The future of mobility-as-a-service: trust transfer across automated mobilities, from road to sidewalk.

While trust in different types of automated vehicles has been a major focus for researchers and vehicle manufacturers, few studies have explored how people trust automated vehicles that are not cars, nor how their trust may transfer across different mobilities enabled with automation. To address this objective, a dual mobility study was designed to measure how trust in an automated vehicle with a familiar form factor-a car-compares to, and influences, trust in a novel automated vehicle-termed sidewalk mobility. A mixed-method approach involving both surveys and a semi-structured interview was used to characterize trust in these automated mobilities.

Nickel particle-enabled width-controlled growth of bilayer molybdenum disulfide nanoribbons.

Transition metal dichalcogenides exhibit a variety of electronic behaviors depending on the number of layers and width. Therefore, developing facile methods for their controllable synthesis is of central importance. We found that nickel nanoparticles promote both heterogeneous nucleation of the first layer of molybdenum disulfide and simultaneously catalyzes homoepitaxial tip growth of a second layer via a vapor-liquid-solid (VLS) mechanism, resulting in bilayer nanoribbons with width controlled by the nanoparticle diameter.

Surfactant-Mediated Growth and Patterning of Atomically Thin Transition Metal Dichalcogenides.

The role of additives in facilitating the growth of conventional semiconducting thin films is well-established. Apparently, their presence is also decisive in the growth of two-dimensional transition metal dichalcogenides (TMDs), yet their role remains ambiguous. In this work, we show that the use of sodium bromide enables synthesis of TMD monolayers a surfactant-mediated growth mechanism, without introducing liquefaction of metal oxide precursors.

The Critical Role of Electrolyte Gating on the Hydrogen Evolution Performance of Monolayer MoS.

According to density functional theory, monolayer (ML) MoS is predicted to possess electrocatalytic activity for the hydrogen evolution reaction (HER) that approaches that of platinum. However, its observed HER activity is much lower, which is widely believed to result from a large Schottky barrier between ML MoS and its electrical contact. In order to better understand the role of contact resistance in limiting the performance of ML MoS HER electrocatalysts, this study has employed well-defined test platforms that allow for the simultaneous measurement of contact resistance and electrocatalytic activity toward the HER during electrochemical testing.

Exfoliation of a non-van der Waals material from iron ore hematite.

With the advent of graphene, the most studied of all two-dimensional materials, many inorganic analogues have been synthesized and are being exploited for novel applications. Several approaches have been used to obtain large-grain, high-quality materials. Naturally occurring ores, for example, are the best precursors for obtaining highly ordered and large-grain atomic layers by exfoliation.

Intrinsic Chirality Origination in Carbon Nanotubes.

Elucidating the origin of carbon nanotube chirality is key for realizing their untapped potential. Currently, prevalent theories suggest that catalyst structure originates chirality via an epitaxial relationship. Here we studied chirality abundances of carbon nanotubes grown on floating liquid Ga droplets, which excludes the influence of catalyst features, and compared them with abundances grown on solid Ru nanoparticles.

Ultrasensitive gas detection of large-area boron-doped graphene.

Heteroatom doping is an efficient way to modify the chemical and electronic properties of graphene. In particular, boron doping is expected to induce a p-type (boron)-conducting behavior to pristine (nondoped) graphene, which could lead to diverse applications. However, the experimental progress on atomic scale visualization and sensing properties of large-area boron-doped graphene (BG) sheets is still very scarce.

High-performance hybrid oxide catalyst of manganese and cobalt for low-pressure methanol synthesis.

Carbon dioxide capture and use as a carbon feedstock presents both environmental and industrial benefits. Here we report the discovery of a hybrid oxide catalyst comprising manganese oxide nanoparticles supported on mesoporous spinel cobalt oxide, which catalyses the conversion of carbon dioxide to methanol at high yields. In addition, carbon-carbon bond formation is observed through the production of ethylene.

Insights into carbon nanotube nucleation: cap formation governed by catalyst interfacial step flow.

In order to accommodate an increasing demand for carbon nanotubes (CNTs) with desirable characteristics one has to understand the origin of helicity of their structures. Here, through in situ microscopy we demonstrate that the nucleation of a carbon nanotube is initiated by the formation of the carbon cap. Nucleation begins with the formation of a graphene embryo that is bound between opposite step-edges on the nickel catalyst surface.

Graphene as an atomically thin interface for growth of vertically aligned carbon nanotubes.

Growth of vertically aligned carbon nanotube (CNT) forests is highly sensitive to the nature of the substrate. This constraint narrows the range of available materials to just a few oxide-based dielectrics and presents a major obstacle for applications. Using a suspended monolayer, we show here that graphene is an excellent conductive substrate for CNT forest growth.

Enhanced gas sensing in pristine carbon nanotubes under continuous ultraviolet light illumination.

The advance of nanomaterials has opened new opportunities to develop ever more sensitive sensors owing to their high surface-to-volume ratio. However, it is challenging to achieve intrinsic sensitivities of nanomaterials for ultra-low level detections due to their vulnerability against contaminations. Here we show that despite considerable achievements in the last decade, continuous in situ cleaning of carbon nanotubes with ultraviolet light during gas sensing can still dramatically enhance their performance.

Formation of ripples in graphene as a result of interfacial instabilities.

Formation of ripples on a supported graphene sheet involves interfacial interaction with the substrate. In this work, graphene was grown on a copper foil by chemical vapor deposition from methane. On thermal quenching from elevated temperatures, we observed the formation of ripples in grown graphene, developing a peculiar topographic pattern in the form of wavy grooves and single/double rolls, roughly honeycomb cells, or their combinations.

Carbon nanotube nucleation driven by catalyst morphology dynamics.

In situ observation of the carbon nanotube nucleation process accompanied by dynamic reconstruction of the catalyst particle morphology is considered within a thermodynamic approach. It reveals the driving force for the detachment of the sp(2)-carbon cap, so-called lift-off-a crucial event in nanotube growth. A continuum model and detailed atomistic calculations identify the critical factors in the lift-off process: (i) catalyst surface energy, affected by the chemisorbed carbon atoms at the exterior surface of the catalyst, exposed to the carbon feedstock; and (ii) the emergence of a pristine, high-energy facet under the sp(2)-carbon dome.

The catalyst for growing single-walled carbon nanotubes by catalytic chemical vapor deposition method.

The complexity of the catalyst's actual role and properties, along with the numerous synthesis parameters for the growth of single-walled carbon nanotubes (SWCNTs), has hindered the efforts to understand the formation of this fascinating material. In this manuscript, we review and discuss the data regarding the properties and peculiarities of a wide variety of catalyst nanoparticles available in the scientific literature, in order to reveal common features that are favorable for SWCNTs growth. A special effort is made to show the influence of the support material on the thermodynamic properties of the catalyst and, thereby, on the growth path of the nanotubes.

Thermodynamics behind carbon nanotube growth via endothermic catalytic decomposition reaction.

Carbon filaments can be grown using hydrocarbons with either exothermic or endothermic catalytic decomposition enthalpies. By in situ monitoring the evolution of the reaction enthalpy during nanotube synthesis via methane gas, we found that although the decomposition reaction of methane is endothermic an exothermic process is superimposed which accompanies the nanotube growth. Analysis shows that the main contributor in this liberated heat is the radiative heat transfer from the surroundings, along with dehydrogenation reaction of in situ formed secondary hydrocarbons on the catalyst surface and the carbon hydrogenation/oxidation processes.

Low-temperature single-wall carbon nanotubes synthesis: feedstock decomposition limited growth.

We report on the lowest temperature of SWCNT growth using endothermic decomposition of CH4 gas on a specially activated alumina-supported Fe:Mo catalyst. However, the observed lowest growth temperature (560 degrees C) is higher than that reported previously for exothermic feedstock type. Our observation indicates that the decomposition threshold temperature of the feedstock limits the SWCNT growth.

Reduced carbon solubility in Fe nanoclusters and implications for the growth of single-walled carbon nanotubes.

Fe nanoclusters are becoming the standard catalysts for growing single-walled carbon nanotubes via chemical vapor decomposition. Contrary to the Gibbs-Thompson model, we find that the reduction of the catalyst size requires an increase of the minimum temperature necessary for the growth. We address this phenomenon in terms of solubility of C in Fe nanoclusters and, by using first-principles calculations, we devise a simple model to predict the behavior of the phases competing for stability in Fe-C nanoclusters at low temperature.