Deciphering the Atomic-Scale Structural Origin for Photoluminescence Quenching in Tin-Lead Alloyed Perovskite Nanocrystals.

The development of tin-lead alloyed halide perovskite nanocrystals (PNCs) is highly desirable for creating ultrastable, eco-friendly optoelectronic applications. However, the current incorporation of tin into the lead matrix results in severe photoluminescence (PL) quenching. To date, the precise atomic-scale structural origins of this quenching are still unknown, representing a significant barrier to fully realizing the potential of these materials. Here, we uncover the distinctive defect-related microstructures responsible for PL quenching using atomic-resolution scanning transmission electron microscopy and theoretical calculations. Our findings reveal an increase in point defects and Ruddlesden-Popper (RP) planar faults with increasing tin content. Notably, the point defects include a spectrum of vacancies and previously overlooked antisite defects with bromide vacancies and cation antisite defects emerging as the primary contributors to deep-level defects. Furthermore, the RP planar faults exhibit not only the typical rock-salt stacking pattern found in pure Pb-based PNCs but also previously undocumented microstructures rich in bromide vacancies and deep-level cation antisite defects. Direct strain imaging uncovers severe lattice distortion and significant inhomogeneous strain distributions caused by point defect aggregation, potentially breaking the local force balance and driving RP planar fault formation via lattice slippage. Our work illuminates the nature and evolution of defects in tin-lead alloyed halide perovskite nanocrystals and their profound impact on PL quenching, providing insights that support future material strategies in the development of less toxic tin-lead alloyed perovskite nanocrystals.

Charged Exciton Generation by Curvature-Induced Band Gap Fluctuations in Structurally Disordered Two-Dimensional Semiconductors.

Curvature is a general factor for various two-dimensional (2D) materials due to their flexibility, which is not yet fully unveiled to control their physical properties. In particular, the effect of structural disorder with random curvature formation on excitons in 2D semiconductors is not fully understood. Here, the correlation between structural disorder and exciton formation in monolayer MoS2 on SiO2 was investigated by using photoluminescence (PL) and Raman spectroscopy. We found that the curvature-induced charge localization along with band gap fluctuations aid the formation of the localized charged excitons (such as trions). In the substrate-supported region, the trion population is enhanced by a localized charge due to the microscopic random bending strain, while the trion is suppressed in the suspended region which exhibits negligible bending strain, anomalously even though the dielectric screening effect is lower than that of the supported region. The redistribution of each exciton by the bending strain leads to a huge variation (∼100-fold) in PL intensity between the supported and suspended regions, which cannot be fully comprehended by external potential disorders such as a random distribution of charged impurities. The peak position of PL in MoS2/SiO2 is inversely proportional to the Raman peak position of E12g, indicating that the bending strain is correlated with PL. The supported regions exhibit an indirect portion that was not shown in the suspended regions or atomically flat substrates. The understanding of the structural disorder effect on excitons provides a fundamental path for optoelectronics and strain engineering of 2D semiconductors.

Giant Modulation of Refractive Index from Picoscale Atomic Displacements.

It is shown that structural disorder-in the form of anisotropic, picoscale atomic displacements-modulates the refractive index tensor and results in the giant optical anisotropy observed in BaTiS3, a quasi-1D hexagonal chalcogenide. Single-crystal X-ray diffraction studies reveal the presence of antipolar displacements of Ti atoms within adjacent TiS6 chains along the c-axis, and threefold degenerate Ti displacements in the a-b plane. 47/49Ti solid-state NMR provides additional evidence for those Ti displacements in the form of a three-horned NMR lineshape resulting from a low symmetry local environment around Ti atoms. Scanning transmission electron microscopy is used to directly observe the globally disordered Ti a-b plane displacements and find them to be ordered locally over a few unit cells. First-principles calculations show that the Ti a-b plane displacements selectively reduce the refractive index along the ab-plane, while having minimal impact on the refractive index along the chain direction, thus resulting in a giant enhancement in the optical anisotropy. By showing a strong connection between structural disorder with picoscale displacements and the optical response in BaTiS3, this study opens a pathway for designing optical materials with high refractive index and functionalities such as large optical anisotropy and nonlinearity.

Sequence-based prediction of the effects of histones H1 post-translational modifications: impact on the features related to the function.

Post-translational modifications modulate histones H1 activity but their impact on proteins features was not studied so far. Therefore, this work was intended to answer how the most common modifications, i.e. acetylation, methylation, phosphorylation and ubiquitination, can influence on histones H1 to alter their physicochemical and molecular properties. Investigations were done with the use of sequence-based predictors trained on various protein features. Because a full set of histones H1 modifications is not included in the databases of histone proteins, the survey was performed on the human, animals, plants, fungi and protist sequences selected from UniProtKB/Swiss-Prot database. Quantitative proportions of modifications were similar between the groups of organisms (CV = 0.11) but different within the group (p < 0.05). The effects of modifications were evaluated with the use of mutated sequences obtained through the substitution of modified residue of Lys, Ser and Thr by a neutral residue of the Ala. An advantage of deleterious mutations at the sites of acetylation, methylation and ubiquitination over the sites of phosphorylation (p < 0.05) indicate that this modification have more redundant character. Modifications evoke an increase of protein solubility and stability as well as acceleration of folding kinetics and a weaken of binding affinity. Besides, they also maintain a higher extent of intrinsic structural disorder. The obtained results prove that modifications should be perceived as relevant factors influencing physicochemical features determining molecular properties. Thus, histones H1 functioning is strictly correlated with the status of modifications.Communicated by Ramaswamy H. Sarma.

Structural Stability and Disorder Level of Moderately Reduced Paper-like Graphene Oxide Investigated with Micro-Raman Analysis.

This paper discusses the results of the micro-Raman analysis performed on paper-like graphene oxide (GO) samples consisting of many functionalised graphene layers and annealed at moderate temperatures (≤500 °C) under vacuum conditions (p ≃ 10-4 mbar). The analysis of the standalone samples revealed that the obtained material is characterised by a noticeable disorder level but still stays below the commonly accepted threshold of high or total disorder. GO formed in a simple way showed two spectral bands above 1650 cm-1 recorded very rarely or not at all and their origin has been discussed in detail. The results also confirmed the metastable character of multilayer GO after the annealing process at moderate temperatures as the C/O ratio was kept between 2 and 3 and the spectral features were stable within the annealing temperature range.

Amorphous Materials for Lithium-Ion and Post-Lithium-Ion Batteries.

Lithium-ion and post-lithium-ion batteries are important components for building sustainable energy systems. They usually consist of a cathode, an anode, an electrolyte, and a separator. Recently, the use of solid-state materials as electrolytes has received extensive attention. The solid-state electrolyte materials (as well as the electrode materials) have traditionally been overwhelmingly crystalline materials, but amorphous (disordered) materials are gradually emerging as important alternatives because they can increase the number of ion storage sites and diffusion channels, enhance solid-state ion diffusion, tolerate more severe volume changes, and improve reaction activity. To develop superior amorphous battery materials, researchers have conducted a variety of experiments and theoretical simulations. This review highlights the recent advances in using amorphous materials (AMs) for fabricating lithium-ion and post-lithium-ion batteries, focusing on the correlation between material structure and properties (e.g., electrochemical, mechanical, chemical, and thermal ones).  We  review both the conventional and the emerging characterization methods for analyzing AMs and present the roles of disorder in influencing the performances of various batteries such as those based on lithium, sodium, potassium, and zinc. Finally,  we  describe the challenges and perspectives for commercializing rechargeable AMs-based batteries.

Correlating Structural Disorder in Metal (Oxy)hydroxides and Catalytic Activity in Electrocatalytic Oxygen Evolution.

Understanding the correlation between the structural evolution of electrocatalysts and their catalytic activity is both essential and challenging. In this study, we investigate this correlation in the context of the oxygen evolution reaction (OER) by examining the influence of structural disorder during and after dynamic structural evolution on the OER activity of Fe-Ni (oxy)hydroxide catalysts using operando X-ray absorption spectroscopy, alongside other experiments and theoretical calculations. The Debye-Waller factors obtained from extended X-ray absorption fine structure analyses reflect the degree of structural disorder and exhibit a robust correlation with the intrinsic OER activities of the electrocatalysts. The enhanced OER activity of in situ-generated metal (oxy)hydroxides derived from different pre-catalysts is linked to increased structural disorder, offering a promising approach for designing efficient OER electrocatalysts. This strategy may inspire similar investigations in related electrocatalytic energy-conversion systems.

Phase Transitions in Boron Carbide.

The idealized rhombohedral unit cell of boron carbide is formed by a 12-atom icosahedron and a 3-atom linear chain. Phase transitions are second order and caused by the exchange of B and C sites or by vacancies in the structure. Nevertheless, the impact of such minimal structural changes on the properties can be significant. As the X-ray scattering cross sections of B and C isotopes are very similar, the capability of X-ray fine structure investigation is substantially restricted. Phonon spectroscopy helps close this gap as the frequency and strength of phonons sensitively depend on the bonding force and mass of the vibrating atoms concerned. Phase transitions known to date have been identified due to significant changes of properties: (1) The phase transition near the chemical composition B8C by clear change of the electronic structure; (2) the endothermic temperature-dependent phase transition at 712 K according to the change of specific heat; (3) the high-pressure phase transition at 33.2 GPa by the drastic change of optical appearance from opacity to transparency. These phase transitions affect IR- and Raman-active phonons and other solid-state properties. The phase transitions at B~8C and 712 K mean that a well-defined distorted structure is converted into another one. In the high-pressure phase transition, an apparently well-defined distorted structure changes into a highly ordered one. In all these cases, the distribution of polar C atoms in the icosahedra plays a crucial role.

Disorder effect on intersubband optical absorption ofn-typeδ-doped quantum well in GaAs.

The inevitable structural disorder associated with the fluctuation of the applied external electric field, laser intensity, and bidimensional density in the low dimensional quantum system can affect noticeably optical absorption properties and the related phenomena. In this work, we study the effect of structural disorder on the optical absorption properties in delta-doped quantum wells (DDQWs). Starting from effective mass approximation and the Thomas-Fermi approach as well as using the matrix density, the electronic structure and the optical absorption coefficients of DDQWs are determined. It is found that the optical absorption properties depend on the strength and the type of structural disorder. Particularly, the bidimensional density disorder suppresses strongly the optical properties. Whilst, the disordered external applied electric field fluctuates moderately in the properties. In contrast, the disordered laser holds absorption properties unalterable. So, our results specify that to have and preserve good optical absorption properties in DDQWs, requires precise control of the bidimensional. Besides, the finding may improve the understanding of the impact of the disorder on the optoelectronic properties based on DDQWs.

Phase segregation and miscibility of TiOx nanocomposites in Gd-doped ceria solid electrolyte material.

Electro-chemo-mechanical (ECM) coupling refers to mechanical deformation due to electrochemically driven compositional change in a solid. An ECM actuator producing micrometre-size displacements and long-term stability at room temperature was recently reported, comprising a 20 mol% Gd-doped ceria (20GDC), a solid electrolyte membrane, placed between two working bodies made of TiOx/20GDC (Ti-GDC) nanocomposites with Ti concentration of 38 mol%. The volumetric changes originating from oxidation or reduction in the local TiOx units are hypothesized to be the origin of mechanical deformation in the ECM actuator. Studying the Ti concentration-dependent structural changes in the Ti-GDC nanocomposites is therefore required for (i) understanding the mechanism of dimensional changes in the ECM actuator and (ii) maximizing the ECM response. Here, the systematic investigation of the local structure of the Ti and Ce ions in Ti-GDC over a broad range of Ti concentrations using synchrotron X-ray absorption spectroscopy and X-ray diffraction is reported. The main finding is that, depending on the Ti concentration, Ti atoms either form a cerium titanate or segregate into a TiO2 anatase-like phase. The transition region between these two regimes with Ti(IV) concentration between 19% and 57% contained strongly disordered TiOx units dispersed in 20GDC containing Ce(III) and Ce(IV) and hence rich with oxygen vacancies. As a result, this transition region is proposed to be the most advantageous for developing ECM-active materials.

Role of structural disorder in the vibrational spectra of sol-gel γ and δ-Al2O3 nanoparticles.

Alumina nanopowders belonging to the γ and δ transition phases have been characterized by infrared and Raman spectroscopies. A quantitative interpretation of their vibrational spectra has been provided and related to their crystal structure, with particular emphasis on structural disorder and features not predicted by group-theoretical considerations. Both phases show very similar infrared dielectric functions, but with clear instances of mode-splitting in the δ phase, which are related to ordering in the tetrahedral Al positions. Raman spectroscopy was unable to resolve any modes in the sample identified as γ phase, but the full lattice vibrational region could be measured for the δ sample under UV and red excitation lines. Raman spectra are more complex than those obtained by infrared spectroscopy and cannot be completely explained by factor group analysis, in the absence of dedicated theoretical studies. Finally, the luminescent properties of these materials have been qualitatively explored and linked to disorder and substitutional impurities. In general, the results contained in this work prove that vibrational spectroscopies are powerful tools for quantitative analyses of these disordered nanomaterials and suggest the need for more theoretical work to understand their vibrational properties.

Crystal Chemistry of the Copper Oxalate Biomineral Moolooite: The First Single-Crystal X-ray Diffraction Studies and Thermal Behavior.

Moolooite, Cu(C2O4)·nH2O, is a typical biomineral which forms due to Cu-bearing minerals coming into contact with oxalic acid sources such as bird guano deposits or lichens, and no single crystals of moolooite of either natural or synthetic origin have been found yet. This paper reports, for the first time, on the preparation of single crystals of a synthetic analog of the copper-oxalate biomineral moolooite, and on the refinement of its crystal structure from the single-crystal X-ray diffraction (SCXRD) data. Along with the structural model, the SCXRD experiment showed the significant contribution of diffuse scattering to the overall diffraction data, which comes from the nanostructural disorder caused by stacking faults of Cu oxalate chains as they lengthen. This type of disorder should result in the chains breaking, at which point the H2O molecules may be arranged. The amount of water in the studied samples did not exceed 0.15 H2O molecules per formula unit. Apparently, the mechanism of incorporation of H2O molecules governs the absence of good-quality single crystals in nature and a lack of them in synthetic experiments: the more H2O content in the structure, the stronger the disorder will be. A description of the crystal structure indicates that the ideal structure of the Cu oxalate biomineral moolooite should not contain H2O molecules and should be described by the Cu(C2O4) formula. However, it was shown that natural and synthetic moolooite crystals contain a significant portion of "structural" water, which cannot be ignored. Considering the substantially variable amount of water, which can be incorporated into the crystal structure, the formula Cu(C2O4)·nH2O for moolooite is justified.

Differential Retention of Pfam Domains Contributes to Long-term Evolutionary Trends.

Protein domains that emerged more recently in evolution have a higher structural disorder and greater clustering of hydrophobic residues along the primary sequence. It is hard to explain how selection acting via descent with modification could act so slowly as not to saturate over the extraordinarily long timescales over which these trends persist. Here, we hypothesize that the trends were created by a higher level of selection that differentially affects the retention probabilities of protein domains with different properties. This hypothesis predicts that loss rates should depend on disorder and clustering trait values. To test this, we inferred loss rates via maximum likelihood for animal Pfam domains, after first performing a set of stringent quality control methods to reduce annotation errors. Intermediate trait values, matching those of ancient domains, are associated with the lowest loss rates, making our results difficult to explain with reference to previously described homology detection biases. Simulations confirm that effect sizes are of the right magnitude to produce the observed long-term trends. Our results support the hypothesis that differential domain loss slowly weeds out those protein domains that have nonoptimal levels of disorder and clustering. The same preferences also shape the differential diversification of Pfam domains, thereby further impacting proteome composition.

Ferrimagnetic Ordering and Spin-Glass State in Diluted GdFeO3-Type Perovskites (Lu0.5Mn0.5)(Mn1-xTix)O3 with x = 0.25, 0.50, and 0.75.

ABO3 perovskite materials with small cations at the A site, especially those with ordered cation arrangements, have attracted a great deal of interest because they show unusual physical properties and deviations from the general characteristics of perovskites. In this work, perovskite solid solutions (Lu0.5Mn0.5)(Mn1-xTix)O3 with x = 0.25, 0.50, and 0.75 were synthesized by means of a high-pressure, high-temperature method at approximately 6 GPa and approximately 1550 K. All the samples crystallize in the GdFeO3-type perovskite structure (space group Pnma) and have random distributions of the small Lu3+ and Mn2+ cations at the A site and Mn4+/3+/2+ and Ti4+ cations at the B site, as determined by Rietveld analysis of high-quality synchrotron X-ray powder diffraction data. Lattice parameters are a = 5.4431 Å, b = 7.4358 Å, c = 5.1872 Å (for x = 0.25); a = 5.4872 Å, b = 7.4863 Å, c = 5.2027 Å (for x = 0.50); and a = 5.4772 Å, b = 7.6027 Å, c = 5.2340 Å (for x = 0.75). Despite a significant dilution of the A and B sublattices by non-magnetic Ti4+ cations, the x = 0.25 and 0.50 samples show long-range ferrimagnetic order below TC = 89 K and 36 K, respectively. Mn cations at both A and B sublattices are involved in the long-range magnetic order. The x = 0.75 sample shows a spin-glass transition at TSG = 6 K and a large frustration index of approximately 22. A temperature-independent dielectric constant was observed for x = 0.50 (approximately 32 between 5 and 150 K) and for x = 0.75 (approximately 50 between 5 and 250 K).

Intrinsic protein disorder uncouples affinity from binding specificity.

Intrinsically disordered proteins (IDPs) and intrinsically disordered regions (IDRs) of proteins often function by molecular recognition, in which they undergo induced folding. Based on prior generalizations, the idea prevails in the IDP field that due to the entropic penalty of induced folding, the major functional advantage associated with this binding mode is "uncoupling" specificity from binding strength. Nevertheless, both weaker binding and high specificity of IDPs/IDRs rest on limited experimental observations, making these assumptions more speculations than evidence-supported facts. The issue is also complicated by the rather vague concept of specificity that lacks an exact measure, such as the Kd for binding strength. We addressed these issues by creating and analyzing a comprehensive dataset of well-characterized ID/globular protein complexes, for which both the atomic structure of the complex and free energy (ΔG, Kd ) of interaction is known. Through this analysis, we provide evidence that the affinity distributions of IDP/globular and globular/globular complexes show different trends, whereas specificity does not connote to weaker binding strength of IDPs/IDRs. Furthermore, protein disorder extends the spectrum in the direction of very weak interactions, which may have important regulatory consequences and suggest that, in a biological sense, strict correlation of specificity and binding strength are uncoupled by structural disorder.

Hysteresis in Heat Capacity of MWCNTs Caused by Interface Behavior.

The paper is concerned with the study of structural disorder as well as the emergence and causes of heat capacity hysteresis in multiwall carbon nanotubes. The investigation methods are X-ray diffraction analysis, Raman spectroscopy, transmission electron microscopy, and calorimetric tests: thermogravimetric analysis, differential scanning calorimetry, and the thermal relaxation method for heat capacity hysteresis. Multiwall carbon nanotubes are shown to be composed of one or several types of zigzag-armchair domains. The domain structure of nanotube samples is responsible for the generation of uniaxial elastic microstrains and viscoelastic bending strains at domain interfaces. The thermomechanical behavior of interfaces is the chief cause of temperature hysteresis of heat capacity. The number of hystereses corresponds to the number of domain types in the structure, and values of hysteresis are determined by the crystallite size, thermal conductivity, and normal temperature distribution of strain. The found mechanism of heat capacity hysteresis can be helpful in preventing jumps in thermal properties and managing thermal memory in multiwall carbon nanotubes.

Modeling bismuth insertion in 1D hybrid lead halide TMSO(PbxBiy)I3pseudo-perovskites.

The structures of the disordered 1D (pseudo-)perovskites of general TMSO(PbxBiy)I3formulation [TMSO = (CH3)3SO+], obtained by doping the TMSOPbI3species with Bi3+ions, are investigated through the formulation of a statistical model of correlated disorder, which addresses the sequences of differently occupied BI6face-sharing octahedra (B = Pb, Bi or vacant site) within ideally infinite [(BI3)-]nchains. The x-ray diffraction patterns simulated on the basis of the model are matched to the experimental traces, which show many broad peaks with awkward (nearly trapezoidal) shapes, under the assumption that the charge balance is fully accomplished within each chain. The analysis allowed to establish a definite tendency of the metal species to cluster as pure Pb and Bi sequences. The application of the model is discussed critically, in particular as what concerns the possibility that further B-site neighbors beyond the second may influence the overall B-site occupancies.

Photonics probing of pup brain tissue and molecular-specific nuclear nanostructure alterations due to fetal alcoholism via light scattering/localization approaches.

SIGNIFICANCE: Light is a good probe for studying the nanoscale-level structural or molecular-specific structural properties of brain cells/tissue due to stress, alcohol, or any other abnormalities. Chronic alcoholism during pregnancy, i.e., fetal alcoholism, being teratogenic, results in fetal alcohol syndrome, and other neurological disorders. Understanding the nano-to-submicron scale spatial structural properties of pup brain cells/tissues using light/photonic probes could provide a plethora of information in understanding the effects of fetal alcoholism. AIM: Using both light scattering and light localization techniques to probe alterations in nano- to-submicron scale mass density or refractive index fluctuations in brain cells/tissues of mice pups, exposed to fetal alcoholism. APPROACH: We use the mesoscopic physics-based dual spectroscopic imaging techniques, partial wave spectroscopy (PWS) and molecular-specific inverse participation ratio (IPR) using confocal imaging, to quantify structural alterations in brain tissues and chromatin/histone in brain cells, respectively, in 60 days postnatal mice pup brain, exposed to fetal alcoholism. RESULTS: The finer focusing PWS analysis on tissues shows an increase in the degree of structural disorder strength in the pup brain tissues. Furthermore, results of the molecular-specific light localization IPR technique show an increase in the degree of spatial molecular mass density structural disorder in DNA and a decrease in the degree in histone. CONCLUSIONS: In particular, we characterize the spatial pup brain structures from the molecular to tissue levels and address the plausible reasons for such as mass density fluctuations in fetal alcoholism.

Tackling Disorder in γ-Ga2 O3.

Ga2 O3 and its polymorphs are attracting increasing attention. The rich structural space of polymorphic oxide systems such as Ga2 O3 offers potential for electronic structure engineering, which is of particular interest for a range of applications, such as power electronics. γ-Ga2 O3 presents a particular challenge across synthesis, characterization, and theory due to its inherent disorder and resulting complex structure-electronic-structure relationship. Here, density functional theory is used in combination with a machine-learning approach to screen nearly one million potential structures, thereby developing a robust atomistic model of the γ-phase. Theoretical results are compared with surface and bulk sensitive soft and hard X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, spectroscopic ellipsometry, and photoluminescence excitation spectroscopy experiments representative of the occupied and unoccupied states of γ-Ga2 O3 . The first onset of strong absorption at room temperature is found at 5.1 eV from spectroscopic ellipsometry, which agrees well with the excitation maximum at 5.17 eV obtained by photoluminescence excitation spectroscopy, where the latter shifts to 5.33 eV at 5 K. This work presents a leap forward in the treatment of complex, disordered oxides and is a crucial step toward exploring how their electronic structure can be understood in terms of local coordination and overall structure.

Structural dynamics of Zika virus NS1 via a reductionist approach reveal the disordered nature of its ß-roll domain in isolation.

Flavivirus Non-structural 1 (NS1) protein performs multiple functions and it is highly plausible that significant structural and folding dynamics of NS1 might play a role in its multifunctionality. It is important to understand the structural conformations of NS1 and its domains in isolation, possibly highlighting the implications on the overall NS1 protein dynamics. Therefore, we have employed extensively long molecular dynamic (MD) simulations in understanding the dynamics of the three structural domains (i.e., ß-roll, wing, and ß-ladder) in isolation, as a reductionist approach. We also found that the ß-ladder domain is highly flexible, while the ß-roll domain is disordered during long simulations. Further, we experimentally validated our findings using CD spectroscopy and confirmed the intrinsically disordered behavior of NS1 ß-roll in isolation and lipid mimetic environments. Therefore, we believe this study may have implications for significant dynamics played by NS1 protein, specifically during oligomerization of NS1.