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Ciprofloxacin (CIP) is a substance that, although it shows benefits to human beings due to its antibiotic activity, is also an organic pollutant of difficult removal from the environment via conventional methods. As an alternative, photocatalytic methods may promote the degradation of this molecule to non-toxic compounds. Beyond that, photocatalysts with different morphologies may present diverse performances in the reaction process. In this study, the photoactivity of CeO2 nanostructured materials (CeNTs and CeO2) was evaluated in the photodegradation of CIP, and a possible photodegradation mechanism was proposed. The CeNTs and CeO2 were obtained from alkaline hydrothermal synthesis and calcination of Ce(NO3)3.6H2O, respectively. Based on the TG, XRD, SEM, and UV–Vis diffuse reflectance characterizations, it was verified that the materials are partially hydrated, constituted by CeO2 with crystalline cubic fluorite structure and Fm-3 m space group, and with morphologies formed by an aggregate of particles (CeO2) and a fibrillar morphology (CeNTs). XPS revealed changes in the surface states and Ce4+ to Ce3+ ratio, indicating a greater amount of oxygen vacancies in the fibrillar nanostructures. Both showed optical activity in the presence of UV light and a reduction of band gap energies, going from 2.95 for CeO2 to 2.80 for CeNTs. The CIP removal by photodegradation was 61% and 89% for the CeO2 and CeNTs, respectively. The higher photocatalytic activity of the CeNTs was attributed to better superficial and optical properties, resulting in an increase in the velocity of photoactivation with the final degradation of CIP being approximately 28% higher than the CeO2. Therefore, it was confirmed that the fibrillar morphology can change properties of CeO2 and increase your applications as photocatalyst. [ABSTRACT FROM AUTHOR]

In this work, antibiotic pyrazinamide (PZA) photodegradation on palygorskite (Pal), NiWO4 crystals, and NiWO4-Pal (2, 6, and 10%) nanocomposites was evaluated under polychromatic irradiation. In the characterization of the samples, XRD patterns displayed good crystallinity for NiWO4 crystals and nanocomposites. In addition, the diffractograms were used in the Rietveld refinement for phase indexing, revealing a wolframite-type monoclinic structure with the space group P2/c. The active vibrational modes related to the characteristic groups of the samples were identified using Raman and FTIR spectroscopy. Photoluminescence (PL) spectra revealed that NiWO4 and NiWO4-Pal (2%) nanocomposite have the highest electron-hole pair recombination rate, and the contribution of the green component in the NiWO4-Pal (2%) nanocomposite indicates a greater contribution of deep energy levels to the PL profile. DRS in the UV-visible region indicated that NiWO4 crystals have indirect band-gap energy (Egap) 2.64 eV; NiWO4-Pal (2, 6, and 10%) nanocomposites have 2.62, 2.58, and 2.59 eV, respectively; and Pal has 2.83 eV. The catalytic tests showed that the NiWO4-Pal (2%) nanocomposite samples, under polychromatic radiation, exhibit greater efficiency in photodegradation at 110 min, with yield of 98.5%. The ROS tests indicated that the studied reactive species play a similar role in PZA photodegradation. [ABSTRACT FROM AUTHOR]

In this paper, we report the synthesis of CuWO4, MnWO4, and FTO|CuWO4|MnWO4 as type II heterojunction thin film prepared by the drop-casting method. These thin films were synthesized by microwave-hydrothermal method with pure phase formation confirmed by X-ray diffraction (XRD), micro-Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS) analyses. The photoelectrochemical response of these films was investigated under simulated illumination with AM 1.5 G type filter. The heterojunction displayed photocurrent density values two times higher than the FTO|CuWO4 film, reaching 39 μA/cm2 at 1.23 V versus normal hydrogen electrode. Optical and electrochemical characterizations revealed superior visible light absorption and lower charge transfer resistance for the FTO|CuWO4|MnWO4 heterojunction thin film. Low photoluminescence emission and transient photocurrent data confirmed a decreased electronic charge transfer between the valence and the conduction band, besides a reduced electron–hole recombination rate for the FTO|CuWO4|MnWO4 heterojunction film. Mott-Schottky photocurrent response investigation revealed that the FTO|CuWO4|MnWO4 heterojunction thin film can be considered an excellent photoanode for photoelectrocatalytic applications under solar irradiation. Finally, the heterojunction exhibited better performance for the photodegradation of Rhodamine B (RhB), corresponding to 55.5% at 165 min. [ABSTRACT FROM AUTHOR]

Summary: In this article, we report a solar cell prepared with p‐type cuprous oxide (Cu2O) and n‐type gamma‐tungsten oxide (γ‐WO3) films combined by an redox electrolyte in a configuration similar to that used in dye‐sensitized solar cells. Cu2O films were prepared by the electrochemical method in three different pH conditions. X‐ray diffraction patterns revealed that the Cu2O films presented a crystalline phase with cubic structure after deposition, whereas the n‐type γ‐WO3 film was prepared by the drop‐casting method. Optical analyses showed that both oxide films absorb visible light. After the photoelectrochemical characterization of the films, solar cells configured like a "sandwich" (Cu2O/electrolyte/γ‐WO3) were assembled and investigated under irradiation of 100 mW cm−2. The solar cell with I−/I3− redox pair showed better results than that prepared with polysulfide K2S/Sn2− electrolyte. For each solar cell, the investigated parameters were short‐circuit current density, open‐circuit voltage, fill factor, maximum power, and cell efficiency. The method proposed here can be considered new, promising, and simple for the preparation of solar cells with a p–n junction. [ABSTRACT FROM AUTHOR]