Intrinsic Narrowband Blue Phosphorescent Materials and Their Applications in 3D Printed Self‐monitoring Microfluidic Chips

Abstract Organic room‐temperature phosphorescent (RTP) materials, especially with narrowband emission properties, exhibit great potential for applications in display and sensing, but have been seldom reported. Herein, a rare example of the intrinsic narrowband blue RTP material is fabricated and reported. A series of indolo[3,2,1‐kl]phenothiazine derivatives, named Cphpz, 1O‐Cphpz, and 2O‐Cphpz, are designed and synthesized. Due to their relatively rigid structures, these three compounds showed deep blue narrowband emissions ranging from 396 to 434 nm with the full width at half maximum (FWHM) of 31, 26, and 31 nm, respectively. To the delight, compound 2O‐Cphpz displayed intrinsic narrowband blue RTP at 448 nm with FWHM of 36 nm and a long‐lived lifetime of 1.08 s in hydroxyethyl acrylate and acrylic acid matrix. Photophysical studies, single crystal analyses, and TD‐DFT calculations are performed to elucidate further the relationships between molecular structures and the narrowband blue RTP properties. Meanwhile, because the narrowband blue RTP is highly sensitive to humidity, a visualizing droplet path optical microfluidic chip is efficiently fabricated through the digital light processing 3D printing.This work provides a rare example and a reliable strategy to realize narrowband blue RTP and further expand their applications in self‐monitoring 3D printed structures.