Showing papers on "Crystal published in 2019"
TL;DR: In this paper, a colour-tunable, ultra-long organic phosphorescence (UOP) can be tuned by varying the excitation wavelength, allowing dynamic colour tuning from the violet to the green part of the visible spectrum.
Abstract: Materials exhibiting long-lived, persistent luminescence in the visible spectrum are useful for applications in the display, information encryption and bioimaging sectors1–4. Herein, we report the development of several organic phosphors that provide colour-tunable, ultra-long organic phosphorescence (UOP). The emission colour can be tuned by varying the excitation wavelength, allowing dynamic colour tuning from the violet to the green part of the visible spectrum. Our experimental data reveal that these organic phosphors can have an ultra-long lifetime of 2.45 s and a maximum phosphorescence efficiency of 31.2%. Furthermore, we demonstrate the applications of colour-tunable UOP for use in a multicolour display and visual sensing of ultraviolet light in the range from 300 to 360 nm. The findings open the opportunity for the development of smart luminescent materials and sensors with dynamically controlled phosphorescence. Organic phosphors with ultra-long lifetimes and an emission colour that can be tuned by the excitation wavelength are reported.
467 citations
TL;DR: Rare-earth doping is identified as a general strategy for introducing local structural heterogeneity in order to enhance the piezoelectricity of relaxor ferroelectric crystals.
Abstract: High-performance piezoelectrics benefit transducers and sensors in a variety of electromechanical applications. The materials with the highest piezoelectric charge coefficients (d33) are relaxor-PbTiO3 crystals, which were discovered two decades ago. We successfully grew Sm-doped Pb(Mg1/3Nb2/3)O3-PbTiO3 (Sm-PMN-PT) single crystals with even higher d33 values ranging from 3400 to 4100 picocoulombs per newton, with variation below 20% over the as-grown crystal boule, exhibiting good property uniformity. We characterized the Sm-PMN-PT on the atomic scale with scanning transmission electron microscopy and made first-principles calculations to determine that the giant piezoelectric properties arise from the enhanced local structural heterogeneity introduced by Sm3+ dopants. Rare-earth doping is thus identified as a general strategy for introducing local structural heterogeneity in order to enhance the piezoelectricity of relaxor ferroelectric crystals.
442 citations
TL;DR: Li et al. as mentioned in this paper proposed a 2D layered perovskite-like (NH4)3Bi2I9 device that provides unique anisotropic X-ray detecting performance with different crystal directions, effective suppression of ion migration and a low detection limit of 55'nGyair's−1.
Abstract: The effective detection of X-ray radiation with low threshold is essential to many medical and industrial applications. Three-dimensional (3D) organolead trihalide and double perovskites have been shown to be suitable for direct X-ray detection. However, the sensitivity and stability of 3D perovskite X-ray detectors are limited by ion motion, and there remains a demand to develop green and stable X-ray detectors with high sensitivity and low detection limit. The emerging low-dimensional perovskites have shown promising optoelectronic properties, featuring good intrinsic stability and reduced ion migration. Inspired by this, we show that our 2D layered perovskite-like (NH4)3Bi2I9 device provides unique anisotropic X-ray detecting performance with different crystal directions, effective suppression of ion migration and a low detection limit of 55 nGyair s−1. These results will motivate new strategies to achieve a high-performance X-ray detector by utilizing 2D layered perovskite or perovskite-like materials, without requiring toxic elements. Perovskite-like materials enable different X-ray detection performance along different crystal directions. A low detection limit of 55 nGyair s−1 is demonstrated.
318 citations
TL;DR: It is proposed that hcp-NiFe possesses favorable electronic property to expedite the reaction on the NC surface, resulting higher catalytic activity for OER, and provides a new insight to design more efficient electrocatalysts by considering the crystal phase correlated electronic property.
Abstract: Tuning the crystal phase of metal alloy nanomaterials has been proved a significant way to alter their catalytic properties based on crystal structure and electronic property. Herein, we successfully developed a simple strategy to controllably synthesize a rare crystal structure of hexagonal close-packed (hcp) NiFe nanoparticle (NP) encapsulated in a N-doped carbon (NC) shell (hcp-NiFe@NC). Then, we systemically investigated the oxygen evolution reaction (OER) performance of the samples under alkaline conditions, in which the hcp-NiFe@NC exhibits superior OER activity compared to the conventional face-centered cubic (fcc) NiFe encapsulated in a N-doped carbon shell (fcc-NiFe@NC). At the current densities of 10 and 100 mA cm-2 , the hcp-NiFe@NC with Fe/Ni ratio of ≈5.4 % only needs ultralow overpotentials of 226 mV and 263 mV versus reversible hydrogen electrode in 1.0 m KOH electrolyte, respectively, which were extremely lower than those of fcc-NiFe@NC and most of other reported NiFe-based electrocatalysts. We proposed that hcp-NiFe possesses favorable electronic property to expedite the reaction on the NC surface, resulting higher catalytic activity for OER. This research provides a new insight to design more efficient electrocatalysts by considering the crystal phase correlated electronic property.
235 citations
TL;DR: In this article, a layered manganese oxide that contains a high content of crystal water (∼10 wt%) as an aqueous zinc battery cathode was reported.
Abstract: Aqueous zinc (Zn)-ion batteries are gaining considerable attention as grid-scale energy storage systems due to their advantages in rate performance, cost, and safety. Here, we report a layered manganese oxide that contains a high content of crystal water (∼10 wt%) as an aqueous zinc battery cathode. The interlayer crystal water can effectively screen the electrostatic interactions between Zn2+ ions and the host framework to facilitate Zn2+ diffusion while sustaining the host framework for prolonged cycles. By virtue of these ‘water’ effects, this material exhibits a high reversible capacity of 350 mA h g−1 at 100 mA g−1, along with decent cycling and rate performance, in a two-electrode cell configuration. Density functional theory (DFT) calculations and extended X-ray absorption fine structure (EXAFS) analyses jointly reveal that upon Zn2+ ion intercalation, a stable inner-sphere Zn-complex coordinated with water molecules is formed, followed by the formation of a Zn–Mn dumbbell structure, which gives a clue for the observed electrochemical performance. This work unveils the useful function of crystal water in enhancing the key electrochemical performance of emerging divalent battery electrodes.
228 citations
TL;DR: It is found that submicrometer-size magnesium samples exhibit high plasticity that is far greater than for their bulk counterparts, which should allow development of high-ductility magnesium and other metal alloys.
Abstract: Lightweight magnesium alloys are attractive as structural materials for improving energy efficiency in applications such as weight reduction of transportation vehicles. One major obstacle for widespread applications is the limited ductility of magnesium, which has been attributed to [Formula: see text] dislocations failing to accommodate plastic strain. We demonstrate, using in situ transmission electron microscope mechanical testing, that [Formula: see text] dislocations of various characters can accommodate considerable plasticity through gliding on pyramidal planes. We found that submicrometer-size magnesium samples exhibit high plasticity that is far greater than for their bulk counterparts. Small crystal size usually brings high stress, which in turn activates more [Formula: see text] dislocations in magnesium to accommodate plasticity, leading to both high strength and good plasticity.
226 citations
TL;DR: In this article, a simple solvothermal reaction was developed to synthesize the novel lanthanum-doped UiO-66, which can be generated in the process of doping.
222 citations
TL;DR: In this paper, a van der Waals crystal, α-MoO3, is shown to support in-plane hyperbolic polariton guided modes at mid-infrared frequencies without the need for patterning.
Abstract: Hyperbolic media have attracted much attention in the photonics community due to their ability to confine light to arbitrarily small volumes and their potential applications to super-resolution technologies. The two-dimensional counterparts of these media can be achieved with hyperbolic metasurfaces that support in-plane hyperbolic guided modes upon nanopatterning, which, however, poses notable fabrication challenges and limits the achievable confinement. We show that thin flakes of a van der Waals crystal, α-MoO3, can support naturally in-plane hyperbolic polariton guided modes at mid-infrared frequencies without the need for patterning. This is possible because α-MoO3 is a biaxial hyperbolic crystal with three different Reststrahlen bands, each corresponding to a different crystalline axis. These findings can pave the way toward a new paradigm to manipulate and confine light in planar photonic devices.
215 citations
183 citations
TL;DR: In this paper, a reliable sol-gel approach, which combines the formation of ZnO nanocrystals and a solvent driven, shape-controlled, crystal growth process to form well-organized ZnOsO nanostructures at low temperature is presented.
Abstract: A reliable sol–gel approach, which combines the formation of ZnO nanocrystals and a solvent driven, shape-controlled, crystal-growth process to form well-organized ZnO nanostructures at low temperature is presented. The sol of ZnO nanocrystals showed shape-controlled crystal growth with respect to the solvent type, resulting in either nanorods, nanoparticles, or nanoslates. The solvothermal process, along with the solvent polarity facilitate the shape-controlled crystal growth process, augmenting the concept of a selective adhesion of solvents onto crystal facets and controlling the final shape of the nanostructures. The XRD traces and XPS spectra support the concept of selective adhesion of solvents onto crystal facets that leads to yield different ZnO morphologies. The shift in optical absorption maxima from 332 nm in initial precursor solution, to 347 nm for ZnO nanocrystals sol, and finally to 375 nm for ZnO nanorods, evidenced the gradual growth and ripening of nanocrystals to dimensional nanostructures. The engineered optical band gaps of ZnO nanostructures are found to be ranged from 3.10 eV to 3.37 eV with respect to the ZnO nanostructures formed in different solvent systems. The theoretical band gaps computed from the experimental XRD spectral traces lie within the range of the optical band gaps obtained from UV-visible spectra of ZnO nanostructures. The spin-casted thin film of ZnO nanorods prepared in DMF exhibits the electrical conductivity of 1.14 × 10−3 S cm−1, which is nearly one order of magnitude higher than the electrical conductivity of ZnO nanoparticles formed in hydroquinone and ZnO sols. The possibility of engineering the band gap and electrical properties of ZnO at nanoscale utilizing an aqueous-based wet chemical synthesis process presented here is simple, versatile, and environmentally friendly, and thus may applicable for making other types of band-gap engineered metal oxide nanostructures with shape-controlled morphologies and optoelectrical properties.
177 citations
TL;DR: It is demonstrated that transport under steady-state illumination is considerably altered at the structural phase transition in the MA compounds, providing advanced insights into the evolution of the crystal structure with decreasing temperature that are essential to interpret the growing interest in investigating the electronic, optical, and photonic properties of lead-halide perovskite materials.
Abstract: The extraordinary properties of lead-halide perovskite materials have spurred intense research, as they have a realistic perspective to play an important role in future photovoltaic devices. It is known that these materials undergo a number of structural phase transitions as a function of temperature that markedly alter their optical and electronic properties. The precise phase transition temperature and exact crystal structure in each phase, however, are controversially discussed in the literature. The linear thermal expansion of single crystals of APbX3 (A = methylammonium (MA), formamidinium (FA); X = I, Br) below room temperature is measured using a high-resolution capacitive dilatometer to determine the phase transition temperatures. For δ-FAPbI3 , two wide regions of negative thermal expansion below 173 and 54 K, and a cascade of sharp transitions for FAPbBr3 that have not previously been reported are uncovered. Their respective crystal phases are identified via powder X-ray diffraction. Moreover, it is demonstrated that transport under steady-state illumination is considerably altered at the structural phase transition in the MA compounds. The results provide advanced insights into the evolution of the crystal structure with decreasing temperature that are essential to interpret the growing interest in investigating the electronic, optical, and photonic properties of lead-halide perovskite materials.
TL;DR: A simulation of the effect of the crystallite size on the shape and width of the X-ray patterns was done using PDF-4 software which confirmed that raw ordered bone crystals produce broad peaks which so far have been erroneously assigned to polycrystalline hydroxyapatite with low crystalline quality.
Abstract: This paper focuses on the study of the effect of the change of the crystal size on the shape and width of the X-ray diffraction patterns for defatted and deproteinized bones as well as incinerated biogenic hydroxyapatite obtained from bovine, porcine, and human bones. Inductively Couple Plasma showed the presence of some ions such as Mg, K, Al, Fe, Zn, and Na for all samples. The nanometric size of the crystals was determined through High Resolution Transmission Electron Microscopy in which ordered crystals were found. The calcination of raw clean bones at 720 °C produced a transition of crystal size from nano to micro due to a coalescence phenomenon, this was accompanied by a decrease of the peak width of the X-ray diffraction patterns due to the decrease of the inelastic scattering contribution from the microcrystals. A simulation of the effect of the crystallite size on the shape and width of the X-ray patterns was done using PDF-4 software which confirmed that raw ordered bone crystals produce broad peaks which so far have been erroneously assigned to polycrystalline hydroxyapatite with low crystalline quality.
TL;DR: Analysis of van der Waals crystal VI3 reveals that it exhibits a structural transition from monoclinic C2/ m to rhombohedral R3̅ at Ts ≈ 79 K, similar to CrX3, and is a candidate for two-dimensional FM semiconductors.
Abstract: We report structural properties, physical properties, and the electronic structure of van der Waals (vdW) crystal VI3. Detailed analysis reveals that VI3 exhibits a structural transition from monoc...
TL;DR: This paper reviews the progresses achieved in zeolite morphology control and investigates theZeolite crystallization and crystal assembly mechanisms are investigated for providing an overall insight into the regulation of zeolites crystal morphology.
Abstract: Aluminosilicate zeolites with controllable morphology have attracted considerable attention due to their potential applications in catalysis, adsorption, and separation technologies, as well as the biomedical field. However, the rational design and preparation of zeolites with the required morphology have not been achieved because the zeolite crystallization mechanism has not been fully understood, and therefore, the nucleation and crystal growth processes cannot be oriented. This paper reviews the progresses achieved in zeolite morphology control. The chemical compositions of the synthesis gel, including template (or the structure-directing agent) and framework heteroatoms, silica and alumina sources, alkali metal cations and mineralization ions, crystallization conditions, and synthesis methods have a considerable impact on the crystal morphology. The oriented assembly of zeolite crystals into special morphologies, such as hierarchical porous structures, zeolite membranes, hollow zeolite spheres, and core@shell-structured zeolites, can be realized by using soft and/or hard template methods and adjusting the synthesis and crystallization conditions. In addition, zeolite crystallization and crystal assembly mechanisms are investigated for providing an overall insight into the regulation of zeolite crystal morphology.
TL;DR: The cross-linked porous mesh structures growing on the {001} crystal plane strengthen the mixing with conductive carbon, inducing preferable conductivity, as well as increasing the area of ion contact and the number of active sites, enable the hexagonal Ni-MOF to exhibit excellent electrochemical performance as supercapacitor electrode materials.
Abstract: Hexagonal nickel-organic framework (Ni-MOF) [Ni(NO3 )2 ·6H2 O, 1,3,5-benzenetricarboxylic acid, 4-4'-bipyridine] is fabricated through a one-step solvothermal method. The {001} crystal plane is exposed to the largest hexagonal surface, which is an ideal structure for electron transport and ion diffusion. Compared with the surrounding rectangular crystal surface, the ion diffusion length through the {001} crystal plane is the shortest. In addition, the cross-linked porous mesh structures growing on the {001} crystal plane strengthen the mixing with conductive carbon, inducing preferable conductivity, as well as increasing the area of ion contact and the number of active sites. These advantages enable the hexagonal Ni-MOF to exhibit excellent electrochemical performance as supercapacitor electrode materials. In a three-electrode cell, specific capacitance of hexagonal Ni-MOF in the 3.0 m KOH electrolyte is 977.04 F g-1 and remains at the initial value of 92.34% after 5,000 cycles. When the hexagonal Ni-MOF and activated carbon are assembled into aqueous devices, the electrochemical performance remains effective.
TL;DR: In this paper, the inner chemical etching reactivity of a crystal can be enhanced at the nanoscale by means of direct laser writing, which allows to produce cm-scale arbitrary three-dimensional nanostructures with 100 nm feature sizes inside large crystals in absence of brittle fracture.
Abstract: Nanostructuring hard optical crystals has so far been exclusively feasible at their surface, as stress induced crack formation and propagation has rendered high precision volume processes ineffective. We show that the inner chemical etching reactivity of a crystal can be enhanced at the nanoscale by more than five orders of magnitude by means of direct laser writing. The process allows to produce cm-scale arbitrary three-dimensional nanostructures with 100 nm feature sizes inside large crystals in absence of brittle fracture. To showcase the unique potential of the technique, we fabricate photonic structures such as sub-wavelength diffraction gratings and nanostructured optical waveguides capable of sustaining sub-wavelength propagating modes inside yttrium aluminum garnet crystals. This technique could enable the transfer of concepts from nanophotonics to the fields of solid state lasers and crystal optics.
TL;DR: In this paper, the authors focused on the glass forming, crystallization, and physical properties of ZnO doped MgO-Al2O3-SiO2-B 2O3 glass-ceramics and revealed a rational mechanism of glass formation, crystal precipitation, and evolution between structure and performance.
Abstract: This study focused on the glass forming, crystallization, and physical properties of ZnO doped MgO-Al2O3-SiO2-B2O3 glass-ceramics. The results show that the glass forming ability enhances first with ZnO increasing from 0 to 0.5 mol%, and then weakens with further addition of ZnO which acted as network modifier. No nucleating agent was used and the crystallization of studied glasses is controlled by a surface crystallization mechanism. The predominant phase in glass-ceramics changed from α-cordierite to spinel/gahnite as ZnO gradually replaced MgO. The phase type did not change; however, the crystallinity and grain size in glass-ceramics increased when the glasses were treated from 1030 °C to 1100 °C. The introduction of ZnO can improve the thermal, mechanical, and dielectric properties of the glass-ceramics. The results reveal a rational mechanism of glass formation, crystal precipitation, and evolution between structure and performance in the xZnO-(20-x)MgO-20Al2O3-57SiO2-3B2O3 (0 ≤ x ≤ 20 mol%) system.
TL;DR: Density functional theory calculations reveal that the FA/MA ratio affects the surface energy of the mixed perovskites, leading to the variation of preferential orientation consequently, and the present work provides a vital step in understanding the intrinsic properties of mixed-cation Perovskite optoelectronics.
Abstract: Crystal orientation has a great impact on the properties of perovskite films and the resultant device performance. Up to now, the exquisite control of crystal orientation (the preferred crystallographic planes and the crystal stacking mode with respect to the particular planes) in mixed-cation perovskites has received limited success, and the underlying mechanism that governs device performance is still not clear. Here, a thermodynamically favored crystal orientation in formamidinium/methylammonium (FA/MA) mixed-cation perovskites is finely tuned by composition engineering. Density functional theory calculations reveal that the FA/MA ratio affects the surface energy of the mixed perovskites, leading to the variation of preferential orientation consequently. The preferable growth along the (001) crystal plane, when lying parallel to the substrates, affects their charge transportation and collection properties. Under the optimized condition, the mixed-cation perovskite (FA1- x MAx PbI2.87 Br0.13 (Cl)) solar cells deliver a champion power conversion efficiency over 21%, with a certified efficiency of 20.50 ± 0.50%. The present work not only provides a vital step in understanding the intrinsic properties of mixed-cation perovskites but also lays the foundation for further investigation and application in perovskite optoelectronics.
TL;DR: Hydrogen bonds containing spacers are used to synthesize highly luminescent perovskites with fully isolated lead-bromide octahedras and shed light on the origin of the emission.
Abstract: As one of next-generation semiconductors, hybrid halide perovskites with tailorable optoelectronic properties are promising for photovoltaics, lighting, and displaying. This tunability lies on variable crystal structures, wherein the spatial arrangement of halide octahedra is essential to determine the assembly behavior and materials properties. Herein, we report to manipulate their assembling behavior and crystal dimensionality by locally collective hydrogen bonding effects. Specifically, a unique urea-amide cation is employed to form corrugated 1D crystals by interacting with bromide atoms in lead octahedra via multiple hydrogen bonds. Further tuning the stoichiometry, cations are bonded with water molecules to create a larger spacer that isolates individual lead bromide octahedra. It leads to zero-dimension (0D) single crystals, which exhibit broadband 'warm' white emission with photoluminescence quantum efficiency 5 times higher than 1D counterpart. This work suggests a feasible strategy to modulate the connectivity of octahedra and consequent crystal dimensionality for the enhancement of their optoelectronic properties.
TL;DR: The room-temperature phosphorescent DBBZL crystals could exhibit reversible bending and irreversible bending based on one crystal, demonstrating the application of flexibility.
Abstract: Recently, the study of flexible (elastically bendable and plastically bendable) organic single crystals has become a hot research field in crystal engineering. In general, crystal elasticity and plasticity are incompatible with each other. Different from the applications of fluorescent crystals, the applications of room-temperature phosphorescence (RTP) materials generally ignore the crystallographic nature of large single crystals. Herein, we creatively combine elasticity and plasticity based on one RTP crystal 4,4′-dibromobenzil DBBZL. The in-depth study of the irreversible transformation between elastic bending and plastic bending provided important insights into the mechanism of both elastically bendable crystals and plastically bendable crystals in crystal engineering. The DBBZL crystal exhibits elastic bending (reversible) under external stress, whereas it shows plastic bending (irreversible) after excessive bending. Notably, the first phosphorescent optical waveguides of large single RTP crystals are realized not only in straight state, but also in elastic bent state and plastic bent state.
TL;DR: In this paper, the synergetic optimization of electronic and thermal transport properties in rhombohedral GeTe doped with transition metal Ti is reported, where the Seebeck coefficient of Ge1-xTixTe is significantly increased and the corresponding thermal conductivity is decreased.
TL;DR: In this paper, Li-ion conductor materials are comprised of a mobile L-ion sublattice hosted in a crystal structural framework of immobile polyanion groups, which facilitates the transport of a large number of Li ions and yields high ionic conductivity.
Abstract: DOI: 10.1002/aenm.201902078 replacement of liquid electrolyte and has the potential to achieve improved safety, higher energy density, and longer cycle life than current commercial lithiumion batteries with liquid electrolytes.[17] Despite significant research efforts, only a few Li SIC materials exhibit an ionic conductivity of >10−3 S cm−1 at room temperature, and some Li SICs suffer from limited stability, poor interfacial compatibility, or high cost in processing and manufacturing.[6,7,18] A strong need exists for fundamental understanding of these SIC materials in order to design and discover new Li SIC materials. A Li-ion conductor material is comprised of a mobile Li-ion sublattice hosted in a crystal structural framework of immobile polyanion groups. The empty space in between these polyanion groups hosts Li ions as Li sites and forms interconnected channels. Li ions migrate among the sites through these channels, contributing to overall ionic transport. Well-known crystal structural frameworks of SICs include NASICON structure of LiM2(PO4)3 (M = Ge, Ti, Sn, Hf, Zr) compositions,[19] garnet structure of LixLa3M2O12 (5 ≤ x ≤ 7, M = Nb, Ta, Sb, Zr, Sn) compositions,[20] and LGPS-type structure of Li10+xM1+xP2−xS12 (0 ≤ x ≤ 1, M = Si, Ge, Sn) compositions.[21] Recent studies have demonstrated that the crystal structural framework determines Li sites, migration pathways, and the energy landscape, and particular crystal structural frameworks are optimal for low energy barrier Li ion migration.[10,22,23] For example, the crystal structural framework with a body-centered cubic (bcc) anion sublattice, such as found in LGPS and Li7P3S11, has been shown to have an energy landscape with the lowest barrier compared to other anion sublattices, such as in facecentered cubic and hexagonal close packed sublattices.[10] However, some SICs with crystal structural frameworks of non-bcc anion sublattices, such as lithium garnet (e.g., LLZO) and lithium NASICON (e.g., LATP), also exhibit high Li+ conductivities as high as ≈10−3 S cm−1 at RT. It remains an open question as to what features of these crystal structure frameworks enable super-ionic conduction. Due to their unique crystal structural frameworks, SIC materials have highly mobile Li-ion sublattices, which are drastically different from those in typical solids (Figure 1). The disordered Li sublattice of SICs facilitates the transport of a large number of Li ions and yields high ionic conductivity. In the disordered Li sublattice, the Li-ion diffusion mechanism is also distinctive As technologically important materials for solid-state batteries, Li superionic conductors are a class of materials exhibiting exceptionally high ionic conductivity at room temperature. These materials have unique crystal structural frameworks hosting a highly conductive Li sublattice. However, it is not understood why certain crystal structures of the super-ionic conductors lead to high conductivity in the Li sublattice. In this study, using topological analysis and ab initio molecular dynamics simulations, the crystal structures of all Li-conducting oxides and sulfides are studied systematically and the key features pertaining to fast-ion conduction are quantified. In particular, a unique feature of enlarged Li sites caused by large local spaces in the crystal structural framework is identified, promoting fast conduction in the Li-ion sublattice. Based on these quantified features, the high-throughput screening identifies many new structures as fast Li-ion conductors, which are further confirmed by ab initio molecular dynamics simulations. This study provides new insights and a systematic quantitative understanding of the crystal structural frameworks of fast ion-conductor materials and motivates future experimental and computational studies on new fast-ion conductors.
TL;DR: In this paper, a critical review summarizes recent progress in the design and tailoring of diversified Bi-based ultrathin materials for various photocatalytic applications, such as crystal facet control, bismuth enrichment strategy, surface adjustment, heteroatom doping, defect engineering, co-catalyst modification, and utilization of solid solutions, single atoms, and heterojunctions.
Abstract: The emerging ultrathin materials with a suitable energy band structure have been regarded as a new type of photocatalyst. Among them, bismuth-based ultrathin materials display intriguing photocatalytic performance due to the unique structural and electronic properties, strong light response and appealing energy band structure. This critical review summarizes recent progress in the design and tailoring of diversified Bi-based ultrathin materials for various photocatalytic applications. We start with the introduction from the crystal structure, materials design and synthesis of various Bi-based ultrathin photocatalysts, such as bismuth oxide, bismuth oxyhalides, Bi2WO6, Bi2MoO6, BiVO4 and so on. Then, strategies for local atomic arrangement, electronic structure, and carrier concentration tuning, so as to boost the performance, are summarized, such as crystal facet control, bismuth-enrichment strategy, surface adjustment, heteroatom doping, defect engineering, co-catalyst modification, and utilization of solid solutions, single atoms, and heterojunctions. Furthermore, advancements of versatile photocatalytic applications over Bi-based ultrathin materials are discussed, including oxygen evolution, hydrogen evolution, organic syntheses, CO2 reduction, N2 reduction, and pollutant removal, with an emphasis on the structure–activity relationship. Finally, the existing challenges and future research opportunities are also presented.
TL;DR: In this paper, the spontaneous polarization of barium ferrites partially substituted with In, Al, Ga and Sc ions was found out in solid solutions, partially substituting with In and Al ions that is an evidence of their ferroelectric properties.
TL;DR: In this article, the authors examined earth-abundant, metal-free, graphitic C3N4 with exceptional optical and electronic properties, excellent chemical and thermal stability, an appropriate band gap, and non-toxicity for QLED applications.
TL;DR: In this article, a phononic crystal plate made of soft material with resonant units is proposed, where each resonant unit consists of a mass which is connected to the perforated plate by thin beams.
TL;DR: The authors show the synthesis of monolayer Sb2O3 molecular crystals on mica substrates by passivator-assisted vapor deposition, which can be extended to the controlled growth of other two-dimensional inorganic molecular crystals and open up opportunities for potential molecular electronic devices.
Abstract: Two-dimensional molecular crystals, consisting of zero-dimensional molecules, are very appealing due to their novel physical properties. However, they are mostly limited to organic molecules. The synthesis of inorganic version of two-dimensional molecular crystals is still a challenge due to the difficulties in controlling the crystal phase and growth plane. Here, we design a passivator-assisted vapor deposition method for the growth of two-dimensional Sb2O3 inorganic molecular crystals as thin as monolayer. The passivator can prevent the heterophase nucleation and suppress the growth of low-energy planes, and enable the molecule-by-molecule lateral growth along high-energy planes. Using Raman spectroscopy and in situ transmission electron microscopy, we show that the insulating α-phase of Sb2O3 flakes can be transformed into semiconducting β-phase under heat and electron-beam irradiation. Our findings can be extended to the controlled growth of other two-dimensional inorganic molecular crystals and open up opportunities for potential molecular electronic devices.
TL;DR: Here, it is discussed how the effects of the elastic and plastic deformation of molecular crystals on the diffraction signature give primary evidence of their degree of crystallinity.
Abstract: The mention of the word "crystal" invokes images of minerals, gems, and rocks, all of which are inevitably solid, hard, and durable entities with well-defined smooth faces and straight edges. With the discovery in the first half of the 20th century that many molecular crystals are soft and can be deformed in a similar way as rubber or plastic, this perception is changing, and both the concept and formal definition of what a crystal is may require reinterpretation. The seemingly naive question posed in the title of this Minireview does not have a simple answer. Here, we discuss how the effects of the elastic and plastic deformation of molecular crystals on the diffraction signature give primary evidence of their degree of crystallinity. In most cases, the definition of a crystal holds for both elastically and plastically deformed crystals and, unless there is significant or complete physical separation of the crystal during the deformation, they can safely be considered (deformed) single crystals with a high concentration of defects.