Gas sensing properties of porphyrin assemblies prepared using ultra-fast LB deposition

The interaction between the gas sensing and surface morphology properties of LB thin films of porphyrins in terms of the adsorption kinetics

“…The solid phase which is suitable for the thin film fabrication is found to be between 10 and 20 mN m À1 for all chemicals. The area per molecule values of the monolayers are determined by extrapolation of the linear part of the isotherm curve which corresponds to the solid phase and the values were found to be approximately 50, 43, 115 and 15 Å 2 for the porphyrins porp1eporp4 respectively which is compatible with the previous results [15,17].…”

Optical anisotropy and gas sensing properties of ordered porphyrin films

“…By following the modification with time, it is evident that the signal variation did not reach its saturation, which avoided the long lasting pollution of the sample we have otherwise observed, with possible damage of the layer. The full recovery of the original signal level, after exposure to a flow of high purity N 2 gas, on the contrary happens after few tens of seconds [5].…”

“…In our experiment, we have used the higher sensitivity of the outer layers to gas or vapours to disentangle their contribution ("the surface") from the rest of the film ("the bulk"), which is most probably less affected by adsorption [5]. By considering the two different curves measured at λ − (Fig.…”

“…Experimental research has shown that porphyrins offer a fascinating opportunity, since they couple a very high reactivity to the possibility of tuning their gas sensing properties by simple modifications of their structure: this can be obtained by choosing suitably the metal at the centre of the ring and/or the peripheral substituents [4]. It has been also reported that the sensitivity to gas would be higher for highly disordered layers [5]: Langmuir-Blodgett (LB) films prepared at very high deposition rates (fast LB) yield an unconventional, high sensitivity to NO 2 probably due to the enhanced surface area of the resulting porous assembly. This fact has motivated the preferential choice of a coarse deposition method, and techniques as spray aereosol are normally used as they connect ease of use …”

Solvent induced aggregation of protoporphyrin and octacarboxylphthalocyanine of zinc deposited on gold surface

“…These interactions involved in solution play a crucial role in the nanostructuration of the film that will determine its physical properties. Depending on the applications, it could be better to obtain either a two-dimensionally organized molecular film over a wide surface, for instance when a high electronic transport is required in the surface plane [25,26], or a grainy film taking advantage of the increased specific surface as in the case of molecular sensors [27]. Therefore, in this study we were mainly concerned by the way the solvent composition could determine the final structure of deposited molecular films of specific conjugated macrocycles.…”