UV‐Activated Luminescence/Colourimetric O₂ Indicator

Abstract

An oxygen indicator is described, comprising nanoparticles of titania dispersed in hydroxyethyl cellulose (HEC) polymer film containing a sacrificial electron donor, glycerol, and the redox indicator, indigo-tetrasulfonate (ITS). The indicator is blue- coloured in the absence of UV light, however upon exposure to UV light it not only loses its colour but also luminesces, unless and until it is exposed to oxygen, whereupon its original colour is restored. The initial photobleaching spectral (absorbance and luminescence) response characteristics in air and in vacuum are described and discussed in terms of a simple reaction scheme involving UV activation of the titania photocatalyst particles, which are used to reduce the redox dye, ITS, to itsleucoform, whilst simultaneously oxidising the glycerol to glyceraldehye. The response characteristics of the activated, that is, UV photobleached, form of the indicator to oxygen are also reported and the possible uses of such an indicator to measure ambientO2levels are discussed.

Optical studies of the solution phase reduction and stabilization of indigo tetrasulfonate in polyelectrolyte complexes

“…The absorbance band in Fig. 2 a at 590 nm is the absorbance of the oxidized ITS and agrees with the literature [ 5 , 41 ]. Fig.…”

“…Developing chemistries that can stabilize molecules in redox states that are not normally stable under atmospheric conditions has significant application for the indicator chemistry field [ 1 , 2 , 3 ]. Molecules whose color change can be controlled by redox or acid/base chemistry are particularly useful for packaging applications in the food and biomedical industries [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 ]. While many indicators are engineered to change color rapidly, there are applications for stabilization of the redox active species for long periods of time so that the color change is more gradual [ 1 , 2 ].…”

Nanotechnologies for Improving Food Quality, Safety, and Security

“…For example, researchers at the University of Strathclyde have produced a hydroxyethyl cellulose polymer fi lm oxygen sensor, containing titanium dioxide nanoparticles and the blue dye, indigo -tetrasulfonate. Following incorporation in the packaging, the sensor is exposed to UV light, the dye is photo -bleached (a reaction catalyzed by the titanium dioxide) and remains so until exposed to atmospheric oxygen levels, when it rapidly (within three minutes) returns to a deep blue color (even in the dark) [73] .…”

Thermoelectric Energy Harvesting for Oxygen Determination in Refrigerated Intelligent Packaging

“…In all of these techniques, the use of oxygen indicators and sensors becomes a necessity. Many examples have been reported for both oxygen indicators [15]- [17] and sensors [18]- [20], being very adequate those based on luminescent oxygen sensitive elements [21]- [23] because they are inexpensive, nontoxic, tuneable and they exhibit a long ambient shelf-life [13].…”