Photocatalytic Decomposition Of Organic Dyes Research Articles

Evaluation of the Applicability of Modifying CdSe Thin Films by the Addition of Cobalt and Nickel to Enhance the Efficiency of Photocatalytic Decomposition of Organic Dyes

This article presents the results of an assessment of the use of CdSe, NiCdSe, and CoCdSe thin films as a basis for photocatalysts used for the decomposition of the organic dyes rhodamine B, cargo red, and indigo carmine. Interest in this area was determined by the need to solve a number of issues related to increasing the efficiency purifying aqueous media from the negative effects of organic dyes, which cannot be disposed of using traditional methods associated with adsorption or filtration. The use of the electrochemical synthesis method to obtain thin films of a given thickness showed that the addition of nickel or cobalt sulfates to the standard electrolyte solution used to obtain CdSe films results in the formation of CdSe films with a higher degree of structural ordering (the crystallinity degree was more than 50%), as well as a decline in the band gap. When analyzing data on the photocatalytic decomposition of organic dyes, it was found that a change in the structure of the films due to the introduction of nickel and cobalt leads, in the case of the decomposition of the rhodamine B dye, to a more efficient decomposition, and in the case of the cargo red and indigo carmine dyes, not only to their complete decomposition and mineralization, but also to a reduction in the time of photocatalytic reactions (decomposition growth rate). Moreover, an analysis of cyclic tests demonstrated that NiCdSe and CoCdSe films maintain 90% of their photocatalytic decomposition efficiency compared to that achieved during the first decomposition cycle, while CdSe degrades after three consecutive cycles and its efficiency reduces by more than 2.5–3 times.

Rapid fabrication of colloidal crystal films by spin coating using polymeric particles synthesized by dispersion polymerization

Rapid fabrication of colloidal photonic crystals was successfully carried out by spin coating using polymeric beads. To this end, monodisperse polystyrene (PS) nanospheres were synthesized by dispersion polymerization using alcohol as a reaction medium to prepare coating solution. Transmission of visible light at a specific wavelength could be observed, which is measured by transmittance spectra of coating samples. The transmission intensity of light at specific wavelength could be controlled by adjusting rotation speed or the concentration of coating solution, while peak wavelength could be adjusted by the size of PS nanospheres. Inorganic inverse opal like macroporous silica or titania films were fabricated by diffusion of silica or titania nanoparticles through colloidal crystal film, followed by calcination for removal of PS nanospheres. As a demonstrative application of inverse opal films, photocatalytic decomposition of organic dye was performed under UV light illumination by immersing the macroporous titania film in aqueous solution. The rate constant of decomposition reaction could be estimated from transient data of the dye concentration.

Accelerating Photocatalytic Activity by Tailoring Cocatalysts on Polycrystalline Tungsten(VI) Oxide Microplates

AbstractIn this study, the structure–activity relationship of the WO3 photocatalyst and the role of cocatalysts deposited on the WO3 surface were analyzed. Investigation of the phase transformation of WO3 microplates revealed that amorphous WO3 was progressively crystallized into monoclinic WO3 during consecutive thermal treatments. The obtained WO3 microplates were used for the photocatalytic decomposition of organic dyes under simulated solar light irradiation to understand the effect of the crystal structure on the photocatalytic activity. The crystal phase of the WO3 microplates with a monoclinic structure was optimal for the photocatalytic reaction. However, the effects of the crystal phase and the surface area of the WO3 sample were very small, and a deposited metal cocatalyst was essential for achieving photocatalytic activity. The detailed mechanisms and influence of cocatalysts on the WO3 surface were discussed.

Upcycling discarded cellulosic surgical masks into catalytically active freestanding materials

The COVID-19 pandemic outbreak has resulted in the massive fabrication of disposable surgical masks. As the accumulation of discarded face masks represents a booming threat to the environment, here we propose a solution to reuse and upcycle surgical masks according to one of the cornerstones of the circular economy. Specifically, the non-woven cellulosic layer of the masks is used as an environmentally sustainable and highly porous solid support for the controlled deposition of catalytically active metal-oxide nanoparticles. The native cellulosic fibers from the surgical masks are decorated by titanium dioxide (TiO2), iron oxide (FexOy), and cobalt oxide (CoOx) nanoparticles following a simple and scalable approach. The abundant surface –OH groups of cellulose enable the controlled deposition of metal-oxide nanoparticles that are photocatalytically active or shown enzyme-mimetic activities. Importantly, the hydrophilic highly porous character of the cellulosic non-woven offers higher accessibility of the pollutant to the catalytically active surfaces and high retention in its interior. As a result, good catalytic activities with long-term stability and reusability are achieved. Additionally, developed free-standing hybrids avoid undesired media contamination effects originating from the release of nanoscale particles. The upcycling of discarded cellulosic materials, such as the ones of masks, into high-added-value catalytic materials, results an efficient approach to lessen the waste´s hazards of plastics while enhancing their functionality. Interestingly, this procedure can be extended to the upcycling of other systems (cellulosic or not), opening the path to greener manufacturing approaches of catalytic materials.Graphical abstractA novel approach to upcycle discarded cellulosic surgical masks is proposed, providing a solution to reduce the undesired accumulation of discarded face masks originating from the COVID-19 pandemic. The non-woven cellulosic layer formed by fibers is used as solid support for the controlled deposition of catalytically active titanium dioxide (TiO2), iron oxide (FexOy), and cobalt oxide (CoOx) nanoparticles. Cellulosic porous materials are proven useful for the photocatalytic decomposition of organic dyes, while their peroxidase-like activity opens the door to advanced applications such as electrochemical sensors. The upcycling of cellulose nonwoven fabrics into value-added catalytic materials lessens the waste´s hazards of discarded materials while enhancing their functionality.

Photocatalytic Decomposition of Organic Dyes Using a Rotating Cylinder System.

In this study, a rotating cylinder system was used in the photocatalytic decomposition of organic dyes in aqueous medium for water purification. To this end, the titania nanoparticle dispersion was mixed with an organic dye solution under a rotating inner cylinder at controlled speed. The rate constant was adjusted by changing the speed of rotation to determine the optimal circulating velocity. Since nanoparticle dispersion is a secondary contaminant after wastewater treatment, the titania paste was deposited on the inner surface of the stationary outer cylinder to form a photocatalytic film. During repeated batch-mode operation, the deactivation of the deposited film was analyzed by measuring the rate constant as a function of time. Continuous operation was also used to remove organic dye in the water to study factors affecting the removal efficiency of methylene blue. Higher rotating velocity and slow feed rate facilitated the removal of contaminants via desorption of adsorbed dyes with adequate retention time.

Study of defect formation processes under heavy ion irradiation of ZnCo2O4 nanowires

In recent years, particular attention has been paid to the study of the possibility of using ionizing radiation to modify the properties of nanomaterials. The main goal of these studies is to study the processes of evolution of defects formed during the interaction of incident particles with nanostructures, which has a significant difference from the processes of defect formation in bulk materials. In this paper, we consider the effect of heavy ion irradiation with O2+ (28 MeV), Kr15+ (147 MeV) and Xe22+ (225 MeV) heavy ions on the structural and conductive properties of ZnCo2O4 nanowires obtained by electrochemical synthesis. The irradiation fluence was selected taking into account the possibility of simulating the appearance of single point defects and their subsequent evolution (1010 ions/cm2), as well as the effect of overlapping defect regions formed during the passage of ions in the crystal structure (1012 ions/cm2). The study found that at low irradiation fluences for all ions, partial annealing of structural defects due to irradiation was observed. At the same time, the use of Xe22+ heavy ions at low irradiation fluence can significantly change the structural and conductive properties of nanowires, as well as significantly increase the rate of the photocatalytic decomposition of organic dyes. In the case of high irradiation doses, the effects of overlapping defect regions for O2+ and Kr15+ ions lead to an increase in the degree of structural changes; however, for Xe22+ ions, material degradation is observed due to the destruction of crystalline bonds. The presented results will make a significant contribution to the development of the technology of using ionizing radiation to modify the properties of nanomaterials by removing structural distortions and deformations with small radiation doses.

Fabrication of Silica Microspheres Containing TiO₂ or Aluminum Zinc Oxide Nanoparticles via Self-Assembly: Application in Water Purification.

In this study, silica micro-particles containing titania (TiO₂) or aluminum zinc oxide (AZO) nanopar-ticles were synthesized using emulsion droplets as micro-reactors, for water purification application via photocatalytic decomposition of organic dyes. Towards this end, aqueous silicic acid solution has been emulsified with aqueous dispersion of TiO₂ or AZO nanoparticles in a continuous oil phase to form tiny droplets, followed by subsequent self-assembly of the droplets via evaporation. The resulting composite microparticles were controlled to obtain a spherical or porous morphology by adjusting the concentration of the nanoparticle dispersion. As a demonstrative application, the resulting composite micro-particles have been used as photocatalysts for the removal of methylene blue under UV irradiation. In the case of silica microparticles containing AZO nanoparticles, the adsorption of organic pollutants combined with photocatalytic decomposition was found to be effective, and trace amounts of the pollutant remained after the removal process.

In situ growth of four MOF/LZH composites on layered zinc hydroxide and their photocatalytic performance in decomposition of organic dyes

Four new MOF/layered zinc hydroxide composites suitable for photocatalytic decomposition of organic dyes were prepared via an in situ growth on layered zinc hydroxide according to the solvothermal procedure and characterized by SEM, XRD, IR spectroscopy, and N2-adsorption/desorption. All the selected pollutant dyes (methyl orange, congo red, brilliant green, sunset yellow, and amaranth) underwent a very efficient photodegradation by MOF/LZH-6 composite upon the UV irradiation (λ = 365 nm) via their oxidation by OH radicals and super oxide anion radical species.

NANOCOMPOSITES BASED ON TIO2-SNO2: INFLUENCE OF ACID-BASED AND STRUCTURAL-ADSORPTION PROPERTIES ON THE PHOTOCATALYTIC ACTIVITY

Background. TiO2-SnO2 nanocomposites receive a lot of attention due to their efficient application in heterogeneous photocatalysis. Coupling TiO2 with SnO2 contributes to the suppression of charge carriers’ recombination and enhances photocatalytic performance of the material. Although considerable research on TiO2-SnO2 system has been conducted, there is still a great uncertainty about the most efficient ways of its synthesis, effective synthesis conditions and the most appropriate reagents.Objective. The purpose of the paper is comparison of two synthesis methods (hydrolytic and hydrothermal) and different precursors to obtain TiO2-SnO2 composites; assessment of the influence of different factors on the final properties of photocatalysts.Methods. Synthesis of TiO2-SnO2 nanocomposites allowed studying the effect of SnO2 content on acid-base and structural-adsorption properties that eventually determine photocatalytic performance. Photocatalytic decomposition of organic dyes of various types (methylene blue and Congo red) was used to evaluate photoactivity of materials.Results. Both synthesis methods allowed obtaining of TiO2 and TiO2-SnO2 nanocomposites with crystallite size of 3–24 nm. Hydrolytic synthesis using TiCl4 resulted in pure rutile TiO2, while hydrothermal synthesis using TTIP resulted in pure anatase TiO2. Addition of SnO2 enhanced photocatalytic activity of the samples obtained by hydrothermal method – a sample with 1% SnO2 exhibited photocatalytic activity 30% higher than pure TiO2 sample.Conclusions. Samples obtained by hydrothermal method have both acidic and basic Brønsted sites and are universal sorbents and photocatalysts that remove cationic and anionic dyes. Composites obtained by hydrolytic method contain only basic Brønsted sites and are therefore active for cationic dyes. Surface properties of materials play a crucial role that ultimately determines photocatalytic activity of the materials.

Interaction of conducting polymers, polyaniline and polypyrrole, with organic dyes: polymer morphology control, dye adsorption and photocatalytic decomposition

Conducting polymers, such as polyaniline and polypyrrole, have frequently been discussed in the literature due to ease of preparation and high application potential. These polymers have been observed to interact with organic dyes because of the similarity in the conjugated molecular structure of both moieties. The interaction manifests itself in three fundamental directions that have been so far treated separately. The first is represented by the conductivity enhancement and morphology control when using organic dyes as templates in polypyrrole preparation. The adsorption of dyes on conducting polymers is the second field oriented at the water pollution treatment. Finally, the photocatalytic decomposition of organic dyes aims at the similar environmental target. The last two applications do not require the presence of conductivity which, on the other hand, is a key parameter of conducting polymers. The future design of advanced adsorbents, however, has to exploit both the conductivity and electroactivity in the control of pollutant adsorption or degradation. For this reason, all these interactions and their practical impact are considered in the present review.

Two-dimensional CuO-ZnO nanohybrids with enhanced photocatalytic performance for removal of pollutants

Two dimensional (2D) CuO-ZnO hybrid nanostructures were prepared by using a simple chemical approach and thoroughly investigated by FESEM, X-ray photoelectron spectroscopy, HRTEM, UV–Vis absorption spectroscopy and X-ray diffraction. The photocatalytic decomposition of organic dyes was evaluated using the prepared 2D CuO-ZnO hybrid nanostructures as photocatalysts under sunlight irradiation. Photocatalytic degradation assisted by 2D CuO-ZnO nanohybrids showed remarkably improved efficiency than pristine nanosheets of CuO and completely decolorized MB and MO dyes in just 20 min. Photocatalytic degradation of toxic 4-nitrophenol (4-NP) was also investigated in the presence of prepared nanostructures and 2D CuO-ZnO nanohybrids illustrated better activity over pristine CuO nanosheets. The observed superior photocatalytic performance of 2D CuO-ZnO nanohybrids is ascribed to the inhibited charge carrier recombination and improved light utilization because of formation of p-n nanoheterojunctions of CuO and ZnO. A possible mechanism and role of radicals participating in photocatalytic degradation of dyes were also proposed.

RETRACTED: The phenomena and mechanism for the enhanced adsorption and photocatalytic decomposition of organic dyes with Ag3PO4/graphene oxide aerogel composites

Abstract Ag3PO4/graphene oxide aerogel composites were fabricated by a hydrothermal method. The structure of Ag3PO4 and graphene oxide aerogel was investigated by XRD and Raman spectrum. The specific surface area of Ag3PO4, graphene oxide aerogel, and Ag3PO4/graphene oxide aerogel composites was investigated by the BET method. The adsorption and photocatalytic properties of Ag3PO4/graphene oxide aerogel composites were studied in Methylene Blue solution. The results showed that the existence of graphene oxide aerogel among Ag3PO4 could increase the specific surface area, adsorption performance, and photocatalytic performance of the composites. A higher percentage of graphene oxide aerogel resulted in higher adsorption capacity of Ag3PO4/graphene oxide aerogel composites, while an optimum percentage of graphene oxide aerogel was required for the maximum photocatalytic performance of the composites.

Selectively Photocatalytic Activity of an Open-Framework Chalcogenide Built from Corner-Sharing T4 Supertetrahedral Clusters.

The photocatalysis process with high selectivity is a very important research forefront for the semiconductor photocatalytic decomposition of organic pollutants. However, the rational design of efficient photocatalysts with high selectivity is still a challenge. Here, we present an open-framework chalcogenide (Heta)8[In14Sn2Zn4Se33] (Heta = ethanolamine-H+) (compound 1) constructed from T4 supertetrahedral clusters [In14Sn2Zn4Se35]12- with visible-light-driven selectively photocatalytic degradation activity. Single-crystal XRD analysis shows that compound 1 crystallizes in I41/acd (no. 142) space group, with a = b = 24.3462(2) Å, c = 45.0062(9) Å, V = 26676.9(7) Å3, and Z = 8. Under visible-light irradiation, the selectively photocatalytic activities of 1 were evaluated by photodegradation of two kinds of cationic dye molecules, i.e., methylene blue (MB) and rhodamine B (RhB), against two anionic dyes, methyl orange (MO) and Kermes red (KR), with different sizes. We show that the adsorption capability and charge-matching between organic dyes and the supertetrahedral cluster together with a suitable band structure make it an excellent and selective photocatalyst. This is the first example of an open-framework chalcogenide based on supertetrahedral T4 for the selectively semiconductor photocatalytic decomposition of organic dyes.

Localized Surface Plasmon Resonance Induced Band Gap Regulation Governing the Excellent Photocatalytic Performance of Ag/g-C₃N₄ Heterostructure.

It is an efficient mode to optimize photocatalytic performance of semiconductors by the localized surface plasmon resonance (LSPR) effect through constructing composites with noble metal nanoparticles, nevertheless, the understanding for the essential mechanism, especially the LSPR effect on band gap engineering or free radicals, is not clear. Herein, Ag nanoparticles (Ag NPs) were decorated on popular used semiconductors, graphitic carbon nitride (g-C₃N₄), through a microemulsion route. As expected, Ag/g-C₃N₄ hybrid materials demonstrated outstanding photocatalytic decomposition of organic dyes, including methyl orange, phenol and rhodamine B, in which the photocatalytic efficiency of the composite with the optimal ratio of Ag content was 3.37 times higher than that of pristine sample. The mechanism for the better photocatalytic action was attributed to the localized surface plasmon resonance (LSPR) effect, narrow band gap and low valance band position originated from Ag NPs, which resulted in superior visible-light adsorption and the formation of _OH with strong oxidation. As well, because of the synergy between Ag NPs and g-C₃N₄, faster separation of the photogenerated charges and efficiently utilization of the ·OH and ·O-₂ generated from hole and electron are realized simultaneously. Ultimately, our results offer a extremely understanding of superior photocatalytic property caused by the LSPR effect.

PCBM nanoparticles as visible-light-driven photocatalysts for photocatalytic decomposition of organic dyes

Abstract

Enhanced visible-light photocatalytic decomposition of organic dye over CdSe/Al2TiO5 heterojunction photocatalysts

Heterojunction with nano-level interfacial contact has an advantage in improving the transfer capacity of photongenerated carriers. In consequence, a heterojunction composite with nano-level interfacial contact was developed by establishing CdSe/Al2TiO5 heterojunction composites. The heterojunction composite was established by combining Al2TiO5 and CdSe nanocrystals. They provided superior nano-level interfacial contact. The photocatalytic activity of heterojunction composites were illustrated to be significantly improved compared to that of pure Al2TiO5 and CdSe nanocrystals. Moreover, the photocurrent intensity of heterojunction composites displays a several times enhancement, implying the promotion of photocatalytic activity was owned to the nano-level interfacial contact with ideal photogenerated electron-hole pairs transfer behavior.

Oriented ZnO nanostructures and their application in photocatalysis

We report a chemical bath deposition approach for the preparation of large arrays of oriented ZnO nanostructures by activated substrate processes, and precipitated ZnO nanorods by passive occupation of the crystal surface. Photoluminescence dynamics showed that various visible emission characteristics associated with defects such as oxygen vacancy, zinc interstitial or their complexes. In addition, the precipitated ZnO nanorods exhibited excellent performance in the adsorption and photocatalytic decomposition of organic dyes, achieving 95% photodegradation of Rhodamine 6B. Moreover, oxygen defects function as trap sites with strong adsorption abilities towards organic dyes and showed high performance in the photocatalytic degradation of the dye molecules.

Preparation and Performance of TiO2-ZnO/CNT Hetero-Nanostructures Applied to Photodegradation of Organic Dye

Water pollution by organic compounds is one of the major challenges faced by industries that use dyeing processes. Thus, some methods were developed for degrading dyes in wastewaters, including heterogeneous photocatalysis by semiconductor oxides. However, these oxides have limited photocatalytic activity due to the fast recombination of photogenerated electron-hole pairs. The aim of this study is the use of a carbon nanotube (CNT) and TiO2-ZnO oxide junction from modified sol-gel method to promote the degradation of organic dye through the photocatalytic activity of these nanocomposites. TiO2-ZnO/CNT nanocomposites were studied by X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscope (SEM) and photocatalytic decomposition of organic dyes. The results of photocatalysis show up to 60% the efficiency of the samples in the removal of dye.

Assembly of three new POM-based Ag(I) coordination polymers with antibacterial and photocatalytic properties

Three new silver coordination polymers, namely, {Ag3(bpy)6[PW12O40]} (1), {Ag5(H2biim)2(Hbiim-NO2)2[PW12O40]} (2), {Ag7(pytz)4[PW12O40]} (3) (bpy=2,2′-bipyridine, H2biim=2,2′-biimidazole, pytz=4-(1H-tetrazol-5-yl)pyridine), have been synthesized under hydrothermal condition. Compound 1 shows a 3D supramolecular framework based on 0D moieties. Compound 2 exhibits an attractive 2D biologic screw axis. Compound 3 displays a 3D structure, which consists of Ag(I)···π interactions, π···π stacking and weak Ag···Ag interactions. It is noteworthy that nitration happens to compound 2 during the hydrothermal condition, which is quite rare. Through contrasting the antibacterial activities of gram negative and gram positive bacteria, we find compounds 1–3 have better antibacterial property in gram negative bacteria than gram positive bacteria. In addition, compounds 1–3 also exhibit efficiency of photocatalytic decomposition of organic dyes. Those compounds may be used as potential multifunctional materials in wastewater treatment, because they not only can kill bacteria but also degrade organic pollutants.

Correlation between palladium chemical state and photocatalytic performance of TiO2–Pd based nanoparticles

Photocatalytic processes can be used to illustrate both solar energy conversion and environmental friendly applications. In this study, we synthesize several titanium dioxide–palladium (TiO2–Pd) based catalysts by wet impregnation method plus hydrogen-thermal reduction process in order to develop high-effective photocatalysts that can be easily produced even in industrial quantities. Moreover, we examine the effects of hydrogen-thermal reduction process on the photocatalytic performance of TiO2–Pd based catalysts. From X-ray photoelectron spectroscopy analysis, increasing the hydrogen reduction process time results in the decreasing of palladium ion (Pd2+) and palladium oxide (PdO), but it causes the increasing of palladium (Pd) metal. The hydrogen reduction process is helpful for the preparation of TiO2–Pd based catalysts with high photocatalytic decomposition of organic dyes (the apparent reaction rate constant ~0.124min−1 under solar simulator irradiation) and excellent photocatalytic hydrogen production rate (~26,000μmol/g·h under UV-B irradiation). The TiO2–Pd based catalysts prepared in this study exhibit high photocatalytic performance. They are also industrially relevant especially when the low cost of Pd metal is taken into consideration.