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.     

Preparation, characterization of the Ta-doped ZnO nanoparticles and their photocatalytic activity under visible-light illumination

This paper describes a novel catalyst of the Ta-doped ZnO nanocrystals prepared by a modified polymerizable complex method using the water-soluble tantalum precursor as the sources of Ta. The catalysts were characterized by means of various analytical techniques as a function of Ta content (x=0–4 mol%) systematically. A remarkable advantage of the results was confirmed that dopant Ta enhanced the visible-light absorption of ZnO and the low-solubility tantalum doping could restrain the growth of crystal and minish the particle size. The relationship between the physicochemical property and the photocatalytic performance was discussed, and it was found that the photocatalytic activity in the photochemical degradation of methylene blue under visible-light irradiation (λ420 nm) was dependent on the contents of the dopant, which could affect the particle size, concentration of surface hydroxyl groups and active hydrogen-related defect sites, and the visible-light absorption. The highest photocatalytic activity was obtained for the 1.0 mol% Ta-doped ZnO sample.     

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.     

Preparation of ZnS-Fluoropolymer nanocomposites and its photocatalytic degradation of methylene blue

The ZnS particles were immobilized on the surface of poly(vinylidene difluoride) (PVDF) mixing methacrylic acid (MAA)-trifluoroethyl acrylate (TFA) copolymer electrospun nanofibers. The PVDF and MAATFA copolymer nanofibers were prepared by electrospinning. Zinc ions were introduced onto the surface of nanofibers by coordinating with the carboxyls of MAA, and then sulfide ions were added to react with zinc ions to form ZnS particles under hydrothermal condition. The size and the amount of ZnS particles increased with the reaction time prolonging. The Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) results reveal that a chemical interaction exists between ZnS and fluoropolymer fibers. The degradation rate of methylene blue in ZnS-fluoropolymer nanocomposite system was considerably higher than in that of ZnS powders system under UV irradiation. There may be an adsorption-migration-photodegradation process during the degradation of methylene blue by using ZnS-fluoropolymer nanocomposites as photocatalyst. The photocatalytic activity of ZnS-fluoropolymer nanocomposites changes indistinctively after 10 times repeating tests.     

Enhanced photocatalytic activity of ZnO nanoparticles by surface modification with KF using thermal shock method

ZnO nanoparticles were modified with KF using thermal shock method at various temperatures in order to improve the photocatalytic activity of ZnO under both UVA and visible light irradiation. The influences of KF-modification on the crystal structure, morphology, UV–visible absorption, specific surface area as well as surface structure of ZnO were respectively characterized by XRD, FE-SEM, UV–Visible diffuse reflectance, N₂ adsorption and XPS spectroscopy. The photocatalytic activity was evaluated via the degradation of methylene blue under UVA irradiation. According to the results, the thermal shock process with KF did not modify the structure, the particle size and the optical properties of ZnO nanoparticles but successfully increase their UVA and visible light induced photocatalytic activity. This enhancement of activity may be attributed to the increase of surface hydroxyl groups and zinc vacancies of modified ZnO samples.     

A novel study on synthesis of egg shell based activated carbon for degradation of methylene blue via photocatalysis

Egg shell-based activated carbon was successfully synthesized by the simple chemical activation process. Orthophosphoric acid and sodium hydroxide used as an activation agent. XRD pattern reveals the hexagonal structure of activated carbon. The functional group presents in activated carbon was identified using FT-IR spectroscopy. SEM images show irregular shapes of carbon. The photocatalytic performance of investigated activated carbon by illuminating methylene blue dye under UV–Visible irradiations. Photocatalytic activity of activated carbon results maximum degradation efficiency of 83%. Adsorption efficiency have been increased with respect of time for degradation of dye. Free radicals and superoxide’s play a significant role is decolourization of methylene blue. Photocatalytic activity of activated carbon synthesized by Orthophosphoric acid results shows the high degradation efficiency when compared to NaOH.     

ZnO/ZnSe复合纳米结构的制备及可见光光催化性能

通过热水解法, 以氧化锌为模板, 成功制备出形貌均一的ZnO/ZnSe复合纳米结构. 为了对比不同O/Se比对光催化性能的影响, 保持其它反应参数不变, 调节还原剂水合肼的用量, 得到不同硒化程度的ZnO/ZnSe复合纳米结构. 采用场发射扫描电子显微镜、 X射线衍射仪和透射电子显微镜对样品的形貌及结构进行了表征, 通过测试该复合结构对亚甲基蓝的可见光催化降解评估了其光催化效率. 结果表明, 与纯ZnO比, ZnO/ZnSe复合结构在可见光区域和紫外光区域的光吸收范围变宽, 显示出较高的光催化效率. 原因在于ZnSe导带上的电子在扩散势能的作用下迁移到ZnO的导带上, 而空穴仍保留在ZnSe价带, 这样有助于光生电子和空穴对的分离, 降低其复合机率, 从而提高ZnO的光催化效率.     

Comparative study for the removal of methylene blue via adsorption and photocatalytic degradation

Physically and chemically activated carbons were prepared from date pits and olive stones. Titania and WO(x)-TiO(2)/MCM-41 were prepared as photoactive catalysts. Surface characterizations were investigated from ash content, pH, base neutralization capacities and FT-IR techniques. The textural characteristics, namely specific surface area (S(BET)) and pore texture, were determined from low temperature adsorption of N(2) at 77 K. The decolorization of aqueous solution of methylene blue was performed by means of two alternative methods. Steam-activated carbons own higher surface area compared with ZnCl(2)-activated carbons, and the micropore surface area represents the major contribution of the total area. Steam-activated carbons were the most efficient decolorizing adsorbents owing to its higher surface area, total pore volume and the basic nature of the surface. The calculated values of DeltaG(0), DeltaH(0) and DeltaS(0) indicate the spontaneous behavior of adsorption. The photocatalytic degradation is more convenient method in decolorizing of methylene blue compared with the adsorption process onto activated carbons.     

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.     

砚状ZnO/石墨烯复合物的制备及其光催化性能

采用一步溶液法制备了具有砚状形貌的ZnO/石墨烯复合材料。利用扫描电子显微镜(SEM)、高分辨透射电子显微镜(HRTEM)等研究不同制备条件下ZnO形貌、石墨烯的复合状态和砚状ZnO的生长机理;通过测试300W氙灯对甲基蓝溶液(MB)的光催化效率,研究制备条件、形貌结构对复合物的光催化性能的影响;通过对复合物光致发光(PL)光谱以及紫外-可见光谱测试,研究石墨烯复合物对光生电子-空穴对的复合以及光吸收效率的影响。研究结果表明,砚状ZnO的生长机理为掏蚀机理;复合石墨烯增强了这种ZnO的光吸收效率、降低了ZnO的带隙,并且降低了光生电子-空穴对复合几率,有利于提高光催化性能;砚状ZnO的砚底上表面粗糙,有利于反应面积的增加,砚底的厚度较薄,有利于光生电子-空穴对在较强的内建电场下迅速向相反方向分离,降低其复合几率,从而使其具有优异的光催化性能。     

Electrochemical determination of heparin using methylene blue probe and study on competition of Ba with methylene blue for binding heparin

Cyclic voltammetric investigation of the interaction of methylene blue (MB) with heparin (hep) at a gold electrode is presented. The combination of MB with heparin formed a nonelectroactive complex MB-hep, which resulted in the peak current decrease of MB. The anodic peak current difference of MB was found to be proportional to the concentration of heparin in the range of 0.666-64.5 μg mL⁻¹ with a detection limit of 270 ng mL⁻¹ and a satisfactory result was obtained for the determination of heparin in injection samples. The equilibrium constant for MB-hep complex was calculated to be 7.32 × 10⁵. The dynamic process of competition of Ba²⁺ with methylene blue for binding heparin was monitored using quartz crystal microbalance (QCM) technique. The reaction rate constant between Ba²⁺ and MB-hep was estimated to be 0.0022 s⁻¹.     

An electrochemical DNA-sensor developed with the use of methylene blue as a redox indicator for the detection of DNA damage induced by endocrine-disrupting compounds

An electrochemical biosensor capable of indirect detection of DNA damage induced by any one of the three endocrine-disrupting compounds (EDCs) – bisphenol A (BPA), 4-nonylphenol (NP) and 4-t-octylphenol (OP), has been researched and developed. The methylene blue (MB) dye was used as the redox indicator. The glassy carbon electrode (GCE) was modified by the assembled dsDNA/graphene oxide-chitosan/gold nano-particles to produce a dsDNA/GO-CS/AuNPs/GCE sensor. It was characterized with the use of electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and scanning electron microscopy (SEM) techniques. The loading/release of the MB dye by the dsDNA/GO-CS/AuNPs film was investigated, and the results showed that the process was reversible. Based on this, the sensor was used to measure the difference between the loading capabilities of intact and damaged dsDNA in the films. The sensor was then successfully applied to detect DNA damage electrochemically. The differential pulse voltammetry (DPV) peak current ratio for MB, observed before and after DNA damage, increased linearly in the presence the BPA, NP or OP compounds; the treatment range was 10–60 min, and the respective damage rates were 0.0069, 0.0044 and 0.0031 min⁻¹, respectively. These results were confirmed by the binding constants: 2.09 × 10⁶ M⁻¹ (BPA-DNA), 1.28 × 10⁶ M⁻¹ (NP-DNA) and 9.33 × 10⁵ M⁻¹ (OP-DNA), all of which were obtained with the use of differential pulse stripping voltammetry (DPSV).     

Facile synthesis of ZnO and Co3O4 nanoparticles by thermal decomposition of novel Schiff base complexes: Studying biological and catalytic properties

In this paper, a novel Zn(II) and Co(II) Schiff base complexes were synthesized by template method via refluxing 2,3-Naphthalenedicarboxaldehyde, Metal(II) chloride (Metal = Zn or Co), and L-phenylalanine. ZnO and Co₃O₄ nanoparticles were synthesized by thermal decomposition of Zn(II) and Co(II) complexes, respectively. The products were characterized using different instruments such as CHN, Conductivity, FT-IR, XRD, HR-TEM, and UV–Vis spectrophotometer. The experimental results of elemental analysis for Zn(II) and Co(II) complexes, agree with the calculated results, indicating that the Zn(II) and Co(II) complexes have 1:1 ligand/metal ratios. The molar conductance of the Zn(II) and Co(II) complexes, is less than 5 Ω^?1cm^?1mol^?1, confirming the non-electrolytic nature of the synthesized complexes. The average crystallite diameter of the ZnO and Co₃O₄ samples is 39.64 and 30.38 nm, respectively. The optical energy gap of the ZnO and Co₃O₄ samples are 2.75 and 3.25 eV, respectively. Methylene blue dye was utilized to examine the photocatalytic properties of the synthesized nanoparticles using UV irradiations in the absence and presence of hydrogen peroxide. The % degradation of the methylene blue dye in the presence of hydrogen peroxide using ZnO and Co₃O₄ samples after 40 min is 94.55 and 98.98, respectively. Six pathogenic microbes were utilized to examine the antimicrobial properties of the synthesized Schiff base complexes and their nanoparticles: Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Streptococcus species, Aspergillus species, and Candida species. Zn(II) and Co(II) complexes display inhibition towards all the studied microbes. Besides, ZnO and Co₃O₄ nanoparticles exhibit less inhibition towards Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Streptococcus species. Moreover, ZnO and Co₃O₄ nanoparticles have no activity towards Aspergillus and Candida species.     

Determination of methylene blue by resonance light scattering method using silica nanoparticles as probe

A simple and novel method was developed to determine methylene blue(MB) by resonance light scattering(RLS) using silica nanoparticles(SiO_2NPs) as the probe.It was found that MB could enhance the RLS intensity of SiO_2NPs.Moreover,the increase in RLS intensity was linear with the concentration of MB over the range of 0.01-3.0 μg mL~(-1).The limit of detection(LOD) was as low as 4.36 ng mL~(-1)(3σ) and the relative standard deviation(RSD) was 2.4%(n=6).Under the optimum experimental conditions,this proposed method was successfully applied for the determination of MB in aquaculture samples with recoveries between 96.3% and 107%.Possible mechanisms for the RLS enhancement of SiO_2NPs in the presence of MB were also discussed.     

Voltammetric determination of DNA hybridization using methylene blue and self-assembled alkanethiol monolayer on gold electrodes

An electrochemical DNA biosensor based on the recognition of single stranded DNA (ssDNA) by hybridization detection with immobilized complementary DNA oligonucleotides is presented. DNA and oligonucleotides were covalently attached through free amines on the DNA bases using N-hydroxysulfosuccinimide (NHS) and N-(3-dimethylamino)propyl-N′-ethylcarbodiimide hydrochloride (EDC) onto a carboxylate terminated alkanethiol self-assembled monolayers (SAM) preformed on a gold electrode (AuE). Differential pulse voltammetry (DPV) was used to investigate the surface coverage and molecular orientation of the immobilized DNA molecules. The covalently immobilized probe could selectively hybridize with the target DNA to form a hybrid on the surface despite the bases being attached to the SAM. The changes in the peak currents of methylene blue (MB), an electroactive label, were observed upon hybridization of probe with the target. Peak currents were found to increase in the following order: hybrid-modified AuE, mismatched hybrid-modified AuE, and the probe-modified AuE which indicates the MB signal is determined by the extent of exposed bases. Control experiments were performed using a non-complementary DNA sequence. The effect of the DNA target concentration on the hybridization signal was also studied. The interaction of MB with inosine substituted probes was investigated. Performance characteristics of the sensor are described.     

Electrochemical detection of DNA hybridization using methylene blue and electro-deposited zirconia thin films on gold electrodes

A novel electrochemical DNA biosensor based on methylene blue (MB) and zirconia (ZrO₂) thin films modified gold electrode for DNA hybridization detection is presented. Zirconia thin films were electrodynamically deposited onto the bare gold electrode in an aqueous electrolyte of ZrOCl₂ and KCl by cycling the potential between −1.1 and +0.7 V (versus Ag/AgCl) at a scan rate of 20 mV s⁻¹. Oligonucleotide probes with phosphate group at the 5′ end were attached onto the zirconia thin films because zirconia is affinity for phosphoric group. The surface density of the immobilized DNA molecules at the zirconia interface was investigated by fluorescence spectroscopy method. Hybridization was induced by exposure of the ssDNA-containing Au electrode to complementary ssDNA in solution. The decreases in the peak currents of MB, an electroactive label, were observed upon hybridization of probe with the target. The cathodic peak current (i_p) of MB after hybridization with the target DNA was linearly related to the logarithmic value of the target DNA concentration ranging from 2.25×10⁻¹⁰ to 2.25×10⁻⁸ mol l⁻¹. A detection limit of 1.0×10⁻¹⁰ mol l⁻¹ of oligonucleotides can be estimated.     

Electrochemical DNA biosensor for the detection of short DNA species of Chronic Myelogenous Leukemia by using methylene blue

A novel assay for the voltammetric detection of 18-bases DNA sequences relating to Chronic Myelogenous Leukemia (CML, Type b3a2) using methylene blue (MB) as the hybridization indicator was reported. DNA was covalently attached onto a glassy carbon electrode (GCE) through amines of the DNA bases using N-hydroxysulfosuccinimide (NHS) and N-(3-dimethylamion)propyl-N′-ethyl carbodiimidehydrochloride (EDC). The covalently immobilized single-stranded DNA (ssDNA) could selectively hybridize with its complementary DNA (cDNA) in solution to form double-stranded DNA (dsDNA) on the surface. A significant increase of the peak current for methylene blue upon the hybridization of immobilized ssDNA with cDNA in the solution was observed. This peak current change was used to monitor the recognition of CML DNA sequence. This electrochemical approach is sequence specific as indicated by the control experiments in which no peak current change was observed if a non-complementary DNA sequence was used. Factors, such as DNA target concentration and hybridization conditions determining the sensitivity of the electrochemical assay were investigated. Under optimal conditions, this sensor has a good calibration range between 1.25 × 10⁻⁷ and 6.75 × 10⁻⁷ M, with CML DNA sequence detection limit of 5.9 × 10⁻⁸ M.     

Facile preparation of hierarchically porous carbon using diatomite as both template and catalyst and methylene blue adsorption of carbon products

Hierarchically porous carbons were prepared using a facile preparation method in which diatomite was utilized as both template and catalyst. The porous structures of the carbon products and their formation mechanisms were investigated. The macroporosity and microporosity of the diatomite-templated carbons were derived from replication of diatom shell and structure-reconfiguration of the carbon film, respectively. The macroporosity of carbons was strongly dependent on the original morphology of the diatomite template. The macroporous structure composed of carbon plates connected by the pillar- and tube-like macropores resulted from the replication of the central and edge pores of the diatom shells with disk-shaped morphology, respectively. And another macroporous carbon tubes were also replicated from canoe-shaped diatom shells. The acidity of diatomite dramatically affected the porosity of the carbons, more acid sites of diatomite template resulted in higher surface area and pore volume of the carbon products. The diatomite-templated carbons exhibited higher adsorption capacity for methylene blue than the commercial activated carbon (CAC), although the specific surface area was much smaller than that of CAC, due to the hierarchical porosity of diatomite-templated carbons. And the carbons were readily reclaimed and regenerated.     

Adsorption of cationic methylene blue dye using microwave-assisted activated carbon derived from acacia wood: Optimization and batch studies

This study assesses the performance of optimized acacia wood-based activated carbon (AWAC) as an adsorbent for methylene blue (MB) dye removal in aqueous solution. AWAC was prepared via a physicochemical activation process that consists of potassium hydroxide (KOH) treatment, followed by carbon dioxide (CO₂) gasification under microwave heating. By using response surface methodology (RSM), the optimum preparation conditions of radiation power, radiation time, and KOH-impregnation ratio (IR) were determined to be 360 W, 4.50 min, and 0.90 g/g respectively, which resulted in 81.20 mg/g of MB dye removal and 27.96% of AWAC’s yield. Radiation power and IR had a major effect on MB dye removal while radiation power and radiation time caused the greatest impact on AWAC’s yield. BET surface area, mesopore surface area, and pore volume of optimized AWAC were found to be 1045.56 m²/g, 689.77 m²/g, and 0.54 cm³/g, respectively. Adsorption of MB onto AWAC followed Langmuir and pseudo-second order for isotherm and kinetic studies respectively, with a Langmuir monolayer adsorption capacity of 338.29 mg/g. Mechanism studies revealed that the adsorption process was controlled by film diffusion mechanism and indicated to be thermodynamically exothermic in nature.     

简单低温水浴法合成鳞片状氧化铜/四针状氧化锌晶须复合光催化剂(英文)

以硝酸铜为原料,聚乙二醇(PEG,Mw=400)为稳定剂和模板剂,采用简单的低温水浴合成法成功合成了四针状氧化锌晶须(T-ZnOw)表面负载鳞片状CuO的纳米复合光催化剂,系统研究了复合催化剂样品的晶体结构和形貌,通过荧光发光光谱(PL)和紫外光照射的条件下样品对阳离子污染物(亚甲蓝,MB)和阴离子污染物(甲基橙,MO)的光催化降解效率表征了样品的光催化性能,同时采用ICP-AES详细分析了PEG 400浓度对T-ZnOw表面负载CuO纳米颗粒数量的影响.结果表明,T-ZnOw表面有序地沉积了大量鳞片状CuO纳米颗粒,随着PEG 400浓度增加,T-ZnOw表面沉积的CuO纳米片数量逐渐增多,且CuO纳米片在T-ZnOw表面的排列更加有序.同时,PEG 400浓度的变化对合成样品特征发光峰的强度也有一定影响,当PEG 400浓度小于0.60 mol/L时,合成样品特征发光峰强度随着PEG 400浓度增大而减小;当PEG 400浓度大于0.60 mol/L时,样品的特征发光峰强度随之有所增加.在紫外光照射条件下,CuO/T-ZnOw纳米复合催化剂样品对MB和MO水溶液的降解均表现出优异的光催化活性,当PEG 400浓度≤0.60 mol/L时,样品的光催化活性随着PEG 400浓度的增大而增加;而当PEG 400浓度大于0.60 mol/L时,样品的光催化活性反而有所降低.此外,在相同条件下,所有样品对MB水溶液的降解效率明显高于对MO水溶液的降解效率.