Adsorption, excitation analysis, and the mechanism of tetracycline photodegradation by Ca12O12-PEDOT, Mg12O12-PEDOT, and Zn12O12-PEDOT hybrid materials: Perspective from first-principles study

Tetracycline (TC) residues threaten aquatic ecosystems by infiltrating water bodies and disrupting aquatic life, potentially affecting the food chain. In our quest to address this ecological concern, we embarked on a fascinating investigation exploring the photodegradation of tetracycline using nanocomposite materials: Ca12O12-PEDOT, Mg12O12-PEDOT, and Zn12O12-PEDOT within the framework of density functional theory (DFT) at the omega B97XD/ def2svp method. The results obtained showed that tc@Ca12O12-PEDOT composite exhibited unparalleled stability with an adsorption distance of 1.922 angstrom, surpassing its counterparts tc@Mg12O12-PEDOT and tc@Zn12O12-PEDOT. The tc@Ca12O12_PEDOT system displayed a compact energy gap, suggesting its superior photon absorption capability from the valence band compared to the others. The sequential order of stabilization energies was observed as follows: Zn12O12-PEDOT > Mg12O12-PEDOT > Ca12O12-PEDOT, with values of 73.26 kcal/mol, 49.35 kcal/mol, and 10.66 kcal/mol, respectively. The analysis of charge transfer showed that tc@Mg12O12_PEDOT had the highest magnitude of charge transfer, followed by tc@Zn12O12_PEDOT and tc@Ca12O12_PEDOT. The characterization of the hole and electron separation through the computed back donation revealed a distinct pattern: tc@Zn12O12_PEDOT > tc@Mg12O12_PEDOT > tc@Ca12O12_PEDOT. The presence of t-index >0 indicated substantial hole and electron separation due to charge transfer. The investigation into hole and electron distribution exhibited a small Hole Distribution Index (HDI), signifying a narrow spatial extent of this charge separation. The order of spatial extent was found to be tc@Zn12O12_PEDOT > tc@Ca12O12_PEDOT > tc@Mg12O12_PEDOT. Similar conclusions can be drawn for the Electron Distribution Index (EDI). When comparing tc@Mg12O12_PEDOT with tc@Ca12O12_PEDOT, we observed a fascinating redshift in the first excited state (41.83 nm), second excited state (27.01 nm), and third excited state (7.59 nm).

Automated summary

Tetracycline residues pose a threat to aquatic ecosystems, and the nanocomposite material Ca12O12-PEDOT exhibits excellent stability and photon absorption capability, suggesting its potential use in the photodegradation of tetracycline.