Ultra-fast pH determination with a new colorimetric pH-sensing hydrogel for biomedical and environmental applications

In this study that demonstrates many firsts in the literature, the acrylate derivative (BTBm) of bromothymol blue, retaining its indicator feature, was synthesized as a monomer via using an organic indicator bromothymol blue (BTB). After the structural characterization of BTBm synthesized by ourselves for the first time, copolymeric hydrogel systems were formed with three different commercial monomers in cationic (3-Acrylamidopropyl-trimethylammonium chloride / APTMACl), anionic (3-Sulfopropyl acrylate potassium salt / SPA) and neutral (acrylamide / AA) structures. Structural characterization of BTBm-based hydrogels, which was successfully synthesized by using a 0.5% methylene bisacrylamide (MBA) crosslinker, was elucidated by FT-IR spectroscopy. The morphological structures and elemental compositions of the hydrogels were examined by SEM and EDX elemental mapping analyses. The color changes of BTBm-based hydrogels, which are intended to be used as colorimetric pH sensors, were examined in different pH environments both with naked-eye and by using a UV–Vis spectrophotometer. It has been observed that APTMACl-BTBm hydrogel can be a more beneficial colorimetric pH sensor material than other BTBm-based hydrogels in terms of its ability to respond to pH changes in a wide color range, short response time, and mechanical strength performance. • pH sensor BTBm monomer was synthesized using an organic indicator bromothymol blue. • Anionic, cationic and neutral copolymeric hydrogels based on BTBm were synthesized. • The performances of the obtained hydrogels as pH sensors were compared. • APTMACl-BTBm hydrogel had wide pH range sensitivity and fast response ability. • APTMACl-BTBm hydrogel is an excellent candidate for pH sensitive smart wound dressing.