Photodegradation Of Rhodamine 6G Research Articles

Porphyrin-Nanocarbon Complexes to Control the Photodegradation of Rhodamine.

Porphyrin-nanocarbon systems were used to generate a photocatalyst for the control of rhodamine B and rhodamine 6G photodegradation. Carboxylic functionalized multi-walled carbon nanotubes (o-MWCNTs) were decorated by two different porphyrin moieties: 5-(4-aminophenyl)-10,15,20-(triphenyl)porphyrin (a-TPP) with an amine linker and 5-(4-carboxyphenyl)-10,15,20-(triphenyl)porphyrin (c-TPP) with a carboxyl linker to the o-MWCNT, respectively, with their photocatalyst performances investigated. The optical properties of the mixed nanocomposite materials were investigated to reveal the intrinsic energy levels and mechanisms of degradation. The charge-transfer states of the o-MWCNTs were directly correlated with the performance of the complexes as well as the affinity of the porphyrin moiety to the o-MWCNT anchor, thus extending our understanding of energy-transfer kinetics in porphyrin-CNT systems. Both a-TPP and c-TPP o-MWCNT complexes offered improved photocatalytic performance for both RhB and Rh6G compared to the reference o-MWCNTs and both porphyrins in isolated form. The photocatalytic performance improved with higher concentration of o-MWCNTs in the complexed sample, indicating the presence of greater numbers of -H/-OH groups necessary to more efficient photodegradation. The large presence of the -H/-OH group in the complexes was expected and was related to the functionalization of the o-MWCNTs needed for high porphyrin attachment. However, the photocatalytic efficiency was affected at higher o-MWCNT concentrations due to the decomposition of the porphyrins and changes to the size of the CNT agglomerates, thus reducing the surface area of the reactant. These findings demonstrate a system that displays solar-based degradation of rhodamine moieties that are on par, or an improvement to, state-of-the-art organic systems.

Interfacial self-assembly of porphyrin-based SURMOF/graphene oxide hybrids with tunable pore size: An approach toward size-selective ambivalent heterogeneous photocatalysts

New photocatalysts were synthesized from graphene oxide (GO) and zinc porphyrins via non-covalent self-assembly in Pickering emulsions. The formation of surface-attached metal organic frameworks (SURMOFs) with different size of mesopores (1.1. and 1.6 nm) was confirmed by X-ray powder diffraction and BET nitrogen absorption methods. The activity of the SURMOF/GO materials in photodegradation of rhodamine 6G (Rh6G) and 1,5-dihydroxynaphtalene (DHN) were studied spectroscopically. The photocatalysts initiate aerobic oxidative photodestruction with k up to 2.3 × 10−1 min−1 through generation of singlet oxygen on porphyrin centers. Under anaerobic conditions, these materials assist photoreduction of the same dyes in the SURMOF micropores. The mechanisms of photodegradation assisted by SURMOF/GO hybrids were confirmed by a combination of MALDI-TOF spectroscopy, Sensor Green and terephthalic acid probing. The size of the SURMOF pores controls the reduction, which occur due to the effective charge separation between porphyrin SURMOFs and GO. The photocatalyst with larger pores can transform both Rh6G and DHN, whereas that one with smaller pores is active only with respect to small DHN molecules. The ability of as-formed SURMOF/GOs to exploit two mechanisms yielding different products of photodestruction provides a basis for creating novel ambivalent photocatalysts for selective transformations of targeted compounds in molecular mixtures.

Bergenia ciliate-Mediated Mixed-Phase Synthesis and Characterization of Silver-Copper Oxide Nanocomposite for Environmental and Biological Applications.

Bergenia ciliate (B. ciliate) leaf extract was used as a reducing and stabilizing agent for the synthesis of silver-copper oxide nanocomposite (Ag-CuO NC). Scanning and transmission electron microscopies (SEM and TEM) were used to examine the structural morphology, and the average particle size was determined to be 47.65 nm. The phase confirmation and crystalline structure were examined through the X-ray diffraction (XRD) technique, where cubic and monoclinic geometries were assigned to Ag and CuO. The energy dispersive X-ray (EDX), Fourier transform infrared (FTIR) and ultra-violet and visible (UV-Visible) spectroscopies were operated to analyse the elemental composition, functional groups and light absorption phenomena of the Ag-CuO NC. Under the full light spectrum, the photodegradation of Rhodamine 6G was recorded, and 99.42 percent of the dye degraded in 80 min. The Agar well diffusion method was followed to perform antibacterial activity against selected pathogens, and the activity was found to increase with increasing concentration of Ag-CuO NC. The ABTS free radical scavenging activity suggests that the activity of Ag-CuO NC is higher than ascorbic acid.

Ultrasonic effect on the photocatalytic degradation of Rhodamine 6G (Rh6G) dye by cotton fabrics loaded with TiO2

The effect of sonication on the photodegradation of Rhodamine 6G (Rh6G, a fluorone dye) using woven cotton fabrics decorated with TiO2 nanoparticles (NPs) has been investigated. TiO2 NPs were synthesized in situ by sol–gel method in the presence of cotton textile and then hydrothermally treated. TiO2-loaded fabrics were treated ultrasonically to test adhesion to- and properties of the NPs on the fabrics. We demonstrate good adhesion and a good stability of the NPs of TiO2. Moreover, sonication substantially improved the distribution on the surfaces and hence enhanced the fabrics catalytic activity. Either under UV or simulated sunlight, ultrasonicated fabrics were found to have a high photocatalytic activity towards Rh6G, used as a model dye. SEM, XPS, UV–Vis and FTIR spectroscopy, as well as ground state diffuse reflectance and laser induced luminescence were used to characterize fabrics/TiO2 samples in terms of topography, surface composition, influence of hydrothermal treatment on photocatalytic activity, stability of TiO2 NPs, electro-optical properties of the modified fabrics, as well as the effect of ultrasonication on the photodegradation of Rh6G. This work paves the way to a larger scale improvement of the photocatalytic performances of TiO2-loaded cotton fabrics by post-sonication.

Synthesis and characterization of zinc stannate nanostructures for the adsorption of chromium (VI) ions and photo-degradation of rhodamine 6G

The zinc stannate nanostructure was synthesized via sol-gel route and its physicochemical, adsorption and photocatalytic properties were studied. The specific surface area (S) was calculated by Brunauer–Emmett–Teller (BET) and Barrett, Joyner and Halenda (BJH) methods using N2 adsorption-desorption. The SBET and SBJH were found to be 105 and 138 m2 g−1 respectively with the average pore size of 2.5 nm. Based on diffraction data, cubic geometry was assigned to the crystallites with average size of 31.74 nm. The morphology of the particles was studied though transmission electron microscopy (TEM) and scanning electron microscopy (SEM) and the average particles size as calculated from TEM was 21.6 nm. The band gap calculated from the diffuse reflectance spectrum was 3.36 eV. The percentage composition and purity were determined by energy dispersive X-ray (EDX), whereas surface functional moieties were detected by Fourier transform infrared (FTIR) spectroscopy. The batch method was used to study the adsorption of Cr(VI) ions by varying, initial electrolyte concentration, pH, and temperature of solution. The parameters extracted from Langmuir and Freundlich models shows that the adsorption process was more feasible at higher temperature and lower pH. The maximum sorption capacity of the adsorbent was found to be 32.81 mg g−1. The 1:1 exchange mechanism was proposed between Cr(VI) and surface protons while the thermodynamic study reveals the endodermic nature of the adsorption process. The photocatalytic performance of the zinc stannate was examined against Rhodamine 6G where 98.17% degradation was achieved in 390 min.

A novel natural sunlight active photocatalyst of CdS/SWCNT/CeO2 heterostructure: In depth mechanistic insights for the catalyst reactivity and dye mineralization

A conventional type II heterostructure based on CdS/SWCNT/CeO2 was successfully prepared via a modified co-precipitation and hydrothermal method. The as-prepared heterostructure was characterized via UV–Vis, Fluorescence, XRD, XPS and TEM. The morphology of the heterostructure showed spherical nanoparticles with a particle size of 5.1 nm for CdS/CeO2 on the SWCNT. These properties were translated into remarkable enhancement in the photodegradation of Rhodamine 6G (R6G) dye as a model pollutant for textile and food stuff industries under natural solar radiation. The photo-experiments showed an enhanced photocatalytic activity of CdS/CeO2 and CdS/SWCNT/CeO2 to be 79.3% and 86.4% respectively which are two-fold much greater than that of bare CeO2 NPs (36.6%). Also, the calculated photonic efficiencies (ζ) were found to be 11.7%, 39% and 54.5% for CeO2, CdS/CeO2 and CdS/SWCNT/CeO2 nanostructures respectively. Total organic carbon (TOC) was used to further estimate the mineralization capability of the heterostructure (94% TOC Removal). Furthermore, the band alignment of CdS/SWCNT/CeO2 heterostructure was determined via Mot-Schottky plots and Valence and Core-Level X-ray Photoelectron Spectroscopy, which provided a deep insight about the photodegradation efficiency. For in-depth understanding what happens during the photodegradation, the detection of reactive oxidative species (ROS) was investigated by the trapping experiments.

One-step synthesis of magnetic-TiO2-nanocomposites with high iron oxide-composing ratio for photocatalysis of rhodamine 6G.

In the study, a facile one-step method for synthesizing magnetic-TiO2-nanophotocatalysts was developed. With the same composing ratio of 0.5 and 0.35 (Fe:Ti, mole:mole), we prepared two types of magnetic-TiO2-nanocomposites as one-step synthesized FexOy-composed TiO2 (FexOy/TiO2-0.5 and FexOy/TiO2-0.35) and two-step synthesized core-shell FexOy@TiO2 (FexOy@TiO2-0.5 and FexOy@TiO2-0.35), and tested their performance in rhodamine 6G (R6G) photodegradation. X-ray diffraction (XRD) analysis showed that FexOy@TiO2-0.5 has the smallest crystallite size (16.8 nm), followed by FexOy@TiO2-0.5 (18.4 nm), FexOy/TiO2-0.35 (21.0 nm) and FexOy/TiO2-0.5 (19.0 nm), and X-ray photoelectron spectroscopy (XPS) suggested the decreasing percentage of Fe3O4 from 52.1% to 36.7%-47.2% after Ti-deposition treatment. The saturated magnetisms followed the order: FexOy@TiO2-0.5 > FexOy@TiO2-0.35 > FexOy/TiO2-0.5 > FexOy/TiO2-0.35. R6G photodegradation followed the first order kinetics and was slightly influenced by pH but significantly affected by initial photocatalyst concentration. FexOy/TiO2-0.35 achieved the highest removal efficiency for R6G (92.5%), followed by FexOy@TiO2-0.35 (88.97%), FexOy@TiO2-0.5 (60.49%) and FexOy/TiO2-0.5 (48.06%). Additionally, all these magnetic-TiO2-nanocomposites had satisfied magnetic recoverability and exhibited laudable reusability after 5-times reuse, even achieving higher R6G removal efficiencies from 97.30% to 98.47%. Our one-step method took only 75 min for nanocomposite synthesis, 90 min less than conventional two-step method, showing its feasibility as a practical method for magnetic-TiO2-nanocomposite synthesis in industrial application.

Novel diatom-FeO x composite as highly active catalyst in photodegradation of Rhodamine-6G

Abstract We report the study of nanoporous silica-iron oxide composite generated from diatom frustules as a highly active catalyst for the photodegradation of the dye Rhodamine-6G. The unique architecture and high surface area of diatoms were utilized to immobilize iron oxide on their surface to form the composite. Photodegradation was carried out under 365-nm radiation and was observed using the absorption spectrum of the dye. The reaction was found to follow pseudo-first-order kinetics. The results were compared with commercially available granular iron oxide. The rate constant K (min−1) for photodegradation by the diatom composite was found to be as high as 0.0584 min−1 for diatom-FeO x composites, which is 52% higher than 0.0273 min−1 for granular FeO x at a dye concentration of 0.02 mm. The unique structural morphology and the synthetic strategy have led to the composites showing superior activity in the degradation of the dye Rhodamine-6G.

Photodegradation of Rhodamine 6G by Amorphous TiO2 Films Grown on Polymethylmethacrylate by Magnetron Sputtering

Titanium dioxide (TiO2) was deposited on polymethylmethacrylate (PMMA) substrates by magnetron sputtering using a Compact Planar Magnetron sputtering device at different flow rate ratios of O2/Ar. The deposited TiO2 on PMMA substrates were characterized using X-ray Diffraction analysis, X-ray Photoelectron Spectroscopy, Fourier Transform Infrared Spectroscopy, UV-Visible Spectroscopy, and Scanning Electron Microscopy (SEM). These techniques confirm the deposition of a chemically stable amorphous TiO2 layer on the PMMA surface. Photocatalytic activity of the amorphous TiO2 layers were tested via photodegradation of Rhodamine 6G (Rh6G) dye solution. The samples were able to degrade 18–27% of the Rh6G solution after the initial 25 minutes of UV irradiation and complete degradation of Rh6G was observed after 7 hours of UV irradiation.

Double-sided plasmonic Au nanoparticles on Cu-doped ZnO/ZnO heterostructures with enhanced photocatalytic activity

We demonstrate the synthesis of heterostructured photocatalysts that the double-sided plasmonic Au nanoparticles have been deposited on the Cu-doped ZnO/ZnO heterostructures by a facile ion sputtering method. The resultant quaternary Cu-doped ZnO/Au/ZnO/Au heterostructures exhibit excellent photocatalytic activity in the photodegradation of rhodamine 6G under 10W UV light irradiation, which is much higher than Cu-doped ZnO/ZnO heterostructures. Moreover, the Cu-doped ZnO/Au/ZnO/Au heterostructures can be reused for degradation of R6G during a five-cycle experiment without significant decrease in the photocatalytic efficiency.

Calcium-containing materials as alternative catalysts in advanced oxidation process

In this work, four calcium-containing materials (calcium hydroxide, commercial hydrated lime, calcium oxide and calcium carbonate) were evaluated as catalysts in the photodegradation of Rhodamine 6G (Rh6G) under UV radiation. The effect of catalyst concentration, reaction time and pH were evaluated. Materials were characterized by X-ray powder diffraction, thermogravimetric analysis, Scanning Electron Microscopy and Diffuse Reflectance Spectroscopy. The X-ray powder patterns showed that Ca(OH)2, CaO and CaCO3 samples presented pure crystalline phases while commercial hydrated lime consisted of a mixture of calcite and calcium hydroxide. Materials evaluation indicated that among the calcium-containing catalysts Ca(OH)2 was the most active material showing a degradation and mineralization percentages of 50 and 61, respectively. Since Ca(OH)2 band gap value was 5.69eV, characteristic of an insulator material, the photocatalytic activity was attributed to an indirect dye sensitization.

TiO2-chabazite semiconductor composites for photocatalytic degradation of rhodamine under sunlight irradiation

In this work, natural zeolite chabazite was employed to obtain semiconductor composites by mixing with commercial and sol-gel processed, anatase phase TiO2 powders. The TiO2-chabazite semiconductor composites were prepared by mixing the powders and subsequently milling at high-energy or stirring in aqueous solution at acid pH. The crystalline and morphological characteristics of the semiconductor composites were analyzed by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The results show the polycrystalline character of the composites with good synergy between the phases. The different semiconductor composites were also tested and compared as photocatalysts in the photodegradation of rhodamine 6G in aqueous solutions under sulight irradiation. The photocatalytic properties of the semiconductor composites depend mainly on the quality of the TiO2 semiconductor, with the commercial one yielding better photocatalysts. The adsorption properties of chabazite aid the photocatalysis process by accumulating rhodamine molecules near TiO2 and allowing deeper penetration of sunlight in the solution. Both high-energy milled and acid route processed, commercial TiO2–based composites produced better results for the rhodamine photodegradation under sunlight irradiation. The percent reduction of rhodamine in solution after 90min produced by these semiconductor composites was 97.9 and 96.8%, respectively.

Rapid Synthesis of Mesoporous, Nano‐Sized MgCr2O4 and Its Catalytic Properties

Monophasic MgCr2O4 has been synthesized by calcining the gel formed by the addition of epoxide to an ethanolic solution containing MgCl2·6H2O and CrCl3·6H2O. The sample has been characterized by a variety of analytical techniques including powder X‐ray diffraction (PXRD), FT‐IR, Raman, UV–Visible spectroscopy, transmission electron microscopy, and magnetic measurements at room temperature. Calcining the xerogel at 500°C and 700°C for 2 h yielded MgCr2O4 (yield of almost 61% by weight). BET surface area of 33.95 m2/g with an average pore diameter of 28.45 nm was obtained for the sample after calcination at 700°C. Square facets of the cubic spinel structure were observed in TEM images with an average crystallite diameter of 18 nm. HR‐TEM experiments and SAED measurements confirmed the spinel structure and negated the presence of other phases. The presence of MO4 tetrahedral and MO6 octahedral units in MgCr2O4 has also been evidenced from FTIR and Raman spectra. The sample showed paramagnetic behavior at room temperature with μeff of 3.54 B.M suggesting the presence of Cr in III oxidation state. Its use as an efficient catalyst for the oxidative degradation of Xylenol Orange (XO) and the photo degradation of Rhodamine‐6G (Rh‐6G) dyes have been demonstrated as these dye molecules are environmental pollutants.

Photocatalytic behaviour of zinc tetraamino phthalocyanine-silver nanoparticles immobilized on chitosan beads

Photocatalytic degradation of Rhodamine 6G using unconjugated zinc tetraamino phthalocyanine (ZnTAPc) or when conjugated to Ag nanoparticles (ZnTAPc–AgNPs) is reported. Upon conjugating ZnTAPc to silver nanoparticles, the singlet oxygen production of the phthalocyanine was slightly increased. ZnTAPc and ZnTAPc–AgNPs were immobilized onto chitosan beads for ease of recovery after photocatalysis. Chitosan beads were characterized by FTIR, XRD and TGA. The photodegradation of Rhodamine 6G was used to evaluate the efficiency of the immobilized photocatalysts. In the presence of AgNPs, the photodegradation of Rhodamine 6G was enhanced. The apparent rates (k) were found to be 8.51×10−8 and 1.61×10−7molL−1min−1 for chitosan supported ZnTAPc or ZnTAPc–AgNPs, respectively. The observation of good photocatalytic activity of the ZnTAPc when immobilized on chitosan proves the uncompromised efficiency of the photocatalysts even when confined in beads, showing great potential for the functionalized beads as heterogeneous catalysts.

Photodegradation of rhodamine 6G in aqueous solution via SrCrO4 and TiO2 nano-sphere mixed oxides

Nano-sphere TiO2 and SrCrO4 (up to 5 mol%) mixed oxides were synthesized by co-precipita- tion method and investigated as catalyst in the photodegradation of rhodamine 6G (Rh6G) in aqueous solution. SrCrO4/TiO2 oxides were characterized by techniques of powdered X-ray diffraction, EDAX, BET, TEM, SEM and ESR analysis. The photocatalytic activities of degradation of dyes were measured by UV-VIS absorption spectroscopy. The results showed that the mixed oxides of TiO2 with 1 mole % of SrCrO4 (SCT1) exhibit a photocatalytic acti- vity 3 times higher than that of P25TiO2 for oxidation of various dyes (Rh6G, TB, MO and BG) under UV light irradiation (l>280nm). Among all these dyes the photodegradation of Rh6G was faster compared to other dyes. The average crystallite sizes, spherical particle sizes and grain sizes of SCT1 were found to be ~15nm, 90±5nm and 100±5nm, respectively. The EPR spectrum of SCT1 indicated that the ejection of electron helped to degrade the dye molecule faster.

Morphologies of Nanostuctured ZnO Prepared by Matrix-Assisted Method and its Effects on Photocatalytic Activity

Zinc oxide nanoparticles have been successfully synthesized by matrix-assisted method using activated carbon as a matrix and zinc nitrate and zinc acetate as ZnO precursors. Different weight percentages (10-40 wt %) of Zn precursor were loaded onto activated carbon and calcined in air at 500 and 600 oC, producing highly crystallined ZnO particles with a wurtzite structure. Nanospherical ZnO and a mixture of nanosphere and nanorod ZnO were produced from zinc nitrate and zinc acetate, respectively. The efficiency study of the synthesized ZnO in the photodegradation of rhodamine 6G indicated that ZnO produced from zinc acetate is more effective than that from zinc nitrate, possibly due to the differences in the morphology of the synthesized ZnO.

Structural refinement and photocatalytic activity of Fe-doped anatase TiO2 nanoparticles

Colloidal iron-doped (0.0–3.0mol%) TiO2 nanoparticles have been synthesized using sol–gel method and characterized by thermogravimetric analysis, powder XRD, IR spectroscopy, Raman spectroscopy, and transmission electron microscopy (TEM). The characteristic features of nanocrystalline TiO2 in tetragonal anatase phase were confirmed by powder XRD studies with Rietveld refinement. Rietveld refinement data gave 2.59, 3.21 value of RB for pure TiO2 and 3.0mol% Fe:TiO2 nanoparticles, respectively. Raman bands at 639cm−1, 517cm−1, and 395cm−1 further confirmed the pure anatase phase in all samples. TEM pictures revealed the non-spherical nanoparticles having sizes in between 7 and 14nm. Surface area and pore volume for the samples were in the range of 150–87m2/g and 0.35–0.21cm3/g, respectively. The magnetic and optical properties of the nanoparticles were investigated by using SQUID magnetometer and UV–vis spectroscopy. The undoped titania nanoparticles were diamagnetic; whereas all doped titania samples were paramagnetic. The optical band gap of titania nanoparticles were found to decrease with the increase in iron content in host lattice. The photocatalytic performance of the iron-doped TiO2 nanoparticles for the conversions of p-nitrobenzaldehyde to p-nitrobenzoic acid as well as photodegradation of Rhodamine 6G was also investigated.

Photoelectrochemical and Photocatalytic Properties of TiO2, WO3 and WO3-TiO2 Porous Films in the Photodegradation of Rhodamine 6G in Aqueous Solution

Photoelectrochemical and Photocatalytic Properties of TiO₂, WO₃ and WO₃-TiO₂ Porous Films in the Photodegradation of Rhodamine 6G in Aqueous Solution

Stabilisation of mesoporous TiO 2 by different bases influencing the photocatalytic activity

Mesoporous titania was synthesised following the Evaporation-Induced Self-Assembly method. The structures had to be thermally stabilised in order to possess photocatalytic activity, since the photocatalytic active anatase phase needs to be accessible. The photocatalytic activity of the materials was tested by the photodegradation of rhodamine 6G. The stabilisation of the mesoporous structure is done by a post-modification in basic medium. A comparison was made between NH 4OH and NaOH as post-modification base. The results show that post-modification with NaOH is better than NH 4OH and leads also to a better photocatalyst.

Photocatalysis by Composite Particles Containing Inert Domains

AbstractTitanium dioxide is a well‐known photocatalyst for the treatment of air and water. The use of structures comprised of photocatalytic sites and high capacity adsorption sites may improve the TiO2 photoefficiency, in cases where the contaminnants do not adsorb well onto the photocatalyst. In this work, composite particles composed of activated carbon, partially coated with sol‐gel‐made titanium dioxide, were prepared and characterized. It was found that chelating the titanium tetraiso‐propoxide, used as a precursor, with acetylacetone is crucial for obtaining reasonable loading (up to 12–15% in weight). High content of water or humidity tends to form thick films that might bridge over the pores of the activated carbon, thus reducing the available surface area.The photocatalytic activity of the composite particles was tested by following the rate of production of carbon dioxide during the photodegradation of Rhodamine 6G in an aqueous solution. Enhanced mineralization rates relative to sol‐gel‐made titanium dioxide particles (by ˜30%) were observed. This enhancement is attributed to the adsorption of the contaminants in the vicinity of the photoactive sites. It was further found that the composite particles produced relatively less of the toxic by‐product carbon monoxide, than sol‐gel‐made titanium dioxide or the commercially available Degussa P25. The reason for this effect is yet to be determined.