A colorimetric sensor array for odour visualization

Array-based vapour-sensing devices are used to detect and differentiate bet ween chemically diverse analytes. These systems- based on cross-responsive sensor elements-aim to mimic the mammalian olfactory system(1-3) by produci ng composite responses unique to each odorant. Previous work has concentrat ed on a variety of non-specific chemical interactions(4-11) to detect non-c oordinating organic vapours. But the most odiferous, toxic compounds often bind readily to metal ions. Here we report a simple optical chemical sensin g method that utilizes the colour change induced in an array of metalloporp hyrin dyes upon ligand binding while minimizing the need for extensive sign al transduction hardware. The chemoselective response of a library of immob ilized vapour-sensing metalloporphyrin dyes permits the visual identificati on of a wide range of ligating (alcohols, amines, ethers, phosphines, phosp hites, thioethers and thiols) and even weakly ligating (arenes, halocarbons and ketones) vapours. Water geometrical correlation length), and consequen tly a purely diffusive large-scale behaviour for the force. Therefore, we c onclude that our results are certainly applicable to disordered packings su ch as cohesionless soils or sand piles. In contrast, for the particular cas e of non-random, textured packings, biased and long-range correlated q-seri es along the force transmission tree are likely to be encountered, thus alt ering the previous purely diffusive behaviour.