Bulk Ones Research Articles

Reinforcement of nanostructured polyacrylamide hydrogels through the generation of secondary physical network using the nanoparticles’ functional groups

The main drawback regarding hydrogels utilization in biomedical engineering is represented by their weak mechanical properties and it is often addressed either by using nanospecies as fillers or by generating secondary networks that strengthen the material. Our study validates a new synthesis route of obtaining double-network nanostructured materials making use of the functional groups of an adsorbed glyco-protein on carbon-based nanospecies. Following a simple procedure, the decorated nanospecies were embedded in a synthetic polymer and subsequently formed a secondary hydrogen-bond based network through incubation in natural polyphenol solutions of various concentrations. The natural macromolecule's adsorption was evaluated through FTIR and DLS measurements. When compared to the single-network nanostructured materials, the double-network hydrogels exhibited lower affinity to aqueous media and improved ability to dissipate energy upon mechanical stress, depending on the amount of the employed natural crosslinker. As a result of generating the second network through incubation in polyphenol aqueous solution, the surface storage and loss moduli exceed the values of the bulk ones, as indicated by rheology and nanoindentation tests. The properties of the double-network hydrogels can also be tailored towards more hydrophilic surfaces with increased roughness through the control of the supplementary crosslinker amount. Considering the studied physical-chemical properties, and especially their mechanical characteristics, the obtained materials hold great promise for biomedical applications, particularly for the fabrication of scaffolds for wound dressing, soft or low load bearing tissue regeneration and repair.

Efficient photocatalytic degradation of textile dye pollutants using thermally exfoliated graphitic carbon nitride (TE–g–C3N4)

Graphitic carbon nitride (g–C3N4), an organic photocatalyst was reported to have beneficial properties to be used in wastewater treatment applications. However, g–C3N4, in its bulk form was found to have poor photocatalytic degradation efficiency due to its inherent limitations such as poor specific surface area and fast electron–hole pair recombination rate. In this study, we have tuned the physiochemical properties of bulk g–C3N4 by direct thermal exfoliation (TE–g–C3N4) and examined their photocatalytic degradation efficiency against abundant textile dyes such as methylene blue (MB), methyl orange (MO), and rhodamine B (RhB). The degradation efficiencies for MB, MO, and RhB dyes are 92 ± 0.18%, 93 ± 0.31%, and 95 ± 0.4% respectively in 60 min of UV light irradiation. The degradation efficiency increased with an increase in the exfoliation temperature. The prepared catalysts were characterized using FTIR, XRD, FE-SEM, EDAX, BET, and UV-DRS. In BET analysis, TE–g–C3N4 samples showed improved surface area (48.20 m2/g) when compared to the bulk g–C3N4 (5.03 m2/g). Further, the TE–g–C3N4 had 2.98 times higher adsorption efficiency than the bulk ones. The free radicals scavenging studies revealed that the superoxide radicals played an important role in the photodegradation for dyes, when compared to the hydroxyl radical (.OH) and the photo-induced holes (h+), Photoluminescence (PL) emission and electrochemical impedance spectroscopy (EIS) spectra of TE–g–C3N4 indicated a lowered electron–hole pairs’ recombination rate and an increased photo-induced charge transfer respectively. Further, the TE–g–C3N4 were found to have excellent stability for up to 5 cycles with only a minor decrease in the activity from 92% to 86.2%. These findings proved that TE–g–C3N4 was an excellent photocatalyst for the removal and degradation of textile dyes from wastewater.

Ultrasmall Ce-based metal–organic frameworks nanozyme with hydrolytic activity for boosting antibiofilm therapy

Biofilms adhering to device surfaces impose great threat to public health and industries. Metal-organic frameworks (MOFs) replicating the functionalities of natural enzymes are highly promising for combating biofilms, however still challenged by the intrinsic inferior catalytic activity. Herein, a simple and facile strategy is demonstrated to fabricate ultrasmall Ce-MOFs in an aqueous solution at ambient temperature to achieve high hydrolytic activity under mild conditions. Benefiting from the biomimetic structure and the ultrasmall size, Ce-MOFs nanozyme exhibited remarkable hydrolytic catalytic activities for cleaving the phosphate bonds, glycosidic bonds and their mixtures, the biofilm, showing satisfactory performance in biofilm prevention and eradication. Catalytic mechanism investigation reveals that the synergistic interaction between Ce4+ and Ce3+, the dense active site leads to 3–15 folds higher hydrolytic activity of the ultrasmall sized Ce-MOFs compared with the bulk ones. This work is expected to provide insights for rational design of nanozymes and holds great promise for environmental remediation.

Electrophysical properties, memristive and resistive switching of charged domain walls in lithium niobate

Charged domain walls (CDWs) in ferroelectric materials raise both fundamental and practical interest due to their electrophysical properties differing from bulk ones. On a microstructure level, CDWs in ferroelectrics are 2D defects separating regions with different spontaneous polarization vector directions. Screening of electric field of the CDW's bound ionic charges by mobile carriers leads to the formation of elongated narrow channels with an elevated conductivity in initially dielectric materials. Controlling the position and inclination angle of CDW relative to the spontaneous polarization direction, one can change its conductivity over a wide range thus providing good opportunities for developing memory devices, including neuromorphic systems. This review describes the state of art in the formation and application of CDWs in single crystal uniaxial ferroelectric lithium niobate (LiNbO3, LN), as resistive and memristive switching devices. The main CDWs formation methods in single crystal and thin-film LN have been described, and modern data have been presented on the electrophysical properties and electrical conductivity control methods of CDWs. Prospects of CDWs application in resistive and memristive switching memory devices have been discussed.

Plasma Immersion Ion Implantation of a Fe-Mn-C Based Steel for Biomedical Applications: Effect of Gases and Treatment Times on the Surface Properties

Current research on biodegradable iron-based alloys mainly focuses at regulating the material degradation rate, as well as its biological behavior, especially from the point of view of the hemocompatibility and cytocompatibility. In fact, fine-tuning of the surface roughness, morphology and chemical composition can improve the functional response of the material. For that purpose, a surface modification strategy, namely plasma immersion ion implantation (PIII), is proposed to perform the selective modification of surface properties without affecting the bulk ones. In this work, the influence of treatment time (timp = 15, 60 and 120 min.) and implanted species (O, N or C) on the surface properties of a Fe-13Mn-1.2C resorbable alloy was investigated. The findings demonstrated that varying the process gas and the exposition time led to a variety of topographies, surface energies and chemical compositions. XPS analyses and depth profiles clearly showed the impact of the process parameters on the surface features and element distribution, due to implanted species penetration into the alloy. The implanted samples showed a delayed clotting time, thus a better hemocompatibility. In contrast, nitrogen-treated surfaces displayed a more pronounced hemolytic behavior, whereas oxygen and methane did not. PIII implantation appears to be a versatile solution for fine-tuning surface topography, composition and biological properties, making the process promising for the improvement of metallic biodegradable vascular implants.

Electrophysical properties, memristive and resistive switching in charged domain walls in lithium niobate

Charged domain walls (CDW) in ferroelectric materials are interesting from fundamental and applied points of view, since they have electrical properties different from bulk ones. At the microstructural level, CDW in ferroelectrics are two-dimensional defects that separate regions of the material with different directions of spontaneous polarization vectors. Compensation of the electric field of the bound ionic charge of the CDW by mobile carriers leads to the formation of extended narrow channels with increased conductivity in the original dielectric material. By controlling the position and angle of inclination of the CDW relative to the direction of spontaneous polarization, it is possible to change its conductivity in a wide range, which opens up broad prospects for creating memory devices, including for neuromorphic systems. The review presents the current state of research in the field of formation and application of CDW formed in single crystals of uniaxial ferroelectric lithium niobate (LiNbO3, LN) as resistive and memristive switching devices. The main methods for forming CDW in single crystals and thin films of LN are considered, and modern data on the electrophysical properties and methods for controlling the electrical conductivity of CDW are presented. The prospects for using CDW in memory devices with resistive and memristive switching are discussed.

Коллективная природа низкотемпературных фотопроводимости и проводимости в Пайерлсовском проводнике ромбическом TаS3

This work summarizes the results of series of works devoted to the study of the mechanisms of low-temperature conduction and photoconduction in the Peierls conductor orthorhombic TaS3 (o-TaS3). We used the tools we discovered to change the relationship between the single-particle and collective components of low-temperature photoconduction and conduction in o-TaS3 – illumination and uniaxial stretching of the sample. Using them, we were able to separate single-particle and collective contributions and show that the collective contribution dominates both low-temperature conduction (T ≲ 100 K) and low-temperature photoconduction (T ≲ 45 K). In addition, the discovered analogy between the influence of illumination and stretching on low-temperature conduction and photoconduction made it possible to establish the dimension of charge density wave (CDW) pinning in samples of different cross-sections at low temperatures. It was found that for all samples, including bulk ones, one-dimensional pinning is observed at temperatures T < 40 K, and it also has a collective character.

LucFlow: A method to measure Luciferase reporter expression in single cells.

Reporter assays, in which the expression of an inert protein is driven by gene regulatory elements such as promoters and enhancers, are a workhorse for investigating gene regulation. Techniques for measuring reporter gene expression vary from single-cell or single-molecule approaches having low throughput to bulk Luciferase assays that have high throughput. We developed a Luciferase Reporter Assay using Flow-Cytometry (LucFlow), which measures reporter expression in single cells immunostained for Luciferase. We optimized and tested LucFlow with a murine cell line that can be differentiated into neutrophils, into which promoter-reporter and enhancer-promoter-reporter constructs have been integrated in a site-specific manner. The single-cell measurements are comparable to bulk ones but we found that dead cells have no detectable Luciferase protein, so that bulk assays underestimate reporter expression. LucFlow is able to achieve a higher accuracy than bulk methods by excluding dead cells during flow cytometry. Prior to fixation and staining, the samples are spiked with stained cells that can be discriminated during flow cytometry and control for tube-to-tube variation in experimental conditions. Computing fold change relative to control cells allows LucFlow to achieve a high level of precision. LucFlow, therefore, enables the accurate and precise measurement of reporter expression in a high throughput manner.

Correlated EPR and optical study of charge trapping phenomena in tellurite glasses. The role of barium oxide

Tellurite glasses of the compositions TeO2(60%)-ZnO(40%) and TeO2(60%)-ZnO(20%)-BaO(20%) were prepared in the bulk form with following grinding into powders. The samples were X-ray irradiated. The created charge trapping centers were studied in both types of samples using electron paramagnetic resonance (EPR) spectroscopy. The O− defect and two types of F+ centers were discovered. One of the F+ center remained unchanged whereas the other one as well as the O− defect were affected by the presence of BaO. Moreover, photo-, radio- and thermoluminescence (PL, RL, TL, respectively) methods were applied as well. The discovered charge trapping centers have been proven to influence luminescence properties as well – improving them in the TeO2(60%)-ZnO(40%) and vice versa degrading them in the TeO2(60%)-ZnO(20%)-BaO(20%) glasses. The effect was even stronger in the grinded samples as compared to the bulk ones. The role of the BaO has been disclosed as supporting oxygen leakage from the host.

Adsorption and desorption of polychlorinated biphenyls on biochar colloids with different pyrolysis temperatures: the effect of solution chemistry.

Biochar releases colloidal particles into the environment during applications and aging which can become carriers of pollutants and influence on the environmental risk of pollutants due to the excellent adsorption and migration properties of biochar colloids (BCCs). The adsorption and desorption behaviors of BCCs can be different from their bulk ones due to the colloidal size, which merits specific studies. Herein, the adsorption and desorption of 2,4,4'-trichlorobiphenyl (PCB28) as a representative on BCCs released from bulk biochars prepared from bamboo chips at 300, 500, and 700C and the effects of solution properties were specifically investigated. Results show that the adsorption was dominated by pore filling and π-π interaction, and thus, BCCs prepared at higher temperature with greater pore volume and aromaticity had higher adsorption of PCB28. Results show that the adsorption was dominated by pore filling and π-π interaction, and thus, BCCs prepared at higher temperature with greater pore volume and aromaticity had higher adsorption of PCB28. The saturation adsorption amounts of PCB28 on BCC300, BCC500, and BCC700 were 21.9, 40.3, and 62.4mg/g, respectively. It is noteworthy that PCB28 possessed a significant desorption hysteresis from BCCs, with the hysteresis index (Ce = 80μg/L) increased from 0.380 to 0.661 as the preparation temperature of BCCs rising from 300 to 700℃. High concentration of NaCl (100mmol/L) was unfavorable for the adsorption and desorption. The presence of humic acid or fulvic acid (FA), especially the smaller FA, could inhibit the adsorption and desorption of PCB28 on BCCs due to micropore blocking. In seawater, groundwater, surface water, and soil solution samples, the PCB28 adsorption of BCCs was inhibited to varying degrees in comparison with that in deionized water, and the desorption was noticeably inhibited in the groundwater sample. These findings provide valuable information for the understanding of interactions between BCCs and organic contaminants in natural waters and for the environmental application of biochars as well.

A Universal Synthesis Strategy for Lanthanide Sulfide Nanocrystals with Efficient Photocatalytic Hydrogen Production.

As an important lanthanide (Ln)-based functional materials, the Ln chalcogenides possess unique properties and various applications. However, the controllable synthesis of Ln chalcogenide nanocrystals still faces great challenges because of the rather poor affinity between Ln and chalcogenide ions (S, Se, Te) as well as strong preference of combination with existed oxygen. Herein, a facile but general heterogeneous nucleation synthetic strategy is established toward a series of colloidal ternary Cu Ln sulfides nanocrystals using the Ln dithiocarbamates and CuIas precursors. To extend this synthetic protocol, similar strategy is used to prepare six kinds of high quality CuLnS2 nanocrystals, while the bulk ones are only obtained by the traditional solid-state reaction at rigorous condition. Importantly, high-entropy nanocrystals CuLnS2 and CuEux Ln2-x S3 which contain six Lnelements (Nd, Sm, Gd, Tb, Dy) are readily obtained by the co-decomposed process attributed to their similar diffusion speed. As a proof-of-concept application, CuEu2 S3 nanocrystals showed efficient photocatalytic hydrogen production properties.

The role of selenium and nano selenium on physiological responses in plant: a review.

Selenium (Se), being an essential micronutrient, enhances plant growth and development in trace amounts. It also protects plants against different abiotic stresses by acting as an antioxidant or stimulator in a dose-dependent manner. Knowledge of Se uptake, translocation, and accumulation is crucial to achieving the inclusive benefits of Se in plants. Therefore, this review discusses the absorption, translocation, and signaling of Se in plants as well as proteomic and genomic investigations of Se shortage and toxicity. Furthermore, the physiological responses to Se in plants and its ability to mitigate abiotic stress have been included. In this golden age of nanotechnology, scientists are interested in nanostructured materials due to their advantages over bulk ones. Thus, the synthesis of nano-Se or Se nanoparticles (SeNP) and its impact on plants have been studied, highlighting the essential functions of Se NP in plant physiology. In this review, we survey the research literature from the perspective of the role of Se in plant metabolism. We also highlight the outstanding aspects of Se NP that enlighten the knowledge and importance of Se in the plant system.

A series of crumpled ball-like metal oxide-based catalysts enabled by aerosol synthesis

Two-dimensional nano metal oxides (2D-NMOs) have attracted great concerns due to high exposure of active sites and short ion transport distance. However, 2D-NMOs with the layered structure render to restack into bulk ones, resulting in the active-sites coverage and ion-transport blockage. Here, crumpled 2D NMOs with paper-ball-like shape was proposed to avoid the restacking. Our new strategy can convert diversity of metal oxide into paper-ball-like structure with controllable composition by overcoming the fragile nature of metal oxide and limitation of growth pattern. Resultantly, as-prepared 2D NMOs demonstrated superior catalytic activity and durability in both oxygen evolution reaction (OER) and organic dye degradation reaction, owing to their high exposure of active sites and low ionic diffusion resistance.

Identification of the spectral complex refractive index of pure silica micrometric fibers versus temperature

A new methodology was developed to identify the spectral complex refractive index of semi-transparent solid phases within heterogeneous media up to high temperatures. In this methodology, numerical samples are first generated from statistical information about the microstructure of a given material obtained by X-ray micro-tomography. The radiative properties of these numerical samples (reflectance, transmittance, and emittance) are then simulated with a Geometric Monte Carlo Ray Tracing code while the radiative properties of the real material are measured by Fourier Transform Infrared spectroscopy. The spectral complex refractive index is then extracted thanks to an optimization algorithm, by minimizing the discrepancies between the experimental and numerical radiative properties. This methodology was applied to a fibrous sample made of pure silica. The complex index was extracted at 295 K and 1010 K. In both cases, it enabled a good prediction of the radiative properties of the material and proved the relevance of performing calculations with characteristics identified at the local scale instead of the bulk ones.

Synthesis and structural characterization of new group 12 metal ions coordination polymers built on sulfur‐based ligand and probing their high iodine adsorption efficiency in micro and bulk forms

In this work, we have prepared two new sulfur CPs with group 12 transition metals, namely,[Zn (NCS)Cl(μ2‐L)]n(1)and[Hg (SCN)2(μ2‐L)]n(3).[Cd (NCS)Cl(μ2‐L)]n(2), which is isostructural with1, was synthesized for a comparison from our published work. These compounds have been characterized by FT‐IR, UV–Vis, powder X‐ray diffraction (PXRD), elemental analysis (CHNS), scanning electron microscopy (Fe‐SEM), TGA, BET, and single‐crystal X‐ray analysis for1and3. In the structure of all polymers, the bbit ligand [L = bbit = 1,1‐bis(3‐methyl‐4‐imidazoline‐2‐thion)butane] is bridged between metal centers by the anti‐anti‐anti conformation to form an infinite 1D zigzag chain. The considered polymers were used for the removal of a substantial amount of I2from cyclohexane solution. Despite the nonporous and low dimensional frameworks of title polymers, their maximum iodine adsorption capacities were notable and in order of 817.68, 906.48, and 911.08 mg/g for polymers1–3, respectively, with an extraordinary stability toward iodine. The capacity of micro‐sized structures was almost double as compared with their bulk ones.

Parity‐Time Phase Transition of Topological Corner States in Square Lattice Photonic Crystal Structures

Marriage of the concepts of parity‐time (PT) symmetry and topology recently gave rise to PT‐symmetric topological photonics, triggering great interest in the community of photonics. This work reveals PT‐symmetric phase transition in second‐order topological photonic systems: the photonic systems consisting of square lattice topological photonic crystals with balanced gain and loss support the corner states, two of which are in thresholdless PT broken phase and the other two exhibit PT phase transition with a threshold determined by the coupling strength between the corner modes. The main advantage of the proposed photonic system is the significantly high gain contrast between the corner states and unnecessary background modes originating from bulk and edge ones, enabling diverse photonic applications such as nanolasing with significantly high power compared with the preceding topological nanolasers made of only gain sublattices. The results presented in this work pave the way toward potential applications such as biological sensing and spectroscopy at the nanoscale.

Metamorphosis of the properties of the gas-phase fraction of ZnS:Mn obtained by the method of self-propagating high-temperature synthesis from the charge with a different Zn/S ratio

Performed in this work is a comparative analysis of photoluminescence, photoluminescence excitation and EPR spectra of gas-phase fraction of powdery ZnS:Mn obtained using the self-propagating high-temperature synthesis from the charge with a different Zn/S ratio. It was found that the size of particles in the synthesized materials was with in the range 10–300 nm. The size that is comparable with the Debye screening length (L). The luminescence and other characteristics of the studied material were found to differ significantly from the bulk ones. This finding has been explained by a unique energy structure of crystallites. Zn/S ratio has been shown to impact significantly on the crystallites sizes and the amount of incorporated Mn. The largest crystallite sizes and the high Mn content were observed in the powder synthesized with a stoichiometric Zn/S ratio, while the minimum particle sizes - in the powders synthesized with S excess. At sulfur excess, the size of particles is close to the Debye length, and carriers can freely migrate in the conduction band to the surface, where mainly nonradiative recombination occurs. The stoichiometric Zn/S ratio or Zn excess in the charge results in the increase of the particle sizes up to the values 2L ≤ d≤3L. Such materials are characterized by minimization of non-radiative losses. This finding opens new possibilities for ZnS application.

Multilayered Sb-Rich GeSbTe Phase-Change Memory for Best Endurance and Reduced Variability

Sb-rich GeSbTe-based phase-change memories (PCMs) were studied in the past years for their high switching speed to target storage class memory (SCM) applications. In this work, we show the advantages of an engineered multilayered Sb-rich GeSbTe stack compared with standard bulk reference materials. The studied multilayer-based PCM devices feature a lower programming current with respect to the equivalent bulk ones, preserving a high programming speed. Furthermore, multilayered Sb-rich GeSbTe brings better endurance performances for a wide programming current range and extremely reduced cycle-to-cycle (C2C) and device-to-device (D2D) variability along cycling verified in 4 kb PCM arrays. These results confirm improved yield and reliability obtained, thanks to multilayered PCM solution.

Synthesis of Titanium Oxide Nanotubes for Photo Electrochemical Cells and its Characterizations

Nano scale materials have many peculiar properties than the bulk ones and have led to break through in various fields of science and technology. Titanium oxide is one of the excellent and most demanded materials because of its various applications and properties such as such as large surface area. In this paper, Titanium oxide (TiO2) nanotube arrays were synthesized by electrochemical anodization of titanium foil. Dimension of nanotubes and elemental composition were detected by Field Emission-Scanning Electron Microscope with Energy Dispersive X-Ray Analysis (FESEM- EDAX). From X- Ray Diffraction (XRD) the intensity of peaks, d- spacing values and phase of TiO2 nanotubes were analyzed. The Energy Bandgap (Eg) of the formed TiO2 nanotubes was determined by Diffuse Reflectance Spectroscopy from Kubelka-Monk Plot. From the obtained results, the synthesized TiO2 nanotubes are suitable for Photo Electrochemical Cell applications.

Topological synchronization of coupled nonlinear oscillators

Synchronization of coupled oscillators is a ubiquitous phenomenon found throughout nature. Its robust realization is crucial to our understanding of various nonlinear systems, ranging from biological functions to electrical engineering. On another front, in condensed matter physics, topology is utilized to realize robust properties like topological edge modes, as demonstrated by celebrated topological insulators. Here, we integrate these two research avenues and propose a nonlinear topological phenomenon, namely topological synchronization, where only the edge oscillators synchronize while the bulk ones exhibit chaotic dynamics. We analyze concrete prototypical models to demonstrate the presence of positive Lyapunov exponents and Lyapunov vectors localized along the edge. As a unique characteristic of topology in nonlinear systems, we find that unconventional extra topological boundary modes appear at emerging effective boundaries. Furthermore, our proposal shows promise for spatially controlling synchronization, such as on-demand pattern designing and defect detection. The topological synchronization can ubiquitously appear in topological nonlinear oscillators and thus can provide a guiding principle to realize synchronization in a robust, geometrical, and flexible way.