Degree Of Structural Order Research Articles

Surface Functionalization of Doxorubicin loaded MCM-41 Mesoporous Silica Nanoparticles by 3-Aminopropyltriethoxysilane for Selective Anticancer 9 Effect on A549 and A549/DOX Cells

In this study, MCM-41 mesoporous silica nanoparticles were successfully synthesized by the condensation of a tetraorthosilicate precursor on a template self-assembled by cetyltrimethylammonium bromide in alkaline. The small-angle x-ray diffraction patterns of MCM-41 indicate that silica nanoparticles possess hexagonal structures with a high degree of structural ordering. Transmission electron microscopy images show that the size of the MCM-41 particles is around 100-120 nm, and the pore sizes range from 2 nm to 4 nm. In addition, the specific surface area of MCM-41 obtained by Brunauer–Emmett–Teller analysis is as high as 987 m2.g−1 and the pore size extracted from nitrogen physical adsorption isotherms is in accordance with the TEM result. Thermogravimetric analysis, Fourier-transform infrared spectroscopy, Zeta potential measurements and photoluminescence measurements show that 3-aminopropyltriethoxysilane (APTES) and doxorubicin were grafted and loaded successfully onto MCM-41 nanoparticles. An assay on fibroblasts, A549 and doxorubicin-resistant A549/DOX cells indicates that the prepared MCM41 grafting APTES nanoparticles are safe to normal cells and toxic to cancer cells in vitro.

Multilayer Diffraction Reveals That Colloidal Superlattices Approach the Structural Perfection of Single Crystals.

Colloidal superlattices are fascinating materials made of ordered nanocrystals, yet they are rarely called “atomically precise”. That is unsurprising, given how challenging it is to quantify the degree of structural order in these materials. However, once that order crosses a certain threshold, the constructive interference of X-rays diffracted by the nanocrystals dominates the diffraction pattern, offering a wealth of structural information. By treating nanocrystals as scattering sources forming a self-probing interferometer, we developed a multilayer diffraction method that enabled the accurate determination of the nanocrystal size, interparticle spacing, and their fluctuations for samples of self-assembled CsPbBr3 and PbS nanomaterials. The multilayer diffraction method requires only a laboratory-grade diffractometer and an open-source fitting algorithm for data analysis. The average nanocrystal displacement of 0.33 to 1.43 Å in the studied superlattices provides a figure of merit for their structural perfection and approaches the atomic displacement parameters found in traditional crystals.

Electronic Transport and Corrosion Mechanisms of Graphite-Like Nanocrystalline Carbon Films Used on Metallic Bipolar Plates in Proton-Exchange Membrane Fuel Cells

Nanocrystalline carbon films, which consist of graphite-like nanocrystals within an amorphous carbon matrix, have recently attracted extensive theoretical and experimental attention. Understanding the electronic transport and corrosion mechanisms of graphite-like nanocrystalline carbon films (GNCFs) is essential for their application in proton-exchange membrane fuel cells (PEMFCs). So far, limited progress has been made on the electronic or atomistic understanding of how the degree of structural order and grain boundaries affect the electronic transport and corrosion behaviors of GNCFs. In this work, using the Landauer-Büttiker formula merged with first-principles density functional theory, the conductance of GNCFs is presented as a function of their crystallinity. As the crystallinity decreases, the electron states around the Fermi level are found to be more spatially localized, thus hindering the electronic transport of GNCFs. Additionally, a systemic picture of the chemical reactivity of nanostructured surface in GNCFs toward typical particles existing in PEMFCs is drawn by ab initio molecular dynamics simulations. Systemic experimental investigations on the corrosion mechanisms of GNCFs used in PEMFCs have been conducted in this work. Compared with pure amorphous carbon films, the GNCFs exhibit higher corrosion current densities due to the preferential corrosion in the larger slit pores at the grain boundaries, but their stability in interfacial contact resistance is significantly improved by the embedded graphite-like nanocrystals, which have high levels of resistance to oxygen chemical adsorptions and act as high-speed ways to transport electrons.

Natural fibers reinforced FDM 3D printing filaments

3D printing is one of the revolutionary techniques in the field of manufacturing. Among the different 3D printing processes FDM is one the most economical and popular method. Commonly used filament material used for printing is PLA. An advantage of PLA is that it is biodegradable. However, PLA in pure form is brittle and has low toughness and flexibility. To overcome the drawbacks, composites of PLA are used. In this review paper we have explored different natural fibres that can be used to make composites with PLA. Hence the study also aims at providing effective waste management using 3D printing. The substances included are mainly agricultural by products, substances that can be extracted from leaves, barks etc. They are not only bio-degradable, they are also economical. Reinforcements discussed include SCGs-PLA (Spent coffee grounds PLA) filaments, rice bran and PLA composites, cellulose-PLA filament etc. Crystallinity refers to degree of structural order in a solid and is an important parameter for producing filaments. Hence the different fiber reinforced composites have been studied as to compare the improvement in crystallinity. The method of preparation and the properties of the composites have been studied. Screw extrusion method is used to produce the filaments. Different mechanical properties like Young’s modulus, stiffness, elasticity, distortion by water absorption, strain etc. have been measured. The cross sections of the filaments are studied under scanning electron microscope. In this review we have discussed the method of preparation of different types of natural fibres and producing the composite filaments of these fibres with PLA matrix. We have also discussed the improvements in mechanical properties that are brought by the fibres to PLA. When choosing a filament for an application, one needs to consider factors like required strength, stiffness in the printed product and the cost of printing. Hence this review serves as a guide to choose the best natural fiber reinforced filament that serves the required purpose.

Eco-efficient cement based on activated coal washing rejects with low content of kaolinite

Coal washing waste was studied as supplementary cementitious material to evaluate it as new raw materials for ecocements. The influence of temperature (room temperature, 450, 650, and 800 °C) and residence time in the muffle furnace (1, 2, and 3 h) on the mineralogy and pozzolanic properties of coal washing waste was analyzed. Different characterization techniques such as PSD, XRF, XRD, FTIR, and elemental analysis were employed. In addition, the degree of structural order–disorder of the kaolinite and the amount of amorphous material in each calcined sample were determined. Subsequently, blended cements were prepared by replacing 20% with calcined waste, and their physical and mechanical behavior were analyzed (water demand, setting time, expansion, pozzolanicity, and compressive strength). The results obtained show that despite the low kaolinite content in the coal waste (14%), it is possible to obtain optimal eco-pozzolans when they are subjected to a thermal activation process above 600 °C, with an optimal temperature around 800 °C. The blended cements comply with the specifications for Type II/A cements, reaching relative compressive strength up to 0.99%. A good correlation between the compressive strengths and amorphous content of the thermally activated waste was obtained.

Comparative Study of the Physical Properties of Fine-Crystalline Mechanoactivated and Sol–Gel Samples of YBa2Cu3O6.92 High-Temperature Superconductors

A technique based on the sol–gel technology is developed for the synthesis of fine-crystalline YBa2Cu3O6.92 (Tc = 91.5 K) high-temperature superconductors (HTSCs), including the step-by-step annealing of the samples in tablet form at the annealing temperature Tann = 750°C in an argon atmosphere. Having the same microstructure with the average crystallite size $$\left\langle D \right\rangle $$ = 200 nm, the sol–gel samples exhibit different magnetic and thermodynamic properties, depending on the number of anneals in argon. Comparison of the characteristics for sol–gel and mechanoactivated fine-crystalline samples of the same composition made it possible to make an assumption about the implementation of incomplete atomic ordering in sol–gel samples at the first stage of annealing with an increase in the degree of structural ordering during the next two stages. This may be the main reason for the change in the physical characteristics of the HTSC sol–gel samples structured at the nanoscale level, depending on the number of annealings in an argon atmosphere.

Characterization of β-Ga2O3 homoepitaxial films and MOSFETs grown by MOCVD at high growth rates

The ultra-wide bandgap semiconductor gallium oxide (Ga2O3) offers substantial promise to significantly advance power electronic devices as a result of its high breakdown electric field and maturing substrate technology. A key remaining challenge is the ability to grow electronic-grade epitaxial layers at rates consistent with 20–40 μm thick drift regions needed for 20 kV and above technologies. This work reports on extensive characterization of epitaxial layers grown in a novel metalorganic chemical vapor deposition tool that permits growth rates of 1.0–4.0 μm h−1. Specifically, optical, structural and electrical properties of epilayers grown at ∼1 μm h−1 are reported, including employment in an operating MOSFET. The films demonstrate relatively smooth surfaces with a high degree of structural order, limited point defectivity (Nd − Na ≈ 5 × 1015 cm−3) and an optical bandgap of 4.50 eV. Further, when employed in a MOSFET test structure with an n+ doped channel, a record high mobility for a transistor structure with a doped channel of 170 cm2 V−1 s−1 was measured via the Hall technique at room temperature. This work reports for the first time a β-Ga2O3 MOSFET grown using Agnitron Technology’s high growth rate MOCVD homoepitaxial process. These results clearly establish a significant improvement in epilayer quality at growth rates that can support future high voltage power device technologies.

Introductory guide to the application of XPS to epitaxial films and heterostructures

XPS is an important characterization method for epitaxial films and heterostructures. Although standard approaches for XPS data collection and analysis provide useful information such as average composition and the presence of contaminants, more in-depth analyses provide information about the film structure, surface termination, built-in electric potentials, and band offsets. The high degree of structural order in these materials enables such information to be extracted from spectral data but also adds complications to the analysis. This guide highlights three topics of importance in this field: (i) the impacts of crystallinity on XPS signals and quantification, (ii) the unexpected spectral line shapes that can occur in unusual or novel materials, and (iii) the ability of XPS to yield information about built-in potentials and band offsets. Concepts are demonstrated using complex oxide heterostructures. Although these topics are highly relevant to epitaxial films and heterostructures, they also apply to single crystals of complex materials.

Properties and oxidation of in-cylinder soot associated with exhaust gas recirculation (EGR) in diesel engines

The properties and oxidation of in-cylinder soot from a diesel engine fueled with n-heptane were explored under the simulated exhaust gas recirculation (EGR) condition, via CO2 addition to the intake air of the engine. A self-developed total cylinder sampling system was employed to obtain the soot samples at the EGR ratios of 0 and 25%, and this study only focused on the soot oxidation that occurred in the soot oxidation-dominated (SOD) phase. Computational fluid dynamics (CFD) simulations were performed to determine the local combustion characteristics related to soot oxidation. Soot oxidation rates were evaluated based on in-cylinder soot mass traces and CFD results. Soot properties were characterized in terms of nanostructure, carbon chemical state, and surface functional groups. Detailed analysis of the soot mass indicates that EGR addition enhances the mass-based specific rate of soot oxidation. However, CFD results show that EGR addition reduces the flame temperature and the concentrations of O2 and OH, and consequently decreases soot surface oxidation rates by O2 and by OH. The characterization of soot properties shows that EGR decreases the degree of structural ordering and results in the formation of more oxygenated and aliphatic C–H groups on the soot surface. This alteration in physico-chemical properties favors soot oxidation during the combustion process, and results in an increase in the mass-based specific rate of soot oxidation in the SOD phase.

Optical parameters and microstructural properties of Solid Bitumens of high reflectance (Impsonites). Reflections on their use as an indicator of organic maturity

Six solid bitumen samples from Paja Formation (Cretaceous of Colombia) were optically, chemically and structurally characterized using bulk chemistry, reflectance indicating surface (RIS), micro-Raman and X-ray diffraction (XRD) parameters. The volatile matter and carbon contents and high random reflectance (Ro%) placed these solid bitumens in the category of cata-impsonites according to Jacob's classification. RIS axes (RMAX, RINT and RMIN) form almost a sphere, and consequently, the anisotropy (Ram or bireflectance values) of these materials is very weak, comparatively to other carbonaceous materials (coals) of similar degree of evolution. The weak anisotropy character of the solid bitumen is related to the absence of pressure in the system, which did not promote the orientation of the basic structural units (BSUs) in a three-dimensional arrangement. The degree of ordering evaluated by Raman parameters, such as full width at half maximum (FWHM) of the D1 and G bands, and XRD parameters, including d002 and crystallite sizes Lc and La, showed that the solid bitumens of the Paja Formation have a low structural order equivalent to high-rank coals, specifically anthracites B (3.0% ≤ Ro < 4.0%), although their reflectance values placed them in a higher rank (Ro > 4.0%). The discrepancy between high reflectance and low degree of structural order can explain why some of the equations used to estimate equivalent vitrinite reflectance (Ro eq. Vite) from solid bitumens do not work universally. Taking in consideration several equations available in the literature, Jacob's equation (Jacob, 1989) was the one that fitted the Ro eq. Vite values in the range of 3.0% to 4.0%, which parallels with the degree of structural order obtained for the solid bitumens. Consequently, Jacob's equation can now be extended to solid bitumen in the range of cata-impsonites.

Effects of the post-annealing reductive-atmosphere-sintered (K0.48Na0.52)NbO3 lead-free piezoceramics

Post-annealing in a weak oxidative atmosphere (a partial pressure of oxygen P(O2) = 1 × 10-6 MPa in high purity N2) was applied to the reductive-atmosphere-sintered (K0.48Na0.52)NbO3 lead-free piezoceramics. Structural characterization indicated that the Nb–O bond length and local structure order degree of the (K0.48Na0.52)NbO3 ceramics increased after post-annealing. The dielectric and impedance spectra analysis revealed that the oxygen vacancies could be compensated after the post-annealing process. The piezoelectric performances of the KNN ceramics post-annealed at 900 °C for 4 h were comparable with that of counterpart sintered in the air. These results indicate that the post-annealing treatment may provide a prospective approach for the fabrication of base metal electrode-cofired KNN multilayer piezoelectric devices.

Interaction of ultra-thin CoTPP films on Fe(001) with oxygen: Interplay between chemistry, order, and magnetism

This work focuses on the stability against the oxidation of the chemical, structural, and magnetic properties of the system consisting of a layer of Co tetra-phenyl porphyrins grown on the top of Fe(001) – p(1 × 1)O. Such a system is characterized by a very high degree of structural order and the existence of magnetic coupling between the molecules and the substrate, even at room temperature, as we recently reported [Jagadeesh et al., Appl. Phys. Lett. 115, 082404 (2019)]. We highlight, by using x-ray photoemission spectroscopy, the effect of porphyrins in screening the substrate from oxidation. The coupling between the magnetic response of the system and the order of the molecular layer is investigated by means of spin-resolved UV photoemission spectroscopy and low-energy electron diffraction, respectively. As a result, a link is eventually found between this response and the chemical and structural stability of the interface.

Annealing effects on the structural and optical properties of undoped and Zr-doped Ba titanate prepared by self-propagating high-temperature synthesis

Undoped and Zr-doped BaTiO powders have been prepared by self-propagating combustion synthesis from suitable precursors. The obtained powders have been subjected to thermal annealing in air at temperatures between 400 and 1200 °C. Experimental findings indicate that annealing affects compositional, structural and optical properties. XRD analysis reveals the presence of a metastable hexagonal phase in powders obtained by SHS. Its relative amount drastically decreases during high-temperature annealing. As-synthesized powders have broad photoluminescence due to the degree of structural order in the powders. This can be also seen from the absorbance spectra, which exhibit a band at 650 nm. F color centers form as a consequence of electron trapping in oxygen vacancies.

Sub kGy photon irradiation alterations in graphite

Present work concerns polymer pencil-lead graphite (PPLG) and the potential use of these in elucidating irradiation-driven structural alterations. The study provides detailed analysis of radiation-induced structural interaction changes and the associated luminescence that originates from the energy absorption. Thermally stimulated emission from the different occupied defect energy levels reflects the received radiation dose, different for the different diameter PPLGs. The PPLG samples have been exposed to photon irradiation, specifically x-ray doses ranging from 1 to 10 Gy, extended to 30–200 Gy through use of a60Co gamma-ray source. Trapping parameters such as order of kinetics, activation energy and frequency factor are estimated using Chen's peak-shape method for a fixed-dose of 30 Gy. X-ray diffractometry was used to characterize the crystal structure of the PPLG, the aim being to identify the degree of structural order, atomic spacing and lattice constants of the various irradiated PPLG samples. The mean atomic spacing and degree of structural order for the different diameter PPLG are found to be 0.3332 nm and 26.6° respectively. Photoluminescence spectra from PPLG arising from diode laser excitation at 532 nm consist of two adjacent peaks, 602 nm (absorption) and 1074 nm (emission), with mean energy band gap values within the range 1.113–1.133 eV.

Study on the synthesis and properties of hierarchically structured electrospun/vapour-grown carbon nanofibres nanocomposites

Herein, we present an extensive analysis of the effect of the initial concentration of iron acetylacetonate(III) (Fe(Acac)3), serving as the catalyst for the growth of carbon nanostructures from the gas phase, on the properties and processes occurring during the synthesis of hierarchically structured electrospun/vapour-grown carbon nanofibres nanocomposites. The examined materials contained from 0 to 4.5% of Fe(Acac)3 and were analysed at various stages of the synthesis. The conducted study revealed empirical formulas correlating the Fe(Acac)3 content with the viscosity of the precursor solutions and the resulting diameters of electrospun carbon nanofibres (eCNF). The concentration of the catalyst exerted a strong impact on the morphology and density of nanoprotrusions on the surface of eCNF. The presence of the grown nanostructures caused an increase in the degree of structural ordering of the nanocomposites. Obtained results suggest also the catalytic effect of Fe(Acac)3 on the cyclisation/oxidation of polyacrylonitrile and proved the hypothesis that the presence of this compound significantly affects the course of the thermal conversion of polyacrylonitrile into the carbon. Evaluation of the wettability revealed the superhydrophobic-superoleophilic character of the nanocomposites and showed that contact angles can be easily controlled by the appropriate selection of initial concentration of Fe(Acac)3.

Life in The Context of Order and Complexity.

It is generally accepted that life requires structural complexity. However, a chaotic mixture of organic compounds like the one formed by extensive reaction sequences over time may be extremely complex, but could just represent a static asphalt-like dead end situation. Likewise, it is accepted that life requires a certain degree of structural order. However, even extremely ordered structures like mineral crystals show no tendency to be alive. So neither complexity nor order alone can characterize a living organism. In order to come close to life, and in order for life to develop to higher organisms, both conditions have to be fulfilled and advanced simultaneously. Only a combination of the two requirements, complexity and structural order, can mark the difference between living and dead matter. It is essential for the development of prebiotic chemistry into life and characterizes the course and the result of Darwinian evolution. For this reason, it is worthwhile to define complexity and order as an essential pair of characteristics of life and to use them as fundamental parameters to evaluate early steps in prebiotic development. A combination of high order and high complexity also represents a universal type of biosignature which could be used to identify unknown forms of life or remnants thereof.

Dosimetric utility of structural changes in gamma irradiated graphite-rich pencils

9B and H grade carbon-based pencil (carbon concentrations approaching 81 and 62 wt respectively %) have been investigated for radiotherapy dosimetry applications, offering low dependence on photon energy and near soft tissue effective atomic number. Comparison has been made with highly oriented pyrolytic graphite (HOPG), a pure and ordered synthetic form of graphite. The samples were exposed to 60Co gamma ray doses from 0 to 20 Gy (encompassing the range of doses utilized in fractionated radiotherapy), structural interaction alterations resulting from the radiation doses being observed via Raman and Photoluminescence (PL) spectroscopy and X-ray diffraction (XRD). Among the most prominent features to be observed in Raman spectra are the so-called G and D peaks, appearing at 1578 cm−1 and 1348 cm−1 respectively. The intensity ratio ID/IG was used for further characterization of the dose-dependent defects produced in the graphitic materials. From PL measurement, sample average energy band gap values are observed to be within the region 1.114–1.116 eV, being considered direct bandgap-like semiconductors. The characteristic XRD crystal plane Miller index (002) peak was observed in order to calculate the atomic spacing, lattice constant and the degree of structural order of the irradiated samples.

Improving the in vitro digestibility of rice starch by thermomechanically assisted complexation with guar gum

The effects of thermomechanical treatment and guar gum (GG) addition on the in vitro digestibility of rice starch have been investigated. Rice starch added with GG at concentrations of 0, 0.025, 0.05, 0.075, or 0.10 g/100 g (wet basis) was subject to a micro-extrusion process. The in vitro digestibility, predicted glycemic index (pGI), and multi-scale structures (granule, lamellar, crystalline, and molecular structures) were examined. Micro-extruded rice starch (MERS) with GG presented reduced digestion rate and pGI, a higher degree of structural ordering, and altered crystalline, single-helical and double-helical structures. Using Pearson correlation analysis, the relationships among extrusion, the molecular interaction and multi-scale structure, and the digestibility were established. The content of resistant components (RC) was positively correlated with crystallinity (r = 0.836, p < 0.05), fractal dimension (r = 0.966, p < 0.05), A-type crystallinity (r = 0.954, p < 0.01), V-type crystallinity (r = 0.987, p < 0.05), R1045/1022 (r = 0.987, p < 0.05), single-helix content (r = 0.897, p < 0.05), and double-helix content (r = 0.991, p < 0.01); and was negatively correlated with pGI (r = −0.947, p < 0.05). Overall, this study showed that thermomechanical treatment assisted the complexation of GG with starch, which could be an effective means to improve the resistant properties of rice starch.

Towards a white-emitting phosphor Ca10V6O25 based material

To achieve a stable material capable of white-light emission, we fabricated Ca10V6O25 by both co-precipitation (CP) and microwave-assisted hydrothermal (MAH) methods at different temperatures. The effects of structural disorder at a short-range (Raman spectra), medium-range (UV–vis spectra), and long-range (X-ray diffraction) on the material structure and its effect on optical properties were investigated. Both CP and the MAH methods were efficient for obtaining pure Ca10V6O25 material with different morphologies. Significant changes in morphology and degree of structural order and disorder were found to affect the photoluminescence (PL) properties. All samples exhibited a broadband PL spectrum, characteristic associated to charge transfer processes of the [VO4]3- group, as well as transitions that occurred in the energy levels located within the band gap. The samples obtained by the MAH method at temperatures of 100 °C and 120 °C exhibited a lower structural disorder (at long- and short-ranges), the CIE chromaticity coordinates were located in the white region, MAH100 (x = 0.311 and y = 0.348) and MAH120 (x = 0.350 and y = 0.368). Furthermore, we conducted a detailed study of temperature dependence of PL spectra. All samples displayed decreased luminescence intensity as temperatures increased and low values of activation energy (approximately 2 meV). Finally, the as-synthetized Ca10V6O25 material has interesting properties for possible applications as a white-emitting phosphor under ultraviolet excitation.

Anomalous Non-Linear to Linear Shift in Magnetoresistance of Amorphous Carbon Films

Non-linear to linear negative magnetoresistance (MR) was studied under the magnetic field ranging from −7 T to 7 T with a change in measurement temperature from 2 K to 300 K. Under the magnetic field of 7 T, a maximum MR magnitude of 8.2% was observed at 2 K. The chemical vapor deposition technique was adopted to synthesize the amorphous carbon thin films. Non-saturated and non-linear negative MR was observed for the lower temperatures, while 10 K was observed as transition temperature. Afterwards, the more likely linear MR behavior was observed up to 300 K. MR shape change was correlated with the structural morphology of metallic disordered graphitic layers or the random stacking of graphene layers with amorphous carbon. The negative MR mechanism for such a non-linear to linear shift was partially assumed as a combined effect of the diffused scattering theory and the weak localization theory. The negative MR effect has a direct relation with the degree of structural order.