Facile approaches to build ordered amphiphilic tris(phthalocyaninato) europium triple-decker complex thin films and their comparative performances in ozone sensing

Solution processed thin films of an amphiphilic tris(phthalocyaninato) rare earth triple-decker complex, Eu-2[Pc(15C5)(4)](2)[Pc(OC10H21)(8)], have been prepared from three different methods: self-assembly (SA) annealed in solvent vapor, quasi-Langmuir-Shafer (QLS) and drop casting methods. In particular, we successfully developed a simple QLS process for fabricating ordered multilayers with a good thickness control. The films prepared from three different methods were characterized by a wide range of methods including electronic absorption spectra, IR, X-ray diffraction, atomic force microscopy (AFM), and current-voltage (I-V) measurements. J-type aggregates have been formed with the increasing degree of order of molecular stacking Cast < QLS < SA films. Moreover, the gas sensing behavior of the three types of films was investigated towards ozone in the 8-300 ppb range. Unexpectedly good sensitive, stable and reproducible responses to O-3 gas are obtained for these kinds of ultra-thin solution processed films in a fast response/recovery cycle of only 1/4 min. The response of Eu-2[Pc(15C5)(4)](2)[Pc(OC10H21)(8)] films is linearly correlated to the ozone concentration. The interaction between the Eu-2[Pc(15C5)(4)](2)[Pc(OC10H21)(8)] films and different ozone concentrations was found to follow first-order kinetics. Strikingly, QLS films showed the most stable response and the largest average sensor response rate constant among the three types of films.