Published: November 09, 2011 r2011 American Chemical Society 14956 dx.doi.org/10.1021/jp209108r | J. Phys. Chem. B 2011, 115, 14956–14962 ARTICLE pubs.acs.org/JPCB Characterization of Composite PhthalocyanineÀFatty Acid Films from the Air/Water Interface to Solid Supports G. Giancane,* ,† D. Manno, ‡ A. Serra, ‡ V. Sgobba, § and L. Valli † † Dipartimento di Ingegneria dell’Innovazione, Universit  a degli Studi del Salento, I-73100 Lecce, Italy ‡ Dipartimento di Scienze dei Materiali, Universit  a degli Studi del Salento, I-73100 Lecce, Italy § Department of Chemistry and Pharmacy & Interdisciplinary Center for Molecular Materials, Friedrich-Alexander-Universit € at Erlangen-N€ urnberg, Egerlandstrasse, 3, D-91058 Erlangen, Germany ’ INTRODUCTION Chemical and physical properties of phthalocyanines (Pc's) have always attracted the attention of numerous researchers for the diversified applications of these molecules in miniaturized electronic devices such as chemical sensors, 1,2 organic field effect transistors, 3 solar cells, 4 electrochromic 5 and thermochromic apparatuses, 6 laser dyes 7 and many other applications even in the biomedical field, 8 such as in photodynamic cancer therapy. 9 Most of these applications usually stem from the Pc wide flat π-electron cloud, which is responsible of the typical blue-green color of these materials. Pc's comply with the fundamental requisites of chemical and light resistance and mechanical and thermal stability (they are usually sublimed at a temperature of about 500 °C in vacuum, condensing unaltered), all essential for active layers in functioning devices. In the majority of these applications, outstanding performances are observed in highly oriented films obtained by selected film construction techniques. In comparison with methods currently employed in the majority of inorganic systems, the present construction of organic appa- ratuses can be easier, environmentally more friendly, and, above all, economical when commercially available materials (such as the one employed in this research) are used. Among them, several deposition methods can be used to obtain films of Pc's; some of the most appealing are self-organization techniques, such as the LangmuirÀBlodgett (LB) or LangmuirÀSch € afer (LS), self-assembly or layer-by-layer approaches. 10,11 They represent an alternative cost-effective, solution-based transferring method that gives the possibility to tune at the nanometric level the molecular composition, architecture, and thickness of the Pc film. The use of such immobilization methods is necessary since it is well-known that some frontier applications require organized layers of molecular dimensions. Above all, the LB technique is an economic but time-consuming method that allows one to transfer a wide typology of organic materials; the horizontal lifting variation (LS method) offers the chance to construct more rapidly multilayers of organic materials. Organized monolayers of Pc's can be obtained by the attachment of adequate substituents to control the floating filmÀsubphase interaction and to tailor peculiar properties such as light absorption, conductivity, dis- tribution of energy levels, etc. Nevertheless, sometimes the floating layers of Pc's appear inhomogeneous and patchy and with small values of the limiting areas per molecule that are not consistent with the formation of a real monolayer. Therefore, floating films have been also prepared using a mixture of the investigated Pc with arachidic acid (AA), a well-known film- forming material largely used to promote organized LB and LS films. Concerning vanadyl Pc's, an extensive collection of patent literature exists regarding their employment as potential op- tical recording agents, 12 photoreceptors, 13 transistors, 14 and nonlinear optics devices. 15 In this work, a commercial tetra- substituted vanadyl Pc, vanadyl-2,9,16,23-tetraphenoxy-29H, 31H-phthalocyanine (here hence named VOPc) has been char- acterized and transferred onto solid substrates as is and in mixture Received: September 21, 2011 Revised: November 7, 2011 ABSTRACT: A commercial vanadyl 2,9,16,23-tetraphenoxy-29H,31H- phthalocyanine (VOPc) was dissolved in chloroform and spread on ultrapure water subphase in a Langmuir trough. The floating film was thoroughly characterized at the airÀwater interface by means of the Langmuir isotherm, Brewster angle microscopy, UVÀvis reflection spec- troscopy, and infrared measurements carried out directly at the airÀwater interface. All the results showed the formation of a non-uniform and aggregated floating layer, too rigid to be transferred by the LangmuirÀ Blodgett (LB) method. For this reason, a mixture of arachidic acid and VOPc was realized, characterized, and transferred by the LB technique on solid substrates. Interface measurements and atomic force microscopy analysis suggested the formation of a uniform arachidic acid film and a superimposed VOPc placed in prone configuration.