No abstract

Perfluorooctanesulfonate (PFOS) is a compound that has wide applications with extreme persistence in the environment and the potential to bioaccumulate, and could induce adverse effects to ecosystems. We investigated the degradation of PFOS by laccase-induced enzyme catalyzed oxidative humification reactions (ECOHRs) using 1-hydroxybenzotriazole (HBT) as a mediator. Approximately 59% of PFOS was transformed over 162 days of incubation, and the reaction appeared to follow a pseudo-first-order model with reaction rate constant of 0.0066/ d ( r = 0.87) under one condition tested. Using differential absorption spectra and theoretical simulation, we elucidated the interaction between Cu/Mg and PFOS, and proposed that Cu and Mg could serve as a bridge to bring the negatively charged PFOS and laccase to proximity, thus increasing the chance of radicals that are released from laccase to reach and react with PFOS. In addition, density functional theory modeling showed that PFOS complexation to the metal ions could unlock its helical configuration and decrease the C-C bond energy of PFOS. These changes allow the attack of PFOS C-C backbone by radicals to become easier. On the basis of products identification, we proposed that direct attack of PFOS by the HBT radical initiated the free radical chain reaction processes and led to the formation of fluoride and partially fluorinated compounds. These results suggest that ECOHR is a potential pathway by which PFOS could be degraded in the environment, and it may make a viable approach to remediate PFOS contamination via amendment of appropriate enzymes and mediators.

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Inspired by recent experimental observation of molecular morphology and theoretical predictions of multiple properties of cyclo [18]carbon, we systematically studied photophysical and nonlinear optical properties of cyclo[2N]carbons (N = 3−15) allotropes through density functional theory. This work unveils the unusual optical properties of the sp-hybridized carbon rings with different sizes. The remarkable size dependence of optical properties of these systems and its underlying natures are profoundly explored, and the relevance between aromaticity and optical properties are highlighted. The extrapolation curves fitted for energy level of frontier molecular orbitals, maximum absorption wavelength, and (hyper)polarizability of considered carbon rings are presented, which can be used to reliably predict corresponding properties for arbitrarily large rings.The findings in this study will facilitate the exploration of potential application of the cyclocarbons in the field of optical material. File list (2) download file view on ChemRxiv Manuscript.docx (2.01 MiB) download file view on ChemRxiv Supporting Information.docx (2.22 MiB)