Synthesis of an Acid-gas Sensing Fluorescence Dye Showing Change of Both Color and Fluorescence Emission Spectrum inside
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ISSN 1229-9197 (print version) ISSN 1875-0052 (electronic version)
Synthesis of an Acid-gas Sensing Fluorescence Dye Showing Change of Both Color and Fluorescence Emission Spectrum inside Polyethylenic Fiber on Exposure to Gas Phase Strong Acid for Application to Washable Textile Sensors Junheon Lee and Taekyeong Kim* Department of Textile System Engineering, College of Engineering, Kyungpook National University, Daegu 41566, Korea (Received October 11, 2019; Revised January 14, 2020; Accepted February 16, 2020) Abstract: A halochromic fluorescence dye was synthesized to fabricate acid-gas sensing textiles. The dye has a maximum absorption at 436 nm and stokes shift of 54 nm in ethanol, which means that it exhibits a typical fluorescence color of greenish yellow. The dye was designed to have good substantivity toward hydrophobic and chemical resistant polyethylenic fibers, such as high molecular weight polyethylene (HMWPE) fibers, by introducing di-butyl and t-butyl groups on coumarin and benzoxazole moieties of the chromophore, respectively. The fluorescence dye showed the change of both color and fluorescence emission properties not only in a solution by addition of hydrochloric acid but also inside the HMWPE fiber on exposure to gas phase hydrogen chloride even at relatively low concentrations. From the repeat test, the sensing performance was maintained reversibly even after 20 repeat cycles of adsorption and desorption of gas phase hydrogen chloride. The HMWPE fabrics dyed with the fluorescence dye can be washable by showing fastness of rating 4-5 to washing. Keywords: Acid gas, Chemosensor, Halochromic, Fluorescence, Polyethylene
However, in that case, there is a risk that the sensitivity of dyes against external stimuli would be decreased or even disappear because the contact of stimulants to the dyes inside the substrate will be delayed or even blocked as well as the structural deformation of chemosensing dyes by stimulation would be restricted sterically inside the substrates. The pH paper or strips used in laboratories may come to mind, and they surely show rapid color change on exposure to acids or bases of gas phase. However, unfortunately, the pH indicating dyes are merely absorbed on paper or paperlike substrates so that they could be leached out of the substrates in aqueous or non-aqueous media. In addition, the durability of paper substrate itself is very weak so that they can be used only as a disposable type. The objective of this study is to fabricate a textile acid-gas sensor with very high sensitivity and rapid response speed, and moreover, practical level of durability against operating environment such as washing, rubbing, and contamination, etc. A pH indicating fluorescence dye was synthesized first and then penetrated into a hydrophobic and chemicalresistant polyethylenic fiber using a dyeing process normally used in textile fields, and it could make a washable acid-gas sensing textile. We have reported several issues in the previous studies [11,12]. The first issue was that many existing
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