Spectroscopy, Morphology, and Electrochemistry of Electrospun Polyamic Acid Nanofibers

In-situ constructing porous N-doped carbon skeleton with rich defects from modified polyamide acid to boost the high performance of Na3V2(PO4)3 cathode for full sodium-ion batteries

Generally, the transport of electrons and Na+ is seriously constrained in Na3V2(PO4)3 (NVP) due to intense interactions of V-O and PO bonds. Besides, polyamide acid (PAA) is hardly used in the sol-gel route due to insolubility. This work develops a facile liquid synthesis strategy based on modified PAA, achieving in-situ construction of a porous N-doped carbon framework with rich defects to improve the kinetics of NVP. The addition of triethylamine (TEA) reacts with carboxyls in PAA to achieve acid-base neutralization, turning PAA into polyamide salts with good solubility. The special morphology construction mechanism of this unique system was observed by ex-situ scanning electron microscopy (SEM) and Transmission electron microscopy (TEM). Specifically, PAA undergoes in-situ conversion into chain-like polyimide (PI) through a thermal polymerization mechanism during the pre-sintering process. Meanwhile, NVP precursors are evenly dispersed in the PI fibers, efficiently reducing the particle size. After the final treatment, the favorable porous carbon skeleton could be generated derived from the partial decomposition of PI, on which small active grains are in situ grown. The resulting N-doped carbon substrate contains rich defects, benefiting from the migration of Na+. Furthermore, the porous construction is conducive to alleviating the stress and strain generated by the high current impact, increasing the contact area between electrodes/electrolytes to improve the utilization efficiency of active substances. Comprehensively, the optimized samples exhibit a capacity of 82.1 mAh g-1 at 15C with a retention rate of 95.45 % after 350 cycles. It submits a capacity of 67.6 mAh g-1 at 90C and remains 52.2 mAh g-1 after 1500 cycles. Even in full cells, it reveals a value of 110.6 mAh g-1. This work guides the application of in-situ multiple modifications of polymers in electrode materials.

Electrospun nanofiber-based glucose sensors for glucose detection

Diabetes is a chronic, systemic metabolic disease that leads to multiple complications, even death. Meanwhile, the number of people with diabetes worldwide is increasing year by year. Sensors play an important role in the development of biomedical devices. The development of efficient, stable, and inexpensive glucose sensors for the continuous monitoring of blood glucose levels has received widespread attention because they can provide reliable data for diabetes prevention and diagnosis. Electrospun nanofibers are new kinds of functional nanocomposites that show incredible capabilities for high-level biosensing. This article reviews glucose sensors based on electrospun nanofibers. The principles of the glucose sensor, the types of glucose measurement, and the glucose detection methods are briefly discussed. The principle of electrospinning and its applications and advantages in glucose sensors are then introduced. This article provides a comprehensive summary of the applications and advantages of polymers and nanomaterials in electrospun nanofiber-based glucose sensors. The relevant applications and comparisons of enzymatic and non-enzymatic nanofiber-based glucose sensors are discussed in detail. The main advantages and disadvantages of glucose sensors based on electrospun nanofibers are evaluated, and some solutions are proposed. Finally, potential commercial development and improved methods for glucose sensors based on electrospinning nanofibers are discussed.