Surface barriers to mass transfer in nanoporous materials for catalysis and separations

Surface barriers to mass transfer in various nanoporous materials have been increasingly identified. These past few years especially, a significant impact on catalysis and separations has come to light. Broadly speaking, there are two types of barriers: internal barriers, which affect intraparticle diffusion, and external barriers, which determine the uptake and release rates of molecules into and out of the material. Here, we review the literature on surface barriers to mass transfer in nanoporous materials and describe how the existence and influence of surface barriers has been characterized, aided by molecular simulations and experimental measurements. As this is a complex, evolving research topic, without consensus from the scientific community at the time of writing, we present various current viewpoints, not always in agreement, on the origin, nature, and function of such barriers in catalysis and separation. We also emphasize the need for considering all the elementary steps of the mass transfer process in optimally designing new nanoporous and hierarchically structured adsorbents and catalysts

Anisotropic ultrafast spin/valley dynamics in WTe2 films

WTe2 Weyl semimetal hosts the natural broken inversion symmetry and strong spin orbit coupling, making it promising for exotic spin/valley dynamics within a picosecond timescale. Here, we unveil an anisotropic ultrafast spin/valley dynamics in centimeter-scale, single-crystalline Td-WTe2 films using a femtosecond pump-probe technique at room temperature. We observe a transient (~0.8 ps) intra-valley transition and a subsequent polarization duration (~5 ps) during the whole spin/valley relaxation process. Furthermore, the relaxation exhibits the remarkable anisotropy of approximately six-fold and two-fold symmetries due to the intrinsic anisotropy along the crystalline orientation and the extrinsic matrix element effect, respectively. Our results offer a prospect for the ultrafast manipulation of spin/valleytronics in topological quantum materials for dissipationless high-speed spin/valleytronic devices.Comment: 21 pages, 4 figure

Observation of an anisotropic ultrafast spin relaxation process in large-area WTe2films

Weyl semimetal Td-WTe2 hosts the natural broken inversion symmetry and strong spin-orbit coupling, which contains profound spin-related physics within a picosecond timescale. However, the comprehensive understanding of ultrafast spin behaviors in WTe2 is lacking due to its limited quality of large-scale films. Here, we report on an anisotropic ultrafast spin dynamics in highly oriented Td-WTe2 films using a femtosecond pump-probe technique at room temperature. A transient spin polarization-flip transition as fast as 0.8 ps is observed upon photoexcitation. The inversed spin is subsequently scattered by defects with a duration of about 5.9 ps. The whole relaxation process exhibits an intriguing dual anisotropy of sixfold and twofold symmetries, which stems from the energy band anisotropy of the WTe2 crystalline structure and the matrix element effect, respectively. Our work enriches the insights into the ultrafast opto-spintronics in topological Weyl semimetals

Sensitive and Ultrabroadband Phototransistor Based on Two-Dimensional Bi2O2Se Nanosheets

Bi2O2Se, a high-mobility and air-stable 2D material, has attracted substantial attention for application in integrated logic electronics and optoelectronics. However, achieving an overall high performance over a wide spectral range for Bi2O2Se-based devices remains a challenge. A broadband phototransistor with high photoresponsivity (R) is reported that comprises high-quality large-area (≈180 µm) Bi2O2Se nanosheets synthesized via a modified chemical vapor deposition method with a face-down configuration. The device covers the ultraviolet (UV), visible (Vis), and near-infrared (NIR) wavelength ranges (360–1800 nm) at room temperature, exhibiting a maximum R of 108 696 A W−1 at 360 nm. Upon illumination at 405 nm, the external quantum efficiency, R, and detectivity (D*) of the device reach up to 1.5 × 107%, 50055 A W−1, and 8.2 × 1012 Jones, respectively, which is attributable to a combination of the photogating, photovoltaic, and photothermal effects. The devices reach a −3 dB bandwidth of 5.4 kHz, accounting for a fast rise time (τrise) of 32 µs. The high sensitivity, fast response time, and environmental stability achieved simultaneously in these 2D Bi2O2Se phototransistors are promising for high-quality UV and IR imaging applications

Spin-ARPES EUV beamline for ultrafast materials research and development

A new femtosecond, Extreme Ultraviolet (EUV), Time Resolved Spin-Angle Resolved Photo-Emission Spectroscopy (TR-Spin-ARPES) beamline was developed for ultrafast materials research and development. This 50-fs laser-driven, table-top beamline is an integral part of the "Ultrafast Spintronic Materials Facility", dedicated to engineering ultrafast materials. This facility provides a fast and in-situ analysis and development of new materials. The EUV source based on high harmonic generation process emits 2.3 × 1011 photons/second (2.3 × 108 photons/pulse) at H23 (35.7 eV) and its photon energy ranges from 10 eV to 75 eV, which enables surface sensitive studies of the electronic structure dynamics. The EUV monochromator provides the narrow bandwidth of the EUV beamline while preserving its pulse duration in an energy range of 10-100 eV. Ultrafast surface photovoltaic effect with ~650 fs rise-time was observed in p-GaAs (100) from time-resolved ARPES spectra. The data acquisition time could be reduced by over two orders of magnitude by scaling the laser driver from 1 KHz, 4W to MHz, KW average power

Dispositional and Situational Autonomy as Moderators of Mood and Creativity

Although previous research suggests that mood can influence creativity, the controversy about the effects of positive and negative moods has raged for years. This study investigated how the relationship between induced mood and creativity is moderated by dispositional and situational autonomy. It contrasted the different moderating effects of the 2 kinds of autonomy. In Experiment 1, 93 participants completed a questionnaire about dispositional autonomy and performed a creative task after watching 1 of 3 film clips, which were to induce positive, negative, or neutral moods. The results of experiment 1 indicated that positive moods prompted creativity and negative moods inhibited creativity when individuals were low in dispositional autonomy (low in autonomous orientation or high in impersonal orientation). In Experiment 2, 73 participants engaged in a game to manipulate levels of situational autonomy and induce positive or negative moods. The results of experiment 2 showed that positive moods fostered greater creativity than did negative moods when individuals were in full-autonomy condition. The different moderating effects of dispositional and situational autonomy are discussed

Conflict monitoring and stimulus categorization processes involved in the prosocial attitude implicit association test: Evidence from event-related potentials

The implicit association test (IAT) is a promising method used to assess individual implicit attitudes by indirectly measuring the strengths of associations between target and attribute categories. To date, the cognitive processes involved in the prosocial attitude IAT task have received little attention. The present study examined the temporal dynamics of the IAT that measures prosocial attitude using event-related potentials (ERPs). ERP results revealed enhanced N2 amplitudes for incongruent trials when compared with congruent trials and enhanced P300 amplitudes for congruent trials when compared with incongruent trials. In addition, the N2 amplitude differences were significantly correlated with individual prosocial behavior (the amount of donation). Our findings suggest that conflict monitoring and stimulus categorization processes are involved in the prosocial attitude IAT task and that the ERP indices of IATs that measure prosocial attitude may predict individual prosocial behavior.The implicit association test (IAT) is a promising method used to assess individual implicit attitudes by indirectly measuring the strengths of associations between target and attribute categories. To date, the cognitive processes involved in the prosocial attitude IAT task have received little attention. The present study examined the temporal dynamics of the IAT that measures prosocial attitude using event-related potentials (ERPs). ERP results revealed enhanced N2 amplitudes for incongruent trials when compared with congruent trials and enhanced P300 amplitudes for congruent trials when compared with incongruent trials. In addition, the N2 amplitude differences were significantly correlated with individual prosocial behavior (the amount of donation). Our findings suggest that conflict monitoring and stimulus categorization processes are involved in the prosocial attitude IAT task and that the ERP indices of IATs that measure prosocial attitude may predict individual prosocial behavior

Who Are You More Likely to Help? The Effects of Expected Outcomes and Regulatory Focus on Prosocial Performance.

Prosocial behavior refers to a broad category of actions that benefit other people or the society. Compared with other factors that affect prosocial performance, prosocial outcomes, consisting of prosocial gains and prosocial non-losses have received less attention up to now. In the current research, we explored the influences of different types of expected outcomes and regulatory focus on prosocial performance. Studies 1a and 1b examined the differences in prosocial performance elicited by prosocial gain (e.g., enhancing others' access to clean water) and prosocial non-loss outcomes (e.g., protecting others from suffering dirty water). We found that the expected prosocial non-loss outcomes induced greater prosocial performance compared with the expected prosocial gain outcomes. Studies 2a and 2b examined the effects of dispositional and situational regulatory focus on prosocial loss aversion. We found that differences in prosocial performance between two expected prosocial outcomes were reduced when promotion focus was primed; whereas a primed prevention focus did not significantly increase this difference. Additionally, participants displayed a greater prosocial loss aversion in the prevention focus condition than in the promotion focus condition. The reason for the non-significant interaction between regulatory focus and expected prosocial outcome was discussed

Nano- and microscale engineering of the molybdenum disulfide-based catalysts for syngas to ethanol conversion

Nickel-promoted MoS, unsupported catalysts and laponite-supported alcohol synthesis catalysts were synthesised by using microemulsion (ME) and hydrothermal (HT) methods. Highly ordered sulfide slabs, consisting of up to seven layers, were visible in the TEM images of HT-based NiMoS catalysts. In contrast, disordered sulfide layers were identified in ME-based NiMoS catalysts. High catalytic activity was observed in ME-based supported (laponite-supported NiMoS) and unsupported catalysts. After the CO hydrogenation reaction, the catalysts were characterised by X-ray photoelectron spectroscopy and inductively coupled plasma-mass spectrometry elemental analyses, which detected a significant sulfur loss in ME-based NiMoS catalysts and minor sulfur loss in HT-based NiMoS catalysts. In addition to the large surface area (120 m g), disordered sulfide structure, and exposed active sites, ME-based NiMoS catalysts demonstrated higher alcohol selectivity (61 mol%) than HT-based NiMoS catalysts (15 mol%). Correlations between the catalyst morphology, surface active components, and alcohol selectivity are discussed herein