Triple-Band and Ultra-Broadband Switchable Terahertz Meta-Material Absorbers Based on the Hybrid Structures of Vanadium Dioxide and Metallic Patterned Resonators.

A bifunctional terahertz meta-material absorber with three layers is designed. The surface of the bifunctional meta-material absorber is a periodically patterned array composed of hybrid structures of vanadium dioxide (VO2) and metallic resonators; the middle layer is a nondestructive TOPAS film, and the bottom layer is a continuous metallic plane. Utilizing the phase-transition property of VO2, the responses of the meta-material absorber could be dynamically switched between triple-band absorption and ultra-broadband absorption. When VO2 is in the metallic state, an ultra-broadband absorption covering the bandwidth of 6.62 THz is achieved over the range from 4.71 THz to 11.33 THz. When VO2 is in the di-electric state, three absorption peaks resonated at 10.57 THz, 12.68 THz, and 13.91 THz. The physical mechanisms of the bifunctional meta-material absorber were explored by analyzing their near-field distributions. The effects of varying structural parameters on triple-band and ultra-broadband absorption were investigated. It is revealed that by optimizing the structure parameters, the number of absorption peaks could be increased for a certain sacrifice of absorption bandwidth. FDTD Solutions and CST Microwave Studio were used to simulate the data of the absorber, and similar results were obtained.

Impact of Inoculating with Indigenous Bacillus marcorestinctum YC-1 on Quality and Microbial Communities of Yibin Yacai (Fermented Mustard) during the Fermentation Process.

Bacillus species play an important role in improving the quality of some fermented foods and are also one of the dominant bacteria in Yibin Yacai (fermented mustard). However, little is known about their effects on the quality of Yibin Yacai. Here, the effect of Bacillus marcorestinctum YC-1 on the quality and microbial communities of Yibin Yacai during the fermentation process was investigated. Results indicated that the inoculation of Bacillus marcorestinctum YC-1 promoted the growth of Weissella spp. and Lactobacillus spp. and inhibited the growth of pathogens, accelerating the synthesis of free amino acids and organic acids and the degradation of nitrite. Furthermore, inoculating Yibin Yacai with YC-1 could effectively enhance the synthesis of alcohols and terpenoids in yeasts, thus producing more linalool, terpinen-4-ol, and α-muurolen in Yibin Yacai, and endowing it with pleasant floral, fruity, woody, and spicy aromas. These findings reveal that the inoculation of B. marcorestinctum YC-1 can improve the quality and safety of Yibin Yacai by changing microbial communities as fermentation proceeds.

Light-driven self-healing polyurethane based on PDA@Ag nanoparticles with improved mechanical and antibacterial properties.

To endow the polyurethane (PU) coating with antimicrobial and self-healing ability, a PU composite film (PUDA@Ag) based on furfuryl functional polydopamine nanoparticles (FPDA NPs) and Diels-Alder (DA) reaction was prepared successfully. Herein, FPDA NPs were added to maleimide-terminated PU by DA reaction as cross-linking agents and photothermal fillers. Owing to the excellent photothermal effect of PDA NPs and the existence of DA bonds, the PUDA@Ag film had superior self-healing performance (90%). Importantly, with the existence of FPDA@Ag, the PU composite films showed comprehensive mechanical properties (tensile strength up to 50 MPa, toughness of 153.9 MJ m-3, and elongation at break of 895%). Silver nanoparticles (AgNPs) as antibacterial agents and nanofillers endowed the PUDA@Ag with excellent antibacterial and long-term antibacterial properties against Gram-negative E. coli and Gram-positive S. aureus. This work provides a reasonable method to prepare multi-responsive self-healing PU composite films with super-high strength and antimicrobial properties that have great potential in the fields of biomedicine, coating, and thermal management.