1. Introduction:
Trimethylamine (TMA) vapours are highly volatile and released due to microbial degradation i.e., from the decomposition of plants and animals and exposure of it to an extent of 10 ppm causes headache, eye irritation, nausea etc. Hence, detection of this offensive TMA vapours are of prime importance for human safety\cite{Li_2017}. Mixed catalysts oxides system possesses potential advantages in gas sensing owing to its higher rate of reaction leading to spontaneous redox reactions. Increased sensitivity, selectivity and stability in addition to higher surface reactivity can be enhanced by mixed semiconducting oxides which also increases the material’s electronic conductivity\cite{Faia_2016}. Transition functional materials are widely used as supporting oxide in addition to host sensing material to enhance the electronic sensitization which majorly contributes to chemi-resistive sensing\cite{Epifani_2013}. In that row, VTO catalyst system emerges as an active counterpart in chemi-resistive sensing application. Vanadium and titanium oxide combination is selected due to its similar ionic radii of 0.68 Ǻ helping in building ordered crystal structure, i.e.., the substitution between the Ti and V oxides can be easily done in the crystal lattice\cite{Khan_2013}.It also plays a vital role in modulating the band gap. Thermal and chemical stability being an important property for any sensing element, VTO system has been chosen among various mixed oxides, for its combined phase stability, i.e., TiO contributing towards chemical stability and VO towards higher thermal stability. TiO supplements the host oxide by triggering its intrinsic property providing sites for spill over in VO, thereby tuning the electrical property of the material\cite{Alessandri_2005}. In case of VTO system, the catalytic property plays an important combinational feature in inflating the sensitivity, stability and selectivity of the sensing element towards TMA vapours. VO itself a heterogeneous catalyst when combined with TiO can be used as a better identifier of volatile organic amine, TMA.
Till date, VTO system have been employed in various applications such as gas sensors\cite{Epifani_2013}, energy storage\cite{Fleischmann_2017}, heterogenous catalysts\cite{Shyue_2005}, electrochromic devices\cite{Lu_2013} and super capacitors\cite{Jampani_2015}. But there are no reports on the sensing of TMA vapours using VTO catalytic system.