Facile synthesis of ZnO nanoparticles for the photocatalytic degradation of methylene blue

Journal of Sol-Gel Science and Technology - ZnO nanoparticle photocatalysts with a grain size range of 20–100?nm were prepared via a simple sol–gel method and characterized by...     

Biosynthesis of silver nanoparticles and their role in photocatalytic degradation of methylene blue dye

Research on Chemical Intermediates - Nowadays, synthesis of nanoparticles, particularly silver nanoparticles (Ag-NPs), has become a research priority due to their wide application in medicine and...     

Electrospun Pd-doped ZnO nanofibers for enhanced photocatalytic degradation of methylene blue

Pure and Pd-doped ZnO nanofibers were synthesized via an electrospinning technique, in which polyvinylpyrrolidone was used as the fiber template, zinc acetate/palladium chloride as the precursors, and a mixture of ethanol/acid acetate/water at ratio of 8:5:2 (v/v/v) as the co-solvent. The electrospun fibers were calcined at 600 °C in air for 2 h and characterized by various methods. The photocatalytic activity of the pure and Pd-doped ZnO nanofibers was studied through the photodegradation of methylene blue. Comparing to the pure ZnO nanofibers, the Pd-doped catalysts showed a much enhanced photodegradation efficiency. The possible mechanism was also discussed.     

Facile solvothermal synthesis of highly active monoclinic scheelite BiVO4 for photocatalytic degradation of methylene blue under white LED light irradiation

In this study, BiVO₄ was successfully synthesized via the solvothermal process using a solvent mixture of ethylene glycol and water under different synthesis conditions of temperature and pH. Physicochemical properties such as crystal phase, morphology, and optical absorption of the as-synthesized BiVO₄ samples were characterized by X-ray diffraction (XRD), Raman spectra, field emission scanning electron microscopy (FE-SEM), and ultraviolet–visible diffraction reflection spectroscopy (UV–vis DRS). The XRD analysis showed that different synthesis conditions of temperature and pH significantly affected the growth of monoclinic BiVO₄ crystals oriented along (0 4 0) facets. Form SEM results, the synthesis conditions, including pH and temperature, have a great effect on the morphology of monoclinic structured BiVO₄. As the pH value increases in the range of 0–9 and temperature increases from 80 °C to 180 °C, the morphology of BiVO₄ changed from peanut-, rod-, and leaf-like shapes. The photocatalytic activities of as-synthesized BiVO₄ photocatalysts were evaluated by the photodegradation of methylene blue (MB) dye under irradiation of white LED light. We have found that by using appropriate synthesis conditions (the synthesis temperature of 140 °C and the synthesis pH of 7) the BiVO₄ exhibited high photocatalytic efficiency for MB degradation (about 82.30% after 180 min of irradiation). This result is due to the development of the BiVO₄ crystals oriented along (0 4 0) facets with an increase in the intensity ratio of I_(0 4 0)/I_(1 2 1). The growth of BiVO₄ crystals oriented along (0 4 0) facets may be beneficial to enhance the photocatalytic activity of monoclinic scheelite BiVO₄.     

Facile synthesis and characterization of Fe2O3 nanoparticles using L-lysine and L-serine for efficient photocatalytic degradation of methylene blue dye

In this work, Fe₂O₃ nanoparticles, abbreviated as OL and OS, were facilely synthesized by the combustion procedure using L-lysine and L-serine as organic fuels, respectively. Also, the OL and OS samples were identified using different instruments such as Raman spectrometer, FT-IR spectrophotometer, UV–Vis spectrophotometer, XRD, HR-TEM, BET surface area, and FE-SEM. The XRD confirmed that the mean grain size of OL and OS samples is 42.23 and 33.16 nm, respectively. The HR-TEM images confirmed that irregular, hexagonal, and spherical shapes, have an average diameter of 39.13 and 34.28 nm, were observed in the OL and OS samples, respectively. The BET surface area of the OL and OS samples is 16.20 and 28.34 m²/g, respectively. Additionally, the OL and OS samples were accomplished for the photocatalytic degradation of methylene blue dye in the absence and presence of hydrogen peroxide. The % degradation of 45 mL of 25 mg/L of methylene blue dye in the case of using OL and OS samples in the absence of hydrogen peroxide is 55.23 and 63.64 % after 120 min, respectively. Also, in the presence of hydrogen peroxide, the % degradation in the case of using OL and OS samples is 100 % after 35 and 25 min, respectively.     

Shape-controlled fabrication of porous ZnO architectures and their photocatalytic properties

In this paper, we report a simple two-step approach to prepare porous octahedron- and rod-shaped ZnO architectures. The morphology of porous ZnO particles can be conveniently tuned by controlling morphologies of the ZnC₂O₄·2H₂O precursor. SEM and TEM characterization results indicate that these porous ZnO architectures are built up by numerous ZnO primary nanoparticles with random attachment. Based on thermogravimetry analysis, we believe that the release of water vapor, CO and CO₂ leads to the formation of high-density pores in shape-controlled particles during the calcination process. Further experimental results indicate that as-prepared porous ZnO particles exhibit good photocatalytic activity due to large surface area.     

Photocatalytic synthesis of ZnO/Ag nanostructure sensitized by methylene blue

The possibility of photochemical synthesis of ZnO/Ag nanoheterostructures by the action of visible light absorbed by methylene blue as sensitizer was established. It was shown that sensitization of the ZnO nanoparticles results from electron transfer from the singlet-excited molecules of the dye to the conduction band of the ZnO nanoparticles. A scheme for the mechanism of the photoprocesses that occur is proposed.__________Translated from Teoreticheskaya i Éksperimentalnaya Khimiya, Vol. 41, No. 1, pp. 12–16, January–February, 2005.     

Hierarchical Ag/ZnO micro/nanostructure: Green synthesis and enhanced photocatalytic performance

Ag/ZnO metal-semiconductor nanocomposites with hierarchical micro/nanostructure have been prepared by the hydrothermal synthesis in the presence of bovine serum albumin (BSA). The results suggest that this biomolecule-assisted hydrothermal method is an efficient route for the fabrication of Ag/ZnO nanocomposites by using BSA both a shape controller and a reducing agent of Ag⁺ ions. Moreover, Ag nanoparticles on the ZnO act as electron sinks, improving the separation of photogenerated electrons and holes, increasing the surface hydroxyl contents of ZnO, facilitating trapping the photoinduced electrons and holes to form more active hydroxyl radicals, and thus, enhancing the photocatalytic efficiency of ZnO. This is a good example for the organic combination of green chemistry and functional materials.     

Chlorophyll-sensitized phenolic resins for the photocatalytic degradation of methylene blue and synthetic blue wastewater

Journal of Sol-Gel Science and Technology - A novel method was proposed to incorporate chlorophyll molecules into the phenolic resins for the photocatalytic degradation of methylene blue and...     

三维Cu-MOF对亚甲蓝的吸附和光催化降解及其机理

本文报道了[Cu₃(ppda)₃(tib)₂(H₂O)₄]·6H₂O (Cu-MOF)的合成、结构、吸附和光催化降解性能。在Cu-MOF中，1，4-苯二乙酸(H₂ppda)和1，3，5-三(1-咪唑基)苯(tib)配体交替连接Cu离子形成二维层，层与层之间通过trans-ppda^2-相互穿插形成稳定的三维结构。Cu-MOF对亚甲蓝(MB)的催化效率为97%，最高反应速率常数为0.019 7 min^-1。光催化降解机理：在光的激发下，催化剂表面的光生电子和空穴对发生分离，并与O₂、H₂O、H₂O₂反应生成活性物质，将染料降解为CO₂和H₂O。在MB溶液中加入NaCl (200 g·L^-1)后，Cu-MOF的吸附量有所提升(87.23 mg·g^-1)，准二级动力学模型和Langmuir等温线模型的实验数据拟合程度较好，该吸附的主要过程为单层化学吸附。     

三维Cu-MOF对亚甲蓝的吸附和光催化降解及其机理

本文报道了[Cu₃(ppda)₃(tib)₂(H₂O)₄]·6H₂O(Cu-MOF)的合成、结构、吸附和光催化降解性能。在Cu-MOF中,1,4-苯二乙酸(H₂ppda)和1,3,5-三(1-咪唑基)苯(tib)配体交替连接Cu离子形成二维层,层与层之间通过trans-ppda^2-相互穿插形成稳定的三维结构。Cu-MOF对亚甲蓝(MB)的催化效率为97%,最高反应速率常数为0.019 7 min^-1。光催化降解机理：在光的激发下,催化剂表面的光生电子和空穴对发生分离,并与O₂、H₂O、H₂O₂反应生成活性物质,将染料降解为CO₂和H₂O。在MB溶液中加入NaCl(200 g·L^-1)后,Cu-MOF的吸附量有所提升(87.23 mg·g     

Ultrasonic assisted synthesis of ZnO nanoflakes and photocatalytic activity evaluation for the degradation of methyl orange

In the present investigation, ZnO nanoflakes was prepared via sonochemical synthesis route. Effect of ultrasonic treatment time was studied based on structural, morphological and optical properties. X-ray diffraction (XRD) reveals the formation of wurtzite hexagonal crystalline structure of ZnO nanoflakes. Ultrasonic treatments affected the crystallite size and the density of dislocation, which is due to increased nucleation and growth rates of nanoflakes. The samples synthesized at 40–50 min ultrasonic treatment showed a strong absorption band at 605 and 650 (cm^?1) versus other treatments, which is an indication of 2D nanostructure (nanoflakes). FE-SEM analysis further confirms the formation of 2D nanostructures of the ZnO. The composition and purity was confirmed by the energy dispersive X-ray (EDX) analysis, which displays the occurrence of Zn and O elements in the sample. Photocatalytic activity (PCA) of ZnO nanoflakes was studied for methyl orange (MO) dye degradation under UV light exposure and up to 93.13 % dye degradation is achieved within 90 min. Effect of various parameters (dye concentration, mass of photocatalytic material) and kinetic study was also performed. Results revealed that the ultrasonic treatment affected the optical and photocatalytic properties of the of ZnO nanoflakes, which could be employed for the remediation of dyes in textile effluents.     

ZnO-based ternary nanocomposite for decolorization of methylene blue by photocatalytic dynamic membrane

In this article, novel Ag–ZnO/g-C₃N₄/GO ternary nanocomposites were prepared via co-precipitation method by 1%w Ag, 50% w g-C₃N₄, 10% w GO concentration and applied in dynamic membranes. The characteristics of Ag–ZnO/g-C₃N₄/GO nanocomposite were evaluated by various techniques such as X-ray diffraction, field emission scanning electron microscopy, energy dispersive X-ray map, transmission electron microscopy, X-ray photoelectron spectroscopy, photocatalyst. The photocatalytic degradation of methylene blue was investigated under visible light. The photocatalytic efficiency of 93.43% for methylene blue degradation was obtained for Ag–ZnO/g-C₃N₄/GO nanocomposite after 50 min of irradiation, which was remarkably higher than that of pure ZnO, bare g-C₃N₄, Ag–ZnO, and Ag–ZnO/g-C₃N₄ at the same irradiation time. Likewise, in self-forming and pre-coated membranes, ternary nanocomposites can play a vital role in the membrane surface properties, as well as their decolorization performance. The rejection of methylene blue was 30% in pure polyethersulfone membrane, while the photocatalytic degradation of methylene blue in Ag–ZnO/g-C₃N₄/GO nanocomposites was 88.46% and 98.86% after 10 and 15 min of irradiation in both self-forming and pre-coated dynamic membranes, respectively. Experimental results show that the dynamic membrane possesses a higher ability for degradation of MB in a shorter period of time than the static system.     

Studies on hydrothermal synthesis of photolumniscent rare earth (Eu3+ & Tb3+) doped NG@FeMoO4 for enhanced visible light photodegradation of methylene blue dye

FeMoO₄ nanorods and their rare earth (Eu³⁺ and Tb³⁺) doped composites with nitrogen doped graphene (NG) were synthesized by facile hydrothermal method in aqueous medium. X-ray diffraction (XRD) analysis of the as-synthesized samples was done to study the phase purity and crystalline nature. FTIR and Raman Spectroscopy have been studied for investigating the bonding in nanostructures. The surface morphology of the samples was investigated with field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The photolumniscent nature of the samples was investigated by the using the fluorescence spectrophotometer. The photocatalytic degradation efficiency of the prepared pure FeMoO₄ and its rare earth doped composites with nitrogen doped graphene was evaluated as function of visible light irradiation versus concentration of methylene blue (MB dye). The prepared nanocomposites show enhanced photocatalytic efficiency as compared to the bare FeMoO₄ nanorods.     

Photo-degradation of methylene blue using Ta-doped ZnO nanoparticle

A photocatalyst of Ta-doped ZnO was prepared by a modified Pechini-type method. The structural, morphological properties and photocatalytic activity of 1 mol % Ta-doped ZnO samples annealed at different temperatures were characterized. The photo-oxidation of methylene blue under the visible-light irradiation followed the pseudo-first-order kinetics according to the Langmuir-Hinshelwood model. It is found that the photocatalysis of 1% Ta-doped ZnO annealed at 700 °C showed excellent performance of the photodegradation of methylene blue, which was attributed to a competitive trade-off among the crystallinity, surface hydroxyl groups, and specific surface area. The processing parameter such as the pH value also played an important role in tuning the photocatalytic activity. The maximum photodecomposed rate was achieved at pH=8, and an novel model about the absorption of methylene blue on the surface of the catalysts was proposed.     

Kinetics of the photocatalytic degradation of methylene blue on titanium dioxide

The first step of the photocatalytic degradation of methylene blue (MB) on anatase is photocatalytic reduction with subsequent decomposition of the dye itself and its leucobase. At low catalyst concentrations (≤2 g/L), the dye decomposition rate constant increases with increasing anatase concentration. A plateau appears for anatase concentrations above 2 g/L. Under steady-state conditions, the reaction kinetics is described by the Michaelis–Menten equation if the catalyst concentration is significantly greater than the MB concentration, which permits us to determine the kinetic parameters of the degradation process.     

Kinetic modeling of ZnO-rGO catalyzed degradation of methylene blue

Photodegradation of organic pollutants strongly depends on design of metal oxide semiconductor photocatalysts. Graphene, if composited with ZnO, can effectively enhance its photocatalytic performance for the eradication of pollutants from aqueous medium. Here in, ZnO-rGO is reported as highly active catalyst for degradation of methylene blue. A 200-mg/L solution of methylene blue dye was completely degraded within 1 h in comparison to 74% and 56% degradation over ZnO and rGO, respectively. The commonly used mechanisms of heterogeneous catalytic reactions, the Langmuir-Hinshelwood mechanism, and the Eley-Rideal mechanisms, were used to describe the reaction kinetics. The Langmuir-Hinshelwood mechanism was found as more favorable in this study. Apparent activation energy, E_ap, true activation energy, E_T, entropy, ΔS, and enthalpy, ΔH were calculated as 36.2 kJ/mol, 13.1 kJ/mol, 197.5 J/mol, and 23.1 kJ/mol, respectively.     

Biosynthesis of zinc oxide nanoparticles using Euphorbia milii leaf constituents: Characterization and improved photocatalytic degradation of methylene blue dye under natural sunlight

A facile biosynthesis route was followed to prepare zinc oxide nanoparticles (ZnO NPs) using Euphorbia milii (E. milii) leaf constituents. The SEM images exhibited presence of spherical ZnO NPs and the corresponding TEM images disclosed monodisperse nature of the ZnO NPs with diameter ranges between 12 and 20 nm. The Brunauer–Emmett–Teller (BET) analysis revealed that the ZnO NPs have specific surface area of 20.46 m²/g with pore diameter of 2 nm–10 nm and pore volume of 0.908 cm³/g. The EDAX spectrum exemplified the existence of Zn and O elements and non-appearance of impurities that confirmed pristine nature of the ZnO NPs. The XRD pattern indicated crystalline peaks corresponding to hexagonal wurtzite structured ZnO with an average crystallite size of 16.11 nm. The FTIR spectrum displayed strong absorption bands at 512 and 534 cm^?1 related to ZnO. The photocatalytic action of ZnO NPs exhibited noteworthy degradation of methylene blue dye under natural sunlight illumination. The maximum degradation efficiency achieved was 98.17% at an illumination period of 50 min. The reusability study proved considerable photostability of the ZnO NPs during photocatalytic experiments. These findings suggest that the E. milii leaf constituents can be utilized as suitable biological source to synthesis ZnO NPs for photocatalytic applications.     

Efficient photocatalytic degradation of rhodamine-B by Fe doped CuS diluted magnetic semiconductor nanoparticles under the simulated sunlight irradiation

The present work is planned for a simple, inexpensive and efficient approach for the synthesis of Cu_1-xFe_xS (x = 0.00, 0.01, 0.03, 0.05 and 0.07) nanoparticles via simplistic chemical co-precipitation route by using ethylene diamine tetra acetic acid (EDTA) as a capping molecules. As synthesized nanoparticles were used as competent catalysts for degradation of rhodamine-B organic dye pollutant. The properties of prepared samples were analyzed with energy dispersive analysis of X-rays (EDAX), X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-visible optical absorption spectroscopy, Fourier transform infrared (FTIR) spectra, Raman spectra and vibrating sample magnetometer (VSM). EDAX spectra corroborated the existence of Fe in prepared nanoparticles within close proximity to stoichiometric ratio. XRD, FTIR and Raman patterns affirmed that configuration of single phase hexagonal crystal structure as that of (P6₃/mmc) CuS, without impurity crystals. The average particle size estimated by TEM scrutiny is in the assortment of 5–10 nm. UV-visible optical absorption measurements showed that band gap narrowing with increasing the Fe doping concentration. VSM measurements revealed that 3% Fe doped CuS nanoparticles exhibited strong ferromagnetism at room temperature and changeover of magnetic signs from ferromagnetic to the paramagnetic nature with increasing the Fe doping concentration in CuS host lattice. Among all Fe doped CuS nanoparticles, 3% Fe inclusion CuS sample shows better photocatalytic performance in decomposition of RhB compared with the pristine CuS. Thus as synthesized Cu_0·97Fe_0·03S nanocatalysts are tremendously realistic compounds for photocatalytic fictionalization in the direction of organic dye degradation under visible light.