Structural Properties Research Articles

The unusual structural properties and potential biological relevance of switchback DNA

Synthetic DNA motifs form the basis of nucleic acid nanotechnology. The biochemical and biophysical properties of these motifs determine their applications. Here, we present a detailed characterization of switchback DNA, a globally left-handed structure composed of two parallel DNA strands. Compared to a conventional duplex, switchback DNA shows lower thermodynamic stability and requires higher magnesium concentration for assembly but exhibits enhanced biostability against some nucleases. Strand competition and strand displacement experiments show that component sequences have an absolute preference for duplex complements instead of their switchback partners. Further, we hypothesize a potential role for switchback DNA as an alternate structure in sequences containing short tandem repeats. Together with small molecule binding experiments and cell studies, our results open new avenues for switchback DNA in biology and nanotechnology.

Erosion performance of direct-aged Al2O3-reinforced plasma-sprayed composite coatings at high-temperature conditions

The present investigation evaluates the influence of furnace heat-treatment (HT) on the microstructure, microhardness, fracture toughness and erosion resistance of three plasma sprayed composite coatings: a Inconel625–30 wt% micron-sized Al2O3 (In625-MHT) coating, a Inconel625–30 wt% nano-sized Al2O3 (In625-NHT) coating and a Inconel625–15 wt% micron-sized Al2O3 + 15 wt% nano-sized Al2O3 (In625-BHT/bimodal) coating. High temperature solid particle erosion tests were conducted at 900 °C temperature and with at two different impingement angles (90 and 30) in simulated environment using standard erosion-test rig. Coatings were subjected to detailed mechanical and microstructural analysis in order to better understand their erosion mechanism and structure–property correlation. By healing pores and cracks, the furnace HT increases the coatings’ erosion resistance in the order of In625-BHT, In625-NHT, and In625-MHTcoating. In addition, the mechanical properties of In625-BHT coating like porosity (1.0 ± 0.09%), micro-hardness (1299 ± 25Hv) and fracture toughness (5.9 MPa√m) are significantly improved after HT. The presence of grooves and lips on the surfaces of uncoated substrates provides clear evidence that the erosion mechanism involves the combined processes of micro-ploughing and micro-cutting indicating ductile erosion mode. However unimodal and bimodal composite coatings demonstrated a brittle erosion mode.

One pot green process for facile fractionation of sorghum biomass to lignin, cellulose and hemicellulose nanoparticles using deep eutectic solvent

Complete valorization of lignocellulosic biomass is crucial for bio-based biorefineries to fulfil the circular bioeconomy concept. However, the existence of lignin carbohydrate complexes (LCC) in biomass hinders the simultaneous fractionation of biomass components, such as lignin, hemicellulose and cellulose, for subsequent biorefining processes. This study explores for the first time a novel approach tailored for the deconstruction of sorghum biomass components through efficient breakdown of LCC. Selective targeting of the major LCC linkages binding xylan and lignin was performed using an ultrasound-assisted deep eutectic solvent under mild treatment conditions. This process yielded a maximum cellulose content of 98.3 %, hemicellulose content of 95.2 %, and lignin content of 94.6 %, with the highest purities of 99.43 %, 96.71 %, and 98.12 %, respectively. FTIR, 2D-HSQC NMR and XRD analyses confirmed that most of the structural properties of lignin, hemicellulose, cellulose are retained. The lignocellulosic components were successfully valorised to cellulose, hemicellulose, and lignin nanoparticles with mean sizes of 64.5 ± 6 nm, 72.8 ± 4 nm and 57.2 ± 8 nm respectively, with good thermal stability. The proposed green process enables the complete utilization of agro-residue feedstock for the preparation of biomass-derived nanoparticles, thereby accelerating the economic and industrial prospects of bio-based biorefineries.

First-Principle Characterization of Structural, Electronic, and Optical Properties of Tin-Halide Monomers.

The growing interest in tin-halide semiconductors for photovoltaic applications demands in-depth knowledge of the fundamental properties of their constituents, starting from the smallest monomers entering the initial stages of formation. In this first-principles work based on time-dependent density-functional theory, we investigate the structural, electronic, and optical properties of tin-halide molecules SnXn 2-n, with and X=Cl, Br, I, simulating these compounds in vacuo as well as in an implicit solvent. We find that structural properties are very sensitive to the halogen species while the charge distribution is also affected by stoichiometry. The ionicity of the Sn-X bond is confirmed by the Bader charge analysis albeit charge displacement plots point to more complex metal-halide coordination. Particular focus is posed on the neutral molecules SnX2, for which electronic and optical properties are discussed in detail. Band gaps and absorption onset decrease with increasing size of the halogen species, and despite general common features, each molecule displays peculiar optical signatures. Our results are elaborated in the context of experimental and theoretical literature, including the more widely studied lead-halide analogs, aiming to contribute with microscopic insight to a better understanding of tin-halide perovskites.

Investigations on the mechanical properties of multi-directional graded cellular structures based on gyroid surface

A novel multi-directional graded cellular structure based on gyroid surface is designed and additively manufactured in this work. Through quasi-static compression tests, their mechanical characteristics were assessed. The results revealed that cellular structures featuring bidirectional and three-directional gradients exhibit notably enhanced mechanical performance compared to unidirectional gradients (8.8% for energy absorption, 89.7% for compressive strength, 53.9% and 66.3% for elastic modulus and yield strength, respectively). Moreover, the mechanical properties of structures with three-directional gradients can be finely tuned by adjusting gradient variation. Consequently, these innovative multi-directional graded cellular structures offer promising potential across diverse applications as efficient energy absorbers.

Structural, optical and magnetic properties of chemically grown copper oxide nanoparticles: An insight into anticancer activities

Self-assembling nanorods like copper oxide (CuO) nanoparticles (NPs) have been successfully synthesized using two different copper cationic precursors to investigate their structural, optical, and magnetic properties. These NPs are employed in anticancer applications. Both the CuO-NPs have been tested for their toxicity on human cells. The XRD patterns confirm the formation of monoclinic crystal structures for both the systems. The FESEM microstructural surface morphology shows high agglomeration and a typical elemental composition is evaluated from EDAX analysis. The HRTEM analysis reveals high crystalline CuO nanorods with diameters in the range of 60 ∼ 94 nm and 09∼ 22 nm for two different nanoparticles named CuO-NPs1 and CuO-NPs2, respectively. The optical band gap of CuO-NPs has been calculated from UV–visible absorption spectra and is found to be 2.18 eV and 2.55 eV for CuO-NPs1 and CuO-NPs2, respectively. FTIR analysis provides insights into the chemical compositions of both the CuO-NPs. Magnetization study using vibrating sample magnetometer (VSM) indicates antiferromagnetic-like properties associated with weak ferromagnetic behaviour. Cytotoxicity tests on MCF-7 cell lines show that CuO-NPs2 exhibit more pronounced effect with IC50 of 22.95 μg/mL. The toxicity of both the CuO-NPs are also assessed using human lymphocytes, suggesting that CuO-NPs could be promoted as anticancer agents while remaining non-toxic to biological systems.

Structural phase transition, relaxor behavior, and ultra-low strain hysteresis in BaTiO3 ceramics modified by BiYO3

In this study, the structural properties, phase transition, relaxor behavior, and strain properties of (1−x)BaTiO3‒xBiYO3 (x= 0.02‒0.15 mol) ceramics were investigated. The room temperature x-ray diffraction and Raman spectroscopy results reveal that (1−x)BaTiO3‒xBiYO3 ceramics undergo phase transition from tetragonal to pseudo-cubic structure with x increasing. The curves of dielectric constant and loss tangent as a function of temperature and frequency show that the dielectric constant was changing from being dependent on temperature to being independent of it upon increasing BiYO3 amount, which is induced obvious dielectric relaxation behavior. Slimmer polarization–electric field (P–E) loops and lower remnant polarization (Pr ) were observed for samples with x ⩾ 0.08. The transition between the ferroelectric and relaxor states leads to the narrow strain–electric field (S–E) loops, which exhibit a high electric field-induced strain of 0.192% and an ultra-low strain hysteresis of 10.4% at an electric field of 70 kV cm−1 for x= 0.04. This excellent performance indicates that 0.96BaTiO3‒0.04BiYO3 ceramic may be promising lead-free materials for high-precision displacement actuators applications.

Frequency Shift in Microwave Circuits Manufactured with Circuit Board Plotters: Case Study of a Parallel Coupled Lines Filter

Board milling is one of the most widespread methods for manufacturing printed circuit boards from low frequencies to the microwave and millimeter wave range. In this contribution, the detrimental effect of defects typical of printed circuit board plotters has been investigated. In detail, a systematic frequency shift in the circuit performance has been observed both in terms of S21 and S11 parameters. The performance degradation has been analyzed and attributed to the inaccurate milling depth, which is typical of many plotters, particularly for less recent models. After the conductor removal step, the unwanted milling of dielectric material changes the electrical properties of the microstrip structure, in turn affecting the circuit performance. This circumstance has been investigated by means of electromagnetic simulations performed on the real case study of a parallel coupled lines filter. Therefore, a filter prototype has been realized and measured to confirm the simulated results. This study can be beneficial to those professionals involved in the design and realization of microwave and millimeter waves circuits with board milling machines.

A neural basis for learning sequential memory in brain loop structures

IntroductionBehaviors often involve a sequence of events, and learning and reproducing it is essential for sequential memory. Brain loop structures refer to loop-shaped inter-regional connection structures in the brain such as cortico-basal ganglia-thalamic and cortico-cerebellar loops. They are thought to play a crucial role in supporting sequential memory, but it is unclear what properties of the loop structure are important and why.MethodsIn this study, we investigated conditions necessary for the learning of sequential memory in brain loop structures via computational modeling. We assumed that sequential memory emerges due to delayed information transmission in loop structures and presented a basic neural activity model and validated our theoretical considerations with spiking neural network simulations.ResultsBased on this model, we described the factors for the learning of sequential memory: first, the information transmission delay should decrease as the size of the loop structure increases; and second, the likelihood of the learning of sequential memory increases as the size of the loop structure increases and soon saturates. Combining these factors, we showed that moderate-sized brain loop structures are advantageous for the learning of sequential memory due to the physiological restrictions of information transmission delay.DiscussionOur results will help us better understand the relationship between sequential memory and brain loop structures.

Investigating magnetic properties and Curie temperatures of FeX2 (X=S, Se, Te) Monolayers

Abstract In recent years, there has been a growing interest in two-dimensional magnetic materials. With their unique properties and tunable characteristics, magnetic monolayers hold significant potential for the next-generation devices. This study employs the first principles calculations to examine the electronic, structure, and magnetic properties of the hexagonal and trigonal FeX2 (X=S, Se, Te) monolayers. The calculations show that only two configurations found dynamically stable which are hexagonal FeS2 and FeTe2. Both H-FeS2 and H-FeTe2 monolayers exhibit metallic behavior in PBE calculations. Furthermore, the results indicate that these monolayers also exhibit ferromagnetic behavior. This ferromagnetic ordering suggests significant interactions between the magnetic moments. The magnetic exchange constants are determined by using 2D Ising model. After determining the magnetic exchange constants, a Monte Carlo simulation is performed to obtain the Curie temperature. Furthermore, the influence of the Hubbard U parameter on the electronic and magnetic structure was also examined, revealing significant modifications in the band structure and magnetic moments. Additionally, magnetic exchange constants were calculated for the PBE+U case, as well as using the TB2J method, to provide a comprehensive understanding of the magnetic properties of the stable structures.

Pectin and Alginate Functional Biopolymers: Factors Influencing Structural Composition, Functional Characteristics and Biofilm Development

Various natural polymers have been explored for their specific and desirable functional properties. Biopolymers have been found to hold the potential to satisfy many current environmental and health needs from a natural food packaging perspective. With a drive towards a more sustainable and plastic-free future, polymers like pectin and alginate have been considered key to reducing traditional plastic packaging usage in the food industry. These well-established, commercially available biopolymers display unique functional properties that can be manipulated in the development of biofilms that possess specific physical–mechanical properties. Pectin and alginate have also proven successful in the biomedical applications of encapsulation, drug delivery, wound healing and tissue engineering, greatly due to their ability to form biofilms and coatings. The structural and consequent functional properties of pectin and alginate have been investigated, although rarely concurrently with one another, focusing on biofilm development. Research has specifically identified and highlighted the importance of pectin and alginate in developing biofilms due to their versatile and charged structural nature. This review article discusses and highlights factors responsible for the specific properties displayed by pectin and alginate biofilms from a chemical and film development perspective.

Green valorization approach of Citrus limetta peels by ultrasound-assisted enzymatic extraction for recovery of dietary fibers: Optimization, physicochemical, structural, functional, and thermal properties

Green valorization approach of Citrus limetta peels by ultrasound-assisted enzymatic extraction for recovery of dietary fibers: Optimization, physicochemical, structural, functional, and thermal properties

The effect of NiO on the structural and optical properties of lithium strontium borate glasses

The effect of NiO on the structural and optical properties of lithium strontium borate glasses

Study of Structural, Electronic, Optical, Mechanical, and Thermodynamic Properties of Perovskite RbX2Ta3O10 (X = Ca and Mg) Materials for Photocatalytic Applications: A DFT Insights

Study of Structural, Electronic, Optical, Mechanical, and Thermodynamic Properties of Perovskite RbX2Ta3O10 (X = Ca and Mg) Materials for Photocatalytic Applications: A DFT Insights

Six-Coordinated CoII Single-Molecule Magnets: Synthetic Strategy, Structure and Magnetic Properties.

The pursuit of molecule-based magnetic memory materials contributes significantly to high-density information storage research in the frame of the ongoing information technologies revolution. Remarkable progress has been achieved in both transition metal (TM) and lanthanide based single-molecule magnets (SMMs). Notably, six-coordinated CoII SMMs hold particular research significance owing to the economic and abundant nature of 3d TM ions compared to lanthanide ions, the substantial spin-orbit coupling of CoII ions, the potential for precise control over coordination geometry, and the air-stability of coordination-saturated structures. In this review, we will summarize the progress made in six-coordinated CoII SMMs, organized by their coordination geometry and molecular structure similarity. Valuable insights, principles, and new mechanism gleaned from this research and remaining issues that need to be addressed will also be discussed to guide future optimization.

Strain Engineering on the Electronic Structure and Optical Properties of Monolayer WSi2X4 (X = N, P, As)

Strain Engineering on the Electronic Structure and Optical Properties of Monolayer WSi2X4 (X = N, P, As)

Systematic Investigation of Structural, Morphological and Optical Properties of Fe Doped ZnO Nanorods and Its Nanocomposite with Graphite Oxide

Systematic Investigation of Structural, Morphological and Optical Properties of Fe Doped ZnO Nanorods and Its Nanocomposite with Graphite Oxide

Mechanical–thermal coupling in micro-nanocavity graphene/paraffin phase change energy storage materials for heat management

Combining the superior thermal conductivity of graphene and the outstanding heat storage of paraffin, micro-nanocavity graphene/paraffin nanocomposites (MNGPNs) have recently served as promising thermal management materials in high-power microelectronic devices. However, current evaluations of the thermal management performances of MNGPNs are restricted in the lab condition, deviating from the complex mechanical–thermal coupling environment in practical scenarios. Here, we have investigated the structural and thermal management properties of MNGPNs with varying mechanical loads by in situ electron microscopy and in situ thermal characterizations. Our results reveal distinct mechanical–thermal coupling effects along in-plane and out-of-plane directions of MNGPNs. Specifically, mechanical loading reduces the porosity and enhances the heat transfer capacity of MNGPNs in the out-of-plane direction, while mechanical loading along the in-plane direction causes local damage to the graphene structure and weakens the heat transfer capacity of MNGPNs. Since the heat management performance of MNGPNs is dominated by the in-plane thermal transport, MNGPNs with mechanical loading show a delayed phase transition response time and unchanged phase transition enthalpy. This work provides in situ mechanical guidance for the practical application of MNGPNs for heat management.

Synthesis and characterization of enhanced azo-azomethine doped PANI/HCl conducting polymers for electrochemical applications

In this study, conducting polymers composed of polyaniline hydrochloric acid (PANI/HCl) with varying concentrations of a newly synthesized azo-azomethine dye (4-(((Z)-2-hydroxy-5-((Z)-(4-hydroxyphenyl)diazenyl)-3-methoxybenzylidene)amino)benzoic acid) were synthesized using a chemical oxidative polymerization technique. The synthesized azo-azomethine was characterized by FTIR, 1H-NMR, 13C-NMR, and HRMS. The effects of varying the concentration of the dopant azo-azomethine in PANI/HCl on its optical, structural, thermal, and electrical properties were examined using FTIR, UV–Vis, XRD, FESEM, TEM, cyclic voltammetry, and electrical impedance spectra. The results indicate that the optical, direct, and indirect band gaps of the doped polymers decreased from 4.48 and 3.96 eV to 3.91 and 2.49 eV, respectively. The crystalline structure and phase transitions in the doped polymers were examined using X-ray diffraction. Cyclic voltammetry demonstrated that the doped polymers exhibited higher electrochemical conductivity compared to the pure polymer, with the specific capacitance increasing from 161.17 to 816.9 F/g. The electrical impedance spectra revealed the bulk resistance and conductivity of the material. Among all the doped polymers, PANI/HCl with an azo-azomethine concentration of 5 × 10−5 M exhibited lower bulk resistance (10 Ω) and higher electrical conductivity (σ = 50.09 × 10−3 S cm−1).

High-Speed Self-Powered PdSe2/Si 2D-3D PIN-like Photodetector with Broadband Response Based on PdSe2 Quantum Island Structure.

As a two-dimensional (2D) material, palladium diselenide (PdSe2) has attracted extensive research attention due to its unique asymmetric crystal structure and extraordinary optoelectronic properties, showing great potential in electronic, optoelectronic, and other application fields. Thinner PdSe2 exhibits semiconductor properties, while the photoresponse of the photodetectors based on this film is weaker. Although increasing the thickness of the PdSe2 film can improve the photoresponse, thicker PdSe2 exhibits metallic-like properties, which is not conducive to the formation of the heterojunction. In this work, a PdSe2 2D material with a quantum island structure is prepared by a simple thermal-assisted conversion method. A new type of photodetector with a PdSe2/n--Si/n+-Si vertical PIN-like structure is innovatively proposed. Broad spectral absorption from 532 to 2200 nm and a high rectification ratio (106) of the device are achieved. The introduced n--Si layer concentrates the electric field in the depletion region, thereby shortening the transit time and accelerating the separation and collection of the carriers, resulting in the enhancement of the responsivity and 3 dB frequency compared to the traditional device with a PN structure. A recorded highest 3 dB frequency of ∼25 kHz is achieved for the PdSe2 2D-3D PIN-like device.