Crystalline Order Research Articles

Editorial: theme issue on complex rheology in biological systems

Editorial: theme issue on complex rheology in biological systems

Substoichiometric Titania As Viable Supports for Direct Electrodeposition of Electrocatalysts for Fuel-Cell Relevant Reactions

One of the obstacles to long-term performance of fuel cells is the corrosion carbon support for the electrocatalysts. Titania (TiO2), with its robust corrosion resistance, is already used as a catalyst support for a range of reactions. However, with a bandgap of around 3 - 3.4 eV depending on the type of polymorph, it is too insulating to serve as an electrocatalyst support. In this study, we explored the electrical and the corrosion-resistance properties of substoichiometric titania, specifically the Ti2O3 and the Ti3O5 phases, in order to assess whether they may be as plausible carbon-free supports for electrocatalysts. Furthermore, we investigated the efficacy of synthesizing low-dimensional Pt, Pd, and combined Pt-Pd based catalysts directly onto substroichimetric titania through iterative electrodeposition steps. The influence of the electrodeposition parameters on the physicochemical and electrochemical properties of Pt particles was investigated using x-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), x-ray absorption spectroscopy (XAS) and cyclic voltammetric techniques. Along with CV analysis, XPS confirmed the successful deposition of (Pt,Pd)-based electrocatalysts onto Ti2O3 and Ti3O5 supports. XAS confirmed that the local atomic structure of the catalysts exhibited the crystalline order expected from Pt and Pd. SEM analysis showed that the electrochemical deposition conditions used in this work favored the formation of particles with hierarchical fractal-like morphologies. Accelerated stress testing (AST) for the oxygen reduction reaction (ORR) using modified DOE protocols were performed to investigate the catalyst stability. After 30K AST cycles, the active electrocatalyst area retained relative to the as-prepared catalysts was ~14 and 22% for electrocatalysts electrochemically deposited on Ti2O3 and Ti3O5, respectively. Figure 1

Edge-Driven Phase Transitions in 2D Ice

2D water, confined by atomically flat layered materials, may transit into various crystalline phases even at room temperature. However, to gain full control over the crystalline state, we should not only confine water in the out of plane direction but also restrict its in plane motion, forming 2D water clusters or ribbons. One way to do this is by using an electric field, in particular the intrinsic electric field of an adjacent polar material. We have found that the crystalline phases of 2D water clusters placed between two hexagonal boron nitride hBN nanoribbons are crucially determined by the nanoribbons edges, the resulting polarity of the nanoribbons, and their interlayer distance. We make use of density functional theory with further assistance of molecular dynamics simulations to establish the comprehensive phase diagrams demonstrating transitions between liquid and solid phases and between the states of different crystalline orders. We also show that the crystalline orders are maintained when water flows between hBN channels under external pressure. Our results open a promising pathway towards the control of water structure and its flow by the use of the microscopic electric field of polar materials.

Dynamic and Static Assembly of Sulfated Cellulose Nanocrystals with Alkali Metal Counter Cations.

Sulfate groups on cellulose particles such as cellulose nanocrystals (CNCs) provide colloidal stability credit to electrostatic repulsion between the like-charged particles. The introduction of sodium counter cations on the sulfate groups enables drying of the CNC suspensions without irreversible aggregation. Less is known about the effect of other counter cations than sodium on extending the properties of the CNC particles. Here, we introduce the alkali metal counter cations, Li+, Na+, K+, Rb+, and Cs+, on sulfated CNCs without an ion exchange resin, which, so far, has been a common practice. We demonstrate that the facile ion exchange is an efficient method to exchange to any alkali metal cation of sulfate half esters, with exchange rates between 76 and 89%. The ability to form liquid crystalline order in rest was observed by the presence of birefringence patterns and followed the Hofmeister series prediction of a decreasing ability to form anisotropy with an increasing element number. However, we observed the K-CNC rheology and birefringence as a stand-out case within the series of alkali metal modifications, with dynamic moduli and loss tangent indicating a network disruptive effect compared to the other counter cations, whereas observation of the development of birefringence patterns in flow showed the absence of self- or dynamically-assembled liquid crystalline order.

Insight into the improving effect on multi-scale structure, physicochemical and rheology properties of granular cold water soluble rice starch by dielectric barrier discharge cold plasma processing

In the present study, the alcohol/alkali treatment of starch produced granular cold-water-soluble starch (CWS) and explored the improvement of dielectric barrier discharge cold plasma (CP) on its multi-scale structure, physicochemical and rheological properties. The granular integrity of the prepared CWS was destroyed, and the crystal structure changed from type A to amorphous. CP processing reduced the molecular weight of CWS and the ratio of long amylopectin to produce small molecular parts with appropriate chain length. CP processing also resulted in a decrease in amylose content, relative crystallinity, and short-range order. These structural changes promote the improvement of CWS properties. For example, CP-treated CWS starch exhibited better solubility, swelling power, flowing capacity, and enzymatic hydrolysis properties. Therefore, this research showed that cold plasma technology is suited to improve the structure and enhance properties of CWS to tailor starch to the desired food applications. • The granular cold-water-soluble starch (CWS) was modified cold plasma (CP). • CP degraded the CWS molecules and reduced the molecular weight. • CP reduced the crystallinity of CWS and led to a more disordered structure. • CP-treated improves the cold-water solubility of CWS. • CP-treated CWS showed better fluidity and enzymatic hydrolysis properties.

2D‐FFCASP—A New Approach for 2D Structure Prediction Applied to Self‐Assemblies of DNA Bases

AbstractBiomolecular self‐assembly on surfaces is an emerging and exciting field for the fabrication of 2D nanostructures that are being used in a wide range of applications. Self‐assembly of the nucleic acid bases, which are mostly stabilized by hydrogen bonding, in both solution and solid have been well characterized by various experimental techniques such as nuclear magnetic resonance (NMR) and scanning tunneling microscopy (STM). Especially for the surface based self assemblies, the resolution of STM images is quite insufficient to reveal the dominating intermolecular interactions which lead to the formation of self‐assembled DNA bases. Moreover, it is also possible to form crystalline order self assemblies by finding suitable experimental conditions. This fact allows the application of crystal structure prediction (CSP) tools for the discovery of ordered self assemblies. In this regard, the existing CSP method called FFCASP has been extended with a new implementation allowing the prediction of 1D or 2D periodic and nonperiodic structures. The new approach, 2D‐FFCASP, has been applied to four DNA bases and the best resulting structures have been further evaluated by dispersion‐corrected density functional theory (DFT‐D) and cluster in a molecule local correlation approach at the second‐order Møller–Plesset perturbation (CIM‐RI‐MP2). 2D‐FFCASP successfully reproduced the known self‐assemblies of DNA bases in addition to many newly found isoenergetic structures.

Improvement of cooking and textural properties of rice flour-soy protein isolate noodles stabilised with microbial transglutaminase and glucono-δ-lactone and dried using superheated steam.

In a bid to produce rice flour noodles with improved texture and reduced cooking time, rice flour-soy protein isolate noodles (RNS) were structurally enhanced by a combined treatment (COM) of microbial transglutaminase (MTG) with glucono-δ-lactone (GDL). The RNS-COM was either dried using superheated steam (SHS) to yield RNS-COM-SHS or steamed for 10 min (S10) before air drying to produce RNS-COM-S10 noodles. Control samples were SHS-dried rice flour (RN-SHS) and air-dried RN-S10 noodles. In general, textural and microstructural properties indicated higher textural properties and a more robust network in RNS-COM-SHS and RNS-COM-S10 than in other noodles. However, optimum cooking time (P < 0.5) was in the order; RN-SHS, RNS-COM-SHS < RN-S10 < RNS-COM-S10. As a result of the COM treatment, structurally enhanced noodles were more resistant to cooking. As applied in RNS-COM-SHS noodles, SHS was able to improve cooking quality, probably through the formation of bigger and evenly spread pores that had promoted faster gelatinisation of starch, with a high order of relative starch crystallinity.

The influence mechanism of brown rice starch structure on its functionality and digestibility under the combination of germination and zinc fortification

This study explored the influence of germination and fortification on the functionality and digestibility of brown rice from the perspective of starch structure changes. The surface of germinated brown rice starch appeared some pits and holes under the action of endogenous hydrolase, and the amylose content, relative crystallinity and short-range order of the starch decreased significantly after germination. However, the fortification treatment seemed to intensify the enzymatic hydrolysis of germinated brown rice starch, showing deeper pits, lower short-range order and less double helix structure. These changes in structural characteristics led to a significant decrease in peak viscosity, enthalpy change (ΔH) and starch hydrolysis rate after germination and fortification treatment. As the germination time increased, the trend became more obvious. And the peak viscosity and enthalpy change (ΔH) of fortified brown rice reached the minimum values of 290.89 cP and 13.73 J/g after 34 h of germination, respectively, while the starch hydrolysis rate reached the maximum value of 85.42 %. Overall, the combination of germination and fortification could be an effective method to adjust the functional and digestive characteristics of starch by changing its structural characteristics.

Textured MAPbI3 Thin Films Achieved via Solvent Engineering in the Solution‐Shearing Process

Solvent mixtures for making uniform, crystalline methylammonium lead iodide (MAPbI3) perovskite films are provided. The solvents dimethyl sulfoxide (DMSO), γ‐butyrolactone (GBL), and 1‐methyl‐2‐pyrrolidinone (NMP) are examined as well as their binary combinations to prepare solution‐sheared perovskite films at higher than 150 °C temperatures. Characterization methods such as imaging, X‐ray diffraction, grazing‐incidence wide‐angle X‐ray scattering, and photoluminescence (PL) to evaluate the crystal size, quality, and ordering that determine the viability of these films for device applications are explored and then a perovskite solar cell is made to test the stability of the most promising film. Excellent macroscopic crystals, over 1 mm in length, are achieved using a solvent mixture containing equal volumes of DMSO and NMP. These superior 3D MAPbI3 films, which retain solvent–perovskite intermediate phases and exhibit high crystalline ordering, are essential for high‐performing and stable optoelectronic devices.

Kombucha Bacterial Cellulose Synthesized by Liquid Fermentation on Black Tea (Camellia sinensis): Effect of the Sucrose

Bacterial cellulose membranes were synthesized by liquid fermentation of the Kombucha strain into black tea (Camellia sinensis) at different concentrations of sucrose. Structural properties of bacterial cellulose Kombucha, such as lateral order index (LOI), total crystallinity index (TCI), hydrogen bond intensity (HBI), fraction (fa), as well as their dependence on sucrose content were evaluated by Fourier transform infrared spectroscopy, using different absorption bands of the vibrational spectrum. It was thus observed that sucrose tends to crystallize bacterial cellulose, due to the increase in the total index of crystallinity and lateral order, as well as the fraction (fa), while the index of hydrogen bonds decreased. The addition of organic cocoa (Theobroma cacao) in the culture medium prior to fermentation produced membranes with properties very similar to those prepared only with black tea. Obtaining type I cellulose and crystallization controlled by this process could contribute to obtaining high crystallinity membranes for biomedical and bioelectronic applications.

A comprehensive review on the synthesis techniques of porous materials for gas separation and catalysis

AbstractIntrinsic structural characteristics of porous materials have found significant applications in selective separation of gases and heterogeneous catalysis. While using porous materials for gas separation and catalysis, some of the challenging issues are the strength of catalytic sites, hydrothermal stability, crystalline order of solids, and selectivity. Researchers' ability to engineer the synthesis strategies rationally can help overcome technological challenges. In recent years, breakthroughs in porous materials are focused on developing different chemistries to control the pore architecture. This review focuses on recent advances made in synthesis strategies of porous materials and their impact on gas separation and catalysis applications. A significant part of this review is devoted to various synthesis methods, such as various types of templating methods, molecular layer deposition, sol–gel technique, and polymerization methods. Improvement in various catalytic reactions and gas separations due to different functionalization methods is also summarized. Lastly, we have discussed the applications of porous materials in the form of adsorbents and membranes in commercial processes. We hope that this review will serve as a quick reference for beginners who want to synthesize porous materials with control of pore structure.

Recent Developments in Plasmonic Alloy Nanoparticles: Synthesis, Modelling, Properties and Applications.

Despite the traditional plasmonic materials are counted on one hand, there are a lot of possible combinations leading to alloys with other elements of the periodic table, in particular those renowned for magnetic or catalytic properties. It is not a surprise, therefore, that nanoalloys are considered for their ability to open new perspectives in the panorama of plasmonics, representing a leading research sector nowadays. This is demonstrated by a long list of studies describing multiple applications of nanoalloys in photonics, photocatalysis, sensing and magneto-optics, where plasmons are combined with other physical and chemical phenomena. In some remarkable cases, the amplification of the conventional properties and even new effects emerged. However, this field is still in its infancy and several challenges must be overcome, starting with the synthesis (control of composition, crystalline order, size, processability, achievement of metastable phases and disordered compounds) as well as the modelling of the structure and properties (accuracy of results, reliability of structural predictions, description of disordered phases, evolution over time) of nanoalloys. To foster the research on plasmonic nanoalloys, here we provide an overview of the most recent results and developments in the field, organized according to synthetic strategies, modelling approaches, dominant properties and reported applications. Considering the several plasmonic nanoalloys under development as well as the large number of those still awaiting synthesis, modelling, properties assessment and technological exploitation, we expect a great impact on the forthcoming solutions for sustainability, ultrasensitive and accurate detection, information processing and many other fields.

Improving crystallinity and ordering of PBTTT by inhibiting nematic to smectic phase transition via rapid cooling

The liquid crystalline (LC) phase can promote the long-range ordering of conjugated polymer films. Therefore, the effects of different single LC phases and the coexistence of multiple LC phases on film morphology deserve further study. In this work, we found that distinct film morphologies can be obtained by undergoing different LC transition processes. It was demonstrated that Poly(2,5-bis(3-alkylthiophen-2-yl)thieno[3,2-b]thiophene) (PBTTT) undergoes a high-temperature nematic LC I phase and a low-temperature smectic LC Ⅱ phase by optical images, in-situ UV–vis spectroscopy and Fourier transform infrared spectroscopy (FTIR). When the PBTTT is rapidly cooled from the melt to solid thin film at 130 °C/min, the films crystallize from LC I directly and keep the nematic-like texture. When the melt is slowly cooled at 1 °C/min, the films crystallize after transforming from LC I to LC II and retain the smectic-like texture. The former films exhibit 24.5 times higher crystallinity than the latter. Meantime, the lamellar packing d100 distance increases from 21.06 Å to 23.85 Å, and the intercrystallite distance increases from 9 nm to 25 nm, respectively. The restraint chain mobility in the highly ordered smectic phase and the nanoconfinement effect induced by phase separation between LC I and LC II are responsible for the reduced crystalline order in the films experienced by LC I and LC II. This work emphasizes the importance of LC phases and rational annealing programs on morphology design.

Observation of two-step melting on a sphere

Melting in two-dimensional flat space is typically two-step and via the hexatic phase. How melting proceeds on a curved surface, however, is not known. Topology mandates that crystalline particle assemblies on these surfaces harbor a finite density of defects, which itself can be ordered, like the icosahedral ordering of 5-coordinated disclination defects on a sphere. Thus, melting even on a sphere, the simplest closed surface, involves the loss of both crystalline and defect order. Probing the interplay of these two forms of order, however, requires a system in which melting can be performed in situ, and this has not been achieved hitherto. Here, by tuning interparticle interactions in situ, we report an observation of an intermediate hexatic phase during the melting of colloidal crystals on a sphere. Remarkably, we observed a precipitous drop in icosahedral defect order in the hexatic phase where the shear modulus is expected to vanish. Furthermore, unlike in flat space, where disorder can fundamentally alter the nature of the melting process, on the sphere, we observed the signature characteristics of ideal melting. Our findings have profound implications for understanding, for instance, the self-assembly and maturation dynamics of viral capsids and also phase transitions on curved surfaces.

Revealing and Controlling Energy Barriers and Valleys at Grain Boundaries in Ultrathin Organic Films.

In organic electronics, local crystalline order is of critical importance for the charge transport. Grain boundaries between molecularly ordered domains are generally known to hamper or completely suppress charge transfer and detailed knowledge of the local electronic nature is critical for future minimization of such malicious defects. However, grain boundaries are typically hidden within the bulk film and consequently escape observation or investigation. Here, a minimal model system in form of monolayer-thin films with sub-nm roughness of a prototypical n-type organic semiconductor is presented. Since these films consist of large crystalline areas, the detailed energy landscape at single grain boundaries can be studied using Kelvin probe force microscopy. By controlling the charge-carrier density in the films electrostatically, the impact of the grain boundaries on charge transport in organic devices is modeled. First, two distinct types of grain boundaries are identified, namely energetic barriers and valleys, which can coexist within the same thin film. Their absolute height is found to be especially pronounced at charge-carrier densities below 1012 cm- 2 -the regime at which organic solar cells and light emitting diodes typically operate. Finally, processing conditions by which the type or energetic height of grain boundaries can be controlled are identified.

Toward functionalization without functional agents: An X-ray photoelectron spectroscopy study

Changes to the surface composition of hydroxyapatite were measured after incubations in water, in ethanol or in a mixed aqueous-alcoholic medium. Ethanol decreased the surface presence of calcium ions in direct proportion to its amount in the medium. Because of its lower polarity than that of water, ethanol also increased the interfacial energy, in response to which the surface relaxed by rearranging into a more disordered state, as indicated by the increase in the heterogeneity of both calcium and oxygen electronic states. Accordingly, the binding energy of core-level oxygen electrons consistently increased with the concentration of ethanol and was compensated for by the decrease of the corresponding binding energies in calcium atoms, attesting to the weakened ionic bonds at the interface. The weakened ionic bonds increased the metallicity of the calcium ion, which prompted the offset of the valence band edge determined by the Ca4s electron energy state toward the Fermi level and the conduction band, thus shrinking the band gap and increasing the electrical conductivity of the surface. The surface energy reduction entailing the partial loss of the crystalline order at the surface predisposed the nanoparticles incubated in alcoholic media for diminished sorption of proteins, but also for an augmented osteogenic response. These results demonstrate that surface functionalization of materials for various physicochemical and biological effects could be achieved without the use of chemical ligands. Rather, more economical design techniques stemming from the repertoire of materials science and engineering could be employed with equally satisfactory outcomes.

Polypyrrole with appreciable solubility, crystalline order and electrical conductivity synthesized using various dopants appropriate for device applications

Polypyrrole with appreciable solubility, crystalline order and electrical conductivity synthesized using various dopants appropriate for device applications

Structural heterogeneity in non-crystalline Tex Se1−x thin films

Rapid crystallization behavior of amorphous TexSe1−x thin films limits the use of these alloys as coatings and in optoelectronic devices. Understanding the short- and medium-range ordering of the amorphous structure and the fundamental physics governing the crystallization of the films is crucial. Although the lack of long range crystalline order restricts the characterization of the amorphous films, electron microscopy offers a way to extract information about the nanoscale ordering. In this paper, the local ordering of amorphous TexSe1−x thin films with x=0.22, 0.61, 0.70, 0.90, and 1 grown by thermal evaporation is investigated using radial distribution function (RDF) and fluctuation electron microscopy (FEM) analysis. RDF results show that the nearest-neighbor distances of selenium (Se) and tellurium (Te) in their crystalline structure are preserved, and their bond lengths increase with the addition of Te. Density functional theory (DFT) calculations predict structures with interatomic distances similar to those measured experimentally. Additionally, fluctuations in atomic coordination are analyzed. Medium range order (MRO) analysis obtained from FEM and DFT calculations suggests that there are at least two populations within the chain network structure, which are close to the Se–Se and Te–Te intrachain distances. For the binary alloy with x &amp;gt; 0.61, TexSe1−x, Te–Te like populations increase and Te fragments might form, suggesting that the glass forming ability decreases rapidly.

Spatial manipulation of topological defects in nematic shells.

It is well known that positions of topological defects (TDs) in liquid crystals can be manipulated experimentally by locally distorting the liquid crystalline (LC) order, as for example by melting induced by optical tweezers. In this work, we study numerically the nematic ordering profiles and the corresponding topological defect configurations in thin nematic liquid crystalline shells controlled by imposed local distortion of LC order. We demonstrate that within curved LC films such manipulations could be strongly affected by local Gaussian curvature if it exhibits strong spatial variations. We use mesoscopic approach in which the shell geometry and LC orientational order are described by curvature of the surface and nematic order parameter tensor. For illustration purposes, we consider LC shells exhibiting spherical topology. We show that on increasing prolateness of shells, which imposes spatially inhomogeneous Gaussian curvature, TDs are relatively strongly "glued" to a local Gaussian curvature.

Performance enhancement in organic solar cells and photodetectors enabled by donor phase optimization at the surface of hole transport layer

The domain purity, material crystallinity and distribution at the interface between the active layer and the transport layer have an important impact on the performance of organic solar cells (OSCs) and organic photodetectors (OPDs), while this focal issue has received less attention in previous studies. From this perspective, a new method to simultaneously enhance the performance of OSC and OPD is proposed, namely, using a sequential deposition method to first construct a compact stacking structure of dual-donor (D18-Cl:PTO2) eutectic in the donor layer, and then induce the ordered deposition of the acceptor (Y6). Compared with the conventional bulk heterojunction (BHJ), the active layer realized by this method not only improves the crystallinity and stacking order of the constituent material on the surface of the transport layer, but also regulates a good vertical distribution, which is conducive to improving the charge transport and extraction efficiency, reducing the leakage current, and enhancing the stability of the device. As a result, the OSC device based on the D18-Cl:PTO2/Y6 structure achieves a power conversion efficiency of up to 17.65% and good light-degradation stability, which is much better than that of BHJ-based OSC (PCE of 16.37%). For the OPD, the dark current at reverse bias is reduced by more than an order of magnitude, and the maximum responsivity is improved to 0.52 A/W through the optimization of the donor phase at the interface. Moreover, the strategy does not require additional post-processing compared to the BHJ preparation, which reduces the device construction cost and process complexity, providing an effective way for developing high-performance organic optoelectronic devices.