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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]

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]

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]

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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]

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]

We studied the effect of sensitization on photocatalytic properties of TiO 2 thin films. We synthesized tetracarboxy-phthalocyanines of Cu (PcTcCu) and Zn (PcTcZn) for using Achar method; TiO 2 thin films were deposited by doctor blade method, after that, thin films were sensitized through chemisorption method. Properties of TiO 2 and sensitized-TiO 2 thin films were studied by measurements of X-ray diffraction (XRD), infrared spectroscopy (IR) and absorption diffuse reflectance. The XRD patterns indicated that sensitization did not affect the crystalline phases radio of the TiO 2 films; furthermore, the optical analysis showed that after sensitization process TiO 2 photophysical properties improved greatly in visible regions. Photocatalytic degradation of methylene blue was studied under visible irradiation in aqueous solution and, the pseudo-first order model was used to obtain kinetic information of the photocatalytic degradation. Results indicated that photocatalytic activities of PcTcZn–TiO 2 and PcTcCu–TiO 2 were 2.8 times and 3.6 times better than TiO 2 thin films, these results also indicated that magnetic properties of metal complex in the phthalocyanines determines the efficiency of sensitizer in photocatalytic process. Finally the efficiency in photocatalytic process improved greatly when methylene blue photo-degradation were assisted with slight amount of H 2 O 2 . [ABSTRACT FROM AUTHOR]

In this work, we show an easy and practical analytical method to quantify the content of heavy metals in grass used to feed cattle located in areas of high vehicle traffic flow. Technique used in this work proved to be useful, easy sample preparation, wide dynamic range, and high performance. Analyzes were performed on a Fluorescence Spectrometer Energy Dispersive X- Ray (EDX). Quantification of metals was performed using the method of fundamental parameters. The analysis of the grass showed high content of elements such as Fe and Mn. Along, results indicated heavy metals concentration was highest in the proximity to the vehicle road, element Fe had highest concentration and element Cu had the lowest concentration, finally we determined minimal distance to the road vehicles to ensure the heavy metals concentration was minimal. [ABSTRACT FROM AUTHOR]

In this work we studied the photo-Fenton oxidation of phenol in aqueous solution using tetra(4-carboxyphenyl)porphyrin iron (III) adsorbed on silicon dioxide (TCPPFe/SiO 2 ) under irradiation of visible light for the generation of hydroxyl radicals. The TCPPFe/SiO 2 was synthesized by the Alder's method and, it was characterized by spectrophotometry UV–vis, FT-IR and electron paramagnetic resonance (EPR). The hydroxyl radicals were detected by chemical trapping through indirect fluorescence of the 2-hydroxyterephthalic acid. The secondary products of the phenol photo-oxidation were analyzed by High Pressure Liquid Chromatography (HPLC) where hydroquinone, catechol and benzoquinone were identified as main products. Finally, we determined and compared the kinetic parameters of the photo-oxidation process using a pseudo-first order model. [ABSTRACT FROM AUTHOR]

Highlights: [•] Tetra(4-carboxypenyl)porphyrin adsorbed on SiO2 with visible light generate singlet oxygen. [•] The absence of the EPR DMPO-O2 − signal evidenced that superoxide anion was not present. [•] Anthraquinone and oxanthrone produced by the decomposition of the endoperoxide intermediary were identified as the only oxidation products of anthracene. [Copyright &y& Elsevier]

Abstract: The generation of superoxide radical anion O2 − from tetra(4-carboxyphenyl)porphyrin (TCPP) adsorbed on TiO2 in DMSO and irradiated by visible light was studied using EPR spectroscopy and 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as spin trap. A chemical filter was used to remove light with wave lengths <500nm. A multiline EPR spectrum was observed, characteristic of a mixture of two adducts, the first corresponding to DMPO–O2 − and the second to the so-called nitroxide-like radical. Hyperfine coupling constants determined for the DMPO–O2 − adduct are: a N =14.1G, a H β =10.8G and a H γ =1.4G, and for the nitroxide-like radical adduct a N =14G. An increased intensity of the EPR lines corresponding to the nitroxide-like radical adduct was observed under irradiation without chemical filter, which suggests a possible DMPO–O2 − decomposition. No singlet oxygen could be detected by EPR spectroscopy using 2,2,6,6-tetramethyl-4-piperidone (TEMP) as spin trap and by chemical trapping using anthracene as the trap. [ABSTRACT FROM AUTHOR]

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]

We deposited bare TiO 2 and TiO 2 /ZnO thin films to study their antimicrobial capacity against Fusarium oxysporum f. sp. dianthi. The deposit of TiO 2 was performed by spin coating and the ZnO thin films were deposited onto the TiO 2 surface by plasma-assisted reactive evaporation technique. The characterization of the compounds was carried out by scanning electron microscopy (SEM) and powder X-ray diffraction techniques. Furthermore, density functional theory (DFT) and time-dependent DFT (TDDFT) calculations were performed to support the observed experimental results. Thus, the removal of methylene blue (MB) by adsorption and posterior photocatalytic degradation was studied. Adsorption kinetic results showed that TiO 2 /ZnO thin films were more efficient in MB removal than bare TiO 2 thin films, and the pseudo-second-order model was suitable to describe the experimental results for TiO 2 /ZnO ( q e = 12.9 mg/g; k 2 = 0.14 g/mg/min) and TiO 2 thin films ( q e = 12.0 mg/g; k 2 = 0.13 g/mg/min). Photocatalytic results under UV irradiation showed that TiO 2 thin films reached 10.9% of MB photodegradation ( k = 1.0 × 10 -3 min -1 ), whereas TiO 2 /ZnO thin films reached 20.6% of MB photodegradation ( k = 3.9 × 10 -3 min -1 ). Both thin films reduced the photocatalytic efficiency by less than 3% after 4 photocatalytic tests. DFT study showed that the highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) energy gap decreases for the mixed nanoparticle system, showing its increased reactivity. Furthermore, the chemical hardness shows a lower value for the mixed system, whereas the electrophilicity index shows the biggest value, supporting the larger reactivity for the mixed nanoparticle system. Finally, the antimicrobial activity against F. oxysporum f. sp. dianthi showed that bare TiO 2 reached a growth reduction of 68% while TiO 2 /ZnO reached a growth reduction of 90% after 250 min of UV irradiation., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

In this work, we fabricated a TiO 2 thin film, and the same film was modified with an Anderson aluminum polyoxometalate (TiO 2 -AlPOM). Physical-chemical characterization of the catalysts showed a significant change in morphological and optical properties of the TiO 2 thin films after surface modification. We applied the kinetic and isothermal models to the methylene blue (MB) adsorption process on both catalysts. The pseudo-second order model was the best fitting model for the kinetic results; qe (mg/g) was 11.9 for TiO 2 thin films and 14.6 for TiO 2 -AlPOM thin films, and k 2 (g mg -1 min -1 ) was 16.3 × 10 -2 for TiO 2 thin films and 28.2 × 10 -2 for TiO 2 -AlPOM thin films. Furthermore, the Freundlich model was suitable to describe the isothermal behavior of TiO 2 , K F (5.42 mg/g), and 1/ n (0.312). The kinetics of photocatalytic degradation was fitted using the Langmuir-Hinshelwood model; k ap was 7 × 10 -4 min -1 for TiO 2 and 13 × 10 -4 min -1 for TiO 2 -AlPOM. The comparative study showed that TiO 2 thin films reach a 19.6% MB degradation under UV irradiation and 9.1% MB adsorption, while the TiO 2 -AlPOM thin films reach a 32.6% MB degradation and 12.2% MB adsorption on their surface. The surface modification improves the morphological, optical, and photocatalytic properties of the thin films. Finally, the DFT study supports all the previously shown results., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

Background: Photodynamic therapy activity against different biological systems has been reported for porphyrins. Porphyrin modifications through peripheral groups and/or by metal insertion inside the ring are main alternatives for the improvement of its photo-physical properties. In this study, we synthesized and characterized 5,10,15,20-tetrakis(4-bromophenyl)porphyrin and the dicloro-5,10,15,20-tetrakis(4-bromophenyl)porphyrinato Sn(IV). Methods: Metal-free porphyrin was synthesized using the Alder method, while the Sn(IV)-porphyrin complex was prepared by combining metal-free porphyrin with stannous chloride in DMF; the reaction yields were 47% and 64% respectively. Metal-free porphyrin was characterized by UV-Vis, FT-IR, ESI-mass spectrometry and 13 C-NMR. Additionally, the Sn(IV) -porphyrin complex was characterized using UV-Vis and FT-IR. Cyclic voltammetry tests in four different solvents. The fluorescence quantum yield (Φ f ) was measured using fluorescein as a standard, the singlet oxygen quantum yield (Φ D ) was estimated using the standard 5,10,15,20-(tetraphenyl)porphyrin (H2TPP) and the quencher of singlet oxygen 1,3-diphenylisobenzofuran (DPBF). Results: UV-Vis assay showed typical Q and Soret bands for porphyrin and its metallo-porphyrin complex. Compounds showed photoluminescence at the visible range of electromagnetic spectrum. The inclusion of the metal in the porphyrin core changed the Φ f from 0.15 to 0.05 and the Φ D increased from 0.55 to 0.59. Finally, the effect of the compounds on the viability of L. panamensis was evaluated by means of the MTT test. The results showed that both compounds decreased the viability of the parasite; this inhibitory activity was greater under light irradiation; the porphyrin compound had IC 50 of 16.5 μM and the Sn(IV)-porphyrin complex had IC 50 of 19.2 μM. Conclusion: The compounds were synthesized efficiently, their characterization was carried out by different spectroscopy techniques and their own signals were evidenced for both structures, both compounds decreased the cell viability of L. panamensis ., Competing Interests: No competing interests were disclosed., (Copyright: © 2021 Espitia-Almeida F et al.)