Colorimetric/fluorometric optical chemosensors based on oxazolidine for highly selective detection of Fe3+ and Ag+ in aqueous media: Development of ionochromic security papers

Abstract

Photodetection of metal ions in different environments is a noteworthy research. Some sensitive oxazolidine derivatives were synthesized and their responsivities toward different metal ions were investigated. The OX1 and OX2 derivatives were synthesized from 2,3,3-trimethylindolenin and 1,1,2-trimethylbenz[e]indole, respectively. In addition, two hydroxyl and naphthalene functionalities were applied to both of the OX1 and OX2 derivatives to obtain OX1-OH and OX2-OH and also OX1-Naph and OX2-Naph derivatives, respectively. Investigation of ionochromic properties of oxazolidine derivatives showed their potential applications as highly-selective and sensitive optical chemosensors for detection of metal ions. The results showed colorimetric and fluorometric photodetection of Fe3+ ions in aqueous solution, where OX2-NaPh displayed selective photodetection of Ag+ in addition to Fe3+. For the development of paper-based colorimetric/fluorometric metal ion chemosensors and also high-security anticounterfeiting technology, ionochromic cellulosic papers based on oxazolidine derivatives were prepared via layer-by-layer coating strategy, which showed fluorescence emission in different colors with impregnation in aqueous solution of Fe3+ or Ag+. In addition, the Fe3+ and Ag+ aqueous solutions were used as anticounterfeiting ink for handwriting and printing on the ionochromic papers with pink, cyan blue, and dark blue fluorescence emissions of the written or printed marks. Therefore, the prepared ionochromic cellulosic papers have potential applications as colorimetric/fluorometric metal ion chemosensors and also in anticounterfeiting technology based on ionochromic security papers.