The growing production and extensive use of pharmaceuticals have resulted in their frequent detection in various environmental compartments. Ciprofloxacin (CIP), a fluoroquinolone antibiotic used for treating respiratory, urinary tract, and gastrointestinal infections, is increasingly present in aquatic environment due to its intensive medical application and incomplete removal in conventional treatment systems. In response to the tightening of environmental regulations aimed at reducing pollutant emissions, the development of efficient and sustainable methods for eliminating pharmaceutical contaminants has become a priority. Among promising approaches, advanced oxidation processes stand out for their ability to generate highly reactive radicals under relatively mild operating conditions, enabling effective degradation of persistent pollutants.

In this study, the photodegradation of CIP was investigated under simulated sunlight using heterogeneous photocatalysis. Degradation kinetics was monitored with particular attention devoted to several operational parameters: catalyst type (ZnO and TiO₂), catalyst loading (0.5–5.0 mg/mL), initial CIP concentration (0.025–0.125 mmol/L), and photoreactor design. Complete removal of CIP was achieved within 60 min using both photocatalysts. The results indicate that increasing catalyst loading slightly decreases removal efficiency within the tested range, with the highest performance obtained at 0.5 mg/mL. Similarly, increasing initial CIP concentration led to a moderate reduction in degradation efficiency, with the most effective removal observed at 0.025 mmol/L. The higher photocatalytic performance observed with the xenon lamp reactor was attributed to its UVA light intensity, which was 26.1 times greater than that of the reactor with the halogen lamp. Finally, the reusability of ZnO was assessed over three successive cycles under identical conditions. A gradual decline in efficiency was observed, likely due to the adsorption of degradation products blocking active sites on the photocatalyst surface.

Acknowledgements

The financial support of the Ministry of Science, Technological Development and Innovation of the Republic of Serbia (Grants No. ‪451-03-137/2025-03/ 200125 & 451-03-136/2025-03/200125).

Photocatalysis-induced phenomena, such as active motion and superhydrophilicity, have been widely studied [1,2]. In this presentation, we introduce a previously unrecognized effect: photocatalysis-induced electric fields [3]. Using monoclinic bismuth vanadate (BiVO4) films and potassium dichromate (K2Cr2O7) as a model reduction system, we demonstrate that illumination generates long-range electric fields extending hundreds of micrometers into the surrounding solution. Spatially resolved concentration measurements and transport analysis reveal that these fields strongly bias the migration of charged reactants toward the photocatalyst surface. The same behavior is observed in an independent system based on TiO2, indicating that this phenomenon is not limited to a specific material or crystal structure.

Unlike the localized interfacial fields commonly discussed in semiconductor heterojunctions, these extended electric fields enhance dichromate transport by more than three orders of magnitude, thereby maintaining a continuous reactant supply. As a result, the overall photocatalytic reduction rate is significantly improved without additional energy input, catalyst restructuring, or complex reactor engineering. We argue that photocatalysis-induced electric fields represent a new handle for coupling light-driven redox chemistry with ion transport. This concept opens an unexplored design space for optimizing photocatalytic reactors and may be generalizable to other oxidation or reduction processes relevant to green synthesis, solar fuel production, and environmental catalysis.

References

[1] K. Villa, M. Pumera. Fuel-free light-driven micro/nanomachines: artificial active matter mimicking nature. Chem. Soc. Rev., 2019, 48: 4966-4978.

[2] A. Fujishima, X. Zhang, D.A. Tryk. TiO₂ photocatalysis and related surface phenomena. Surf. Sci. Rep., 2008, 63: 515-582.

[3] C. Chen, S. Zhao, B. Zhou, C. Ye, B. Jiang, L. Zhang. Enhancing dichromate transport and reduction via electric fields induced by photocatalysis. iScience, 2025, 28.

The efficiency of photocatalytic reactions depends critically on the ability of a catalyst to absorb photons with energies that match the activation barrier of the desired chemical process. However, identifying metal–ligand complexes that can absorb a specific photon energy (Ea) remains a major challenge due to the vast diversity of possible combinations and the nonlinear relationship between molecular structure and electronic excitation energy. In this work, we present a machine learning framework that performs inverse design of photoactive complexes—accepting a target energy input (Ea) and predicting metal–ligand combinations capable of absorbing photons with that energy to catalyze a specified transformation.
The model leverages patterns learned from computational and experimental data to identify how structural and electronic features influence photon absorption. By reversing this relationship, the algorithm can suggest promising complexes tailored to the energy requirements of a given reaction. This approach enables a rational, data-driven route to photocatalyst discovery, reducing reliance on empirical screening and expensive quantum chemical calculations. Beyond identifying suitable complexes for specific activation energies, the framework offers a foundation for designing light-responsive materials across a range of catalytic and energy-conversion processes. It represents a step toward fully automated materials discovery, where machine learning can translate energetic requirements directly into molecular design strategies.

Two dinuclear oxovanadium(V) complexes with water solubility, [(L1H)VO(μ-O)]₂ (C1) and [(L2H)VO(μ-O)]₂ (C2), were successfully synthesized via the reaction of VOSO₄ with their respective tetradentate Schiff base ligands, namely [N-(2-hydroxyethylamino)ethyl]-5-methoxysalicylaldimine (L1H) and 2-[(2-(2-hydroxyethylamino)ethylimino)methyl]phenol (L2H), under reflux in methanol. The synthetic procedure afforded the complexes in good yields and with high purity, as confirmed by spectroscopic analyses and elemental composition. These dinuclear Schiff base oxovanadium complexes were systematically evaluated for their catalytic activity in the oxidation of olefins using water as a green and environmentally benign solvent in combination with various oxidizing agents. The experimental results demonstrated high catalytic efficiency, excellent product yields, and remarkable reusability, highlighting the potential of these complexes as sustainable catalysts in aqueous media. Beyond their catalytic applications, these oxovanadium(V) complexes possess significant photophysical and electrochemical properties, including strong absorption in the visible region and tunable redox potentials. These characteristics render them promising candidates for photovoltaic applications, particularly in dye-sensitized solar cells (DSSCs) and other solar energy conversion devices, where efficient light harvesting and electron transfer are essential. The combination of water solubility, catalytic performance, and photophysical features makes these complexes versatile functional materials for both chemical and energy-related applications.

In the present investigation, a novel ternary nanocomposite, MgO/g-C₃N₄/Bi₂O₃, was successfully fabricated via a wet impregnation technique. The photocatalytic efficacy of this hybrid system was thoroughly assessed for the degradation of various organic pollutants, namely the antibiotic amoxicillin (AMX), the pesticide chlorpyrifos (CPF), and the dye methylene blue (MB), under visible light irradiation in an aqueous medium. Extensive physicochemical characterizations were performed employing XRD, SEM, TEM, EDS, XPS, UV-DRS, PL, BET, and EIS analyses. XRD patterns confirmed the coexistence of crystalline phases corresponding to hexagonal g-C₃N₄, monoclinic Bi₂O₃, and cubic MgO, with their respective characteristic planes distinctly discernible in the composite. Morphological investigations using SEM and TEM illustrated a hybrid structure composed of nanosheets interspersed with nanorods. Optical studies revealed enhanced visible light harvesting and a reduced bandgap energy of 2.3 eV, promoting efficient photoexcitation. Under optimized conditions—10 ppm pollutant concentration, pH 6, 100 mg catalyst dosage, and 90 minutes of visible light illumination—the nanocomposite achieved remarkable degradation efficiencies of 96.2% (MB), 74.2% (CPF), and 62.7% (AMX), substantially surpassing the performances of its individual components (g-C₃N₄, Bi₂O₃, and MgO). Radical quenching experiments identified photoinduced holes (h⁺) and superoxide radicals (O₂·⁻) as the primary reactive species orchestrating the degradation pathways. Importantly, the photocatalyst exhibited excellent structural robustness and maintained high photocatalytic activity over three consecutive cycles, demonstrating superior reusability and stability. These findings establish the MgO/g-C₃N₄/Bi₂O₃ nanocomposite as a highly efficient, visible-light-responsive photocatalyst for the sustainable remediation of organic contaminants in aquatic systems.

The rational design of supramolecular assemblies enables precise modulation of molecular optical properties through controlled intermolecular interactions. This study employs density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations to investigate the structure–property relationships governing the second-order nonlinear optical (NLO) responses in host–guest complexes formed between C₆₀ and carbon nanoring derivatives (B-PLY-CPP and N-PLY-CPP). The optimized geometries of B-PLY-CPP@C₆₀ and N-PLY-CPP@C₆₀ confirm stable convex–concave π–π stacking, with interaction energies of approximately –35 kcal/mol. The static​ first hyperpolarizability (β_tot), calculated at the CAM-B3LYP/6-31G(d) level, reveals that the N-doped complex (N-PLY-CPP@C₆₀) achieves a β_tot value of 1.01 × 10⁴ au, which is significantly higher than that of its B-doped analogue and is competitive with classic push–pull NLO chromophores. This enhancement correlates directly with a more efficient intermolecular charge transfer from the nanoring host to the C₆₀ guest, as evidenced by a substantial red-shift in the calculated low-energy absorption band. Analysis using a two-level model confirms that the superior NLO response originates from a lower transition energy and a larger transition dipole moment associated with this charge-transfer excitation. The results provide comparative mechanistic insights​ into how heteroatom doping and supramolecular organization can be used to tailor charge-transfer excited-state characteristics and enhance second-order NLO activity in carbon-based materials, highlighting a viable supramolecular strategy for property modulation.

Understanding how composition controls photoluminescence is essential for improving semiconductor nanomaterials used in optical sensing and light-emitting technologies. In this work, cadmium sulfide (CdS) nanostructures were synthesized using a sonochemical method with different Cd:S molar ratios (1:0.1, 1:0.25, 1:0.5, 1:0.75, and 1:1), and their structural and emission properties were systematically investigated. Ultrasound-driven nucleation produced nanocrystals ranging from irregular Cd-rich aggregates to well-defined, uniform particles at stoichiometric compositions. XRD analysis revealed a controlled phase transition from purely hexagonal CdS to mixed hexagonal–cubic structures, with crystallite sizes between ~6 and 35 nm.

Photoluminescence measurements demonstrated two characteristic emission regions: near-band-edge (≈420 nm) and deep-level defect-related bands (≈540–560 nm). Emission intensity and spectral position were strongly dependent on precursor stoichiometry. The 1:1 sample showed the highest PL intensity with a dominant emission around 547 nm, indicating enhanced defect-assisted radiative recombination. In contrast, intermediate compositions, particularly 1:0.5, exhibited broadened PL bands and suppression of higher-order Raman modes, consistent with phonon confinement and increased surface defect activity. UV–Vis absorption confirmed composition-dependent band gap modulation, reflecting quantum confinement and defect state evolution.

These results show that tuning the Cd:S ratio provides a simple and effective strategy for controlling crystal phase, defect density, and photoluminescent behavior in CdS nanomaterials. This approach is promising for light-emitting devices, UV photodetectors, and photochemistry-driven optoelectronic applications.