Degradable, antibacterial and ultrathin filtrating electrospinning membranes of Ag-MOFs/poly(l-lactide) for air pollution control and medical protection

High-efficiency respiratory protection and intelligent monitoring by nanopatterning of electroactive poly(lactic acid) nanofibers

The advent of multifunctional nanofibrous membranes (NFMs) has led to the development of next-generation air filters that are ready to intercept fine particulate matters (PMs) and monitor the respiratory diseases. However, it is still challenging to fabricate biodegradable NFMs featuring the desirable combination of high filtration efficiencies, low air resistance, and intelligent real-time monitoring. Herein, a hierarchical nanopatterning approach was proposed to functionalize the stereocomplexed poly(lactic acid) (PLA) (SC-PLA) nanofibers via the combined electrospinning of SC-PLA and electrospray of CNT@ZIF-8 nanohybrids. The nanopatterned SC-PLA (NSC-PLA) NFMs were characterized by largely increased surface activity and electroactivity, as evidenced by the nearly two-fold increase in surface potential (up to 7.3 kV) and substantial improvements in the dielectric properties. Furthermore, the NSC-PLA NFMs exhibited excellent tribo-output performance, yielding a voltage of as high as 13.5 V for NSC-PLA NFMs loaded 10 % nanohybrids (NSC-PLA10). In particular, the exceptionally high electroactivity and unique protrusion structure together contributed to promote the filtration efficiencies, while providing a low pressure drop (e.g., 96.1 % for PM2.5 and 88.3 % for PM0.3, only 67.6 Pa of NSC-PLA10, at 32 L/min). More importantly, NSC-PLA NFMs enabled real-time monitoring of physiological signals during different respiratory states, as evidenced by the output voltages of 17.2, 32.9 and 37.5 mV for normal breath, fast breath and cough recorded by NSC-PLA10. The proposed NSC-PLA NFMs show enormous potential in the fields of air filtration and real-time respiratory monitoring, thus providing ecofriendly solutions to personal health management.

Super protective effect, ultra-high juice absorption and long-term antibacterial of Ag-2MI@Chitosan biodegradable sponge for fruit preservation and transportation

Plastic foam packaging is often used for the transportation to avoid mechanical damage to the fruit, but it lacks antibacterial properties, water absorption and is non-degradable, leading to fruit decay and safety risks as well as serious environmental pollution. Herein, Ag-2-Methylimidazole@Chitosan (Ag-2MI@CS) was successfully synthesized by in situ synthesis at normal temperature and pressure, and improved the antibacterial performance of Ag-2MI@CS by using green solvent ethanol to adjust the solvent polarity. The results showed that the long-lasting inhibitory performance of Ag-2MI@CS was significantly improved, the long-lasting antibacterial time has been extended from 24 h to 96 h. Furthermore, Ag-2MI@CS can significantly protect fruits and reduce the damage of fruits, even when falling from a height of 60 cm or under extreme transportation conditions. Besides, Ag-2MI@CS had extremely high absorption rates of water and fruit juice, 1447.69 % and 1356.59 %, respectively, which was conducive to absorbing water generated by respiration and juice generated by damage during transportation, so as to avoid the growth of bacteria caused by water and fruit juice. Ag-2MI@CS can achieve fruit preservation in both indoor static and transportation dynamic conditions. This study offers novel insights into new biodegradable packaging material in fruit transportation.

Nanopatterning of beaded poly(lactic acid) nanofibers for highly electroactive, breathable, UV-shielding and antibacterial protective membranes

Despite great potential in fabrication of biodegradable protective membranes by electrospinning of poly(lactic acid) (PLA) nanofibers, it is still thwarted by smooth surfaces and poor electroactivity that challenge the promotion of electret properties and long-term air filtration performance. Here, a microwave-assisted synthetic method was used to customize dielectric TiO2 nanocrystals of ultrasmall and uniform dimensions (∼30 nm), which were homogeneously embedded at beaded PLA nanofibers (PLA@TiO2, diameter of around 280 nm) by the combined "electrospinning-electrospray" approach. With small amounts of TiO2 (2, 4 and 6 wt%), the nanopatterned PLA@TiO2 nanofibrous membranes (NFMs) were characterized by largely increased dielectric constants (nearly 1.9), surface potential (up to 1.63 kV) and triboelectric properties (output voltage of 12.2 V). Arising from the improved electroactivity and self-charging mechanisms, the nanopatterned PLA@TiO2 NFMs exhibited remarkable PM0.3 filtration properties (97.9 %, 254.6 Pa) even at the highest airflow rate of 85 L/min, surpassing those of pure PLA membranes (86.2 %, 483.7 Pa). This was moreover accompanied by inhibition rates of 100 % against both E. coli and S. aureus, as well as excellent UV-blocking properties (UPF as high as 3.8, TUVA of 50.9 % and TUVB of 20.1 %). The breathable and electroactive nanopatterned PLA NFMs permit promising applications in multifunctional protective membranes toward excellent UV shielding and high-efficiency removal of both PMs and pathogens.

Incorporating charged Ag@MOFs to boost the antibacterial and filtration properties of porous electrospinning polylactide films

Faced with the pollution caused by particulate matter (PM) in the air, the prevalence of infectious diseases, and the environmental burden by use of nondegradable polymers, the existing filter materials such as meltblown cloth of polypropylene cannot satisfactorily meet people's requirements. In this study, Ag nanoparticles were loaded onto ZIF-8 particles by impregnation reduction to prepare the positively charged Ag@ZIF-8. The porous fibrous membranes of Ag@ZIF-8 with polylactide (PLA) were manufactured by electrostatic spinning technology. Due to the inherently charged feature of Ag@ZIF-8 particles and the presence of pores on fibers, the prepared membranes showed a stable good filtration efficiency of over 97 % at different humidity (30-90%RH, relative humidity). Meanwhile, the presence of charge on Ag@ZIF-8 and the synergistic effects of Ag and ZIF-8 particles made the membranes exhibit good antibacterial effects. The width of the inhibition zone of 3 wt%Ag@ZIF-8/PLA membrane reached 1.33 mm for E. coli and 1.35 mm for S. aureus, respectively.

Metal-Organic Framework/Polyvinyl Alcohol Composite Films for Multiple Applications Prepared by Different Methods

The incorporation of different functional fillers has been widely used to improve the properties of polymeric materials. The polyhydroxy structure of PVA with excellent film-forming ability can be easily combined with organic/inorganic multifunctional compounds, and such an interesting combining phenomenon can create a variety of functional materials in the field of materials science. The composite membrane material obtained by combining MOF material with high porosity, specific surface area, and adjustable structure with PVA, a non-toxic and low-cost polymer material with good solubility and biodegradability, can combine the processability of PVA with the excellent performance of porous filler MOFs, solving the problem that the poor machinability of MOFs and the difficulty of recycling limit the practical application of powdered MOFs and improving the physicochemical properties of PVA, maximizing the advantages of the material to develop a wider range of applications. Firstly, we systematically summarize the preparation of MOF/PVA composite membrane materials using solution casting, electrostatic spinning, and other different methods for such excellent properties, in addition to discussing in detail the various applications of MOF/PVA composite membranes in water treatment, sensing, air purification, separation, antibacterials, and so on. Finally, we conclude with a discussion of the difficulties that need to be overcome during the film formation process to affect the performance of the composite film and offer encouraging solutions.

High-performance multifunctional electrospun fibrous air filter for personal protection: A review

With the increasingly serious air pollution and the rampant coronavirus disease 2019 (COVID–19), preparing high–performance air filter to achieve the effective personal protection has become a research hotspot. Electrospun nanofibrous membrane has become the first choice of air filter because of its small diameter, high specific surface area and porosity. However, improving the filtration performance of the filter only cannot meet the personal needs: it should be given more functions based on high filtration performance to maximize the personal benefits, called, multifunctional, which can also be easily realized by electrospinning technology, and has attracted much attention. In this review, the filtration mechanism of high–performance electrospun air filter is innovatively summarized from the perspective of membrane. On this basis, the specific preparation process, advantages and disadvantages are analyzed in detail. Furthermore, other functions required for achieving maximum personal protection benefits are introduced specifically, and the existing high–performance electrospun air filter with multiple functions are summarized. Finally, the challenges, limitations, and development trends of manufacturing high–performance air filter with multiple functions for personal protection are presented.