Lead phthalocyanine

Lead(II) phthalocyanine can be prepared by heating lead(II) oxide with the respective phthalonitrile without solvent150-159 or in 1-chloronaphthatene.154 Addition of anhydrous lead(II) acetate to a solution of dilithium phthalocyanine in anhydrous alcohol gives a precipitate of lead phthalocyanine.59 Lead phthalocyanine can also be obtained by electrosynthesis.160... 

In the following example, the low stability of lead phthalocyanines is used to prepare a metal-free 4,5-tetrabridged phthalocyanine 4 as the decomposition product. 

The palladium phthalocyanine (67), developed by Mitsui Toatsu and Ciba58,59 is one of the leading phthalocyanine infrared absorbers for CD-R (Compact Disk-Rewritable) (see Chapter 9.13). Bulky groups (R) reduce undesirable molecular aggregation, which lowers the extinction coefficient and hence the absorptivity and reflectivity. Partial bromination allows fine tuning of the film absorbance and improves reflectivity. The palladium atom influences the position of the absorption band, the photostability and the efficiency of the radiationless transition from the excited state.58 It is marketed by Ciba as Supergreen.60... 

Silver(II) phthalocyanine has been obtained by the action of silver nitrate on dilithium phthalocyanine in absolute alcohol at room temperature, or by the action of silver sulfate upon lead phthalocyanine in boiling 1-chloronaphthalene.496,561 ESR studies confirmed the presence of the paramagnetic d9 Ag ion, and for a frozen solution in 1-chloronaphthalene showed well-resolved nitrogen hyperfine lines. In the undiluted solid at room temperature, only a broad resonance was observed at g < 2.016. This may have been caused by aggregation.562... 

For the TOF SIMS analysis, only slides treated with a natural pH HAPS solution were used. These were subsequently extracted with warm and hot water. They were mounted into a grid sample holder for transportation into a VG IX23S time-of-flight (TOF) SIMS instrument operating at a vacuum of < 10 Torr with a microfocused liquid Ga metal ion primary beam source (30 keVx 1.0 nA). For charge compensation, an electron flood gun was used. The working resolution of the spectrometer was determined from a lead phthalocyanine spectrum for Pb+ at mlz = 208 and the molecular ion at mlz = 720, it was 500 and 1000, respectively. 

Phthalocyanines were chosen for these experiments because they are electronic semiconductors and because they are quite stable materials — an important consideration in fabricating any practical gas-detecting device. A considerable body of literature exists describing the physical and chemical properties of the phthalocyanines. A review of the work prior to 1965 is contained in the chapter by A. B. P. Lever in Volume 7 of Advances in Inorganic Chemistry and Radiochemistry (2). Electrical properties of phthalocyanines have been receiving increased attention in recent years. The photoconductivity of metal-free phthalocyanine has been studied in detail (3,4). Electrical properties of lead phthalocyanine have been studied extensively, especially by Japanese workers (5, ,7,8i). They have also studied the alteration of the conductivity of this material upon exposure to oxygen ( ,10.). The effects of a series of adsorbed gases (0, , CO, and NO) on the conductivity of iron phthalo-... 

Figure 73 Representation of antiferroelectric structure proposed for a lead phthalocyanine.

Organic semiconductors (OS), such as pentacene, lead phthalocyanine etc. have attracted considerable attention as the components of barrier heterojunctions with other organic or inorganic semiconductors (IS) for transistor, sensor or photovoltaic application. Therefore, dependence of the electronic and recombination properties of the heterostructure interface on the technological conditions of the interface formation is of great importance [1-6]. 

Both anisotype and isotype junctions, based on n-GaAs, were fabricated with pentacene (Pn) and lead phthalocyanine (PbPc) as organic semiconductor of p-type, and methyl perylene pigment (MPP) as OS of n-type. 

Lead phthalocyanine, obtained from the exothermic reaction between litharge and phthalonitrile (10, 195), is readily demetallated by concentrated acids and is not very stable in organic solvents. It forms pure green... 

By far the most detailed thermodynamic studies have been made by Berezin, who has looked at the equilibria existing in concentrated sulfuric acid. Linstead s group were the first to observe that some of the metal phthalocyanines were demetallated in concentrated sulfuric acid, whereas others appeared indefinitely stable (10). It was shown that all phthalocyanines which resisted attack were of metals whose radii were of the right size to fit nicely into the space available at the center of the ligand. Berezin has since put these observations on a more quantitative basis (19, 21, 26). Labile complexes (i.e., those which are demetallated instantly or fairly rapidly in concentrated sulfuric acid) include those of the alkali metals, alkaline earth metals, Be, Mg, Cd, Hg, Sb(III), Pb, Sn(II), Mn(II), and Fe(III). Stable complexes (demetallated very slowly in acid) include those of Zn, Al, Cl2Sn(IV), OV(IV), Co(II), Rh(II), Os(IV), Ni(II), Pd(II), Pt(II), and Cu(II). The actual rates of decomposition vary widely thus, while calcium and magnesium phthalocyanines are demetallated very rapidly, silver and lead phthalocyanines react fairly slowly (19). The rates of decomposition in 1 M sulfuric acid increase in the sequence (19) Fe(III)... 

The most commonly reported organic semiconductor material is phthalocyanine (Pc), although many embodiments of this material are technically classified as polymers and will not be discussed in this chapter. One sensor of this type is a p-type semiconductor sensitive to CI2 and NO2 at a 150 °C operating temperature, and has the advantage of very low sensitivity to H2, H2S, NH3, CH4, SO2, and CO [20]. Mg, Co, Ni, Cu, or Zn phthalocyanine films have also demonstrated some sensitivity to NO2 [28]. In another study, lead phthalocyanine (PbPc) was configured as an n-type semiconductor when doped with RUO2 and Pd and was shown to be sensitive to H2 and CO gases [21]. 

Nichogi K, Waragai K, Taomoto A, Saito Y and Asakawa S 1989 Lead phthalocyanine Langmuir-Blodgett films Thin Solid Films 178 297-301... 

Sadaoka Y., Jones T. A., and Gopel W., Effect of heat treatment on the electrical conductance of lead phthalocyanine films for NO2 gas detection, J. Mater. Sci. Lett., 8, 1095-1097, 1989. 

Lead phthalocyanine tetracarboxylic acid was used to sense humidity and alcohol vapors [63]. Remarkable improvement in the selectivity with respect to ethyl alcohol and reduction in the sensitivity for humidity was observed when the surface was treated with electron cyclotron resonance plasma. The response and recovery time were 50 and 30 seconds, respectively. The increased cross-linking of PbPc is responsible for the creation of new functional groups that have imparted the sensing of alcohol vapor through extrinsic doping. 

Table I summarizes the application of the NRL sensor for the detection of four toxic vapors (Column 1), various selective reagent coatings (Column 2), the lowest vapor concentration detected (Column 3), and the probable reaction mechanism (Column 4). The types of vapors besides ammonia. Include an organophosphonate, and two sulfur compounds. The reagent coatings Included a variety of dyes, (i.e., oxazlne, lead-phthalocyanine (Pb-Pc), lead tetraphenylprophrin, (Pb-...

Jakubik W, Urbanczyk M, Opilski A (2001) Sensor properties of lead phthalocyanine in a surface acoustic wave system. Ultrasonics 39(3) 227-232... 

Lead phthalocyanine (PbPc) Resistive NO, Redox Bott and Jones (1984) Sadaoka et al. (1990a, b) Liu et al. (1996)... 

Liu CJ, Hsieh JC, Ju YH (1996) Response characteristics of lead phthalocyanine gas sensor effect of operating temperature and deposition annealing. J Vac Sci Technol A 14 753-756 Liu CJ, Peng CH, Ju YH, Hsieh JC (1998) Titanyl phthalocyanine gas sensor for NO detection. Sens Actuators B... 

Wang B, Zhou X, Wu Y, Chen Z (2012) Lead phthalocyanine modified carbon nanotubes with enhanced NH3 sensing performance. Sens Actuators B 171 398-405... 

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