Dataset Information

Calculating Optical Absorption Spectra of Thin Polycrystalline Organic Films: Structural Disorder and Site-Dependent van der Waals Interaction.

ABSTRACT: We propose a new approach for calculating the change of the absorption spectrum of a molecule when moved from the gas phase to a crystalline morphology. The so-called gas-to-crystal shift ?[Formula: see text] _m is mainly caused by dispersion effects and depends sensitively on the molecule's specific position in the nanoscopic setting. Using an extended dipole approximation, we are able to divide ?[Formula: see text] _m = -QW_m in two factors, where Q depends only on the molecular species and accounts for all nonresonant electronic transitions contributing to the dispersion while W_m is a geometry factor expressing the site dependence of the shift in a given molecular structure. The ability of our approach to predict absorption spectra is demonstrated using the example of polycrystalline films of 3,4,9,10-perylenetetracarboxylic diimide (PTCDI).

SUBMITTER: Megow J

PROVIDER: S-EPMC4360364 | biostudies-literature | 2015 Mar

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Calculating Optical Absorption Spectra of Thin Polycrystalline Organic Films: Structural Disorder and Site-Dependent van der Waals Interaction.

Megow Jörg J Körzdörfer Thomas T Renger Thomas T Sparenberg Mino M Blumstengel Sylke S Henneberger Fritz F May Volkhard V

The journal of physical chemistry. C, Nanomaterials and interfaces 20150224 10

We propose a new approach for calculating the change of the absorption spectrum of a molecule when moved from the gas phase to a crystalline morphology. The so-called gas-to-crystal shift Δ[Formula: see text] m is mainly caused by dispersion effects and depends sensitively on the molecule's specific position in the nanoscopic setting. Using an extended dipole approximation, we are able to divide Δ[Formula: see text] m = -QWm in two fac ...[more]

PMID: 25834658

Similar Datasets

Project description:Liquid-phase deposition of exfoliated 2D nanosheets is the basis for emerging technologies that include writable electronic inks, molecular barriers, selective membranes, and protective coatings against fouling or corrosion. These nanosheet thin films have complex internal structures that are discontinuous assemblies of irregularly tiled micron-scale sheets held together by van der Waals (vdW) forces. On stiff substrates, nanosheet vdW films are stable to many common stresses, but can fail by internal delamination under shear stress associated with handling or abrasion. This "re-exfoliation" pathway is an intrinsic feature of stacked vdW films and can limit nanosheet-based technologies. Here we investigate the shear stability of graphene oxide and MoSe2 nanosheet vdW films through lap shear experiments on polymer-nanosheet-polymer laminates. These sandwich laminate structures fail in mixed cohesive and interfacial mode with critical shear forces from 40 - 140 kPa and fracture energies ranging from 0.2 - 6 J/m2. Surprisingly these energies are higher than delamination energies reported for smooth peeling of ordered stacks of continuous 2D sheets, which we propose is due to energy dissipation and chaotic crack motion during nanosheet film disassembly at the crack tip. Experiment results also show that film thickness plays a key role in determining critical shear force (maximum load before failure) and dissipated energy for different nanosheet vdW films. Using a mechanical model with an edge crack in the thin nanosheet film, we propose a shear-to-tensile failure mode transition to explain a maximum in critical shear force for graphene oxide films but not MoSe2 films. This transition reflects a weakening of the substrate confinement effect and increasing rotational deformation near the film edge as the film thickness increases. For graphene oxide, the critical shear force can be increased by electrostatic cross-linking achieved through interlayer incorporation of metal cations. These results have important implications for the stability of functional devices that employ 2D nanosheet coatings.

Dataset Information

Calculating Optical Absorption Spectra of Thin Polycrystalline Organic Films: Structural Disorder and Site-Dependent van der Waals Interaction.

Publications

Calculating Optical Absorption Spectra of Thin Polycrystalline Organic Films: Structural Disorder and Site-Dependent van der Waals Interaction.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets