Colorimetric UV sensors with tunable sensitivity from diacetylenes

• New diacetylene lipids containing amide and diamide groups were synthesized.
• Colorimetric UV sensing properties of the diacetylene lipids were evaluated.
• New method for justification of the color transition point was proposed.
• Tuning of the UV sensitivity of the diacetylene lipids was achieved.
• New evidence for dual mechanisms of the color transition were observed.

A series of diacetylene compounds containing β-alanine ethyl ester and di-β-alanine ethyl ester groups were synthesized and dip-coated on paper for colorimetric UV sensing study. The white-to-blue-to-red colorimetric responses of the sensor strips were recorded by a photo scanner. The color images are analyzed based on the RGB color system to determine the color transition points and sensitivity. Coarse and fine tuning of the UV sensitivity was achieved by varying the head group and aliphatic chain length of the diacetylene lipids. Comparison of the UV sensitivity trends with the thermochromic sensitivity trends revealed that not only the photo-induced thermochromism but also photo-induced mechanical strain of the polydiacetylene backbone contributed to the color transition upon the UV irradiation.