Advanced Materials Interfaces最新文献

Chemically modified graphene is an attractive electrode material for electrocatalysis, energy devices, and sensors, whereas pristine graphene is electrochemically passive. The remarkable anisotropic electrochemical nature of graphene is uncovered by π–π interaction, making pristine graphene more active than bare Au. The π–π stacking during redox reaction “dopes” the graphene, disrupting the passivating hydration layer, making it a facile electrochemical electrode. The structure during π–π stacking-mediated redox of methylene blue (MB) is quantitatively measured by the differential reflectivity of a polarized laser on a ≈100 micron spot. The local redox reaction current varies over fourfold due to the orientation of the ≈10 micron size grains. The mosaic-grain anisotropy on each spot shows local uniaxial orientation. The redox signal at the optimum orientation is over 2.5-fold greater than that for bare Au on the same electrode. The redox signal is over fivefold greater at the edges of graphene compared bare Au. Remarkably, the π–π interaction increases chemical stability significantly, leading to negligible photo-degradation at the approximate absorption wavelength of MB. The exclusive redox activity due to π–π interaction on pristine graphene adds to the toolbox of making exotic opto-electrochemical electrode materials for electrocatalysis, sensing, and electronics.

This work focuses on combating bacterial infections in bone tissue using metal elements embedded in bioactive glass. While there is an urgent need for alternative methods with a shrinking number of effective treatment options untouched by antimicrobial resistance, it is crucial to first understand the mechanisms of pathogenesis, persistence, and bacterial resistance in skeletal infection, and then develop effective counterstrategies and innovative alternatives. This review considers the role of antimicrobial metal ions, their mechanism of action, and their incorporation into bioactive glass formulations as these materials can serve as delivery platforms with the least possible complexities. Furthermore, the bacterial infection risk in bone is also examined with specific attention to antibiotic resistance and biofilm formation. This review sheds light on the most promising materials as novel antibacterial agents by presenting a wide range of possible bioactive glass formulations equipped with potential antibacterial ions and in vitro/ in vivo insights, and it also reinforces the importance of continuing studies to develop multi-faceted antibacterial bioactive glasses.

This work presents a study of piezoelectric zinc oxide (ZnO) thin films deposited by a novel post-reactive sputtering method. The process utilizes a rotating drum with DC magnetron sputtering deposition onto substrates with subsequent DC plasma-assisted oxidation of the deposited metal to metal oxide. The paper analyzes the influence of plasmaassisted magnetron sputtering (PA-MS) deposition parameters (O₂ plasma source power, O₂ flow, and Ar flow) on the morphological, structural, optical, and piezoelectric properties of ZnO thin films. Design of experiments has been utilized to evaluate the role of these parameters on the growth rate (r_g) and the properties of resulting films. Results indicate a predominant influence of the plasma power on the r_g over other parameters. Among the eight tested samples, three of them show high crystal quality with high intensity (0001) diffraction peak, characteristic of the wurtzite crystalline structure of ZnO, and one of them exhibits piezoelectric coefficient values of ≈11pC N⁻¹. That sample corresponding to a ZnO film deposited at the lowest r_g of 0.075 nm s⁻¹, confirmed the key role of the deposition parameters on the piezoelectric response of films, and demonstrated PA-MS as a promising technique to produce high-quality piezoelectric thin films.

Bifunctional Catalysts

Cobalt ferrite nanoparticle catalysts generated from homoleptic iron and cobalt urea complexes and deposited onto dahlia like arrangements of nitrogen doped carbon nanohorns are shown on the le: side. These carbon/ferrite composites convert molecular oxygen into hydroxyl ions and back to oxygen (right side) and are thus efficient catalysts to drive a secondary zinc/air battery with high efficiency. More details can be found in article 2400415 by Jörg J. Schneider and co-workers. Image art by Dr. Sherif Okeil.

Hydrogel Reaction Trap

The cover image of the article 2400341 by Kwanwoo Shin and co-workers showcases a simple, cost-effective method to enhance the sensitivity of lateral flow assay (LFA) kits. By using a drop-casting process to apply a hydrogel reaction trap, the flow rate and reaction time are optimized, significantly boosting diagnostic performance. This method can increase the sensitivity of commercial LFA kits by up to sevenfold.

The diffusion of potassium in SrTiO₃ (STO) single crystals is investigated as a function of temperature. Charge attachment induced transport experiments are employed inducing diffusion profiles in STO evolving with time. Potassium concentration profiles, characterized ex-situ by ToF-SIMS depth profiling, exhibited a bimodal shape indicating two different transport pathways. Two diffusion coefficients are obtained for the two profiles. Their temperature dependence is described using an Arrhenius approach, allowing two activation energies to be derived from the data set. Utilizing DFT+U, the ionic mobility of potassium along the crystal structure is simulated and activation energies are determined for every trajectory. The transport pathway with the larger diffusion coefficient is assigned to defect transport, most likely via Sr vacancies. The transport pathway exhibiting the lower diffusion coefficient is assigned to interstitial transport. In addition, the experiment is repeated on a bicrystalline STO sample to investigate the effect of a grain boundary on the ionic conductivity of the sample. As expected, the grain boundary represents an additional diffusion path for the potassium ions. The corresponding diffusion coefficient along the grain boundary is three orders of magnitude larger than that for bulk diffusion. Atomically resolved structural information in the grain boundary region is presented.

Magnetic vortices are topological spin structures frequently found in ferromagnets, yet novel to antiferromagnets. By combining experiment and theory, it is demonstrated that in a nanostructured antiferromagnetic-ferromagnetic NiO(111)-Fe(110) bilayer, a magnetic vortex is naturally stabilized by magnetostatic interactions in the ferromagnet and is imprinted onto the adjacent antiferromagnet via interface exchange coupling. Micromagnetic simulations are used to construct a corresponding phase diagram of the stability of the imprinted antiferromagnetic vortex state. The in-depth analysis reveals that the interplay between interface exchange coupling and the antiferromagnet magnetic anisotropy plays a crucial role in locally reorienting the Néel vector out-of-plane in the prototypical in-plane antiferromagnet NiO and thereby stabilizing the vortices in the antiferromagnet.

Photoelectrolysis of water is a sustainable option for the production of hydrogen fuel. GaN nano- or microstructures are considered for water-splitting due to their general high chemical stability and high surface-to-volume ratio enhancing the process effectiveness. In this study GaN structures with dodecagonal microrods are used as a working electrode for the water-splitting process. Microrods are grown using a plasma-assisted molecular beam epitaxy process allowing tailoring of microrod height and density. Their unique property is the of presence twelve sidewalls with alternating a- and m-plane orientations. This enables a simultaneous study of the chemical stability of c-, a-, and m-plane walls of GaN. The water-splitting process is performed using a 1 mol l⁻¹ NaOH electrolyte solution. Non-zero current measured at zero bias under illumination indicates that the process takes place. A degradation of the GaN structure is observed after a prolonged process time. In short-term exposures, etching of microrod sidewalls is observed. Roughening of the a-plane walls studied by transmission electron microscopy indicates that this orientation is etched with a fastest rate. The internal crystalline structure is not influenced by the etching and remains stable as shown by the X-ray absorption spectroscopy study.