Materials Advances最新文献

The development of efficient and durable catalysts for the oxygen evolution reaction (OER) is urgent for renewable and sustainable energy storage and conversion. High-entropy oxides (HEOs) have gained significant attention for OER electrocatalysis owing to their multielement synergy and tunable electronic structure. The presence of multiple cations and anions in HEOs’ crystal structure leads to a slow diffusion effect, lattice distortion, high configurational entropy, and cocktail effect. The high configurational entropy of HEOs reveals outstanding electrochemical activity due to the large number of active sites compared with their individual counterparts. Herein, a series of equimolar (quaternary, quinary, and senary) and non-equimolar HEOs were fabricated using a rapid microwave irradiation method. The crystal structure, morphology, elemental composition and oxidation states of the HEOs were explored via different physical characterizations. The OER activity of the HEOs was investigated through cyclic voltammetry (CV), linear sweep voltammetry (LSV), chronoamperometry, and electrochemical impedance spectroscopy (EIS). All the prepared HEOs demonstrated outstanding OER activity, where the optimum composition exhibited a low overpotential of 350 mV, Tafel slope of 49.4 mV dec⁻¹ at 10 mA cm⁻² and excellent stability for 3600 s. Other electrocatalytic parameters including high diffusion coefficient (D°) (2.2 × 10⁻⁸ cm² s⁻¹), mass transport coefficient (m_T) (2.9 × 10⁻⁴ cm s⁻¹), heterogeneous rate constant (k°) (5.85 × 10⁻⁴ cm s⁻¹), high active surface area (A) (0.0116 cm²), and turnover frequency (TOF) (1.388 s⁻¹) were observed for optimized composition. EIS analysis revealed low solution resistance and charge transfer resistance values. This outstanding performance is attributed to multiple cationic contribution due to the synergistic effect, high durability, improved conductivity, and high entropy stabilization. However, the electrochemical behavior of HEOs depends on each metal ion and its concentration on the catalyst's surface, thus providing new opportunities for tailoring their functional properties by simply changing their elemental composition for different electrochemical applications.

Global concerns are increasing worldwide owing to the utilization of non-renewable fossil fuel-derived polymeric films for the packaging of perishables and other related commodities. The emergence of bio-based packaging films, characterized by affordability, environmental friendliness, and abundant renewable sources, offers a promising alternative to address these concerns. This study aims to mitigate the adverse impacts associated with petroleum-based films by developing an effective bio-nanocomposite with enhanced mechanical and barrier properties. The developed composite, achieved through the incorporation of montmorillonite (MMT) nanoclay into two distinct biopolymer blends (chitosan–xanthan gum and chitosan–vanillin), was further optimized to determine the optimal ratio. The bio-nanocomposite film with 3% nanoclay reinforcement in the chitosan–vanillin blend demonstrated superior performance compared to all other films. In contrast to an untreated chitosan film, this bio-nanocomposite exhibited reduced transmittance, mitigating oxidative damage from UV radiation in packaged food items. Notably, a substantial improvement in water resistance and a remarkable 6.64-fold increase in tensile strength were observed. The film's biodegradability, as evidenced by a 25% weight loss in the first month in a soil burial test, underscores its environmental friendliness. Results from a range of instrumental techniques and measurements collectively suggest that the synthesized and optimized film has significant potential for application in the future sustainable food-packaging industry.

Porous silicone polymer composites (elastomeric foams) with tunable properties and multifunctionalities are of great interest for several applications. However, the difficulties in balancing functionality and printability of silicone polymer based composite resins hinder the development of 3D printed multifunctional porous silicone materials. Here, the direct ink write (DIW) technique and NaCl filler as a sacrificial template were utilized to develop 3D printed porous silicone composites. Three different fillers (hydrophilic and hydrophobic fumed silica, and carbon nanofibers (CNF)) were used to impart additional functionality and to explore their effects on the rheology of the DIW resin, and the mechanical properties of the 3D printed elastomeric foams. While hydrophilic silica was effective in modulating the rheology of the resin, CNFs were effective in improving the tensile strength of the elastomeric foam. Unlike tensile strength, which was found to be dependent on filler type, the uniaxial compressive behavior was found to be more dependent on the porosity of the elastomeric foams. A hyperelastic constitutive model (the Compressive, Hyperelastic, Isotropic, Porosity-based Foam model) was used to simulate the uniaxial compressive behavior of the elastomeric foams, and the model accurately reproduced the experimental stress–strain profiles. The expanded design flexibility of tunable porosity in DIW parts enables the foams to be utilized in a wider variety of applications. For example, the foam with CNF filler demonstrated excellent oil/water separation capacity, with absorbing efficiencies of 450% and 330% respectively for chloroform and toluene. Similarly, a foam with hydrogen getter capacity was developed using the CNF filled foam with hydrogen getter as an additional functional filler, and high performance of the 3D printed hydrogen getter composite was demonstrated.

Rare-earth double tungstate NaEu(WO₄)₂ was synthesized via a trisodium citrate (Na₃cit)-assisted hydrothermal technique, followed by calcination, to promote crystallinity and detailed investigations on their crystal structures and luminescence properties. In this study, the structural evolution of our samples synthesized with different amounts of Na₃cit was studied by employing X-ray diffraction, Rietveld refinement, Fourier transform infrared and Raman spectroscopy techniques. It was found that NaEu(WO₄)₂ belongs to the scheelite family with Na and Eu atoms occupying the same sites and antisite defects deforming EuO₈ dodecahedra. The modulation of W–O, Eu–O and angle splitting in the presence of antisite defects was identified. From in-depth X-ray photoelectron spectroscopy, we validated the deformation of the EuO₈ dodecahedron due to the presence of oxygen vacancies (V_Os), which originated from antisite defects. Herein, we show that the band gap of NaEu(WO₄)₂ is highly sensitive to defects; however, the ⁵D₀–⁷F₂ transition of Eu³⁺ at 615 nm with color coordinates (0.67, 0.33) is very robust, making NaEu(WO₄)₂ a suitable red phosphor material for near UV-type light-emitting devices (LEDs). We also identified that V_Os present in the EuO₈ dodecahedron act as active sites for acetone sensing (∼68% response to 100 ppm) with a response and recovery time of ∼3.3/10 s at room temperature, suggesting the potency of NaEu(WO₄)₂ as a multifunctional material with applications in LEDs and acetone sensors. In order to validate our experimental observations theoretically, we calculated the band structure and density of states of bare and antisite defects containing NaEu(WO₄)₂ using ab initio density functional theory and identified the sensing mechanism. We believe that our studies will be helpful in introducing new multifunctional applications of NaEu(WO₄)₂, while theoretical calculations will provide new electronic insights that may be used to understand the features of other double rare-earth tungstate materials.

Electrocatalysis presents an efficient and eco-friendly approach for the two-electron oxygen reduction reaction (2e⁻ ORR) to produce hydrogen peroxide (H₂O₂). However, challenges persist in enhancing catalyst activity and refining design strategies. In this study, a general four-step strategy is introduced to develop efficient single-atom catalysts (SACs) for H₂O₂ production based on transition metals and nonmetals embedded into γ-graphyne monolayers (TM–NM–GY) through first-principles calculations. Our results indicate that the intrinsic activity for the 2e⁻ ORR can be properly and handily evaluated using the robust intrinsic electronegativity descriptor. On this foundation, we propose two strategies of B doping and creating C vacancies (v) to further enhance catalytic activity. Remarkably, Ni–B–GY and Ag–v–GY exhibit exceptional selectivity, stability, and activity with overpotentials as low as 0.08 V and 0.15 V, respectively, approaching the ideal limit of H₂O₂ catalysts. Mechanistic investigations reveal that B doping facilitates electron transfer and strengthens the hybridization between Ni 3d and O 2p orbitals, leading to stronger adsorption strength of *OOH and thus enhancing the 2e⁻ ORR catalytic performance. These findings not only present several promising SAC candidates for H₂O₂ production, but also pave the way for the rational design of highly efficient SACs for various catalytic reactions.

Conductive hydrogel-based soft devices are gaining increasing attention. Still, their dependence on water makes them susceptible to freezing and drying, which affects their long-term stability and durability and limits their applications under subzero temperatures. Developing hydrogels that combine exceptional strength, high strain sensitivity, anti-freezing properties, synchronous sensing, durability, and actuating capabilities remains a significant challenge. To overcome these issues, a universal solvent replacement strategy (USRS) was adopted to fabricate anti-freezing and anti-drying organohydrogels with ultra stretchability and high strain sensitivity in a wide temperature range. Ethylene glycol (Eg) and glycerol (Gl) were used as secondary solvents to replace water (primary solvent) from the hydrogel network. Due to the strong hydrogen bonding capabilities of Eg and Gl with water and the hydrogel network, the organohydrogels formed show resistance to freezing and drying. This allows the organohydrogels to maintain conductivity, sensitivity, stretchability, and durability under subzero temperatures. The developed organohydrogels display remarkable stretchability (850%), good electrical conductivity (0.45 S m⁻¹), exceptional anti-freezing performance below −90 °C and very high sensitivity (GF = 10.14). Additionally, the strain sensor demonstrates a notably wide strain range (1–600%) checked within the temperature range of −15 °C to 25 °C. It also effectively monitors various human movements with differing strain levels, maintaining good stability and repeatability from −15 to 25 °C. It is also believed that this strain sensor can work efficiently above and below the mentioned temperature range. This study introduced a straightforward approach to developing conductive organohydrogels with outstanding anti-freezing and mechanical properties, demonstrating significant potential for use in wearable strain sensors and soft robotics.

The present study introduces Trigonella foenum-graecum (TFG, fenugreek)-mediated Co₃O₄ nanoparticles (NPs) as an innovative solution for eliminating industrial azo dyes from contaminated water. The novelty lies in their rapid, cost-effective synthesis and excellent photocatalytic and antimicrobial performance, which mark a significant advancement in environmental remediation. The NPs are synthesized using a co-precipitation method and characterized through advanced techniques. UV-visible absorption spectroscopy revealed two prominent direct bandgap transitions, surpassing previous reports and enhancing light absorption for efficient photocatalysis. FTIR analysis confirmed the successful incorporation of TFG phytochemicals, while XRD and SAED patterns indicated high crystallinity, a small crystallite size (1.6 nm), and ultrafine average particle size (5.5 nm) as observed by HRTEM. XPS analysis validated the synthesis with controlled oxidation states and defect sites featuring Co²⁺ and Co³⁺ ions. The optimized synthesis process led to outstanding photocatalytic performance, achieving 100% degradation of Congo red dye in just 60 minutes at a concentration of 120 mg L⁻¹. This efficiency underscores their capability to treat CR-contaminated water under specific conditions. The synergy between TFG phytochemicals and Co₃O₄ NPs demonstrates significant potential for water pollution remediation. Additionally, these NPs exhibit strong antimicrobial activity against Gram-negative and Gram-positive bacteria, highlighting their broader environmental significance and potential applications in various ecological fields.

A novel red-emitting scintillator Li₂MnCl₄ is proposed as a candidate for thermal neutron detection. It features high Li content, low density, a low effective atomic number, and emission in the red-NIR region. These characteristics make it an interesting candidate for long-distance neutron detection in harsh environments e.g. decommissioning of nuclear power plants. The absorption is thoroughly investigated in the scope of the Tanabe–Sugano diagram. The luminescence mechanism in undoped Li₂MnCl₄ is studied in depth using steady-state and time-resolved photoluminescence. Doping with Eu²⁺ and Ce³⁺ is introduced as a trial to improve the scintillation efficiency. We show that in the Eu²⁺ and Ce³⁺ doped Li₂MnCl₄ the luminescence mechanism involves energy transfer from the dopants to Mn²⁺, and propose the local lattice distortion around the dopant and possible charge compensation mechanisms.

In spite of remarkable advancements in tissue engineering and regenerative medicine in recent years, a notable gap remains in the availability of economically feasible and efficient treatments to address the hypoxic conditions within wounds. This perspective delves into cutting-edge strategies leveraging autotrophic tissue engineering for regenerative medicine, and provides new pathways for wound healing and repair. Autotrophic tissue engineering harnesses the innate photosynthetic ability of algae to provide optimal oxygen levels within cell-seeded scaffolds. This innovative approach attempts to fabricate tissue constructs endowed with self-sustainability. It also reduces the dependence on external nutrient sources, and seeks to produce functional scaffolds suitable for 3D bioprinting applications. Similarly, we envision a creative design approach focused on devising a novel methodology to functionalize carbon quantum dots (CQDs) with fucoidan derived from algae through click chemistry.

The electrical conductivity of powdered carbon aerogels is one of the key factors required for electro-chemical applications. This study investigates the correlation between the structural, physical, mechanical and electrical properties of pure and activated carbon aerogels, as well as aerogel-composites. The thermal activation with carbon dioxide led to higher electrical conductivity and a decrease in density and particle size. Furthermore, the influence of applied force, compressibility of aerogels and aerogel composites on electrical conductivity was studied. A number of different carbonaceous powdered additives with various morphologies, from almost spherical to fiber- and flake-like shaped, were investigated. For two composites, theoretical values for conductivity were calculated showing the great contribution of particle shape to the conductivity. The results show that the conductive behavior of composites during compression is based on both the mechanical particle arrangement mechanism and increasing particle contact area.