Blue fluorescent waterborne polyurethane‐based transition metal complexes with antibacterial activity

Abstract

Efficient and stable blue fluorescent materials are the key components of light‐emitting devices and have received wide attention. Herein, transition metal complexes Zn(5‐AQ)2, Cu(5‐AQ)2, and Cd(5‐AQ)2 are prepared by using 5‐aminoquinoline (5‐AQ) as ligand and Zn2+, Cu2+, and Cd2+ as the central ions, respectively. Then, waterborne polyurethane (WPU)‐based transition metal complexes Zn(5‐AQ)2‐WPU, Cu(5‐AQ)2‐WPU, and Cd(5‐AQ)2‐WPU with different emission wavelengths of blue fluorescence are prepared by bonding Zn(5‐AQ)2, Cu(5‐AQ)2, and Cd(5‐AQ)2 to polyurethane chains as chain extenders, respectively. Noteworthily, with the increase of transition metal ion radius (Zn2+ < Cu2+ < Cd2+), the fluorescence emission wavelengths of the complexes showed different degrees of blue‐shift, and the blue‐shifted wavelengths showed a decreasing trend. Importantly, their fluorescence colors are blue‐shifted from blue‐green to blue with different emission wavelengths after accessing the polyurethane backbone, which has potential applications in the field of tuning white LED materials. The thermal decomposition temperatures of Zn(5‐AQ)2‐WPU, Cu(5‐AQ)2‐WPU, and Cd(5‐AQ)2‐WPU are above 220°C with good thermal stability, and their fluorescence lifetimes are prolonged by 8.817, 8.896, and 6.489 ns, respectively, compared with the complexes. Furthermore, WPU transition metal complexes with water as a dispersive medium have an antibacterial efficiency of up to 100% against Escherichia coli, which is an environmentally friendly antibacterial material with broad application prospects.