Chemical Stability Research Articles

Fabrication of Zinc Oxide Thin Films by Sol-Gel Dip Coating Process

Zinc oxide (ZnO) is a non-toxic material known for its distinctive physical and chemical properties, including a direct band gap energy of 3.37 eV and a large exciton binding energy of 60 meV, which contribute to its significant thermal and chemical stability at room temperature. Due to these characteristics, ZnO plays a critical role in various applications, such as UV light emitters, transparent conducting thin films in electronic devices, gas sensors, piezoelectric materials, transducers, and as a transparent conductive oxide (TCO) layer in thin-film photoelectrochemical cells. Numerous fabrication techniques have been employed to produce ZnO thin films. However, many of these methods require costly equipment, high vacuum environments, and elevated temperatures. In contrast, the sol-gel process stands out as a convenient, cost-effective, and versatile method for ZnO thin film fabrication. It offers advantages such as simplicity, low crystallization temperature, ease of reproducibility, molecular-level homogeneity, and precise compositional control. In this study, ZnO thin films were deposited onto Indium Tin Oxide (ITO) glass substrates using the sol-gel dip coating method, with varying preparative parameters: sol concentrations and annealing temperatures. The resulting samples were characterized using a UV-visible spectrophotometer, X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and energy dispersive X-ray spectroscopy (EDX). The results demonstrated that the unique properties of ZnO thin films are highly dependent on the preparative parameters. Specifically, the band gap energy decreased from 3.25 eV to 3.18 eV with increasing sol concentration and also showed a similar decline with higher annealing temperatures. XRD patterns revealed a smaller full width at half maximum (FWHM) of the most intense peak (002) at higher sol concentrations and annealing temperatures, indicating an increase in crystallite size. FESEM images highlighted distinct morphological changes corresponding to the variations in sol precursor concentration and annealing temperature, while EDX analysis confirmed the formation of highly pure ZnO thin films on ITO glass substrates.

Chemical thermodynamics of biomass, cellulose, and cellulose derivatives: A review

This article provides a review of the research on the chemical thermodynamics and thermochemistry of biomass, cellulose, and its derivatives such as ethers, esters, and oxycelluloses. For diverse biomass types, gross and net heating values were studied. It has been established that these energetical characteristics of biomass can be calculated using a superposition of the energetical characteristics of the main components of biomass such as cellulose, hemicelluloses, lignin, lipids, proteins, etc. The pelletization of biomass improves its fuel performance. It was shown that, if the ultimate goal is to generate the maximum amount of thermal energy, then it is more profitable to directly burn the initial biomass in the form of pellets than to burn the amount of solid or liquid biofuel that can be extracted from this biomass. After the cellulose study, the direct and exact thermochemical method for determining the crystallinity degree of this biopolymer was proposed. In addition, the standard combustion and formation enthalpies of various cellulose samples were studied. As a result, the thermodynamic characteristics of four crystalline allomorphs of cellulose, CI, CII, CIII, and CIV, were obtained and their thermodynamic stability was evaluated. The thermochemistry of enzymatic hydrolysis of cellulose was studied. In addition. The thermodynamical characteristics of various cellulose derivatives were determined, and the thermochemistry of the reactions of cellulose alkalization, etherification, esterification, and oxidation was studied.

A Supramolecular-Nanocage-Based Framework Stabilized by π-π Stacking Interactions with Enhanced Photocatalysis.

π frameworks, defined as a type of porous supramolecular materials weaved from conjugated molecular units by π-π stacking interactions, provide a new direction in photocatalysis. However, such examples are rarely reported. Herein, we report a supramolecular-nanocage-based π framework constructed from a photoactive Cu(I) complex unit. Structurally, 24 Cu(I) complex units stack together through π-π stacking interactions, forming a truncated octahedral nanocage with sodalite topology. The inner diameter of the nanocage is 2.8 nm. By sharing four open faces, each nanocage connects with four equivalent ones, forming a 3D porous π framework (π-2). π-2 shows good thermal and chemical stability, which can adsorb CO2, iodine, and methyl orange molecules. More importantly, π-2 can serve as a photocatalyst for hydrogen evolution reaction. With ultrafine Pt subnanometer particles (0.9±0.1 nm) incorporated into the nanocages as a co-catalyst, the hydrogen evolution rate reaches a record-high value of 524012 μmol/gPt/h in the absence of any additional photosensitizers. The high photocatalytic activity can be ascribed to the ultrafine size of the Pt particles, as well as the fast electron transfer from π-2 to the highly active Pt upon illumination. π-2 represents the unique stable supramolecular-cage-based π framework with excellent photocatalytic activity.

Machine Learning-Guided Discovery of Copper(I)-Iodide Cluster Scintillators for Efficient X-ray Luminescence Imaging.

Developing efficient scintillators with environmentally friendly compositions, adaptable bandgaps, and robust chemical stability is crucial for modern X-ray radiography. While copper(I)-iodide cluster crystals show promise, the vast design space of inorganic cores and organic ligands poses challenges for conventional approaches. In this study, we present machine learning-guided discovery of copper(I)-iodide cluster scintillators for efficient X-ray luminescence imaging. Our findings reveal that combining base learning models with fused features enhances model generalization, achieving an impressive determination coefficient of 0.88. By leveraging this approach, we obtain a high-performance Cu(I)-I cluster scintillator, named copper iodide-(1-Butyl-1,4-diazabicyclo[2.2.2]octan-1-ium)2, which exhibit radioluminescence 56 times stronger than that of PbWO4, and enables a detection limit for X-rays of 19.6 nGyair s-1. Furthermore, we demonstrate the versatility of these scintillators by incorporating them as microfillers in the fabrication of flexible composite scintillators for X-ray imaging, achieving a static resolution of 20 lp mm-1 and demonstrating promising performance for dynamic X-ray imaging.

The oligonucleotides containing N7-regioisomer of guanosine. Influence on thermodynamic properties and structure of RNA duplexes.

During chemical synthesis of the purine riboside, the N7-regioisomer is kinetically formed whereas the N9-regioisomer is a thermodynamically formed product. We have studied the effect of substituting the N9-regioisomer of guanosine with its N7-regioisomer (N7-guanosine, 7G) at a central position of several RNA duplexes. We found that this single substitution by 7G severely diminished their thermodynamic stabilities when 7G paired with C and U, but remarkably, led to a significant amount of stabilization in most of the duplexes when forming mismatches with G and A. The extent of stabilization was observed to be dependent on the sequence and orientation of neighboring base pairs of N7-guanosine. 1D and 2D NMR studies on the duplexes along with extensive molecular dynamics simulations revealed the conformational differences occurring due to substitution of G by 7G and it was observed that the thermodynamic results were largely explainable by considering the formation of stable non-canonical hydrogen bonding interactions, although other interactions such as stacking and electrostatic interactions could also play a role. These observations can have important applications in the design of RNA-based disease diagnostics and therapeutics.

Carbon nanomaterials for efficient oxygen and hydrogen evolution reactions in water splitting: A review

Water splitting has gained significant attention as a means to produce clean and sustainable hydrogen fuel through the electrochemical or photoelectrochemical decomposition of water. Efficient and cost-effective water splitting requires the development of highly active and stable catalysts for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Carbon nanomaterials, including carbon nanotubes, graphene, and carbon nanofibers, etc., have emerged as promising candidates for catalyzing these reactions due to their unique properties, such as high surface area, excellent electrical conductivity, and chemical stability. This review article provides an overview of recent advancements in the utilization of carbon nanomaterials as catalysts or catalyst supports for the OER and HER in water splitting. It discusses various strategies employed to enhance the catalytic activity and stability of carbon nanomaterials, such as surface functionalization, hybridization with other active materials, and optimization of nanostructure and morphology. The influence of carbon nanomaterial properties, such as defect density, doping, and surface chemistry, on electrochemical performance is also explored. Furthermore, the article highlights the challenges and opportunities in the field, including scalability, long-term stability, and integration of carbon nanomaterials into practical water splitting devices. Overall, carbon nanomaterials show great potential for advancing the field of water splitting and enabling the realization of efficient and sustainable hydrogen production.

Hot isostatic pressing of ball milled novel grade high entropy alloys at different sintering time and the investigation of their mechanical and corrosion resistance properties

Abstract With the discovery of high entropy alloys, new materials with superior properties have emerged. According to recent research, high-entropy alloys’ multi-component structure and mixing entropy have made them more prominent than other alloys. Because of their excellent chemical and mechanical properties—such as high hardness, high-temperature resistance, high wear resistance, chemical stability, and high corrosion resistance—high entropy alloys outperform other material types in various applications. A new grade of mechanically alloyed high entropy alloy (HEA) of composition 23Fe-21Cr-18Ni-20Ti-18Mn was consolidated by a hot isostatic pressing (HIP) at a temperature of 1000 °C, at different sintering time of 30, 60, and 90 min respectively. We have investigated the impact of sintering time on the microstructure, mechanical, corrosion, and wear-resistance properties. The x-ray diffraction (XRD) spectra of the 30 min HIPed HEA sample showed dominant s-FeCr phases and traces of γ-Fe, and the Ni-Ti phases. Whereas, the 90 min HIPed HEA samples showed more dominant Ni-Ti and traces of γ-Fe, and β-Mn phases. There is a phase transformation from BCC to HCP of consolidated HEA at increased holding time. The density of the samples increases from 5.882 to 6.327 g cm−3 and the porosity percentage decreases from 12.93 to 6.35% with the increase in the holding time. The Vickers microhardness value for 30, 60, and 90 min HIPed 23Fe-21Cr-18Ni-20Ti-18Mn HEA at 1000 °C was found to be 433, 513, and 793 HV respectively at an indentation load of 0.1 kgf. The consolidated HEA sample undergoes an abrasive and oxidative wear mechanism with ploughing and plastic deformation modes. The morphology of the wear debris was investigated using SEM. The 90 min sintered sample showed an excellent corrosion resistance due to the high rate of material densification and minimum surface flaws.

Polyphenol-treatment without preceding glutaraldehyde fixation: a potential paradigm change for bioprosthetic heart valves

Abstract Background Glutaraldehyde (GA) is the common fixative agent for bioprosthetic heart valves (BHVs). However, its chemical instability can expose calcium binding sites and, at commercially used concentrations, GA does not ensure effective immunological tolerance, triggering an immune response correlated to degeneration. Recently, polyphenols (PPs) achieved an almost complete xenoantigens inactivation in GA-fixed BHVs ensuring chemical stability of the treated tissue while improving mechanical characteristics and adding anti-infective and anti-thrombotic properties [1-4]. Purpose A new PP-based treatment has been introduced as a potential GA substitute in BHV manufacturing. The unique chemical properties of PPs permit them to interact with the tissue through stable chemical bonds without depolymerization over time, achieving several improvements that promise to extend the long-term durability of BHVs (Fig.1). Methods The study compared the effects of two cross-linking methods on bovine pericardial tissue: (1) traditional fixation in GA, and (2) treatment with PPs without GA. The type of chemical interaction between PPs and tissue was evaluated through nuclear magnetic resonance. The xenoantigens inactivation was quantified in-vitro by ELISA test and in-vivo in a humanized mouse animal model. Biomechanical properties were assessed through uniaxial stress-strain tests and cross-link density through the shrinkage temperature test. The protective effect against bacterial adhesion was evaluated against a strain of S aureus, while the inhibition of thrombosis was evaluated in-vivo in a pig animal model and in-vitro in a blood-loop using bovine blood with radio-labeled platelets. Results PPs effectuated multiple chemical bonds with and within the pericardium including cross-links based on covalent and hydrogen bonds, stacking, and electrostatic interactions. The inactivation of over 90% of surface-xenoantigens of the treated tissue allowed for superior biocompatibility (compared to <50% by commercial GA concentrations). The increase in elongation exhibited by PP-treated tissue confirmed excellent biomechanical features (Fig.2) while a sufficient degree of cross-linking was demonstrated through an adequate shrinkage temperature. Furthermore, a significant degree of bacterial adhesion (86% inhibition evaluated with S. aureus) and thrombus formation (Fig.2, up to 90% inhibition) were observed. Conclusion There is a real clinical need for improved chemical stability, calcification resistance, and immunological tolerance of current BHVs (surgical and transcatheter). PP technology may substitute the use of GA extending their performance and durability, thereby opening trans-catheter heart valves to younger patients. Reducing the need for mechanical heart valves would also address the associated risks of lifelong anticoagulation therapy.Figure 1Figure 2

A Sustainable and Eco-Friendly Membrane for PEM Fuel Cells Using Bacterial Cellulose

Bacterial cellulose (BC) is an advantageous polymer due to its renewable nature, low cost, environmental compatibility, biocompatibility, biodegradability, chemical stability, and ease of modification. With these advantages, BC is an interesting candidate for the development of novel eco-friendly materials for proton-exchange membrane (PEM) applications. However, its practical applications have been limited by its relatively high dispersion in water, which usually occurs during the operation of proton-exchange membrane fuel cells (PEMFCs). In addition, the proton conductivity of bacterial cellulose is poor. In this study, functionalized BC modified with 3-aminopropyltriethoxysilane (APTES) was prepared using a solvent casting method to enhance its performance. The results showed that the water stability of the modified BC membrane was significantly improved, with the contact angle increasing from 54.9° to 103.3°. Furthermore, the optimum ratio of BC and APTES was used to prepare a proton-exchange membrane with a maximum proton conductivity of 62.2 mS/cm, which exhibited a power generation performance of 4.85 mW/cm2 in PEMFCs. It is worth mentioning that modified BC membranes obtained by combining an alkaline proton carrier (-NH2) with BC have rarely been reported. As fully bio-based conductive membranes for PEMFCs, they have the potential to be a low-cost, eco-friendly, and degradable alternative to expensive, ecologically problematic fluoric ionomers in short-term or disposable applications, such as biodegradable electronics and portable power supplies.

Revolutionizing acridine synthesis: novel core-shell magnetic nanoparticles and Co-Zn zeolitic imidazolate framework with 1-aza-18-crown-6-ether-Ni catalysts

Nanoparticles have emerged as a critical catalyst substrate due to their exceptional features, such as catalytic efficiency, high stability, and easy recovery. In our research, we have developed an innovative and environmentally friendly magnetic mesoporous nanocatalyst. Using the co-precipitation method, we produced magnetic nanoparticles (Fe3O4) and coated them with Zeolitic imidazolate frameworks (ZIFs) to enhance their surface area and chemical stability. The resulting substrate was functionalized with 1-aza-18-crown-6-ether and nickel metal. Our prepared catalyst has been rigorously evaluated using advanced techniques, including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Brunauer-Emmet-Teller (BET), vibrating sample magnetometry (VSM), scanning electron microscopy and energy dispersive X-ray (SEM-EDS), inductively coupled plasma (ICP), elemental mapping analysis (EMA), thermogravimetric analysis (TGA), and transmission electron microscopy (TEM). By synthesizing acridine derivatives, we have demonstrated the exceptional efficiency of our catalyst in organic compound synthesis. Through optimization, we have established the ideal parameters for catalytic processes, including catalyst amount, temperature, time, and ultrasonic use. Our catalyst has been proven to exhibit remarkable physical and chemical properties, such as porosity, temperature resistance, and recyclability. Notably, our heterogeneous nanocatalyst has shown outstanding performance and can be recycled six times without any loss in efficiency, affirming its potential in acridine.

Amorphous Exsolution of Fe3O4 Nanoparticles in SrTiO3: A Path to High Activity and Stability in Photoelectrochemical Water‐Splitting

Exsolution creates metal nanoparticles embedded within perovskite oxide matrices, promoting optimal exposure, even distribution, and robust interactions with the perovskite structure. Fe3O4, an oxidized form of Fe, is an attractive catalyst for photoelectrochemical (PEC) water‐splitting due to its strong light absorption, excellent electrical conductivity, and chemical stability. However, exsolving Fe is challenging, often requiring harsh reduction conditions that can decompose the perovskite. Herein, hybrid composites are fabricated for PEC water‐splitting by reductively annealing a solution of SrTiO3 photoanode and Fe cocatalyst precursors. In situ transmission electron microscopy reveals uniform, high‐density Fe particles exsolving from amorphous SrTiO3 films, followed by film‐crystallization at elevated temperatures. This innovative process extracts entire Fe dopants while maintaining structural stability, even at doping levels exceeding 50%. Upon air exposure, the embedded Fe particles oxidize to Fe3O4, forming a Schottky junction and enhancing light absorption. These conditions yield a high activity of 5.10 mA cm−2 at 1.23 V versus reversible hydrogen electrode (an 11.86‐fold improvement over SrTiO3) from the 30% Fe‐doped SrTiO3, with excellent stability (97% retention) over 24 h. Theoretical calculations indicate that in the amorphous state, FeO bonds weaken while TiO bonds remain strong, promoting selective exsolution. The mechanisms driving amorphous exsolution versus crystal exsolution are elucidated.

Novel Preparation and Characterization of Zinc Ricinoleate Through Alkali Catalysis

The enhanced thermal and chemical stability of Zinc oxide-based materials make them excellent candidates for the removal of odor-producing pollutants and compounds. The zinc salt of ricinoleic acid, commonly known as zinc ricinoleate, is viewed as the top performer. This article describes an innovative two-step synthesis of zinc ricinoleate, where the first step consists of the preparation of an intermediate compound, methyl ricinoleate, which is synthesized via transesterification of castor oil with methanol and catalyzed by sodium hydroxide. The second step comprises the preparation of zinc ricinoleate through the saponification of methyl ricinoleate in the presence of zinc oxide particles. XRD, FTIR, and NMR spectroscopies confirmed the synthesis of methyl ricinoleate and zinc ricinoleate. HR-SEM and AFM images showed the formation of larger particles, while the thermal stability of the materials was confirmed by TGA.

A Stable Layered Microporous MOF Assembled with Y-O Chains for Separation of MTO Products.

Benefiting from highly tunable pore environments, some metal-organic frameworks (MOFs) have recently shown promising prospects in the separation of methanol-to-olefin (MTO) products (mainly C3H6 and C2H4). However, the "trade-off" between gas storage capacity and selectivity always results in inefficient separation. In addition, poor stability of MOFs also limits practical separation applications. Herein, we have successfully assembled a layered Y-MOF (FJI-W9) with bent diisophthalate ligands (H4L), Y-O chains, and 2-fluorobenzoic acids. As expected, FJI-W9 not only exhibits good chemical stability but also shows significant potential for C3H6/C2H4 separation. For FJI-W9, the C3H6 uptake at 298 K and 10 kPa is 63 cm3/g, and the IAST selectivity of FJI-W9 for C3H6/C2H4 (V/V = 50/50) is calculated to be 20.5. To the best of our knowledge, both C3H6 uptake and selectivity of FJI-W9 surpass most porous materials. GCMC simulation indicates that the special supramolecular binding sites in FJI-W9 have much stronger interactions with C3H6 than C2H4 molecules. More importantly, practical breakthrough experiments demonstrate that FJI-W9 can effectively separate C3H6/C2H4 (50/50) mixtures, thus obtaining high-purity C2H4 and C3H6, respectively.

On thermodynamic stability of black holes. Part II: AdS family of solutions

On thermodynamic stability of black holes. Part II: AdS family of solutions

A 3D Robust and Microporous B←N Framework with 8‐connected Sandwich Nodes for Efficient Separation of Hexane Isomers

Recently B←N organic frameworks (BNFs) have gained substantial attention owing to their unique dative bond energy, which imparts them with specialized functionalities across a broad spectrum of applications. Despite previous reports on BNFs with permanent porosity, research endeavors towards three‐dimensional (3D) BNFs with similar properties are scarce, with no report of robust 3D BNFs featuring permanent porosity to date. Herein, electrostatic complementarystrategy is proposed to construct the first example of 3D robust and microporous BNF, BNF‐100, featuring a reo topology with 8‐connected sandwich nodes assembled via dative B←N bonds. The activated form BNF‐100a exhibits excellent chemical stability and permanent porosity with Langmuir surface area of 645.9 m2 g−1 and pore volume of 0.23 cm3 g−1. BNF‐100a can efficiently separate hexane isomers through sieving mechanisms, as confirmed by vapor adsorption experiments and dynamic breakthrough tests, surpassing the performance of most MOF materials. Finally, we achieved the purification of different branched hexane isomers using a single breakthrough column in a combined breakthrough and purging experiment, which is the first reported instance in the literature on hexane isomer separation.

A 3D Robust and Microporous B←N Framework with 8-connected Sandwich Nodes for Efficient Separation of Hexane Isomers.

Recently B←N organic frameworks (BNFs) have gained substantial attention owing to their unique dative bond energy, which imparts them with specialized functionalities across a broad spectrum of applications. Despite previous reports on BNFs with permanent porosity, research endeavors towards three-dimensional (3D) BNFs with similar properties are scarce, with no report of robust 3D BNFs featuring permanent porosity to date.Herein,electrostatic complementarystrategyisproposedto constructthe first example of3Drobust and microporousBNF,BNF-100, featuring areotopology with 8-connected sandwich nodes assembled via dative B←N bonds. The activated formBNF-100aexhibits excellent chemical stability and permanent porosity with Langmuir surface area of 645.9 m2g-1and pore volume of 0.23 cm3 g-1.BNF-100acan efficiently separate hexane isomers through sieving mechanisms, as confirmed by vapor adsorption experiments and dynamic breakthrough tests, surpassing the performance of most MOF materials.Finally, we achieved the purification of different branched hexane isomers using a single breakthrough column in a combined breakthrough and purging experiment, which is the first reported instance in the literature on hexane isomer separation.

Environmentally Friendly Microemulsions of Essential Oils of Artemisia annua and Salvia fruticosa to Protect Crops against Fusarium verticillioides

Essential oils (EOs) are reported to be natural pesticides, but their use to protect crops is very limited due to EOs’ high instability and great volatility. Nanovectors represent a very smart alternative, and in this study, EOs from Artemisia annua (AEO) and Salvia fruticosa (SEO) were formulated into microemulsions and tested against Fusarium verticillioides. The EOs were extracted by steam distillation and analyzed by GC–MS. The main constituents of AEO were camphor, artemisia ketone, and 1,8-cineole; the main constituents of SEO were 1,8-cineole, camphor, α-pinene, and β-pinene. Artemisia ketone and 1,8-cineole were used to calculate the recovery and chemical stability of the microemulsions. The microemulsions were loaded with 10 mg/mL of EOs, and the recoveries were 99.8% and 99.6% for AEO and SEO, respectively. The sizes of the lipid phases were 255.3 ± 0.6 nm and 323.7 ± 2.3 nm for the AEO and SEO microemulsions, respectively. Activity against F. verticillioides was tested using amphotericin B as the positive control. F. verticillioides was very susceptible to both EOs. When loaded in the microemulsions, AEO and SEO remained very active at a dose of 1.4 and 1.2 mg, with a 99.99% reduction of F. verticillioides. The findings suggest AEO and SEO microemulsions are suitable carriers for the protection of crops against F. verticillioides.

Evaluation of Pollution Linked to Open-Air Storage of Black Shale by the Company Frontier S.A in Sakania in the South-East of the DR. Congo

The black shale from the company “Frontier S.A” in Sakania is impregnated with sulphide minerals such as pyrite which is an iron sulphide (FeS2) and chalcopyrite which is a double sulphide of copper and iron (Cu FeS2). Due to its storage in the open air, these sulphides are particularly oxidized. In addition, this black shale presents a certain physical and chemical instability which can be the basis of the degradation of the nearby surrounding environments (watercourses, soils, groundwater, etc.). It results from our chemical characterization tests that this black shale contains 0.05% Cu, 0.007% Co, 1.3% Fe, 0.007% Ni, 0.001% As; 0.0012% Pb; 0.0021 Cd; 1.75% of S.The mineralogical analysis reveals that the sample contains the main minerals: sulphides, in the form of chalcopyrite and pyrite; oxidized, in the form of quartz; carbonates, in the form of dolomite and calcite, and graphitic material (C). For the determination of the character of acid mine drainage, the static tests for predicting the AMD on the one hand, gave values for the net neutralization potential (NNP) and the ratio between the neutralization and acidification potentials (RPN). respectively 37.5 and 41.39, that is to say values classifying the black shale of Frontier as not generating ADM. And on the other hand, during the kinetic tests using the principle of testing periodic leaching of the sample over a long period, the percolates obtained made it possible to monitor the pH (between 6.2 to 7.07), the redox potential (between -39.8 to 92mV), the electrical conductivity (between 640 to 672μS/Cm), as well as the concentration rate of metals (low mobilization). This made it possible to conclude that the AMD did not exist on the site.

Peripheral Fusion of Carbon-Based Aromatic Rings to B4N4-Heteropentalene Leading to Close π-Stacking in the Solid State.

π-Electronic molecules with a BN-heterocyclic and carbon-based aromatic hybrid ring system (h-CBN) are interesting in that they potentially exhibit synergistic properties arising from the two different π-systems. Here we report the synthesis and properties of a h-CBN-type molecule (1) having a bicyclic B4N4-heteropentalene core fused with extended aromatic rings. This molecule exhibits excellent chemical stability despite the absence of bulky substituents for kinetic protection, which in turn provides effective stacking of the π-system upon crystallization. Depending on the crystallization solvent, 1 forms two polymorphs, i. e., the α- and β-phases. While both phases have one-dimensional columnar structures, the π-stacking geometries associated with the transfer integrals of the frontier orbitals are different, resulting in a twofold difference in the electrical conducting properties. We also found that upon thermal vacuum deposition, 1 gives an amorphous film, which serves as a host material for a red phosphorescent OLED device (maximum external quantum efficiency: 15.5 and 13.3 % at 0.1 and 2.5 mA, respectively).

Tailoring ZrWNb-Based Refractory High Entropy Alloys: A Multidirectional Characterization Through Elemental, Physical, Thermodynamic, and Nuclear Radiation Attenuation Properties

This study explores the development and characterization of 18 novel ZrWNb[(X)(Y)] (where XY are Hf, Ta, Mo, V, Ti) refractory high entropy alloys (RHEAs) designed to enhance mechanical robustness, thermodynamic stability, and radiation shielding effectiveness. Through a rigorous analysis, we evaluated the elastic modulus, entropy, and enthalpy of mixing, atomic size difference, valence electron concentration, and the omega parameter to understand the alloys’ phase behavior and structural integrity. Our findings revealed a broad range of elastic modulus values, indicating diverse mechanical adaptability suitable for high-stress applications. The thermodynamic assessment highlighted several RHEAs with favorable phase stability, particularly ZrWNbTaHf and ZrWNbTiTaHf, which are poised for high-performance usage due to their balanced mixing entropy and enthalpy. This study also benchmarks the RHEAs against conventional alloys, with sample R1 exhibiting the lowest fast neutron effective removal cross section, underscoring its superior neutron shielding capabilities. Additionally, R1 demonstrated exceptional photon attenuation, as evidenced by its competitive half-value layer performance across an extensive energy spectrum. Collectively, these results position R1 as a standout candidate, offering a significant advancement in materials science for applications demanding stringent radiation shielding, such as in nuclear reactor environments and space exploration.