NO2 sensing ability of a monolayer of cobalt(II) porphyrin molecules covalently assembled on a engineered silica substrate

The 5,10,15-tri-(p-dodecanoxyphenyl)-20-(p-hydroxyphenyl)- and 5,10,15,20-tetrakis-(p-dodecanoxyphenyl)-cobalt porphyrin complexes were synthesized, purified and characterized. Silica substrates were functionalized with a covalent 4-ClCH2C6H4SiCl3 monolayer. Additional covalent bonding of the 5,10,15-tri-(p-dodecanoxyphenyl)-20-(p-hydroxyphenyl)-cobalt porphyrin to the silylated substrates was further achieved. The monolayer surface chemical characterization was carried out by X-ray photoelectron measurements. Both the Co 2p and N 1s spectra are evident. The NO2 sensing capability of the present cobalt porphyrin systems, at ppm levels, has been demonstrated.