Photocatalytic Decolorization Efficiency Research Articles

Standardization of silver nanoparticle synthesis: Photocatalytic application (immobilized with chitosan complex) with textile dyes and antibacterial activity against Staphylococcus aureus using banana pseudo stem

The purpose of the study is to standardize the silver nanoparticle (BP-AgNPs) synthesis and its antibacterial activity and photocatalytic application with the selected dyes using the banana pseudo stem extract. “One-factor analysis (OFTA)” was carried out for the standardization of silver nanoparticle synthesis and nanoparticle-chitosan complex immobilization. The parameters were identified with plant quantity (20 g), silver nitrate concentration (1 mM), the ratio of plant extract and silver nitrate solution (2:8), pH (12), temperature (37 °C), dispersed light conditions, shaking conditions (120 rpm), and time (6 h) were analysed. The photocatalytic decolorization efficiency of the standardized BP-AgNPs (immobilized with chitosan complex) has shown 96.92% for methylene blue (10 ppm) at 3 h and 97.55% for safranin (100 ppm) at 15 h. The antibacterial activity for the synthesised BP-AgNPs was determined. MIC value of the BP-AgNPs was determined to be 15.62 μg. mL−1 for S. aureus. The synthesised BP-AgNPs treated with 0.5×, 1× and 2× MIC concentration (x = 15.62 μg. mL−1) showed decreased viable counts of S. aureus (99.6% at 2× concentration having viable count of 22.6 × 102 CFU. mL−1) at 24 h incubation when compared with the control culture. The structural characteristics of the BP-AgNPs were identified as spherical with SEM and the size was identified as 12.19 ± 1.62 nm with TEM and as 37.23 ± 17.89 nm with XRD. The parameters such as FTIR, Zeta potential, EDS further supports the nanoparticle synthesis with banana pseudostem extract. The current result suggested that, the silver nanoparticles (BP-AgNPs) synthesised using the extract of the banana pseudo stem could be used as an alternative source for dye decolorization and antibacterial activities.

Green synthesis and characterization of silver nanoparticles from sandalwood (Santalum album L.) extract for efficient catalytic reduction, antioxidant and antibacterial activity

Metal nanoparticles that have been manufactured in a green environment have been recognized as potentially useful materials for the development of nanomedicine due to the fact that they are eco-friendly, non-toxic, and durable. Silver nanoparticles (AgNPs) have been demonstrated to be beneficial in a variety of applications, including those in the fields of biomedicine and environmental protection, according to research. Our study aims to prepare AgNPs using sandalwood (Santalum album L.) extract. Sandalwood-based silver nanoparticles (SW-AgNPs) that were characterized using a variety of techniques, including UV–Vis spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy-energy dispersive X-ray (SEM-EDS) analysis. The antioxidant activity of the produced SW-AgNPs was examined in relation to the radical scavenging of 2,2-diphenyl-1-picrylhydrazyl (DPPH) and showed a maximum of 80.21 ± 0.91% after the concentration of SW-AgNPs was set at 500 μg/mL. The antibacterial efficiency of SW-AgNPs was tested against infection causing bacteria (Staphylococcus aureus and Pseudomonas aeruginosa) with zones of inhibition of 17.2 and 12.3 mm, respectively. The SW-AgNPs showed photocatalytic decolorization efficiency of around 71.3% and 92.14% for the Malachite green (MG), methylene blue (MB) dyes respectively, after a 150 min incubation. The results that were obtained therefore present a potential way for the green synthesis of SW-AgNPs utilizing S. album L. extract, which has significant applications in the fields of biopharmaceuticals and catalysis.

Synthesis of hematite (α-Fe2O3) nanoparticles by a liquid-phase microplasma-assisted electrochemical process for photocatalytic activity

Dye contamination is becoming a more significant environmental challenge with the development of the textile industry. Scientists from all over the world are working hard to create new, more efficient ways to reduce environmental pollution through environmentally friendly synthesis techniques. In this regard, hematite (α-Fe2O3) nanoparticles have been synthesized by the novel, quick, cheap, and environmentally safe microplasma technique for the photodegradation of rhodamine-B under direct Sunlight. Thus, the synthesized α-Fe2O3 nanoparticles were characterized by various characterization techniques such as x-ray diffraction (XRD), scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), and ultraviolet-visible spectroscopy (UV–vis spectroscopy). The structural and optical properties were found to vary with changing precursor concentrations. We measured the photocatalytic decolorization efficiency of synthesized hematite (α-Fe2O3) nanoparticles for rhodamine-B dye under direct Sunlight. It was found that α-Fe2O3 nanoparticles exhibited a decolorization capability with 73.75% decolorization of the dye at the rate of 0.04305 g.mg−1.min−1 after 100 min of irradiation, exhibiting excellent performance to remove organic contaminants from wastewater.

Graphene quantum dot and iron co-doped TiO2 photocatalysts: Synthesis, performance evaluation and phytotoxicity studies

The present study reports the synthesis, photocatalytic decolorization of reactive black 5 dye and phytotoxicity of graphene quantum dots (GQDs) and iron co-doped TiO2 photocatalysts via modified sol gel method. GQDs were synthesized by direct pyrolysis of citric acid (CA). Scanning electron microscopy (SEM) and energy dispersion spectroscopy (EDS), Raman spectroscopy, atomic force microscopy (AFM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), diffuse reflectance spectroscopy (DRS), Brunauer–Emmett–Teller (BET) and photoluminescence spectroscopy (PL) were used to determine the physicochemical properties of the best performing photocatalysts. The results indicated improved physicochemical properties of GQD-0.1Fe-TiO2-300 with root mean square roughness (Rz) (33.82 nm), higher surface area (170.79 m2 g−1), pore volume (0.08 cm3 g−1), and bandgap (2.94 eV). Moreover, GQD-0.1Fe co-doping of TiO2 greatly improved the photocatalytic decolorization efficiency for RB5 dye. The photocatalytic reaction followed the pseudo first order reaction with gradual decrease in Kapp values for increment in RB5 concentration. The KC value was obtained as 2.45 mg L−1 min−1 while the KLH value was 0.45 L mg−1 indicating the heterogeneous reaction system followed the Langmuir-Hinshelwood isotherm and simultaneously occurring adsorption and photocatalytic processes. Photocatalytic reaction mechanism studies exhibited the holes and OH radicals as the main active species in the GQD-0.1Fe-TiO2-300 responsible for the decolorization of RB5. The proposed reaction pathway showed that both Fe-TiO2 and GQDs play important role in generation of electrons and holes. Additionally, GQD-0.1Fe-TiO2-300 were durable up to four cycles. Phytotoxicity assay displayed that treated water and best performing photocatalysts had no effect on Lycopersicon esculentum seed germination. Therefore, the proposed system can pave a viable solution for safe usage of dye loaded wastewater and effluent for irrigation after treatment.

Facile Synthesis of Spinel CoCr2O4 and Its Nanocomposite with ZrO2: Employing in Photo‐catalytic Decolorization of Fe (II)-(luminol-Tyrosine) Complex.

In this project, the deep green power from spinel cobalt chromite (CoCr2O4) nano-crystals carried out using the co-precipitation method and then calcinated at 600 oC for 4 hours. This produced nano-crystal (spinel CoCr2O4) fabricated using the ultrasonic technique to link it with zirconium dioxide (ZrO2) in ratios 1:2 and 1:3, respectively. The X-ray diffraction (XRD), scan electron microscopy (SEM), and energy-dispersive X-rays (EDX), as well as ultraviolet-visible spectrophotometry used to describe the characterizations of prepared materials. The XRD analysis demonstrated that the spinel CoCr2O4 synthesis and their composites were found to be nanoparticles. XRD spectra indicated that the spinel CoCr2O4 is successfully loaded on ZrO2, because, the 2θ of ZrO2 is shifted toward a high 2θ value after spinel CoCr2O4 loaded. This case is attituded to the tiny Co2+ and Cr3+ ions combined with Zr4+ ‌in crystal lattice. The SEM images and EDX spectra of these obtained nanomaterials were found to be spherical agglomerations with an enhanced degree of surface roughness after surface fabrication. On the other side, the bandgap of spinel CoCr2O4 nanocrystals elevated from 3.2 to 4.8 eV with increasing the ZrO2 dose. Under UV-A light, the photocatalytic decolorization efficiency of Fe (II)-(luminol-Tyrosine) complex utilizing spinel CoCr2O4 nanocrystals was tested, and it increases from 17.57 % to 30.67% and 41.97% when its nanocomposite was used in 1:2 and 1:3 ratios, respectively. The elevated efficiency after modified the spinel CoCr2O4 surface with ZrO2 as nanocomposite, due to increasing the acidity of the spinel CoCr2O4 surface that enhances the adsorption of hydroxyl on its surface then generality of the hydroxyl radical, and reducing the recombination. The photoreaction using spinel CoCr2O4 nanocrystals, ZrO2, and their composites were followed pseudo-first-order kinetics depended on the complex concentration.

A reusable chitosan/TiO2@g-C3N4 nanocomposite membrane for photocatalytic removal of multiple toxic water pollutants under visible light.

Photocatalysis has been proved to be a promising approach in wastewater purification. However, it is hard to recycle powdery photocatalysts from wastewater in industry, but immobilizing them using larger materials can overcome this drawback. For that reason, TiO2@g-C3N4 was embedded into chitosan to synthesize a highly reusable and visible-light-driven chitosan/TiO2@g-C3N4 nanocomposite membrane (CTGM). CTGM showed enhanced photoactivity and the photocatalytic efficiencies of the toxic water pollutants methyl orange (M.O.), rhodamine B (Rh.B), chromium (VI) (Cr (VI)), 2,4-dichlorophenol (2,4-DCP) and atrazine (ATZ) were more than 90% under visible light at ambient conditions. Significantly, CTGM was easy to recycle and showed excellent reusability: there was no decrease in the photocatalytic decolorization efficiency of Rh.B throughout 10 cycles. A continuous-flow photocatalysis system was set up and 90% of Rh.B was effectively decolorized. A simple approach was developed to prepare a novel, effective and visible-light-driven membrane that was easy to reuse, and a feasible photocatalysis continuous-flow system was designed to be a reference for wastewater treatment in industry.

Crystal structure dependent photocatalytic degradation of manganese and titanium oxides composites

Crystalline hexagonal disk-shaped anatase TiO2 within manganese oxide (Mn2O3) nanorods has been fabricated to form manganese oxide-titanium dioxide (MnT) composites following sonochemical approach. The unique morphology of the synthesized MnT provides higher surface area to enhance the adsorption efficiency and promotes electron–hole separation. This appears particularly promising for efficient photocatalysis. The photocatalytic decolorization efficiency (PD) of sonosynthesized MnT (S-MnT) was tested via decomposition of an organic pollutant, malachite green oxalate under ultraviolet irradiation and compared to that of sol–gel synthesized MnT (H-MnT). The profound impact of hydrogen peroxide (H2O2) addition on the photoactivity was tested. S-MnT with addition of sonicated H2O2 showed the best photoactivity (PD 99.61% in 50 min) in comparison to sol–gel synthesized H-MnT (PD 92.14% in 60 min). The mechanism of degradation was found to depend on the formation of superoxide radicals (O −·2 ), hydroxyl radicals (·OH) and the defect concentration. The role of ultrasound in the overall degradation process was also discussed. Photoluminescence studies demonstrate that Mn2+ ions are in an octahedral and tetrahedral coordination in both the composites which is favourable for light emission.

Synthesis and Characterization of Fe(II) Doped CdS Nanoparticles and Photodegradation of Acid Blue – 29 (AB-29) Dye

The present work is aimed at the synthesis of Fe(II) doped CdS nanoparticles and investigating the photocatalytic decolorization efficiency of synthesized nanoparticles against Acid Blue (AB-29) dye solution under varying controlling parameters such as catalyst dose, initial concentration of dye and pH. The samples were prepared by colloidal chemical precipitation method and characterized by X-ray diffraction and HRTEM techniques. The results were evaluated by using visible absorption spectroscopy. The obtained results witnessed the high photocatalytic decolorization efficiency of Fe(II) doped CdS nanoparticles at the pH 8.<div><br></div>

Modeling and optimization of Photocatalytic Decolorization of binary dye solution using graphite electrode modified with Graphene oxide and TiO2.

In this paper, the experimental design methodology was employed for modeling and optimizing the operational parameters of the photocatalytic degradation of a binary dye solution using a fixed photocatalytic compound. The compound used was modified graphite electrode (GE) with graphene oxide (GO) on which TiO2 nanoparticles were immobilized. GO nanoparticle was deposited on graphite electrode (GO-GE) using electrochemical approach. TiO2 nanoparticles were immobilized on GO-GE by solvent evaporation method. A binary solution containing mixture of methylene blue (MB) and acid red 14 (AR14) was chosen as dye model. The degradation intermediates were detected and analyzed using gas chromatography. Effect of different factors on the photocatalytic decolorization efficiency was investigated and optimized using response surface methodology (RSM). The obtained results indicated that the prepared TiO2-GO-CE can decolorize MB with high efficiency (93.43%) at pH11, dye concentration of 10mg/L and 0.04g of immobilized TiO2 on the GO fabricated plates after 120min of photocatalytic process. It was demonstrated that by modifying GE with GO the stability of the electrode was remarkably enhanced. The ANOVA results (R2 = 0.97 and P value <0.0001 for MB, R2 = 0.96 and P value <0.0001 for AR14) and numerical optimization showed that it is possible to make good prediction on decoloration behavior and save time and energy with less number of experiments using design of experiments (DoE) like the RSM. Graphical abstract Wastewater treatment processWastewater treatment process.

Entrapment of TiO2 and ZnO powders in alginate beads: Photocatalytic and reuse efficiencies for dye solutions and toxicity effect for DNA damage

Abstract Semiconductor photocatalysts; zinc oxide (ZnO) and titanium dioxide (TiO2) were used to entrap in calcium alginate (Ca-Alg) beads for photocatalytic oxidation of azo dye solutions. The decolorization of two textile dyes, Basic Red 18 (BR18) and Reactive Red 180 (RR180), was investigated in this study. The effect of catalyst loading and initial dye concentration were systematically evaluated. Complete decolorization (100%) of RR180 was obtained by ZnO/Ca-Alg beads at 10 g/L loading and 25 mg/L initial dye concentration for 180 min. However, at the same conditions, decolorization of 45.6% of RR180 was determined by TiO2/Ca-Alg beads. The results also showed that the highest BR18 decolorization levels were 98.4% at 10 g/L loading and 25 mg/L initial dye concentration for 180 min when ZnO/Ca-Alg beads were used as an entrapping matrix. However, a maximum decolorization of 87.1% of BR18 was obtained by TiO2/Ca-Alg beads at similar conditions for 180 min. Catalyst reusability was also tested during ten cycles and ZnO/Ca-Alg beads showed good stability compared to TiO2/Ca-Alg beads. Photocatalytic decolorization efficiency of ZnO/Ca-Alg beads was better than TiO2/Ca-Alg beads for both dyes. Using the comet assay for the genotoxic effect induced on Saccharomyces cerevisiae was also evaluated by entrapped ZnO and TiO 2 powders in Ca-Alg beads. Genotoxicity study showed that the proportion of damaged cells and the genetic damage index (GDI) increased after exposed to entrapped beads in the light phase.

Dendritic CdS wrapped with carbon nanotubes with enhanced photocatalytic performance

Development of new and efficient photocatalysts is important for environment pollution solution. In this paper, a novel photocatalyst consisting of CdS dendrites/carbon nanotubes composites (CdS D/CNT) was prepared by a microwave-assisted reaction. X-ray diffraction (XRD), UV–vis diffuse reflectance spectra (DRS), Fourier transform infrared spectra (FTIR), field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) were used to analyze the samples. CdS had a dendritic structure and carbon nanotubes (CNT) were wrapped around them. Formation of CdS D/CNT composites was investigated by the time-dependent experiments. The photocatalytic decolorization efficiency of the nanocomposites was examined by the degradation of methyl orange (MO). Our work shows promise in synthesizing metal sulfide/CNT nanocomposites for catalytic and other applications.

Synthesis, characterization and comparative studies of dual doped ZnO nanoparticles for photocatalytic applications

Pure and dual doped ZnO nanoparticles were synthesized via the wet chemical method. The synthesized samples were characterized by XRD, HR-SEM/EDS, HR-TEM, UV–Vis, PL, FT-IR, and FT-Raman spectral measurements. The prepared ZnO nanoparticles exhibit a hexagonal wurtzite structure and [Ce–La, La–Gd, Gd–Ce] rare earth dual doped ZnO nanoparticles was confirmed from the shift in XRD peaks position, cell parameter and also changes in the peaks intensity. HR-SEM/EDS and HR-TEM show spherical in shape with less agglomeration on the surface of all samples and the images are clearly revealed that the particle size ~ 40 nm (PZ), 14 nm (ZCL3), 16 nm (ZLG3) and 28 nm (ZGC3). UV–Vis spectra show a strong Ultraviolet region absorbance for ZCL3 sample with the low Energy band gap value of 2.81 eV. The presences of the functional group and molecular vibrations are characterized by employing the FT-IR and FT-Raman spectra. From the PL spectra, it was found that the peak position of all samples produces a visible emission. The photocatalytic performance of the synthesized doped nanoparticles found to exhibit better degradation of MB dye under solar irradiation ZCL3 showed an increase in the photo catalytic decolorization efficiency. The bactericidal activity of dual doped ZnO nanoparticles was investigated against Gram-positive and Gram-negative bacteria and compare with standard ampicillin. We observe that ZCL3 sample have excellent antibacterial activity against Gram-negative bacteria (P. mirabilis) and the mean zone of inhibition ~ 20 mm.

Structural, Optical, and Photocatalytic Activities of Ag-Doped and Mn-Doped ZnO Nanoparticles

We report the photocatalytic activities of ZnO, Ag-doped ZnO, and Mn-doped ZnO nanoparticles (NPs). Ag-doped and Mn-doped ZnO samples were synthesized using a coprecipitation method and calcined at 600°C. XRD, SEM, EDX, and UV-vis spectroscopy techniques were employed for characterization of the synthesized samples. The photocatalytic activities of the samples were evaluated by measuring the photocatalytic decolorization of methyl violet with sunlight being the source of energy. XRD patterns of the samples confirmed the wurtzite structure without change which was indicative of the absence of Mn- and Ag-related secondary phases for the doped ZnO. The UV-vis spectra indicated the band gap energy of ZnO, Ag-doped ZnO, and Mn-doped ZnO to be 2.98, 2.80, and 2.64 eV, respectively. Photocatalytic decolorization of methyl violet for the synthesized samples was found to be favorable at a pH of 9.0, catalyst dose of 1 g/L, and initial dye concentration of 4.5 × 10−4 g/L. Mn-doped ZnO and Ag-doped ZnO photocatalytic decolorization efficiency was significantly higher than undoped ZnO. Incorporation of Mn and Ag enhanced the visible-light photocatalytic activity of ZnO; this could be due to the ability of these metals to increase the surface defects of ZnO which in turn shift their optical absorption towards the visible region.

Synthesis of ternary g-C3N4/Bi2MoO6/TiO2 nanotube composite photocatalysts for the decolorization of dyes under visible light and direct sunlight irradiation

Abstract Novel ternary nanocomposite photocatalysts based on g-C3N4/Bi2MoO6/TiO2 nanotube were synthesized using simple solid combustion, hydrothermal and wetness impregnation methods. The structural and morphological properties of the synthesized photocatalysts were systematically characterized using powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy and scanning electron microscopy (SEM). The crystal structure and phase purity of unitary, binary, and ternary photocatalysts were confirmed by XRD analysis. The SEM analysis reveals the tubular morphology of the TiO2 nanotube, and the presence of Ti, C, N, Bi, Mo, O, C, and N in the ternary composites was confirmed by EDX analysis. The photocatalytic decolorization efficiency of the ternary composites was evaluated by monitoring the decolorization of reactive black 5 and methylene blue dyes under visible light and direct sunlight irradiation, and these ternary composites were compared with binary composites and unitary photocatalysts in terms of the decolorization efficiency. After five cycles of adsorption and decolorization reactions, it was confirmed that the ternary composite photocatalysts were highly stable and reusable. From the results, we conclude that ternary composites (g-C3N4/Bi2MoO6/TiO2 nanotube) are efficient photocatalysts for the decolorization of dyes.

Rapid Photocatalytic Decolorization of Methyl Orange under Visible Light Using VS4/Carbon Powder Nanocomposites

Photocatalytic decolorization of the dye compounds represents a promising approach for textile wastewater treatment, and thus, development of new photocatalysts will be of strong interest. Herein, a novel photocatalyst based on transition metal chalcogenides vanadium tetrasulfide (VS4) was prepared via a simple one-step hydrothermal synthesis, and the synthesized VS4/carbon powder nanocomposites exhibited excellent photocatalytic decolorization efficiency under visible light irradiation. A significantly high methyl orange (MO) decolorization rate of 13.4–19.8 mg L–1 h–1 was achieved. Reactive species such as •O2–, h+, and e– generated through this photocatalytic process have played key roles in decolorization with phthalic acid as a product. The optimal catalyst dosage was determined to be 1.0 g L–1. The decolorization rate was enhanced with the increase in initial MO concentration, and an acidic condition favored the degradation. The VS4/carbon powder nanocomposites could maintain the MO decolorization e...

Synthesis and characterization of Pr x Zn1−x Se nanoparticles for photocatalysis of four textile dyes with different molecular structures

Undoped and Pr-doped ZnSe nanoparticles were prepared using a simple hydrothermal method. The structure and morphology of nanoparticles were investigated by X-ray diffraction, scanning electron microscopy, photoelectron spectroscopy, and Brunauer–Emmett–Teller analysis. The photocatalytic activity of undoped and Pr-doped ZnSe nanoparticles under visible light was evaluated in degradation of acid yellow 36, methylene blue, basic yellow 13, and malachite green. Results indicated that the doping of Pr dopant into ZnSe nanoparticles significantly enhanced the photocatalytic activity. The photocatalytic decolorization efficiency of undoped ZnSe and Pr0.03Zn0.97Se nanocatalysts was 26 and 68 % after 180 min of treatment, respectively, for removing acid yellow 36.

Solar photocatalytic decolorization of azo dyes in water and textile wastewater on N-(Cr3+, Fe3+) doped-TiO2 nanoparticle films: optimization of some operational parameters

The photocatalystic decolorization of the mixture of three textile azo dyes, i.e. Reactive Red (RR) 193, RR 198 and RR 239, with N, or Cr3+ or Fe3+doped TiO2 film photocatalysts under solar light irradiation was studied. The effect of different factors, i.e. concentration of dopant, pH of the solution, additive of H2O2 and irradiation source on the photocatalytic decolorization efficiency of the TiO2 film catalysts, was investigated. The optimal doping concentration is 0.2 at.% with N- or Cr3+, with larger than 96% of the decolorizing efficiencies after 4 h irradiation time. The decolorization of the dyes was strongly enhanced by the addition of hydrogen peroxide in the pH of 3.0. Under solar light irradiation in the presence of H2O2, both N-doped and Cr3+-doped TiO2 thin film were also applied to photocatalytically decolorize a textile wastewater sample.

Electro-assisted photocatalytic decolorization of Reactive Navy Blue SP-BR solution by ZnO nanoparticles immobilized on stainless steel anode

In this study, the effect of electrical field on the photocatalytic (PC) decolorization efficiency of Reactive Navy Blue SP-BR solution using commercial ZnO nanoparticles was studied. The electrical field was applied through potential difference (∆V) between the anode and the cathode. ZnO nanoparticles were immobilized on a stainless steel or titanium anode by electrophoretic deposition method. It was found that the electrical field could increase the decolorization efficiency. Decolorization efficiency in the dye solution with the initial concentration of 15 mg L−1 during 90 min was increased in electro-assisted photocatalytic (EAP) process up to 81% compared to 39% in simple PC process. Applying the potential difference of 4 V showed the highest efficiency in Reactive Navy Blue SP-BR decolorization by EAP process. The effect of working electrode material was studied by replacing the stainless steel with titanium while the other parameters were constant. EAP decolorization efficiency in the dye solution with the initial concentration of 15 mg L−1 and titanium anode was 64%.

Photocatalytic decolorization of methylene blue dye by Ag3PO4–AgX (X = Cl−, Br− and I−) under visible light

Three kinds of Ag3PO4–AgX (X=Cl−, Br− and I−) were prepared by the co-precipitation method between AgNO3 and Na2HPO4+KX (X=Cl−, Br− and I−) solutions. Their photocatalytic activities were also investigated by decolorization of a methylene blue solution. Under visible light irradiation, photocatalytic decolorization of the dye using Ag3PO4–AgX as photocatalyst could occur by interaction between a hole in the valence band of the photocatalyst and the methylene blue dye molecules as it cannot detect the emission of 7-hydroxylcoumarin. AgCl and AgBr induce the Ag3PO4 to increase its photocatalytic decolorization efficiency. On the other hand, the compound Ag3PO4–AgI also showed a high adsorption for methylene blue in the dark.

Visible-Light Photocatalysis in Ca0.6Ho0.4MnO3 Films Deposited by RF-Magnetron Sputtering Using Nanosized Powder Compacted Target

A novel immobilized Ca0.6Ho0.4MnO3 photocatalyst has been developed with high photocatalytic activity for Rhodamine 6G (Rh6G) photodegradation under visible light irradiation. The nanocrystalline Ca0.6Ho0.4MnO3 films were successfully deposited by RF-magnetron sputtering on unheated quartz glass substrates using Ca0.6Ho0.4MnO3 powder as sputtering target and its photocatalytic functionalities have been explored. The visible-light-responsive photocatalytic activity of Ca0.6Ho0.4MnO3 films was evaluated by the photodegradation of Rh6G aqueous solutions under visible light irradiation. The reusability of Ca0.6Ho0.4MnO3 films on fresh dye samples was studied, showing an efficient reuse, without decreasing the photocatalytic decolorization efficiency. Furthermore, X-ray diffraction of the reused films did not reveal additional phases indicating high photochemical stability of the films even after reusing them in successive runs. The photocatalytic efficiency of the nanocrystalline Ca0.6Ho0.4MnO3 films was furt...