Heteroatom/Heterocycle-Substituted Ketone Dyes as Efficient Photoinitiators in Visible Light-Emitting Diode/Near Infrared Light Photopolymerization with Enhanced Two-Photon Lithography Capability

Photopolymerization is a burgeoning technology with a wide range of applications from coatings and inks to nanotechnology. The development of photosensitized systems that can work at long wavelengths with safety and environmental friendliness, such as visible light-emitting diodes and near infrared light, is essential. In this study, a series of ketone dyes containing heteroatom/heterocyclic substituents were designed on the basis of the carbazole–coumarin backbone to compare with aryl ring-substituted ones. The photophysical and photochemical properties of the dyes were studied by UV–vis spectroscopy, time-dependent density functional theory calculations, fluorescence spectroscopy, and steady-state photolysis. The potential application of dyes in one/two-photon polymerization was investigated. Results showed that the introduction of heterocycles/heteroatoms has a considerable influence on the absorption and polymerization properties of dyes. CCK–Th, which contains a thiophene substitute, exhibits the most excellent light absorption properties as well as the fastest reaction efficiency with amine additives. Notably, when comparing the two-photon lithography capability, the photoresist containing 0.1 wt % CCK–Th, which can achieve a writing speed of 46 mm s–1, exhibits high two-photon sensitivity, about two times that of the benzene ring-substituted CCK–Ben. In addition, CCK–Th shows outstanding ability to construct complex three-dimensional patterns. These modified CCKs show great application potential in nanotechnology, additive manufacturing, and optoelectronics and provide design concepts for the development of photoinitiators.