The reason for this behaviour such information is that NO2 gradually transforms the intrinsic semiconductor LnPc2 newsletter subscribe into the oxidised form LnPc2+, causing a decrease of the conductivity after a long exposure [11].The intensity and kinetics of the response to a particular gas are Inhibitors,Modulators,Libraries therefore related Inhibitors,Modulators,Libraries to the nature of the phthalocyanine Inhibitors,Modulators,Libraries compound Inhibitors,Modulators,Libraries used as the sensitive material. In addition, the charge transport process and the possibility of measuring a macroscopic conductance depend on the relative orientation and separation of adjacent molecules. The variation in conductivity is in fact controlled by the nature of the surface adsorption sites which is influenced by both the structure and morphology of the films and the latter varies considerably, depending on the method of deposition used.

This is particularly evident in Langmuir�CBlodgett films in which the suppression of crystallinity has the effect of enhancing the matrix permeability and improving the sensor performance Inhibitors,Modulators,Libraries [16].Whit regards to the sublimated films, phthalocyanines crystallise as a variety of polymorphs, and the two main phases are identified as �� and ��. They are both characterised by a herringbone Inhibitors,Modulators,Libraries structure with the molecules stacked along the b-axis, but the polymorphs are differentiated by the angle between the plane of the molecule and the stacking axis. Sublimated films of transition Inhibitors,Modulators,Libraries metal phthalocyanines may have amorphous or �� or �� crystalline nature depending on sublimation conditions.

Annealing of a sublimated crystalline film transforms the form AV-951 to the �� form and changes its electrical conduction and gas response characteristics [17].

Inhibitors,Modulators,Libraries This indicates that for sublimated films morphology also plays a fundamental role in the electrical response to gas exposure. Indeed, the morphology must accommodate both the charge transfer interaction and charge carrier transport. It is commonly accepted that the charge transfer interaction is easier if the face of a phthalocyanine ring rather than an Cilengitide edge is available, i.e. if the molecules are arranged face-on instead of edge-on with respect to the surface of substrates. On the other hand, charge carrier transport is facilitated by a long-range stacking of co-facially oriented phthalocyanine rings.

Amorphous films http://www.selleckchem.com/products/chir-99021-ct99021-hcl.html are prepared by vacuum sublimation (10?6 Torr) onto liquid-nitrogen-cooled (100K) substrates [18]. These films are stable at room temperature but crystallise to an phase on annealing over the temperature range 60�C140 ��C followed by an to �� phase transition at more elevated temperature depending on the central metal [19]. The structure of sublimated films is selleck chem Tofacitinib important since, as we have already mentioned, it determines how gases may enter the lattice and interact with the phthalocyanine units.