Qiongzhen Liu

Hierarchically Three-Dimensional Nanofiber Based Textile with High Conductivity and Biocompatibility As a Microbial Fuel Cell Anode

Microbial fuel cells (MFCs) encompass complex bioelectrocatalytic reactions that converting chemical energy of organic compounds to electrical energy. Improving the anode configuration is thought to be a critical step for enhancing MFCs performance. In present study, a hierarchically structured textile polypyrrole/poly(vinyl alcohol-co-polyethylene) nanofibers/poly(ethylene terephthalate) (referred to PPy/NFs/PET) is shown to be excellent anode for MFCs. This hierarchical PPy/NFs/PET anode affords an open porous and three-dimensional interconnecting conductive scaffold with larger surface roughness, facilitating microbial colonization and electron transfer from exoelectrogens to the anode. The mediator-less MFC equipped with PPy/NFs/PET anode achieves a remarkable maximum power density of 2420 mW m(-2) with Escherichia coli as the microbial catalyst at the current density of 5500 mA m(-2), which is approximately 17 times higher compared to a reference anode PPy/PET (144 mW m(-2)). Considering the low cost, low weight, facile fabrication, and good winding, this PPy/NFs/PET textile anode promises a great potential for high-performance and cost-effective MFCs in a large scale.

The woven fiber organic electrochemical transistors based on polypyrrole nanowires/reduced graphene oxide composites for glucose sensing

Novel woven fiber organic electrochemical transistors based on polypyrrole (PPy) nanowires and reduced graphene oxide (rGO) have been prepared. SEM revealed that the introduction of rGO nanosheets could induce the growth and increase the amount of PPy nanowires. Moreover, it could enhance the electrical performance of fiber transistors. The hybrid transistors showed high on/off ratio of 102, fast switch speed, and long cycling stability. The glucose sensors based on the fiber organic electrochemical transistors have also been investigated, which exhibited outstanding sensitivity, as high as 0.773 NCR/decade, with a response time as fast as 0.5s, a linear range of 1nM to 5μM, a low detection concentration as well as good repeatability. In addition, the glucose could be selectively detected in the presence of ascorbic acid and uric acid interferences. The reliability of the proposed glucose sensor was evaluated in real samples of rabbit blood. All the results indicate that the novel fiber transistors pave the way for portable and wearable electronics devices, which have a promising future for healthcare and biological applications.

A specially structured conductive nickel-deposited poly(ethylene terephthalate) nonwoven membrane intertwined with microbial pili-like poly(vinyl alcohol-co-ethylene) nanofibers and its application as an alcohol sensor

The trend in development of portable and wearable sensors in healthcare-related applications promotes an expanding demand for flexible, stretchable and electrically conductive fabrics. A novel structured conductive nickel-deposited poly(ethylene terephthalate) (PET) membrane intertwined with microbial pili-like poly(vinyl alcohol-co-ethylene) (PVA-co-PE) nanofibers has been prepared. FTIR and XRD analysis indicated that the deposited metallic nickel was semi-crystalline with a FCC structure. SEM observations showed that nickel was compactly deposited on the surfaces of the nanofibers and PET substrate in the Ni@nanofibers/PET membranes. The coated nanofibers acted as conductive bridges among the randomly entangled PET fibers, leading to a significant increase in the conductivity of Ni@PVA-co-PE nanofibers/PET membranes. Abrasion tests suggested that Ni@PVA-co-PE nanofibers/PET membranes have superior stability in electrical conductivity compared to that of the native Ni@PET membrane. The membrane with high conductivity and good stability was employed as an electrode to construct a capacitive alcohol sensor. The sensor demonstrated good sensitivity and high efficiency.

Amine-functionalized PVA-co-PE nanofibrous membrane as affinity membrane with high adsorption capacity for bilirubin

In this study, poly(vinyl alcohol-co-ethylene) (PVA-co-PE) nanofibrous membrane was activated by sodium hydroxide and cyanuric chloride, and then the activated membranes were functionalized by 1,3-propanediamine, hexamethylenediamine and diethylenetriamine to be affinity membranes for bilirubin removal, respectively. The chemical structures and morphologies of membranes were investigated by SEM, FTIR and XPS. And the adsorption ability of different amine-functionalized nanofibrous membranes for bilirubin was characterized. Furthermore, the effects of temperature, initial concentration of bilirubin, NaCl concentration and BSA concentration on the adsorption capacity for bilirubin of diethylenetriamine-functionalized nanofibrous membrane were studied. Results indicated that the adsorption capacity for bilirubin of diethylenetriamine-functionalized nanofibrous membrane could reach 85mg/g membrane when the initial bilirubin concentration was 200mg/L while the adsorption capacity could be increased to 110mg/g membrane if the initial bilirubin concentration was more than 400mg/L. The dynamic adsorption of diethylenetriamine-functionalized nanofibrous membrane showed that the ligands of amine groups on the membrane surface could be used as far as possible by recirculating the plasma with certain flow rates. Therefore, the diethylenetriamine-functionalized PVA-co-PE nanofibrous membrane possessed high adsorption capacity for bilirubin and it can be candidate as affinity membrane for bilirubin removal.

Large scale poly(vinyl alcohol-co-ethylene)/TiO2 hybrid nanofibrous filters with efficient fine particle filtration and repetitive-use performance

Severe air pollution results in a great demand for high-yielding nanofiber-based materials with excellent filtration performance. In this work, PVA-co-PE/TiO2 hybrid nanofibrous filters on PP nonwoven supports were prepared on a large scale via a melt phase separation and suspension coating technique. The hybrid nanofibers doped by TiO2 nanoparticles have a diameter in the range from about 50 nm to 300 nm. With increasing fiber coverage density, the average pore size of the hybrid nanofibrous filter media declines from 10 μm for PP nonwoven to less than 500 nm. Compared to pristine PVA-co-PE nanofibrous filter media, the hybrid nanofibrous filters exhibit much higher filtration efficiency and lower pressure drop, which further induces an increased quality factor by about 167%. This is mainly attributed to the enhanced electrostatic absorption between hybrid nanofibers and NaCl aerosol nanoparticles caused by the polarity of TiO2. Besides, the secondary factor is the slightly weakened direct-interception ability of the filter media with increased pore size. Furthermore, it was found that a multilayered-structure was generated by the cyclic swilling–drying handling. This structure results in the steadily increasing particle-collection capability and quality factor of PVA-co-PE/TiO2 hybrid nanofibrous filter media, implying its superiority in the application as an air filter media with high filtration efficiency and repetitive-use performance.

Hydrogel degradation triggered by pH for the smart release of antibiotics to combat bacterial infection

Here we developed a hydrogel that could be triggered by a change in pH to degrade and smartly release antibiotics to combat a bacterial infection; use of this hydrogel could reduce the inappropriate and disproportionate use of antibiotics.

A facile route to the production of polymeric nanofibrous aerogels for environmentally sustainable applications

Mesoporous polymeric aerogels with high compressibility and durability have attracted great attention due to their environmentally sustainable applications. However, it is still challenging to develop polymeric aerogels in a simple, low-cost and mass produced way. Herein, we report a strategy to prepare a high porosity polymeric nanofibrous aerogel (referred to as NFA) by direct freeze-drying of the poly(vinyl alcohol-co-ethylene) (PVA-co-PE) nanofibrous suspension. It is noteworthy that this process is free of gelation and any solvent exchange. In addition, the PVA-co-PE nanofibers were mass-produced from our production line, based on a high throughput Melt-Extrusion-Phase-Separation technique. Additionally, the network of the NFA aerogels can be tuned by the host–guest assembly of the nanofibers and the foreign PVA nano-lamellae from disordered/ordered cellular to a leaf-like structure. Further modification of the NFA by gaseous methyltrichlorosilane (MTS) led to covalently bonded siloxane nanoparticles formed on the surface, thereby facilely realizing the nanofibrous aerogel from hydrophilic to hydrophobic as well as achieving excellent resilience. The corresponding hydrophobic aerogel (designated as HNFA) possessed a slightly larger density of 11.1 mg cm−3 with an almost unchanged porosity of 99% and meso–macroporous pores of 5–100 nm compared with the NFA (8.3 mg cm−3). They are demonstrated as good thermal insulators (0.033–0.044 W m−1 K−1), high-performance air filters (99.2% filtration efficiency with 64 Pa pressure drop), organic pollutants absorbers (2500–5329% weight gain) and continuous water/oil separators. Therefore, this study opens up a new approach for simple and large-scale preparation of polymeric aerogels for versatile applications.

Concurrent filtration and inactivation of bacteria using poly(vinyl alcohol-co-ethylene) nanofibrous membrane facilely modified using chitosan and graphene oxide

Integrating multiple nanoscale components with antibacterial properties into a single membrane filter is indispensable for efficient application in water treatment. Herein, we prepare a poly(vinyl alcohol-co-ethylene) (PVA-co-PE) nanofibrous membrane (NFM) decorated using chitosan (CS) and graphene oxide (GO), via a melt-phase-separated nanofiber/CS-GO suspension coating technique. As indicated by morphology and structure analysis, CS and GO have tight physical attachment to the surface of the nanofibers throughout the PVA-co-PE layer, with diminished pore size and contact angle. Compared to commercial PVDF membrane, NFMs exhibit enhanced retention rate of pigmented nanoparticles and bacterial cells and higher and more stable water flux due to their relatively small thickness and high stacking density. The performance for inactivation of bacteria is also improved by employing NFM. Particularly after CS/GO modification, the inactivation rate of the membrane is increased to the range of 97.8–99.5% against E. coli and S. aureus with superior repetitive-use performance. These results can be attributed to the enhancement effect of the nanofiber network on the activity of the hydroxyl groups in PVA-co-PE, NH3+ in chitosan and the 2D structure of graphene oxide. The present membranes have much potential for use in long-term water treatment with high efficiency and stability.

Immobilization of Firefly Luciferase on PVA-co-PE Nanofibers Membrane as Biosensor for Bioluminescent Detection of ATP

The bioluminescent reaction catalyzed by firefly luciferase has become widely established as an outstanding analytical system for assay of adenosine triphosphate (ATP). When in solution, the luciferase is unstable and cannot be reused. The problem can be partially solved by immobilizing the luciferase on solid substrates. The poly(vinyl alcohol-co-ethylene) (PVA-co-PE) nanofibers membrane has abundant active hydroxyl groups on the surface. The PVA-co-PE nanofibers membrane was first activated by cyanuric chloride with triazinyl group. Then the activated PVA-co-PE nanofibers membrane was subsequently reacted with 1,3-propanediamine and biotin. The firefly luciferase was immobilized onto the surface of 1,3-propanediamine- and biotin-functionalized membranes. The surface chemical structure and morphologies of nanofibers membranes were characterized by FTIR-ATR spectra and SEM. The hydrophilicity of membranes was tested by water contact angle measurements. The detection of fluorescence intensity displayed that the firefly-luciferase-immobilized PVA-co-PE nanofibers membranes indicated high catalytic activity and efficiency. Especially, the firefly-luciferase-immobilized nanofiber membrane which was functionalized by biotin can be a promising candidate as biosensor for bioluminescent detection of ATP because of its high detection sensitivity.

Continuously Producible Ultrasensitive Wearable Strain Sensor Assembled with Three-Dimensional Interpenetrating Ag Nanowires/Polyolefin Elastomer Nanofibrous Composite Yarn

Fiber-shaped strain sensors with great flexibility and knittability have been tremendously concerned due to the wide applications in health manager devices, especially in human motion detection and physiological signal monitoring. Herein, a novel fiber-shaped strain sensor has been designed and prepared by interpenetrating Ag nanowires (NWs) into polyolefin elastomer nanofibrous yarn. The easy-to-obtain structure and simple roll-to-roll process make the continuous large-scale production of nanofibrous composite yarn possible. The continuous and alternating stretching and releasing reversibly change the contact probability between AgNWs in this interpenetrating network, leading to the variations of electrical resistance of the sensor. The gauge factors of strain sensors are calculated to be as high as 13920 and the minimum detection limit is only 0.065%. In addition, the strain sensor shows excellent durability during 4500 cycles with the strain of 10%. The response times of stretching and releasing strains are 10 and 15 ms, respectively. Furthermore, the strain sensor has been successfully applied in human motion detections both in single yarn and knitted fabrics. The result shows the practicability in applications of monitoring limbs movements, eye motion changes, artificial vocal cords, human pulse, and complex motions, which shows great potential in wearable sensors and electronic skin.