Coexistence Of Domains Research Articles

Interactions Determining Stereoselectivity in Two-Dimensional Systems─The Case of 22-Hydroxycholesterol Epimers.

Oxidized derivatives of cholesterol play an important role in the functioning of biomembranes. Unlike other biomolecules, which are physiologically active in only one enantiomeric form, some oxysterols exist endogenously as two stereoisomers that exhibit strictly different biological effects. In this paper, we focused our attention on 22-hydroxycholesterol (22-OH) epimers, 22(R)-OH and 22(S)-OH, and examined their properties in Langmuir monolayers spread at the air/water interface, using classical surface manometry complemented with Brewster angle microscopy (BAM) images of the film texture. The studied epimers showed quite different monolayer characteristics. Namely, 22(S)-OH formed homogeneous, condensed monolayers of high collapse pressure, while 22(R)-OH films were more disordered and expanded with quite low collapse pressure. Interestingly, the latter compound showed in the course of the surface pressure-molecular area isotherm a temperature-dependent plateau transition, characterized by the coexistence of domains of molecules with different inclinations, visible in BAM images as patches of varying brightness. Molecular dynamics (MD) simulations confirmed this and revealed that the greater structural variability of 22(R)-OH is due to the greater hydration of the oxygen atom at C(22) compared to the other epimer. Next, we tested whether 22-OH epimers could differentiate interactions with sphingomyelin (SM). Although the strength of interaction with SM was similar for both epimers, the composition of the films corresponding to this minimum was different. With the aid of MD, it was found that these differences result directly from the interplay between 22-OH molecules and their ability for hydrogen bond formation. Therefore, the stereochemistry of oxysterols seems to play a crucial role in the overall structural organization of the membrane.

Exploring the feasibility of using fluidized bed homogeneous crystallization technology to recover sulfate ions from briny water as calcium sulfate pellets

The increasing salinity of water sources poses significant operational and environmental challenges, highlighting the importance of developing efficient methods for recovering [SO42−] ions from briny wastewater. In this study, the potential of fluidized bed homogeneous crystallization (FBHC) technology for recovering [SO42−] ions from briny water is explored. FBHC is an innovative technique that enhances scalability and separation efficiency by promoting the growth of crystalline particles in a fluidized state. To achieve maximum [SO42−] recovery and maintain stable fluidized bed conditions, a pH of 8 is recommended. A removal ratio (RR) of 71 % was recorded at a [SO42−] concentration of 0.14 M. Various [SO42−] concentrations exhibited a molar ratio (MR) of [Ca2+]/[SO42−] = 1.5. Smaller particles, which are more soluble and exhibit less nucleation, are typically formed under conditions with lower pH and [Ca2+] levels. Intermediate-sized particles are favored at neutral to slightly alkaline pH levels and near-stoichiometric [Ca2+]/[SO42−] MR. Greater calcium content and higher pH values promote the development and agglomeration of larger particles, with 50 % of the particles exceeding an average size of 0.38 mm. In the XPS study of CaSO4 crystals (gypsum), the Ca 2p1/2 and Ca 2p3/2 peaks are observed at binding energies of 351.5 eV and 347.7 eV, respectively. Gypsum is identifiable due to the presence of clear and distinct peaks in XRD patterns. SEM analysis reveals the coexistence of amorphous patches and tiny crystalline domains on the surface. These gypsum crystals resemble stacked needle-like structures accompanied by small, powdery crystals. In an acidic environment, the primary phase is CaSO4·2H2O, which generates well-formed, elongated, or tabular crystals that are characteristic of gypsum. The FBHC process, characterized by a high crystallization ratio (CR = 68 %) and the recovery of crystal pellets (>0.3 mm), significantly reduces sludge production compared to traditional chemical precipitation methods. Its cost-effectiveness and recoverability make FBHC a promising technology for the recovery of sulfate ions from briny wastewater.

Magnetic domain study in Fe3GaTe2 ferromagnet with strong perpendicular anisotropy using magnetic force microscopy

We investigate the magnetic domain behavior of bulk Fe3GaTe2, a van der Waals (vdW) ferromagnet characterized by a Curie temperature (Tc) of 350–380 K and significant perpendicular magnetic anisotropy (PMA). Using magnetic force microscopy, we present the evolution of magnetic domains during cooling from Tc to 300 K, and analyze magnetic domain images along the hysteresis loop at 4.2 K. Our observations reveal a strong temperature-dependent domain structure. From room temperature to Tc, we observe the coexistence of stripe, bubble, and surface spike domains. In contrast, in the zero-field cooled state at 4.2 K, irregular stripe and enclosed ring domains predominate. The correlation between global and local magnetization suggests that the hysteretic behavior in the magnetization results from the rapid nucleation of a few stripe domains evolving into intricate dendritic patterns, a phenomenon not previously observed in other vdW systems. These findings highlight the delicate balance among interlayer exchange coupling, thermal fluctuations, and PMA in the formation of various domains in a 3D vdW system, where shape anisotropy is minimized.

Asymmetric Manipulation of Perpendicular Exchange Bias and Programmable Spin Logical Cells by Spin-Orbit Torque in a Ferromagnet/Antiferromagnet System.

Antiferromagnets are competitive candidates for the next generation of spintronic devices owing to their superiority in small-scale and low-power-consumption devices. The electrical manipulation of the magnetization and exchange bias (EB) driven by spin-orbit torque (SOT) in ferromagnetic (FM)/antiferromagnetic (AFM) systems has become focused in spintronics. Here, the realization of a large perpendicular EB field in Co/IrMn and the effective manipulation of the magnetic moments of the magnetic Co layer and EB field by SOT in Pt/Co/IrMn system is reported. During the SOT-driven switching process, an asymmetrically manipulated state is observed. Current pulses with the same amplitude but opposite directions induce different magnetization states. Magneto-optical Kerr measurements reveal that this is due to the coexistence of stable and metastable antiferromagnetic domains in the AFM. Exploiting the asymmetric properties of these FM/AFM structures, five spin logic gates, namely AND, OR, NOR, NAND, and NOT, are realized in a single cell via SOT. This study provides an insight into the special ability of SOT on AFMs and also paves an avenue to construct the logic-in-memory and neuromorphic computing cells based on the AFM spintronic system.

Coexistence of multi-scale domains in ferroelectric polycrystals with non-uniform grain-size distributions

Coexistence of multi-scale domains in ferroelectric polycrystals with non-uniform grain-size distributions

Mechanical characterization of freestanding lipid bilayers with temperature-controlled phase.

Coexistence of lipid domains in cell membranes is associated with vital biological processes. Here, we investigate two such membranes: a multi-component membrane composed of DOPC and DPPC lipids with gel and fluid separated domains, and a single component membrane composed of PMPC lipids forming ripples. We characterize their mechanical properties below their melting point, where ordered and disordered regions coexist, and above their melting point, where they are in fluid phase. To conduct these inquiries, we create lipid bilayers in a microfluidic chip interfaced with a heating system and optical tweezers. The chip features a bubble trap and enables high-throughput formation of planar bilayers. Optical tweezers experiments reveal interfacial hydrodynamics (fluid-slip) and elastic properties (membrane tension and bending rigidity) at various temperatures. For PMPC bilayers, we demonstrate a higher fluid slip at the interface in the fluid-phase compared to the ripple phase, while for the DOPC:DPPC mixture, similar fluid slip is measured below and above the transition point. Membrane tension for both compositions increases after thermal fluidization. Bending rigidity is also measured using the forces required to extend a lipid nanotube pushed out of the freestanding membranes. This novel temperature-controlled microfluidic platform opens numerous possibilities for thermomechanical studies on freestanding planar membranes.

Association between oral health and cognitive frailty in community‐dwelling older adults

AbstractBackgroundCognitive frailty indicates the presence of both physical frailty and mild cognitive impairment (MCI) and has been associated with an increased risk of adverse health outcomes (e.g., mortality). Poor oral health has been related to cognitive impairment and physical frailty, respectively. However, the association between oral health and cognitive frailty remains unclear. This study aimed to explore the association between oral health and cognitive frailty in community‐dwelling older adults.MethodThis 10‐year cohort study (2011‐2021) is a part of an ongoing prospective cohort study. At baseline (2011‐2013), 605 non‐demented community‐dwelling older adults (aged 65+) with four biennial follow‐ups. Cognitive frailty was defined as the coexistence of MCI and physical frailty. Extended definitions of cognitive frailty were also assessed and defined as the coexistence of impaired cognitive domains and physical frailty. Oral health variables included tooth defects, dentition, and periodontal status. The generalized linear mixed model was used to explore the longitudinal association between oral health and cognitive frailty, adjusting for age, sex, lifestyle, comorbidity, and so on.ResultThe mean age of the study participants was 72.7 at baseline, and 53.4% were female. We found that tooth defect was associated with worsening of impaired memory‐frailty [adjusted odds ratio (aOR) = 1.13; 95% confidence interval (CI) = 1.03‐1.24] and impaired verbal fluency‐frailty (aOR = 1.07; 95% CI = 1.00‐1.11) over time; Dentition was associated with worsening of impaired executive function‐frailty (aOR = 1.10; 95% CI = 1.02‐1.18) over time; Periodontal status was associated with worsening of impaired memory‐frailty (aOR = 1.07; 95% CI = 1.02‐1.13) and verbal fluency‐frailty (aOR = 1.05; 95% CI = 1.00‐1.11) over time. No significant associations were found for traditional cognitive frailty and impaired attention‐frailty.ConclusionCognitive frailty is associated with oral health after adjusting for covariates. Inspection of oral health is helpful to predict the risk of cognitive impairment at an early stage. Further research on this topic is warranted to validate our findings.

Ba2+/Sr2+ regulation in A‐site vacancy‐engineered B0.015+1.5xS0.245‐1.5x□0.03BNT relaxor ceramics for energy storage

AbstractA‐site vacancy‐engineered Ba0.015+1.5xSr0.245‐1.5x□0.03Bi0.385Na0.325TiO3 (B0.015+1.5xS0.245‐1.5x□0.03BNT, x = 0, 0.012, 0.024, 0.036, 0.048, 0.06) ceramics were fabricated by a solid‐state reaction method. The effect of Ba/Sr regulation on the structure, polarization, and dielectric energy storage properties of the B0.015+1.5xS0.245‐1.5x□0.03BNT ceramics were investigated. With the increase of the x value, the lamellar microdomains transform into the coexistence of banded domains and nanodomains. A double‐like P‐E hysteresis loop with a high polarization value (Pmax > 35 μC/cm2) can be obtained at a very low electric field of 60 kV/cm. Consequently, a large recoverable energy storage density (Wrec = 2.33 J/cm3) can be achieved at a relatively low applied electric field of 130 kV/cm. The designed B0.087S0.173□0.03BNT also exhibits high dielectric constant (εr = 3510 @150°C&1 kHz) with suitable temperature capacitance coefficient (TCC150°C = ±15%) over the temperature range of 17°C∼382°C. These findings provide a novel vacancy‐engineered avenue towards the design of BSBNT relaxor ceramics with high Wrec and good stability for low‐voltage driven high‐temperature pulsed power capacitor.

Thermodynamic and structural properties of lipid-photosensitizer conjugates mixed with phospholipids: Impact on the formation and stability of nano-assemblies

The photosensitizer Phenalenone (PN) was grafted with one or two lipid (C18) chains to form pure nano-assemblies or mixed lipid vesicles suitable for photodynamic therapy. Mixtures of PN-C18 conjugates with stearoyl-oleoyl phosphatidylcholine (SOPC) form vesicles that disintegrate into bilayer sheets as the concentration of PN-C18 conjugates increases. We hypothesized that PN-C18 conjugates control the thermodynamic and structural properties of the mixtures and induce the disintegration of vesicles due to PN π-π-interactions.Monolayers were analyzed by surface pressure and grazing incidence X-ray diffraction (GIXD) measurements, and vesicles by differential scanning calorimetry and cryo-TEM. The results showed that PN-triazole-C18 (1A) and PN-NH-C18 (1B) segregate from the phospholipid domains. PN-(C18)2 (conjugate 2) develops favorable interactions with SOPC and distearoyl-phosphatidylcholine (DSPC). GIXD demonstrates the contribution of SOPC to the structuring of conjugate 2 and the role of the major component in controlling the structural properties of DSPC-conjugate 2 mixtures. Above 10 mol% conjugate 2 in SOPC vesicles, the coexistence of domains with different molecule packing leads to conjugate segregation, vesicle deformation, and the formation of small bilayer discs stabilized by the inter-bilayer π-π stacking of PN molecules.

Source-Free Progressive Graph Learning for Open-Set Domain Adaptation.

Open-set domain adaptation (OSDA) aims to transfer knowledge from a label-rich source domain to a label-scarce target domain while addressing disturbances from irrelevant target classes not present in the source data. However, most OSDA approaches are limited due to the lack of essential theoretical analysis of generalization bound, reliance on the coexistence of source and target data during adaptation, and failure to accurately estimate model predictions' uncertainty. To address these limitations, the Progressive Graph Learning (PGL) framework is proposed. PGL decomposes the target hypothesis space into shared and unknown subspaces and progressively pseudo-labels the most confident known samples from the target domain for hypothesis adaptation. PGL guarantees a tight upper bound of the target error by integrating a graph neural network with episodic training and leveraging adversarial learning to close the gap between the source and target distributions. The proposed approach also tackles a more realistic source-free open-set domain adaptation (SF-OSDA) setting that makes no assumptions about the coexistence of source and target domains. In a two-stage framework, the SF-PGL model' uniformly selects the most confident target instances from each category at a fixed ratio, and the confidence thresholds in each class weigh the classification loss in the adaptation step. The proposed methods are evaluated on benchmark image classification and action recognition datasets, where they demonstrate superiority and flexibility in recognizing both shared and unknown categories. Additionally, balanced pseudo-labeling plays a significant role in improving calibration, making the trained model less prone to over- or under-confident predictions on the target data.

Pure Chiral Polar Vortex Phase in PbTiO3/SrTiO3 Superlattices with Tunable Circular Dichroism.

Nontrivial polarization textures have been demonstrated in ferroelectric/dielectric superlattices, where the electrostatic, elastic, and different gradient energies compete in a delicate balance. When PbTiO3/SrTiO3 superlattices are grown on DyScO3, the coexistence of ferroelectric domains and vortex structure is observed for n = 12-20 unit cells. Here, we report an approach to achieve single-phase vortex structures in superlattices by controlling the epitaxial strain using Sr1.04Al0.12Ga0.35Ta0.50O3 substrates. The domain width follows Kittel's law with the thickness of the ferroelectric PbTiO3 layers. A phase transition from vortex to a disordered phase with temperature is characterized by the correlation length. Resonant soft X-ray diffraction circular dichroism at the titanium L-edge reveals enhanced chirality with the thickness of the ferroelectric layer. These results are supported by second-principles simulations, which demonstrate that the integrated helicity increases with n. The stabilization of chiral single-phase polar vortices in ferroelectric/dielectric superlattices can enable novel optoelectronic devices with enhanced ferroelectric-light interaction.

DNA Sensing Platforms: Novel Insights into Molecular Grafting Using Low Perturbative AFM Imaging.

By using AFM as a nanografting tool, we grafted micrometer-sized DNA platforms into inert alkanethiol SAMs. Tuning the grafting conditions (surface density of grafting lines and scan rate) allowed us to tailor the molecular density of the DNA platforms. Following the nanografting process, AFM was operated in the low perturbative Quantitative Imaging (QI) mode. The analysis of QI AFM images showed the coexistence of molecular domains of different heights, and thus different densities, within the grafted areas, which were not previously reported using contact AFM imaging. Thinner domains corresponded to low-density DNA regions characterized by loosely packed, randomly oriented DNA strands, while thicker domains corresponded to regions with more densely grafted DNA. Grafting with densely spaced and slow scans increased the size of the high-density domains, resulting in an overall increase in patch height. The structure of the grafted DNA was compared to self-assembled DNA, which was assessed through nanoshaving experiments. Exposing the DNA patches to the target sequence produced an increase in the patch height, indicating that hybridization was accomplished. The relative height increase of the DNA patches upon hybridization was higher in the case of lower density patches due to hybridization leading to a larger molecular reorganization. Low density DNA patches were therefore the most suitable for targeting oligonucleotide sequences.

Ruddlesden–Popper Perovskite Alloys: Continuous and Discontinuous Tuning of the Electronic Structure

Alloying mixed ratios of elements into the halide perovskite (HP) structure has proven to be an effective method of tuning these materials’ structural and electronic properties for photovoltaic and other optoelectronic applications. However, the standard spectroscopies used to characterize HP alloys such as absorption and photoluminescence are limited in their ability to detect disorder and phase segregation within the structure. Here, we characterize these properties in 2D HP alloys to a greater degree by using electroabsorption spectroscopy to study thin films with mixed-metal (Pb–Sn) and mixed-halide (Br–Cl and Br–I) compositions. The large spectral separation of band-edge states in 2D HPs allow us to detect a coexistence of elemental-rich domains within the Pb–Sn and Br–I alloys. Meanwhile, we find that the Br–Cl alloys exhibit sharper spectral features and a more uniform electroabsorption response indicative of an ordered structure, albeit still not as ordered as their pure Br and Cl counterparts. The band gap energies of the Br–Cl series (PEA2PbBrxCl4 – x) can be continuously tuned between 3.425 and 4.13 eV via the Br:Cl ratio, while the exciton binding energies can be tuned from 349 to 487 meV.

Phase Transition and Phase Separation in Realistic Thylakoid Lipid Membrane of Marine Algae in All-Atom Simulations.

Thylakoid membranes are specialized membranes predominantly composed of uncommon galacto- and sulfolipids, having distinct roles in photosynthesis. Large acyl chain variety and richness in polyunsaturated fatty acid (PUFA) content of thylakoid lipids further add to the compositional complexity. The function of these membrane systems is intimately dependent on the fluidity of its lipid matrix, which is strongly modulated by the lipid composition and temperature. The present work, employing extensive atomistic simulations, provides the first atomistic view of the phase transition and domain coexistence in a model membrane composed of thylakoid lipids of a commercially important red alga Gracilaria corticata between 10 and 40 °C. The growth and photosynthetic activity of marine algae are greatly influenced by the seawater temperature. So far, little is known about the molecular organization of lipids in thylakoid membranes, in particular their adaptive arrangements under temperature stress. Our simulations show that the algal thylakoid membrane undergoes a transition from a gel-like phase at a low temperature, 10-15 °C, to a homogeneous liquid-crystalline phase at a high temperature, 40 °C. Clear evidence of spontaneous phase separation into coexisting nanoscale domains is detected at intermediate temperatures nearing the optimal growth temperature range. Particularly, at 25-30 °C, we identified the formation of a stable ripple phase, where the gel-like domains rich in saturated and nearly hexagonally packed lipids were separated from fluid-like domains enriched in lipids containing PUFA chains. The phase separation is driven by the spontaneous and preferential segregation of lipids into differentially ordered domains, mainly depending on the acyl chain types. Cholesterol impairs the phase transition and the emergence of domains and induces a fairly uniform liquid-ordered phase in the membrane over the temperatures studied. This work improves the understanding of the properties and reorganization of lipids in the thylakoid membrane in response to temperature variation.

Effect of gravity on phase transition for liquid–gas simulations

Direct simulations of phase-change and phase-ordering phenomena are becoming more common. Recently, qualitative simulations of boiling phenomena have been undertaken by a large number of research groups. One seldom discussed limitation is that large values of gravitational forcing are required to simulate the detachment and rise of bubbles formed at the bottom surface. The forces are typically so large that neglecting the effects of varying pressure in the system becomes questionable. In this paper, we examine the effect of large pressure variations induced by gravity using pseudopotential lattice Boltzmann simulations. These pressure variations lead to height dependent conditions for phase coexistence and nucleation of either gas or liquid domains. Because these effects have not previously been studied in the context of these simulation methods, we focus here on the phase stability in a one-dimensional system, rather than the additional complexity of bubble or droplet dynamics. Even in this simple case, we find that the different forms of gravitational forces employed in the literature lead to qualitatively different phenomena, leading to the conclusion that the effects of gravity induced pressure variations on phase-change phenomena should be very carefully considered when trying to advance boiling and cavitation as well as liquefaction simulations to become quantitative tools.

Serinc5 Restricts HIV Membrane Fusion by Altering Lipid Order and Heterogeneity in the Viral Membrane.

The host restriction factor, Serinc5, incorporates into budding HIV particles and inhibits their infection by an incompletely understood mechanism. We have previously reported that Serinc5 but not its paralogue, Serinc2, blocks HIV cell entry by membrane fusion, specifically by inhibiting fusion pore formation and dilation. A body of work suggests that Serinc5 may alter the conformation and clustering of the HIV fusion protein, Env. To contribute an additional perspective to the developing model of Serinc5 restriction, we assessed Serinc2 and Serinc5's effects on HIV pseudoviral membranes. By measuring pseudoviral membrane thickness via cryo-electron microscopy and order via the fluorescent dye, FLIPPER-TR, Serinc5 was found to increase membrane heterogeneity, skewing the distribution toward a larger fraction of the viral membrane in an ordered phase. We also directly observed for the first time the coexistence of membrane domains within individual viral membrane envelopes. Using a total internal reflection fluorescence-based single particle fusion assay, we found that treatment of HIV pseudoviral particles with phosphatidylethanolamine (PE) rescued HIV pseudovirus fusion from restriction by Serinc5, which was accompanied by decreased membrane heterogeneity and order. This effect was specific for PE and did not depend on acyl chain length or saturation. Together, these data suggest that Serinc5 alters multiple interrelated properties of the viral membrane─lipid chain order, rigidity, line tension, and lateral pressure─which decrease the accessibility of fusion intermediates and disfavor completion of fusion. These biophysical insights into Serinc5 restriction of HIV infectivity could contribute to the development of novel antivirals that exploit the same weaknesses.

Stacking domain morphology in epitaxial graphene on silicon carbide

Terrace-sized, single-orientation graphene can be grown on top of a carbon buffer layer on silicon carbide by thermal decomposition. Despite its homogeneous appearance, a surprisingly large variation in electron transport properties is observed. Here, we employ Aberration-Corrected Low-Energy Electron Microscopy (AC-LEEM) to study a possible cause of this variability. We characterize the morphology of stacking domains between the graphene and the buffer layer of high-quality samples. Similar to the case of twisted bilayer graphene, the lattice mismatch between the graphene layer and the buffer layer at the growth temperature causes a moir\'e pattern with domain boundaries between AB and BA stackings. We analyze this moir\'e pattern to characterize the relative strain and to count the number of edge dislocations. Furthermore, we show that epitaxial graphene on silicon carbide is close to a phase transition, causing intrinsic disorder in the form of co-existence of anisotropic stripe domains and isotropic trigonal domains. Using adaptive geometric phase analysis, we determine the precise relative strain variation caused by these domains. We observe that the step edges of the SiC substrate influence the orientation of the domains and we discuss which aspects of the growth process influence these effects by comparing samples from different sources.

Control of excited state charge transfer dynamics of DMABN in deep eutectic solvent: Involvement of the partially twisted intermediate state

The photo-driven charge transfer process of 4-(dimethylamino) benzonitrile (DMABN) in deep eutectic solvent (DES) is investigated through steady state and time resolved spectroscopy along with non-adiabatic molecular dynamic simulations. Simultaneous coexistence of polar and non-polar domains in the DES manifests itself in different optical response and charge transfer dynamics of DMABN. The weaker correlation between solvent viscosity and observed reaction dynamics reveals the inadequacy of global macroscopic variables to rationalise the process at the microscopic level. On the other hand, ab initio computational results clearly show the presence of a distribution of partially twisted conformations, that helps to rationalise the experimental observations.

Light-Controlled Lyotropic Liquid Crystallinity of Polyaspartates Exploited as Photo-Switchable Alignment Medium

Two polyaspartates bearing ortho-fluorinated azobenzenes (pFAB) as photo-responsive groups in the side chain were synthesized: PpFABLA (1) and co-polyaspartate PpFABLA-co-PBLA [11, 75%(n/n) PpFABLA content]. As a consequence of the E/Z-isomerization of the side chain, PpFABLA (1) undergoes a visible-light-induced reversible coil-helix transition in solution: Green light (525 nm) affords the coil, and violet light (400 nm) affords the helix. pFAB significantly increases the thermal stability of the Z-isomer at 20 °C (t1/2 = 66 d for the Z-isomer) and effectively counters the favored back formation of the helix. At 20%(w/w) polymer concentration, the helical polymer forms a lyotropic liquid crystal (LLC) that further orients unidirectionally inside a magnetic field, while the coil polymer results in an isotropic solution. The high viscosity of the polymer solution stabilizes the coexistence of liquid crystalline and isotropic domains, which were obtained with spatial control by partial light irradiation. When used as an alignment medium, PpFABLA (1) enables (i) the measurement of dipolar couplings without the need for a separate isotropic reference and (ii) the differentiation of enantiomers. PpFABLA-co-PBLA (11) preserves the helical structure, by intention, independently of the E/Z-isomerization of the side chain: Both photo-isomers of PpFABLA-co-PBLA (11) form a helix that─at a concentration of 16%(w/w)─form an LLC. Despite the absence of a change in the secondary structure, the E/Z-isomerization of the side chain changes the morphology of the liquid crystal and leads to different sets of dipolar coupling for the same probe molecule.

Sol-gel based synthesis to explore structure, magnetic and optical properties of double perovskite Y2FeCrO6 nanoparticles

In this present investigation, nanoparticles of B-site disordered Y2FeCrO6 (YFCO) double perovskite have been successfully synthesized for the first time by optimizing synthesis steps and temperatures of facile sol-gel technique to investigate their structural, magnetic, and optical properties. The Rietveld refinement of the X-ray diffraction pattern of YFCO nanoparticles revealed a single-phase orthorhombic structure with pbnm space group. The average size of the nanoparticles is around 67±15 nm determined by both field emission scanning electron microscopy and transmission electron microscopy imaging. The existence of mixed valence states of Fe and Cr ions was confirmed by X-ray photoelectron spectroscopy which is an indication of the absence of proper B site long range ordering. The temperature dependent magnetization curves demonstrated negative magnetization of this double perovskite material with compensation temperature at around 170 K. The field-dependent magnetic hysteresis loops exhibited the coexistence of weak ferromagnetic and antiferromagnetic domains in YFCO nanoparticles. The exchange bias effect was observed below Néel temperature which is tunable by a cooling magnetic field. The UV–visible spectroscopy ensured that YFCO nanoparticles have a direct band gap of ∼ 1.90 eV, which was further confirmed by steady-state photoluminescence spectroscopy. This B-site disordered YFCO might enhance interest on basic fundamental research on disordered rare-earth and transition metal-based perovskite systems and can be used for spintronics as well as photocatalytic applications because of its favorable magnetic and optical properties.