One-Step Preparation of Lanthanide-Doped Polyurea Multicolor Microspheres for Versatile Fluorescent Applications

Lanthanide-doped polyurea microspheres (LTP@PUMs) are prepared through a facile one-step precipitation polymerization, without stabilizer under quiescent condition. The process features simple operation, mild condition and low LTP doping. The size of the microspheres and their fluorescence color are precisely adjustable by tuning experiment conditions. LTP@PUMs are of great interests in several aspects, including multicolor fluorescence, high quantum yield (75.3%), remarkable stability, redispersibility and biocompatibility, owing to good compatibility of LTP with PU, strong hydrogen-bonding and coordination interactions. These excellent properties allow LTP@PUMs to achieve versatile applications. Taking LTP@PUMs as fluorescent sensor, selective detection for 4-nitrophenol is shown with high sensitivity (detection limit: 0.076 µM) and good reusability. In latent fingerprint imaging, high-quality and durable fluorescence images on various substrates are easily obtained. Strong fluorescence is also retained after heating to 260°C, making LTP@PUMs a high-thermal-resistant multicolor filler for 3D printing, an interesting property rarely reported. In vivo, LTP@PUMs are demonstrated to accumulate selectively in spleen (71.0%, 2.87 µm) and lungs (90.1%, 10.12 µm), enabling high-contrast imaging without obvious abnormal behaviors observed after eight months. This work offers, therefore a new strategy for the fabrication of multifunctional fluorescent microspheres, with promising prospects in environmental monitoring, public security, advanced manufacturing, and biomedicine.