A physical insight into the gas-sensing properties of copper (II) tetra-(tert-butyl)-5,10,15,20-tetraazaporphyrin Langmuir–Blodgett films

Abstract The Langmuir isotherm of copper (II) tetra-( tert -butyl)-5,10,15,20-tetraazaporphyrin [CuPaz( t -Bu) 4 ] has been investigated at the air–water interface. The Langmuir monolayer displays two phase regions, which have a phase transition at 7 mN/m. Langmuir–Blodgett (LB) films have been fabricated onto glass slides, interdigitated electrodes and quartz crystal microbalance electrodes, and characterized by UV-VIS spectroscopy, electrical and nanogravimetric measurements, respectively. The CuPaz( t -Bu) 4 LB films were used to quantity some of the volatile gases, i.e. vapors of hexane, benzene and toluene. UV-VIS spectroscopic measurements reveal that there is an interaction between CuPaz( t -Bu) 4 molecules and the above organic solvent molecules, which is manifested by a red shift and broadening of Soret and Q bands. The response and recovery behaviors, sensitivity and selectivity of the LB films to different organic vapors have been investigated by means of nanogravimetric measurements. Such results offer a potential application of such a porphyrin derivative for the detection of aromatic compounds, even at room temperature.