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In this work, TiO2 and Anderson-type polyoxometalates (Ni, Co, and Fe) thin-film composites were fabricated. The composites were characterized by FTIR and Raman spectroscopy, diffuse reflectance, and scanning electronic microscopy. The methylene blue (MB) photocatalytic degradation on the composites under UV irradiation was studied. Spectroscopic results verified the modification of TiO2 thin films. Optical and morphological properties changed after TiO2 modification. The largest change in the optical band gap was observed for the FePOM/TiO2 system, which reported a value of 3.05 eV. The POM/TiO2 systems were more efficient in methylene blue (MB) adsorption than bare TiO2. Furthermore, the modified films were more efficient than bare TiO2 during MB photodegradation tests. The NiPOM/TiO2 and the CoPOM/TiO2 were the most efficient in the MB adsorption, reaching ~20%. The NiPOM/TiO2 and the CoPOM/TiO2 composites were the most efficient in the photodegradation process, reaching ~50% of MB removal. The stability tests indicated that composite films were moderately stable after the three performed reusability cycles. Thus, these results suggest that POM modification of TiO2 can improve the adsorption and photodegradation capacity of semiconductors. [ABSTRACT FROM AUTHOR]

In the information contained herein, we fabricated biochar by means of a pyrolysis process; it used Prosopis juliflora waste (PJW) as a biomass source. The physical and chemical material characterization was carried out through FTIR, thermogravimetric, BET-N2 isotherm, and SEM-EDX assays. We studied the methylene orange (MO) adsorption onto PWJ biochar. The PJW biochar displayed a maximum percentage of MO removal of 64%. The results of the adsorption study indicated that Temkin isotherm was suitable to describe the MO adsorption process on PJW biochar; it suggests that the MO adsorption on PJW biochar could be a multi-layer adsorption process. Results showed that the pseudo-second-order model was accurate in demonstrating the MO adsorption on PJW (k2 = 0.295 g mg−1min−1; qe = 8.31 mg g−1). Furthermore, the results made known that the MO removal by PJW biochar was endothermic (ΔH = 12.7 kJ/mol) and a spontaneous process (ΔG = −0.954 kJ/mol). The reusability test disclosed that after four consecutive adsorption/desorption cycles, the PWJ biochar reduced its MO removal by only 4.3%. [ABSTRACT FROM AUTHOR]

Photodynamic therapy (PDT) is a promising technique for the treatment of various diseases. In this sense, the singlet oxygen quantum yield (Φ∆) is a physical–chemical property that allows to stablish the applicability of a potential photosensitizers (PS) as a drug for PDT. In the herein report, the Φ∆ of three photosensitizers was determined: metal-free tetrahydroxyphenyl porphyrin (THPP), THPP-Zn and the THPP-V metal complexes. Their biological application was also evaluated. Therefore, the in vitro study was carried out to assess their biological activity against Escherichia coli. The metal-porphyrin complexes exhibited highest activities against the bacterial strain Escherichia coli. at the highest concentration (175 μg/mL) and show better activity than the free base ligand (salts and blank solution). Results indicated a relation between Φ∆ and the inhibitory activity against Escherichia coli, thus, whereas higher is the Φ∆, higher is the inhibitory activity. The values of the Φ∆ and the inhibitory activity follows the tendency THPP-Zn > THPP > THPP-V. Furthermore, quantum chemical calculations allowed to gain deep insight into the electronic and optical properties of THPP-Zn macrocycle, which let to verify the most probable energy transfer pathway involved in the singlet oxygen generation. [ABSTRACT FROM AUTHOR]

In this work, we fabricated and characterized ZnO and TiO2 thin films, determining their structural, optical, and morphological properties. Furthermore, we studied the thermodynamics and kinetics of methylene blue (MB) adsorption onto both semiconductors. Characterization techniques were used to verify thin film deposition. The semiconductor oxides reached different removal values, 6.5 mg/g (ZnO) and 10.5 mg/g (TiO2), after 50 min of contact. The pseudo-second-order model was suitable for fitting the adsorption data. ZnO had a greater rate constant (45.4 × 10−3) than that of TiO2 (16.8 × 10−3). The removal of MB by adsorption onto both semiconductors was an endothermic and spontaneous process. Finally, the stability of the thin films showed that both semiconductors maintained their adsorption capacity after five consecutive removal tests. [ABSTRACT FROM AUTHOR]

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In this work, tetra(4-carboxyphenyl)porphyrin (TCPP) and two Anderson-type polyoxomolybdates (containing Cu and Zn, respectively; CuPOM, ZnPOM) were synthesized and deposited on TiO2 thin films. The properties of the obtained materials were characterized through UV–vis spectroscopy, Fourier transform infrared spectroscopy (FT-IR), diffuse reflection spectroscopy, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). The adsorption and photodegradation under the visible light irradiation of methylene blue (MB) were studied for TiO2, TCPP/TiO2, TCPP/CuPOM/TiO2 and TCPP/ZnPOM/TiO2 thin films in aqueous solution. The results of the diffuse reflectance showed two bands in the visible light spectrum for the TCPP/POM/TiO2 systems compared to unmodified TiO2 that does not show any bands in the same region of the spectrum. The TCPP/POM/TiO2 systems showed a higher removal of MB, with an adsorption rate near to 31% for the TCPP/CuPOM/TiO2 film compared to 9% adsorption on the TiO2 film. The kinetic results show that the pseudo-second order model was the best fitting model for the MB adsorption process onto fabricated materials. The photodegradation studies under visible light showed a better performance on TCPP/POM/TiO2 thin films, with an efficiency in the MB photodegradation of near 49% and 44% in aqueous solution for TCPP/CuPOM/TiO2 and TCPP/ZnPOM/TiO2, respectively. The reusability test indicated that the porphyrin films are moderately stable after the performed cycles. [ABSTRACT FROM AUTHOR]

Copyright of Iteckne is the property of Universidad Santo Tomas, Division de Ingenierias and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Prospectiva (1692-8261) is the property of Universidad Autonoma del Caribe and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Antioxidants act as quenchers or scavengers of oxidative free radicals and singlet oxygen (1O2); these compounds are effective in the treatment of diseases associated with oxidative stress and food preservation. We studied the antioxidant activity of hesperidin which was isolated from mandarin (Citrus reticulata) fruit peels against singlet oxygen (1O2). High-performance liquid chromatography with diode array detection was used for chemical characterization. The total singlet oxygen quenching rate constants of the hesperidin was measured by using the Stern–Volmer model. Results showed an overall quenching rate constant with a value of 6.43 × 107 M−1 s−1 for 1O2, which for the best of our knowledge has not been reported before. Furthermore, quantum chemical calculations were performed to get insight into the molecular and electronic structure properties of this antioxidant, which confirms that the quenching mechanism through energy transfer is rarely probable and that 1O2 could interact with the methoxy phenyl charge rich fragment of the molecule. [ABSTRACT FROM AUTHOR]

Copyright of Prospectiva (1692-8261) is the property of Universidad Autonoma del Caribe and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Prospectiva (1692-8261) is the property of Universidad Autonoma del Caribe and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this work, we studied the effect of TiO2 sensitization with dry biomass extracted of cyanobacteria on the degradation of methylene blue dye (AM). Cyanobacterial cultures isolated from water samples were collected from the swamp of Malambo in Colombia; two main genera of cyanobacteria were identified, and they were cultivated with BG-11 culture medium. The concentrations of chlorophyll a in the exponential and stationary phases of growth were measured; the phycobilin content was quantified by spectrophotometry. Thin films of TiO2 were deposited by a doctor blade method, and they were sensitized by wet impregnation. Furthermore, a methylene blue (MB) photodegradation process was studied under visible light irradiation on the cyanobacterial biomass sensitized TiO2 material (TiO2/sensitizer); besides, the pseudo-first-order model was used to obtain kinetic information about photocatalytic degradation. The results showed that the BG-11+ treatment reported a higher amount of dry biomass and phycobiliproteins. After the sensitization process, the TiO2/sensitizer thin films showed a significant red shift in the optical activity; besides the thin film roughness decreasing, the TiO2/sensitizer showed photocatalytic activity of 23.2% under visible irradiation, and besides, the kinetic (kap) constant for TiO2/sensitizer thin films was 3.1 times greater than the kap value of TiO2 thin films. Finally, results indicated that cyanobacterial biomass is a suitable source of natural sensitizers to be used in semiconductor sensitization. [ABSTRACT FROM AUTHOR]

Copyright of Prospectiva (1692-8261) is the property of Universidad Autonoma del Caribe and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this work, we fabricated system In(O,OH)S/i-ZnO/n+-ZnO to be used as potential optical window in thin films solar cells. i-ZnO/n+-ZnO thin films were synthesized by reactive evaporation (RE) method and In(O,OH)S thin films were synthesized by chemical bath deposition (CBD) method; all thin films were deposited on soda lime glass substrates. Thin films were characterized through X-ray diffraction (XRD), atomic force microscopy (AFM), and spectral transmittance measurements. Structural results indicated that both thin films were polycrystalline; furthermore, morphological results indicated that both thin films coated uniformly soda lime glass substrate; besides, optical characterization indicated that system had more than 80% of visible radiation transmittance. [ABSTRACT FROM AUTHOR]

Copyright of Prospectiva (1692-8261) is the property of Universidad Autonoma del Caribe and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Prospectiva (1692-8261) is the property of Universidad Autonoma del Caribe and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Prospectiva (1692-8261) is the property of Universidad Autonoma del Caribe and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The accumulation of cyanobacteria produced due to eutrophication processes and the increment of different pollutants in water as a result of industrial processes affects aquatic environments such as the ocean, rivers, and swamps. In this work, cyanobacterial biomass was used as a biosorbent for the removal of a commercial dye, methylene blue (MB). Thus, MB was removed from biomass obtained from cyanobacterial samples collected from the swamp located in the Colombian Caribbean. Spectroscopical techniques such as FTIR, SEM, EDX measurements were used for the physico-chemical characterization of the bio-adsorbent material. Furthermore, we present the effect of various adsorption parameters such as pH, MB dose, time, and adsorbent concentration on the adsorbent equilibrium process. Three different isotherm models were used to model the MB adsorption on biomass. The functional groups identified on biomass suggest that these models are suitable for the characterization of the sorption of cationic dyes on the surfaces of the biomass; in addition, an SEM assay showed the heterogeneous surface of the biomass' morphology. The equilibrium tests suggested a multilayer type adsorption of MB on the biomass surface. The kinetics results show that a pseudo-second order kinetic model was suitable to describe the MB adsorption on the biomass surface. Finally, the herein obtained results give an alternative to resolve the eutrophication problems generated by cyanobacterial growth in the swamp "Ciénaga de Malambo". [ABSTRACT FROM AUTHOR]

Chemical bath deposition (CBD) is a suitable, inexpensive, and versatile synthesis technique to fabricate different semiconductors under soft conditions. In this study, we deposited Zn(O;OH)S thin films by the CBD method to analyze the effect of the number of thin film layers on structural and optical properties of buffer layers. Thin films were characterized by X-ray diffraction (XRD) and UV-Vis transmittance measurements. Furthermore, we simulated a species distribution diagram for Zn(O;OH)S film generation during the deposition process. The optical results showed that the number of layers determined the optical transmittance of buffer layers, and that the transmittance reduced from 90% (with one layer) to 50% (with four layers) at the visible range of the electromagnetic spectrum. The structural characterization indicated that the coatings were polycrystalline (α-ZnS and β-Zn(OH)2 to four layers). Our results suggest that Zn(O;OH)S thin films could be used as buffer layers to replace CdS thin films as an optical window in thin-film solar cells. [ABSTRACT FROM AUTHOR]

We synthesized and characterized both Co-doped ZnO (ZnO:Co) and Cu-doped ZnO (ZnO:Cu) thin films. The catalysts' synthesis was carried out by the sol–gel method while the doctor blade technique was used for thin film deposition. The physicochemical characterization of the catalysts was carried out by Raman spectroscopy, scanning electron microscopy (SEM), X-ray diffraction, and diffuse reflectance measurements. The photocatalytic activity was studied under visible irradiation in aqueous solution, and kinetic parameters were determined by pseudo-first-order fitting. The Raman spectra results evinced the doping process and suggested the formation of heterojunctions for both dopants. The structural diffraction patterns indicated that the catalysts were polycrystalline and demonstrated the presence of a ZnO wurtzite crystalline phase. The SEM analysis showed that the morphological properties changed significantly, the micro-aggregates disappeared, and agglomeration was reduced after modification of ZnO. The ZnO optical bandgap (3.22 eV) reduced after the doping process, these being ZnO:Co (2.39 eV) and ZnO:Co (3.01 eV). Finally, the kinetic results of methylene blue photodegradation reached 62.6% for ZnO:Co thin films and 42.5% for ZnO:Cu thin films. [ABSTRACT FROM AUTHOR]

In this work, we studied the anthracene oxidation by hydroxyl radicals. Hydroxyl radical was generated by reaction of 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin Fe (III) (TPPFe) with hydrogen peroxide under visible radiation at a nitrogen atmosphere. The TPPFe was synthesized by Adler Method followed by metal complexation with Fe (III) chloride hexahydrate. Hydroxyl radical was detected by fluorescence emission spectroscopy and we studied kinetic of anthracene selective oxidation by hydroxyl radicals through the differential method. The TPPFe was characterized by UV-Vis spectrophotometry, Dynamic Light Scattering (DLS) and Scanning Electron Microscopy (SEM) measurements. The results indicated that TPPFE was compound by micro-particles with a size distribution of around 2500 nm. Kinetic results showed that the apparent rate constant for the oxidation of anthracene increased exponentially on as temperature increases, furthermore, the activation energy for the Anthracene oxidation by hydroxyl radicals under visible irradiation was 51.3 kJ/mol. Finally, anthraquinone was the main byproduct generated after oxidation of anthracene by TPP-Fe under visible irradiation. [ABSTRACT FROM AUTHOR]