Self-assembly of cell-embedding reduced graphene oxide/ polypyrrole hydrogel as efficient anode for high-performance microbial fuel cell.

A three-dimensional (3D) macroporous reduced graphene oxide/polypyrrole (rGO/Ppy) hydrogel assembled by bacterial cells was fabricated and applied for microbial fuel cells. By taking the advantage of electroactive cell-induced bioreduction of graphene oxide and in-situ polymerization of Ppy, a facile self-assembly by Shewanella oneidensis MR-1and in-situ polymerization approach for 3D rGO/Ppy hydrogel preparation was developed. This facile one-step self-assembly process enabled the embedding of living electroactive cells inside the hydrogel electrode, which showed an interconnected 3D macroporous structures with high conductivity and biocompatibility. Electrochemical analysis indicated that the self-assembly of cell-embedding rGO/Ppy hydrogel enhanced the electrochemical activity of the bioelectrode and reduced the electron charge transfer resistance between the cells and the electrode. Impressively, extremely high power output of 3366 ± 42 mW m-2 was achieved from the MFC with cell-embedding rGO/Ppy hydrogel rGO/Ppy, which was 8.6 times of that delivered from the MFC with bare electrode. Further analysis indicated that the increased cell loading by the hydrogel and improved electrochemical activity by the rGO/Ppy composite would be the underlying mechanism for this performance improvement. This study provided a facile approach to fabricate the biocompatible and electrochemical active 3D nanocomposites for MFC, which would also be promising for performance optimization of various bioelectrochemical systems.

Stimuli-responsive cellulose nanomaterials for smart applications.

Stimuli-responsive cellulose nanomaterials (CNMs), which change their physicochemical properties in response to specific stimuli have recently been in the spotlight. A great deal of effort has been dedicated to developing stimuli-responsive CNMs in the past two decades. However, the majority of stimuli-responsive CNMs were achieved via the introduction of stimuli-responsive moieties rather than taking advantage of their inherent switchable hydrogen bonds, electrostatic interactions, and molecular polarization in CNMs. In this review, recent advances and future perspectives of stimuli-responsive CNMs that exploiting the inherent switchable hydrogen bonds, reversible electrostatic interactions, and tunable polarization are highlighted. The principles for designing and assembling such smart CNMs are summarized. Stimuli-responsive CNMs that are sensitive to the changes in humidity, chemical molecules, pH, pressure, and electricity represent tremendous opportunities for making advances in sensors, actuators, biomedical applications due to their sensitivity, specificity, and stability. Additionally, major challenges and future perspectives of stimuli-responsive CNMs are reported.