Structure-property Correlations Research Articles

Evolution of structural dynamics in cesium lead halide perovskite colloidal nanocrystals from temperature-controlled synthesis.

Halide perovskite nanocrystals are at the forefront of materials research due to their remarkable optoelectronic properties and versatile applications. While their lattice structure and optical properties have been extensively investigated for the structure-property correlation, their lattice dynamics, the physical link between the lattice structure and optoelectronic properties, has been much less visited. We report the evolution of structural dynamics of a series of cesium lead halide perovskite nanocrystals whose size and morphology are systematically varied by synthesis temperature. Low-frequency Raman spectroscopy uncovers the nanocrystals' structural dynamics, including a relaxational spectral continuum from ligand librations and a phonon spectrum evolving with nanocrystal size. As the size of nanocrystals increases, their phonon spectrum becomes more intense, and their spectral weights redistribute with new first- and second-order modes being activated. The linewidth of the observed phonon modes generally broadens as the nanocrystal grows larger, an interesting deviation from the established phonon confinement model. We suggest that strong confinement and truncation of the lattice and ligands anchoring on the surface might lead to pinning of the lattice dynamics at nanoscale. These findings offer new insights into the bulk-nano-transition in halide perovskite soft semiconductors.

Stabilization of halide perovskites with silicon compounds for optoelectronic, catalytic, and bioimaging applications

AbstractSilicon belongs to group 14 elements along with carbon, germanium, tin, and lead in the periodic table. Similar to carbon, silicon is capable of forming a wide range of stable compounds, including silicon hydrides, organosilicons, silicic acids, silicon oxides, and silicone polymers. These materials have been used extensively in optoelectronic devices, sensing, catalysis, and biomedical applications. In recent years, silicon compounds have also been shown to be suitable for stabilizing delicate halide perovskite structures. These composite materials are now receiving a lot of interest for their potential use in various real‐world applications. Despite exhibiting outstanding performance in various optoelectronic devices, halide perovskites are susceptible to breakdown in the presence of moisture, oxygen, heat, and UV light. Silicon compounds are thought to be excellent materials for improving both halide perovskite stability and the performance of perovskite‐based optoelectronic devices. In this work, a wide range of silicon compounds that have been used in halide perovskite research and their applications in various fields are discussed. The interfacial stability, structure–property correlations, and various application aspects of perovskite and silicon compounds are also analyzed at the molecular level. This study also explores the developments, difficulties, and potential future directions associated with the synthesis and application of perovskite‐silicon compounds.image

Precise Modulation of CO2 Sorption in Ti8Ce2-Oxo Clusters: Elucidating Lewis Acidity of the Ce Metal Sites and Structural Flexibility.

Investigating the structure-property correlation in porous materials is a fundamental and consistent focus in various scientific domains, especially within sorption research. Metal oxide clusters with capping ligands, characterized by intrinsic cavities formed through specific solid-state packing, demonstrate significant potential as versatile platforms for sorption investigations due to their precisely tunable atomic structures and inherent long-range order. This study presents a series of Ti8Ce2-oxo clusters with subtle variations in coordinated linkers and explores their sorption behavior. Notably, Ti8Ce2-BA (BA denotes benzoic acid) manifests a distinctive two-step profile during the CO2 adsorption, accompanied by a hysteresis loop. This observation marks a new instance within the metal oxide cluster field. Of intrigue, the presence of unsaturated Ce(IV) sites was found to be correlated with the stepped sorption property. Moreover, the introduction of an electrophilic fluorine atom, positioned ortho or para to the benzoic acid, facilitated precise control over gate pressure and stepped sorption quantities. Advanced in situ techniques systematically unraveled the underlying mechanism behind this unique sorption behavior. The findings elucidate that robust Lewis base-acid interactions are established between the CO2 molecules and Ce ions, consequently altering the conformation of coordinated linkers. Conversely, the F atoms primarily contribute to gate pressure variation by influencing the Lewis acidity of the Ce sites. This research advances the understanding in fabricating metal-oxo clusters with structural flexibility and provides profound insights into their host-guest interaction motifs. These insights hold substantial promise across diverse fields and offer valuable guidance for future adsorbent designs grounded in fundamental theories of structure-property relationships.

Structural, Optical, and Mechanical Insights into Cellulose Nanocrystal Chiral Nematic Film Engineering by Two Assembly Techniques.

Iridescent cellulose nanocrystal (CNC) films with chiral nematic nanostructures exhibit great potential in optical devices, sensors, painting, and anticounterfeiting applications. CNCs can assemble into a chiral nematic liquid crystal structure by evaporation-assisted self-assembly (EISA) and vacuum-assisted self-assembly (VASA) techniques. However, there is a lack of comprehensive examinations of their structure-property correlations, which are essential for fabricating materials with unique properties. In this work, we gained insights into the optical, mechanical, and structural differences of CNC films engineered using the two techniques. In contrast to the random self-assembly at the liquid-air interface in EISA, the continuous external pressure in the VASA process forces CNCs to assemble at the filter-liquid interface. This results in fewer defects in the interfaces between tactoids and highly ordered cholesteric phases. Owing to the distinct CNC assembly behaviors, the films prepared by these two methods show great differences in the nanostructure, microstructure, and macroscopic morphology. Consequently, the highly ordered cholesteric structure gives VASA-CNC films a more uniform structural color and enhanced mechanical performance. These fundamental understandings of the relationship of structure-property nanoengineering through various assembly techniques are essential for designing and constructing high-performance chiral iridescent CNC materials.

From Bulk to Interface: Solvent Exchange Dynamics and Their Role in Ion Transport and the Interfacial Model of Rechargeable Magnesium Batteries.

Multivalent battery chemistries have been explored in response to the increasing demand for high-energy rechargeable batteries utilizing sustainable resources. Solvation structures of working cations have been recognized as a key component in the design of electrolytes; however, most structure-property correlations of metal ions in organic electrolytes usually build upon favorable static solvation structures, often overlooking solvent exchange dynamics. We here report the ion solvation structures and solvent exchange rates of magnesium electrolytes in various solvents by using multimodal nuclear magnetic resonance (NMR) analysis and molecular dynamics/density functional theory (MD/DFT) calculations. These magnesium solvation structures and solvent exchange dynamics are correlated to the combined effects of several physicochemical properties of the solvents. Moreover, Mg2+ transport and interfacial charge transfer efficiency are found to be closely correlated to the solvent exchange rate in the binary electrolytes where the solvent exchange is tunable by the fraction of diluent solvents. Our primary findings are (1) most battery-related solvents undergo ultraslow solvent exchange coordinating to Mg2+ (with time scales ranging from 0.5 μs to 5 ms), (2) the cation transport mechanism is a mixture of vehicular and structural diffusion even at the ultraslow exchange limit (with faster solvent exchange leading to faster cation transport), and (3) an interfacial model wherein organic-rich regions facilitate desolvation and inorganic regions promote Mg2+ transport is consistent with our NMR, electrochemistry, and cryogenic X-ray photoelectron spectroscopy (cryo-XPS) results. This observed ultraslow solvent exchange and its importance for ion transport and interfacial properties necessitate the judicious selection of solvents and informed design of electrolyte blends for multivalent electrolytes.

Synergistic effect of the ferroelectric-ferrite approach on the structural, electrical and magnetic properties

ABSTRACT In the present report, the structure–property correlation of 0.9BaZr0.2Ti0.8O3-0.1NiFe2O4 (0.9BZT-0.1NFO) composite is studied. The X-ray Diffraction, Raman spectroscopy and Field Effect Scanning Electron Microscopy (FESEM) reveal the existence of ferroelectric and magnetic phases without any impurity and interdiffusion. The dielectric, ferroelectric and conductivity mechanisms of the sample are studied in a wide range of temperature (RT-500°C) and frequency (100 Hz–1 MHz), respectively. The dielectric constant is larger than 2000 in low frequency (<1 kHz), while it decreases to 500 when the frequency is larger than 4 kHz. Both small polaron and correlated barrier hopping contribute to the conduction mechanism. The multiferroism at room temperature is confirmed by P-E and M-H loop study. The composite obeys the Law of Approach to Saturation at a higher field. The saturation magnetization found from fitting is in good agreement with the experimental value.

Health is the greatest wealth: Quest for a diagnostic check for thermochemistry of pure drug compounds

The development of pharmaceutical formulations and the optimisation of drug synthesis are not possible without knowledge of thermodynamics. At the same time, the quantity and quality of the available data is not at a level that meets modern requirements. A convenient diagnostic approach is desirable to assess the quality of available experimental thermodynamic data of drugs. A comprehensive set of available data on phase transitions of profens family drugs was analysed using new complementary measurements and structure–property correlations. The consistent sets of solid–gas, liquid–gas and solid–liquid phase transitions were evaluated for twelve active pharmaceutical ingredients based on alkanoic acid derivatives and recommended for the calculations of the pharmaceutical processes. A “centerpiece approach” proposed in this work helped to perform the “health check” of the thermochemical data. The evaluated data on the sublimation enthalpies were used to derive the crystal lattice energies of the profens and to correlate the water solubilities with the sublimation vapour pressures and molecular parameters. A “paper-and-pen” approach proposed in this work can be extended to the diagnosis of “sick” or “healthy” thermodynamic data for drugs with a different structure than those studied in this work.

Ferroelectric and antiferroelectric chiral multilactate liquid crystalline materials with negative dielectric anisotropy

In this work, the mesomorphic, electro-optic and dielectric properties have been discussed in the light of molecular structure-property correlations of two chiral multilactate liquid crystalline materials possessing the orthogonal paraelectric Smectic A* phase, tilted ferroelectric Smectic C* phase and the tilted antiferroelectric Smectic CA* phase, over a substantially broad temperature range. Interestingly, a reasonably rare re-entrant Smectic C* phase (SmCre*) has also been identified in one of the investigated materials. These materials differ in their linkage groups (keto or ether) and an additional chiral unit in the terminal chain. The phase transition temperatures and transition enthalpies were determined from Polarizing Optical Microscopy and Differential Scanning Calorimetry (DSC) measurements. The compounds exhibit negative dielectric anisotropy (Δε) throughout the mesomorphic range (maximum −18 and −4 in SmA* for both the compounds) and moderately high values of spontaneous polarization (∼153 nC/cm2 in SmCre* phase). The temperature dependence of the response time (τ), bulk viscosity (η) and the activation energies (Ea) throughout the mesomorphic phase have been determined from the spontaneous polarization measurements. To emphasize the structure-property correlations in more detail, dielectric spectroscopy measurement has also been performed to measure the dielectric strength, dielectric loss, frequency dependent permittivities, relaxation time and relaxation frequencies. The clear evidence of the relatively rare SmCre* phase has also been confirmed from the temperature and frequency dependence of the dielectric permittivity. These results shed important light on the emergence of these materials as a smart alternative for their application in multicomponent mixtures targeted for advanced electro-optic and photonic devices.

Correlations of structural, thermal and electrical properties of sodium doped complex borophosphosilicate glass

Borophosphosilicate glasses with varying sodium ion concentrations were investigated for their, structural, thermal, and electrical properties. All the obtained glasses were transparent except the glass with the highest sodium content, which exhibited translucency due to inhomogeneities. Increasing sodium content led to reduced boron and silicon content while maintaining a constant B/Si ratio, indicating progressive depolymerization of the glass network. Confocal microscopy, scanning electron microscopy, and atomic force microscopy showed homogeneous and granular structure for samples with lower sodium content, but higher sodium content resulted in visible agglomeration/nanocrystallization. X-ray diffractograms showed amorphous nature for most samples, with samples doped with the highest concentrations of Na2O showing several broad reflections suggesting nanoscale crystallinity. Fourier-transform infrared spectroscopy revealed shifts in dominant bands with increasing sodium content, indicating depolymerization of the borate network. An observed decrease in glass transition temperature and thermal stability with increasing sodium content was attributed to depolymerization and formation of non-bridging oxygens. Impedance spectroscopy revealed two relaxation processes associated with the transport of Na+ ions through two different regions. DC conductivity and activation energy predominantly increased with the sodium ion content at high temperatures.

The effects of chain-length distributions on starch-related properties in waxy rices

Normal rice starch consists of amylopectin and amylose, whose relative amounts and chain-length distributions (CLDs) are major determinants of the digestibility and rheology of cooked rice, and are related to metabolic health and consumer preference. Here, the mechanism of how molecular structural features of pure amylopectin (waxy) starches affect starch properties was explored. Following debranching, chain-length distributions of seven waxy varieties were measured using size-exclusion chromatography, and parameterized using biosynthesis-based models, which involve breaking up the chain-length distribution into contributions from five enzyme sets covering overlapping ranges of chain length; structure-property correlations involving the fifth set were found to be statistically significant. Digestibility was measured in vitro, and parameters for the slower and longer digestion phase quantified using non-linear least-squares fitting. The coefficient for the significant correlation involving amylopectin fine structure for the fifth set was −0.903, while the amounts of amylopectin short and long chains were found to dominate breakdown viscosity (correlation coefficients 0.801 and − 0.911, respectively). This provides a methodology for finding or developing healthier starch in terms of lower digestion rate, while also having acceptable palatability. As rice breeders can to some extent control CLDs, this can help the development of waxy rices with improved properties.

Not fully twisted, not fully planar, but intermediate torsions for ideal chromophore design: A computational study on p‐phenylene bridged pyridinium phenolate betaines

AbstractThis contribution reports extensive studies on structure–property correlations of two isoelectronic betaine metamers (positional isomers). These zwitterions differ from each other with respect to bonding modes of pyridinium acceptors (Reichardt's mode: through N‐atom versus Brooker's mode: through C‐atom) with the p‐phenylene bridged phenolate donors. Various quantum chemical methodologies are used in this investigation, with time‐dependent (TD) and coupled perturbed (CPHF) theories for computations of many molecular response properties. Analysis of first hyperpolarizabilities (β) indicates that Reichardt's metamer (ωB97xD: β = 349.5 × 10−30 esu) is more efficient chromophore (~5‐fold enhanced) than Brooker's metamer (ωB97xD: β = 69.4 × 10−30 esu). The gyratory abilities of the bridge junctions resulted in a cohort of metastable conformations, in the rotational potential energy surfaces (PES) of the two metamers. Moreover, rotational PES establishes that intermediary torsions are suitable for optimal chromophore design strategies (Reichardt's metamer: β = 956.5 × 10−30 esu, and Brooker's metamer: β = 1104.7 × 10−30 esu), Thus suitable conformational manipulations, can be used to obtain more efficient zwitterionic molecular chromophores. Compared unbridged prototype molecules, p‐phenylene bridged zwitterions showed ~6–9 times enhanced values of β. In addition, important aspects of suitable chromophore design strategies are suggested.

Modified Donor End Caps for Binary-to-Ternary WORM Memory Conversion in N-Heteroaromatic Systems.

A series of novel D-π-A type organic small molecules have been designed, synthesized, and demonstrated for non-volatile resistive switching WORM memory application. The electron-deficient phenazine and quinoxaline units were coupled with various functionalized triphenylamine end caps to explore the structure-property correlations. The photophysical investigations displayed considerable intramolecular charge transfer, and the electrochemical analysis revealed an optimum band gap of 2.44 to 2.83 eV. These factors and the thin film morphological studies suggest the feasibility of the compounds as better resistive memory devices. All the compounds indicated potent non-volatile resistive switching memory capabilities with ON/OFF ratios ranging from 103 to 104, and the lowest threshold voltage recorded stands at -0.74 V. A longer retention time of 103 s marks the substantial stability of the devices. The phenazine-based compounds outperformed the others in terms of memory performance. Exceptionally, the compound with -CHO substituted triphenylamine exhibited ternary memory performance owing to its multiple traps. The resistive switching mechanism for the devices was validated using density functional theory calculations, which revealed that the integrated effect of charge transfer and charge trapping contributes significantly to the resistive switching phenomena.

Giant electrostriction in bulk RE (III) substituted CeO2: Effect of RE-[formula omitted] interaction and RE concentration

Recent discovery of giant electrostriction in bulk polycrystalline ceramics and thin films of rare earth (RE (III)) substituted ceria (CeO2) driven by electroactive defect complexes and their coordinated elastic response, expands the material spectrum for electrostrain applications beyond the conventional piezoelectric materials. Bulk ceramics provide an ideal platform to systematically study electrostriction as a function of parameters such as RE3+-defect (VO••) interaction and RE concentration. In this work, we perform structure-property correlation studies in bulk ceramics of RE3+ substituted ceria (RECO) with RE=Y, La and Gd, all of them having weak dopant-defect interaction, with Y- VO•• being attractive, La-VO•• being repulsive, and Gd-VO•• being neutral. We employ large signal measurements to measure the electrostrictive coefficients of all the RECO ceramics, with varying concentration of RE3+, and show that an attractive defect-dopant interaction with atleast 20% of substituent ion concentration yields both giant M and Q electrostrictive response.

Pre-yielding and necking process of double network hydrogels revealed by sample geometry effects

Understanding the yielding and necking mechanisms of double network (DN) materials is crucial for establishing structure-property correlations. While previous studies have primarily focused on how macro-yielding behavior changes with network structure and swelling, in this work, we study the local internal damage in the pre-yielding process to unveil the yielding and necking mechanisms for typical DN gels. Through birefringence retardation imaging during tensile deformation on DN gels of various sample geometries, our findings reveal the following key points: 1) Initiation and Growth of Damage Zones: Prior to macroscopic yielding, damage zones initiate from the sample edges and gradually grow towards the sample center with elongation. 2) Rapid Propagation and Yielding: Beyond a certain stress threshold, damage zones rapidly propagate under constant loading. Two damage zones eventually merge at the sample center, resulting in yielding. 3) Intrinsic Stress Determination: The stress at this point is intrinsic and determined by the structure of the two networks. 4) Pseudo Size-Dependency: Samples with insufficient width exhibit a pseudo size-dependency of yielding stress, as yielding occurs before reaching the critical stress. To explain the origin of intrinsic yielding stress, we introduce an intrinsic effective crack length (cI) as a measure of stress concentration around the internal crack tip of the damaged zone in the first network. Beyond this length, the influence on internal stress concentration around the damage zone is effectively screened by the load-bearing effect of the stretchable second network. The estimated cI, dependent on the microstructure of the two networks, was approximately 10 times the mesh size of the first network for typical DN gels.

Lithium Ion Intercalation-Induced Metal-Insulator Transition in Inclined-Standing Grown 2D Non-Layered Cr2S3 Nanosheets.

Gate-controlled ionic intercalation in the van der Waals gap of 2D layered materials can induce novel phases and unlock new properties. However, this strategy is often unsuitable for densely packed 2D non-layered materials. The non-layered rhombohedral Cr2S3 is an intrinsic heterodimensional superlattice with alternating layers of 2D CrS2 and 0D Cr1/3. Here an innovative chemical vapor deposition method is reported, utilizing strategically modified metal precursors to initiate entirely new seed layers, yields ultrathin inclined-standing grown 2D Cr2S3 nanosheets with edge instead of face contact with substrate surfaces, enabling rapid all-dry transfer to other substrates while ensuring high crystal quality. The unconventional ordered vacancy channels within the 0D Cr1/3 layers, as revealed by cross-sectional scanning transmission electron microscope, permitting the insertion of Li+ ions. An unprecedented metal-insulator transition, with a resistance modulation of up to six orders of magnitude at 300 K, is observed in Cr2S3-based ionic field-effect transistors. Theoretical calculations corroborate the metallization induced by Li-ion intercalation. This work sheds light on the understanding of growth mechanism, structure-property correlation and highlights the diverse potential applications of 2D non-layered Cr2S3 superlattice.

Determination of the individual block lengths of the block copolymers of Poly(trimethylene carbonate) by liquid chromatography at critical conditions

Amphiphilic block copolymers based on poly(trimethylene carbonate) (PTMC) have gained significant attention for biomedical applications owing to their unique degradation characteristics. Ring-opening polymerization (ROP) is the most widely employed method for polymerization of cyclic carbonates, especially for trimethylene carbonate (TMC). Herein, di- and tri-block copolymers of PTMC are synthesized by ROP of TMC using poly(ethylene glycol) monomethyl ether (MeO-PEG) or poly(ethylene glycol) (PEG) as a macro-initiator, respectively. The synthesized products are characterized by size-exclusion chromatography (SEC) and nuclear magnetic resonance spectroscopy (1H NMR) for their molar mass and chemical composition, respectively. However, these techniques are inconclusive about several pertinent aspects of the block copolymers, such as individual block length and unwanted homopolymer content. To address these limitations, liquid chromatography at critical conditions of both PEG and PTMC are employed. Chromatographic critical conditions for PTMC are reported for the first time in the current study. The analysis protocol successfully reveals the individual block lengths of both blocks of the block copolymers, along with the quantification of the unwanted homopolymers in the samples. The individual block lengths and the presence of homopolymers significantly affect the self-assembly capability and drug-loading capacity of amphiphilic block copolymers. Thus, the study divulges important information crucial for the development of structure-property correlations, which is essential for optimizing the performance of these block copolymers in biomedical applications.

Chiral Canoe-Like Pd0 or Pt0 Alloyed Copper Alkynyl Nanoclusters Display Near-Infrared Luminescence.

Alloying nanoclusters (NCs) has emerged as a widely explored and versatile strategy for tailoring tunable properties, facilitating in-depth atomic-level investigations of structure-property correlations. In this study, we have successfully synthesized six atomically precise copper NCs alloyed with Group 10 metals (Pd or Pt). Notably, the Pd0 or Pt0 atom situated at the center of the distorted hexagonal antiprism Pd0/Pt0@Cu12 cage, coordinated with twelve Cu+ and two tBuC≡C- ligands. Moreover, ligand exchange strategies demonstrated the potential for Cl- and Br- to replace one or two alkynyl ligands positioned at the top or side of the NCs. The chirality exhibited by these racemic NCs is primarily attributed to the involvement of halogens and a chiral (Pd/Pt)@Cu18 skeleton. Furthermore, all the NCs exhibit near-infrared (NIR) luminescence, characterized by emission peaks at 705-755 nm, lifetimes ranging from 6.630 to 9.662 μs, and absolute photoluminescence quantum yields (PLQYs) of 1.75 %-2.52 % in their crystalline state. The experimental optical properties of these NCs are found to be in excellent agreement with the results of theoretical calculations. These alloy NCs not only offer valuable insights into the synthesis of Pd0/Pt0-Cu alloy NCs, but also bridge the gap in understanding the structure-luminescence relationships of Pd0/Pt0-Cu molecules.

A Study of Structure–Property Correlation on Wet Spinning Conditions in Heat-Resistant Poly(m-phenylene isophthalamide) Hollow Fiber Membranes

A Study of Structure–Property Correlation on Wet Spinning Conditions in Heat-Resistant Poly(m-phenylene isophthalamide) Hollow Fiber Membranes

Interpretable structure-property correlation in X-ray diffraction patterns of HfZrO thin films via machine learning

The X-ray diffraction (XRD) patterns of materials contain important and rich information in terms of structure, strain state, grain size, etc. The XRD can become a powerful fingerprint for material characterizations when it is combined with machine learning techniques. Attempts utilizing machine-learning-based methods mainly focus on phase identification for mixture compounds. Herein, we applied a machine-learning-based method linking XRD patterns of HfZrO thin films directly to their electronic properties in experiments. In accordance with conventional understanding, the machine learning model suggests that non-monoclinic (NM) phases of HfO2 and ZrO2 are among the main contributors to higher relative permittivity and lower leakage current. Furthermore, some minor interfacial phases like TiO x and ZrN x are also proposed to be even more important contributors to our target electronic properties. Our research demonstrates that machine learning has the potential to reveal minor XRD signals from sub-1 nm interfacial layers that have long been considered undetectable and thus ignored by human interpretation.

Advanced tools for molecular characterization of bio-based and biodegradable polymers.

Bio-based and biodegradable materials play a vital role in a sustainable and green economy. These materials must exhibit properties that are similarto or better than the properties of oil- or coal-based materials and require sophisticated synthesis technologies and detailed knowledge of structure-property correlations. For comprehensive molecular structure elucidation, advanced analytical methods, including coupled and hyphenated techniques that combine advanced fractionation and information-rich spectroscopic detectors, are an indispensable tool. One important tool for fractionating complex polymers regarding molecular size is size exclusion chromatography. For fractionating polymers with regard to chemical composition, solvent (or temperature) gradient HPLC has been developed. The combination of different liquid chromatography methods in comprehensive two-dimensional HPLC setups is another important tool. Today, a toolbox of HPLC methods is in place that enables the fractionation of complex bio-based and biodegradable polymers according to the most important molecular parameters including molecular size, composition, functionality, and branching. Here, an overview of the different techniques and some major applications is presented. Some representative developments in the field are discussed, and different techniques, experimental protocols, and applications are highlighted.