Resazurin (Alamar Blue, RZ) is a widely utilized fluorescent probe for biological sensing, whose fluorescent intensity can be modulated by changing its redox states; thereby, electrochemical reactivity of RZ is of significance when designing a sensing assay. Herein, we report novel two-way electrochemical reactivity modulation of RZ using host-guest complexation with rigid molecular containers cucurbit[ n ]uril (CB n , n = 7, 8). The complexation between CB n and RZ is confirmed by 1 H NMR measurements and supported by computational simulation, and the binding constants are determined via UV-vis titration. Notably, the voltametric data highlights that the redox reactivity of RZ can be activated or deactivated upon encapsulation by CB8 or CB7, respectively. This two-way reactivity modulation is hypothesized to be mediated by the difference in cavity volume that favors or hinders the approach of water molecules to the encapsulated reaction center during the reduction process. Despite the similar cavity size to CB, molecular containers such as cyclodextrins (CDs) exhibit considerably weaker modulation effects. Our approach can potentially be applied to other redox processes that involve proton transfer, and open new possibilities in supramolecular electrochemistry.
Developing a sensitive and reliable method for accurate determination of H 2 is of great importance for effective and safe utilization of H 2 in various conditions. A fluorescence (FL) assay for H 2 detection was proposed in the present work. It relied on the fact that Pd/C nanocomposites catalyzed fluorogenic conversion of weakly-FL resazurin (RZR) into highly-FL resorufin (RSR) was triggered by H 2 under ambient condition. This method possessed a limit of detection (LOD) as low as 0.06% volume concentration of H 2 in air, far below 4% that is the generally recognized as the lower explosion limit of H 2 -air mixture. A high selectivity to H 2 over O 2 , N 2 , Ar and CO 2 as well as broad linear response range from 0.2% to 80% made this method promising for H 2 sensing in a variety of circumstances. Most importantly, the developed method was able to detect practical H 2 atmosphere (2% H 2 in air) with high reliability under simple operation.
Microbial fuel cell (MFC) with lignocellulose as an electron donor is considered a sustainable biorefinery. However, low lignocellulose degradation and energy output restrict the scale of application. Herein, the extracellular electron transfer (EET) capacity of Acetivibrio thermocellus DSM 1313 with lignocellulose as substrate was shown to be mediated by the self-produced flavin, and its intracellular electron transfer went through the whole respiratory chain. Thermophilic MFC with resazurin exhibited an increase in the open circuit voltage by 37.78%, and a 2.60 folds increase in power density of 77.85 mW/m 2 , respectively. Differential pulse voltammetry and electrochemical impedance spectroscopy analysis indicated that resazurin decreased the solution and anode charge transfer resistance, and enhanced the extracellular electrochemical activity. Furthermore, resazurin resulted in a lower redox potential, allowing preferential electron transfer to resazurin rather than flavin. This research establishes a resazurin-mediated thermophilic MFC with lignocellulose as substrate, which provides novel idea on the biomass refinery.
危险品化学品经营许可证（带存储）