Response of Optically Transparent pH Sensing Films to Temperature and Temperature Variations

• Main Authors: Daniela M. Topasna, Gregory A. Topasna
• Format: Article
• Language: English
• Published: MDPI AG 2019-12-01
• Series: Coatings
• Subjects: thin films; optical ph sensors; ionic self-assembled monolayer; layer-by-layer assembly; dyes
• Online Access: https://www.mdpi.com/2079-6412/10/1/18

There are numerous applications for thin films based chemical pH sensors, in such areas as biomedical, military, environmental, food, and consumer products. pH sensitive films fabricated through the ionic self-assembled monolayers technique were made of polyelectrolyte polyallylamine hydrochloride and the water-soluble organic dye molecule Direct Yellow 4. The films were monitored in various environmental conditions and for selected periods, at temperatures varying between −13.7 and 46.2 °C. Absorbance measurements and atomic force microscopy performed before and after thermal treatment indicate that for optimized thickness and composition the films maintain their functionality and are not affected by long-term exposure at these temperatures.