Search Results (334)

The stacking of two-dimensional atomic-level thickness materials onto hexagonal boron nitride (h-BN) and graphene (Gr) not only significantly enhances their properties, but also exhibits a multitude of exceptional characteristics, promising widespread applications across various fields. Clay minerals hold profound significance in scientific research not only because of their abundance but also because of their application in geology, environmental science, materials science, and biotechnology. We present a study that uses density functional theory (DFT) to analyze the effect on the mechanical properties of lizardite slab-reinforced Gr or h-BN monolayers. In addition to the reference lizardite slab (Liza-2D), six composites were studied: a monolayer of Gr (h-BN) over the octahedral face of a pristine lizardite slab (Liza-Gr1 (Liza-BN1)), a monolayer of Gr (h-BN) under the tetrahedral face of a pristine lizardite slab (Liza-Gr2(Liza-BN2)), and a pristine lizardite slab sandwiched between two Gr (h-BN) monolayers (Liza-Gr3(Liza-BN3)). We observed that reinforcement by Gr or h-BN significantly increased the bulk, Young’s and shear moduli of the composites. Taking into account that the Gr and h-BN sheets interact weakly by van der Waals interactions with the lizardite slab surface, we estimated the Young’s and shear moduli of the composites by the Rule of Mixtures and obtained a reasonable agreement with those from DFT calculations. Full article

Methylisothiazolinone (MIT) is widely used as a biocide in numerous personal care products, glass-cleaning liquids, paints, and industrial applications. MIT and related isothiazolinones have attracted much attention for their allergenic properties such as contact dermatitis. Although the compound was first prepared in 1964 and has been widely used as a biocide since the 1970s, its crystal structure has so far not been reported. Here we report the solid state structure of MIT as determined by single crystal X-ray diffraction (SC-XRD) analysis of a crystal grown from the melt. MIT crystallizes as a layered structure with short C-H···O hydrogen bonding interactions within the sheets. The average distance between the sheets parallel to (1 0 2) is ca. 3.2 Å. The molecule exhibits a small C-S-N angle of 90.81(2)° and a methyl group that is slightly bent out of the plane of the planar five-membered ring. The sulfur atom does not undergo any significant intermolecular interactions. Full article

Chiral electroactive materials have attracted attention for the effects of electrical magnetochiral anisotropy (eMChA) and chirality-induced spin selectivity (CISS). The combination of tetrathiafulvalene (TTF) with chiral moieties is one way to access chiral electroactive materials. In this paper, we have focused on the fused 2,3-dimethylcyclohexene (DMCh) ring as a substituent with chiral carbon atoms and without heteroatoms, which has not been used in the field of molecular conductors, and we synthesized a new TTF derivative (rac-DMCh-EDT-TTF). We have developed novel molecular conductors (rac-DMCh-EDT-TTF)₂X (X⁻ = PF₆⁻, AsF₆⁻ and ClO₄⁻), which have bilayer conducting sheets composed of the two crystallographically independent molecules. All salts exhibited semiconducting behavior from room temperature down to low temperatures, and a resistivity anomaly was observed at 180–250 K. X-ray structure analysis at 100 K and 263 K and molecular orbital calculations using the results of X-ray structure analysis indicated the emergence of a charge disproportionation between Layers 1 and 2 at the low-temperature phase. Full article

Bombyx mori silk fibroin is a promising biopolymer with notable mechanical strength, biocompatibility, and potential for diverse biomedical applications, such as tissue engineering scaffolds, and drug delivery. These properties are intrinsically linked to the structural characteristics of silk fibroin, making it essential to understand its molecular stability under varying environmental conditions. This study employed molecular dynamics simulations to examine the structural stability of silk I and silk II conformations of silk fibroin under changes in temperature (298 K to 378 K) and pressure (0.1 MPa to 700 MPa). Key parameters, including Root Mean Square Deviation (RMSD), Root Mean Square Fluctuation (RMSF), and Radius of Gyration (R_g) were analyzed, along with non-bonded interactions such as van der Waals and electrostatic potential energy. Our findings demonstrate that both temperature and pressure exert a destabilizing effect on silk fibroin, with silk I exhibiting a higher susceptibility to destabilization compared to silk II. Additionally, pressure elevated the van der Waals energy in silk I, while temperature led to a reduction. In contrast, electrostatic potential energy remained unaffected by these environmental conditions, highlighting stable long-range interactions throughout the study. Silk II’s tightly packed β-sheet structure offers greater resilience to environmental changes, while the more flexible α-helices in silk I make it more susceptible to structural perturbations. These findings provide valuable insights into the atomic-level behavior of silk fibroin, contributing to a deeper understanding of its potential for applications in environments where mechanical or thermal stress is a factor. The study underscores the importance of computational approaches in exploring protein stability and supports the continued development of silk fibroin for biomedical and engineering applications. Full article

Health care workers performing radiography on patients in hospitals typically wear aprons for radiation protection. Protective properties are achieved through a combination of shielding materials and polymers. Various shielding materials are mixed with polymers to prepare composite materials. Numerous methods have been devised to design and alter the composition of these materials to improve the shielding performance of aprons. In this study, the shielding performance was analyzed based on the arrangement of shielding materials, the composition of materials (mixed or single), and the fabrication design of the shielding sheets. Various shielding sheets were created using different arrangements of tungsten oxide, bismuth oxide, and barium sulfate, and their shielding efficacy was compared. The atomic number and density of the shielding material directly affect the shielding property. The effectiveness of the composite sheet increased by more than 5% when positioned close to the X-ray tube. Sheets fabricated from materials separated by type, rather than mixed, exhibited a greater X-ray shielding effectiveness because of their layered structure. Therefore, structural design considerations such as linings, outer layers, and inner layers of protective sheets should be considered for effective shielding in medical institutions. Full article

Recent studies have focused on the development of bio-based products from sustainable resources using green extraction approaches, especially nanocellulose, an emerging nanoparticle with impressive properties and multiple applications. Despite the various sources of cellulose nanofibers, the search for alternative resources that replace wood, such as Lygeum spartum, a fast-growing Mediterranean plant, is crucial. It has not been previously investigated as a potential source of nanocellulose. This study investigates the extraction of novel cellulose micro/nanofibers from Lygeum spartum using a two-step method, including both alkali and mechanical treatment as post-treatment with ultrasound, as well as homogenization using water and dilute alkali solution as a solvent. To determine the structural properties of CNFs, a series of characterization techniques was applied. A significant correlation was observed between the Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) results. The FTIR results revealed the elimination of amorphous regions and an increase in the energy of the H-bonding modes, while the XRD results showed that the crystal structure of micro/nanofibers was preserved during the process. In addition, they indicated an increase in the crystallinity index obtained with both methods (deconvolution and Segal). Thermal analysis based on thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) confirmed improvement in the thermal properties of the isolated micro/nanofibers. The temperatures of maximum degradation were 335 °C and 347 °C. Morphological analysis using a scanning electron microscope (SEM) and atomic force microscope (AFM) showed the formation of fibers along the axis, with rough and porous surfaces. The findings indicate the potential of Lygeum spartum as a source for producing high-quality micro/nanofibers. A future direction of study is to use the cellulose micro/nanofibers as additives in recycled paper and to evaluate the mechanical properties of the paper sheets, as well as investigate their use in smart paper. Full article

The formation of conductive copper patterns on mica holds promise for developing cost-effective flexible electronics and sensing devices, though it is challenging due to the low adhesion of mica’s atomically flat surface. Herein, we present a wet-chemical method for copper patterning on flexible mica substrates via electroless copper deposition (Cu-ELD). The process involves pre-functionalizing 50 µm thick muscovite mica with a titanium dioxide (TiO₂) layer, via a sol–gel dip-coating method with a titanium acetylacetonate-based sol. Photolithography is employed to selectively activate the TiO₂-coated mica substrates for Cu-ELD, utilizing in situ photodeposited silver (Ag) nanoclusters as a catalyst. Copper is subsequently plated using a formaldehyde-based Cu-ELD bath, with the duration of deposition primarily determining the thickness and electrical properties of the copper layer. Conductive Cu layers with thicknesses in the 70–130 nm range were formed within 1–2 min of deposition, exhibiting an inverse relationship between plating time and sheet resistance, which ranged from 600 to 300 mΩ/sq. The electrochemical thickening of these layers to 1 μm further reduced the sheet resistance to 27 mΩ/sq. Finally, the potential of Cu-ELD patterning on TiO₂-functionalized mica for creating functional sensing devices was demonstrated by fabricating a functional resistance temperature detector (RTD) on the titania surface. Full article

The high surface area and transfer-less growth of graphene on dielectric materials is still a challenge in the production of novel sensing devices. We demonstrate a novel approach to graphene synthesis on a C-plane sapphire substrate, involving the microwave plasma-enhanced chemical vapor deposition (MW-PECVD) technique. The decomposition of methane, which is used as a precursor gas, is achieved without the need for remote plasma. Raman spectroscopy, atomic force microscopy and resistance characteristic measurements were performed to investigate the potential of graphene for use in sensing applications. We show that the thickness and quality of graphene film greatly depend on the CH₄/H₂ flow ratio, as well as on chamber pressure during the synthesis. By varying these parameters, the intensity ratio of Raman D and G bands of graphene varied between ~1 and ~4, while the 2D to G band intensity ratio was found to be 0.05–0.5. Boundary defects are the most prominent defect type in PECVD graphene, giving it a grainy texture. Despite this, the samples exhibited sheet resistance values as low as 1.87 kΩ/□. This reveals great potential for PECVD methods and could contribute toward efficient and straightforward graphene growth on various substrates. Full article

This paper examines the atomization characteristics of liquid hydrogen fuel in a premixing tube under different operating conditions. Hydrogen fuel’s unique injection morphology and atomization behavior were analyzed using the Volume of Fluid-to-Discrete Particle Model (VOF to DPM) approach, coupled with the SST $k-\omega$ turbulence model and adaptive mesh refinement. The study revealed that the breakup and transformation of liquid surfaces into particles are significantly impacted by varying air velocities and injection pressure. Specifically, higher air velocities caused the liquid sheet to lengthen and narrow due to intensified vortices. However, the breakup was delayed at higher velocities, occurring at distances of 0.037 m and 0.043 m for air velocities of 10 m/s and 20 m/s, respectively. The research also highlights the significant role that injection pressure plays in fluid sheet breakup. Higher pressures promote better atomization and fuel–lair mixing, resulting in more particles with increased diameters. Notably, the fluid sheet exhibited a small angle of about 43.79° when using the velocity component corresponding to p1 = 0.5 MPa. Similarly, for p2 = 1 MPa and p3 = 2 MPa, the angles were measured to be approximately 47.5° and 49.5°, respectively. Additionally, the study observed that the injection expands in length and diameter as time progresses, indicating fuel dispersion. These insights have significant implications for the design principles of injectors in power generation technologies that utilize liquid hydrogen fuel. Full article

Ripples on graphene play a crucial role in manipulating its physical and chemical properties. However, producing ripples, especially at the nanoscale, remains challenging with current experimental methods. In this study, we report that tiny ripples in graphene can be generated by the adsorption of a single metal cation (Na⁺, K⁺, Mg²⁺, Ca²⁺, Cu²⁺, Fe³⁺) onto a graphene sheet, based on the density functional theory calculations. We attribute this to the cation–π interaction between the metal cation and the aromatic rings on the graphene surface, which makes the carbon atoms closer to metal ions, causing deformation of the graphene sheet, especially in the out-of-plane direction, thereby creating ripples. The equivalent pressures applied to graphene sheets in out-of-plane direction, generated by metal cation–π interactions, reach magnitudes on the order of gigapascals (GPa). More importantly, the electronic and mechanical properties of graphene sheets are modified by the adsorption of various metal cations, resulting in opened bandgaps and enhanced rigidity characterized by a higher elastic modulus. These findings show great potential for applications for producing ripples at the nanoscale in graphene through the regulation of metal cation adsorption. Full article

Hydrogen boride (HB) sheets are emerging as a promising two-dimensional (2D) boron material, with potential applications as unique electrodes, substrates, and hydrogen storage materials. The 2D layered structure of HB was successfully synthesized using an ion-exchange method. The chemical bonding and structure of the HB sheets were investigated using Fourier Transform Infrared (FT–IR) spectroscopy and Transmission Electron Microscopy (TEM), respectively. X-ray photoelectron spectroscopy (XPS) was employed to study the chemical states and transformation of the components before and after atomic hydrogen adsorption, thereby elucidating the atomic hydrogen adsorption process on HB sheets. Our results indicate that, upon atomic hydrogen adsorption onto the HB sheets, the B-H-B bonds were broken and converted into B-H bonds. This research highlights and demonstrates the changes in chemical states and component transformations of the boron element on the HB sheets’ surface before and after atomic hydrogen adsorption, thus providing a clearer understanding of the unique bonding and structural characteristics of the HB sheets. Full article

β-amyloid (Aβ) peptides form self-organizing fibrils in Alzheimer’s disease. The biologically active, toxic Aβ25–35 fragment of the full-length Aβ-peptide forms a stable, oriented filament network on the mica surface with an epitaxial mechanism at the timescale of seconds. While many of the structural and dynamic features of the oriented Aβ25–35 fibrils have been investigated before, the β-strand arrangement of the fibrils and their exact orientation with respect to the mica lattice remained unknown. By using high-resolution atomic force microscopy, here, we show that the Aβ25–35 fibrils are oriented along the long diagonal of the oxygen hexagon of mica. To test the structure and stability of the oriented fibrils further, we carried out molecular dynamics simulations on model β-sheets. The models included the mica surface and a single fibril motif built from β-strands. We show that a sheet with parallel β-strands binds to the mica surface with its positively charged groups, but the C-terminals of the strands orient upward. In contrast, the model with antiparallel strands preserves its parallel orientation with the surface in the molecular dynamics simulation, suggesting that this model describes the first β-sheet layer of the mica-bound Aβ25–35 fibrils well. These results pave the way toward nanotechnological construction and applications for the designed amyloid peptides. Full article

This study explores the mechanical properties of graphene/aluminum (Gr/Al) nanocomposites through nanoindentation testing performed via molecular dynamics simulations in a large-scale atomic/molecular massively parallel simulator (LAMMPS). The simulation model was initially subjected to energy minimization at 300 K, followed by relaxation for 50 ps under the NPT ensemble, wherein the number of atoms (N), simulation temperature (T), and pressure (P) were conserved. After the model was fully relaxed, loading and unloading simulations were performed. This study focused on the effects of the Gr arrangement with a brick-and-mortar structure and incorporation of high-entropy alloy (HEA) coatings on mechanical properties. The findings revealed that Gr sheets (GSs) significantly impeded dislocation propagation, preventing the dislocation network from penetrating the Gr layer within the plastic zone. However, interactions between dislocations and GSs in the Gr/Al nanocomposites resulted in reduced hardness compared with that of pure aluminum. After modifying the arrangement of GSs and introducing HEA (FeNiCrCoAl) coatings, the elastic modulus and hardness of the Gr/Al nanocomposites were 83 and 9.5 GPa, respectively, representing increases of 21.5% and 17.3% compared with those of pure aluminum. This study demonstrates that vertically oriented GSs in combination with HEA coatings at a mass fraction of 3.4% significantly enhance the mechanical properties of the Gr/Al nanocomposites. Full article

The gel properties and molecular conformation of Spanish mackerel myofibrillar protein (MP) induced by soy protein isolate–inulin conjugates (SPI–inulin conjugates) were investigated. The addition of SPI–inulin conjugates significantly enhanced the quality of the protein gel. An analysis of different additives was conducted to assess their impact on the gel strength, texture, water-holding capacity (WHC), water distribution, intermolecular force, dynamic rheology, Raman spectrum, fluorescence spectrum, and microstructure of MP. The results demonstrated a substantial improvement in the strength and water retention of the MP gel with the addition of the conjugate. Compared with the control group (MP), the gel strength increased from 35.18 g·cm to 41.90 g·cm, and WHC increased from 36.80% to 52.67% with the inclusion of SPI–inulin conjugates. The hydrogen bond content was notably higher than that of other groups, and hydrophobic interaction increased from 29.30% to 36.85% with the addition of SPI–inulin conjugates. Furthermore, the addition of the conjugate altered the secondary structure of the myofibrillar gel, with a decrease in α-helix content from 62.91% to 48.42% and an increase in β-sheet content from 13.40% to 24.65%. Additionally, the SPI–inulin conjugates led to a significant reduction in the endogenous fluorescence intensity of MP. Atomic force microscopy (AFM) results revealed a substantial increase in the Rq value from 8.21 nm to 20.21 nm. Adding SPI and inulin in the form of conjugates is an effective method to improve the gel properties of proteins, which provides important guidance for the study of adding conjugates to surimi products. It has potential application prospects in commercial surimi products. Full article

Exposure to high levels of radiation can cause acute, long-term health effects, such as acute radiation syndrome, cancer, and cardiovascular disease. This is an important occupational hazard in different fields, such as the aerospace and healthcare industry, as well as a crucial burden to overcome to boost space applications and exploration. Protective bulky equipment made of heavy metals is not suitable for many advanced purporses, such as mobile devices, wearable shields, and manned spacecrafts. In the latter case, the in-space manufacturing of protective shields is highly desirable and remains an unmet need. Composites made of polymers and high atomic number fillers are potential means for radiation protection due to their low weight, good flexibility, and good processability. In the present work, we developed electrospun composites based on polycaprolactone (polymer matrix) and tungsten powder for application as shielding materials. Electrospinning is a versatile technology that is easily scalable at an industrial level and allows obtaining very lightweight, flexible sheet materials for wearables. By controlling tungsten powder size, we engineered homogeneous, stable and processable suspensions to fabricate radiation composite shielding sheets. The shielding capability was assessed by an in vivo model on prototype composite sheets containing 80 w% of W filler in a polycaprolactone (PCL) fibrous matrix by means of irradiation tests (X-rays) on mice. The obtained results are promising; as expected, the shielding effectivity of the developed composite material increases with the thickness/number of stacked layers. It is worth noting that a thin barrier consisting of 24 layers of the innovative shielding material reduces the extent of apoptosis by 1.5 times compared to the non-shielded mice. Full article