Two-dimensional monolayer transition metal dichalcogenide semiconductors are ideal building blocks for atomically thin, flexible optoelectronic and catalytic devices. Although challenging for two-dimensional systems, sub-diffraction optical microscopy provides a nanoscale material understanding that is vital for optimizing their optoelectronic properties. Here we use the ‘Campanile' nano-optical probe to spectroscopically image exciton recombination within monolayer MoS2 with sub-wavelength resolution (60 nm), at the length scale relevant to many critical optoelectronic processes. Synthetic monolayer MoS2 is found to be composed of two distinct optoelectronic regions: an interior, locally ordered but mesoscopically heterogeneous two-dimensional quantum well and an unexpected ∼300-nm wide, energetically disordered edge region. Further, grain boundaries are imaged with sufficient resolution to quantify local exciton-quenching phenomena, and complimentary nano-Auger microscopy reveals that the optically defective grain boundary and edge regions are sulfur deficient. The nanoscale structure–property relationships established here are critical for the interpretation of edge- and boundary-related phenomena and the development of next-generation two-dimensional optoelectronic devices.
Nickel hydride with a diphosphinite-based ligand catalyzes the highly efficient reduction of CO(2) with catecholborane, and the hydrolysis of the resulting methoxyboryl species produces CH(3)OH in good yield. The mechanism involves a nickel formate, formaldehyde, and a nickel methoxide as different reduced stages for CO(2). The reaction may also be catalyzed by an air-stable nickel formate.
Two platinum(II) diimine dithiolate complexes, Pt(dcbpy)(met) (1) and Pt(dcbpy)(bdt) (2) (dcbpy = 4,4‘-dicarboxyl-2,2‘-bipyridine; met = cis-1,2-dicarbomethoxyethylene-1,2-dithiolate; bdt = 1,2-benzenedithiolate) were used as sensitizers for platinized TiO2 (TiO2/Pt), and systems composed of 1/TiO2/Pt and 2/TiO2/Pt were found to generate hydrogen from aqueous protons and a sacrificial electron donor, triethanolamine (TEOA), under visible light irradiation. Turnover numbers reached 84 after 95 h of irradiation for the first system and 72 after 73 h of irradiation for the second. Additional photolyses with light of wavelength longer than 455 nm showed that the systems are photostable with no loss of activity. Parallel experiments with Pt(diimine)(met) and Pt(diimine)(bdt) complexes that do not bind to TiO2 reveal that attachment of the sensitizer to TiO2 is essential for effective hydrogen generation.
NO adsorption, diffusion and reaction at reduced CeO2(110) were studied by density functional theory calculations. NO accommodated by O vacancies can readily diffuse via alternate NO2 formation and dissociation, facilitating N2O2 formation and subsequent reduction to N2. Rare earth ceria plays an important catalytic role in both static and dynamic ways by tuning the electron distribution in adsorbates and reacting molecules.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.