58 research outputs found

    Chiral kagome lattice from simple ditopic molecular bricks

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    Self-assembly techniques allow for the fabrication of highly organized architectures with atomic-level precision. Here, we report on molecular-level scanning tunneling microscopy observations demonstrating the supramolecular engineering of complex, regular, and long-range ordered periodic networks on a surface atomic lattice using simple linear molecular bricks. The length variation of the employed de novo synthesized linear dicarbonitrile polyphenyl molecules translates to distinct changes of the bonding motifs that lead to hierarchic order phenomena and unexpected changes of the surface tessellations. The achieved 2D organic networks range from a close-packed chevron pattern via a rhombic network to a hitherto unobserved supramolecular chiral kagome lattice

    The influence of student gender on the assessment of undergraduate student work

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    The aim of this study was to investigate the influence of perceived student gender on the feedback given to undergraduate student work. Participants (n = 12) were lecturers in higher education and were required to mark two\ud undergraduate student essays. The first student essay that all participants marked was the control essay. Participants were informed that the control essay was written by Samuel Jones (a male student). Participants then marked the target essay. Although participants marked the same essay, half of the participants (n = 6) were informed that the student essay was written by Natasha Brown (a female student), while the remaining participants were informed that it was written by James Smith (a male student). In-text and end-of-text feedback were qualitatively analysed on six dimensions: academic style of writing; criticality; structure, fluency and cohesion; sources used; understanding/knowledge of the subject; and other. Analysis of feedback for both the control and target essay revealed no discernible differences in the number of comments (strengths of the essay, areas for improvement) made and the content and presentation of these comments between the two groups. Pedagogical implications pertaining to the potential impact of anonymous marking on feedback processes are discussed

    Electron Coherence in a Melting Lead Monolayer

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    We used angle-resolved photoemission spectroscopy to measure the electronic dispersion and single-particle spectral, function in a liquid metal. A lead monolayer supported on a copper (111) surface was investigated as the temperature was raised through the melting transition of the film. Electron spectra and momentum distribution maps of the liquid film revealed three key features of the electronic structure of liquids: the persistence of a Fermi surface, the filling of band gaps, and the localization of the wave functions upon melting. Distinct coherence lengths for different sheets of the Fermi surface were found, indicating a strong dependence of the localization lengths on the character of the constituent atomic wave functions.</p

    Self-assembly and spectroscopic fingerprints of photoactive pyrenyl tectons on hBN/Cu(111)

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    The controlled modification of electronic and photophysical properties of polycyclic aromatic hydrocarbons by chemical functionalization, adsorption on solid supports, and supramolecular organization is the key to optimize the application of these compounds in (opto)electronic devices. Here, we present a multimethod study comprehensively characterizing a family of pyridin-4-ylethynylfunctionalized pyrene derivatives in different environments. UV–vis measurements in toluene solutions revealed absorption at wavelengths consistent with density functional theory (DFT) calculations, while emission experiments showed a high fluorescence quantum yield. Scanning tunneling microscopy (STM) and spectroscopy (STS) measurements of the pyrene derivatives adsorbed on a Cu(111)-supported hexagonal boron nitride (hBN) decoupling layer provided access to spatially and energetically resolved molecular electronic states. We demonstrate that the pyrene electronic gap is reduced with an increasing number of substituents. Furthermore, we discuss the influence of template-induced gating and supramolecular organization on the energies of distinct molecular orbitals. The selection of the number and positioning of the pyridyl termini in tetrasubstituted, trans- and cis-like-disubstituted derivatives governed the self-assembly of the pyrenyl core on the nanostructured hBN support, affording dense-packed arrays and intricate porous networks featuring a kagome lattice
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