Synthesis of an Ag–ZnO nanocomposite catalyst for visible light-assisted degradation of a textile dye in aqueous solution

The photocatalytic activity of silver-deposited ZnO in the photodegradation of methyl orange (MO) was investigated. The as-prepared photocatalysts were characterized by X-ray diffraction, UV–visible diffuse reflectance spectroscopy, and photoluminescence spectroscopy. The results showed that the silver-deposited ZnO had a visible light plasmon absorption band. The photocatalytic degradation experiment revealed that the catalytic efficiency of the Ag–ZnO composite in the degradation of MO was greater than that of pure ZnO samples. This study shows that the degradation process is dominated by the Ag–ZnO photocatalytic system, complying with a pseudo-first-order rate law. Under the experimental conditions, approximately 65.0% dye removal was achieved within 100 min.     

Jute stick extract assisted hydrothermal synthesis of zinc oxide nanoflakes and their enhanced photocatalytic and antibacterial efficacy

In this paper, we used green and hydrothermal methodology to prepare zinc oxide (ZnO) nanoflakes (NFs) with jute stick extract (J–ZnO NFs) as growth substrate. The prepared materials were characterized using different analytical techniques including ultraviolet–visible spectroscopy (UV–vis), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), fourier transform infrared (FTIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). The characteristic absorption peak for ZnO NFs and J–ZnO NFs were observed from the UV–vis spectrum at 373 and 368 nm respectively. The hexagonal wurtzite crystal structure of ZnO NFs and J–ZnO NFs was confirmed by XRD analysis. FESEM and TEM analyses of synthesized J–ZnO NFs confirmed their NFs shape and collectively flower-like structure formation by the assembly of NFs of J–ZnO on cellulose of jute stick extract substrate. The FTIR analysis revealed the functional groups of jute stick extract biomolecules, mainly cellulose, are responsible for the formation of collectivel flower like J–ZnO NFs structure. The XPS analysis revealed the surface and chemical compositions (Zn, C, and O) of J–ZnO NFs. The photocatalytic performance of ZnO NFs and J–ZnO NFs samples was carried out by the degradation of methylene blue (MB) dye solution under UV light irradiation. The degradation efficiency of ZnO NFs and J–ZnO NFs was obtained 79 % and 89 %, respectively, for 5 h. Notably, the degradation efficiency of the J–ZnO NFs was 98 % after 8 h of irradiation, which is very inspiring. The both NFs exhibited first-order kinetics with MB photodegradation. We also examined the possible antibacterial activity of both samples against Escherichia coli (E. coli) pathogens, which demonstrated a significant result with a 17 mm and 19 mm zone of inhibition by ZnO NFs and J–ZnO NFs respectively.     

Band structure tuning of ZnO/CuO composites for enhanced photocatalytic activity

The toxic dye pigments, even in small quantities, can damage ecosystems. Removing organic, inorganic, and microbiological contaminants from wastewater via heterogeneous photocatalysis is a promising method. Herein, we report the band structure tuning of ZnO/CuO nanocomposites to enhance photocatalytic activity. The nanocomposites were synthesized by a chemical approach using step-wise implantation of p-type semiconductor CuO to n-type semiconductor ZnO. Various characterization techniques such as X-ray diffraction analysis (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray analysis (EDX) and UV spectroscopy were used to investigate the crystal structure, surface morphology, elemental composition and optical properties of the synthesized samples. As the CuO content increased from 10% to 50% in ZnO/CuO nanocomposites, the optical bandgap decreased from 3.36 to 2.14 eV. The photocatalytic activity of the samples was evaluated against the degradation of methylene blue (MB) under visible irradiation. Our study demonstrates a novel p–n junction oxide photocatalyst based on wt. 10% CuO/ZnO with superior photocatalytic activity. Effectively 66.6% increase in degradation rate was achieved for wt. 10% CuO/ZnO nanocomposite compared to pure ZnO nanoparticles.     

Preparation and characterization of zinc oxide nanoflakes using anodization method and their photodegradation activity on methylene blue

In this work, we report the formation of leaf-like ZnO nanoflakes by anodization of zinc foil in a mixture of ammonium sulfate and sodium hydroxide electrolytes under various applied voltage and concentration of sodium hydroxide. The morphology and structure of ZnO nanoflakes were investigated by field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction analysis. In addition, the photocatalytic activity of the prepared nanoflakes zinc oxide was evaluated in the photodegradation of organic dye methylene blue (MB) solution under UV irradiation. It was found that zinc oxide prepared under high concentration of sodium hydroxide and high voltage showed better performance in the photodegradation of methylene blue.     

Preparation,characterization and activity evaluation of p–n junction photocatalyst p-NiO/n-ZnO

In this paper, p–n junction photocatalyst NiO/ZnO was prepared by the sol–gel method using Ni (NO₃)₂ and zinc acetate as the raw materials. The structural and optical properties of the p–n junction photocatalyst NiO/ZnO were characterized by X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) analysis, UV–Vis diffuse reflection spectrum (DRS) and the fluorescence emission spectra. The photocatalytic activity of the photocatalyst was evaluated by photocatalytic reduction of Cr₂O₇ ²⁻ and photocatalytic oxidation of methyl orange (MO). The results showed that the photocatalytic activity of the p–n junction photocatalyst NiO/ZnO is much higher than that of ZnO on the photocatalytic reduction of Cr₂O₇ ²⁻. However, the photocatalytic activity of the photocatalyst is much lower than that of ZnO on the photocatalytic oxidation of methyl orange. Namely, the p–n junction photocatalyst NiO/ZnO has higher photocatalytic reduction activity, but lower photocatalytic oxidation activity. The heat treatment condition also influences the photocatalytic activity strongly, and the best preparation condition is about 400 °C for 2 h. Effect of the heat treatment condition on the photocatalytic activity of the photocatalyst was also investigated. The mechanisms of influence on the photocatalytic activity were discussed by the p–n junction principle.     

An effective nanocomposite of polyaniline and ZnO: preparation,characterizations, and its photocatalytic activity

The polyaniline/zinc oxide (PANI/ZnO) nanocomposites were prepared by in situ polymerization of aniline monomer with ZnO nanomaterials and applied as a photocatalyst for the degradation of methylene blue (MB) dye. The morphological observations elicited the agglomerations of PANI sheets which occurred due to the interaction between PANI and ZnO nanomaterials in PANI/ZnO nanocomposites. As compared to pristine PANI, the UV–vis spectra exhibited that the absorption peak of π–π* transitions considerably shifted to higher wavelength at 360 nm from 325 nm in the nanocomposites. The photocatalytic activity results indicated the substantial degradation of MB dye by ~76% over the surface of PANI/ZnO nanocomposite catalyst under light illumination. The PANI/ZnO nanocomposites showed three times higher photocatalytic activity to MB dye degradation compared to pristine PANI might due to high photogenerated electron (ē)–hole (h⁺) pairs charge separation.     

Large-scale synthesis of ZnO balls made of fluffy thin nanosheets by simple solution process: structural, optical and photocatalytic properties

This paper reports a large-scale synthesis of ZnO balls made of fluffy thin ZnO nanosheets by simple solution process at low-temperature of 65±2°C. The synthesized ZnO structures were characterized in detail in terms of their morphological, structural, optical and photocatalytic properties. The detailed morphological characterizations, done by field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM), confirmed that the synthesized products are ZnO balls which are made by accumulation of hundreds of thin ZnO nanosheets. Interestingly, it is seen that the nanosheets are arranged in such a special fashion that they made ball-like morphologies. Detailed structural examinations revealed that of as-synthesized ZnO products are well-crystalline and possessing wurtzite hexagonal phase. The optical property, measured by UV-Visible spectroscopy, substantiated good optical properties for as-synthesized ZnO balls. The as-synthesized ZnO balls were utilized as an efficient photocatalysts for the photocatalytic degradation of methylene blue (MB) dye. Almost complete degradation of MB was observed in presence of ZnO balls composed of nanosheets within 70 min under UV-light irradiation. By comparing the photocatalytic performance with commercially available TiO(2)-UV-100, it was observed that the synthesized ZnO balls exhibited superior photocatalytic performance as compared to TiO(2)-UV-100 photocatalyst.     

Combustion synthesis of calcium doped ZnO nanoparticles for the photocatalytic degradation of methylene blue dye

ZnO nanoparticles are one of the prominent photocatalysts for environmental applications due to its high redox ability, nontoxic and higher stability. This report explains the synthesis of ZnO nanoparticles by a simple solution combustion method using zinc nitrate hexahydrate as an oxidizing agent and incense stick powder as fuel at 400 °C. Several techniques were adopted for the characterization of the obtained product. X-ray diffraction (XRD) pattern shows that a lower concentration of fuel gives pure ZnO and a higher concentration of fuel results in calcium doped ZnO with a cubic phase having a crystallite size of 32–28 nm. UV–vis spectrum shows that as the fuel concentration increases, band gap decreases and reaches to 3.33 eV for 3 g of fuel. Spongy networks with many pores wereobserved in the scanning electron microscope (SEM) and transmission electron microscope (TEM) images showed the average particle size of Ca doped ZnO NPs is about 20 nm. Pure and Ca doped ZnO nanoparticles were examined for photocatalytic degradation of methylene blue (MB) dye under UV light irradiation. The results prove that Ca doped ZnO nanoparticles show good photocatalytic activity.     

Enzymes and phytochemicals from neem extract robustly tuned the photocatalytic activity of ZnO for the degradation of malachite green (MG) in aqueous media

The malachite green (MG) is very difficult to degrade in water; thus, it needs an efficient photocatalyst. In this study, neem extract was used to tune the surface and crystal properties of ZnO nanostructures for the photodegradation of MG. The biosynthesized ZnO samples were prepared by hydrothermal method in the presence of 5, 10 and 15 mL of neem extract. The structural characterization has shown nanoparticle like morphology of ZnO as revealed by scanning electron microscopy (SEM) and hexagonal phase was confirmed by powder X-ray diffraction (XRD) technique. The XRD analysis has shown a shift in the 2 theta towards lower angle for ZnO with increasing amount of neem extract. Also, the crystallite particle size of ZnO was decreased with increasing neem extract. The UV–visible spectroscopy has shown the decrease in the optical band gap of ZnO, and the lowest band gap is possessed by ZnO sample produced with 15 mL of neem extract. The ZnO sample obtained with 15 mL of neem extract has shown approximately 99% degradation efficiency for MG for 70 min in aqueous solution. The superior photocatalytic activity of ZnO sample with 15 mL of neem extract could be attributed from the decrease in charge recombination rate due to the decreased optical band gap and particle size.

     

CPF/ZnO纳米复合催化材料的制备

通过原位聚合-热转化两步法,利用ZnO纳米微粒和糠醇(F)制备出了具有大共轭结构的高分子(CPF)和ZnO的纳米复合催化材料(CPF/ZnO);用TG-DTA、TEM、XRD、XPS、IR和UV-Vis等技术对其热稳定性、形貌、尺寸、结构及吸光特性等进行了表征,以亚甲基蓝(MB)溶液的催化降解研究了该材料在自然光条件下的催化性能。结果表明,由该方法可以得到平均尺寸约为 50 nm的CPF/ZnO纳米复合催化材料;其中的CPF为具有极性基团和大共轭结构的高分子;ZnO与CPF化学键合在一起;CPF的引入将ZnO的光谱响应拓展到了整个紫外-可见区,从而极大地改善了ZnO在自然光条件下的催化性能。如在460 ℃下处理40 min所得的纳米复合材料,在自然光条件下,10 min即可使MB溶液完全脱色,而在相同条件下,纯纳米ZnO仅能使MB的脱色率为10%左右;该催化材料重复使用3次仍可使MB溶液的脱色率保持在80%以上。     

Fe2O3/ZnO/ZnFe2O4 composites for the efficient photocatalytic degradation of organic dyes under visible light

In this study, novel ternary Fe₂O₃/ZnO/ZnFe₂O₄ (ZFO) composites were successfully prepared through a simple hydrothermal reaction with subsequent thermal treatment. The as-prepared products were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET) analysis, Barrett-Joyner-Halenda (BJH) measurement, and UV–vis diffuse reflectance spectroscopy (UV–vis DRS). The photocatalytic degradation of rhodamine B (Rh B) under visible light irradiation indicated that the ZFO composites calcined at 500 °C has the best photocatalytic activity (the photocatalytic degradation efficiency can reach up to 95.7% within 60 min) and can maintain a stable photocatalytic degradation efficiency for at least three cycles. In addition, the photocatalytic activity of ZFO composites toward dye decomposition follows the order cationic Rh B > anionic methyl orange. Finally, using different scavengers, superoxide and hydroxyl radicals were identified as the primary active species during the degradation reaction of Rh B.     

Photocatalytic degradation of acid blue 74 in water using Ag–Ag2O–Zno nanostuctures anchored on graphene oxide

Water pollution due to industrial effluents from industries which utilize dyes in the manufacturing of their products has serious implications on aquatic lives and the general environment. Thus, there is need for the removal of dyes from wastewater before being discharged into the environment. In this study, a nanocomposite consisting of silver, silver oxide (Ag₂O), zinc oxide (ZnO) and graphene oxide (GO) was synthesized, characterized and photocatalytically applied in the degradation (and possibly mineralization) of organic pollutants in water treatment process. The Ag–Ag₂O–ZnO nanostructure was synthesized by a co-precipitation method and calcined at 400 °C. It was functionalized using 3-aminopropyl triethoxysilane and further anchored on carboxylated graphene oxide via the formation of an amide bond to give the Ag–Ag₂O–ZnO/GO nanocomposite. The prepared nanocomposite was characterized by UV–Vis diffuse reflectance spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electronic microscopy (SEM), energy dispersive X-ray spectrometry (EDX), Fourier transformed infrared spectroscopy (FTIR), and Raman spectroscopy. The applicability of Ag–Ag₂O–ZnO/GO nanocomposite as a photocatalyst was investigated in the photocatalytic degradation of acid blue 74 dye under visible light irradiation in synthetic wastewater containing the dye. The results indicated that Ag–Ag₂O–ZnO/GO nanocomposite has a higher photocatalytic activity (90% removal) compared to Ag–Ag₂O–ZnO (85% removal) and ZnO (75% removal) respectively and thus lends itself to application in water treatment, where the removal of organics is very important.     

Synthesis and characterization of novel poly(1-naphthylamine)/zinc oxide nanocomposites: Application in catalytic degradation of methylene blue dye

The organic–inorganic poly(1-naphthylamine)/ZnO (PNA/ZnO) nanocomposites were synthesized by in situ chemical oxidative polymerization of 1-naphthylamine monomer and ZnO nanomaterials for the photocatalytic degradation of methylene blue (MB) dye under visible light. The surface properties of PNA molecules were altered by adding the ZnO nanomaterials. The crystalline and the optical properties of PNA/ZnO nanocomposites were improved with the increased contents of ZnO nanomaterials in PNA molecules due to the effective interaction of PNA to the surface of ZnO nanomaterials. The prepared PNA/ZnO nanocomposites presented moderate photocatalytic MB dye degradation of ~22% under visible light. The occurrence of dye degradation under visible light might attribute to high-charge separation of ē-h⁺ pairs at the interfaces of PNA and ZnO nanomaterials in its excited state under light irradiation.     

Enhanced Photocatalytic Performance of ZnO Nanorods Coupled by Two‐Dimensional α‐MoO3 Nanoflakes under UV and Visible Light Irradiation

We exploit the utilization of two‐dimensional (2D) molybdenum oxide nanoflakes as a co‐catalyst for ZnO nanorods (NRs) to enhance their photocatalytic performance. The 2D nanoflakes of orthorhombic α‐MoO₃ were synthesized through a sonication‐aided exfoliation technique. The 2D MoO₃ nanoflakes can be further converted to substoichiometric quasi‐metallic MoO_3?x by using UV irradiation. Subsequently, 1D–2D MoO₃/ZnO NR and MoO_3?x/ZnO NR composite photocatalysts have been successfully synthesized. The photocatalytic performances of the novel nanosystems in the decomposition of methylene blue are studied by using UV‐ and visible‐illumination setup. The incorporated 2D nanoflakes show a positive influence on the photocatalytic activity of the ZnO. The obtained rate constant values follow the order of pristine ZnO NR<MoO₃/ZnO NR<MoO_3?x/ZnO NR composites. The enhancement of the photocatalytic efficiency can be ascribed to a fast charge carrier separation and transport within the heterojunctions of the MoO₃/ZnO NRs. In particular, the best photocatalytic performance of the MoO_3?x/ZnO NR composite can be additionally attributed to a quasi‐metallic conductivity and substoichiometry‐induced mid‐gap states, which extend the light absorption range. A tentative photocatalytic degradation mechanism was proposed. The strategy presented in this work not only demonstrates that coupling with nanoscale molybdenum oxide nanoflakes is a promising approach to significantly enhance the photocatalytic activity of ZnO but also hints at new type of composite catalyst with extended applications in energy conversion and environmental purification.     

Synthesis of nano-sized Ag3PW12O40/ZnO heterojunction as a photocatalyst for degradation of organic pollutants under simulated sunlight

With the rapid development of the world economy, water pollution has become increasingly serious. The photocatalytic degradation of pollutants is one of the most promising environmental treatment techniques. In this study, novel Ag₃PW₁₂O₄₀/ZnO nanoheterojunction was successfully constructed via a chemical process and was then characterized using X-ray diffraction, transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, diffuse reflectance spectroscopy, Brunauer-Emmett-Teller analysis, and photoluminescence measurements. The synthesized nanoheterojunction exhibited good crystallinity and dispersity. The particle diameter of the composite was approximately 800 nm, the bandgap was 2.92 eV, and the specific surface area was approximately 10.5 m².g^?1. Under optimum conditions, the photocatalyst degraded 82.1% RhB in 60 min. Moreover, the novel Ag₃PW₁₂O₄₀/ZnO heterojunction also exhibited an excellent recycling stability. Hydroxyl radicals, superoxide radicals, and holes played important roles in the photocatalytic degradation process. A possible mechanism for the enhanced photocatalytic performance of the nanoheterojunction was proposed. This work provides a strong foundation for the application of Ag₃PW₁₂O₄₀/ZnO nanoheterojunction for treating environmental organic pollutants.     

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.     

Co doped ZnO nanowires as visible light photocatalysts

High aspect ratio cobalt doped ZnO nanowires showing strong photocatalytic activity and moderate ferromagnetic behaviour were successfully synthesized using a solvothermal method and characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), vibrating sample magnetometry (VSM) and UV–visible absorption spectroscopy. The photocatalytic activities evaluated for visible light driven degradation of an aqueous methylene orange (MO) solution were higher than for Co doped ZnO nanoparticles at the same doping level and synthesized by the same synthesis route. The rate constant for MO visible light photocatalytic degradation was 1.9·10⁻³ min⁻¹ in case of nanoparticles and 4.2·10⁻³ min⁻¹ in case of nanowires. We observe strongly enhanced visible light photocatalytic activity for moderate Co doping levels, with an optimum at a composition of Zn_0.95Co_0.05O. The enhanced photocatalytic activities of Co doped ZnO nanowires were attributed to the combined effects of enhanced visible light absorption at the Co sites in ZnO nanowires, and improved separation efficiency of photogenerated charge carriers at optimal Co doping.     

ZnO修饰提升花状BiOBr的可见光催化降解罗丹明B性能

以Bi(NO3)3·5H2O、Zn(CH3COO)2·2H2O和NaBr为前驱体,采用简单溶剂热法制备BiOBr/ZnO三维花状微纳米复合材料.采用X射线衍射、扫描电子显微镜、X射线光子能谱、N2吸附-脱附、光致发光和电子顺磁共振等分析技术对其理化性质进行了表征.通过可见光催化降解罗丹明B(RhB)的实验测试了复合材料...     

Structural,optical, electrical,and photocatalytic properties of manganese doped zinc oxide nanocrystals

Manganese-doped and undoped ZnO nanocrystals were synthesized via wet-chemical methods. The structure, physico-chemical, electrical and optical properties of the as-prepared products were characterized by using the X-ray diffraction (XRD), UV-vis diffuse reflectance spectroscopy (DRS), photoluminescence spectroscopy (PLS) and electrochemical impedance spectroscopy (EIS) techniques. The photocatalytic activity of Mn-doped ZnO nanocrystal (mixed phases) has been examined under the visible-irradiation by using photocatalytic oxidation of rhodamine B (RhB) dye as a model reaction, and compared with that of known system such as pure ZnO nanocrystal (single-phase). The results showed that Mn doped ZnO nanocrystals bleaches RhB much faster than undoped ZnO upon its exposure to the visible light. The enhancement of the photocatalytic activity was discussed as an effect due to the Mn doping in the Mn-doped ZnO semiconductors, which shifts the optical absorption edge to the visible region and alters the electron-hole pair separation conditions. These factors are responsible for the higher photocatalytic performance of Mn/ZnO composites.