Oxide-Metal Interaction Probed by Scanning Tunneling Microscope Manipulation of Cr2O7 Clusters on Au(111).

Interfacial interaction plays a crucial rule in catalysis over supported catalysts, and the catalyst-support interaction needs to be explored at microscopic scale. Here, we use the scanning tunneling microscope (STM) tip to manipulate Cr2O7 dinuclear clusters on Au(111) and find that the Cr2O7-Au interaction can be weakened by an electric field in the STM junction, facilitating rotation and translation of the individual clusters at the imaging temperature (78 K). Surface alloying with Cu makes the manipulation of the Cr2O7 clusters hard due to the enhanced Cr2O7-substrate interaction. Density functional theory calculations reveal that barrier for translation of a Cr2O7 cluster on the surface can be increased by surface alloying, influencing the tip manipulation. Our study demonstrates that the oxide-metal interfacial interaction can be probed by STM tip manipulation of supported oxide clusters, which provides a new method to investigate the interfacial interaction.

Periodic Arrays of Metal Nanoclusters on Ultrathin Fe-Oxide Films Modulated by Metal-Oxide Interactions.

Rational design of highly stable and active metal catalysts requires a deep understanding of metal-support interactions at the atomic scale. Here, ultrathin films of FeO and FeO2-x grown on Pt(111) are used as templates for the construction of well-defined metal nanoclusters. Periodic arrays of Cu clusters in the form of monomers and trimers are preferentially located at FCC domains of FeO/Pt(111) surface, while the selective location of Cu clusters at FeO2 domains is observed on FeO2-x /Pt(111) surface. The preferential nucleation and formation of well-ordered Cu clusters are driven by different interactions of Cu with the Fe oxide domains in the sequence of FeO2-FCC > FeO-FCC > FeO-HCP > FeO-TOP, which is further validated by density functional theory calculations. It has been revealed that the p-band center as a reactivity descriptor of surface O atoms determines the interaction between metal adatoms and Fe oxides. The modulated metal-oxide interaction provides guidance for the rational design of supported single-atom and nanocluster catalysts.

Microwave Absorption of α-Fe2O3@diatomite Composites.

A neoteric round sieve diatomite (De) decorated with sea-urchin-like alpha-type iron trioxide (α-Fe2O3) synthetics was prepared by the hydrothermal method and further calcination. The results of the electromagnetic (EM) parameters of α-Fe2O3-decorated De (α-Fe2O3@D) showed that the minimum reflection loss (RLmin) of α-Fe2O3@D could reach -54.2 dB at 11.52 GHz and the matched absorber thickness was 3 mm. The frequency bandwidth corresponding to the microwave RL value below -20 dB was up to 8.24 GHz (9.76-18 GHz). This indicates that α-Fe2O3@D composite can be a lightweight and stable material; because of the low density of De (1.9-2.3 g/cm3), the density of α-Fe2O3@D composite material is lower than that of α-Fe2O3 (5.18 g/cm3). We found that the combination of the magnetic loss of sea-urchin-like α-Fe2O3 and the dielectric loss of De has the most dominant role in electromagnetic wave absorption and loss. We focused on comparing the absorbing properties before and after the formation of sea-urchin-like α-Fe2O3 and explain in detail the effects of the structure and crystal shape of this novel composite on the absorbing properties.

Dynamic transformation between bilayer islands and dinuclear clusters of Cr oxide on Au(111) through environment and interface effects.

SignificanceFor oxide catalysts, it is important to elucidate and further control their atomic structures. In this work, well-defined CrO2 bilayer islands and Cr2O7 dinuclear clusters have been grown on Au(111) and unambiguously identified by scanning tunneling microscopy and theoretical calculations. Upon cycled redox treatments, the two kinds of oxide nanostructures can be reversibly transformed. It is interesting to note that both Cr oxides do not exist in bulk but need to be stabilized by the metal surface and the specific environment. Our results suggest that both redox atmosphere and interface confinement effects can be used to construct an oxide nanostructure with the specific chemical state and structure.

Core-Shell Structured SiO2@NiFe LDH Composite for Broadband Electromagnetic Wave Absorption.

In this work, a novel core-shell structure material, NiFe layered double hydroxide (NiFe LDH) loaded on SiO2 microspheres (SiO2@NiFe LDH), was synthesized by a one-step hydrothermal method, and the spontaneous electrostatic self-assembly process. The morphology, structure, and microwave absorption properties of SiO2@NiFe LDH nanocomposites with different NiFe element ratios were systematically investigated. The results show that the sample of SiO2@NiFe LDH-3 nanocomposite has excellent microwave absorption properties. It exhibits broadband effective absorption bandwidth (RL < −10 dB) of 8.24 GHz (from 9.76 GHz to 18.0 GHz) and the reflection loss is −53.78 dB at the matched thickness of 6.95 mm. It is expected that this SiO2@NiFe-LDH core-shell structural material can be used as a promising non-precious, metal-based material microwave absorber to eliminate electromagnetic wave contamination.

Effects of college students' mindfulness on depression symptoms during the epidemic prevention and control period: The mediating effect of psychological resilience.

Depression symptoms significantly impact college students' mental health, particularly during the "closed management" period during the spread of COVID-19. Exploring the mechanism that affects college students' depression symptoms can help alleviate the impact of closed management policies on individual mental health and improve their mental health level. The onset of the COVID-19 pandemic resulted in the normalization of epidemic prevention and control in China and the implementation of the dynamic zero-COVID policy. This study used the Five-Factor Mindfulness Questionnaire-Short Form, Psychological Resilience Scale, and Beck Depression Scale to investigate the mindfulness, psychological resilience, and depression symptoms of 1,062 students under closed management conditions at Northwest Normal University. The mindfulness, psychological resilience, and depression status of students in closed management were investigated using an online questionnaire survey. Eight hundred and ten college students (M age = 20.43, SD = 1.67, range = 17-30) were selected to test the model using the structural equation model and bootstrap method. The results showed that the gender differences in mindfulness and psychological resilience were not significant. Gender differences in depression symptoms were significant, and depression symptoms in men were significantly higher than in women. Grade differences in resilience, mindfulness, and depression levels were not significant. Thus, psychological resilience is negatively associated with depressive symptoms. Psychological resilience plays a mediating role between mindfulness and depressive symptoms. This study provides reference and inspiration for improving college students' mental health under epidemic prevention and control circumstances.