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NO2 and H2 sensing properties for urchin-like hexagonal WO3 based on experimental and first-principle investigations
摘要： An intricate sea-urchin-like hexagonal WO3 nanostructure was synthesized by a facile hydrothermal approach. Sensing properties of the as-fabricated sensor exhibited surpassing response and selectivity for NO2 in comparison of H2 after corroborating the composition, phase-purity and surface morphology using X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Formation of the urchin-like structure was ascribed to the capping effects of potassium sulfate that prompts the anisotropic growth of WO3, leading to hierarchical complex with a large surface-volume ratio. In particular, first-principle calculation had provided a new perspective for us to delve into the sensing process of H2 and NO2 from an atomic level. It was found that the sensing properties mainly arose from the tuning of electronic structure and electrons transfer between the adsorbed gas and the sensitized surface along with the charge relocation between them. Finally, a plausible mechanism was proposed as theoretical guidance for achieving high-performance sensors experimentally and supposedly.
关键词： Gas sensing,Surface reaction,First-principles,WO3
更新于2025-09-23 15:23:52
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High-Yield Formation of Graphdiyne Macrocycles Through On-Surface Assembling and Coupling Reaction
摘要： Rationally designed halogenated hydrocarbons are widely used building blocks to fabricate covalent-bonded carbon nanostructures on surface through a reaction pathway involving generation and dissociation of organometallic intermediates and irreversible covalent bond formation. Here we provide a comprehensive picture of the on-surface-assisted homocoupling reaction of 1,3-bis(2-bromoethynyl)benzene on Au(111), aiming for the synthesis of graphdiyne nanostructures. Submolecular resolution scanning tunneling microscopy and noncontact atomic force microscopy observations identify the organometallic intermediates and their self-assemblies formed in the dehalogenation process. The demetallization of the organometallic intermediates at elevated temperatures produces butadiyne moieties that spontaneously formed two different covalent structures, i.e. graphdiyne zigzag chains and macrocycles, whose ratio was found to depend on the initial coverage of organometallic intermediates. At the optimal condition, the stepwise demetallization and cyclization led to a high yield production of graphdiyne macrocycles up to 95 %. Statistical analysis and theoretical calculations suggested that the favored formation of macrocycles was resulted from the complex interplay between thermodynamic and kinetic processes involving the organometallic bonded intermediates and the covalently bonded butadiyne moieties.
关键词： on-surface reaction,graphdiyne macrocycle,organometallic intermediate,scanning tunneling microscopy,noncontact atomic force microscopy,thermodynamic and kinetic control
更新于2025-09-10 09:29:36