Xiang Zheng Kong

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.

Raspberry-like microspheres have been widely used as superhydrophobic materials, photonic crystals, drug carriers, etc. Nevertheless, their preparation methods, usually consisting of multiple steps, are generally time- and energy-consuming. Herein raspberry-like SiO₂@polyurea microspheres (SiO₂@PUM) are readily prepared via a one-step precipitation polymerization of isophorone diisocyanate in a H₂O/acetone mixture with the presence of SiO₂ particles. The sphere size, surface roughness, and SiO₂ content of SiO₂@PUM are easily adjustable by varying the experimental conditions. TEM and SEM observations reveal that the final SiO₂@PUM exhibits a core-shell structure, with polyurea (PU) in the core and SiO₂ particles as the shell. In the process, the SiO₂ particles were initially located on the PUM surface as a monolayer. With the reaction proceeding, the monolayer of SiO₂ particles became thicker, forming a thicker layer of SiO₂ particles on PUM due to the accumulation of SiO₂ particles, leading to a multilayer structure of SiO₂ particles on the shell of SiO₂@PUM. The formation mechanism of the raspberry-like SiO₂@PUM was thoroughly discussed and ascribed to electrostatic attraction between the positively charged PU and negatively charged SiO₂ particles. Once dried, SiO₂@PUM was superhydrophobic and turned hydrophilic if water-wetted. Using a layer of SiO₂@PUM, effective separation with good reusability for a variety of oil-water mixtures was achieved regardless of the oil density and types of oil-water emulsions. This work presents a novel protocol for the preparation of raspberry-like microspheres with tunable wettability via a rapid and green process, and the resulting microspheres are highly effective for the separation of diverse types of oil-water mixtures.

Tetracyclines are well-known antibiotics and widely used against a variety of bacterial infections. Their monitoring and detection have been an important issue. To this end, a vast number of methods have been developed; fluorescence sensing is one of the most reported. However, most of the reported sensors are made from transition metals with sophisticated multiprocesses; polymers are hardly seen for this purpose, particularly biocompatible ones. Herein, an aqueous solution of poly(ethylene glycol) (PEG), well known for being biocompatible, is shown to emit under excitation of 280 nm, while the solutions of selected tetracyclines, namely, doxycycline (DOX) and tetracycline (TC), are non-emissive under the same conditions. In the binary solutions of PEG-DOX or PEG-TC, PEG emission is sharply quenched with high sensitivity and selectivity. PEG was then used as a sensor for DOX and TC detections in water with high performance compared to reported studies. The same tests were also done by DOX spiking in milk and tap water, demonstrating that DOX was practically fully recovered. The quenching mechanism was ascribed to the interaction between the O atoms of PEG in clusters and specific heteroatom groups on tetracycline molecules through hydrogen bonding, elucidated from FTIR and NMR analyses. Therefore, this work provides a novel, fully green, easy to operate, low cost, and reliable protocol for tetracycline monitoring and detection and opens new potential application for PEG.