Synthesis of Modified Bromothymol Blue Having Long Alkyl Substituents for Application to Textile-based Chromogenic Basic-gas Sensors

A textile-based chromogenic sensor was fabricated to react against small amount of gas phase alkaline chemicals. A modified bromothymol blue (mBTB) having two linear pentyl substituents on the chromophore was synthesized to give good affinity and wash fastness on nylon substrates as well as recognizable color change by exposure to gas phase basic chemicals such as ammonia and alkylamines. The color change properties of the mBTB were examined in solution and on nylon fabrics at various alkaline conditions. The nylon fabric dyed with mBTB exhibited very sensitive and rapid reaction showing color change over 50 from orange to dark khaki even at 10 ppm of ammonia in a couple of minutes. The textile sensor appeared to be reused more than 20 repeat cycles. The textile sensor was tested for fastness to washing, rubbing and light. The wash fastness of mBTB was significantly improved compared to the conventional bromothymol blue.