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Double- and triple-decker phthalocyanine derivatives have been successfully used as the sensitive materials for liquid electrochemical sensors. The materials include homoleptic and heteroleptic phthalocyanine complexes formed by phthalocyanine, porphyrin and naphthalocyanine rings. A high degree of cross-selectiviy towards antioxidant compounds (including vannilic acid, pyrogallol, ascorbic acid and catechin) has been attained by using different phthalocyanine complexes. The features observed in the cyclic voltammograms reflect the rich electrochemistry of either the phthalocyanine molecules or the studied solutions. In consequence, each sensor shows a selective response to the antioxidant analysed. The obtained voltammograms from by using highly ordered electrodes prepared using the Langmuir–Blodgett (LB) or the Langmuir–Schaefer (LS) techniques show better resolution and stability than those of disordered electrodes prepared by casting. For this reason, ordered films have been chosen to construct an array of liquid sensors. The principal component analysis (PCA) of the obtained signals has allowed that a clear discrimination of the antioxidant solutions be achieved. The rich and varied responses produced by antioxidant molecules evidences that voltammetric

Phthalocyanines are macrocycles with an appealing diversification of characteristics of fundamental interest in contemporary advanced technologies. On the other side, the Langmuir–Blodgett method permits to deposit films with a substantial control over thickness and molecular organisation. As a natural consequence, this review deals with an actual subject of attention in up-to-date research, the employment of Langmuir–Blodgett films of phthalocyanines in chemical sensors for the revelation of analytes in both gas and liquid phases. Experimental data on the structure, morphology and surface properties of the multilayers are connected with the most relevant characteristics of sensors, in order to discover the intimate relationships between the sensor performances and the peculiarities and molecular organisation induced by the deposition technique. The integration of the unconventional electrical and optical properties of phthalocyanines with the potentialities of the Langmuir–Blodgett thin films has generated not only promising expectations, but has given also certainties about the realisation of functional sensing devices.

Thin films of metal phthalocyanines (MPc) are known to exhibit excellent physical properties but poorly controlled morphologies. Therefore, the present work seeks to understand the film growth mechanism of a model compound for potentially usable MPc, specifically, copper tetra(3-nitro-5-tert-butyl)phthalocyanine (CuPc*). The Langmuir-Schaefer (LS) technique was applied to prepare a series of CuPc* films under different processing conditions. The film growth was examined by Brewster angle microscopy (BAM) on the water surface and small-angle X-ray scattering (SAXS) from the solid films. Neutron reflectometry (NR) measurements of the water uptake into the films and computer simulation of hydrated CuPc* were performed to substantiate an idea of colloidal MPc-water aggregates as nanoscale precursors of smooth solid films. This idea appears fruitful in terms of materials chemistry.

Time travel through 150 years of Italian postage stamp issues has allowed defining the evolution of the recurring pigments in stamp designs by means of Raman and FTIR spectroscopy. Numerous exemplars have been analyzed, covering the entire production of stamps for both the Italian Kingdom and Republic. Raman and FTIR spectra showed the changeover from Prussian blue to copper phthalocyanine inks in 1958. The entire succession for red inks was also recognized to develop from the original cinnabar to red ochre and minium and finally to red azo pigments. The changes in orange printing ink proceeded on a similar path. The first orange Italian exemplar was printed employing a mixture of chrome orange and red ochre. In 1929 this combination was replaced by azo pigments. Green stamps belonging to the first issues entailed the choice of blue and orange inks, namely chrome orange and Prussian blue. Later on, an ink composed mainly of phthalocyanine was employed as the green dye. The merging of data coming from Raman microscopy and FTIR-ATR spectroscopy, both non-destructive techniques, has allowed the characterization of stamp designs and potentially provides direct and fast evidence for the recognition of forged exemplars.

This paper reports the use of optical trasduction techniques to characterise solid state chemo-optical sensors prepared by Langmuir–Schafer technique (LS) in thin film form based onto Cu(II) tris-(2,4-di- t -amylphenoxy)-(12-hydroxy-1,4,7,10-tetraoxadodecyl)-phthalocyanine macromolecules CuPcOH as active layers. The study consists in the UV–vis optical absorption monitoring of the active LS layers in the presence of specific five volatile organic compounds (VOCs) mixed in dry air in controlled atmosphere; in particular tert -butylamine, methanol, ethanol, hexane and ethyl acetate, all analytes of interests in the food quality control. The UV–vis spectra have been monitored by recording the dynamic variation in the integral of the absorbance curves in well defined spectral regions: 300–400 nm, 550–600 nm, 600–640 nm, 640–700 nm, covering the whole spectrum and centred around the typical absorption bands of phthalocyanine thin films. This simultaneous UV–vis four channel monitoring allowed to use only one active layer as sensing element where each selected spectral region generates independent sensors. The dependency of the above mentioned outputs towards the analytes has been discussed. A base optical characterisation of the investigated LS thin films has been performed.

The sensitivity of gadolinium bis-phthalocyanine assemblies to different concentrations of NO2 has been studied. Gold (on chrome) interdigitated electrodes on glass were passed through a floating Langmuir monolayer at 1000 mm min−1 for 20 excursions. This ultra-fast technique has greatly reduced the time needed to manufacture samples and has led to a defect structure in the deposited layers with an enhanced surface area to volume ratio. The resulting films were tested as chemiresistors in low concentrations of NO2 (0.25–4 ppm). A highly linear calibration plot (fractional current vs. concentration plot) was obtained over the concentration range 0.25–1.0 ppm, with a gradient of ∼210% ppm−1.

An octa-substituted copper phthalocyanine was dissolved in chloroform and spread on ultrapure water subphase in a Langmuir trough. The floating films were characterized at the air-water interface by the Langmuir isotherm, Brewster angle microscopy, and UV-Vis reflection spectroscopy and transferred by Langmuir-Schafer technique on a silicon substrate, and thickness, refractive index, and extinction coefficient of the phthalocyanine derivative thin film were calculated by means of spectroscopic ellipsometry. A different number of layers were deposited using Langmuir-Schafer method onto QCM crystals, and the active layers were tested as sensors for the detection of phenols in aqueous solution. The piezoelectric sensor response, totally reversible, is influenced by the number of transferred layers and by the nature of the substituent; on the contrary, the pK(a) value of the injected analytes slightly affects the device performances. Repeatability of the sensor responses was tested, and the frequency variation appears unchanged at least for 100 days.

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 air-water interface by means of the Langmuir isotherm, Brewster angle microscopy, UV-vis reflection spectroscopy, and infrared measurements carried out directly at the air-water interface. All the results showed the formation of a non-uniform and aggregated floating layer, too rigid to be transferred by the Langmuir-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.

Langmuir–Schaefer (LS) films of copper(II) tetrakis-(isoprpoxy-carbonyl)-phthalocyanine (TiPCuPc) have been deposited onto various solid supports. Its floating film have been characterized at the air–water interface by means of Brewster Angle Microscopy and Langmuir curves. Vibrational modes of multilayer transferred LS film have been studied by Raman spectroscopy and the optical parameters (refractive index n and extinction coefficient k ) have been determined in the visible range of the electromagnetic spectrum. Linearly polarized light absorbance measurements have been performed at room temperature in the 400–800 nm spectral range and the average orientation of the phthalocyanine rings have been estimated. Transmission electron microscopy has been also used to characterize the morphological properties of the LS film and a close packed arrangement of the deposited molecules has been observed.

Thin films of pure tetrakis-(isopropoxy-carbonyl)-copper-phthalocyanine (TIPCuPc) , a novel functionalized phthalocyanine, and its hybrid junctions with colloidal rod-like TiO2 nanocrystals (NCs) were deposited in order to elucidate their properties and application in piezoelectric chemical sensors. The strong tendency of the phthalocyanine to assembly was confirmed at the air/water interface by advanced Brewster Angle Microscopy (BAM) and UV-vis reflection spectroscopy techniques. In particular, H-type aggregates, in situ and at the air/water interface, self-associate in aligned 3D bulky domains. The characteristics of the molecule and of the assemblies were studied in the solid state by means of UV-vis spectroscopy, Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR) spectroscopy and Atomic Force Microscopy (AFM). These studies prompted investigation of the operating conditions to process the bare TIPCuPc and related TiO2 NC-based hybrid junctions as sensing active layers for phenol pollutants integrated in a Quartz Crystal Microbalance (QCM). Interestingly, the preferentially oriented phthalocyanine LB-film undergoes chemical interactions with the NC film, which enhances the sensitivity of the QCM sensor.

This article reports on an extensive investigation on a functionalized phthalocyanine, namely, copper(II) tetrakis-(isopropoxy-carbonyl)-phthalocyanine (TIPCuPc). The self-association of the molecules is extensively described in solution in different solvents (DMSO, DMF, CHCl(3), pyridine) by means of UV-vis steady state spectroscopy at the air/water interface by Brewster angle microscopy (BAM) and in thin films by using atomic force microscopy (AFM). We investigated the morphology of TIPCuPc as thin film by evaluating different factors: temperature, solvent, concentration, transferring procedure (spin-coating and Langmuir-Schafer technique), and nature of the substrate (mica and quartz). The behavior of the molecules under UV light irradiation and their thermal stability were studied as well. Such a detailed study can allow a suitable processing of this phthalocyanine derivative for future applications. Here the photoelectrochemical activity of the phthalocyanine was investigated when suitably combined as sensitizer with rodlike TiO(2) nanocrystals (NCs) in hybrid junctions integrated in a photoelectrochemical cell.

The Langmuir–Schaefer technique has been used to fabricate ordered monolayers of novel heteroleptic double and triple-decker phthalocyanine derivatives. The molecules studied include a double-decker mixed porphyrinate and naphthalocyaninate lanthanum(III) compound and a europium triple-decker molecule where one of the rings is a substituted porphyrin and the two remaining rings are substituted phthalocyanine macrocycles. The materials and their films have been characterised using UV–vis–NIR spectroscopy and electrochemistry. The UV–vis–NIR spectra of the solutions show the expected features corresponding to the aromatic rings present in each molecule. The absorption spectra of LS films show broadenings and important shifts to higher wavelengths when compared to the electronic absorption spectra of solutions or disordered cast films. Thin films are sensitive to electron acceptor gases, such as NOx as observed by modifications in the electronic absorption spectra of the films. These fast and reversible changes can be the basis of optical sensors based on thin films of heteroleptic phthalocyanines (Pc). Cyclic and square wave voltammograms of dichloromethane solutions lead to rich curves where a variety of peaks are observed. The voltammogrames of the corresponding films also reflect the rich electrochemical properties of the studied compounds. Electrochromism has been found with LB and cast films electrodes in KCl and KClO 4 solutions: important changes in the UV–vis–NIR spectra registered in situ simultaneously to the application of the electrical potential have been observed. The rich electrochemistry and the electrochromism observed, opens the possibility of using such films in multicolour electrochromic devices. Films prepared onto ITO glass show characteristic electrochemical responses when exposed to solutions of organic compounds, such as ascorbic and vanillic acid, providing a high degree of cross-selectivity. This effect can be used in the development of arrays of sensors used in electronic tongues. In summary Langmuir–Schaefer films of heteroleptic double and triple-decker phthalocyanines could be of interest at least in three potential applications: thin film electrochromic devices, optical gas sensors and voltammetric sensors.

By means of microgravimetry, UV-Vis spectroscopy and optic microscopy, sorption of pyridine, primary aliphatic amines and benzylamine by the Langmuir-Blodgett (LB) films of tetra-4-tert-butyl- and tetra-(3-nitro-5-tert-butyl)-substituted cobalt phthalocyanines (CoPc' and CoPc*, respectively) was studied over a broad concentration range. In general, sorption occurs as stepwise intercalation of the sorbate molecules into the supramolecular 3D structure of the phthalocyanine assembly followed by formation of the donor-acceptor complexes. Both intercalation depth and stoichiometry of the complexes are determined by the molecular structure of amines. The supramolecular factor allows discrimination between amines in air but not in aqueous solutions because of concurrent intercalation of water.

The interaction between gas mols. and the active surface of thin org. film can generate variation in the phys. properties of the layer. Here, spin coated layers of 4 metallophthalocyanines which were used as optochem. interactive materials are reported together with a discussion concerning the preliminary data obtained with optical absorbance measurements in UV-vis spectral range onto these optical sensitive sensors. Glass substrates coated with metallophthalocyanine show good sensitivity and selectivity depending both on the metal and the peripheral substituents. A certain sensitivity towards tert-butylamine, diethylamine, dibutylamine, 2-butanone and acetic acid was found.

Chemical sensors based on surface plasmon resonance (SPR) measurements have been proposed in various applications ranging from biomedical and environmental monitoring to industrial process control. It is widely gaining recognition as a valuable tool to investigate gas sensing interactions. In this work, surface plasmon resonance studies in angular modulation have been used to characterise response in the presence of NO2 toxic gas of thin TiO 2 porous films containing different types of metal-phthalocyanines. The hybrid thin films were prepared using sol-gel technique. Low temperature annealing of the films (80 °C) ensured the formation of microporous TiO2 backbone and the preservation of phthalocyanine. Optical parameters of the active layers in dry air were calculated by using the SPR measurements and information about their variation in the presence of different concentrations of toxic gas was obtained. © 2002 Elsevier Science B.V. All rights reserved.

Copper(II) phthalocyanine derivatives with four alkoxycarbonyl chains as substituents were synthesized. Langmuir-Blodgett (LB) films of the two following compounds were deposited: Cu(II) [tetrakis(3,3-dimethyl-1-butoxycarbonyl)] phthalocyanine and Cu(II) [tetrakis( n -butoxycarbonyl)] phthalocyanine. Moreover, alternate LB films of the two compounds and LB films from a 1:1 mixture of them were prepared. Monolayers were spread onto the water surface from different solutions and were transferred onto quartz slides using the vertical lifting method. The deposition parameters and processes are described, and a UV-visible spectroscopic characterization of these compounds in different solvents and of the related LB films is presented. All isotherms and optical data are consistent with the molecules being stacked nearly edge-on to both the water surface and the substrate. Moreover, after deposition, the molecular faces exhibit a preferred orientation perpendicular to the dipping direction. Molecular order in the films was explored by polarized electronic absorption spectroscopy. Optical characterization of our LB films indicates the presence of some degree of molecular aggregation even in the multilayers. Finally, the results from a preliminary transmission electron microscopy study on the LB films are presented.

Langmuir–Blodgett (LB) films of Cu(II) [tetrakis-(3,3-dimethyl-1-butoxycarbonyl)] phthalocyanine have already been the subject of thorough study; in this case, the absorption spectrum in the UV–VIS spectral range and the optical constants of the as-deposited LB film were studied. Furthermore, in order to use these LB films as optical gas sensors, ellipsometric measurements carried out on our LB films in the presence of dry air and their interaction with toluene and tetrachloroethene are discussed. In particular, reference values for thickness and complex refractive index have been determined. Moreover, the variations of the relative thickness, the normalised refractive index and extinction coefficient at a fixed wavelength, when these films are exposed to different concentrations of toluene and tetrachloroethene, are presented.

Copper (II) phthalocyanine derivatives with four alkyl chains were synthesized. Langmuir-Blodgett (LB) films of the following two compounds were deposited: Cu(II)[tetrakis(3,3-dimethyl-butoxycarbonyl)] phthalocyanine and Cu(II)[tetrakis(n-butoxycarbonyl)] phthalocyanine. Moreover, LB films from a 1:1 mixture of the two compounds were prepared. All isotherms and optical data were consistent with the molecules being stacked nearly edge-on to the substrate, with the molecular faces having a preferred orientation perpendicular to the dipping direction. The dynamic response characteristics of the electrical conductance of the LB films to different NO2 concentrations in dry air are described. A relationship has been observed between the anisotropic molecular orientation and the electrical conductivity parallel to the substrate.

In the last two decades there has been considerable interest in the study of optical and electrical properties of metal-substituted phthalocyanines with the goal of their possible applications in technology. In particular, these compounds have been proposed as new materials for gas sensors [1–3]. The deposition of these macrocycles by the Langmuir-Blodgett thin films is a method with significant potential [4].

Novel Cu(II) [tetrakis-(3,3-dimethyl-l-butoxycarbonyl)]phthalocyanine (CuPcBC) thin films have been prepared by the Langmuir-Blodgett (LB) technique from ethyl acetate and toluene solutions. Polarized light UV-Vis measurements show in-plane anisotropy of the orientation of molecules in the LB films. Dynamic response characteristics of the electrical conductance to different NO 2 concentrations in dry air are presented. The sensitivity as a function of temperature has been analysed; in particular, the CuPcBC LB film have shown a good sensitivity to NO 2 gas at an operating temperature of about 170 °C.

Attenuated total reflection Fourier transform infrared (ATR-FTIR) difference spectroscopy has been employed as a powerful method for the comprehension of active layer– analyte interactions, revealing interesting mechanistic aspects concerning the binding of halogen-substituted phenols onto phthalocyanine Langmuir–Schaefer films.