White light-emitting diodes are gaining popularity and are set to become the most common light source in the U.S. by 2025. However, their performance is still limited by the lack of an efficient red-emitting component with a narrow band emission. The red phosphor SrLiAl3N4:Eu2+ is among the first promising phosphors with a small bandwidth for next-generation lighting, but the microscopic origin of this narrow emission remains elusive. In the present work, density functional theory, the ΔSCF-constrained occupation method, and a generalized Huang–Rhys theory are used to provide an accurate description of the vibronic processes occurring at the two Sr2+ sites that the Eu2+ activator can occupy. The emission band shape of Eu(Sr1), with a zero-phonon line at 1.906 eV and a high luminescence intensity, is shown to be controlled by the coupling between the 5dz2–4f electronic transition and the low-frequency phonon modes associated with the Sr and Eu displacements along the Sr channel. The good agreement between our computations and experimental results allows us to provide a structural assignment of the observed total spectrum. By computing explicitly the effect of the thermal expansion on zero-phonon line energies, the agreement is extended to the temperature-dependent spectrum. These results provide insight into the electron–phonon coupling that accompanies the 5d–4f transition in similar UCr4C4-type phosphors. Furthermore, these resultshighlight the importance of the Sr channel in shaping the narrow emission of SrLiAl3N4:Eu2+, and they shed new light on the structure–property relations of such phosphors.

We investigated the effect of the aluminum distribution in the adsorption properties of carbon dioxide in the MFI, MOR, and ITW zeolites. Because of its lack of experimental evidence and theoretical validation, Löwenstein’s rule was not generally imposed, and special attention was paid to the effect of the Al–O–Al linkages. To this end, we first generalized an existing transferable force field for CO2 adsorption in non-Löwenstein zeolites. By means of molecular simulations based on this force field, we showed that the carbon dioxide adsorption efficiency in MFI is determined by the number of Al atoms, rather than by their distribution in the framework. This was attributed to the small size of the CO2 molecules compared to the 3D wide-channel topology of the structure. Conversely, we found that the Al distribution has a higher impact on the heat of adsorption in MOR. Although structures with a very high and very low number of non-Löwenstein bonds presented significant differences, the bonds themselves do not affect the heat of adsorption directly. Instead, we found that an homogeneous distribution of the Al atoms in the sites forming the C-channel is more favorable. Finally, the small-pore distribution of the ITW zeolite led to high values of the heat of adsorption and wide error bars, which made the study feasible just for low aluminum concentrations. In that case, we report a small dependency of the heat of adsorption on the Al distribution.

Area-selective deposition (ASD) using a precursor inhibitor (PI) is a promising alternative to self-assembled monolayer inhibitors due to a wide range of material selection and high process compatibility. In this study, bis(ethylcyclopentadienyl)ruthenium [Ru(EtCp)2] is introduced as a homometallic PI for the ASD of Ru. The chemical reactivity and steric hindrance between Ru(EtCp)2, the Ru precursor, and H2O are theoretically calculated using density functional theory calculations and Monte Carlo simulations. The blocking property is related to the packing density of Ru(EtCp)2 on the surface, and unoccupied sites degrade the blocking property. An additional H2O pulse is used to hydrolyze and remove the Et groups of Ru(EtCp)2 to create more space for the additional adsorption of Ru(EtCp)2. As a result, the packing density of Ru(EtCp)2 PI increases, leading to an improvement in the blocking property. A single pulse of Ru(EtCp)2 inhibits the growth of the Ru atomic layer deposition (ALD) film for 200 cycles, whereas Ru(EtCp)2 with an additional H2O pulse inhibits the growth of the Ru ALD film for up to 300 cycles. Transmission electron microscopy results show that the Ru ASD thin films are purely metallic even after the degradation of Ru(EtCp)2. This highlights the possibility of using homometallic PIs in future applications of metal ASD processes.

HgTe nanocrystals are one of the most promising candidates for optoelectronic applications in short- and middle-range infrared wavelength regions. Fabrication of one-dimensional anisotropic HgTe nanoparticles with a wurtzite structure has been a challenging task, so far. We introduce a two-step cation-exchange strategy to synthesize wurtzite-phase HgTe nanorods, starting from CdTe nanorods and proceeding through the formation of a Cu2–xTe intermediate. We demonstrate a means to tune the residual Cu content in the final HgTe nanorods from tens to less than one at % by adjusting the oleylamine and N,N-dimethylethylenediamine concentrations used during the Cu-to-Hg cation-exchange step. The photoluminescence peak position of the HgTe nanorods is tunable in the broad spectral range from 1500 to 2500 nm with the decrease of the residual Cu content. Field-effect transistors based on fabricated HgTe nanorods show favorable transport characteristics, namely, hole mobilities up to 10–2 cm2V–1 s–1 and on/off current ratio up to 103. The responsivity of photodetectors based on HgTe nanorods at 1340 nm reaches 1 A/W, and the detectivity is up to 1010 Jones for the devices with a simple planar geometry. Results presented here indicate wide prospects for exploring the electronic properties of wurtzite HgTe nanorods, as well as cation-doping and ligand surface passivation effects on device performance, which is of great importance for the field of modern optoelectronics.

In the original Editorial, the interview with Olivia Adly Attallah stated, “Within her research group, she is leading a project on chemical recycling of plastic waste entitled ‘Bio Innovation of a Circular Economy for Plastic’ (BioICEP) that is sponsored by the European Union–China Horizon 2020 Cooperation Initiative.” This statement is inaccurate. The statement should have read, “Within her research group, she is leading a project on the chemical recycling of plastic waste as part of a larger European Union–China flagship H2020 project entitled ‘Bio Innovation of a Circular Economy for Plastic’ (BioICEP).” This article has not yet been cited by other publications.

Conjugated polymer organic mixed ionic–electronic conductors (OMIECs) consist of a complex arrangement of crystalline and amorphous regions at the nanoscale. The arrangement of ions in this heterogeneous environment upon electrochemical doping influences the performance of devices that leverage mixed conductivity. This study investigates how varying the ratio of amorphous and crystalline content affects the distribution of ions in blends of regiorandom (RRa) and regioregular (RR) poly(3-hexylthiophene) (P3HT). By correlating changes in the polymer lattice spacing upon ion uptake with spectroelectrochemistry measurements of polaron formation, we find that ions enter the crystalline regions of the polymer first. Using nanoscale infrared imaging with photoinduced force microscopy (PiFM) of the infrared-active PF6– ions, we map the location of ions at the nanoscale and show that ions cluster in crystalline regions of P3HT thin films. We correlate the infrared images of ion locations with visible PiFM (785 nm) to map the presence of polarons in the film and find that the locations of ions and polarons are correlated. This study also reveals that balancing the distribution of amorphous and crystalline regions can enhance ion injection kinetics. These results underline the importance of controlling the nanoscale morphology of conjugated polymers for high-performing OMIECs.

Eutectic electrolytes can attain high concentrations of redox-active species, offering a path toward high energy density redox flow batteries. Here we introduce a new entropically-driven eutectic mixing approach using organic small molecules. By mixing chemically similar redox-active species, we engineer highly concentrated, low viscosity liquids composed almost entirely of redox-active molecules. Using quinones as a model system, we discover a ternary benzoquinone eutectic mixture and a binary naphthoquinone eutectic mixture which have theoretical redox-active electron concentrations of 16.8 and 8.8 M e–, respectively. We investigate compatibility with protic supporting electrolytes and quantify ionic conductivity and viscosity of quinone eutectic electrolytes across multiple states of charge. A binary naphthoquinone eutectic electrolyte with a protic ionic liquid supporting electrolyte (7.1 M e–, theoretical volumetric capacity 188 Ah L–1) achieves a volumetric capacity of 49 Ah L–1 in symmetric static cell cycling. These preliminary results suggest that entropy-driven eutectic mixing is a promising strategy for developing high-energy density flow battery electrolytes.

Photocatalytic conversion of solar energy to generate green hydrogen is considered to be one of the most promising methods in response to the energy problem. Recently, covalent organic frameworks (COFs) have emerged as a potential new class of materials in photocatalytic hydrogen production. Herein, a planar and strong donor–acceptor (D–A) COF was constructed by simply introducing strongly electronegative F atoms. By experiments and theoretical calculations, the key role of F was verified in charge separation and transfer. On the one hand, it can form intramolecular hydrogen bonds, reducing the torsion angle caused by steric hindrance and maintaining AA′ positive stacking mode, which promotes charge transfer in the axial direction. On the other hand, the enhanced electron-withdrawing effect could increase the intrinsic separation driving force of charge separation and enhance π–π interactions, thus prolonging the lifetime of carriers between COF layers and reducing charge recombination. As a result, COF-F performed the highest photocatalysis hydrogen evolution of 10.58 mmol g–1 h–1 (52.9 μmol h–1) than COF-H and COF-Cl. Thus, this work provides novel insight into designing COF photocatalysts with enhanced charge separation and transfer efficiency by molecular structure engineering.

In the tissue engineering field, cell death due to oxygen shortage is still a major challenge for the construction and transplantation of three-dimensional (3D) tissues. To address this problem, oxygen-releasing materials have attracted much attention in recent years. Although calcium peroxide (CaO2) is one of the most common oxygen sources for these types of materials, limitations have also been reported concerning the burst release of oxygen after immersion in water. Herein, we introduce a new strategy to delay the oxygen release from CaO2 microparticles through coating with a hydroxyapatite (HAp) layer (HAp-CaO2) that serves as a diffusion barrier. Strikingly, this coating can be applied by simple immersion of CaO2 microparticles in phosphate buffer (PB) solution. We demonstrate that gelatin hydrogels with embedded HAp-CaO2 microparticles release oxygen for 10 days as compared to only 3 days for identical hydrogels including uncoated CaO2 microparticles. In addition, we demonstrate that the sustained oxygen supply from these hydrogels shows a drastic improvement in cell proliferation under hypoxic conditions. Taken together, this study introduces an easy strategy for sustained oxygen release based on inorganic microparticle formation that can be applied to a broad range of biomaterials for the development of oxygen-releasing materials.

X-ray photoelectron spectroscopy (XPS) is widely used to determine the chemical and electronic states of atoms within a material. However, it is often complex to interpret the O 1s region in metal oxides, where an ∼531 eV binding energy feature appears between lattice oxygen (∼530 eV) and oxygen-containing surface species (∼532 eV). This feature has been vaguely ascribed to oxygen vacancies or oxygen deficient regions for many decades. This work employs full-potential density functional theory to calculate the binding energies of the O 1s electrons under two- and three-dimensional periodic boundary conditions as a probe of expected XPS spectra. ZnO is used as an example system. Both bulk crystal regions containing a range of oxygen defects and slabs with a range of surface terminations and functionalizations have been considered. The slabs considered are mostly {1010} and {1120} surfaces that are not expected to be reconstructed from the cleaved bulk structure. The resulting O 1s binding energies show no signature for oxygen defects in bulk regions. Furthermore, the 531 eV binding energy feature often ascribed to oxygen vacancies or oxygen deficient regions can instead be readily explained by the O 1s electrons from water molecules strongly bound to the exposed ZnO surface (i.e., chemisorbed, as distinct from more loosely bound water) or surface oxygen passivated with hydrogen. This work will rectify many misinterpretations of XPS data of the O 1s region in metal oxides, provide guidance for precisely understanding the oxygen states of a material, and subsequently enable the real origin of material properties to be revealed.

Precisely designing metal nanoparticles (NPs) is the cornerstone for maximizing their efficiency in applications like catalysis or sensor technology. Metal–organic frameworks (MOFs) with their defined and tunable pore systems provide a confined space to host and stabilize small metal NPs. In this work, the MOF encapsulation of various atom-precise clusters following the bottle-around-ship approach is investigated, providing general insights into the scaffolding mechanism. Eleven carbonyl-stabilized Pt(M) (M = Co, Ni, Fe, and Sn) clusters are employed for the encapsulation in the zeolitic imidazolate framework (ZIF)-8. Infrared and UV/Vis spectroscopy, density functional theory, and ab initio molecular dynamics revealed structure–encapsulation relationship guidelines. Thereby, cluster polarization, size, and composition were found to condition the scaffolding behavior. Encaging of [NBnMe3]2[Co8Pt4C2(CO)24] (Co8Pt4) is thus achieved as the first MOF-encapsulated bimetallic carbonyl cluster, Co8Pt4@ZIF-8, and is fully characterized including X-ray absorption near edge and extended X-ray absorption spectroscopy. ZIF-8 confinement not only promotes property changes, like the T-dependent magnetism, but it also further allows heat-induced ligand-stripping without altering the cluster size, enabling the synthesis of naked, heterometallic, close to atom-precise clusters.

Stable molecular clusters are of interest for targeted deposition in porous materials. In this work, we report the discovery of two new molecular Ce–O clusters of composition [Ce6O4(OH)4(NO3)4(DMF)4(C7H4O2X)8]·(DMF)4(H2O)2 (1-X) and [Ce6O4(OH)4(H2O)6(NO3)6(C7H4O2X)6] (2-X) (X = −Cl, −CHO, and −Br). Both cluster types contain a similar hexanuclear building unit, and crystal structures were determined from single-crystal X-ray diffraction or 3D electron diffraction data and subsequent Rietveld refinements against powder X-ray diffraction (PXRD) data. The crystal structure data is complemented by results from the local structure around the cerium ions, determined by extended X-ray absorption fine structure (EXAFS) measurements in the solid state. The composition of all Ce–O clusters was confirmed by elemental analysis, NMR and IR spectroscopy. The Ce–O clusters are highly soluble, up to 101 and 136 g/L for 1-Cl and 2-Cl, respectively, in organic solvents, which strongly depends on the type of cluster and functionalization of the benzoate ligands. Moreover, the structural and compositional integrity of dissolved clusters in different solvents was established. Recrystallization of 1-Cl from dichloromethane (DCM) and Raman spectroscopy confirm the integrity of both cluster types in solution. Further examination by EXAFS measurements on the Ce K-edge of clusters containing 4-chlorobenzoate reveals that only minor changes in the cerium environment of 1-Cl are observed upon dissolution in THF, DCM, and dioxane, while the results for 2-Cl indicate a partial degradation upon dissolution. After proving the stability, a cluster solution of 1-Cl was used to impregnate the mesoporous metal–organic framework Cr-MIL-101. Extensive characterization by PXRD, inductively coupled plasma-optical emission spectroscopy, and energy-dispersive X-ray spectroscopy, as well as thermogravimetry and N2-sorption measurements, confirm the successful insertion of Ce–O clusters into the large mesoporous cages of the framework. Due to the combination of high surface area and potential catalytic activity, the Cluster@MOF materials could be of high interest for application in heterogeneous catalysis.

Harvesting devices based on thermogalvanic principles, such as thermally regenerative electrochemical cycles (TREC), hold great promise for Internet of Things applications where autonomy is critical. One architecture that is particularly interesting for TREC cells with improved energy density, efficiency, and scalability is the thin-film Li-ion battery. In this work, a paradigm to guide the design of thin-film Li-ion-based TREC cells is established via three criteria for electrode selection. These requirements were distilled by translating the TREC principle into measurable material properties for Li-ion electrodes. More specifically, the identified criteria included a high thermogalvanic cell coefficient preferably exceeding 0.2 mV K–1, a weak dependence of the thermogalvanic coefficient on the lithiation state, and a favorable balance between the thermogalvanic cell coefficient and electrode kinetics as estimated from the lithiation overpotential. The material properties necessary to assess these criteria can all be obtained via a previously developed thermogalvanic characterization methodology. In the present work, this methodology was applied to a catalogue of five electrode materials, namely, LiMn2O4 (LMO), Li4Ti5O12 (LTO), LiFePO4 (LFP), anatase TiO2, and Cl-doped amorphous TiO2. The obtained results were organized into three separate blocks, each focused on a specific aspect, like electrolyte decomposition, nanoscaling effects, and kinetics, that warrants special consideration during thermogalvanic characterization. A material selection matrix was subsequently compiled by applying the aforementioned selection criteria to the characterization results. In this manner, LTO was identified as the most suitable candidate electrode, and recommendations for future investigations of thin-film Li-ion TREC devices could be delivered.

Plasmonic metal–semiconductor heterostructures with well-defined morphologies and spatial architectures have emerged as promising materials for wide applications in photocatalysis and optoelectronics. However, the synthesis of such structures with high quality and high yield remains a great challenge due to the incompatibility between the two materials. Herein, we report an optimized approach for the controlled preparation of branched Ag-CdS icosapods, which possess 20 CdS arms with an ordered spatial arrangement on the Ag cores. Moreover, the length, diameter, and thickness of the CdS arms on the Ag nanoparticles can be precisely tuned by the synthetic conditions, leading to Ag-CdS icosapods with tunable absorption properties. Furthermore, more complex hierarchical nanostructures can be achieved by the secondary growth of nanoplate arrays on the CdS arms. As a proof of concept, a phototransistor based on the self-assembled monolayer film of Ag-CdS icosapods shows a stable photoresponse and quite a fast switching performance under optical illumination of 540 nm without excitation of the CdS, which originates from the generation and transfer of plasmon-induced hot carriers in the Ag-CdS icosapods under an applied bias. This work offers a reproducible approach to finely tuning metal–semiconductor heterostructures with desirable architectures and paves the way for more deeply understanding their structure–property correlation.

We report on quasielastic neutron scattering (QENS) and ab initio molecular dynamics (AIMD) simulations of the mechanism of proton diffusion in the partially and fully hydrated barium indate oxide proton conductors Ba2In2O5(H2O)x (x = 0.30 and 0.92). Structurally, these materials are featured by an intergrowth of cubic and “pseudo-cubic” layers of InO6 octahedra, wherein two distinct proton sites, H(1) and H(2), are present. We show that the main localized dynamics of these protons can be described as rotational diffusion of O–H(1) species and H(2) proton transfers between neighboring oxygen atoms. The mean residence times of both processes are in the order of picoseconds in the two studied materials. For the fully hydrated material, Ba2In2O5(H2O)0.92, we also reveal the presence of a third proton site, H(3), which becomes occupied upon increasing the temperature and serves as a saddle state for the interexchange between H(1) and H(2) protons. Crucially, the occupation of the H(3) site enables long-range diffusion of protons, which is highly anisotropic in nature and occurs through a two-dimensional pathway. For the partially hydrated material, Ba2In2O5(H2O)0.30, the occupation of the H(3) site and subsequent long-range diffusion are not observed, which is rationalized by hindered dynamics of H(2) protons in the vicinity of oxygen vacancies. A comparison to state-of-the-art proton-conducting oxides, such as barium zirconate-based materials, suggests that the generally lower proton conductivity in Ba2In2O5(H2O)x is due to a large occupation of the H(1) and H(2) sites, which, in turn, means that there are few sites available for proton diffusion. This insight suggests that the chemical substitution of indium by cations with higher oxidation states offers a novel route toward higher proton conductivity because it reduces the proton site occupancy while preserving an oxygen-vacancy-free structure.

We report a chemically programmed design and the switching characteristics of a functional metal–DNA-origami–polyoxometalate (POM) material obtained from the solution-processed assembling of biocompatible molecular precursors. The DNA origami is immobilized on the gold surface via thiolate groups and acts as a carrier (ad-layer) structure, ensuring the spatially controlled hybridization of the pre-defined six-helix bundle (6HB) positions with DNA-augmented, tris(alkoxo)-ligated Lindqvist-type polyoxovanadate (POV6) units. The DNA-confined POV6 units accept electrons in a stepwise fashion, allowing for a multi-logic function, which we directly probe using scanning tunneling electron microscopy and spectroscopy. Electron acceptance and injection into the originally non-conducting DNA structure and the subsequent release to the gold substrate depend upon the potential at the nanoscale tip and the oxidation state of POV6, as well as on the mechanism of action of POV6 countercations. By combining experiment and theory, we show that the bio-hybrid heterojunction has far-reaching potential to create a chemically controlled POM-based nano-environment with synaptic behavior.

Iodide elpasolites (or double perovskites, A2B′B″I6, B′ = M+, B″ = M3+) are predicted to be promising alternatives to lead-based perovskite semiconductors for photovoltaic and optoelectronic applications, but no iodide elpasolite has ever been definitively prepared or structurally characterized. Iodide elpasolites are widely predicted to be unstable due to favorable decomposition to the competing A3B2I9 (B = M3+) phase. Here, we report the results of synchrotron X-ray diffraction (XRD) and X-ray total scattering measurements on putative Cs2AgBiI6 nanocrystals made via anion exchange from parent Cs2AgBiBr6 nanocrystals. Rietveld refinement of XRD and pair distribution functions (PDF) data shows that these nanocrystals indeed exhibit a tetragonal (I4̅m) elpasolite structure, making them the first example of a structurally characterized iodide elpasolite. A series of experiments probing structural relaxation and the effects of surface ligation or grain size all point to the critical role of surface free energy in stabilizing the iodide elpasolite phase in these nanocrystals.

The molecular packing and orientation of conjugated polymer chains in thin films have considerable influence on the charge transport properties and performance of polymer-based optoelectronic devices. Understanding and controlling the formation of different packing geometries and textures are important for understanding structure–function relationships and the purposeful optimization of device performance. Here, we extensively study the origin of a recently discovered third crystalline form (“form III”) of the well-studied electron transporting polymer P(NDI2OD-T2) that also exhibits pronounced end-on orientation. The effects of various processing conditions on the thin-film microstructure are studied with grazing-incidence wide-angle X-ray scattering. We find that end-on oriented form III crystallites directly evolve from face-on oriented form I crystallites upon melting under the specific conditions of high molecular weight, optimum annealing temperature, and optimum film thickness. Furthermore, by studying the charge transport properties of P(NDI2OD-T2) thin films in electron-only diodes and field-effect transistors, we find that films with end-on oriented form III crystallites demonstrate a 5-fold increase in carrier mobility in diodes (vertical transport direction) and a 1.5-fold increase in electron mobility in transistors (horizontal transport direction) compared to films with either face-on form I crystallites or edge-on form II crystallites.

Low-cost, green, large-scale, room-temperature, and fast synthesis of covalent organic frameworks (COFs) represents a highly desirable issue, due to both scientific and industrial interests, but remains a big challenge. The disadvantage of the established solvothermal method for COFs is now seriously restricting their practical industrial applications. We report herein aqueous synthesis of ketoenamine- and imine-linked COFs through a two-step dissolution–precipitation (DP) strategy. Impressively, using this DP method, we can prepare five ketoenamine-linked COFs and two imine-linked COFs in an ideal synthetic process with room temperature, 5 min reaction time, and large-scale products for one batch reaction, in the absence of acetic acid. These COFs show impressively high crystallinity and porosity and potential application in iodine and uranyl capture. This ideal synthetic route will pave a powerful methodology for making functional COFs with the value of practical industrial applications.

Designing new ultraviolet nonlinear optical (NLO) crystals with strong second-harmonic generation (SHG) response and a deep ultraviolet cutoff edge is an unremitting pursuit of scientific researchers, accompanied by the key issues of how to realize a noncentrosymmetric structure with the ideal arrangement of ultraviolet NLO-active genes. Herein, a strategy that creates halogen-centered secondary building blocks with rare-earth atoms was used for further design, and we synthesized rationally an unprecedented NLO crystal Cs2La2B10O17Cl4 exhibiting the largest SHG response (2.1 × KDP) among borates with [B5O11] as the fundamental building blocks. The unique role of Cl-centered secondary building blocks in regulating the arrangement of the B–O framework and enhancing nonlinearity was discussed in detail, which will bring the researcher a perspective in designing new NLO crystals.