Phthalocyanine Monolayers Research Articles

Structure of ultrathin films of chloroalminium phthalocyanine on MoS 2 studied by means of penning ionization electron spectroscopy, angle-resolved UPS and LEED

The structure of ultra-thin films (0.5–5 monolayers) of chloroalminium phthalocyanine (ClAlPc) on an MoS 2 substrate was studied by Penning ionization electron spectroscopy (PIES), angle resolved ultraviolet photoelectron spectroscopy (ARUPS) and low-energy electron diffraction (LEED). The change in the molecular orientation was sensitively detected during the variation of the thickness and temperature of the film.

Formation and characterisation of a self-assembled phthalocyanine monolayer suitable for gas sensing

Abstract The formation and characterisation of a novel self-assembled monolayer film for gas sensing are reported. The phthalocyanine 1,1′4,4′,8,8′,11,11′,15,15′,18,18′,22,22′-tetradecakishexyl-225,25′-(3,3′-dithiodipropyl)diphthalocyanine, has been synthesised from its hydroxypropyl precursor, via a two-step reaction. The disulfide functionality of the molecule has been used to produce a self-assembled phthalocyanine monolayer on a gold substrate. The phthalocyanine monolayer has been characterised using reflection absorption infrared spectroscopy (RAIRS).

Observation of Outermost Surface Layers of Phthalocyanine Ultra-Thin Films by Penning Ionization Electron Spectroscopy: Chloroaluminium Phthalocyanine on MoS2

Abstract Using Penning ionization electron spectroscopy, which provides information on the local distribution of the individual orbitals exposed outside the outermost surface layer, ultra-thin films (1 to several monolayers) of chloroaluminium phthalocyanine were characterized during layer-by-layer vacuum deposition onto an MoS2 substrate and the change in the molecular orientation was sensitively detected.

Characterization of Ultrathin Films of Chloroaluminum Phthalocyanine during Layer-by-Layer Preparation on Graphite: PIES and UPS Study

Penning ionization electron spectroscopy and ultraviolet photoelectron spectroscopy were used to characterize ultrathin films (one to several monolayers) of chloroaluminum phthalocyanine during layer-by-layer vacuum deposition onto a graphite substrate. At one monolayer, molecules deposited on the substrate held at room temperature are oriented flat to the substrate with the chlorine atom protruding outside the film surface. With increasing film thickness, molecules are gradually tilted in subsequent layers. The monolayer film deposited on the substrate at -170 C shows a disordered molecular arrangement (tilted molecules), but the change in the arrangement, disordered (tilted) to ordered (flat), is observed upon heating the film up to 100 C.

Large Molecule Epitaxy on Single Crystal Metals, Insulators and Single Crystal and MBE-Grown Layered Semiconductors

We review the packing structures for a series of aromatic hydrocarbons, deposited by vacuum deposition methods as ordered monolayers→→multilayers, on a variety of metal, semiconductor and insulator surfaces. New results are presented for the adsorption of monolayers of perylenes, phthalocyanines, coronene, and pentacenes on the Cu(100) surface, along with the implications of these studies for the formation of ordered multilayers of these molecular systems. Aromatic molecules without heteroatoms appear to pack in a flat-lying motif, and exhibit approximately hexagonal close packing, even on a substrate with four-fold symmetry such as Cu(100). In general, aromatic systems whose bulk structures lend themselves to layer-by-layer growth during vacuum deposition appear to be the best candidates for ordered multilayer growth.

Resonance Raman spectra of phthalocyanine monolayers on different supports. A normal mode analysis of zinc phthalocyanine by means of the MNDO method

AbstractResonance Raman spectra of monolayers of transition metal phthalocyanines reveal specific interaction with the support. To elucidate its mechanism, Raman spectra of zinc phthalocyanine monolayers were studied. The analysis was based largely on the results of MNDO calculations. Calculated wavenumbers turned out to be in good agreement with the experimental results. It seems plausible that the α‐nitrogen atoms dominate the interaction with the support. Calculation results also show that the usually assumed D4h geometry does not represent the true energy minimum but must be considered as the ‘mean’ of two mesomeric forms.

Formation and characterization of epitaxial phthalocyanine and perylene monolayers and bilayers on Cu(100): Low-energy electron diffraction and thermal desorption mass spectrometry studies

Ordered monolayer and multilayer thin films of copper phthalocyanine (CuPc) and perylene dicarboxylic dianhydride (PTCDA) have been grown on Cu(100) single crystals. CuPc grows in a commensurate square lattice configuration, with two equivalent domains consisting of closest packed, flat lying Pc rings, rotated at ±21.8° from the principle Cu(100) axes. The dimensions of these square lattices (b1=b2=13.7 Å) are comparable to those observed using other substrates which interact weakly with the Pc overlayer (layered metal dichalocogenides, cleavage faces of single-crystal salts). PTCDA grows in a commensurate rectangular lattice (5√2×4√2)-R=45°, whose dimensions (b1=14.5 Å, b2=18.1 Å) are significantly different than those seen on weakly interacting substrates. Low-energy electron diffraction (LEED), x-ray photoelectron spectroscopy, and thermal desorption mass spectroscopy (TDMS) data for the adsorption of this molecule strongly suggest that the first monolayer is dissociatively adsorbed to the Cu(100) surface. Growth of ordered layers of PTCDA has also been carried out on a Cu(100) surface modified with 1–2 ML (monolayers) of an ordered CuPc film. LEED and TDMS data indicate the formation of a new commensurate rectangular unit cell (b1=13.7 Å, b2=20.5 Å) for these PTCDA/CuPc/Cu(100) overlayers, which suggest that the CuPc layer controls the architecture of the subsequent PTCDA layers. The formation of a wide range of highly ordered organic heterojunctions appears to be possible, starting with a strongly adsorbed first layer, on surfaces such as single-crystal metals.

Epitaxial phthalocyanine thin films and phthalocyanine/C 60 multilayers

Ordered ultrathin films of various dye molecules can be created by vacuum deposition onto a variety of substrates where the interaction with the overlayer is weak and intermolecular forces dominate the ordering process. Examples are shown for the surface electron diffraction data obtained from ordered monolayers of phthalocyanines on metal dichalcogenide surfaces and the corresponding linear optical changes which result from the formation of thin multilayers of those dyes. Organic/organic' multilayer assemblies are also presented, consisting of alternating layers of the fullerene C 60 and InPc-Cl, which show promise for the formation of true organic superlattices, where excitonic interactions are confined in two dimensions.

Raman spectra of zinc phthalocyanine monolayers adsorbed on glassy carbon and gold electrodes by application of a confocal Raman microspectrometer

Raman spectra of zinc phthalocyanine monolayers, adsorbed on gold and on glassy carbon surfaces (electrodes), are presented. These spectra have been recorded with the electrodes inside and outside an electrochemical cell filled with an aqueous electrolyte. A confocal Raman microspectrometer was used. It was demonstrated that, because this spectrometer uses low laser intensifies, no damage of the monolayer occurred. The results show that the interaction of the phthalocyanine molecule with gold differs from that with glassy carbon. Because the laser excitation wavelength (660 nm) coincides with a UV-visible absorption band (Q band), a strong resonance- enhanced Raman spectrum was obtained. No signs of surface enhancement (surface-enhanced Raman scattering) effects were detected.

Spectroscopic studies of phthalocyanine monolayers

Spectroscopic studies of phthalocyanine monolayers

Monolayer characteristics of some multinucleate phthalocyanines

Surface pressure-area isotherms were established for a series of seven derivatized phthalocyanine compounds containing from one to four covalently linked macrocycles. Good solubility in spreading solvents was conferred by the presence of four neopentoxyl groups per macrocycle. All compounds studied formed strong, stable monolayers with high breaking pressures (about 50 mN m −1 or greater). Observed surface pressure-area isotherms were of the most simple kind, with no indication of phase transitions or discontinuities, with one exception. Minimal molecular areas were seen at lowest compression rates and higher temperatures, indicating that these systems have a large number of configurational states which are not capable of restructuring quickly into a compact monolayer of highest density. For some compounds it appears that orientation on the water surface can be essentially flat. Most previously studied phthalocyanine monolayers suggest that the macrocycles tend always to orient edge-on at some acute angle to the water surface because of the very strong cofacial energies of interaction. With other compounds of this group, it is evident that the macrocycles can assume orientations either parallel or perpendicular to the surface, others having intermediate orientations as well. In addition, one multinucleate compound probably assumes a bilayer structure at high surface pressures. The range of orientations available in these systems should appreciably extend the utility of phthalocyanines in monolayers transferred by the Langmuir-Blodgett technique. The present study indicates that a more complete exploitation of the possibilities of organic synthesis can result in a more varied monolayer behavior than seen hitherto.

Langmuir-Blodgett monolayers studied by surface-sensitive X-ray absorption fine structure

A surface-sensitive X-ray absorption fine structure was obtained for copper phthalocyanine Langmuir-Blodgett monolayers. The polarized Cu K near-edge structure is interpreted as evidence for the orientation of copper phthalocyanine monolayers in such a way that the porphyrin plane faces the dipping direction with tilted normal axis, ruling out a possible orientation of the porphyrin plane parallel to the substrate.

Recent studies in phthalocyanine chemistry

Abstract

Langmuir-Blodgett films of soluble copper octa(dodecoxymethyl) phthalocyanine

In this paper, the preparation and characterization of Langmuir-Blodgett monolayers of copper octa(dodecoxymethyl) phthalocyanine will be discussed. The monolayers of this soluble phthalocyanine on water are stable to film pressures greater than 30 dyn cm -1. The surface pressure versus surface area curves indicate that the phthalocyanine molecules are oriented with the planar rings parallel to the air-water interface. The monolayers have been transferred from water onto glass coated with aluminum or indium tin oxide. Multiple layers have also been built up on these substrates. Characterization of the phthalocyanine films on glass coated with indium tin oxide indicates the presence of some degree of molecular aggregation in the films, while molecular ordering in the films is indicated by polarized electronic absorption spectroscopy.

Electronic devices incorporating stable phthalocyanine Langmuir-Blodgett films

This paper describes the critical role of the solvent in the preparation of monolayers of phthalocyanine. Pressure-area isotherms demonstrate that realistic monomolecular areas can be achieved for a number of compounds provided that the central hydrogen atoms in the ring system are replaced by appropriate metal ions. Particularly good results have been obtained with an asymmetrically substituted copper phthalocyanine. Transmission electron diffraction data for copper phthalocyanine tris(CH 2NHC 3H 7-iso) show a preferred orientation over a sample region of 3 mm. The excellent stability of the Langmuir-Blodgett films has enabled us to incorporate them in a number of electronic devices. These include a gas-sensitive structure based on silicon, a bistable switch using GaAs and an electroluminescent metal-insulator-semiconductor ZnSeS diode.

Surface-enhanced Raman scattering of Langmuir-Blodgett monolayers of phthalocyanine by indium and silver island films

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSurface-enhanced Raman scattering of Langmuir-Blodgett monolayers of phthalocyanine by indium and silver island filmsRicardo Aroca, Carol Jennings, G. J. Kovac, Rafik O. Loutfy, and P. S. VincettCite this: J. Phys. Chem. 1985, 89, 19, 4051–4054Publication Date (Print):September 1, 1985Publication History Published online1 May 2002Published inissue 1 September 1985https://doi.org/10.1021/j100265a025RIGHTS & PERMISSIONSArticle Views272Altmetric-Citations60LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (495 KB) Get e-Alerts

The surface structures of phthalocyanine monolayers and vapor-grown films: A low-energy electron diffraction study

Monolayer structures and epitaxial growth of vapor-deposited crystalline phthalocyanine films on single-crystal copper substrates were studied using low-energy electron diffraction. At monolayer coverage, ordered layers of copper-, iron-, and metal-free phthalocyanines were observed on both Cu(100) and Cu(111). With increasing film thickness, ordered multilayer structures of these phthalocyanines were also seen on both substrates at 300 K surface temperature. All three phthalocyanines had identical monolayer and multilayer surface structures on Cu(100). On the Cu(111) substrate, the three phthalocyanines exhibited slightly different surface structures, indicating the importance of the central metal atom in the interaction with the substrate that influences the monolayer surface structure and the ordering during crystal growth. The multilayer crystalline films did not have surface structures characteristic of the bulk crystal structure but rather had a surface unit mesh compatible with a single molecule per unit mesh, oriented parallel to the surface. Electron beam damage and space charge effects were negligible for film thicknesses up to 500–1000 Å.