Formation Of Spherical Particles Research Articles

Effect of cyclic oxidation temperature on compressive strength of Cu-based brake pad for high-speed train

The cyclic oxidation tests of Cu-based brake pads at temperatures of 25, 300, 400, 500, 550, 600, 650 and 700 °C were conducted to simulate the oxidation of the friction surface under different braking speeds. Furthermore, the effect of cyclic oxidation temperature on the compressive strength was investigated. The results show that the cyclic oxidation process of Cu-based brake pads can be divided into three stages: mild oxidation (≤400 °C), moderate oxidation (500–600 °C) and severe oxidation (≥650 °C). Mild oxidation results in the formation of spherical Cu2O particles. The surface is covered by Cu2O and Fe2O3 nanosheets for moderate oxidation. Severe oxidation is characterized by a continuous thick CuO film, Fe2O3 nanosheets, and eroded graphite particles. The compressive strength and toughness of Cu-based brake pads show a declining trend as the cyclic oxidation temperature rises. The compressive strength of the Cu-based brake pad after oxidized at 700 °C, recorded at 30.56 MPa, is considerably lower than that of the original samples, which was 132.2 MPa. This reduction in compressive strength is attributed to the embrittlement of the metallic matrix and the formation of pores from graphite oxidation.

Synthesis of boron-based High-Energy composite microspheres via the Co-Flow microchannel method

Boron-based metastable intermolecular composites (MIC), renowned for their swift energy release and elevated thermal output, exhibit significant promise for utilization in domains such as gunpowder, propellants, and powdered fuel ramjet fuels. The work successfully accomplished the safe and efficient preparation of B/Bi2O3 microunits by utilizing co-flow microchannel technology. The choice of the optimal binder, F2603, for this system was determined by simulation analysis. The practicality of the microchannel platform was then verified using Fluent. SEM analysis demonstrated that an amount of 10 % F2603 resulted in the formation of spherical particles. In terms of physical properties, boron treated with 10 % F2603 exhibits a reduction in its angle of repose from 35° of the raw material to 15°, along with a significant enhancement in hydrophobicity. Furthermore, the MICs lower the reaction temperature of raw boron from 840℃ to 770℃. In the constant volume combustion test, the MIC output pressure increased by 33.3 %. In the constant pressure combustion test, the MIC ignition delay time was reduced from 0.7262 s to 0.5566 s. The structural characteristics of the system decrease the distance for mass and heat transmission across components, resulting in improved overall performance. The study unequivocally demonstrates the efficacy of co-flow microchannel technology in swiftly, effectively, and securely producing energetic molecules. It establishes a solid foundation for future industrial manufacturing.

Elaboration of chitosan nanoparticles loaded with star anise extract as a therapeutic system for lung cancer: Physicochemical and biological evaluation

The research study aimed to maximize the important medical role of star anise extract (SAE) through its loading on a widely available natural polymer (chitosan, Cs). The preparation of SAE loaded CsNPs was performed using an ionic gelation process. The finding illustrated the formation of spherical particles of SAE loaded CsNPs as proved by transmission electron microscope (TEM). In addition, the average particle size of CsNPs and SAE loaded CsNPs are 131.8 ± 24.63 and 318.5 ± 73.94 nm, respectively. Scanning electron microscope (SEM) showed the presence of a density of many spherical particles deposited on the surface of CsNPs owing to the presence of SAE carried onto the surface and in the same time, encapsulated into pores of CsNPs. It also showed the presence of elements such as sodium, potassium, copper, magnesium, zinc, calcium, and iron, as well as the elements found in CsNPs: carbon, oxygen, nitrogen, and phosphorus. The extract was rich in bioactive components, such as anethole, shikimic acid, and different flavonoids, contributing to its medicinal qualities. The bioactive molecules in SAE were assessed by chromatographic analysis. Using the agar well diffusion test, the antibacterial qualities of CsNPs and SAE loaded CsNPs were assessed against pathogenic bacteria linked to lung illnesses. The most significant inhibition zones showed that the SAE loaded CsNPs had the most antibacterial activity. The anticancer activity using MTT assay was used in the biological assessments to determine the cytotoxicity against the NCl-H460 lung cancer cell line. The results showed that CsNPs loaded with SAE considerably decreased cell viability in a dose-dependent manner, with the most significant anticancer impact by SAE loaded CsNPs Furthermore, in vivo tests on lung cancer therapy revealed that when compared to other treatment groups, the SAE loaded CsNPs group showed the greatest reduction in tumor biomarkers and inflammation, as seen by decreased levels of Plasma malondialdehyde (MDA), tumor protein 53 (p53), Tumor necrosis factor-alpha (TNF- alpha), and fibronectin. Results concluded that these thorough characterizations, biological assessments, and antibacterial tests have confirmed the effective integration of SAE into CsNPs. Further, SAE loaded CsNPs could be a suitable option for various biomedical applications in tackling lung cancer and the inactivation of bacterial infection.

Poly(Lactic-Co-Glycolic Acid) Microparticles for the Delivery of Model Drug Compounds for Applications in Vascular Tissue Engineering.

Localized delivery of angiogenesis-promoting factors such as small molecules, nucleic acids, peptides, and proteins to promote the repair and regeneration of damaged tissues remains a challenge in vascular tissue engineering. Current delivery methods such as direct administration of therapeutics can fail to maintain the necessary sustained release profile and often rely on supraphysiologic doses to achieve the desired therapeutic effect. By implementing a microparticle delivery system, localized delivery can be coupled with sustained and controlled release to mitigate the risks involved with the high dosages currently required from direct therapeutic administration. For this purpose, poly(lactic-co-glycolic acid) (PLGA) microparticles were fabricated via anti-solvent microencapsulation and the loading, release, and delivery of model angiogenic molecules, specifically a small molecule, nucleic acid, and protein, were assessed in vitro using microvascular fragments (MVFs). The microencapsulation approach utilized enabled rapid spherical particle formation and encapsulation of model drugs of different sizes, all in one method. The addition of a fibrin scaffold, required for the culture of the MVFs, reduced the initial burst of model drugs observed in release profiles from PLGA alone. Lastly, in vitro studies using MVFs demonstrated that higher concentrations of microparticles led to greater co-localization of the model therapeutic (miRNA) with MVFs, which is vital for targeted delivery methods. It was also found that the biodistribution of miRNA using the delivered microparticle system was enhanced compared to direct administration. Overall, PLGA microparticles, formulated and loaded with model therapeutic compounds in one step, resulted in improved biodistribution in a model of the vasculature leading to a future in translational revascularization.

Influence of minor Mg/Ca/Nb/Ag addition on the morphology and microstructure of Fe-rich phase in powder metallurgy Cu[sbnd]10Fe alloy

The effect of Mg/Ca/Nb/Ag alloying on the morphology and microstructure of powder metallurgy Cu10Fe alloy was investigated systemically in this work. Alloying of Ca reduces the size of Fe-rich particles, while alloying of Mg/Nb/Ag increases the Fe-rich particles. This is attributed to the different roles of various alloying elements on the liquid-phase separation behaviors as well as diffusion of Fe atoms during the solidification. Coarse size spherical Fe-rich particles with a face centered cubic structure are observed in CuFe alloys bearing Mg/Ag/Nb, whilst the alloying of Ca favors the formation of fine spherical Fe-rich particles with a body centered cubic structure. The factor governing the morphology is found to be interfacial energy for CuFe alloys containing Mg/Ag/Nb and elastic energy for Cu-Fe-Ca alloy, respectively. Coarse size Fe-rich particles are hard to deform during subsequent rolling, but the fine Fe-rich particles can co-deform with Cu matrix. This study could provide a detailed picture regarding the influence of various alloying element types on the size, morphology, and lattice structure of Fe phase of CuFe alloy.

The effect of extracellular polymeric substances on MICP solidifying rare earth slags and stabilizing Th and U.

Microbially induced carbonate precipitation (MICP) has been used to cure rare earth slags (RES) containing radionuclides (e.g. Th and U) and heavy metals with favorable results. However, the role of microbial extracellular polymeric substances (EPS) in MICP curing RES remains unclear. In this study, the EPS of Lysinibacillus sphaericus K-1 was extracted for the experiments of adsorption, inducing calcium carbonate (CaCO3) precipitation and curing of RES. The role of EPS in in MICP curing RES and stabilizing radionuclides and heavy metals was analyzed by evaluating the concentration and morphological distribution of radionuclides and heavy metals, and the compressive strength of the cured body. The results indicate that the adsorption efficiencies of EPS for Th (IV), U (VI), Cu2+, Pb2+, Zn2+, and Cd2+ were 44.83%, 45.83%, 53.7%, 61.3%, 42.1%, and 77.85%, respectively. The addition of EPS solution resulted in the formation of nanoscale spherical particles on the microorganism surface, which could act as an accumulating skeleton to facilitate the formation of CaCO3. After adding 20 mL of EPS solution during the curing process (Treat group), the maximum unconfined compressive strength (UCS) of the cured body reached 1.922 MPa, which was 12.13% higher than the CK group. The contents of exchangeable Th (IV) and U (VI) in the cured bodies of the Treat group decreased by 3.35% and 4.93%, respectively, compared with the CK group. Therefore, EPS enhances the effect of MICP curing RES and reduces the potential environmental problems that may be caused by radionuclides and heavy metals during the long-term sequestration of RES.

Sol-Gel Synthesis of Silica-Poly (Vinylpyrrolidone) Hybrids with Prooxidant Activity and Antibacterial Properties.

The present work deals with the sol-gel synthesis of silica-poly (vinylpyrrolidone) hybrid materials. The nanohybrids (Si-PVP) have been prepared using an acidic catalyst at ambient temperature. Tetramethyl ortosilane (TMOS) was used as a silica precursor. Poly (vinylpyrrolidone) (PVP) was introduced into the reaction mixture as a solution in ethanol with a concentration of 20%. The XRD established that the as-prepared material is amorphous. The IR and 29Si MAS NMR spectra proved the formation of a polymerized silica network as well as the hydrogen bonding interactions between the silica matrix and OH hydrogens of the silanol groups. The TEM showed spherical particle formation along with increased agglomeration tendency. The efficacy of SiO2/PVP nanoparticles as a potential antimicrobial agent against a wide range of bacteria was evaluated as bacteriostatic, using agar diffusion and spot tests. Combined effects of hybrid nanomaterial and antibiotics could significantly reduce the bactericidal concentrations of both the antibiotic and the particles, and they could also eliminate the antibiotic resistance of the pathogen. The registered prooxidant activity of the newly synthesized material was confirmative and explicatory for the antibacterial properties of the tested substance and its synergetic combination with antibiotics. The effect of new hybrid material on Crustacea Daphnia magna was also estimated as harmless under concentration of 0.1 mg/mL.

Cryo-EM structure of orf virus scaffolding protein orfv075

Capsid-like poxvirus scaffold proteins self-assemble into semi-regular lattice that govern the formation of spherical immature virus particles. The scaffolding is a critical step in virus morphogenesis as exemplified by the drug rifampicin that impairs the recruitment of scaffold onto the viral membrane in vaccinia virus (VACV). Here we report cryo-electron microscopy structure of scaffolding protein Orfv075 of orf virus (ORFV) that causes smallpox-like diseases in sheep, goats and occasionally humans via zoonotic infection. We demonstrate that the regions that are involved in intertrimeric interactions for scaffold assembly are largely conserved in comparison to its VACV orthologue protein D13 whose intermediate assembly structures have been previously characterized. By contrast, less conserved regions are located away from these interfaces, indicating both viruses share similar assembly mechanisms. We also show that the phenylalanine-rich binding site of rifampicin in D13 is conserved in Orfv075, and molecular docking simulation confirms similar binding modes. Our study provides structural basis of scaffolding protein as a target for anti-poxvirus treatment across wide range of poxvirus genera.

Preferential formation of uniform spherical vaterite by harnessing vortex flows and integrated CO2 capture and mineralization

The use of calcium bearing resources to facilitate solvent regeneration and CO2 reuse via carbon mineralization offers a low energy pathway for the production of calcium carbonate. However, a crucial challenge is the lack of specificity in the formation of various calcium carbonate polymorphs during carbon mineralization. One of the less explored but highly effective approaches to tune the morphology and crystal structure of specific carbonate phases involves tuning vortex flows. This approach is an alternative to utilizing chemical reagents that need to be regenerated for tuning the morphologies and crystalline structures to direct the formation of specific carbonate phases. In this study, the efficacy of using homogeneous vortex flows in limiting the agglomeration of carbonate particles and directing the formation of metastable vaterite phases is discussed and contrasted with the influence of inhomogeneous conventional feed flow patterns on precipitated calcium carbonate (PCC). Herein, a Taylor-Couette Carbonate Conversion (TC3) reactor is used to direct the formation of spherical vaterite particles with uniform particle size distribution preferentially over calcite and other phases. The formed vortex patterns inside TC3 reactor provide homogeneous reaction spaces conducive to PCC formation, ensuring uniform mixing throughout the process. By increasing the rotational speed and the residence time, higher purity carbonates with more uniform sizes are obtained. Furthermore, preferential vaterite formation is also observed in leachates obtained from alkaline industrial residues such as construction and demolition waste and steel slag. Thus, the proposed approach is effective in harnessing multiple waste streams such as CO2 emissions and alkaline industrial residues to produce calcium carbonate phases such as vaterite with structural and morphological specificity.

Effect of rare earth (Sm3+) substitution in mixed Ni-Zn-Co ferrites: Structural, magnetic, and DC electrical resistivity studies

NiZnCo ferrite has good magnetic properties and is one of the core materials used in magnetic devices. The solid-state reaction approach is utilized to synthesize Ni0.4Zn0.35Co0.25Fe2-xSmxO4 (x = 0.0, 0.02, 0.04, 0.06, 0.08, and 0.1) ferrites for investigation of structural, morphological, functional, magnetic and electrical resistivity properties using various characterization techniques. The techniques used for characterization were XRD, SEM, FTIR, VSM, and DC electrical resistivity. XRD spectra were used to determine phase confirmation, cubic crystallite size, andtheir variation with dopant content. No additional phase or impurity was found. The SEM pictures revealed ahomogeneous spherical particle formation with minimal porosity. With absorption bands under 1000 cm−1, FTIR spectra indicate the formation of a spinel structure. Tetrahedral (580 to 599 cm−1) and octahedral (388 to 399 cm−1) bond changes can be seen in infrared spectra. The magnetic hysteresis curves revealed soft ferromagnetic behavior, with coercivity (Oe) (532.13 to 312.10Oe) rising and saturation magnetization (Ms) (83.51 to 60.75 emu/g) falling as doping concentration increased. The DC electrical resistivity of synthesized nanoparticles with various compositions was measured against higher temperatures to confirm their semiconductor nature. The findings demonstrated the typical decreasing trend with rising temperature.

Synthesis of Organopolysilazane Nanoparticles as Lithium-Ion Battery Anodes with Superior Electrochemical Performance via the Two-Step Stöber Method.

The Stöber method, a widely utilized sol-gel technique, stands as a green and reliable approach for preparing nanostructures on a large scale. In this study, we employed an enhanced Stöber method to synthesize organopolysilazane nanoparticles (OPSZ NPs), utilizing polysilazane oligomers as the primary precursor material and ammonia as the catalytic agent. By implementing a two-step addition process, control over crucial parameters facilitated the regulation of the nanoparticle size. Generally, maintaining relatively low concentrations of organopolysilazane and catalyst while adjusting the water/acetonitrile ratio can effectively enhance the surface energy of the organopolysilazane, resulting in the uniform formation of small spherical particles. The average particle size of the synthesized OPSZ NPs is about 140 nm, which were monodispersed and characterized by scanning electron microscopy, transmission electron microscopy, and dynamic light scattering. Furthermore, the composition of OPSZ NPs after pyrolysis was confirmed as SiC2.054N0.206O1.631 with 5.44 wt % free carbon structure by X-ray diffraction and energy-dispersive X-ray spectroscopy. Notably, the electrochemical performance assessment of SiCNO NPs as potential electrode materials for lithium-ion batteries exhibited promising outcomes. Specifically, at 1 A g-1 current density, the specific capacity is 585.45 mA h g-1 after 400 cycles, and the minimum capacity attenuation per cycle is only 0.1076 mA h g-1 (0.0172% of the original capacity), which indicates excellent energy storage capacity and cycle stability. In summary, this research contributes to the development of advanced anode materials for next-generation energy storage systems, marking a stride toward sustainable energy solutions.

Connectivity patterns in lead-free piezocomposites: A critical analysis for 0-3 and 1-3 configurations

In the quest for eco-friendly alternatives within materials science, the development of sustainable and non-toxic piezoelectric composites is of utmost importance. This study undertakes a computational exploration to elucidate the influence of phase connectivity on the engineering performance of lead-free piezocomposites. Employing a combination of analytical and numerical methodologies, we critically evaluated various figures of merit across different microstructural configurations, juxtaposing these findings with traditional lead zirconate titanate (PZT)-based materials. Our analysis considers 0-3 and 1-3 connectivity patterns, incorporating active phases in the form of spherical particles and cylindrical fibers. We also examine the impact of carbon nanotubes (CNTs) in enhancing the polymeric matrix, which introduces the potential for network percolation and further mechanical and electrical property optimization. The study yields pivotal insights into the phase connectivity of lead-free piezocomposites, with direct implications for their application in sensing, actuating, and energy harvesting domains. We ascertain that the electromechanical performance of these composites is contingent upon the connectivity pattern and the proportion of active phase. Notably, the KNNS-BNZH & Polyethylene composite demonstrates exceptional potential in 1-3 configurations, while the BTO & PVDF composite distinguishes itself with superior dielectric and piezoelectric responses across varying volume fractions. The strategic infusion of CNTs into the PDMS matrix emerges as a significant enhancer of electromechanical attributes, albeit with performance improvements that are specific to the type of coefficient and CNT concentration. This investigation underscores the nuanced interplay between composite design and microstructural attributes, reinforcing the critical role these factors play in the advancement of effective and eco-conscious piezoelectric materials.

Polypyrrole-wool composite with electrical heating properties fabricated via layer-by-layer method

This study presents the development of conductive polymer-textile composites with outstanding electric heating properties achieved through the in-situ polymerization of polypyrrole on wool-felt fabrics, renowned for their superior thermal insulation. Employing successive layer-by-layer (LBL) cycles facilitated precise control over the uniform deposition of polypyrrole with the fabrics. The investigation focused on the interaction between wool fiber and polypyrrole, evaluating appearance, add-on, and electrical heating performance with varying LBL cycles. The polymerization process resulted in the formation of spherical polypyrrole particles on the wool-felt, with deposition increasing alongside LBL cycle numbers. Mechanical properties, including tensile strength and bending rigidity, exhibited enhancement with polypyrrole deposition, while strain reduction was noted, with minimal influence from LBL cycles. Electrical properties, particularly surface resistance, displayed a rapid decrease up to the second LBL cycle. Concerning electrical heating performance, the application of a 12 V voltage resulted in a linear increase in surface temperature with increasing LBL cycles, peaking at 15.5 ℃. Notably, this sustained electrical heating effect persisted even after voltage removal, attributed to the low thermal conductivity of wool fiber. Moreover, the polypyrrole conductive layer maintained exceptional conductivity following repeated abrasion and washing, credited to improved uniformity through LBL cycles. The synergy of wool's insulating properties and polypyrrole's conductivity, as confirmed in this study, presents the potential for a highly efficient heating fabric. These developed materials exhibited improved heating performance, energy conservation, and minimal change in mechanical properties, making them suitable for applications such as electrical heating smart clothing.

Preparation of bamboo-shaped mesoporous silica using long-chain alcohol cosurfactants

Herein, orderly arranged bamboo-like mesoporous silica materials were prepared using cetyltrimethylammonium bromide (CTAB) as the template and n-hexanol as the long-chain alcohol cosurfactant. The ordered meso-structure was characterized by XRD analysis, field emission scanning electron microscopy (FE-SEM, Hitachi S4800), transmission electron microscopy, BET and IR spectroscopy analysis. The effects of the CTAB/n-hexanol molar ratio(R), length of the hydrophobic chain with a terminating hydroxyl group on the long-chain alcohol cosurfactant, parity of the hydrophobic carbon atoms on the surface topography, specific surface area, and pore size of the powder were investigated. The results showed that when the molar ratio = 1, the mesoporous silica presented neatly arranged bamboo segment lengths of 19.6–23.9 μm, platycodon grandiflorum widths of 2.13–3.32 μm, pore size of 3.04 nm, and surface area of 820.034 m2/g. Increasing or decreasing the amount of n-hexanol directing led to denser or looser lateral molecular interactions between CTAB and the co-structure-directing agents that respectively reduced or increased the pore size, with the latter resulting in the formation of spherical particles. When n-hexanol was replaced by n-heptanol or n-octanol, the pore size and surface area of the mesoporous silica decreased significantly with the increase in the hydrophobic chain length.

Deciphering the True FEC Reduction Mechanism and Its Implications to the Understanding of the SEI in Li-Ion Batteries

The main challenges in rechargeable batteries, especially when aiming for high energy density, arise from the limited electrochemical stability window of current state-of-the-art electrolytes. Negative electrode active materials, such as silicon, tin oxide and others, whose capacity is many times higher than that of graphite, often exhibit large volume expansion upon lithiation and therefore the SEI formed on their surface is unstable. The most popular strategy for improving their cycling stability is the use of electrolyte additives that are reduced at potentials more positive than the electrolyte solvents. Their decomposition products are incorporated in the SEI, leading to a more stable electrode/electrolyte interface.One of the most-investigated electrolyte additives is fluoroethylene carbonate (FEC), because it has been shown to lead to a significant performance enhancement of Si- and Sn-based anodes. Many reaction pathways have been proposed, however there is currently no agreement on the exact type of chemical compounds constituting the decomposition products, nor on the exact mechanism for FEC decomposition. To address these questions, we conducted a systematic study that tracked the morphological and chemical changes during electrochemical decomposition of FEC. We have found that despite FEC often being referred as a “film-forming” additive, the first stage of its decomposition leads instead to the formation of spherical particles, consisting mainly of lithium fluoride (see figure below);1 only later a carbonate-rich film covers the entire electrode, covering as well the LiF-rich spheres. This phenomenon has been overlooked before likely due to very simple reason, disclosed in our contribution.A detailed investigation using XPEEM—a surface-sensitive analytical technique with high lateral resolution—as a function of electrolyte composition shows that fluorine in the later-formed carbonate film comes from the electrolyte salt, while all fluorine from FEC decomposition resides in the spherical particles, formed upon FEC reduction. In addition, we have found that the size and amount of particles strongly depend on the cell medium, where electrolytes with higher dielectric constant lead to larger particle size, as does the presence of the high-capacity electroactive materials in the electrode, both contributing to the final properties of FEC-derived SEI. The results of this study provide a deeper understanding of how fluorine-containing additives work and enables tuning of the SEI properties to the desired morphological and chemical outcome by using the laws of simple crystal-growth theory by adjusting the inter-cell environment.This work demonstrates that, with the right analytical tools, the true nature of the even seemingly very-well studied compounds can be revealed and a full understanding of their decomposition mechanisms can be clarified. Acknowledgement This research was supported by InnoSuisse (Project number 18254.2) References Y. Surace, D. Leanza, M. Mirolo, Ł. Kondracki, C.A.F. Vaz, M. El Kazzi, P. Novák, S. Trabesinger, Energy Storage Materials 2022, 44, 156-167. Figure 1

Rosemary particle as a new green additive to improve polysulfone membrane separation performance in removal of organic pollutants

This study used rosemary particles to make PSf nanofiltration membranes with antifouling properties, for medicinal pollutants and Azo dyes removal. The extract of rosemary plant was extracted using the Soxhlet process. Then homogeneous rosemary particles were embedded in the PSf membrane matrix as a green additive using the NIPS method. Characterization of the structure and morphology of rosemary particles and membranes was performed by FTIR, XRD, UV–Vis, FE-SEM, STA, DLS, ATR-FTIR, SEM, AFM, Zeta potential and TGA analyses. The results indicated the formation of homogeneous, hydrophilic, and spherical particles with a negative surface charge as well as physical stability in aqueous solutions and high thermal stability with a particle size of about 229 nm. Adding the optimal amount of rosemary particles increased the hydrophilicity (reduced water contact angle from 60.55° to 52.15°) and porosity (increased from 69.3 to 91.7%). Also, by adding 1 wt% of rosemary particles, the permeability of the membrane increased by 3.5 times. The increase in mean pore radius (from 4.77 to 6.08 nm), smoother surface of modified membranes and negative charge on the membrane surface proved this improvement. Therefore, the amount of 1 wt% caused the best flux performance of pure water (from 126 to 359 LMH) and BSA solution (from 104.5 to 202.3 LMH). Moreover, RE/PSf membranes showed a high rejection for azithromycin: 81.98%, cefixime: 58.07%, O II: 71.75, RY 160: 81.71 and RB 5: 93.69%.

Eggshell-Mediated Hematite Nanoparticles: Synthesis and Their Biomedical, Mineralization, and Biodegradation Applications

The present study demonstrates the synthesis of phase pure hematite (α-Fe2O3) nanoparticles (NPs) using collagen protein and calcium carbonate extracted from eggshell membranes and eggshells, respectively, as organic additives. To test the influence of organic additives on the quality of the resulting NPs, the amount of eggshell powder was varied between 1 to 5 g in aqueous iron nitrate solution. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and RAMAN analysis confirmed the formation of hematite NPs without any impurities. FTIR spectra revealed the presence of polyphenolic constituents on the surface of the resulting NPs as stabilizers, which may potentially be responsible for the observed antioxidant and antibacterial properties. Furthermore, the stable phase and the presence of low defects divulged the high hardness value (~983 HV) and fracture toughness (8.59 MPa m1/2), which can be exploited for bone implantation. The FE-SEM results demonstrate the formation of spherical particles, which are well-separated NPs. The results of a biodegradation study which was carried out in phosphate-buffered saline (PBS) revealed that the as-prepared NPs retained their hardness even after 72 h of soaking. These prepared NPs showed 95% radical scavenging activity (RSA) and were good carriers against S. aureus bacteria. Moreover, the SEM images of the mineralization of iron oxide NPs confirmed the formation of new bone. After 5 weeks, all pores were filled, and the minerals were deposited on the surfaces of the scaffolds.

Conformational transitions of the HIV-1 Gag polyprotein upon multimerization and gRNA binding

During the HIV-1 assembly process, the Gag polyprotein multimerizes at the producer cell plasma membrane, resulting in the formation of spherical immature virus particles. Gag-genomic RNA (gRNA) interactions play a crucial role in the multimerization process, which is yet to be fully understood. We performed large-scale all-atom molecular dynamics simulations of membrane-bound full-length Gag dimer, hexamer, and 18-mer. The inter-domain dynamic correlation of Gag, quantified by the heterogeneous elastic network model applied to the simulated trajectories, is observed to be altered by implicit gRNA binding, as well as the multimerization state of the Gag. The lateral dynamics of our simulated membrane-bound Gag proteins, with and without gRNA binding, agree with prior experimental data and help to validate our simulation models and methods. The gRNA binding is observed to affect mainly the SP1 domain of the 18-mer and the matrix-capsid linker domain of the hexamer. In the absence of gRNA binding, the independent dynamical motion of the nucleocapsid domain results in a collapsed state of the dimeric Gag. Unlike stable SP1 helices in the six-helix bundle, without IP6 binding, the SP1 domain undergoes a spontaneous helix-to-coil transition in the dimeric Gag. Together, our findings reveal conformational switches of Gag at different stages of the multimerization process and predict that the gRNA binding reinforces an efficient binding surface of Gag for multimerization, and also regulates the dynamic organization of the local membrane region itself.

ELECTROSYNTHESIS OF CATALYTIC ACTIVE Pd-Cu AND Pd-Au BIMETALLIC NANOPARTICLES NANOCOMPOSITES WITH POLY(N-VINYLPYRROLIDONE) AND NANOCELLULOSE

It was investigated the preparation in an undivided cell of Pd-Cu and Pd-Au bimetallic nanoparticles (NPs) by methylviologen (MV2+) -mediated electrochemical reduction of equimolar amounts of Cu(II), Pd(II) and Au(I) in the presence of poly(N-vinylpyrrolidone) (PVP) and nanocellulose (NC) at controlled potential of generating MV cation radical in aqueous medium at room temperature. Electrosyntheses were performed by sequential or joint reduction of metal ions by passing a theoretical amount of electricity. When Pd(II) ions are added to CuNPs, as well as Au(I) ions are added to PdNPs, a galvanic replacement process is observed, namely oxidation of Cu0 by Pd(II) and Pd0 Au(I) ions. The results of complete reduction are nanocomposites of mainly spherical MNPs, dispersed in the solution bulk, and stabilized by PVP on the surface of the NC. In the sequential synthesis of CuNPs and then PdNPs, the nanocomposite is presented as Cu2O nanoroses coated with fine PdNPs. Nanocomposites of Pd NPs with Cu2O or Au shows the mainly formation of spherical particles with the size of 4 to 50 nm depending on the production method. X-ray powder diffraction (XRD) data of nanocomposites confirm the formation of a mixture of PdNPs (0.8 - 10 nm) with large gold crystallites (until 24 nm), as well as the oxidation of CuNPs to cuprite (Cu2O). The size of metal crystallites and copper oxide varies in the range from 0.8 to 24 nm. In the test reaction of p-nitrophenol reduction with sodium borohydride in aqueous medium, all tested nanocomposites showed time-increasing catalytic activity. When Cu is added to Pd, the catalytic reduction reaction is maintained, while the addition of Au to Pd decreases the catalytic activity of PdNPs by an order of magnitude.

Microwave-assisted construction of AgIO3/BaTiO3 heterostructure with excellent photocatalytic activity for tetracycline and methyl blue degradation

A series of AgIO3/BaTiO3 composite photocatalysts were synthesized by a microwave-assisted hydrothermal method. Among obtained samples, ABO-2 exhibited superior catalytic performance toward the photocatalytic degradation of TC (30 mg/L) with a degradation rate reaching 76.2% within 40 min. Scanning electron microscopy and transmission electron microscopy demonstrated the formation of smaller spherical particles of BaTiO3 on the AgIO3 surface with a direct Z-type heterojunction. Photoluminescence indicated weaker fluorescence response intensity of the composite ABO-2, suggesting effectively suppressed recombination of electron-hole pairs. The impact of pH and inorganic anions on the removal of pollutants by ABO-2 was discussed in detail by degradation experiments. Experimental evidence obtained from free radical active species capture experiments and electron spin resonance (ESR) spectroscopy tests revealed that h+ and •O2− are the primary active species. The intermediates of the TC degradation process analyzed by liquid chromatograph mass spectrometer (LC-MS), as well as the potential degradation pathways and mechanisms were all studied. The photodegradation experiments under sunlight demonstrated ABO-2 achieving a degradation rate of 74.4% toward MB (10 mg/L) within 75 min, indicating a promising composite catalyst for practical applications.