Class Of Materials Research Articles

Fuel‐Driven π‐Conjugated Superstructures to Form Transient Conductive Hydrogels

AbstractDespite advances in creating dissipative materials with transient properties, such as hydrogels and active droplets, their application remains confined to temporal changes in structural properties. Developing out‐of‐equilibrium materials whose electronic functions are parameterized by a chemical reaction cycle is challenging. Yet, this class of materials is required to construct biomimetic materials. In contrast to traditional chemical reaction cycles that exploit molecularly dissolved building blocks at thermodynamic equilibrium, we show that fiber structures derived from reactive naphthalene diimide (NDI) building blocks can be used as resting states to form far‐from‐equilibrium conductive hydrogels after the addition of chemical fuels. Upon fueling the NDI‐derived fibers, a dual‐component activation and deactivation pathway is deduced by kinetic analysis and is absent when using a molecularly dissolved resting state. Investigating the solid‐state morphologies of the structures formed throughout the fuel‐driven reaction cycle using cryo‐EM reveals that the resting thermodynamic fibers evolve to transient thicker fibrils and layered superstructures. We show that the transient redox‐active hydrogels exhibit a nearly threefold increase in electrical conductivity upon fuel consumption before reverting to their original value over hours. These far‐from‐equilibrium materials are potential candidates in applications such as programmable biorobotics and chemical computing.

Zr4+-doped sodium manganese oxide: enhanced electrochemical performance as a cathode in sodium ion batteries.

Sodium manganese oxides are regarded as a valuable class of cathode materials for sodium-ion batteries. By varying the stoichiometry of Na, Mn and O, it is possible to obtain layered, tunnel and spinel type structures, which can withstand the electrochemically-triggered sodiation-desodiation process. In this work, we report the electrochemical performance of Na4Mn2O5, a sodium-rich manganese oxide, which has been previously reported to suffer from structural instability due to the Jahn-Teller distortion of the Mn3+ ion. It was observed that the Na4Mn2-xZrxO5 (x = 0.1) cathode delivered a discharge capacity of ∼203 mA h g-1 post 250 cycles with a capacity retention rate of ∼82.8% on doping with Zr4+ ions. The improvement in cycling ability and rate capability is attributed to the enhanced structural stability and improved electronic conduction brought about by the substitution of Mn3+ by Zr4+ in Na4Mn2O5. Density functional theory-based studies were conducted, which adequately support the obtained results.

High proton conductivity through angstrom-porous titania

Two dimensional (2D) crystals have attracted strong interest as a new class of proton-conducting materials that can block atoms, molecules and ions while allowing proton transport through the atomically thin basal planes. Although 2D materials exhibit this perfect selectivity, the reported proton conductivities have been relatively low. Here we show that vacancy-rich titania monolayers are highly permeable to protons while remaining impermeable to helium with proton conductivity exceeding 100 S cm−2 at 200 °C and surpassing targets set by industry roadmaps. The fast and selective proton transport is attributed to an extremely high density of titanium-atom vacancies (one per square nm), which effectively turns titania monolayers into angstrom-scale sieves. Our findings highlight the potential of 2D oxides as membrane materials for hydrogen-based technologies.

Computational investigation of the phase stability, electronic, optical, phonon spectrum, and elastic behavior of layered perovskites Ca2XO4 (X = Zr, Hf) for optoelectronic applications.

A significant class of solid-state materials, Ruddlesden-Popper (RP) perovskites are well-known for their rich chemical compositions that make them excellent electrocatalysts. Therefore, in this work, we conduct thorough analysis of RP perovskites, specifically Ca2XO4 (X = Zr, Hf). We delve into the structural, electronic, optical, and mechanical properties presenting their insights for the first time. Our investigations reveal that Ca2XO4 (X = Zr, Hf) exhibits stable tetragonal phase structures, with energies (E0) of - 10,522.93eV and - 33,520.14eV, respectively. The calculated in terms of the ground state determines to possess distinct values such as - 4.79 eV/atom for LiScTe2 and - 3.95 eV/atom for Ca2ZrO4 and Ca2HfO4. Notably, the semiconductor characteristics of Ca2ZrO4 and Ca2HfO4 are underscored by their respective wide direct band gap of 5.02eV and 5.30eV. Then, we discuss the optical parameters encompassing the dielectric function, absorption coefficient, optical conductivity, refractive index, and energy loss function. is described as ductile, whereas is defined as brittle. Our outcomes underscore remarkable ability of these materials to absorb ultraviolet radiation from the electromagnetic spectrum, positioning them as promising candidates for optoelectronic applications. We made these calculations by employing first-principles approach rooted in density functional theory (DFT) and utilizing the Perdew-Burke-Ernzerhof-Generalized Gradient Approximation (PBE-GGA) and Tran and Blaha-modified Becke-Johnson (TB-mBJ) functional within the WEIN2K framework. In this framework, Kramers-Kronig relations are used to obtain crucial optical parameters. Mechanical behavior is assessed by employing Voigt-Reuss-Hill approximation (VRH) fulfilling the Born's criteria which emphasizes that these materials are equally appropriate for a broad range of mechanical applications.

Exploring giant dielectric constant in Dy2CoMnO6: evidence of non-overlapping small polaron hopping

Abstract Perovskites, both natural and synthetic, form a large class of materials are a vast class of materials with significant technological relevance due to their remarkable physical properties, such as superconductivity, magnetoresistance, ionic conductivity, and diverse dielectric behaviors. In this study, the dielectric relaxation and transport properties of the double perovskite Dy2CoMnO6(DCMO) synthesized via high-energy ball milling are investigated. DCMO exhibits a notably large dielectric constant, attributed to a combination of intrinsic and extrinsic mechanisms. Frequency-dependent dielectric studies reveal non-Debye-like behavior, validated by augmented Havriliak-Negami function fitting. Impedance spectroscopy confirms the semiconducting nature of DCMO, showing a negative temperature coefficient of resistance, and identifies two distinct relaxation processes corresponding to grain boundaries and grain interiors thereby highlighting the impact of microstructure and defects. The Cole-Cole plot further supports the non-Debye behavior, while thermally activated relaxation suggests damped charge carrier dynamics at grain boundaries. Conduction analysis using augmented Jonscher's power law reveals non-overlapping small polaron tunneling as the dominant mechanism driving both the dielectric response and transport properties, with DC conductivity suggesting a three-dimensional variable range hopping model. These results provide significant insights into the dielectric and transport properties of DCMO, highlighting its promising potential for advanced electronic applications.

Continuous Flow Synthesis of Prussian Blue and Analogues Assisted by AI

AbstractPrussian blue and its analogs are promising materials for numerous applications. Interest in this class of materials arises from their broad pore distribution, redox properties, high biocompatibility, low‐cost components, straightforward manufacturability, and adaptability through analog development. A key challenge is the synthesis of well‐defined, small‐dimensioned materials using machine learning approaches. This study presents a strategy to address this limitation via machine learning‐driven microfluidic synthesis. Employing unsupervised Bayesian optimization with Gaussian processes effectively reduces optimization time and minimizes the need for prior knowledge. As a proof of concept, Prussian blue, and cobalt‐based analogs are synthesized, with UV–vis spectroscopy providing feedback for the machine learning algorithm. The optimized protocols are subsequently applied to larger‐scale preparations, demonstrating that the standardized methods have the potential for the commercial production of high‐quality materials. Comprehensive characterization of the materials confirms their cubic morphology, small dimensionality, and mixed‐valency of the metal elements.

The Emerging of 2D Layer‐Blocked Frameworks

Blocked copolymers are a versatile and powerful class of materials, and their properties can be modified by carefully designing the molecular architecture. Their ability to self‐assemble into nanoscale structures and the multifunctionality make them invaluable in advanced materials science, nanotechnology, and biomedical engineering. Compared to traditional blocked copolymer morphologies such as linear, cyclic, and branched, 2D layer‐blocked frameworks provide materials with clear structure, permanent porosity, favorable chemical and thermal stability, larger surface area, ultra‐high carrier mobility, efficient charge separation and migration, and excellent photoexcitation response. In this concept article, we summarized the design concepts and state‐of‐the‐art strategies for the construction of 2D layer‐blocked frameworks and reviewed the development of some 2D‐like blocked frameworks and their applications in semiconductor, catalysis, energy storage, etc. Finally, we also outlook for the challenges of these materials in preparation and applications across different research fields.

The Synthesis, Characterization, and Theoretical Study of Ruthenium (II) Polypyridyl Oligomer Hybrid Structures with Reduced Graphene Oxide for Enhanced Optoelectronic Applications.

π-conjugated polymers are arguably one of the most exciting classes of materials and have attracted substantial attention due to their unique optical and electronic properties. The introduction of transition metals into conjugated polymers tunes the optoelectronic properties of these metallopolymers, which may improve their performance in device applications. Graphene and reduced graphene oxide (RGO) derivatives are interesting materials with a unique structure and outstanding properties. The present work reports an investigation of three hybrid RGO and π-conjugated oligomers that contain ruthenium polypyridyl chromophores serving as models to provide molecular-level insight for the corresponding transition-metal-containing conjugated polymers.

Assessing Exchange-Correlation Functionals for Accurate Densities of Solids.

The success of Kohn-Sham density functional theory in predicting electronic properties from first-principles is key to its ubiquitous presence in condensed matter research. Central to this theory is the exchange-correlation functional, which can only be written in an approximate form using a handful of exact constraints. A recent criticism of these approximations is that they are designed to give an accurate description of the energy at the expense of a poor representation of the density, which is contrary to the spirit of density functional theory. These conclusions are drawn from studies of atoms or small molecules, where exact results are available. To shed light on this issue, we use the almost exact densities and energies of three prototypical solids (a semiconductor, silicon, an insulator, sodium chloride, and a metal, copper) to compare the performance of exchange-correlation functionals from all rungs of Jacob's ladder. By examining their errors in reproducing both energy and density, we show that several hybrids and semilocal functionals perform consistently well. Furthermore, functionals built to reproduce exact constraints tend to be among the top performers for all tested material classes, strengthening the argument for using these constraints in functional construction. On average, functionals published up to the early 2000s simultaneously improve the prediction of both densities and energies. This is often not the case for more recent functionals, although errors in energy and density continue to evolve in a correlated manner.

Multiple Carbazole-Benzonitrile (CzBN) Derived TADF Molecules Targeting Efficient and Stable Blue OLEDs.

Thermally activated delayed fluorescence (TADF) materials have emerged as a promising avenue for developing efficient and stable blue organic light-emitting diodes (OLEDs) without incorporating heavy metals. Among the numerous donor-acceptor architectures explored, the carbazole (Cz) and benzonitrile (BN) combination has demonstrated exceptional potential for blue OLED applications. Herein, we delve into the recent advances in TADF materials based on the Cz-BN framework, with a particular focus on design strategies to accelerate exciton dynamics and improve material stability through kinetic and thermodynamic optimization. Eventually, challenges associated with the Cz-BN systems in blue OLEDs, as well as prospective research directions that could unlock the full potential of this intriguing category of materials, are also discussed.

Designing van der Waals layers for ferromagnetic quantum spin Hall phase

Most theoretically predicted and experimentally confirmed quantum spin Hall effects (QSHEs) are limited to zero-moment magnets. In this study, we theoretically anticipate the QSHE in ferromagnets and the quantum anomalous Hall effect (QAHE) in antiferromagnets through van der Waals stacked layers, where the magnetization direction is confined to the in-plane. We introduce a search rule for constructing ferromagnetic (FM) quantum spin Hall insulator (QSHI) and antiferromagnetic (AFM) quantum anomalous Hall insulator (QAHI) and further predict a real material of the LuN2/GaS/LuN2 van der Waals multilayer by first-principles calculations. Our results demonstrate the superposition and elimination of Chern numbers under mirror symmetry and time-reversal symmetry, and they further indicate that FM QSHI and AFM QAHI can be converted through deflection magnetization. These findings broaden the material class for QSHE and QAHE and propose a scheme for constructing FM QSHI and AFM QAHI.

Angle of polarized light (AOP) Property for optical classification of the crosslinked polymer

Light-matter interaction has been profoundly studied for sample material classification. However, the optical classification of the sample through the polarized light-matter interaction remains underexplored. It is limited to the measurement of intensity instead of the angle of polarized light (AOP) for its degree of polarization. Measurement of the degree of polarization within a material or a medium becomes easier with a simple, low-cost and direct measurement without the need of any probing or labelling agent. Thus, this investigation was conducted mainly to determine the angle of polarized light (AOP) property of the crosslinked polymer using our proposed polarization measurement technique as an alternative approach of the material classification. The angle of polarized light (AOP) of each polymer was determined in combination property of polarization by absorption, transmission, and scattering. Our proposed scattered angle (ס=90°, 100°, 110°, and 120°) successfully measured the AOP of each polymer that can be classified into two groups. Group 1 represents the AOP value (aopt1-aopn) for a test sample oft1 = 3.1 %, 3.2, and 3.3 % with comparison to the normal sample (n = 3.0 %) and Group 2 represents the AOP value (aopt2-aopn) for the test sample oft2 = 3.4 %, 3.6 % and 3.7 % with comparison to the normal sample (n = 3.0 %). Our study proved a direct, easy, and simple method of determining the degree of polarization of the polymers without the need of complex formulation and labelling protocol. Therefore, this work may enhance the investigation of the optical properties of the agarose-based tissue-mimicking phantom (AGTMP) for modeling or simulation of the real biological sample in the future. Our polarization measures are worthy of further explored and implemented in current optical imaging techniques or sensing platform for optical classification of the biomaterials.

Unified characterization of failure surfaces and golden-ratio ductile-to-brittle classification for isotropic materials

The failure surface, often referred to as the failure angle, defines the specific planar orientation within a material that reaches its load-carrying capacity, represented by material strengths. Analyzing this critical surface is elemental for material characterization, providing profound insights into ductility and brittleness. Despite the diversity of methodologies employed for determining the failure plane from various criteria, a universally accepted theory that systematically governs this characteristic across a broad spectrum of isotropic materials remains elusive. Therefore, this paper aims to develop a unified framework for predicting the failure surface for all homogeneous isotropic solids by considering the convergence of three key material constitutive models: elasticity, failure, and plasticity. A universal energy-based failure criterion is utilized to determine failure angles under fundamental loading scenarios, including uniaxial tension, uniaxial compression, pure shear, and biaxial tension–compression. The sliding, splitting, and crushing behaviors are obtained from the direct and shear strain increments, while the ratio of the two strain increments elucidates the dominant roles in ductile and brittle failure modes. For the first time, the developed theory links the failure angle to Poisson’s ratio, and uniaxial strength properties, unveiling a connection between intrinsic material parameters and extrinsic ductility and brittleness induced by external loadings. The failure angle representing ductile-to-brittle transition under the applied stresses in the principal stress coordinates is shown to be directly related to the golden ratio and independent of loading types. This research addresses longstanding mysteries by providing a deeper understanding of the physics of solids and suggesting potential applications with a phase-field model for predicting the evolving fracture direction.

Optimization of Abrasive Wear Parameters and Thermo-Mechanical Properties of Bauhinia Vahlii and Grewia Optiva Fiber Reinforced Hybrid Polymer Composites

Natural fiber-reinforced polymer composite offers competitive solutions for lightweight applications but faces significant abrasive wear challenges in many industrial and automobile applications. The current study aims to conduct mechanical, physical, and dynamic mechanical analyses, as well as three body abrasion examinations, on grewia-optiva (GO) and bauhinia-vahlii (BV) natural fiber-reinforced epoxy-based hybrid polymer composites containing marble dust as filler. Initially, the woven mat was knitted with an equal amount of grewia-optiva and bauhinia-vahlii natural fibers. Three weight percentages of the woven mat i.e. 10, 20, and 30wt.% were used as reinforcement, and industrial waste marble dust with a fixed amount of 5wt.% was also used as a filler material. GO, and BV fiber mats were chemically treated with 10wt—% NaOH for the cleaning and surface modification of fibers before their use as reinforcement. The fabricated composites' physical and mechanical characteristics, i.e., density, water absorption, hardness, impact, flexural, and tensile strength were examined experimentally. The value of the damping factor (tan δ), storage modulus (Eʹ), and loss modulus (Eʹʹ) of the developed composites were analyzed by a dynamic mechanical analyzer (DMA). The fabricated composites' three-body abrasive wear characteristics were also examined with varying parameters i.e. A: fiber loading, B: sliding distance, and C: normal load. The results show that increasing the fiber loading and using a constant amount of discarded marble dust improves all mechanical characteristics. The tensile strength, flexural strength, impact strength, and hardness improves by 15.99%, 26.30%, 24.40%, and 30.39% respectively for 10wt.% to 30wt.% fiber loading. The composites exhibit significant improvements in damping properties with fiber loading. Moreover, parameters i.e. normal load, speed, and fiber loading have contributed to abrasive wear of composites at 29.70%, 24.81%, and 19.07% respectively. This study will aid in the analysis of the morphological, mechanical, and thermo-mechanical properties of a new class of composite material that might be used for producing natural polymeric roofing systems, boats, and floors, as well as for the automobile industry.

Closed-loop recylcing of thermoset poly(vinylogous urethane) foams

Foams are an intriguing class of porous and lightweight materials which have found widespread applications in thermal insulation, pollutant adsorption, catalyst support, and energy storage. However, their covalently cross-linked structure makes foam unable to be recycled resulting in serious environmental burden. To address this challenge, we report the first example of closed-loop chemically recyclable foam. A simple, catalyst-free cryo-polymerization process with multifunctional amines and acetoacetates was utilized to successfully prepare a series of poly(vinylogous urethane) foams, containing dynamic covalent bonds which can selectively be cleaved on demand. The resulting foams exhibit macroporous structure with diameters exceeding 14 μm, pronounced thermal stability (Td,5% > 262.5 °C), robust hydrophobicity (WCA > 93°) and unique reactivity. Applications have been demonstrated for efficient adsorption of organic solvents and anionic dyes. More importantly, the foams show excellent recyclability under acidic conditions with high monomer recovery yields of up to 97 % and high purity levels. Fresh foams could be regenerated from the retrieved building blocks, thus demonstrating efficient closed-loop recycling. This work provides a new “monomer-foam-monomer” ecological chain and may inspire the advancement of next-generation closed-looped recyclable foam materials.

A new Conjugated mesoporous polymer as fluorescence sensor for the detection of nerve agent simulant dimethyl chlorophosphonate via specific nucleophilic substitution reaction

Conjugated micro/mesoporous polymers (CMPs) represent a category of porous organic materials formed via covalent bonds. Here, DAC-TFP CMP was synthesized using 3,6-diaminocarbazole (DAC) and 2-hydroxy-1,3,5-benzenetricarbaldehyde (TFP) as building blocks. DAC-TFP CMP is a porous conjugation polymer with remarkable thermal and chemical stability. DAC-TFP CMP suspension demonstrates selective "on-off" fluorescence response towards nerve agent simulant dimethyl chlorophosphonate (DMCP) in 1,4-dioxane with exceptionally low detection limits. DMCP and DAC-TFP CMP undergo a nucleophilic substitution reaction, leading to the formation of an N-P bond between N atom on carbazole of DAC-TFP CMP and P atom of DMCP. The new polymer DAC-TFP CMP@DMCP has electron donor-acceptor structure and the fluorescence quenching can be ascribed to the intramolecular charge transfer (ICT) from DAC-TFP CMP unit to DMCP group, as supported by XPS results and DFT calculation. Upon the addition of DMCP to the 1,4-dioxane suspension of DAC-TFP CMP, a subtle blue shift is observed in both the fluorescence emission spectra and UV-vis absorption spectra, providing further validation of the ICT mechanism. DAC-TFP CMP shows excellent recoveries in detecting DMCP in both soil and pesticide samples containing mesotrione and atrazine, highlighting its strong potential as a reliable chemosensor for DMCP detection and analysis.

Enhanced ionic conductivity in Na3Zr2Si2PO12 solid electrolyte via glass addition with low sintering temperature

NZSP (Na3Zr2Si2PO12) stands as a pivotal category of solid-state electrolyte materials in emerging energy devices like solid-state sodium ion batteries (SSSIBs) and solid-state supercapacitors (SSSCs), primarily due to its commendable ionic conductivity at room temperature. However, the high sintering temperatures required to achieve high densities limit the process conditions for applications and increase the energy consumption of the manufacturing process. In this work, we optimized the sintering temperature and obtained high ionic conductivity by incorporating a SiO2-Al2O3-CaO-B2O3 (SACB) glass into NZMSP (Na3.5Zr1.75Mg0.25Si2PO12) ceramics. The results showed that the fluxing of low melting SACB glass increased the cell volume and the bulk density in the matrix material, leading to a significant increase in the grain boundary conductivity of NZMSP. The synthesized ceramic samples (x = 2.1 wt%) maintains high total ionic (∼ 1.65 × 10−3 S/cm) and low electronic conductivities (< 2 × 10−8 S/cm). This work insights into the key role of glass additives in enhancing the properties of sodium ionic conductors, thereby paving the way for the evolution of more efficient and cost-effective processes in advanced ceramic materials.

Cerium oxide anchored free-standing silicon nanowires as potential anode materials for electrochemical supercapacitor

Free-standing 1 D silicon nanowires (Si-NWs) were synthesized by the metal-assisted chemical etching (MACE) technique and subsequently decorated with cerium oxide (CeO2) nanoparticles synthesized by a solvothermal process. Morphological characterization of the CeO2/Si-NWs nanocomposite validates the homogeneous growth of spherical CeO2 nanoparticles around the Si-NWs, while the N2 adsorption-desorption study indicates a large specific surface area (SSA) and the presence of ink-bottle-shaped pores possessing a significant portion of mesopores. This CeO2/Si-NWs composite electrode demonstrates excellent electrochemical behavior, attaining an impressive specific capacitance (Csp) of 830 F g–1 at a current density of 1.0 A g–1, the anodic material delivers an energy density of 19 Wh kg–1 at a power density of 2.5 kW kg–1, along with exceptional durability, retaining 94% of its capacitance after 2000 charge-discharge cycles. The results show that the CeO2/Si-NWs composite electrode has great potential as an emerging category of anodic material for supercapacitors.

Propylene oligomerization over SiO2-overcoated oxides

Catalytic oligomerization of light olefins is an important CC coupling strategy that can be used to produce high-value transportation fuels and chemicals from shale gas and biomass feedstocks. In this work, vapor-phase propylene oligomerization was studied over a series of overcoated SiO2-MOx materials, whose acid site densities and strengths are tunable by the amount of SiO2 deposition and the nature of the core oxide. These materials contain acid sites only on particle external surfaces, limiting pore diffusion artifacts. SiO2-MOx materials were prepared by depositing stoichiometric amounts of tetraethyl orthosilicate (TEOS) onto Al2O3, anatase TiO2, Nb2O5, and ZrO2. Compared to the unmodified oxides, which are poor propylene oligomerization catalysts, the SiO2-MOx materials exhibit moderate activity with Al2O3, TiO2, and Nb2O5 core materials performing better than commercial amorphous silica alumina (ASA) on a surface area basis. The activity of the materials appears to be primarily driven by their Brønsted acid strength as measured by 31P TMPO MAS NMR with the rates ranked in order SiO2/Al2O3 > SiO2/TiO2 ≈ SiO2/Nb2O5 > SiO2/ZrO2. This study shows that SiO2-overcoated materials are a tunable class of materials that are active for vapor-phase propylene oligomerization.

Fracture process zone and fracture energy of heterogeneous soft materials

Bio-inspired heterogeneous soft materials are under rapid development due to their superior fracture and fatigue resistance. In the last few years, several kinds of fibrous soft composites in different length scales have been fabricated. However, the fracture behavior and toughening mechanism of this class of materials are still elusive. Here we develop a theoretical model for the crack tip field of fiber reinforced soft composites. The distribution of deformation around the crack tip and released elastic energy during crack propagation are obtained. The fracture process zone and fracture energy are quantified. There is a critical sample height, below which the fracture process zone size and fracture energy are size-dependent, above which they approach material-specific constants: steady-state fracture process zone size and steady-state fracture energy. A formula is derived to relate the steady-state fracture process zone size and parameters of the composite. It is found that both the steady-state fracture process zone size and the critical sample height scale with the fractocohesive length of the composite. The steady-state fracture energy of the composite can be enhanced either by enlarging the fracture process zone size through tuning fiber geometry or by increasing the work to rupture of the fiber through chemical treatment. This work reveals the toughening mechanism of heterogeneous soft materials and paves the way to design soft materials of high fracture energy, high fatigue threshold, and low hysteresis. It also provides a practical guideline for determining the sample size to measure the steady-state fracture energy of heterogeneous soft materials.