Degradable Selenium-Containing Polymers for Low Cytotoxic Antibacterial Materials.

Developing biodegradable cationic polymers with high antibacterial efficiency and low cytotoxicity is of great significance in biological applications. Selenium is an essential trace element for the human body, and selenium-containing compounds are promising in various health-related applications. To combine selenium with biodegradability, selenide-functionalized polycaprolactones (PCL) with different hydrophobic substituents were synthesized followed by selenoniumization. The optimal polyselenonium salt showed excellent antibacterial activity with an MBC of 2 µg mL-1 and an MIC of 1 µg mL-1 and exhibited good biocompatibility before and after degradation. In addition, the obtained selenium polymer can be well blended with commercial PCL by electrospinning, and films with good antibacterial activity were prepared. This work enriches the knowledge of selenium derivatives and lays a foundation for follow-up research on selenium cationic polymers in the antimicrobial field.

Extreme-Angle Silicon Infrared Optics Enabled by Streamlined Surfaces.

Infrared optical systems are indispensable in almost all domains of society, but their performances are often restricted by bulky size, small field of view, large thermal sensitivity, high fabrication cost, etc. Here, based on the concept of catenary optics, a novel isophase streamline optimization approach is leveraged to design silicon complementary metal-oxide-semiconductor (CMOS)-compatible metasurfaces with broadband, wide-angle, and high-efficiency performances, which breaks through the glass ceiling of traditional optical technologies. By using the truly local geometric phase, a maximum diffraction efficiency approaching 100% is obtained in ultrawide spectral and angular ranges. Somewhat surprising results are shown in that wide-angle diffraction-limited imaging and laser beam steering can be realized with a record field of view up to 178°. This methodology is scalable to the entire optical band and other materials, enabling unprecedented compact infrared systems for surveillance, unmanned vehicles, medical science, etc.