175 research outputs found
Design Principle of Conjugated Polyelectrolytes to Make Them Water‐Soluble and Highly Emissive
The correlation between the molecular design of a conjugated polyelectrolyte (CPE) and its aggregated structure and the emissive properties in water is systematically investigated by means of UV–vis spectrometry, fluorescence spectroscopy, and scanning/transmission electron microscopy. Five different and rationally designed CPEs having carboxylic acid side chains are synthesized. All five conjugated polyelectrolytes are seemingly completely soluble in water in visual observation. However, their quantum yields are dramatically different, changing from 0.45 to 51.4%. Morphological analysis by electron microscopy combined with fluorescence spectrophotometry reveals that the CPEs form self‐assembled aggregates at the nanoscale depending on the nature of their side chains. The feature of the self‐assembled aggregates directly determines the emissive property of the CPEs. The nature and the length of the spacer between the carboxylic acid group and the CPE backbone have a strong influence on the quantum yield of the CPEs. Our study demonstrates that bulky and hydrophilic side chains and spacers are required to achieve complete water‐solubility and high quantum yield of CPEs in water, providing an important molecular design principle to develop functional CPEs. The correlation between the molecular design of conjugated polyelectrolytes (CPEs) and their solubility and emissive properties in water is systematically investigated by means of UV–vis and fluorescence spectroscopy and electron microscopy. Bulky and hydrophilic side chains and spacers are required to achieve complete water solubility and high quantum yield of CPEs in water, providing an important molecular design principle to develop functional CPEs.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90088/1/1076_ftp.pd
Clar's Theory, STM Images, and Geometry of Graphene Nanoribbons
We show that Clar's theory of the aromatic sextet is a simple and powerful
tool to predict the stability, the \pi-electron distribution, the geometry, the
electronic/magnetic structure of graphene nanoribbons with different hydrogen
edge terminations. We use density functional theory to obtain the equilibrium
atomic positions, simulated scanning tunneling microscopy (STM) images, edge
energies, band gaps, and edge-induced strains of graphene ribbons that we
analyze in terms of Clar formulas. Based on their Clar representation, we
propose a classification scheme for graphene ribbons that groups configurations
with similar bond length alternations, STM patterns, and Raman spectra. Our
simulations show how STM images and Raman spectra can be used to identify the
type of edge termination
Optical switching studies of an azobenzene rigidly linked to a hexa-peri-hexabenzocoronene derivative in solution and at a solid–liquid interface
THE LINEAR DICHROISM OF CUBIC MOLECULES : DISTORTION AND LOCAL FIELD CONTRIBUTIONS
Le dichroïsme linéaire de W(CO)6, Mo(CO)6 et Cr(CO)6 dissous dans un mélange compensé de dérivés du cholestérol met en évidence la présence des déformations stériques qui peuvent être la cause principale ou secondaire de l'anisotropie optique, l'autre cause étant l'effet des champs diélectriques locaux, l'importance relative des deux facteurs dépendant de la nature des molécules isotropes.The linear dichroism of W(CO)6, Mo(CO)6 and Cr(CO)6 dissolved in an oriented, compensated nematic mixture clearly shows the occurrence of steric deformations which can be the major or minor source of optical anisotropy, together with local dielectric field effects, depending on the nature of the isotropic molecule
Self-Assembly of a Conjugated Polymer: From Molecular Rods to a Nanoribbon Architecture with Molecular Dimensions
Self-Assembly of a Conjugated Polymer: From Molecular Rods to a Nanoribbon Architecture with Molecular Dimensions
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