N-doped defective nanocarbon (N-DNC) catalysts have been widely studied due to their exceptional catalytic activity in many applications, but the O 3 activation mechanism in catalytic ozonation of N-DNCs has yet to be established. In this study, we systematically mapped out the detailed reaction pathways of O 3 activation on 10 potential active sites of 8 representative configurations of N-DNCs, including the pyridinic N, pyrrolic N, N on edge, and porphyrinic N, based on the results of density functional theory (DFT) calculations. The DFT results indicate that O 3 decomposes into an adsorbed atomic oxygen species (O ads ) and an 3 O 2 on the active sites. The atomic charge and spin population on the O ads species indicate that it may not only act as an initiator for generating reactive oxygen species (ROS) but also directly attack the organics on the pyrrolic N. On the N site and C site of the N 4 V 2 system (quadri-pyridinic N with two vacancies) and the pyridinic N site at edge, O 3 could be activated into 1 O 2 in addition to 3 O 2 . The N 4 V 2 system was predicted to have the best activity among the N-DNCs studied. Based on the DFT results, machine learning models were utilized to correlate the O 3 activation activity with the local and global properties of the catalyst surfaces. Among the models, XGBoost performed the best, with the condensed dual descriptor being the most important feature.
The
green and low-cost preparation of carbon dots (CDs) with excellent
fluorescence plays a key role in cell-imaging applications. Herein,
we develop a green photochemical approach for fabricating CDs. The
produced CDs can be used directly in lung cancer A549 cell imaging
without any tedious post-treatments. As nontoxic and green alternatives
to prevent pollution, fatty acids in sole aqueous media are the only
reactants used to synthesize CDs. Furthermore, the green process of
photoirradiation avoids harsh conditions, such as strong acids and
bases, strong oxidants, and high temperatures and pressures. In addition,
the by-products remaining in the aqueous environment are fatty acid
dimers in the form of vesicles, which can also be recycled as gemini
surfactant resources. We demonstrate that this green synthetic method
for fabricating CDs is suitable for fatty acids with different chain
lengths, and therefore, exhibits considerable universality. Fatty
acids, as readily available green resources in nature, and the green
and simple synthesis method without additional pollution provides
a new approach and perspective for the green synthesis of CDs for
bioimaging.
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