Thin films of phthalocyanines

Thin films of phthalocyanine compounds in general, and those prepared by the LB method in particular, display novel electrical properties (Baker, 1985). The LB technique for depositing mono- and multilayer coatings with well-controlled thickness and morphology offers excellent compatibility with microelectronic technology. Such films have recently been reviewed for their potential applications. The combination of LB supramolecular films with small dimensionally comparable... 

As shown in this symposium, interest in chemical modification of electrode surfaces has been extended in many directions, including the study of light-assisted redox reactions, and the use of modified electrodes in electrochromic devices (1,2). Our own studies have centered on the study of metal and metal oxide electrodes modified with very thin films of phthalocyanines (PC) and on the electrochromic reaction of n-heptyl viologen on metal oxide electrodes, and on the effect on these reactions of changing substrate chemical and physical composition (A,5). 

Bulk Optical Absorption of Phthalocyanine Particles. The visible and near infrared optical absorption of the phthalocyanine pigments was measured on a Cary 17 spectrophotometer using the technique described in Reference 8. A thin film of phthalocyanine dispersed in the polymer was coated onto 3 mil Mylar substrate using wirewound rods. The dry films were index matched by overcoating with a thick film of polyvinyl alcohol. The differential absorption between two films with different thicknesses were recorded to minimize reflection and light scattering losses. The solution absorption spectra of some pigments were also measured in a-chloronapthalene. 

Although there is no tt-tt interaction between phthalocyanines/porphyrins and alcohols, there are many works carried out in sensing alcohols by using thin films of phthalocyanines and porphyrins. LB films of tetra-a-(2,2,4-trimethyl-3-pentyloxy) CuPc show good sensitivity to vapor of alcohol [61]. The response time of the LB film to alcohol is 2 minutes and recovery time is 1 minute. The response should be due to the hydrogen bonding between alcohol and the substituents. 

Kaneko, M., D. Wohrle, D. Schlettwein, and V. Schmidt (1988). Dioxygen sensitivity of a photoexcited thin film of phthalocyanine dispersed in poly(vinylcarbazole). Makromol. Chem. 189, 2419-2425. 

The recovery process a neutral form the phthalocyanine in the presence of Si02 can also be consider as a prototype of the sensing system for a biosensor for the determination of the silica. Therefore, we investigated the influence of alcohol solution on the absorption spectra of thin films of phthalocyanine double-decker lute-tium and ytterbium on polymeric matrices PVP and PVA 4 substrates (Fig. 9.10). 

Nyokong T, Bedioui F (2006) Self-assembled monolayers and electropolymerized thin films of phthalocyanines as molecular materials for electroanalysis. J Porphyr Phthalocya 10 1101-1115... 

Nyokong T, Bedioui F (2006) Self assembled monolayers and electropolymerized thin films of phthalocyanines as molecular materials for electroanalysis. J Praph Phthal 10 1101-1115 Salomon E, Angot T, Papageorgiou N, Layet JM (2005) Self-assembled monolayer of tin-phthalocyanine on lnSb(0 0 l)-(4 x 2)/c(8 x 2). Surf Sci 596 74—81... 

The electrochromism of the phthalocyanine ring-based redox processes of vacuum-sublimed thin films of [Lu(Pc)2] was first reported in 1970,32 and since that time this complex has received most attention, although many other (mainly lanthanide) metallophthalocyanines have been investigated for their electrochromic properties.1 Lu(Pc)2 has been studied extensively by Collins and Schiffrin33,34 and by... 

Monolayer Films of Phthalocyanine Derivatives. A series of organic derivatives of phthalocyanines were prepared that have two important characteristics of materials to be deposited by the Langmuir-Blodgett technique (1) they are soluble in volatile organic solvents, and (2) they form monomolecular films on the surface of water. Further study of deposited films of these phthalocyanine derivatives will be necessary in order to determine the exact orientations on the surface, but regardless of their orientations, they offer interesting possibilities for construction of thin films of ordered arrays of molecules on the surface of gas sensors. 

Ashida, M. Uyeda, N. and Suito, E. (1971). Thermal transformation of vacuum condensed thin films of copper phthalocyanines. /. Cryst. Growth, 8,45-56. [268] Ashizawa, K. (1989). Polymorphism and crystal structure of 2R,4S,6-fluoro-2methyl-spiro[chroman-4,4 -imidazoline]2 -5-dione(M79175). J. Pharm. ScL, 78, 256-60. [129]... 

Suspensions of polyacetylene were prepared as burrs or fibers (46) by using a vanadium catalyst. When the solvent was removed, films of polyacetylene were formed with densities greater than that prepared by the Shirakawa method. These suspensions were mixed with various fillers to yield composite materials. Coatings were prepared by similar techniques. Blends of polypyrrole, polyacetylene, and phthalocyanines with thermoplastics were prepared (47) by using the compounding techniques typically used to disperse colorants and stabilizers in conventional thermoplastics. Materials with useful antistatic properties were obtained with conductivities from 10" to 10" S/cm. The blends were transparent and had colors characteristic of the conducting polymer. For example, plaques containing frans-polyacetylene had the characteristic violet color exhibited by thin films of solid trans-polyacetylene. 

J. Spadavecchia, G. Ciccarella, P. Siciliano, S. Capone, R. Rella, Spin-coated thin films of metal porphyrin-phthalocyanine blend for an optochemical sensor of alcohol vapors. Sen. Actuators, B, Chem 100, 88-93 (2004). 

Table 3.1 Experimental positions of highest occupied electronic levels (IP, determined by UPS) and lowest unoccupied electronic levels (EA, determined by IPES) in thin films of partly fluorinated phthalocyanines.

Table 1 summarizes the analytical results obtained for the thermal reaction of I and of VI. With the exception of the experiment in which methanol was added to VI, the extent of phthalocyanine formation was very small. Moreover, the infrared spectra of these reacted samples exhibited absorptions characteristic of amide or imide carbonyl as well as those for tria-zine. Under these conditions, phthalocyanine formation is not favored. For example, the yield of phthalocyanine ring formation, based on the consumption of starting material, was less than 5% for the model phthalonitrile VI, and less than 10% for the bis-phthalonitrile I. In a separate experiment a thin film of I deposited on a salt plate was allowed to cure while exposed to the atmosphere. Periodic infrared examination of the curing film showed that as the cyano absorbance diminished the absorbance in the carbonyl region increased until the latter was the predominant infrared band. These results demonstrate that... 

Compact chemical sensors can be broadly classified as being based on electronic or optical readout mechanisms [28]. The electronic sensor types would include resistive, capacitive, surface acoustic wave (SAW), electrochemical, and mass (e.g., quartz crystal microbalance (QCM) and microelectromechanical systems (MEMSs)). Chemical specificity of most sensors relies critically on the materials designed either as part of the sensor readout itself (e.g., semiconducting metal oxides, nanoparticle films, or polymers in resistive sensors) or on a chemically sensitive coating (e.g., polymers used in MEMS, QCM, and SAW sensors). This review will focus on the mechanism of sensing in conductivity based chemical sensors that contain a semiconducting thin film of a phthalocyanine or metal phthalocyanine sensing layer. 

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