Water Hydrogen-Bond Mediated Layer by Layer Alignment of Lipid Rafts as a Precursor of Intermembrane Processes.

Lipid rafts, which are dynamic nanodomains in the plasma membrane, play a crucial role in intermembrane processes by clustering together and growing in size within the plane of the membrane while also aligning with each other across different membranes. However, the physical origin of layer by layer alignment of lipid rafts remains to be elucidated. Here, by using fluorescence imaging and synchrotron X-ray reflectivity in a phase-separated multilayer system, we find that the alignment of raft-mimicking Lo domains is regulated by the distance between bilayers. Molecular dynamics simulations reveal that the aligned state is energetically preferred when the intermembrane distance is small due to its ability to minimize the volume of surface water, which has fewer water hydrogen bonds (HBs) compared to bulk water. Our results suggest that water HB-driven alignment of lipid rafts plays a role as a precursor of intermembrane processes such as cell-cell fusion, virus entry, and signaling.

Dual Chalcogen-Bonding Interaction for High-Performance Filterless Narrowband Organic Photodetectors.

A novel green-absorbing organic molecule featuring dual intramolecular chalcogen bonds is synthesized and characterized. This molecule incorporates two such bonds: one between a tellurium atom and the oxygen atom of a carbonyl moiety, and the other between the tellurium atom and the adjacent nitrogen atom within a pyridine moiety. The molecule, featuring dual intramolecular chalcogen bonds exhibits a narrow absorption spectrum and elevated absorption coefficients, closely aligned with a resonance parameter of approximately 0.5. This behavior is due to its cyanine-like characteristics and favorable electrical properties, which are a direct result of its rigid, planar molecular structure. Therefore, this organic molecule forming dual intramolecular chalcogen bonds achieves superior optoelectronic performance in green-selective photodetectors, boasting an external quantum efficiency of over 65% and a full-width at half maximum of less than 95 nm while maintaining the performance after 1000 h of heating aging at 85 °C. Such organic photodetectors are poised to enhance stacked organic photodetector-on-silicon hybrid image sensors, paving the way for the next-generation of high-resolution and high-sensitivity image sensors.

Multiple pathways of crystal nucleation in an extremely supersaturated aqueous potassium dihydrogen phosphate (KDP) solution droplet.

Solution studies have proposed that crystal nucleation can take more complex pathways than previously expected in classical nucleation theory, such as formation of prenucleation clusters or densified amorphous/liquid phases. These findings show that it is possible to separate fluctuations in the different order parameters governing crystal nucleation, that is, density and structure. However, a direct observation of the multipathways from aqueous solutions remains a great challenge because heterogeneous nucleation sites, such as container walls, can prevent these paths. Here, we demonstrate the existence of multiple pathways of nucleation in highly supersaturated aqueous KH2PO4 (KDP) solution using the combination of a containerless device (electrostatic levitation), and in situ micro-Raman and synchrotron X-ray scattering. Specifically, we find that, at an unprecedentedly deep level of supersaturation, a high-concentration KDP solution first transforms into a metastable crystal before reaching stability at room temperature. However, a low-concentration solution, with different local structures, directly transforms into the stable crystal phase. These apparent multiple pathways of crystallization depend on the degree of supersaturation.

ZnO:Ga-graded ITO electrodes to control interface between PCBM and ITO in planar perovskite solar cells.

Ga-doped ZnO (GZO)-graded layer, facilitating electron extraction from electron transport layer, was integrated on the surface of transparent indium tin oxide (ITO) cathode by using graded sputtering technique to improve the performance of planar n-i-p perovskite solar cells (PSCs). The thickness of graded GZO layer was controlled to optimize GZO-indium tin oxide (ITO) combined electrode for planar n-i-p PSCs. At optimized graded thickness of 15 nm, the GZO-ITO combined electrode showed an optical transmittance of 95%, a resistivity of 2.3 × 10-4 Ohm cm, a sheet resistance of 15.6 Ohm/square, and work function of 4.23 eV, which is well matched with the 4.0-eV lowest unoccupied molecular orbital of [6,6]-phenyl-C61-butyric acid methyl ester. Owing to enhanced extraction of electron by the graded GZO, the n-i-p PSC with GZO-ITO combined electrode showed higher power conversion efficiency (PCE) of 9.67% than the PCE (5.25%) of PSC with only ITO electrode without GZO-graded layer. In addition, the GZO integrated-ITO electrode acts as transparent electrode and electron extraction layer simultaneously due to graded mixing of the GZO at the surface region of ITO electrode.

Pressure-Induced Diels-Alder Reactions in C6 H6 -C6 F6 Cocrystal towards Graphane Structure.

Pressure-induced polymerization (PIP) of aromatics is a novel method for constructing sp3 -carbon frameworks, and nanothreads with diamond-like structures were synthesized by compressing benzene and its derivatives. Here by compressing a benzene-hexafluorobenzene cocrystal (CHCF), H-F-substituted graphane with a layered structure in the PIP product was identified. Based on the crystal structure determined from the in situ neutron diffraction and the intermediate products identified by gas chromatography-mass spectrum, we found that at 20 GPa CHCF forms tilted columns with benzene and hexafluorobenzene stacked alternatively, and leads to a [4+2] polymer, which then transforms to short-range ordered H-F-substituted graphane. The reaction process involves [4+2] Diels-Alder, retro-Diels-Alder, and 1-1' coupling reactions, and the former is the key reaction in the PIP. These studies confirm the elemental reactions of PIP of CHCF for the first time, and provide insight into the PIP of aromatics.

Temperature-Dependent Evolution of Poly(3-Hexylthiophene) Type-II Phase in a Blended Thin Film.

The structure of P3HT in P3HT:PCBM films is examined on a poly(3,4-ethylenedioxythiophene) polystyrene sulfonate ( PEDOT: PSS) substrate subjected to cryo-cooling to low temperature (-143 °C) followed by gradual heating to 50 °C. The behavior of these systems is examined in the absence and presence of an Al electrode on top of the P3HT:PCBM film. At temperatures below -10 °C, only the type-I phase of P3HT is observed. However, the type-II phase of P3HT starts to form near -10 °C, in both the presence and absence of the Al layer. In the system without an Al layer, the type-II phase disappears at 30 °C, but this phase persists to 50 °C in the presence of the Al layer. Concomitant with the formation of the type-II phase, a 1:3 ordered P3HT type-II (1/3,0,0) superlattice peak emerged. The type-II domains tend to form near the Al electrode layer and show a higher degree of alignment than the type-I crystals.

Real-Time Characterization of the Nanostructure of a Metal Electrode on an Organic Thin Film: An In Situ X-Ray Scattering Study.

We measured the real-time variations in the nanostructure of organic (P3HT:PCBM) films and the interfacial structure between the electrode and an organic layer during thermal annealing using in-situ X-ray scattering measurements. An in-situ annealing system is valuable for investigating the nanostructures of organic thin films by simultaneously measuring the X-ray reflectivity and the grazing incidence wide-angle X-ray scattering profile. The interface between a Ca electrode and a P3HT:PCBM film began to degrade at 90 degrees C; however, thermal degradation could be prevented by a pre-annealing process prior to the metal deposition step. Device performance measurements revealed that the interface degradation could explain why organic photovoltaic devices with Ca electrodes performed poorly after an annealing process.

Surface-tuning TiO2 NR photoanodes using CoOx interlayers and NiFe-LDH cocatalysts for photoelectrochemical wastewater treatment.

Increasing multidrug-resistant pathogenic microbial around the world become a global problem, making it imperative to develop effective methods for bacterial inactivation in wastewater. In this study, we propose a multifunctional photoelectrochemical (PEC) system to successfully disinfect microbial cells and degrade orange (II) dyes. CoOx NP were synthesized by spin-coating onto hydrothermally synthesized TiO2 nanorod arrays followed by electrodeposited NiFe-LDH to develop the NiFe-LDH/CoOx NP-TiO2 NRs. Interestingly, spin-coated CoOx NP-TiO2 NRs exhibited a 1.5-fold enhancement in photocurrent (1.384 mA/cm2) than pristine TiO2 NRs (0.92 mA/cm2). A NiFe-layered double hydroxide (LDH) cocatalysts layer further exhibits the maximum photocurrent density of 1.64 mA/cm2 with IPCE of 84.5% at 1.0 VAg/AgCl at 380 nm. Furthermore, NiFe-LDH/CoOx-TiO2 NR photoanodes were effectually employed for photoelectrochemical bacteria disinfection and organic pollutant removals. With NiFe-LDH/CoOx-TiO2 NR, 99% (120 min) bacterial inactivation and 99% (60 min) orange II dye decomposition efficiency was achieved. Superoxide radicals (-O2•), hydroxyl radicals (HO•), and holes (h+) played a critical role in the PEC degradation systems. Due to the synergy between NiFe-LDH cocatalyst and CoOx interlayer, surface water oxidation reactions were accelerated over NiFe-LDH/CoOx NP-TiO2 NRs. The charge transport process in NiFe-LDH/CoOx NP-TiO2 NRs photoanode-based PEC system was proposed in detail.

Impact of molecular symmetry on crystallization pathways in highly supersaturated KH2PO4 solutions.

Solute structure and its evolution in supersaturated aqueous solutions are key clues to understand Ostwald's step rule. Here, we measure the structural evolution of solute molecules in highly supersaturated solutions of KH2PO4 (KDP) and NH4H2PO4 (ADP) using a combination of electrostatic levitation and synchrotron X-ray scattering. The measurement reveals the existence of a solution-solution transition in KDP solution, caused by changing molecular symmetries and structural evolution of the solution with supersaturation. Moreover, we find that the molecular symmetry of H2PO4- impacts on phase selection. These findings manifest that molecular symmetry and its structural evolution can govern the crystallization pathways in aqueous solutions, explaining the microscopic origin of Ostwald's step rule.

Nanostructures of small-molecule organic crystals on capillary wave surfaces with controllable capillary lengths.

We report on the nanostructures of organic small-molecule pentacene crystals that have been vapor-deposited onto the capillary wave surfaces of thin liquid films. The characteristic lateral length of the capillary wave surface or the capillary length can be controlled by changing the thickness of the liquid films and, thus, the van der Waals interaction with the substrate. We find that the morphology of the organic crystals gradually varies from fractals to compact islands as the liquid film thickness increases. The square of average distance between organic crystal grains was also found to be proportional to the liquid film thickness. We discuss the possibility that these effects are driven by capillary fluctuations at the air-liquid interface.

TiO2 nanorod/nanotube interface reconstruction and synergistic role of oxygen vacancies and gold in H-Au-TiO2 NR/NT for photoelectrochemical bacterial inactivation and water splitting.

Photoelectrochemical (PEC) water splitting by semiconductor photoanodes is limited by sluggish water oxidation kinetics coupled with serious charge recombinations. In this paper, an effective strategy of TiO2 nanorod/nanotube nanostructured interface reconstruction, oxygen vacancies and surface modification were employed for stability and efficient charge transport in the photoanodes. Successive anodization and hydrothermal routes were adopted for the TiO2 NR/NT photoanodes interface reconstruction, followed by Au nanoparticles/clusters (Au NP) loading and hydrogen treatment. This resulted in H-Au-TiO2 NR/NT photoanodes. A three-dimensional structure of TiO2 NR on TiO2 NT/Ti foil nanotubes achieved the highest photocurrent density (1.42 mA cm-2 at 0.3 V vs. Ag/AgCl). The optimal oxygen vacancies and Au NP loading on TiO2 NR/NT exhibited 1.62 mA cm-2 photocurrent density at 0.3 V vs. Ag/AgCl in H-Au-TiO2 NR/NT photoelectrode, which is eight times higher than the TiO2 NT/Ti foil. TRPL analyses confirm the hydrogen treatments to TiO2 exhibited the emission lifetime (46 ns) in the H-Au-TiO2 NR/NT photoanodes due to newly formed lower Ti3+-related trapped electron states and Au NP. The optimum H-Au (4)-TiO2 NR/NT photoanodes achieved 95% photoelectrochemical (PEC) bacterial inactivation and effective PEC water splitting with (278 and 135.4) µmol of hydrogen and oxygen generation, respectively. In this study, oxygen vacancies combined with gold particles and interface reconstruction provide an innovative way to design effective photoelectrodes.

Synergistic role of in-situ Zr-doping and cobalt oxide cocatalysts on photocatalytic bacterial inactivation and organic pollutants removal over template-free Fe2O3 nanorods.

Herein, we synthesized in-situ Zr-doped Fe2O3 NRs photocatalyst by successive simple hydrothermal and air quenching methods. The synergistic roles of CoOx (1 wt%) and Zr-doping on bacteria inactivation and model organic pollutants over Fe2O3 NRs photocatalyst were studied in detail. Initially, rod-like Zr ((0-8) %)-doped Fe2O3 NRs were produced via a hydrothermal method. CoOx was loaded onto the Zr ((0-8) %)-doped Fe2O3 NRs) surface by a wet impregnation approach. The Zr-doping conditions and CoOx loadings were judiciously optimized, and a highly photoactive CoOx(1 wt%)/Zr(6%)-doped Fe2O3 NRs photocatalyst was developed. The CoOx(1 wt%) loaded Zr(6%)-doped Fe2O3 NRs photocatalyst revealed 99.4% inactivation efficiency compared with (0, 4 and 8)% Zr-doped Fe2O3 NRs, respectively. After CoOx(1 wt%)/Zr(6%)-doped Fe2O3 NRs photocatalyst treatment, Bio-TEM images of bacterial cells showed extensive morphological deviations in cell membranes, compared with the non-treated ones. Additionally, the optimum CoOx(1 wt%)/Zr(6%)-doped Fe2O3 NRs photocatalyst exhibited 99.2% BPA and 98.3% orange II dye degradation after light radiation for 3 h. This work will provide a rapid method for the development of photostable catalyst materials for bacterial disinfection and organic degradation.

Synergistic role of hydrogen treatment and heterojunction in H-WO3-x/TiO2-x NT/Ti foil-based photoanodes for photoelectrochemical wastewater detoxification and antibacterial activity.

The process of photoelectrochemical wastewater detoxification is limited by significant charge recombination, which is difficult to suppress with efficient single-material photoanodes. We demonstrated the effectiveness of hydrogen treatment in evaluating charge separation properties in WO3-x/TiO2-x NT/Ti foil heterojunction photoanodes. The influence of varying hydrogen annealing (200-400 °C) on the structural and photoelectrochemical properties of WO3/TiO2 NS/NT heterojunction is studied systematically. Additionally, after hydrogen treatment of pristine WO3/TiO2 NT/Ti foil photoanodes, substoichiometric H-WO3-x/TiO2-x NT-300 achieved the 1.21 mA/cm2 photocurrent density, which is 8.06 and 3.27 times than TiO2 NT and WO3/TiO2 NT. The hydrogen-treated H-WO3-x/TiO2-x NT-300 electrode exhibits 3 times greater bulk efficiencies than the WO3/TiO2 NT electrode due to the production of oxygen vacancies at the interface. Additionally, optimum H-WO3-x/TiO2-x NS/NT-300 photoanode exhibited 93.8% E. coli and 99.8% BPA decomposition efficiencies. The present work shows the effectiveness of microwave-assisted H-WO3-x/TiO2-x NT heterojunction photoanodes for organic decomposition and antibacterial activity in a neutral environment without surface-loaded co-catalysts.

In situ fabrication of Ag decorated porous ZnO photocatalyst via inorganic-organic hybrid transformation for degradation of organic pollutant and bacterial inactivation.

In this study, in situ silver (Ag) - porous ZnO photocatalysts were synthesized via solvothermal and post-annealing treatment. The formation of the porous ZnO structure due to the removal of organic moieties from the inorganic-organic hybrids Ag-ZnS(en)0.5 during the annealing process. The optimal Ag-ZnO photocatalyst showed excellent photocatalytic degradation activity, with 95.5% orange II dye and 97.2% bisphenol A (BPA) degradation under visible light conditions. Additionally, the photocatalytic inactivation of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) led to a 97% inactivation rate after 2 h under dark conditions. Trapping experiments suggest that the superoxide anion (O2-) radicals are the main active species to degrade the organic dye. The improved photocatalytic dye degradation activity and inactivation of bacteria were attributed to the synergistic effect of Ag and porous ZnO structure, increased surface area, and efficiently separated the photoexcited charge carriers. This work could provide an effective strategy for the synthesis of porous structures toward organic pollutant degradation and bacterial inactivation in wastewater.

Influence of CoOx surface passivation and Sn/Zr-co-doping on the photocatalytic activity of Fe2O3 nanorod photocatalysts for bacterial inactivation and photo-Fenton degradation.

Hydrothermal and wet impregnation methods are presented in this study for synthesizing CoOx(1 wt%)/Sn/Zr-codoped Fe2O3 nanorod photocatalysts for the degradation of organic pollutants and deactivation of bacteria. A hydrothermal route was used to synthesize self-assembled rod-like hierarchical structures of Sn(0-6%) doped Zr-Fe2O3 NRs. Additionally, a wet impregnation method was used to load CoOx onto the surface of photocatalysts (Sn(0-6%)-doped Zr-Fe2O3 NRs). A series of 1 wt% CoOx modified Sn(0-6%)-doped Zr-Fe2O3 NRs were synthesized, characterized, and utilized for the photocatalytic decomposition of organic contaminants, along with the killing of E. coli and S. aureus. In comparison with 0, 2, and 6% Sn co-doped Zr-Fe2O3 NRs, the CoOx(1 wt%)/4%Sn/Zr-Fe2O3 NRs photocatalyst exhibited an E. coli and S. aureus inactivation efficiencies (90 and 98%). A bio-TEM study of treated and untreated bacterial cells revealed that the CoOx(1 wt%)/4%Sn/Zr-Fe2O3 NRs photocatalyst led to considerable changes in the bacterial cell membranes' morphology. The optimal CoOx(1 wt%)/Sn(4%) co-doped Zr-Fe2O3 NRs photocatalyst achieved degradation efficiencies of 98.5% and 94.6% for BPA and orange II dye, respectively. As a result, this work will provide a facile and effective method for developing visible light-active photocatalysts for bacterial inactivation and organic pollutants degradation.

Stress-induced domain dynamics and phase transitions in epitaxially grown VO2 nanowires.

We demonstrate that surface stresses in epitaxially grown VO2 nanowires (NWs) have a strong effect on the appearance and stability of intermediate insulating M2 phases, as well as the spatial distribution of insulating and metallic domains during structural phase transitions. During the transition from an insulating M1 phase to a metallic R phase, the coexistence of insulating M1 and M2 phases with the absence of a metallic R phase was observed at atmospheric pressure. In addition, we show that, for a VO2 NW without the presence of an epitaxial interface, surface stresses dominantly lead to spatially inhomogeneous phase transitions between insulating and metallic phases. In contrast, for a VO2 NW with the presence of an epitaxial interface, the strong epitaxial interface interaction leads to additional stresses resulting in uniformly alternating insulating and metallic domains along the NW length.

Giant Orbital Anisotropy with Strong Spin-Orbit Coupling Established at the Pseudomorphic Interface of the Co/Pd Superlattice.

Orbital anisotropy at interfaces in magnetic heterostructures has been key to pioneering spin-orbit-related phenomena. However, modulating the interface's electronic structure to make it abnormally asymmetric has been challenging because of lack of appropriate methods. Here, the authors report that low-energy proton irradiation achieves a strong level of inversion asymmetry and unusual strain at interfaces in [Co/Pd] superlattices through nondestructive, selective removal of oxygen from Co3 O4 /Pd superlattices during irradiation. Structural investigations corroborate that progressive reduction of Co3 O4 into Co establishes pseudomorphic growth with sharp interfaces and atypically large tensile stress. The normal component of orbital to spin magnetic moment at the interface is the largest among those observed in layered Co systems, which is associated with giant orbital anisotropy theoretically confirmed, and resulting very large interfacial magnetic anisotropy is observed. All results attribute not only to giant orbital anisotropy but to enhanced interfacial spin-orbit coupling owing to the pseudomorphic nature at the interface. They are strongly supported by the observation of reversal of polarity of temperature-dependent Anomalous Hall signal, a signature of Berry phase. This work suggests that establishing both giant orbital anisotropy and strong spin-orbit coupling at the interface is key to exploring spintronic devices with new functionalities.

Atomic ordering and structural determination of AlGaN/AlN/Si(111) thin films using anomalous X-ray scattering.

The atomic structure and atomic ordering of AlGaN/AlN/Si(111) thin films were studied using regular X-ray diffraction (XRD) and anomalous X-ray scattering (AXS). From regular XRD, both the Al composition and strain status of the AlGaN films are determined. AXS spectra were obtained near Ga K absorption edge at both the fundamental (0002) Bragg peak and non-vanishing forbidden (0001) peak. From this (0001) Bragg peak, long range atomic ordering with 2 bilayer periodicity is confirmed and the order parameter, S is determined from the integrated intensity ratio that is maximized up to 0.08 near x approximately equal to approximately equal to 0.5. The AXS near forbidden peak can be an effective method to reveal the atomic ordering of thin films.

Controlling of the electrical resistivity of GaN layer using AIN nucleation layer.

The sheet resistance (Rs) of undoped GaN films on AIN/c-plane sapphire substrate was investigated. The Rs was strongly dependent on the AIN layer thickness and semi-insulating behavior was observed. To clarify the effect of crystalline property on Rs, the crystal structure of the GaN films has been studied using X-ray scattering and transmission electron microscopy. A compressive strain was introduced by the presence of AIN nucleation layer (NL) and was gradually relaxed as increasing AIN NL thickness. This relaxation produced more threading dislocations (TD) of edge-type. Moreover, the surface morphology of the GaN film was changed at thicker AIN layer condition, which was originated by the crossover from planar to island grains of AIN. Thus, rough surface might produce more dislocations. The edge and mixed dislocations propagating from the interface between the GaN film and the AIN buffer layer affected the electric resistance of GaN film.

In-situ synchrotron X-ray scattering study of thin film growth by atomic layer deposition.

We report an atomic layer deposition chamber for in-situ synchrotron X-ray scattering study of thin film growth. The chamber was designed for combined synchrotron X-ray reflectivity and two-dimensional grazing-incidence X-ray diffraction measurement to do a in-situ monitoring of ALD growth. We demonstrate ruthenium thermal ALD growth for the performance of the chamber. 10, 20, 30, 50, 70, 100, 150 and 250-cycled states are measured by X-ray scattering methods during ALD growth process. Growth rate is calculated from thickness values and the surface roughness of each state is estimated by X-ray reflectivity analysis. The crystal structure of initial growth state is observed by Grazing-incidence X-ray diffraction. These results indicate that in-situ X-ray scattering method is a promising analysis technique to investigate the initial physical morphology of ALD films.