Effects of NiO, SnO2, and Ni-doped SnO2 semiconductor metal oxides on the oxygen sensing capacity of H2TPP.

Improving the performance of optical oxygen sensors can be accomplished by adding metal oxide semiconductors (MOSs) additives to the composition comprising an oxygen-sensing agent immobilized in a polymeric thin film. For several decades, MOSs have attracted great interest in gas sensors due to their high sensitivity to many target gasses. Herein, meso-tetraphenylporphyrin (H2TPP) dye was immobilized into the poly(1-trimethylsilyl-1-propyne) (poly(TMSP)) silicone rubber in the presence of NiO, SnO2, Ni:SnO2 metal oxide particles as additives, and their thin films were prepared to investigate oxygen-sensitive optical chemical sensor properties. The characterizations of the synthesized metal oxide powders were carried out through XPS, XRD, FT-IR, PL spectroscopy and SEM methods. Intensity-based spectra and decay kinetics of H2TPP-based thin films were investigated for the concentration range of 0%-100% [O2]. The oxygen sensitivity (I0/I100) of the porphyrin was calculated as 70%. Whereas the relative signal intensity values of H2TPP-based sensor slides were measured as 75%, 80%, and 88% in the presence of NiO, SnO2, Ni:SnO2 additives, respectively. The H2TPP in combination with Ni:SnO2 semiconductor provided a higher I0/I100 value, larger response range, higher Stern-Volmer constant (KSV) value, and faster response time compared to the undoped form, and also NiO and SnO2 additive-doped forms of H2TPP. The response and the recovery times of the porphyrin-based sensing slide along with Ni:SnO2 additives have been measured as 12 and 50 s. These results make the H2TPP along with the MOSs promising candidates as oxygen probes.