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Soluble phthalocyanines, including organo-soluble tetrakis(2,9,16,23-tert-butylphthalocyanines) (M(TBPc), M = H₂, Cu, Mg; M(TBPc)₂, M = Tb, Dy) as well as the water-soluble sodium salt of sulfonated phthalocyanines ((MPc(SO₃Na)₄), M = Cu, Zn, Mg), and perylene tetracarboxylic derivatives (N,N'-bis(1,5-dimethylhexyl)-3,4: 9,10-perylenebis(dicarboximide)) have been prepared by microwave irradiation. Their photoelectric performances have also been investigated. Among lab-made cells, the SnO₂glass / MgPc(SO₃Na)₄ / PDHEP / Al photoelectric cell exhibits the best photoelectricity conversion effect with a short-circuit photocurrent (116.0 μA/cm²) under illumination of white light 1.201 mW/cm².

The nonlinear optical (NLO) properties of lanthanide bisphthalocyanine (Lu(TBPc)Pc), including first hyperpolarizability, second hyperpolarizability and reverse saturable absorption (RSA), have been investigated. Furthermore, Lu(TBPc)Pc has also been applied for optical switch based on its RSA performance.

The group of the University of Valladolid is a multidisciplinary team formed by chemists, physicists and engineers. The activities of the group are focused to the study of the physicochemical properties of nanostructured Langmuir-Blodgett thin films based on phthalocyanines and their applications. Films of a variety of phthalocyanine molecules including several metallophthalocyanines, lanthanide double decker phthalocyanines and heteroleptic derivatives have been prepared. Their spectroelectrochemical properties have been described in detail and compared with those observed in disordered casted films or microcrystalline evaporated films. The group has dedicated special attention to films based on rare earth double decker compounds due to their unique semiconducting, optical and electrochemical properties. A rich electrochromism has been demonstrated in thin films of this family of compounds. The reversibility is improved in nanostructured Langmuir-Blodgett films. This has permitted development of an electrochromic display that can change its color from blue to green and finally to red. At the present moment, our main objective is the design of sensors able to detect gases and liquids. It has been demonstrated that thin film assemblies based on rare earth bisphthalocyanines modify their conductivity and their optical properties in the presence of electron donor or electron acceptors gases. Changes are also observed when the devices are exposed to Volatile Organic Compounds such as esters, alcohols or aldehydes which are responsible of odors in foods and beverages. Liquid sensors have also been developed. Their working principle is based in the fact that the rich electrochemical properties of phthalocyanine thin films are extremely sensitive to the nature of the electrolytic solution. Arrays of phthalocyanines have been used to construct an electronic nose able to discriminate odors from a variety of foods and beverages. Similarly, phthalocyanines have also been used to construct an electronic tongue based on voltammetric sensors. This is one of the main contributions of the group to the field of sensors.

The unique semiconducting, optical and electrochemical properties of radical lanthanide bisphthalocyanines make them ideal materials for sensing applications. A variety of chemical sensors have been developed using rare-earth bisphthalocyanine thin films. In this paper, the characteristics of sensors based on bisphthalocyanines are reviewed. The advantages of these sensors with respect to sensors developed using other metallophthalocyanines are discussed. Resistive sensors based on bisphthalocyanines change their conductivity when exposed to a variety of pollutant gases and volatile organic compounds. Because bisphthalocyanines are intrinsic semiconductors, the conductivity of their thin films is higher than the conductivity of metallophthalocyanine thin films. This facilitates the electrical measurements and enhances the sensitivity of the sensors. Optical sensors have also been developed based on the rich optical properties shown by bisphthalocyanines. Films characterized by a bright green color change to red or to blue upon oxidation or reduction. The changes also affect the charge-transfer band associated to the free radical that bisphthalocyanines show in the near infrared region. This band coincides with telecommunication wavelengths, making possible the fabrication of fiber optic sensors where a phthalocyanine film is deposited at one of the ends of the fiber. Electrochemical sensors have been developed taking advantage of the unique electrochemical behavior associated to the one-electron oxidation and one-electron reduction of the phthalocyanine ring. These reversible processes are extremely sensitive to the nature of the electrolytic solution. This has made possible the development of voltammetric sensors able to produce particular signals when immersed in different liquids. In the last part of the paper, the fundamentals and performance characteristics of electronic noses and electronic tongues based on bisphthalocyanines are described. Such devices have been successfully exploited in quality control, classification, freshness evaluation and authenticity assessment of a variety of food, mainly wines and olive oils.

A method has been developed to obtain good quality Langmuir-Blodgett (LB) films of mixtures of lutetium bisphthalocyanine and carbon nanotubes. The π-A isotherms exhibit high monolayer stability and the compressed monolayers are easily transferred to solid substrates by Y-type deposition. The electronic absorption spectra of the composite LB films show the characteristic bands of both compounds; the bands appear broader and shifted to higher wavelengths than those observed in solutions or in disordered films prepared by the casting method. The films are sensitive to oxidant or reducing vapors, whose presence cause 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 lutetium bisphthalocyanine and carbon nanotubes. LB film electrodes immersed in KCl and KClO₄ solutions show electroactivity associated to the oxidation and reduction of the phthalocyanine ring. Important changes in the UV-vis-NIR spectra registered in situ simultaneously to the application of the electrical potential have been observed. The electrochromism observed opens the possibility of using such thin films in electrochromic devices. Composite films show characteristic electrochemical responses when exposed to solutions of antioxidants, where a certain degree of electrocatalytic effect is observed. The enhanced degree of selectivity can be used in the development of voltammetric sensors.

Voltammetric sensors based on phthalocyanines have been used to detect a variety of compounds. In this paper, the state of the art of sensors prepared using classical techniques will be revised. Then, new strategies to improve the performance of the sensors will be described using as example sensors chemically modified with lutetium bisphthalocyanine (LuPc${}_2)$ dedicated to the detection of phenols of interest in the food industry. Classical LuPc₂ carbon paste electrodes can detect phenols such as catechol, caffeic acid or pyrogallol with limits of detection in the range of 10${}^{-4}$–10${}^{-5}$ M. The performance can be improved by using nanostructured Langmuir–Blodgett (LB) or Layer by Layer (LbL) films. The enhanced surface to volume ratio produce an increase in the sensitivity of the sensors. Limits of detection of 10${}^{-5}$–10${}^{-7}$ M are attained, which are one order of magnitude lower than those obtained using conventional carbon paste electrodes. Moreover, these techniques can be used to co-immobilize two electrocatalytic materials in the same device. The limits of detection obtained in LB sensors combining LuPc₂/AuNPs or LuPc₂/CNT are further improved. Finally, the LB technique has been used to prepare biosensors where a phenol oxydase (such as tyrosinase or lacasse) is immobilized in a biomimetic environment that preserves the enzymatic activity. Moreover, LuPc₂ can be co-immobilized with the enzyme in a lipidic film formed by arachidic acid (AA). LuPc₂ can act as an electron mediator facilitating the electron transfer. These biomimetic sensors formed by LuPc₂/AA/enzyme show Limits of detection of 10${}^{-8}$ M and an enhanced selectivity.