Andrzej Biadasz

Optical spectroscopy study of some 3,4,9,10-tetra-(n-alkoxy-carbonyl)-perylenes in Langmuir–Blodgett films

Abstract Langmuir (L) and Langmuir–Blodgett (LB) films of some 3,4,9,10-tetra-( n -alkoxy-carbonyl)-perylenes have been studied. On the basis of the surface pressure–mean molecular area isotherms, the molecular alignment on the air–water interface has been estimated. The optical spectroscopic study of the LB films has allowed conclusions to be drawn about the arrangement of the molecules on the quartz slides. The fluorescence spectra of the LB films of the perylene-derivatives investigated have revealed the formation of excited dimers.

Molecular organization in binary mixtures of derivatives of naphthalenebicarboxylic acid and naphthoylenebenzimidazole with a liquid crystal in two-dimensional layers II. Langmuir-blodgett films

Langmuir–Blodgett (LB) films of some dichroic dyes, namely derivatives of naphthalenebicarboxylic acid and derivatives of naphthoylenebenzimidazole, and of their mixtures with mesogens: 4‐octyl‐4′‐cyanobiphenyl or 4‐pentyl‐4″‐cyano‐p‐terphenyl were prepared. Absorption and fluorescence studies using unpolarized and linearly polarized light were carried out. Both absorption and fluorescence spectra indicated the formation of aggregates of dye molecules in monomolecular layers. Moreover, it was found that dye molecules are more tilted to the quartz surface in LB films than to the plane of the air–water interface in Langmuir films.

Langmuir films of dichroic dyes with fluorescent properties

Abstract Langmuir films of various dyes, namely derivatives of 3,4,9,10-perylenetetracarboxylic acid and 3,4,9-perylenetricarboxylic acid, derivatives of naphthalenebicarboxylic acid and derivatives of naphthoylenebenzimidazole were investigated. Surface pressure–mean molecular area isotherms were recorded from which the alignment of the molecules in a monomolecular layer at the air–water interface was determined. It was found that both the stability and the rigidity of the monolayer are strongly affected by the molecular structure of the side groups substituted on the skeleton of the molecule.

Alignment of liquid crystal and dichroic dye molecules in mixed Langmuir and Langmuir-Blodgett films

A study of dichroic dye-liquid crystal mixtures (guest-host systems) in monolayers formed at a gas-liquid interface (Langmuir films) and at a solid surface (Langmuir-Blodgett films) has been made. As a host 4- n -octyl-4′-cyanobiphenyl (8CB) or 4- n -pentyl-4″-cyano- p -terphenyl (5CT) were chosen, while three dichroic azo dyes with various molecular structures were used as guest species. The dyes were added to the liquid crystal matrices at a concentration corresponding to the whole range of molar fractions and the surface pressure-mean molecular area isotherms for Langmuir films were recorded. On the basis of the isotherms, conclusions about the molecular organization and the miscibility of the components in the ultrathin films were drawn. The Langmuir films were transferred onto the quartz plates at surface pressures below the collapse point. The polarized absorption spectra of the Langmuir-Blodgett films were recorded and information about the alignment and intermolecular interactions in the mixtures of the non-amphiphilic dichroic dyes and the liquid crystals with strongly polar terminal groups were obtained.

Indium–chlorine and gallium–chlorine tetrasubstituted phthalocyanines in a bulk system, Langmuir monolayers and Langmuir–Blodgett nanolayers – Spectroscopic investigations

The paper deals with spectroscopic characterization of metallic phthalocyanines (Pcs) (indium and gallium) complexed with chlorine and substituted with four benzyloxyphenoxy peripheral groups in bulk systems, 2D Langmuir monolayers and Langmuir-Blodgett nanolayers. An influence of the molecular structure of dyes (the presence of metal and of substitutes attached to the phthalocyanine macroring) on the in situ measurements of light absorption is reported. Molecular arrangement of the phthalocyanine molecular skeleton in the Langmuir monolayers on water substrate and in the Langmuir-Blodgett nanolayers is evaluated. A comparison of the light absorption spectra of the phthalocyanine monolayers with the spectra of the dyes in solution supports the existence of dye aggregates in the monolayer. It was shown that the type of dye aggregates (oblique and H types) depends markedly on the dye molecular structures. The NIR-IR, IR reflection-absorption and Raman spectra are also monitored for Langmuir-Blodgett nanolayers in non-polarized and polarized light. It was shown that the dye molecules in the Langmuir-Blodgett layers are oriented nearly vertically with respect to a gold substrate.

Raman and infrared studies of molecular orientation in fullerene–thiophene films

The paper deals with spectral studies (IR absorption, IR reflection–absorption, Raman scattering, and electronic absorption) of Langmuir–Blodgett layers of selected fullerene–thiophene dyads; some information on preparation and properties of the layers are also given. The spectra were recorded with unpolarised and polarised light (p-polarisation and s-polarisation) to receive data on orientation of the dyads with respect to the solid substrate and on interaction of the dyads with gold substrates. The comparison of the dyad spectra suggests redistribution of charges in both moieties of the dyads after films deposition on the substrate. We have shown that the polarised reflection–absorption spectra of the thin films are strongly dependent on the light polarisation. From the analysis of the data on the basis of the results obtained from various spectral methods it was concluded that the Langmuir–Blodgett layers are ordered and some parts of the dyads are oriented.

Morphology and molecular organisation of liquid-crystalline perylene-3,4,9,10-tetra-(n-hexylester) deposited on a solid substrate

Liquid-crystalline perylene-3,4,9,10-tetra-(n-hexylester) forms characteristic dendritic or flower-like structures at room temperature when it is deposited on a hydrophilic glass substrate using the zone-casting technique. It was found that such unique structures were not possible to be created simply by recrystallisation of this dye from a liquid-crystalline columnar phase. On the basis of the observations using a confocal microscope and the study of wide angle X-ray scattering (WAXS) as well as the analysis of the absorption and fluorescence spectra, some conclusions, concerning the molecular organisation in the dendritic structure, are drawn. Based on the research, one can assume that the dendrites are formed by columnar molecular aggregates with the column axes parallel to the substrate. Such an organisation of the molecules can be interesting from the point of view of organic electronics.