UV-detecting dual-responsive strips based on dicyanoacetate-containing hexaphenylbutadiene with aggregation-induced emission characteristic

Abstract

An ultraviolet (UV) radiation is a double-edged sword. The right amount can kill bacteria on the skin and promote the metabolism of calcium and phosphorus, which further stimulate the hematopoietic and immune functions. However, an excessive UV radiation will burn the skin and can even cause skin cancer. Therefore, a method based on naked-eye judgment should be developed to detect the intensity of UV radiation. Herein, the aggregation-induced emission (AIE) characteristics of two hexaphenyl-1,3-butadiene-based isomers containing dicyanoacetate, ZZ-HPB-NC and EE-HPB-NC were elucidated by single-crystal structure analysis. As the ZZ-HPB-NC, with a looser packing structure, is more suitable for intramolecular photocyclization, the ZZ-HPB–NC–based strips were sensitive to UV radiation. This is because the crystallization of ZZ-HPB-NC can be easily induced on the paper fibers, followed by intramolecular cyclization under UV radiation. As the illumination time increases, the color of the strips changes from yellow to green under a hand-held UV lamp. This approach makes it easy to estimate the intensity of the UV radiation by the naked eyes. The dual-responsive sensitivity is in direct proportion to the intensity of the UV radiation. The detection limit of the ZZ-HPB–NC–based strips at 254 nm UV intensity was estimated to be 8.2 μW/cm2. Thus, the ZZ-HPB–NC–based strips can be used as a simple and inexpensive technique to detect the intensity of the UV lamps in hospitals, nursery schools, and public areas, avoiding the harmful effects of the UV lamps to human eyes and skins.