The detection of oxygen using optical sensors is of increasing interest, especially in modified atmosphere food packaging (MAP), in which the package, usually containing food, is flushed with a gas, such as carbon dioxide or nitrogen. This tutorial review examines the ideal properties of an oxygen optical sensor for MAP and compares them with those developed to date, including the most recent advances. The basic technologies underpinning the different indicator types are described, examples given and their potential for application in MAP assessed. This tutorial review should be of interest to the MAP industry and researchers in optical sensors and oxygen sensing.

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Oxygen indicators and intelligent inks for packaging food

Spectroscopic and photochemical properties of d10 metal complexes

Review on synthesis and properties of high-energy-density liquid fuels: Hydrocarbons, nanofluids and energetic ionic liquids

Photo-CIDNP of biopolymers

— The triplet state characteristics (spectrum, lifetime and quantum yield) for four dye sensi tisers [methylene blue (MB), erythrosin (ER), haematoporphyrin (HP) and riboflavin (RF)] were determined in methanol by laser flash photolysis and singlet oxygen yields (0.60 to 0.48) from time-resolved measurements of the 1270 nm near infrared emission. The reaction of singlet oxygen with four long chain unsaturated phenyl esters [oleate (18: 1), linoleate (18: 2), linolenate (18: 3) and arachidonate (20: 4)] was followed quantitatively using the singlet oxygen luminescence technique and also, after continuous420–700 nm irradiation, by HPLC and other analysis of the isomeric product monohydroperoxides. The overall quantum yield of photooxidation (∼10-2) was shown to be consistent with the observed singlet oxygen quenching constants(2–12 times 104 dm3 mol-1 s-1) for the four esters studied and the singlet oxygen lifetime in methanol (τ∼ 9 μs). The isomer product distribution was interpreted in terms of a dual singlet oxygen and radical mechanism, the radical contribution increasing with sensitiser in the order ER = MB < HP ≪ RF, but also showing some dependence on substrate unsaturation. Evidence is presented for singlet oxygen quenching by MB and RF (kO= 1.6 and 6.0 times 107 dm3 mol-1 s-1) and for the accelerated photobleaching of the dye sensitisers in the presence of the unsaturated esters.

Singlet oxygen yields and radical contributions in the dye‐sensitised photo‐oxidation in methanol of esters of polyunsaturated fatty acids (oleic, linoleic, linolenic and arachidonic)

Etude des equilibres en solution dans le benzene des complexes d'arylphosphine de type L m Cu n X n . L'halogene ne semble avoir qu'un effet mineur sur la dissociation

Solution equilibria of tertiary phosphine complexes of copper(I) halides

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Riboflavin was irradiated anaerobically in aqueous EDTA solutions over the pH range 2.5–10. In other dye systems (Bonneau and Pereyre, 1975), only the trivalent anion of EDTA was found to have significant reactivity for photoreduction. For riboflavin, the reactivity begins with monoanionic EDTA, and the reactivity is markedly increased as the charge increases. This suggests that the charge on the reductant is more important to the electron transfer process for riboflavin than the formation of a nonhydrogen bonded nitrogen site on EDTA. At high concentrations of EDTA in the pH range 4–8, quenching of the photoreduction occurs, which can be explained by an energy transfer between the excited singlet state of riboflavin and trianionic EDTA, possibly as an association complex. The rate constants for the photoreduction of riboflavin by the monovalent, divalent, and trivalent anions of EDTA are 1.0 times 107M-1 s-l, 4.8 times 10′M-1 s-l, and 2.0 times 108M-1s-1, respectively. The rate constant for the singlet state quenching by trianionic EDTA is 3 times 109M-l s-1, and the limiting quantum yield for intersystem crossing for riboflavin in aqueous solution is 0.50 ± 0.05.

The reduction and quenching of photoexcited flavins by edta

Photosensitized isomerization of norbornadiene to quadricyclane with (arylphosphine)copper(I) halides

Etude, a partir de spectres d'absorption et d'emission, des perturbations sur les transitions electroniques de phosphines aromatiques, provoquees par une liaison de ces coordinats au metal de cuivre(I); les resultats revelent un effet prononce sur la transition de l'etat excite le plus bas (1→a Π ) des coordinats

Dennis J. Fife

Papers

Solution equilibria of tertiary phosphine complexes of copper(I) halides

The reduction and quenching of photoexcited flavins by edta

Photosensitized isomerization of norbornadiene to quadricyclane with (arylphosphine)copper(I) halides

Electronic excited states of arylphosphine complexes of copper(I) halides

Thermal isomerization of quadricyclane to norbornadiene catalyzed by copper(II) and tin(II) salts