Comparing zinc and manganese porphyrin LB films as amine vapour sensing materials

Both 5,10,15,20-tetrakis[3,4-bis(2-ethylhexyloxy)phenyl]-porphinato manganese (III) (MnEHO) and 5,10,15,20-tetrakis[3,4-bis(2-ethylhexyloxy)phenyl]-porphinato zinc (II) (ZnEHO) solid-state films have been prepared using the LB technique. Calix[8]arene has been mixed with the ZnEHO and MnEHO to enhance the quality of the porphyrin films, their response to amine gases and also increase film lifetime. UV–vis spectroscopy has been used to study the response of these films to amine vapour. Both ZnEHO and MnEHO show spectral changes under exposure to each of the primary, secondary and tertiary amine gases. Interestingly, the ZnEHO displays a spectral red-shift, with largest spectral changes occurring at 421 nm, whereas the MnEHO displays a blue-shift, with largest optical changes occurring at 467 nm. ZnEHO shows a significantly larger optical spectrum change once amine vapours are introduced to the samples compared with the MnEHO; therefore, ZnEHO is more suitable for amine sensing in a sensing device.