A colorimetric sensor array for odour visualization

Array-based vapour-sensing devices are used to detect and differentiate between chemically diverse analytes. These systems- based on cross-responsive sensor elements-aim to mimic the mammalian olfactory system(1-3) by producing composite responses unique to each odorant. Previous work has concentrated on a variety of non-specific chemical interactions(4-11) to detect non-coordinating organic vapours. But the most odiferous, toxic compounds often bind readily to metal ions. Here we report a simple optical chemical sensing method that utilizes the colour change induced in an array of metalloporphyrin dyes upon ligand binding while minimizing the need for extensive signal transduction hardware. The chemoselective response of a library of immobilized vapour-sensing metalloporphyrin dyes permits the visual identification of a wide range of ligating (alcohols, amines, ethers, phosphines, phosphites, thioethers and thiols) and even weakly ligating (arenes, halocarbons and ketones) vapours. Water geometrical correlation length), and consequently a purely diffusive large-scale behaviour for the force. Therefore, we conclude that our results are certainly applicable to disordered packings such as cohesionless soils or sand piles. In contrast, for the particular case of non-random, textured packings, biased and long-range correlated q-series along the force transmission tree are likely to be encountered, thus altering the previous purely diffusive behaviour.