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

Abstract

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.

Ionically Self-Assembled Monolayer pH Sensitive Films-Fabrication and their Long Term Response to Varying Temperature Conditions

“…As shown in Fig. 6, after 48 hours in the refrigerator the change in the absorbance was minimal, similar to previously reported results [10]. For films left in the fridge at 3.24 °C for 38 days the difference is more noticeable, especially for thicker films (slide N) with 10 bilayers of (PAH/BY), which show 10.64% increase in absorbance.…”

“…In this study we use the optical method to detect changes in absorbance in PAH/BY films due to temperature changes and over long periods of times. We showed previously [10] that these films remain stable with no significant changes in topography and absorbance when exposed to a range of temperatures from below freezing up to 46 °C over a period of time up to 24 hours. We present results of absorbance studies over longer term (128 days) exposure to various temperatures, ranging from subfreezing (-9.02 °C), to low temperature and up to high temperature 100 °C.…”