Durable fluorescent cotton textile by immobilization of unique tetrahydrothienoisoquinoline derivatives

Due to the sensitivity for interchanging color by exposure to UV light, designing of fluorescent textiles is highly demanded to be employed in camping, military and sensing purposes. Aromatic compounds containing tetrahydroisoquinoline are known with their biological and medicinal activity, but they are not applied as fluorescent materials. Therefore, the present study focuses on synthesis of tetrahydrothienoisoquinoline derivatives and their application in textile technology to obtain fluorescent cotton fabrics. Four tetrahydrothienoisoquinoline derivatives were synthesized in three steps, starting from 2,4-diacetyl-5-hydroxy-5-methyl-3-(4-methoxyphenyl)cyclohexanone. The chemical structures of the synthesized tetrahydrothienoisoquinoline derivatives (Ar1-Ph, Ar2-Ph-Cl, Ar3-Ph-CH3 and Ar4-Ph-OCH3) were confirmed by infrared spectra, (HNMR)-H-1 and (CNMR)-C-13. The yields and melting points were both measured for all the synthesized compounds. The tetrahydrothienoisoquinoline derivatives were applied onto the cotton fabrics to obtain Ar1-Ph@cotton, Ar2-Ph-Cl@cotton, Ar3-Ph-CH3@cotton and Ar4-Ph-OCH3@cotton fabrics. All modified cotton fabrics were exhibited by green emission under UV lamp (325 nm). The excited modified cotton fabrics showed an intense fluorescence emission peak at 444-467 nm, related to the implemented compounds. The intensity of the fluorescence peak followed the order of Ar1-Ph@cotton > Ar3-Ph-CH3@cotton >= Ar4-Ph-OCH3@cotton >> Ar2-Ph-Cl@cotton. The estimated quantum yield (QY) were 68.79%, 23.15%, 13.83% and 13.38%, for Ar1-Ph, Ar2-Ph-Cl, Ar3-Ph-CH3 and Ar4-Ph-OCH3, respectively. Due to the water insoluble character of tetrahydrothienoisoquinoline derivatives, the modified fabrics showed quite good durability, as the the quantum yields were marginally diminished by only 10.1 - 12.3%, after 5 washings. The prepared tetrahydrothienoisoquinoline derivatives succeeded for obtaining durable fluorescent textiles, and could be further applied in advanced purposes including technical textiles, sensors/biosensors, smart labeling and anti-counterfeiting purposes. Graphic abstract

Automated summary

This study successfully synthesized four tetrahydrothienoisoquinoline derivatives and applied them to cotton fabrics to obtain fluorescent textiles exhibiting green emissions under UV light. The derivatives showed intense fluorescence emission peaks at 444-467 nm and good water resistance.