Materials Advances最新文献

Carbon dioxide (CO₂) is reversibly adsorbed and desorbed from ferroelectric (001) oriented, BaO-terminated barium titanate, as revealed in real time by high resolution and ultrafast photoelectron spectroscopy and certified by low energy electron diffraction. Desorption proceeds when the substrate is heated above its Curie temperature. The amount of CO₂ adsorbed is derived to be between one molecule for a surface BaO unit cell (adsorption below room temperature) and one molecule for two unit cells (adsorption above room temperature). The molecule is bound with its carbon to surface oxygen, forming a CO₃ structure. The BaTiO₃(001) surface is unaffected by repeated cycles of adsorption–desorption. The relatively high amount of CO₂ adsorbed and the stability of the substrate after repeated adsorption and desorption processes promotes barium titanate as a promising candidate for decarbonization technologies.

The strong demands on increasing fuel efficiency have continuously driven the optimization of superalloys for high-performance applications. In this study, modifications to the chemistry and heat treatment of HAYNES® 282® alloy (H282) were performed by varying γ′ formers and refractory elements. It was found that increasing Ti and substituting W for some of the Mo in the newly designed alloy (Q) resulted in a significant improvement of creep resistance, up to 130% increase in creep life, compared to standard H282. It was found that Orowan loops and dislocation climb were the dominant creep deformation mechanisms in alloy Q, while extensive dislocation tangling as an additional configuration was observed in the baseline alloy. Moreover, phase stability investigations for up to 5000 h at 800 °C and 900 °C revealed a reduced formation of detrimental σ and μ phases in alloy Q when compared to H282. Atom-probe tomography (APT) revealed that the formation and growth of those phases were responsible for a decrease in Mo content in the matrix, thereby leading to a decrease in solid-solution strengthening in H282 over time. Furthermore, the coarsening of γ′ precipitates was retarded by the substitution of W for Mo, particularly under creep stress. The theoretical and experimental understanding of precipitation strengthening unraveled that higher optimal strengthening occurs at larger particle size for alloy Q, compared to the commercial formulation, further explaining the origin of enhanced creep resistance in the modified alloy.

The ability to tailor the electronic band structure and optical absorption by appropriate cationic substitution in perovskite oxide ferroelectrics is essential for many advanced electronic and optoelectronic applications of these materials. Here, we explored weak (Ba,Ni)-doping for reducing optical bandgaps in (K,Na)NbO₃ ferroelectric films and ceramics. The optical absorption in the broad spectral range of (0.7–8.8) eV was investigated in polycrystalline doped, pure, and oxygen deficient films, in doped epitaxial films grown on different substrates, and in doped ceramics. By comparing optical properties of all films and ceramics, it was established that 1–2 at% of cationic substitutions or up to 10 at % of oxygen vacancies have no detectable effect on the direct (∼4.5 eV) and indirect (∼3.9 eV) gaps. Concurrently, substantial sub-gap absorption was revealed and ascribed to structural band tailing in epitaxial films and ceramics. It was suggested that owing to fundamental strain-property couplings in perovskite oxide ferroelectrics, inhomogeneities of lattice strain can lead to increased sub-gap absorption. The uncovered structurally induced sub-gap optical absorption can be relevant for other ferroelectric ceramics and thin films as well as for related perovskite oxides.

The direct conversion of methane to methanol has attracted increasing interests, owing to the necessity for an abundant low-carbon source of energy. However, numerous challenges are encountered in attaining a high conversion rate and selectivity using the existing approach and catalysts. One of them is the need for a reaction halt and a reactivation of the catalyst using an oxidant at high temperature, which makes the whole process non-cyclic. In this study, we employ density functional theory calculations to evaluate rutile-type IrO₂(110), β-PtO₂(110), and β-MnO₂(110) surfaces not only for cleaving the H–CH₃ bond but also for forming methanol. We find that IrO₂(110) and β-PtO₂(110) thermodynamically and kinetically favor the C–H activation on the bridging μO-atom terminations via a heterolytic pathway. However, the formation of strong Ir–C and Pt–C bonds, which initially help the C–H bond scission, hinders the methanol formation. In the β-MnO₂(110) case, in contrast, the Mn–C interaction is quite weak, and the Mn(μ-O)Mn active site is electrophilic, thus allowing the formation of a stable ˙CH₃ radical intermediate state that becomes the driving force for a low-barrier homolytic C–H bond scission as well as a low-barrier and highly exothermic formation of methanol. This first cycle of methane oxidation results in a reduced β-MnO₂(110) surface, where no more μ-O active sites are available for the subsequent cycles of methane activation. Nonetheless, this reduced surface can also oxidize methane to methanol when the H₂O₂ oxidant is inserted in the mid-way reaction and forms new active sites of μ-OH. The second reaction is also highly exothermic although the C–H activation barrier is not as low as that for the fresh stoichiometric surface. This study suggests the β-MnO₂(110) surface as a potential catalyst for the cyclic oxidation of methane to methanol using the H₂O₂ oxidant without halting for reactivation.

In recent years, ZnIn₂S₄ (ZIS) has garnered attention as a promising photocatalyst due to its attractive properties. However, its performance is hindered by its restricted range of visible light absorption and the rapid recombination of photoinduced holes and electrons. Single-atom co-catalysts (SACs) can improve photocatalytic activity by providing highly active sites for reactions, enhancing charge separation efficiency, and reducing the recombination rate of photo-generated carriers. In this work, we perform high-throughput density functional theory (DFT) computations to search for SACs in ZIS encompassing 3d, 4d, and 5d transition metals as well as lanthanides, considering both substitutional and interstitial sites. For a total of 172 SACs, defect formation energy (DFE) is computed as a function of chemical potential, charge, and Fermi level (E_F), leading to the identification of low energy dopants and their corresponding shallow or deep defect levels. Statistical data analysis shows that DFE is highly correlated with the difference in electron affinity between the host (Zn/In/S) atom and the SAC, followed by the electronegativity and boiling point. Among the 60 lowest energy SACs, Co_In, Yb_i, Tc_Zn, Au_S, La_i, Eu_i, Au_i, Ta_In, Hf_In, Zr_In, and Ni_Zn lead to a lowering of the Gibbs free energy for hydrogen evolution reaction, improving upon previous ZIS results. The computational dataset and insights from this work promise to accelerate the experimental design of novel dopants in ZIS with optimized properties for photocatalysis and environmental remediation.

Bone defects represent a significant clinical challenge, traditionally addressed primarily through scaffold-based repair strategies. However, recent studies have revealed that relying solely on scaffolds may not fully overcome the bottlenecks in bone defect repair. Mounting evidence suggests that modulating the inflammatory response plays a crucial role in the bone healing process. While moderate inflammation can promote bone tissue regeneration, excessive or prolonged inflammatory responses may impede the repair process. Our previously developed calcium silicate (CS) scaffold, known to stimulate osteoblast proliferation and accelerate bone tissue formation, was enhanced with magnesium–strontium to boost cellular biological activity and foster bone formation and angiogenesis. In this study, the effects of 3D-printed CS scaffolds reinforced with astragalus (Ast) on inflammation regulation and osteogenic gene expression were examined. X-ray diffraction and Fourier transform infrared spectroscopy confirmed that the Ast phase structure and chemical functional groups were added to the materials. The findings revealed that integrating Ast improves scaffold biocompatibility, bioactivity, and bone and vascular tissue formation efficacy, enhances mechanical strength, and decelerates biodegradation. The 5% Ast-containing CS scaffold exhibited superior capabilities in promoting cell proliferation and differentiation, indicative of effective bone regeneration. Moreover, analysis of hMSC-seeded AstCS scaffold supernatants revealed significantly reduced levels of pro-inflammatory cytokines IL-1β and IL-6, coupled with elevated expression of the anti-inflammatory factor IL-1RA. These results suggest that Astragalus incorporation effectively modulates inflammatory signaling in the scaffold microenvironment. Transcriptome RNA sequencing revealed that this scaffold modulated multiple signaling pathways crucial for bone regeneration, such as WNT, AKT, and PI3K, and significantly influenced genes associated with cellular bone regeneration, angiogenesis, and immune responses. These results highlight the potential of combining Ast with CS in 3D-printed scaffolds for bone tissue engineering, offering new strategies for employing natural pharmaceutical ingredients as bioactivity enhancers and providing a substantial foundation for designing future bone regeneration materials with immune-modulating capabilities.

Recent reports have shown that nickel oxide (NiO) when adopted as a hole transport layer (HTL) in combination with organic layers, such as PTAA or self-assembled monolayers (SAMs), leads to a higher device yield for both single junction as well as tandem devices. Nevertheless, implementing NiO in devices without PTAA or SAM is seldom reported to lead to high-performance devices. In this work, we assess the effect of key NiO properties deemed relevant in literature, namely- resistivity and surface energy, on the device performance and systematically compare the NiO-based devices with those based on PTAA. To this purpose, (thermal) atomic layer deposited (ALD) NiO (NiO_Bu-MeAMD), Al-doped NiO (Al:NiO_Bu-MeAMD), and plasma-assisted ALD NiO (NiO_MeCp) films, characterized by a wide range of resistivity, are investigated. Although Al:NiO_Bu-MeAMD (∼400 Ω cm) and NiO_MeCp(∼80 Ωcm) films have a lower resistivity than NiO_Bu-MeAMD (∼10 kΩ cm), the Al:NiO_Bu-MeAMD and NiO_MeCp-based devices are found to have a modest open circuit voltage (V_OC) gain of ∼30 mV compared to NiO_Bu-MeAMD-based devices. Overall, the best-performing NiO-based devices (∼14.8% power conversion efficiency (PCE)) still lag behind the PTAA-based devices (∼17.5%), primarily due to a V_OC loss of ∼100 mV. Further investigation based on light intensity analysis of the V_OC and FF and the decrease in V_OC compared to the quasi-Fermi level splitting (QFLS) indicates that the V_OC is limited by trap-assisted recombination at the NiO/perovskite interface. Additionally, SCAPS simulations show that the presence of a high interfacial trap density leads to a V_OC loss in NiO-based devices. Upon passivation of the NiO/perovskite interface with Me-4PACz, the V_OC increases by 170–200 mV and is similar for NiO_Bu-MeAMD and Al:NiO_Bu-MeAMD, leading to the conclusion that there is no influence of the NiO resistivity on the V_OC once interface passivation is realized. Finally, our work highlights the necessity of comparing NiO-based devices with state-of-the-art HTL-based devices to draw conclusion about the influence of specific material properties on device performance.

Reactive oxygen species (ROS)-mediated photooxidation is an efficient method for triggering a drug release from liposomes. In addition to the release of small molecules, it also allows the release of large macromolecules, making it a versatile tool for controlled drug delivery. However, the exact release mechanism of large macromolecules from ROS-sensitive liposomes is still unclear. There are no studies on the effect of lipid oxidation on the release of cargo molecules of different sizes. By using HPLC-HRMS method we analyzed the oxidation products of ROS-sensitive DOTAP lipid in phthalocyanine-loaded DOTAP:Cholesterol:DSPE-PEG liposomes after 630 nm light irradiation of different durations. Shorter illumination time (1–2 minutes) led to the formation of hydroperoxides and vic-alcohols predominantly. Longer 9-minute irradiation resulted already in aldehydes generation. Interestingly, the presence of epoxides/mono-hydroperoxides and vic-alcohols in a lipid bilayer ensured a high 90% release of small hydrophilic cargo molecules i.e. calcein, but not large (≥10 KDa) macromolecules. Oxidation till aldehydes was mandatory to deliver e.g. dextrans of 10–70 kDa with ca. 30% efficiency. Molecular dynamics simulations revealed that the formation of aldehydes is required to form pores or even fully disrupt the lipid membrane, while e.g. presence of hydroperoxides is enough to make the bilayer more permeable just for water and small molecules. This is an important finding that shed a light on the release mechanism of different cargo molecules from ROS-sensitive drug delivery systems.

We immobilised colloidal palladium nanoparticles on poly(N-vinylacetamide). The polymer and the immobilised Pd NPs were characterised with characterisation methods such as transmission electron microscopy, dynamic light scattering, thermogravimetric analysis, Fourier-transform infrared spectroscopy, X-ray absorption spectroscopy, and X-ray photoelectron spectroscopy. Finally, we tested catalytic applications under Suzuki–Miyaura cross-coupling reaction conditions.

We report the development of peptide-glycosaminoglycan hydrogels as injectable biomaterials for load-bearing soft tissue repair. The hydrogels are injectable as a liquid for clinical delivery, rapidly form a gel in situ, and mimic the osmotic swelling behaviour of natural tissue. We used a new in vitro model to demonstrate their application as a nucleus augmentation material for the treatment of intervertebral disc degeneration. Our study compared a complex lab gel preparation method to a simple clinical benchtop process. We showed pH differences did not significantly affect gel formation, and temperature variations had no impact on gel performance. Rheological results demonstrated consistency after benchtop mixing or needle injection. In our in vitro disc degeneration model, we established that peptide augmentation could restore the native biomechanical properties. This suggests the feasibility of minimally invasive peptide-GAG gel delivery, maintaining consistent properties across temperature and needle sizes while restoring disc height and stiffness in vitro.