Sensitization metal-phthalocyanine

Photoelectrochemical behavior of metal phthalocyanine solid films (p-type photoconductors) have been studied at both metal (93,94,95,96) and semiconductor (97,98) electrodes. Copper phthalocyanine vacuum-deposited on a Sn02 OTE (97) displayed photocurrents with signs depending on the thickness of film as well as the electrode potential. Besides anodic photocurrents due to normal dye sensitization phenomenon on an n-type semiconductor, enhanced cathodic photocurrents were observed with thicker films due to a bulk effect (p-type photoconductivity) of the dye layer. Meier et al. (9j>) studied the cathodic photocurrent behavior of various metal phthalocyanines on platinum electrodes where the dye layer acted as a typical p-type organic semiconductor. 

The chemistry of these systems is identical to that already described for 02 and H2 production in homogeneous systems except that MV+ or [Ru(bipy)3]3+ generated during the photochemistry of the bulk solution then regenerate MV2+ or [Ru(bipy)3]2+ by donation or acceptance of an electron at the electrode. Photopotentials of —1.0 V and currents of —1 mA can be generated for long periods in this way. Similar photoelectrical cells using metal phthalocyanine or porphyrin sensitizers have also been developed.359-362... 

Yu JC, Xie Y, Tang HY, Zhang L, Chan HC, Zhao J. Visible light-assisted bactericidal effect of metal phthalocyanine-sensitized titanium dioxide films. J Photochem Photobiol A Chem 2003 156 235 11. 

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. 

The zerovalent dipotassium phthalocyanine cuprate(0) may be prepared by the reduction of the cupric complex with potassium in liquid ammonia. It was not possible to isolate a copper(I) derivative (870). Like other low oxidation state metal phthalocyanines, this complex is air- and water-sensitive. 

Another important NOj sensors using metal phthalocyanines are SAW gas sensors. SAW devices are attractive for gas sensor applications because of their high sensitivity and reliability, so that NO sensors using SAW devices with metal phthalocyanines have been extensively studied by many researchers. Nieuwenhuizen et al. of Prins Maurits Laboratory TNO, Netherlands, have actively studied on the SAW gas sensors and as an example of the researches they reported the response of SAW gas sensors for NOj, in which different metal phthalocyanines were deposited on one delay-line of a dual delay-line oscillator[16]. Fig. 7 indicates the response of the sensors as a fimction of NOj concentration at 150°C. The response is defined as frequency differences divided by the thickness of a phthalocyanine layer. As shown in the Figure. Co phthalocyanine is most sensitive to NOj, followed by Cu phthalocyanine and... 

Topics which have formed the subjects of reviews this year include excited state chemistry within zeolites, photoredox reactions in organic synthesis, selectivity control in one-electron reduction, the photochemistry of fullerenes, photochemical P-450 oxygenation of cyclohexene with water sensitized by dihydroxy-coordinated (tetraphenylporphyrinato)antimony(V) hexafluorophosphate, bio-mimetic radical polycyclisations of isoprenoid polyalkenes initiated by photo-induced electron transfer, photoinduced electron transfer involving C o/CjoJ comparisons between the photoinduced electron transfer reactions of 50 and aromatic carbonyl compounds, recent advances in the chemistry of pyrrolidino-fullerenes, ° photoinduced electron transfer in donor-linked fullerenes," supra-molecular model systems,and within dendrimer architecture,photoinduced electron transfer reactions of homoquinones, amines, and azo compounds, photoinduced reactions of five-membered monoheterocyclic compounds of the indigo group, photochemical and polymerisation reactions in solid Qo, photo- and redox-active [2]rotaxanes and [2]catenanes, ° reactions of sulfides and sulfenic acid derivatives with 02( Ag), photoprocesses of sulfoxides and related compounds, semiconductor photocatalysts,chemical fixation and photoreduction of carbon dioxide by metal phthalocyanines, and multiporphyrins as photosynthetic models. 

Various types of solid-state NO2 sensors have been proposed based on semiconducting metal oxides (including heterocontact materials) [42-50,58,59,234-238], solid electrolytes [1,239,240], metal phthalocyanine [241], and SAW devices [242]. Among these NO2 sensors, the semiconducting metal oxides and solid electrolytes appear to be the best. Specifically, semiconducting metal oxide gas sensors are most attractive because they are compact, sensitive, of low cost, and have low-power consumption. Their basic mechanism is that the NO2 gas is adsorbed on the surface of the material this decreases the free electron density into the space-charge layer and results in a resistance increase [243]. 

A. J. (1980) Semiconductor electrodes 30. Spectral sensitization of the semiconductors titanium oxide (n-Ti02) and tungsten oxide (n-W03) with metal phthalocyanines. J. Am. Chem. Soc., 102, 5137-5142. 

Organic materials such as the metal phthalocyanines have been developed to give an extremely sensitive response to nitrogen dioxide (3) with only a minor interference from halogens, but even these materials operate at around 200 C and at present they show little promise of being developed for the detection of other toxic gases. 

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