scanning/transmission electron microscopy in a reductive gas-phase environment. Thus, polymer incorporation in this nanoreactor system, which is amenable to scale up, drives the complete conversion of nanoreactor contents without excessive metal loss, highlighting the impact of nanoreactor composition and structural design on particle synthesis.

The understanding of thermoelectric properties of ternary I–III–VI2type (I = Cu, Ag; III = Ga, In; and VI = Te) chalcopyrites is less well developed. Although their thermal transport properties are relatively well studied, the relationship between the electronic band structure and charge transport properties of chalcopyrites has been rarely discussed. In this study, we reveal the unusual electronic band structure and the dynamic doping effect that could underpin the promising thermoelectric properties of Cu1–xAgxGaTe2compounds. Density functional theory (DFT) calculations and electronic transport measurements suggest that the Cu1–xAgxGaTe2compounds possess an unusual non-parabolic band structure, which is important for obtaining a high Seebeck coefficient. Moreover, a mid-gap impurity level was also observed in Cu1–xAgxGaTe2, which leads to a strong temperature-dependent carrier concentration and is able to regulate the carrier density at the optimized value for a wide temperature region and thus is beneficial to obtaining the high power factor and high average ZTof Cu1–xAgxGaTe2compounds. We also demonstrate a great improvement in the thermoelectric performance of Cu1–xAgxGaTe2by introducing Cu vacancies and ZnTe alloying. The Cu vacancies are effective in increasing the hole density and the electrical conductivity, while ZnTe alloying reduces the thermal conductivity. As a result, a maximum ZTof 1.43 at 850 K and a record-high average ZTof 0.81 for the Cu0.68Ag0.3GaTe2–0.5%ZnTe compound are achieved.

Direct top-down nanopatterning of semiconductors is a powerful tool for engineering properties of optoelectronic devices. Translating this approach to two-dimensional semiconductors such as monolayer transition metal dichalcogenides (TMDs) is challenging because of both the small scales required for confinement and the degradation of electronic and optical properties caused by high-energy and high-dose electron radiation used for high-resolution top-down direct electron beam patterning. We show that encapsulating a TMD monolayer with hexagonal boron nitride preserves the narrow exciton linewidths and emission intensity typical in such heterostructures after electron beam lithography, allowing direct patterning of functional optical monolayer nanostructures on scales of a few tens of nanometers. We leverage this fabrication method to study size-dependent effects on nanodot arrays of MoS2and MoSe2as well as laterally confined electrical transport devices, demonstrating the potential of top-down lithography for nanoscale TMD optoelectronics.

Converting waste heat into useful electricity using solid-state thermoelectrics has a potential for enormous global energy savings. Lead chalcogenides are among the most prominent thermoelectric materials, whose performance decreases with an increase in chalcogen amounts (e.g., PbTe > PbSe > PbS). Herein, we demonstrate the simultaneous optimization of the electrical and thermal transport properties of PbS-based compounds by alloying with GeS. The addition of GeS triggers a complex cascade of beneficial events as follows: Ge2+substitution in Pb2+and discordant off-center behavior; formation of Pb5Ge5S12as stable second-phase inclusions through valence disproportionation of Ge2+to Ge0and Ge4+. PbS and Pb5Ge5S12exhibit good conduction band energy alignment that preserves the high electron mobility; the formation of Pb5Ge5S12increases the electron carrier concentration by introducing S vacancies. Sb doping as the electron donor produces a large power factor and low lattice thermal conductivity (κlat) of ∼0.61 W m–1K–1. The highest performance was obtained for the 14% GeS-alloyed samples, which exhibited an increased room-temperature electron mobility of ∼121 cm2V–1s–1for 3 × 1019cm–3carrier density and a ZT of 1.32 at 923 K. This is ∼55% greater than the corresponding Sb-doped PbS sample and is one of the highest reported for the n-type PbS system. Moreover, the average ZT (ZTavg) of ∼0.76 from 400 to 923 K is the highest for PbS-based systems.

In this contribution, the structural and electronic effects of fluoride doping in both crystalline and amorphous indium oxides are investigated by both experimental and theoretical techniques. Pristine crystalline and amorphous fluoride-doped indium oxide (F:In–O) phases were prepared by solution-based combustion synthesis and sol–gel techniques, respectively. The chemical composition, environment, and solid-state microstructure of these materials were extensively studied with a wide array of state-of-the-art techniques such as UV–vis, X-ray photoelectron spectroscopy, grazing incidence X-ray diffraction, 19F and 115In solid-state NMR, high-resolution transmission electron microscopy (HR-TEM), and extended X-ray absorption fine structure (EXAFS) as well as by density functional theory (DFT) computation combined with MD simulations. Interestingly, the UV–vis data reveal that while the band gap increases upon F–-doping in the crystalline phase, it decreases in the amorphous phase. The 19F solid-state NMR data indicate that upon fluorination, the InO3F3environment predominates in the crystalline oxide phase, whereas the InO4F2environment is predominant in the amorphous oxide phase. The HR-TEM data indicate that fluoride doping inhibits crystallization in both crystalline and amorphous In–O phases, a result supported by the 115In solid-state NMR, EXAFS, and DFT-MD simulation data. Thus, this study establishes fluoride as a versatile anionic agent to induce disorder in both crystalline and amorphous indium oxide matrices, while modifying the electronic properties of both, but in dissimilar ways.

Bi2Si2Te6, a 2D compound, is a direct band gap semiconductor with an optical band gap of ∼0.25 eV, and is a promising thermoelectric material. Single-phase Bi2Si2Te6is prepared by a scalable ball-milling and annealing process, and the highly densified polycrystalline samples are prepared by spark plasma sintering. Bi2Si2Te6shows a p-type semiconductor transport behavior and exhibits an intrinsically low lattice thermal conductivity of ∼0.48 W m–1K–1(cross-plane) at 573 K. The first-principles density functional theory calculations indicate that such low lattice thermal conductivity is derived from the interactions between acoustic phonons and low-lying optical phonons, local vibrations of Bi, the low Debye temperature, and strong anharmonicity result from the unique 2D crystal structure and metavalent bonding of Bi2Si2Te6. The Bi2Si2Te6exhibits an optimal figure of merit ZT of ∼0.51 at 623 K, which can be further enhanced by the substitution of Bi with Pb. Pb doping leads to a large increase in power factor S2σ, from ∼3.9 μW cm–1K–2of Bi2Si2Te6to ∼8.0 μW cm–1K–2of Bi1.98Pb0.02Si2Te6at 773 K, owing to the increase in carrier concentration. Moreover, Pb doping induces a further reduction in the lattice thermal conductivity to ∼0.38 W m–1K–1(cross-plane) at 623 K in Bi1.98Pb0.02Si2Te6, due to strengthened point defect (PbBi′) scattering. The simultaneous optimization of the power factor and lattice thermal conductivity achieves a peak ZT of ∼0.90 at 723 K and a high average ZT of ∼0.66 at 400–773 K in Bi1.98Pb0.02Si2Te6.

Colloidal crystal engineering of complex, low-symmetry architectures is challenging when isotropic building blocks are assembled. Here we describe an approach to generating such structures based upon programmable atom equivalents (nanoparticles functionalized with many DNA strands) and mobile electron equivalents (small particles functionalized with a low number of DNA strands complementary to the programmable atom equivalents). Under appropriate conditions, the spatial distribution of the electron equivalents breaks the symmetry of isotropic programmable atom equivalents, akin to the anisotropic distribution of valence electrons or coordination sites around a metal atom, leading to a set of well-defined coordination geometries and access to three new low-symmetry crystalline phases. All three phases represent the first examples of colloidal crystals, with two of them having elemental analogues (body-centred tetragonal and high-pressure gallium), while the third (triple double-gyroid structure) has no known natural equivalent. This approach enables the creation of complex, low-symmetry colloidal crystals that might find use in various technologies.

Metal chalcophosphates, M2P2Q6(M = transition metals; Q = chalcogen), are notable among the van der Waals materials family for their potential magnetic ordering that can be tuned with an appropriate choice of the metal or chalcogen. However, there has not been a systematic investigation of the basic structural evolution in these systems with alloying of the crystal subunits due to the challenge in the diffusion process of mixing different metal cations in the octahedral sites of M2P2Q6materials. In this work, the P2S5flux method was used to enable the synthesis of a multilayered mixed metal thiophosphate Fe2–xCoxP2S6(x= 0, 0.25, 1, 1.75, and 2) system. Here, we studied the structural, vibrational, and electronic fingerprints of this mixed M2P2Q6system. Structural and elemental analyses indicate a homogeneous stoichiometry averaged through the sample over multiple layers of Fe2–xCoxP2S6compounds. It was observed that there is a correlation between the intensity of specific phonon modes and the alloying concentration. The increasing Co alloying concentration shows direct relations to the in-plane [P2S6]4–and out-of-plane P–P dimer vibrations. Interestingly, an unusual nonlinear electronic structure dependence on the metal alloying ratio is found and confirmed by two distinct work functions within the Fe2–xCoxP2S6system. We believe this work provides a fundamental structural framework for mixed metal thiophosphate systems, which may assist in future studies on electronic and magnetic applications of this emerging class of binary cation materials.

Merging the properties of VO2and van der Waals (vdW) materials has given rise to novel tunable photonic devices. Despite recent studies on the effect of the phase change of VO2on tuning near-field optical response of phonon polaritons in the infrared range, active tuning of optical phonons (OPhs) using far-field techniques has been scarce. Here, we investigate the tunability of OPhs of α-MoO3in a multilayer structure with VO2. Our experiments show the frequency and intensity tuning of 2 cm–1and 11% for OPhs in the [100] direction and 2 cm–1and 28% for OPhs in the [010] crystal direction of α-MoO3. Using the effective medium theory and dielectric models of each layer, we verify these findings with simulations. We then use loss tangent analysis and remove the effect of the substrate to understand the origin of these spectral characteristics. We expect that these findings will assist in intelligently designing tunable photonic devices for infrared applications, such as tunable camouflage and radiative cooling devices.

Copper (Cu) is a catalyst broadly used in industry for hydrogenation of carbon dioxide, which has broad implications for environmental sustainability. An accurate understanding of the degeneration behavior of Cu catalysts under operandoconditions is critical for uncovering the failure mechanism of catalysts and designing novel ones with optimized performance. Despite the widespread use of these materials, their failure mechanisms are not well understood because conventional characterization techniques lack the necessary time and spatial resolution to capture these complex behaviors. In order to overcome these challenges, we carried out transmission electron microscopy (TEM) with a specialized in situgas environmental holder, which allows us to unravel the dynamic behavior of the Cu nanowires (NWs) in operando. The failure process of these nanoscale Cu catalysts under CO2atmosphere were tracked and further rationalized based on our numerical modeling using phase-field methods.

Two-dimensional (2D) hybrid lead iodide perovskites have gained prominence due to their remarkable structural tunability, optoelectronic features, and moisture stability, which have rendered them as attractive alternatives to 3D MAPbI3for optoelectronic devices. 2D multilayer lead bromide perovskites remain an unfathomed phase space with the lack of systematic studies to establish the structure, photophysical properties and stability behavior of this family of 2D halide perovskites. Herein, we present new members of bilayer lead bromide perovskites (CmH2m+1NH3)2(CH3NH3)Pb2Br7(m= 6–8) that belong to the Ruddlesden–Popper structure type, incorporating long chain alkyl-monoammonium cations (CmH2m+1NH3) of hexylammonium (m= 6), heptylammonium (m= 7), and octylammonium (m= 8). A universal solution synthetic methodology for bulk multilayer lead bromide perovskites is presented with all structures solved and refined using single crystal X-ray diffraction. The studied bilayer lead bromide perovskites demonstrate a decrease in the lattice rigidity and lattice match of the inorganic perovskite layer–organic layer, as the alkyl-monoammonium chain length increases. In comparison to their iodide analogues, the bilayer lead bromide compounds exhibit elongation of their stacking axis despite the smaller dimensions of the [PbBr6]4−lattice, while their internal lattice strain was calculated to be reduced, inferring a greater lattice match between the inorganic [PbBr6]4−perovskite layer and organic layer. The (CmH2m+1NH3)2(CH3NH3)Pb2Br7(m= 4, 6–8) compounds exhibit narrow-band emission near 2.5 eV. Time-resolved photoluminescence (PL) displays longer carrier lifetimes on the nanosecond time scale comparing to their iodide analogues, where electronic structure calculations indicate that the increase of the alkyl chain length and, thus, lattice softness enhances nonradiative recombinations. A complete set of air, light, and heat stability tests on unencapsulated thin films of (CmH2m+1NH3)2(CH3NH3)Pb2Br7(m= 4, 6–8) and MAPbBr3show they are stable in ambient air for at least 5 months, exhibiting greater extrinsic stability than the 2D lead iodide congeners. Extraordinarily, 3D MAPbBr3films prove to be more stable than films of 2D lead bromide perovskites, in contrast to MAPbI3which is less stable than the 2D lead iodide perovskites.

This paper describes the synthesis, characterization, and modeling of a series of molecules having four protein domains attached to a central core. The molecules were assembled with the “megamolecule” strategy, wherein enzymes react with their covalent inhibitors that are substituted on a linker. Three linkers were synthesized, where each had four oligo(ethylene glycol)-based arms terminated in a para-nitrophenyl phosphonate group that is a covalent inhibitor for cutinase. This enzyme is a serine hydrolase and reacts efficiently with the phosphonate to give a new ester linkage at the Ser-120 residue in the active site of the enzyme. Negative-stain transmission electron microscopy (TEM) images confirmed the architecture of the four-armed megamolecules. These cutinase tetramers were also characterized by X-ray crystallography, which confirmed the active-site serine-phosphonate linkage by electron-density maps. Molecular dynamics simulations of the tetracutinase megamolecules using three different force field setups were performed and compared with the TEM observations. Using the Amberff99SB-disp + pH7 force field, the two-dimensional projection distances of the megamolecules were found to agree with the measured dimensions from TEM. The study described here, which combines high-resolution characterization with molecular dynamics simulations, will lead to a comprehensive understanding of the molecular structures and dynamics for this new class of molecules.

Owing to the diversity of composition and excellent transport properties, the ternary I–III–VI2type diamond-like chalcopyrite compounds are attractive functional semiconductors, including as thermoelectric materials. In this family, CuInTe2and CuGaTe2are well investigated and achieve maximum ZTvalues of ∼1.4 at 950 K and an average ZTof 0.43. However, both compounds have poor electrical conductivity at low temperature, resulting in low ZTbelow 450 K. In this work, we have greatly improved the thermoelectric performance in the quinary diamondoid compound (Cu0.8Ag0.2)(In0.2Ga0.8)Te2by understanding and controlling the effects of different constituent elements on the thermoelectric transport properties. Our combined theoretical and experimental effort indicates that Ga in the In site of the lattice decreases the carrier effective mass and improves the electrical conductivity and power factor of Cu0.8Ag0.2In1–xGaxTe2. Furthermore, Ag in the Cu site strongly suppresses the heat transport via the enhanced acoustic phonon–optical phonon coupling effects, leading to the ultralow thermal conductivity of ∼0.49 W m–1K–1at 850 K in Cu0.8Ag0.2In0.2Ga0.8Te2. Defect formation energy calculations suggest intrinsic Cu vacancies introduce defect levels that are important to the temperature-dependent hole density and electrical conductivity. Therefore, we introduced extra Cu vacancies to optimize the hole carrier density and improve the power factor of Cu0.8Ag0.2In0.2Ga0.8Te2. As a result, a maximum ZTof ∼1.5 at 850 K and an average ZTof 0.78 in the temperature range of 400–850 K are obtained, which is among the highest in the diamond-like compound family.

GeSe, an analogue of SnSe, shows promise in exhibiting exceptional thermoelectric performance in the Pnmaphase. The constraints on its dopability, however, pose challenges in attaining optimal carrier concentrations and improving ZTvalues. This study demonstrates a crystal structure evolution strategy for achieving highly doped samples and promising ZTs in GeSe via LiBiTe2alloying. A rhombohedral phase (R3m) can be stabilized in the GeSe-LiBiTe2system, further evolving into a cubic (Fm3̅m) phase with a rising temperature. The band structures of GeSe-LiBiTe2in the rhombohedral and cubic phases feature a similar multiple-valley energy-converged valence band of L and Σ bands. The observed high carrier concentration (∼1020cm–3) reflects the effective convergence of these bands, enabling a high density-of-states effective mass and an enhanced power factor. Moreover, a very low lattice thermal conductivity of 0.6–0.5 W m–1K–1from 300 to 723 K is achieved in 0.9GeSe-0.1LiBiTe2, approaching the amorphous limit value. This remarkably low lattice thermal conductivity is related to phonon scattering from point defects, planar vacancies, and ferroelectric instability-induced low-energy Einstein oscillators. Finally, a maximum ZTvalue of 1.1 to 1.3 at 723 K is obtained, with a high average ZTvalue of over 0.8 (400–723 K) in 0.9GeSe-0.1LiBiTe2samples. This study establishes a viable route for tailoring crystal structures to significantly improve the performance of GeSe-related compounds.

Direct in situcharacterizations of the solid–fluid interface on the nanoscale can provide profound implications for addressing bulk-scale enigmas. The advent of closed-cell environmental transmission electron microscopy (E-TEM) enables the implementation of a confined nanoscopic reactor within the high-vacuum microscope. With the encapsulations of reactant fluids and solid species under various stimuli, the whole reaction process can be observed with atomic precision and high temporal resolution. This experimental technique has been adopted widely throughout the field of nanoscience, with applications extending to the synthesis of low-dimensional materials, gas-phase catalysis, and modifications of nanomaterials, where Professor C. N. R. Rao has made substantial contributions over six decades. Here, we delve into the recent representative applications and enhancement strategies of the close gas-cell E-TEM methodology from the early development stages to the latest up-to-date ultrathin (UT) SiNxtechnique. Remarkable advancements in the capabilities of multimodal data acquisition, including the quantitative electron diffraction, on-site spatiotemporal mapping of the gas molecules, and atomic-resolution real-space imaging in the gas cell E-TEM, are demonstrated. Furthermore, the integration of machine learning (ML)-assisted data acquisition and analysis is anticipated to represent the next major breakthrough, significantly expanding the applicability of gas-cell E-TEM across a wide range of research fields.

Two-dimensional Ruddlesden–Popper (2D RP) halide perovskites, C2MAn–1PbnI3n+1(C = bulky ammonium cation; MA = methylammonium) with low n-members (n< 5), have been garnering sensational attention for photovoltaic and optoelectronic applications because of the long carrier diffusion lengths, long-term stability, and tunable bandgap. Yet, the surface modification of 2D RP under kinetic particle irradiation, such as light or electron irradiation, is ambiguous, even though it is imperative to elucidate long-stabilized conversion efficiency. Herein, we present molecular-scale observations of dynamic surface reconstruction of BA2MA2Pb3I10(n= 3) 2D RP induced by the electron beam. The surface dynamics reveal lateral growth of polytypic PbI2with 3R, 4H, and 2H structures at the edge and surface of the 2D perovskite, accompanied by simultaneous annihilation at the other edges. Local radiolysis occurs dominantly by the internal energy increase of electron momentum transfer, which triggers a sequential layer-by-layer degradation into PbI2. In situ observation of the polytypic PbI2growth at the whole surface and edges of 2D RP under electron irradiation elucidates how the outer PbI2self-passivation can protect inner 2D RP, causing longer operando stability.

Despite global efforts to reduce carbon dioxide (CO2) emissions, continued industrialization threatens to exacerbate climate change. This work investigates methods to capture CO2, with a focus on the SIFSIX-3-Ni metal–organic framework (MOF) as a direct air capture (DAC) sorbent. SIFSIX-3-Ni exhibits promising CO2adsorption properties but suffers from degradation processes under accelerated aging, which are akin to column regeneration conditions. Herein, we have grown the largest SIFSIX-3-Ni single crystals to date, facilitating single crystal X-ray diffraction analyses that enabled direct observation of the H2O and CO2dynamics through adsorption and desorption. In addition, a novel space group (I4/mcm) for the SIFSIX-3-Ni is identified, which provided insights into structural transitions within the framework and elucidated water’s role in degrading CO2uptake performance as the material ages. In situX-ray scattering methods revealed long-range and local structural transformations associated with CO2adsorption in the framework pores as well as a temperature-dependent desorption mechanism. Pair distribution function analysis revealed a partial decomposition to form nonporous single-layer nanosheets of edge-sharing nickel oxide octahedra upon aging. The formation of these nanosheets is irreversible and reduces the amount of active material for the CO2sorption. These findings provide crucial insights for the development of efficient and stable DAC sorbents, effectively reducing greenhouse gases, and suggest avenues for enhancing MOF stability under practical DAC conditions.

Molybdenum nitrides and oxynitrides are of interest as catalysts for a wide variety of applications. They are commonly synthesized via the high-temperature ammonolysis of MoO3in which the oxide precursor is reacted with gas-phase ammonia at an elevated temperature. Despite the widespread adoption of ammonolysis as a synthetic approach, the reaction pathway leading to the formation of molybdenum nitrides by this method remains poorly understood. In this work, combined in situ powder X-ray diffraction (PXRD) and in situ transmission electron microscopy (TEM) are used to fully map the transformation of MoO3to the final product and identify the structure relationships among the precursors, intermediates, and product. Two key intermediates, MoO2and HxMoO3-I (x≈ 0.3), are identified, with hexagonal δ-MoN occurring as a minor, short-lived, high-temperature intermediate, depending on reaction conditions. Notably, the reaction is topotactic throughout the transformation from MoO3to HxMoO3-I to MoO2and finally to cubic γ-MoOxNy. There is no evidence for direct transformation from HxMoO3-I to γ-MoOxNy, a route suggested in the prior literature. Moreover, even when the reaction follows a pathway in which the material fully transforms to MoO2at intermediate temperatures, single-phase γ-MoOxNyis obtained after reaction at 800 °C. This comprehensive elucidation of the reaction pathway provides a roadmap for future tuning of the molybdenum oxynitride morphology and chemistry.

Abstract: In this work, we highlight the often-overlooked effects of doping on the microstructure and performance of bulk thermoelectric materials to offer a broader perspective on how dopants interact with their parent material. Using PbSe doped with Na, Ag, and K as a model material system, we combine original computational, experimental, and microscopy data with established trends in material behavior, to provide an in-depth discussion of the relationship between dopants, processing, and microstructure, and their effects on thermoelectric efficiency and thermal stability. Notable observations include differences in the microstructure and mass loss of thermally treated samples of Na- and Ag-doped PbSe, as well as findings that Na and K cations exist predominantly as substitutional point defects while Ag also occupies interstitial sites and exhibits lower solubility. We discuss how these differences in point defect populations are known to affect a dopants’ ability to alter carrier concentration and how they may affect the mechanical properties of PbSe during processing. Graphic Abstract:

Layered heterostructure materials with two different functional building blocks can teach us about emergent physical properties and phenomena arising from interactions between the layers. We report intergrowth compounds KLaM1 – xTe4(M= Mn and Zn; x≈ 0.35) featuring two chemically distinct alternating layers [LaTe3] and [KM1 – xTe]. Their crystal structures are incommensurate, determined by single X-ray diffraction for the Mn compound and a transmission electron microscope study for the Zn compound. KLaMn1 – xTe4crystallizes in the orthorhombic superspace group Pmnm(01/2γ)s00 with lattice parameters a= 4.4815(3) Å, b= 21.6649(16) Å, and c= 4.5220(3) Å. It exhibits charge density wave order at room temperature with a modulation wave vector q= 1/2b* + 0.3478c* originating from electronic instability of Te-square nets in [LaTe3] layers. The Mn analog exhibits a cluster spin glass behavior with spin freezing temperature Tf≈ 5 K attributed to disordered Mn vacancies and competing magnetic interactions in the [Mn1 – xTe] layers. The Zn analog also has charge density wave order at room temperature with a similar q-vector having the c* component ∼0.346 confirmed by selected-area electron diffraction. Electron transfer from [KM1 – xTe] to [LaTe3] layers exists in KLaM1 – xTe4, leading to an enhanced electronic specific heat coefficient. The resistivities of KLaM1 – xTe4(M= Mn and Zn) exhibit metallic behavior at high temperatures and an upturn at low temperatures, suggesting partial localization of carriers in the [LaTe3] layers with some degree of disorder associated with the Matom vacancies in the [M1 – xTe] layers.

We report a reactive flux technique using the common reagent P2S5and metal precursors developed to circumvent the synthetic bottleneck for producing high-quality single- and mixed-metal two-dimensional (2D) thiophosphate materials. For the monometallic compound, M2P2S6(M = Ni, Fe, and Mn), phase-pure materials were quickly synthesized and annealed at 650 °C for 1 h. Crystals of dimensions of several millimeters were grown for some of the metal thiophosphates using optimized heating profiles. The homogeneity of the bimetallic thiophosphates MM′P2S6(M, M′ = Ni, Fe, and Mn) was elucidated using energy-dispersive X-ray spectroscopy and Rietveld refinement. The quality of the selected materials was characterized by transmission electron microscopy and atomic force microscopy measurements. We report two novel bimetallic thiophosphates, MnCoP2S6and FeCoP2S6. The Ni2P2S6and MnNiP2S6flux reactions were monitored in situ using variable-temperature powder X-ray diffraction to understand the formation reaction pathways. The phases were directly formed in a single step at approximately 375 °C. The work functions of the semiconducting materials were determined and ranged from 5.28 to 5.72 eV.

Many strategies have been employed to maintain an “optimal carrier concentration” to achieve a high thermoelectric power factor in n-type PbTe. Here, we show that a high power factor can also be achieved over a broad temperature range without attaining the optimal carrier concentration by alloying n-type PbTe with GaSb. We find that GaSb dissociates into Ga and Sb and dissolves into the PbTe matrix. Ga atoms introduce impurity levels above the valence band of PbTe giving rise to diminished electron–phonon coupling and an increased carrier effective mass leading to a high Seebeck coefficient of −87 μV K–1and a high carrier mobility of 810 cm2V–1s–1at 300 K. As a result, a high power factor of 29 μW cm–1K–2at 323 K is achieved. Phonon band-structure calculations show that Ga is off-centered (0.05 Å) from Pb site along the ⟨111⟩ direction leading to a reduced lattice thermal conductivity of 0.7 W m–1K–1and a maximum thermoelectric figure of merit of 1.35 at 773 K in PbTe0.997I0.003–2 mol % GaSb. The dissolution of III–V semiconductors in lead telluride is a new finding with broader implications and opens new avenues in controlling thermal and charge transport in advanced thermoelectric materials.

Understanding the behavior of high-entropy alloy (HEA) materials under hydrogen (H2) environment is of utmost importance for their promising applications in structural materials, catalysis, and energy-related reactions. Herein, the reduction behavior of oxidized FeCoNiCuPt HEA nanoparticles (NPs) in atmospheric pressure H2environment was investigated by in situgas-cell transmission electron microscopy (TEM). The reduction reaction front was maintained at the external surface of the oxide. During reduction, the oxide layer expanded and transformed into porous structures where oxidized Cu was fully reduced to Cu NPs while Fe, Co, and Ni remained in the oxidized form. In situchemical analysis showed that the expansion of the oxide layer resulted from the outward diffusion flux of all transition metals (Fe, Co, Ni, Cu). Revealing the H2reduction behavior of HEA NPs facilitates the development of advanced multicomponent alloys for applications targeting H2formation and storage, catalytic hydrogenation, and corrosion removal.

To improve their synthesis and ultimately realize the technical promise of two-dimensional covalent organic frameworks (2D COFs), it is imperative that a robust understanding of their structure be developed. However, high-resolution transmission electron microscopy (HR-TEM) imaging of such beam-sensitive materials is an outstanding characterization challenge. Here, we overcome this challenge by leveraging low electron flux imaging conditions and high-speed direct electron counting detectors to acquire high-resolution images of 2D COF films. We developed a Fourier mapping technique to rapidly extract nanoscale structural information from these TEM images. This postprocessing script analyzes the evolution of 2D Fourier transforms across a TEM image, which yields information about polycrystalline domain orientations and enables quantification of average domain sizes. Moreover, this approach provides information about several types of defects present in a film, such as overlapping grains and various types of grain boundaries. We also find that the pre-eminent origin of defects in COF-5 films, a prototypical boronate ester-linked COF, arises as a consequence of broken B–O bonds formed during polymerization. These results suggest that the nanoscale features observed are a direct consequence of chemical phenomena. Taken together, this mapping approach provides information about the fundamental microstructure and crystallographic underpinnings of 2D COF films, which will guide the development of future 2D polymerization strategies and help realize the goal of using 2D COFs in a host of thin-film device architectures.

This paper presents a method to synthetically tune atomically precise megamolecule nanobody–enzyme conjugates for prodrug cancer therapy. Previous efforts to create heterobifunctional protein conjugates suffered from heterogeneity in domain stoichiometry, which in part led to the failure of antibody–enzyme conjugates in clinical trials. We used the megamolecule approach to synthesize anti-HER2 nanobody–cytosine deaminase conjugates with tunable numbers of nanobody and enzyme domains in a single, covalent molecule. Linking two nanobody domains to one enzyme domain improved avidity to a human cancer cell line by 4-fold but did not increase cytotoxicity significantly due to lowered enzyme activity. In contrast, a megamolecule composed of one nanobody and two enzyme domains resulted in an 8-fold improvement in the catalytic efficiency and increased the cytotoxic effect by over 5-fold in spheroid culture, indicating that the multimeric structure allowed for an increase in local drug activation. Our work demonstrates that the megamolecule strategy can be used to study structure–function relationships of protein conjugate therapeutics with synthetic control of protein domain stoichiometry.

Metal heteroanionic compounds such as oxynitrides, oxysulfides, and oxyhalides have emerged as promising photocatalysts for water splitting, owing to their reduced band gaps compared to conventional oxides. Nonetheless, many of these compounds undergo self-oxidation of the non-oxide anions by photogenerated holes. Herein, we present new metal oxychloride intergrowths based on Bi4TaO8Cl–Bi2GdO4Cl as stable visible light photocatalysts. These intergrowths were prepared using a halide flux method, with their crystal structures analyzed by Rietveld refinement of powder X-ray diffraction data and high-resolution scanning transmission electron microscopy. These analyses support intergrowth formation. The Ta/Gd molar ratio was systematically varied in the intergrowths to rationalize the effect of charge separation and changes in band structure toward photocatalytic water-splitting activity. Furthermore, these intergrowths are capable of sustained overall water splitting in a Z-scheme with Ru/SrTiO3/Rh as a hydrogen evolution catalyst. The high stability of these intergrowth materials is attributed to O 2p orbitals at the valance band edge rather than Cl 3p orbitals, as discerned from electronic structure calculations. These results provide new strategies for designing durable artificial photosynthetic systems by rational modulation of crystal and electronic structure.

Thermoelectric materials generate electric energy from waste heat, with conversion efficiency governed by the dimensionless figure of merit, ZT. Single-crystal tin selenide (SnSe) was discovered to exhibit a high ZT of roughly 2.2–2.6 at 913 K, but more practical and deployable polycrystal versions of the same compound suffer from much poorer overall ZT, thereby thwarting prospects for cost-effective lead-free thermoelectrics. The poor polycrystal bulk performance is attributed to traces of tin oxides covering the surface of SnSe powders, which increases thermal conductivity, reduces electrical conductivity and thereby reduces ZT. Here, we report that hole-doped SnSe polycrystalline samples with reagents carefully purified and tin oxides removed exhibit an ZT of roughly 3.1 at 783 K. Its lattice thermal conductivity is ultralow at roughly 0.07 W m–1K–1at 783 K, lower than the single crystals. The path to ultrahigh thermoelectric performance in polycrystalline samples is the proper removal of the deleterious thermally conductive oxides from the surface of SnSe grains. These results could open an era of high-performance practical thermoelectrics from this high-performance material.

Magnetic nanostructures (MNS) have a wide range of biological applications due to their biocompatibility, superparamagnetic properties, and customizable composition that includes iron oxide (Fe3O4), Zn2+, and Mn2+. However, several challenges to the biomedical usage of MNS must still be addressed, such as formulation stability, inability to encapsulate therapeutic payloads, and variable clearance rates in vivo. Here, we enhance the utility of MNS during controlled delivery applications via encapsulation within polymeric bicontinuous nanospheres (BCNs) composed of poly(ethylene glycol)-block-poly(propylene sulfide) (PEG-b-PPS) copolymers. PEG-b-PPS BCNs have demonstrated versatile encapsulation and delivery capabilities for both hydrophilic and hydrophobic payloads due to their unique and highly organized cubic phase nanoarchitecture. MNS-embedded BCNs (MBCNs) were thus coloaded with physicochemically diverse molecular payloads using the technique of flash nanoprecipitation and characterized in terms of their structure and in vivo biodistribution following intravenous administration. Retention of the internal aqueous channels and cubic architecture of MBCNs were verified using cryogenic transmission electron microscopy and small-angle X-ray scattering, respectively. MBCNs demonstrated improvement in magnetic resonance imaging (MRI) contrast enhancement (r2relaxivity) as compared to free MNS, which in combination with scanning transmission electron microscopy and energy-dispersive X-ray spectroscopy evidenced the clustering and continued access to water of MNS following encapsulation. Furthermore, MBCNs were found to be noncytotoxic and able to deliver their hydrophilic and hydrophobic small-molecule payloads both in vitro and in vivo. Finally, the oxidation sensitivity of the hydrophobic PPS block allowed MBCNs to undergo a unique, triggerable transition in morphology into MNS-bearing micellar nanocarriers. In summary, MBCNs are an attractive platform for the delivery of molecular and nanoscale payloads for diverse on-demand and sustained drug delivery applications.

Although high-entropy alloys (HEAs) have shown tremendous potential for elevated temperature, anticorrosion, and catalysis applications, little is known on how HEA materials behave under complex service environments. Herein, we studied the high-temperature oxidation behavior of Fe0.28Co0.21Ni0.20Cu0.08Pt0.23HEA nanoparticles (NPs) in an atmospheric pressure dry air environment by in situgas-cell transmission electron microscopy. It is found that the oxidation of HEA NPs is governed by Kirkendall effects with logarithmic oxidation rates rather than parabolic as predicted by Wagner’s theory. Further, the HEA NPs are found to oxidize at a significantly slower rate compared to monometallic NPs. The outward diffusion of transition metals and formation of disordered oxide layer are observed in real time and confirmed through analytical energy dispersive spectroscopy, and electron energy loss spectroscopy characterizations. Localized ordered lattices are identified in the oxide, suggesting the formation of Fe2O3, CoO, NiO, and CuO crystallites in an overall disordered matrix. Hybrid Monte Carlo and molecular dynamics simulations based on first-principles energies and forces support these findings and show that the oxidation drives surface segregation of Fe, Co, Ni, and Cu, while Pt stays in the core region. The present work offers key insights into how HEA NPs behave under high-temperature oxidizing environment and sheds light on future design of highly stable alloys under complex service conditions.

The insertion and removal of Li+ions into Li-ion battery electrodes can lead to severe mechanical fatigue because of the repeated expansion and compression of the host lattice during electrochemical cycling. In particular, the lithium manganese oxide spinel (LiMn2O4, LMO) experiences a significant surface stress contribution to electrode chemomechanics upon delithiation that is asynchronous with the potentials where bulk phase transitions occur. In this work, we probe the stress evolution and resulting mechanical fracture from LMO delithation using an integrated approach consisting of cyclic voltammetry, electron microscopy, and density functional theory (DFT) calculations. High-rate electrochemical cycling is used to exacerbate the mechanical deficiencies of the LMO electrode and demonstrates that mechanical degradation leads to slowing of delithiation and lithiation kinetics. These observations are further supported through the identification of significant fracturing in LMO using scanning electron microscopy. DFT calculations are used to model the mechanical response of LMO surfaces to electrochemical delithiation and suggest that particle fracture is unlikely in the [001] direction because of tensile stresses from delithiation near the (001) surface. Transmission electron microscopy and electron backscatter diffraction of the as-cycled LMO particles further support the computational analyses, indicating that particle fracture instead tends to preferentially occur along the {111} planes. This joint computational and experimental analysis provides molecular-level details of the chemomechanical response of the LMO electrode to electrochemical delithiation and how surface stresses may lead to particle fracture in Li-ion battery electrodes.

Macrophages can associate with extracellular matrix (ECM) demonstrating nanosequenced cell-adhesive RGD ligand. In this study, we devised barcoded materials composed of RGD-coated gold and RGD-absent iron nanopatches to show various frequencies and position of RGD-coated nanopatches with similar areas of iron and RGD-gold nanopatches that maintain macroscale and nanoscale RGD density invariant. Iron patches were used for substrate coupling. Both large (low frequency) and externally positioned RGD-coated nanopatches stimulated robust attachment in macrophages, compared with small (high frequency) and internally positioned RGD-coated nanopatches, respectively, which mediate their regenerative/anti-inflammatory M2 polarization. The nanobarcodes exhibited stability in vivo. We shed light into designing ligand-engineered nanostructures in an external position to facilitate host cell attachment, thereby eliciting regenerative host responses.