Primary Ammonium Terephthalate Salts with High Moisture Resistance and Their Use in the Detection of OH Radicals.

Abstract

A novel and practical method is proposed for the detection of gaseous OH radicals using a moisture-resistant organic salt composed of terephthalic acid (TPA) and n-alkylamine. When the alkyl chain length was greater than 8, the organic salt had a crystal structure in which the alkyl chains were arranged parallel to each other and zero-dimensional voids were adjacent to terephthalate (TA). Since the parallelly arranged alkyl chains acted as a hydrophobic block, the organic salts had excellent humidity durability. The highly hydrophobic bis(n-octylammonium) terephthalate (nOA-TA) powder was exposed to gaseous OH radicals generated by a low-pressure mercury lamp and a fluorescence response suggesting the formation of bis(n-octylammonium) hydroxyterephthalate (nOA-HTA) was observed. The presence of the zero-dimensional voids in the nOA-TA crystal caused the formation of nOA-HTA. In addition, a sheet was prepared in which nOA-TA crystals were uniformly immobilized in the pores of a membrane filter, and the spatial distribution of OH radicals was evaluated.