4.8 Article

Hydrochromic xanthylium cations with tuneable colour and high moisture-sensitivity for potential smart packaging

Journal

MATERIALS TODAY CHEMISTRY
Volume 33, Issue -, Pages -

Publisher

ELSEVIER SCI LTD
DOI: 10.1016/j.mtchem.2023.101692

Keywords

Hydrochromic; Moisture sensing; Humidity monitoring; Optical sensor; Smart packaging

Ask authors/readers for more resources

Hydrochromic materials can undergo color changes in response to water and moisture, which can be modulated by controlling the composition and structure of the cations. This study proposes a hydrochromic mechanism involving xanthylium cations and demonstrates the potential application of this system in smart packaging.
Hydrochromic materials exhibit a colour change in response to water and moisture. Intensely coloured xanthylium cations, generated by acidifying xanthene-9-ol precursors with trifluoroacetic acid (TFA), are found to exhibit dramatic decolourization with high moisture-sensitivity. Mechanistic study confirms that the hydro-chromic mechanism of xanthylium cations involves the nucleophilic addition of water molecules at the carbocation centre at 9-position of xanthylium, thus regenerating xanthene-9-ol. This accounts for the high reversibility with up to 50 acid-activation/moisture-deactivation cycles. Furthermore, functionalizing the cations with different aliphatic and aromatic groups (electron rich, electron poor and extended pi-conjugated moieties) at the 9-and 2,7-positions, enables the tuning of colour and moisture sensitivity of this hydrochromic system, by controlling the cations' frontier molecular orbital energies and optical bandgap, as well as their chemical stability and nucleophilicity. To demonstrate the potential of the hydrochromic system for humidity sensing in smart packaging, optical paper probes and polymer films pre-doped with xanthene-9-ol precursors were pre -pared. Upon activation with TFA fume, they reveal different colour and decolourization rate in response to atmospheric moisture, ranging from minutes to hours, demonstrating feasibility for smart packaging and other potential applications.

Authors

I am an author on this paper
Click your name to claim this paper and add it to your profile.

Reviews

Primary Rating

4.8
Not enough ratings

Secondary Ratings

Novelty
-
Significance
-
Scientific rigor
-
Rate this paper

Recommended

No Data Available
No Data Available