Degree Of Crystalline Order Research Articles

Supramolecular gels - a panorama of low-molecular-weight gelators from ancient origins to next-generation technologies.

Supramolecular gels, self-assembled from low-molecular-weight gelators (LMWGs), have a long history and a bright future. This review provides an overview of these materials, from their use in lubrication and personal care in the ancient world, through to next-generation technologies. In academic terms, colloid scientists in the 19th and early 20th centuries first understood such gels as being physically assembled as a result of weak interactions, combining a solid-like network having a degree of crystalline order with a highly mobile liquid-like phase. During the 20th century, industrial scientists began using these materials in new applications in the polymer, oil and food industries. The advent of supramolecular chemistry in the late 20th century, with its focus on non-covalent interactions and controlled self-assembly, saw the horizons for these materials shifted significantly beyond their historic rheological applications, expanding their potential. The ability to tune the LMWG chemical structure, manipulate hierarchical assembly, develop multi-component systems, and introduce new types of responsive and interactive behaviour, has been transformative. Furthermore, the dynamics of these materials are increasingly understood, creating metastable gels and transiently-fueled systems. New approaches to shaping and patterning gels are providing a unique opportunity for more sophisticated uses. These supramolecular advances are increasingly underpinning and informing next-generation applications - from drug delivery and regenerative medicine to environmental remediation and sustainable energy. In summary, this article presents a panorama over the field of supramolecular gels, emphasising how both academic and industrial scientists are building on the past, and engaging new fundamental insights and innovative concepts to open up exciting horizons for their future use.

Influence of Structural Disorder on the Magnetic Order in FeRhCr Alloys

Magnetic phase transitions in alloys are highly influenced by the sample preparation techniques. In the present research, electronic and magnetic properties of Fe48Cr3Rh49 alloys with varying cooling rates were studied, both experimentally and theoretically. The degree of crystalline ordering was found to depend on the cooling rate employed after annealing the alloy. Modeling of alloy structures with different degrees of crystalline ordering was carried out via strategic selection of substitution positions and distances between chromium atoms. Theoretical calculations revealed significant changes in magnetic and electronic properties of the alloy with different substitutions. A comprehensive analysis of the calculated and experimental data established correlations between structural characteristics and parameters governing the magnetic phase transition. In this study, we also developed a method for evaluating the magnetic properties of the alloys obtained under different heat treatments. The proposed approach integrates atom substitution and heat treatment parameters, offering precise control over alloy manufacturing to effectively tune their essential magnetic properties.

Investigating structural and property modifications in starch from waxy, stick, and H37 sorghum varieties: Advancing starch structure understanding and applications

This study investigated the changes in the structure and properties of starch derived from waxy, stick, and H37 sorghum varieties at various stages of development. The results indicated that as sorghum plants matured, the shape of starch granules became distorted, their size gradually increased from 5 µm to 20 µm, and distinct porous and inner growth rings developed. Furthermore, there were irregular fluctuations in the levels of amylose and CLD. Notably, it was observed that the amylose content (>20%) played a limiting role in the crystallinity of H37 starch, as confirmed by XRD, 13C CP/MAS NMR, and SAXS analyses. Interestingly, the influence of CLD on factors such as lamellar thickness (6.4–7.1 nm), degree of crystalline order, double-helix structure, and the ratio of crystalline to amorphous starch granules (26–31%) harvested at different developmental stages in various sorghum varieties was more pronounced than the impact of amylose content. The study also conducted an in-depth correlation analysis between the structural and property aspects, including thermodynamics, viscoelasticity, and hydrolysis rate, which provides valuable insights for the precise modification of starch structure.

Moisture-related changes in the nanostructure of woods studied with X-ray and neutron scattering

Wood and other cellulosic materials are highly sensitive to changes in moisture content, which affects their use in most applications. We investigated the effects of moisture changes on the nanoscale structure of wood using X-ray and neutron scattering, complemented by dynamic vapor sorption. The studied set of samples included tension wood and normal hardwood as well as representatives of two softwood species. Their nanostructure was characterized in wet state before and after the first drying as well as at relative humidities between 15 and 90%.Small-angle neutron scattering revealed changes on the microfibril level during the first drying of wood samples, and the structure was not fully recovered by immersing the samples back in liquid water. Small and wide-angle X-ray scattering measurements from wood samples at various humidity conditions showed moisture-dependent changes in the packing distance and the inner structure of the microfibrils, which were correlated with the actual moisture content of the samples at each condition. In particular, the results implied that the degree of crystalline order in the cellulose microfibrils was higher in the presence of water than in the absence of it. The moisture-related changes observed in the wood nanostructure depended on the type of wood and were discussed in relation to the current knowledge on the plant cell wall structure.Graphic abstract

Structural and physicochemical properties of mung bean starch as affected by repeated and continuous annealing and their in vitro digestibility

ABSTRACTMung bean starch slurries (75% moisture) were respectively treated by repeated annealing (RANN) at 50°C for eight repetitions (every repetition was treated for 12 h) and continuous annealing (CANN) at the same temperature for 24, 48, 72 and 96 h. After RANN and CANN modifications, variations in the physicochemical properties, structures as well as digestive characteristics of mung bean starch were investigated. Scanning electron microscopy observed the grooves on the surfaces of starch granules became deeper after RANN and CANN modifications, and the cracks in the granule centers were monitored by light microscopy. However, there was no distinct change detected by confocal laser scanning microscopy. RANN and CANN modifications increased the crystallinity and degree of crystalline order, but the crystalline patterns were not changed. Under the same annealing time, RANN samples presented higher crystallinity, gelatinization temperature, enthalpy, peak time, pasting temperature, resistant starch (RS), slowly digestible starch (SDS) and SDS+RS values, but lower solubility, swelling power, peak viscosity, breakdown and rapidly digestible starch (RDS) values than CANN samples. Therefore, RANN could exert conspicuous impacts compared to CANN, which illustrates the annealing impact on starch modification and it could be applied in food processing as an innovative approach.

Transformation of engineered nanomaterials through the prism of silver sulfidation.

Understanding the structure transformation of engineered nanomaterials (ENMs) is a grand measurement challenge, which impacts many aspects of ENMs applications, such as their efficacy, safety, and environmental consequence. To address the significant knowledge gap regarding the fundamental kinetic rate and extent of ENM transformation in the environment, we present a comprehensive and mechanistic structural investigation of the transformation, aggregation, and dissolution behavior of a polyvinylpyrrolidone-coated silver nanoparticle (AgNP) suspension upon sulfidation in moderately reduced hard water with fulvic acid and dissolved Na2S. This reaction is among the most prevalent and industrially and environmentally relevant ENMs transformation. Using ex situ transmission electron microscopy (TEM) and both in situ and ex situ synchrotron-based small angle X-ray scattering (SAXS) and X-ray diffraction (XRD), we find that sulfidation of faceted AgNPs strongly depends on the crystallographic orientation of the facets, with nanometer-scale passivation layers developed on {111} and {100} facets and continuous nucleation and growth on {110} facets. Nanobeam electron diffraction and atomic resolution imaging show Ag and Ag2S domains both possess a high degree of crystalline order, contradicting amorphous structures as previously reported. In situ SAXS/XRD allowed simultaneous determination of the morphological changes and extent of sulfidation of AgNPs. SAXS/XRD results strongly indicate sulfidation follows first-order reaction kinetics without any aggregation. Aided by their size monodispersity, for the first time, using direct, in situ morphology and atomic-structure probes whose results mutually corroborate, we unequivocally determined the sulfidation rate constant of AgNPs under an environmentally relevant condition (≈0.013 min−1 for 68 nm diameter AgNPs). A rigorous analysis of the long-term sulfidation product of the AgNPs under different S/Ag ratios using ex situ SAXS/XRD clearly demonstrates that the silver mass in the original AgNP and transformed Ag/Ag2S NP is preserved. This result has important environmental implications, strongly suggesting that Ag+ ions, a known highly effective antimicrobial agent, are not leached into the solution during sulfidation of AgNPs. The combined nondestructive methodology can be extended to unfold the structure transformation pathway and kinetics in a broad range of ENM systems.

Structure, Physicochemical Properties, and In Vitro Starch Digestibility of Yellow Pea Flour Modified with Different Organic Acids

The objective of this study was to produce a pea flour ingredient with higher slowly digestible (SDS) and resistant (RS) starch fractions for functional food applications. Heat‐moisture treated flour (HMTF) in the presence of citric, gallic, or vanillic acids and esterified flour (EF) with citric acid were prepared and analyzed for structure and functionality using in vitro starch digestibility, differential scanning calorimetry, Rapid Visco Analyzer, swelling factor (SF), amylose leaching (AML), optical microscopy, and Fourier transform infrared (FT‐IR) spectroscopy. Significant (P < 0.05) increases in SDS and RS content of HMTF and EF were observed. Whereas the granule integrity and the birefringence were not affected by modification, the degree of crystalline order, which was determined by FT‐IR 1,047/1,022 cm−1 peak ratio, was decreased. Gelatinization enthalpies of modified flour were lower than that of native flour, whereas the gelatinization endotherms of HMTF were shifted to higher temperatures and those of EF to lower temperatures. Pasting properties were also affected greatly by both treatments. HMTF demonstrated reduced SF and AML, whereas EF had reduced SF and increased AML. Further, the extent of changes in the structure and functionality of HMTF depended on the type of acid utilized. Overall, heat‐moisture treatment with an organic acid and esterification were effective modifications to produce a pea flour ingredient with enhanced SDS and RS content.

Investigation of Gold and Poly(3-Alkylthiophene) interface in top and bottom contact structures

In this report we present the variations in the degree of crystalline order in π-conjugated polymer based thin films occurring at the interface between Gold (Au) and Poly(3-Alkylthiophene)s (P3ATs). For the purpose of study two possible electrode configurations were considered, i.e. the top contact (Au on top of Polymer) and the bottom contact (Polymer on top of Au). The current-voltage characteristics of Au(top)/P3AT/Au(bottom) devices revealed a near ohmic hole injection from bottom electrode but a non-ohmic hole injection from top electrode. Furthermore, the presence of barrier at the Au(top)/P3AT interface was estimated from the first order derivative of lnJ and lnV characteristics of the device under the low electric field biasing. It was observed that the process of coating metal (Au) itself led to significantly decreased polymer crystallinity and that the effect was more profound in top contact configuration compared to bottom contact ones. These observations were further verified through some non-contact mode characterization techniques such as absorption, photoluminescence, Raman spectroscopy and scanning electron microscopy. The difference in the hole injection current from the top and bottom contact electrodes in a Au/P3AT/Au device has been attributed to the creation of distorted π-conjugation due to Au diffusion effect in polymer films in top contact configuration.

Device performance and density of trap states of organic and inorganic field-effect transistors

Trap states, present in any semiconductor, have a large influence on charge transport as well as various other physical processes relevant for device performance. Therefore, quantifying the density of trap states (trap DOS) in a semiconductor is a crucial step towards understanding and improving field-effect transistors (FET), organic photovoltaic cells (OPV) and organic light-emitting diodes (OLED). We present a method to determine the free vs. total charge carrier density in FETs, and therefore the trap DOS, through full normalization of the transfer curve. We apply this method to many different materials, prepared under a wide range of processing conditions, e.g. organic single crystals, thermally evaporated and inkjet printed thin-films, leading to various degrees of order/disorder. They are compared to inorganic thin-films. A quantitative analysis of the spectral density of the trap DOS reveals the trap DOS in p- and n-type semiconductors to be very similar provided they have a similar morphology. The variation by 3 orders of magnitude is dominated by the degree of crystalline order. Further, the trap DOS in organic materials is essentially the same as in inorganic materials, again, provided they have a similar morphology. Surprisingly, ink-jet printed organic polymers have a relatively low trap DOS, which is in between the one of organic single crystals and thin-films.

From organic single crystals to solution processed thin-films: Charge transport and trapping with varying degree of order

We have fabricated single crystal, thermally evaporated, and spin-coated thin-film transistors (TFTs) from the same organic semiconductor N,N′-1H,1H-perfluorobutyl dicyanoperylene carboxydiimide (PDIF-CN2) using various combinations of deposition methods and gate dielectrics to investigate how the charge transport properties vary with the degree of crystalline order. Never before has a semiconductor been studied in such a wide variety of processing methods, allowing cross-comparison of the microscopic factors influencing the charge transport, and in particular the trap density of states (DOS). Excellent transistor performance was achieved for PDIF-CN2 single crystals in combination with Cytop as a dielectric layer resulting in a mobility of up to 6 cm2/Vs, an on/off-ratio exceeding 108, and a subthreshold swing of 0.45 V/dec. Furthermore, gate-bias-stress effects are not present in these transistors and we observed low stress effects in the evaporated TFTs with Cytop as the gate dielectric. These findings are reflected in the trap DOS. The single crystal field-effect transistor with Cytop has a low trap DOS, whereas in evaporated TFTs, the trap DOS is higher by 2–3 orders of magnitude. Surprisingly, the trap DOS of the spin-coated TFT is similar to that in evaporated TFTs, except for additional discrete trap states centered around 0.24 eV below the conduction band.

Microscopic investigation of soot and ash particulate matter derived from biofuel and diesel: implications for the reactivity of soot

Investigation of soot and ash particulate matter deposited in diesel particulate filters (DPFs) operating with biofuel (B100) and diesel (pure diesel: B0 and diesel80/biofuel20 blend: B20) by means of optical microscopy, scanning electron microscopy, and high resolution transmission electron microscopy (HRTEM) reveals the following: the rapeseed methyl ester biofuel used for this study contributes to ash production, mainly of Ca–S– and P-bearing compounds ranging in size between 50 and 300 nm. Smaller ash particles are less common and build aggregates. Ash is deposited on the inlet DPF surface, the inlet channel walls, and in B100-DPF at the plugged ends of inlet channels. The presence of Fe–Cr–Ni fragments, down to tens of nanometers in size within the ash is attributed to engine wear. Pt particles (50–400 nm large) within the ash indicate that the diesel oxidation catalyst (DOC) upstream of the DPF shows aging effects. Radial cracks on the coating layer of the DOC confirm this assumption. The B100-DPF contains significantly less soot than B20 and B0. Based on the generally accepted view that soot reactivity correlates with the nanostructure of its primary particles, the length and curvature of graphene sheets from biofuel- and diesel-derived soot were measured and computed on the basis of HRTEM images. The results show that biofuel-derived soot can be more easily oxidized than diesel soot, not only during early formation but also during and after considerable particle growth. Differences in the graphene sheet separation distance, degree of crystalline order and size of primary soot particles between the two fuel types are in line with this inference.

Substrate-Au catalyst influence on the growth of ZnO nanorods

In this work, the evolution of the Au assisted-growth of ZnO nanorods deposited by vapour phase deposition both on sapphire and on indium–tin–oxide on glass (ITO-glass) substrates has been studied. Our investigation demonstrates that the growth proceeds first as a 3D growth, giving rise to a buffer layer, few microns thick, formed by ZnO grains with different orientation. Then a 1D transition occurs with the nucleation of a dense array of vertically aligned nanorods. A different degree of crystalline order and nanorods alignment was found between the samples grown on ITO-glass and sapphire substrates, which was ascribed to the different morphology that the Au seed layer acquires on the two different substrates. A semi-quantitative analysis of the ZnO crystalline orientation was carried out by X-ray diffraction (XRD) measurements performed at fixed incidence configuration and supported by high resolution scanning electron microscopy (HR-SEM) investigations on focused ion beam (FIB) prepared cross-sections.

Synthesis and characterisation of terbium activated yttrium tantalate phosphor

Terbium activated yttrium tantalate (YTaO 4:Tb) samples were prepared by solid-state reaction from homogeneous mixtures of Y 2O 3 and Ta 2O 5 for host-lattice formation, Tb 4O 7 or Tb(NO 3) 3·5H 2O as activator source and Li 2SO 4, Na 2SO 4, CsF, Na 4P 2O 7 or Na 2B 4O 7 as flux. Photoluminescence (PL) measurements, FT-IR spectroscopy, X-ray diffraction and scanning electron microscopy revealed that PL properties are influenced by the degree of crystalline order and particle morphology and sizes regulated during the thermal synthesis. The effect of flux and terbium concentration on the morpho-structural characteristics and PL properties of YTaO 4:Tb powder is reported.

Studies on terbium activated yttrium based tantalate phosphors

Abstract Terbium activated yttrium niobium tantalate phosphors were prepared by solid-state reaction and were characterized by photoluminescence measurements, X-ray diffraction and scanning electron microscopy. Photoluminescence (PL) of Y 0.95 Tb 0.05 Ta 1− x Nb x O 4 phosphors ( x = 0–1) are influenced by the host-lattice composition, degree of crystalline order and particle morphology and size. The effect of the morpho-structural properties on PL characteristics of Y(Ta,Nb)O 4 :Tb powders is reported.

Nanoscale Cellulose Films with Different Crystallinities and Mesostructures—Their Surface Properties and Interaction with Water

A systematic study of the degree of molecular ordering and swelling of different nanocellulose model films has been conducted. Crystalline cellulose II surfaces were prepared by spin-coating of the precursor cellulose solutions onto oxidized silicon wafers before regeneration in water or by using the Langmuir-Schaefer (LS) technique. Amorphous cellulose films were also prepared by spin-coating of a precursor cellulose solution onto oxidized silicon wafers. Crystalline cellulose I surfaces were prepared by spin-coating wafers with aqueous suspensions of sulfate-stabilized cellulose I nanocrystals and low-charged microfibrillated cellulose (LC-MFC). In addition, a dispersion of high-charged MFC was used for the buildup of polyelectrolyte multilayers with polyetheyleneimine on silica with the aid of the layer-by-layer (LbL) technique. These preparation methods produced smooth thin films on the nanometer scale suitable for X-ray diffraction and swelling measurements. The surface morphology and thickness of the cellulose films were characterized in detail by atomic force microscopy (AFM) and ellipsometry measurements, respectively. To determine the surface energy of the cellulose surfaces, that is, their ability to engage in different interactions with different materials, they were characterized through contact angle measurements against water, glycerol, and methylene iodide. Small incidence angle X-ray diffraction revealed that the nanocrystal and MFC films exhibited a cellulose I crystal structure and that the films prepared from N-methylmorpholine-N-oxide (NMMO), LiCl/DMAc solutions, using the LS technique, possessed a cellulose II structure. The degree of crystalline ordering was highest in the nanocrystal films (approximately 87%), whereas the MFC, NMMO, and LS films exhibited a degree of crystallinity of about 60%. The N,N-dimethylacetamide (DMAc)/LiCl film possessed very low crystalline ordering (<15%). It was also established that the films had different mesostructures, that is, structures around 10 nm, depending on the preparation conditions. The LS and LiCl/DMAc films are smooth without any clear mesostructure, whereas the other films have a clear mesostructure in which the dimensions are dependent on the size of the nanocrystals, fibrillar cellulose, and electrostatic charge of the MFC. The swelling of the films was studied using a quartz crystal microbalance with dissipation. To understand the swelling properties of the films, it was necessary to consider both the difference in crystalline ordering and the difference in mesostructure of the films.

Relationship between crystalline order and melting mechanisms of solids

The mechanism for homogeneous nucleation of the liquid phase in Lennard-Jones solids is studied by combining the Landau free energy approach with some of the methodology developed to characterise transition path ensembles. The second-order bond orientational order parameter, Q 6 which indexes the overall degree of crystalline order, is shown to provide a dynamically significant collective coordinate describing the melting process. Trajectories generated from configurations sampled in the vicinity of the maximum in the Landau free energy curve, F(Q 6), are shown to have equal likelihood of teminating in either the solid or liquid-like free energy minima. It is also demonstrated that Q 6 is necessary but not sufficient as a dynamical coordinate to describe melting and it is necessary to explore possiblities for additional coordinates which are critical for initiating melting. Our sudy suggests that the additional coordinates for describing the melting process would be some type of localised defect, much smaller in spatial extent than the size of the critical nucleus predicted by classical nucleation theory.

The effect of cyclic voltammetry on the crystalline order of PdPc thin films

The degree of crystalline order of evaporated and cast palladium phthalocyanine films was investigated before and after they were submitted to a voltammetric process. X-ray diffraction and UV-vis spectroscopy measurements demonstrated that the electrochemical treatment improves the crystalline quality of the films. The X-ray results revealed an increase of the average size of the crystallites composing the films as well as a decrease in the spacing between the lattice planes in the direction perpendicular to the surface of the film. Optical measurements showed that the electrochemical treatment also introduces an appreciable degree of in-plane ordering. These improvements of crystalline order are observed in both types of films, cast and evaporated, which indicates that the ordering is a direct consequence of the electrochemical treatment and not of the method used for the film deposition.

Molecular dynamics simulations of crystallization of hard spheres.

We have carried out molecular dynamics simulations of the crystallization of hard spheres modeling colloidal systems that are studied in conventional and space-based experiments. We use microscopic probes to investigate the effects of gravitational forces, polydispersity, and of bounding walls on the phase structure. The simulations employed an extensive exclusive particle grid method and the type and degree of crystalline order was studied in two independent ways: by the structure factor, as in experiments, and through local rotational invariants. We present quantitative comparisons of the nucleation rates of monodisperse and polydisperse hard-sphere systems and benchmark them against experimental results. We show how the presence of bounding walls leads to wall-induced nucleation and rapid crystallization, and discuss the role of gravity on the dynamics of crystallization.

Structural and Magnetic Study of FePt Thin Films as a Function of the Deposition Temperature

The structural and magnetic properties of polycrystalline FePt thin films were studied by X-ray diffraction (XRD), atomic force microscopy (AFM) and vibrating sample magnetometry (VSM). The alloys were prepared by dc magnetron sputtering on oxidized silicon substrates with a Pt buffer layer at substrate temperatures (T s ) varying from 300 to 600 °C. XRD measurements show that the increase of T s enhances the degree of crystalline ordering and also the crystallographic grain size. A face centered cubic crystalline structure with (111) texture is observed. AFM images reveal the presence of a granular structure. The morphological grain size increases with the increase of T s . In-plane and out-of-plane hysteresis measurements, using VSM, show that the saturation magnetization M s decreases with increasing T s . The coercivity increases abruptly from 1.3 to 6.0 kOe, in the in-plane geometry, and from 1.6 to 5.6 kOe, in the out-of-plane geometry, when T s varies from 450 to 500 °C.

Biogenic Graphite as a Potential Geomarker—Application to Continental Reconstructions of Pan-African Gondwana Terrains

Graphite is present in nature in several forms. Genetically they may be broadly classified as biogenic and abiogenic. The biogenic forms are those that are clearly derived from an organic precursor while the abiogenic or inorganic forms are more complex from the point of view of their origin, nature and geological relations. As a geomarker, biogenic graphite has certain advantages. It is easily recognized and shows different degrees of crystallinity depending on the relative grades of metamorphism it had undergone. Once it attains a certain degree of crystalline order, it does not revert to a lower state even under changing metamorphic conditions, thereby making it a good mineral geothermometer. It is also found in specific, restricted geological environments and is therefore useful as a boundary marker of ancient sedimentary terrains. These special characteristics of the biogenic type of graphite can be effectively used to trace sites of sedimentary basins and subsequent ocean closures that may have resulted in geosutures. Studies of the Pan-African terrains of the Gondwana crustal fragments as exemplified by the sutures of the Mozambique Belt running through East Africa, Madagascar, Sri Lanka and Antarctica illustrate this point. A further example comes from the Mashan Group of East China, one of the most productive graphite - bearing regions of the world.