P. C. M. Grim

Expression of chirality by achiral coadsorbed molecules in chiral monolayers observed by STM

The supramolecular packing mode of physisorbed monolayers built up by chiral isophthalic acid derivatives and coadsorbed achiral solvent molecules was imaged at the liquid/graphite interface with scanning tunneling microscopy (STM). The picture on the right shows the submolecularly resolved STM image of an enantiomorphous domain composed of the R enantiomer of the isophthalic acid derivative studied and 1-heptanol molecules; the latter express the chirality of the monolayer. Upon adsorption a racemic mixture is separated into enantiomorphous domains.

Molecular organization of azobenzene derivatives at the liquid/graphite interface observed with scanning tunneling microscopy

Physisorbed monolayers of azobenzene derivatives were studied with a scanning tunneling microscope at the liquid/graphite interface. Three different compounds, namely, 4,4′-di(dodecyloxy) azobenzene (C12(AZO)C12), 5-[ω-(4′-dodecyloxy-4-azobenzene-oxy)dodecyloxy] isophthalic acid (C12(AZO)C12ISA), and 4,4′-bis(ω-[3,5-bis(carboxylato) phenyl-1-oxy] dodecyloxy) azobenzene (ISAC12(AZO)C12ISA) have been investigated. In all cases monolayers could be observed with submolecular resolution at the liquid/graphite interface, allowing one to identify the azobenzene, as well as the other parts of the molecules. For each monolayer structure a molecular model could be composed with a good correspondence to the experimental data. Differences in the observed monolayer structures could be related to the chemical structure of the investigated compounds. The introduction of an isophthalic acid (ISA) headgroup has a profound influence on the monolayer structure because of its capability of hydrogen bond formation with other ...

Insolubilisation and Fluorescence, Induced by Laser Diode Irradiation of IR-Dyes Embedded in Polymer Films

The heat dissipated during non-radiative deactivation of dyes, embedded in a polymer matrix and excited by a diode laser of 839nm, can significantly increase the film temperature and induce not only physical changes of the film properties but also chemical changes of the composition in the film. Diffuse reflectance spectroscopy (DRS) and atomic force microscopy (AFM) showed that irradiation with IR-light of films containing latex particles and an IR-dye, embedded in a matrix polymer, can lead to the physical coalescence of the latex particles, and substantially decreases the solubility of the film. Laser scanning confocal microscopy (LSCM) analysis of films, containing an IR-dye, an acid generator and an acid sensitive fluorescent probe, and irradiated with an IR diode laser, showed image-wise the infrared light induced fluorescence resulting from the thermally stimulated acid release by the chemical decomposition of the acid generator in the polymer film. The LSCM analysis also nicely showed that the processes in the films, induced by the infrared light irradiation, strongly depend on the nature of the polymer matrix in which the compounds are embedded.