材料科学最新文献

Structural Color Materials with Color Mixing Effect

Structural color materials with a color mixing effect using SiO₂–ZrN core–shell particles, where ZrN nanoparticles used as shell exhibit localized surface plasmon resonance, were developed by Shinji Noguchi, Kiyoharu Tadanaga, and co-workers (see article number 2400287). The particle-stacked films can be a material that exhibits a “color mixing effect” that combines specific wavelength absorption through plasmon resonance and specific wavelength diffraction by the periodic structure without using precious metals. These offer the potential to be optical materials for tuning the reflection and absorption spectra.

Nanoparticles

In article 2400107, Matteo Tollemeto and co-workers present a systematic and comprehensive study through a multidisciplinary approach combining conventional and novel techniques for in vitro studies to understand the key molecular interactions between nanoparticles and mucin. Cover art design by Matteo Tollemeto, Eleftheria Pantazoglou and the team of Inmywork Studio.

We report hydrostatic pressure-induced reversible phase transformation in maghemite γ-Fe₂O₃ nanoparticles (cubic → tetragonal → cubic) using an in situ diamond anvil cell (DAC) technique. Thermal arc plasma-synthesized nanoparticles, particularly in a He gas medium, exhibit the reversible phase transformation under pressure ranging from 0 to 2.58 GPa. Rietveld refinement reflects that cubic to tetragonal maghemite phase transformation coexists with a cubic metallic Fe phase at 0.55 GPa pressure. The generation of two new superlattice reflections at 6.93° and 8.11°, respectively, reflects the phase transformation. The presence of a core-shell-type nanostructure observed from transmission electron microscopy micrographs is found to exhibit a spin glass shell-type behavior. This triggers pressure-induced fluctuating magnetization and interparticle interaction-induced surface anisotropy and spin disorder with broken bonds, translational symmetry, and incomplete coordination. This leads to overcoming the nucleation barrier at the surface, subsequently denser nucleation sites and increased nucleation probability. This further leads to an atomic rearrangement and tetragonality in the maghemite phase. Furthermore, with increasing pressure, the reversible structural change, i.e. from the tetragonal to cubic maghemite phase, has been explained in the light of the "internal stress model". The grains are again forced back to the cubic phase via generation of uniform compression along the c-axis and tension along the a and b axes. The spin glass behavior of the core-shell nanostructure along with the "internal stress model" explain the whole reversible phase transformation phenomenon in the γ-Fe₂O₃ phase.

Perovskite quantum dots (PQDs) have attracted emerging attention as fluorescent and light-absorbing materials for next-generation optoelectronics due to their outstanding properties and cost-efficiency. However, PQD thin film suffers significant instability due to structure and material failures, which hinders their application in flexible and reliable PQD-based advanced wearable devices. Herein, we use commercial cellulose fiber-based filter paper as a substrate to synthesize PQDs in situ and fabricate PQD-paper free-standing flexible composite film. The abundant hydroxy capping ligands of cellulose fibers and the unique dense network structure of the filter paper can facilitate confined crystallization, forming strong interactions between the PQDs and substrate, the unpackaged PQD composite film showed extraordinary stability (>30 days) in the air with high humidity (90%). Meanwhile, the strong interaction between PQDs and paper enables an ultrasimple drop-cast synthesis process with excellent process tolerance, making it customizable and easy to scale up (10 cm in diameter). Due to the uniformly dispersed PQDs on cellulose fibers of the substrate, the composite demonstrates impressive photo-responsive properties. Photodetector (PD) arrays were designed on free-standing PQD paper and flexible graphitic electrodes, and circuits were fabricated by drawing. The PD arrays can work as optical and electrical dual-mode image sensors with incredible bending robustness, enduring up to 100,000 cycles at 180°.

We would like to take this opportunity to thank all of Nanoscale Horizons' reviewers for helping to preserve quality and integrity in the nanoscience literature. We would also like to highlight the Outstanding Reviewers for Nanoscale Horizons in 2023.

Nanostructures of some metals can sustain localized surface plasmon resonances, collective oscillations of free electrons excited by incident light. This effect results in wavelength-dependent absorption and scattering, enhancement of the incident electric field at the metal surface, and generation of hot carriers as a decay product. The enhanced electric field can be utilized to amplify the spectroscopic signal in surface-enhanced Raman scattering (SERS), while hot carriers can be exploited for catalytic applications. In recent years, cheaper and more earth abundant alternatives to traditional plasmonic Au and Ag have gained growing attention. Here, we demonstrate the ability of plasmonic Mg nanoparticles to enhance Raman scattering and drive chemical transformations upon laser irradiation. The plasmonic properties of Mg nanoparticles are characterized at the bulk and single particle level by optical spectroscopy and scanning transmission electron microscopy coupled with electron energy-loss spectroscopy and supported by numerical simulations. SERS enhancement factors of ∼10² at 532 and 633 nm are obtained using 4-mercaptobenzoic acid and 4-nitrobenzenethiol. Furthermore, the reductive coupling of 4-nitrobenzenethiol to 4,4'-dimercaptoazobenzene is observed on the surface of Mg nanoparticles under 532 nm excitation in the absence of reducing agents, indicating a plasmon-driven catalytic process. Once decorated with Pd, Mg nanostructures display an enhancement factor of 10³ along with an increase in the rate of catalytic coupling. The results of this study demonstrate the successful application of plasmonic Mg nanoparticles in sensing and plasmon-enhanced catalysis.

Solid oxide electrolysis cells (SOECs) show significant promise in converting CO₂ to valuable fuels and chemicals, yet exploiting efficient electrode materials poses a great challenge. Perovskite oxides, known for their stability as SOEC electrodes, require improvements in electrocatalytic activity and conductivity. Herein, vanadium(V) cation is newly introduced into the B-site of Sr₂Fe_1.5Mo_0.5O_6-δ perovskite to promote its electrochemical performance. The substitution of variable valence V⁵⁺ for Mo⁶⁺ along with the creation of oxygen vacancies contribute to improved electronic conductivity and enhanced electrocatalytic activity for CO₂ reduction. Notably, the Sr₂Fe_1.5Mo_0.4V_0.1O_6-δ based symmetrical SOEC achieves a current density of 1.56 A cm^-2 at 1.5 V and 800 °C, maintaining outstanding durability over 300 h. Theoretical analysis unveils that V-doping facilitates the formation of oxygen vacancies, resulting in high intrinsic electrocatalytic activity for CO₂ reduction. These findings present a viable and facile strategy for advancing electrocatalysts in CO₂ conversion technologies.

Pancreatic ductal adenocarcinoma (PDAC) is characterized by its fibrotic and stiff extracellular matrix. However, how the altered cell/extracellular-matrix signalling contributes to the PDAC tumour phenotype has been difficult to dissect. Here we design and engineer matrices that recapitulate the key hallmarks of the PDAC tumour extracellular matrix to address this knowledge gap. We show that patient-derived PDAC organoids from three patients develop resistance to several clinically relevant chemotherapies when cultured within high-stiffness matrices mechanically matched to in vivo tumours. Using genetic barcoding, we find that while matrix-specific clonal selection occurs, cellular heterogeneity is not the main driver of chemoresistance. Instead, matrix-induced chemoresistance occurs within a stiff environment due to the increased expression of drug efflux transporters mediated by CD44 receptor interactions with hyaluronan. Moreover, PDAC chemoresistance is reversible following transfer from high- to low-stiffness matrices, suggesting that targeting the fibrotic extracellular matrix may sensitize chemoresistant tumours. Overall, our findings support the potential of engineered matrices and patient-derived organoids for elucidating extracellular matrix contributions to human disease pathophysiology.

The trap states at both the upper and bottom interfaces of perovskite layers significantly impact non-radiative carrier recombination. The widely used solvent-based passivation methods result in the disordered distribution of surface components, posing challenges for the commercial application of large-area perovskite solar cells (PSCs). To address this issue, a novel NH₃ gas-assisted all-inorganic dual-interfaces passivation strategy is proposed. Through the gas treatment of the perovskite surface, NH₃ molecules significantly enhanced the iodine vacancy formation energy (1.54 eV) and bonded with uncoordinated Pb²⁺ to achieve non-destructive passivation. Meanwhile, the reduction of the film defect states is accompanied by a decrease in the work function, which promotes carrier transport between the interface. Further, a stable passivation layer is constructed to manage the bottom interfacial defects using inorganic potassium tripolyphosphate (PT), whose ─P═O group effectively mitigated the charged defects and lowered the carrier transport barriers and nucleation barriers of PVK, while the gradient distribution of K⁺ improved the crystalline quality of PVK film. Based on the dual-interface synergistic effect, the optimal MA-contained PSCs with an effective area of 0.1 cm² achieved an efficiency of 24.51% and can maintain 90% of the initial value after aging (10-20% RH and 20 °C) for 2000 h.