This thesis explores novel DV -activated, oxygen-sensitive systems. Thus, photochemical versions of the thermal blue-bottle experiment are used to illustrate the kinetics of PET reactions in homogeneous and heterogeneous photochemistry; the former via the visible light photobleaching of a MB/TEOA solution, and fast recovery in air, and the latter via the DV photobleaching of MB in a Ti02/glucose aqueous dispersion, with slow recovery, but which can be catalysed by Pt. A novel, acetone-based, water-proof Ti02/MB/glycerol/SPS colorimetric oxygen indicating film that coats on hydrophobic polymers is prepared, and is readily photobl~ached but recovers slowly. The rate of photobleaching is dependent upon DV A irradiance, [glycerol], [Ti02] and [MB]. The kinetics of the dark recovery were dependent upon T, %02, and RH. Ethanol replaced acetone, and a Pt catalyst was introduced - i.e. a Pt-Ti02/MB/glycerol/SPS colorimetric oxygen indicator, printable by flexo printing, resulted. The indicator is readily photobleached and recovery times reduced, with linear dependence upon %Pt loading. The recovery kinetics are zero order with respect to [LMB](, moderately dependent upon temperature, and sensitive to relative humidity. Pigment particles (MB and DL-threitol coated onto Ti02) are prepared and extruded in LDPE, to create a water-proof, solvent-based O2 smart plastic film. The blue-coloured indicator is readily photobleached and recovers in ~2.5 days. The rate of photobleaching is dependent upon the irradiance of UV A light. The rate of recovery is dependent upon %02, relative humidity and temperature. A Ti02 colloid is prepared for use with MB in a colorimetric oxygen indicating ink. This ink is suitable for printing onto polyester film by a DOD PU printer. The blue-coloured indicator is readily photobleached and recovers in - 12 hours in ambient air. The rate of recovery is linearly dependent upon the %02, moderately dependent upon relative humidity at 21 "C, and reduced upon reducing temperature.