Bright room-temperature phosphorescence in fluid water usually demands a rigid glassy matrix or a supramolecular cage that seals the guest away from oxygen; here an open, two-dimensional clay surface serves the same end. We have shown that electrostatically fixing cationic dyes on anionic clay nanosheets restricts their intramolecular rotation, suppresses nonradiative decay, and strongly enhances fluorescence—an effect we have termed surface-fixation induced emission (S-FIE). Whether the same rigidification governs the triplet manifold has remained open: enhanced phosphorescence of a Pt(II) porphyrin on clay has been observed, but it has not been traced to a decay process. Here we fix a cationic Pt(II) porphyrin (Pt-TMPyP), which phosphoresces at room temperature in water through the internal heavy-atom effect, on a synthetic saponite (SSA) and resolve the rate constants behind the enhancement of its room-temperature phosphorescence. The phosphorescence quantum yield Φp rises from 0.031 to 0.17 (about 5.5-fold), while the phosphorescence lifetime lengthens from 5.86 to 19.5 μs (about 3.3-fold). Resolving the individual decay rate constants shows that the enhancement is driven by an about fourfold suppression of the nonradiative rate constant knr—the same rotational rigidification that underlies fluorescence S-FIE—acting together with an about 1.6-fold rise in the radiative rate constant. Temperature-dependent emission points to the same origin: surface fixation halves the apparent activation energy of triplet decay, from 24 to 12 kJ mol−1. The oxygen-quenching rate constant kq also falls to 0.64 times its solution value, consistent with shielding of one face of the dye by the nanosheet; this protection from oxygen has no counterpart in the singlet manifold. S-FIE thus extends from the singlet to the triplet manifold, and clay nanosheets offer a room-temperature aqueous phosphorescence platform that needs no rigid matrix.
This study presents a machine-learning-guided hydrothermal strategy for optimizing Cobalt-modified ZnFe2O4 (ZF–Co) photocatalysts. Moreover, a novel scalable porous inorganic coating platform compatible with retrofit implementation on existing urban infrastructures was developed for visible-light-driven atmospheric pollutant mitigation. A hydrothermal synthesis database containing 320 experimentally synthesized ZF–Co samples was generated using temperature (120–250 °C), duration (4–24 h), cobalt concentration (0–20 wt%), and urea-to-metal molar ratio (1.8–9) as input variables, while BET specific surface area (SBET) was selected as the optimization target. Linear regression, random forest, and XGBoost models were implemented for prediction and optimization. The optimized ZF–Co photocatalyst was subsequently characterized using BET, XRD, FESEM/EDS, TEM/HRTEM, FTIR, and UV–Vis analyses and incorporated into a porous lithium-silicate-based coating containing dispersant and foaming agents. The coating was deposited onto cementitious substrates and evaluated by continuous-flow photocatalytic degradation of NOx, formaldehyde, and toluene under UV-A and visible-light irradiation, along with wettability, compressive strength, and pull-off adhesion tests. XGBoost achieved the highest predictive accuracy with R2 = 0.947 and RMSE = 4.49 m2 g−1, identifying an optimum synthesis condition of ∼198 °C, ∼6.8 h, ∼12.2 wt% Co, and ∼2.7 urea-to-metal ratio. Experimental validation yielded a maximum SBET of 126.4 m2 g−1 with only ∼3.0% deviation from the predicted value. The optimized coating achieved ∼58% NO conversion and ∼42% total NOx removal under UV irradiation, while visible light still provided ∼37% and ∼28% removal, respectively. Formaldehyde degradation reached ∼94% under UV and ∼79% under visible light, whereas toluene degradation reached ∼61% and ∼37%, respectively. The coating additionally exhibited a hydrophobic transition from ∼31.6°–33.1° to ∼128.4°–129.3°, preserved compressive strength at ∼40 MPa, and achieved pull-off adhesion strengths of ∼2.1–2.65 MPa. Overall, the results establish a foundation for ML-assisted optimization of ferrite photocatalysts and scalable durable photocatalytic coatings for existing urban infrastructures and diverse construction materials without compromising their intrinsic mechanical functionality or durability. All Python codes and the experimental dataset are provided in the Appendix to ensure reproducibility.
Access to safe water remains a critical challenge in achieving Sustainable Development Goal 6. Solar-driven water treatment is a promising decentralized strategy to address this issue; however, its implementation is hindered by limited spectral utilization and the lack of integrated disinfection functions. Herein, we report a broadband solar-responsive supra-ceramic composite comprising titania nanosheets and silver nanoparticles (TNS/AgNP), exhibiting continuous optical absorption/extinction spanning from ultraviolet to near-infrared (NIR) regions. This composite exhibits a water evaporation rate of 1.05 kg m−2 h−1 under light irradiation. Moreover, the material exhibits dual-mode antibacterial activity against methicillin-resistant Staphylococcus aureus, integrating silver-ion-mediated disinfection in the dark with enhanced photothermal antibacterial effects under NIR irradiation while maintaining high cytocompatibility. These results establish TNS/AgNP as a multifunctional photothermal material platform integrating broadband light harvesting and antibacterial functionality.
