Flavin mononucleotides (FMNs) and flavin adenine nucleotide (FAD) play vital roles in the electron-transfer processes in diverse enzymatic reactions. Owing to the isoalloxazine chromophore, flavins are easily detectable by surface-enhanced Raman spectroscopy (SERS), a surface-sensitive technique. However, the details of the adsorption of flavins on SERS-active materials have never been investigated. In this study, a comprehensive SERS analysis of flavins containing lumichrome and lumiflavin on silver nanoparticles was conducted. With the aid of density-functional-theory calculations, our results suggested that the flavin molecules were adsorbed on the silver nanoparticles via the N3site of the isoalloxazine moiety, which had a stronger adsorption ability than the adenine moiety in the FAD. The SERS spectra of the flavins at different pH values also supported this conclusion. This study demonstrated the feasibility of SERS for the structural characterization of flavins, paving the way for the functional exploration of flavin-labeled detection sensors and flavoprotein researches.Keywords:flavin;riboflavin;flavin mononucleotide;flavin adenine nucleotide;isoalloxazine;surface-enhanced Raman spectroscopy;DFT;adenine;adenosine triphosphate
CO 2 batteries offer a promising solution for mitigating climate change by reducing CO 2 emissions. Using ammonia, a highly effective gaseous alkali, we can harness chemical energy through its reaction with CO 2 for power generation. However, the lack of direct electron transfer in the ammonia-CO 2 carbonation reaction and ammonia's susceptibility to precious metal catalysis side reactions and corrosion complicate the construction of an efficient battery system. To overcome these challenges, we propose a concept that uses organic catalytic reactions to harness the chemical energy from the CO 2 -ammonia reaction for electricity generation. By employing isoalloxazine derivatives—riboflavin sodium phosphate (FMN-Na)—as proton carriers in redox reactions, we can create battery electromotive force through the proton concentration difference (ΔpH) between CO 2 and ammonia. This approach leverages reversible electrochemical proton-coupled electron transfer (PCET) reactions to drive electron flow and facilitate power generation, without requiring renewable electricity charging. Our study demonstrates that a CO 2 -ammonia battery can achieve a peak power density of 22.5 W.m -2 , converting 1 ton of CO 2 into 60.04 kWh of electricity while producing over 99.60% purity ammonium bicarbonate. Our work combines CO 2 mitigation, electricity generation, and the production of valuable by-products, offering innovative strategies for addressing environmental and energy challenges simultaneously.
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