Preparation,characterization and catalytic activity of biomaterial-supported copper nanoparticles

Synthesis of copper nanoparticles was carried out with nanocrystalline cellulose (NCC) as a support by reducing CuSO₄·5H₂O ions using hydrazine. Ascorbic acid and aqueous NaOH were also used as an antioxidant and pH controller, respectively. The synthesized copper nanoparticles supported on NCC (CuNPs@NCC) were characterized by UV–vis, XRD, TEM, XRF, TGA, DSC, N₂ adsorption-desorption method at 77 K and FTIR. The UV–vis confirmed the formation and stability of the CuNPs, which indicated that the maximum absorbance of CuNPs@NCC was at 590 nm due to the surface plasmon absorption of CuNPs. Morphological characterization clearly showed the formation of a spherical structure of the CuNPs with the mean diameter and standard deviation of 2.71 ± 1.12 nm. Similarly, XRD showed that the synthesized CuNPs@NCC was of high purity. The thermal analysis showed that the CuNPs@NCC exhibited better thermal behaviors than NCC. BET surface area revealed that the N₂ adsorption–desorption isotherms of CuNPs@NCC featured a type IV isotherm with an H3 hysterisis loop. This chemical method is simple, cost effective, and environmentally friendly. Compared to NCC-supported CuNPs and unsupported CuNPs, the as-prepared CuNPs@NCC exhibit a superior catalytic activity and high sustainability for the reduction of methylene blue with NaBH₄ in aqueous solution at room temperature. The CuNPs@NCC achieved complete reduction of MB with completion time, rate constant and correlation coefficient (R ²) of 12 min, 0.7421 min^?1 and 0.9922, respectively.     

Biosynthesis and Photocatalytic Properties of SnO<Subscript>2</Subscript> Nanoparticles Prepared Using Aqueous Extract of Cauliflower

This work reports the biosynthesis of Sn(OH)₂ using aqueous extract of fresh cauliflower (Brassica oleracea L. var. botrytis), and the subsequent preparation of SnO₂ nanoparticles at two different annealing temperatures of 300 and 450 °C for 2 h. The obtained SnO₂ nanoparticles were denoted as S1 and S2 for the samples prepared at 300 and 450 °C, respectively. XRD analysis identified rutile tetragonal phase of SnO₂ nanoparticles and TEM results gave a quasispherical and spherical morphologies for S1 and S2 respectively of the size range 3.62–6.34 nm. The optical properties were studied with UV–vis and photoluminescence (PL) spectroscopies, and the nanoparticles showed blue shift in their absorption edges. The observed emission peak in the PL spectra found around 419 nm is attributable to oxygen vacancies and defects. Photocatalytic activities of the nanoparticles (S1 and S2) were studied using methylene blue (MB) under ultraviolet light irradiation and the results reveal 91.89 and 88.23% degradation efficiency of MB by S1 and S2 respectively over a period of 180 min.     

Structural, optical and photocatalytic studies of Fe doped ZnS nanoparticles

Fe doped ZnS nanoparticles (Zn_1?xFe_xS; where x = 0.00, 0.03, 0.05 and 0.10) were synthesized by a chemical precipitation method. The synthesized products were characterized by X-ray diffraction, scanning electron microscope, transmission electron microscope, ultraviolet–visible and photoluminescence spectrometer. The X-ray diffraction and transmission electron microscope studies show that the size of crystallites is in the range of 2–10 nm. Photocatalytic activities of ZnS and 3, 5 and 10 mol% Fe doped ZnS were evaluated by decolorization of methylene blue in aqueous solution under ultraviolet and visible light irradiation. It was found that the Fe doped ZnS bleaches methylene blue much faster than the undoped ZnS upon its exposure to the visible light as compared to ultraviolet light. The optimal Fe/Zn ratio was observed to be 3 mol% for photocatalytic applications.     

Synthesis of VO2 Nanopowders. Part II. Hydrolysis of Vanadium Alkoxide/Citric Acid Premixes: VO2 Nanostructures of Controlled Shape

Reaction of VO(OiPr)₃/citric acid premixes with excess water produces stable, blue dispersions of V_xO_y gel nanoparticles (5–100 nm in diameter) that can be isolated via acetone precipitation. Annealing under reducing conditions transforms these gel particles into crystalline, faceted VO₂ nanoparticles of similar size. Larger V_xO_y gel particles (75–200 nm in diameter) form when V_xO_y nanogel dispersions are aged with aqueous ammonia. Upon annealing, these larger gel particles transform into crystalline VO₂ rods of 50 nm–10 μm in length. Hysteresis loops confirming a semiconductor-to-metal phase transition near 68 °C expected for crystalline VO₂ particles are recorded by variable-temperature electrical resistance and powder X-ray diffraction measurements.     

Facile and green solvothermal synthesis of palladium nanoparticle-nanodiamond-graphene oxide material with improved bifunctional catalytic properties

We developed a selective solvothermal synthesis of palladium nanoparticles on nanodiamond (ND)–graphene oxide (GO) hybrid material in solution. After the GO and ND materials have been added in PdCl₂ solution, the spontaneous redox reaction between the ND–GO and PdCl₂ led to the creation of nanohybrid Pd@ND@GO material. The resulting Pd@ND@GO material was characterized by X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared (FTIR) spectrometry, scanning electronic microscopy (SEM), and atomic absorption spectrometry methods. The Pd@ND@GO material has been used for the first time as a catalyst for the reduction for 2-nitrophenol and the degradation of methylene blue in the presence of NaBH₄. GO plays the role of 2D support material for Pd nanoparticles, while NDs act as a nanospacer for partly preventing the re-stacking of the GO. The Pd@ND@GO material can lead to high catalytic activity for the reduction reaction of 2-nitrophenol and degradation of methylene blue with 100% conversion within ~15 s for these two reactions even when the content of Pd in it is as low as 4.6 wt%.     

Modifications in band gap and optical properties of Zn0.96−xNd0.04CuxO (x = 0, 0.05, 0.1 and 0.15) nanoparticles

Nd-doped and Nd, Cu co-doped ZnO nanoparticles (Zn_0.96?xNd_0.04Cu_xO, x = 0, 0.05, 0.1 and 0.15) were synthesized by sol–gel method. The structural and optical properties of the samples were investigated by X-ray diffraction (XRD) and UV–visible photo-spectrometer. The synthesized nanoparticles have different microstructure without changing a hexagonal wurtzite structure. CuO phase was noticed in XRD spectra at 38.73° after Cu = 5 % which was formed from remaining un-reacted Cu²⁺ ions. The average crystal size was gradually increased from Cu = 0 % (17 nm) to 15 % (17.6 nm) having lowest value (16.7 nm) at Cu = 5 %. The change in lattice parameters confirmed the substitution of Cu in Zn–Nd–O lattice. The observed constant c/a ratio revealed that there was no change in hexagonal wurtzite structure by Cu-doping. The energy dispersive X-ray spectra confirmed the presence of appropriate amount of Nd and Cu in Zn–O lattice. The optical absorption was increased gradually from Cu = 0–10 % and showed maximum at Cu = 10 % due to the presence of more nucleation centres and defect states. The defects related green band between 487 and 493 nm was due to the oxygen vacancies and intrinsic defects. The higher transmittance (≈ 90 %) noticed at Cu = 15 % leads to the industrial applications. The observed blue shift in energy gap from 3.49 eV (Cu = 0 %) to 3.65 eV (Cu = 10 %) and the red shift from Cu = 10 % (3.65 eV) to Cu = 15 % (3.61 eV) can be explained by the Burstein–Moss effect. Presence of chemical bonding was confirmed by Fourier transform infrared spectra.     

Synthesis and Catalytic Evaluation of Silver Nanoparticles Synthesized with <Emphasis Type="Italic">Aloysia triphylla</Emphasis> Leaf Extract

In this investigation, we report the biosynthesis of the silver nanoparticles using Aloysia triphylla leaves extract. The as-prepared silver nanoparticles were characterized by ultraviolet–visible (Uv–vis) spectroscopy, X-ray diffractometry, scanning electron microscopy and transmission electron microscopy The infrared spectroscopy (FTIR) and Raman spectroscopy techniques were also used to evaluate the chemical groups of the plant extract involved in the silver ions bioreduction. The results indicate that as the plant extract/precursor salt ratio increases, the size of the nanoparticles decreases. Also, as the reaction temperature increases, the reduction rate increased too, resulting in the formation of smaller nanoparticles-size ranges. Uv–vis spectroscopy illustrates absorption peaks in the range of wavelengths of 430–445 nm corresponding to surface plasmon resonance band of silver nanoparticles. The X-ray diffraction (XRD) confirmed the presence of silver solids with fcc structure type. The FTIR analysis showed that the bands corresponding to phenolic compounds and the amide group were involved in the synthesis and stabilization of silver nanoparticles, respectively. The Raman studies showed bands at 1380 and 1610 cm^?1, which correspond to the aromatic and amide compounds, confirming the FTIR results. The Uv–vis results indicate the capacity of silver nanoparticles to reduce the methylene blue.     

Cu-Bi纳米粉体的制备及其可见光光催化性能研究

以Cu（NO3）2、Bi（NO3）3、COfNH）2为原料,聚乙二醇（PEG）为分散剂,采用均匀共沉淀法制备了Cu-Bi催化剂,用X-射线粉末衍射法、能量色散法、透射电镜和紫外－可见漫反射光谱法对催化剂的组成、粒径大小、表面形貌和光学吸收性能进行了详细表征,并以酸性大红和亚甲基蓝为目标降解物,考察了所制备的Cu－Bi催化剂在可见光下的光催化性能。实验结果表明,该催化剂为类球形纳米粉体,粒度均匀,粒径约50nm。在可见光作用下,该催化剂对酸性大红和亚甲基蓝均表现出良好的光催化性能,且在240min前,对酸性大红的降解率要优于亚甲基蓝;240min后则两者的降解效果相近。     

Synthesis of TiO2/Bi2WO6 nanofibers with electrospinning technique for photocatalytic methyl blue degradation

TiO₂/Bi₂WO₆ composite nanofibers have been successfully synthesized by a simple electrospinning process. XRD, SEM, HR-TEM, nitrogen adsorption–desorption isotherms and UV–visible diffuse reflectance spectra were used to characterize the composite nanofibers. The composite fibers with diameters about 100 nm was composed of nanoparticles and possessed of high specific surface area (49.6 m² g^?1) and porous structure. Besides, the TiO₂/Bi₂WO₆ composite nanofibers exhibited excellent visible photocatalytic property in the photodegradation of methylene blue (MB), and over 97.2 % of MB was degraded within 5.5 h.     

Structure and Stability of Gold Nanoparticles Synthesized Using <Emphasis Type="Italic">Schinus molle</Emphasis> L. Extract

In this work, we exhibited the results of the green synthesis of gold nanoparticles by aqueous extract of Schinus molle L. leaves. The chemical reaction was carried out by varying the plant extract/precursor salt ratio concentration in the aqueous solution. The structural characterization of the nanoparticles was performed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). XRD analysis showed that the as-synthesized AuNPs have a face-centered cubic structure. SEM and TEM observations indicated that most of the obtained particles have multiple twinning structures (MTP). The synthesized Au-MTP have particle sizes in the range of 10–60 nm, most of them with an average size of about 24 nm. However, triangular Au plate particles were also obtained, having an average size of 180 nm. Fourier transforms infrared spectroscopy and shows that the functional groups responsible for the chemical reduction of AuNPs are phenolic compounds present in the S. molle L. leaf.     

Green synthesis and characterization of cobalt oxide nanoparticles and its electrocatalytic behavior

Green synthesis of pure cobalt oxide nanoparticles (CoO-NPs) in aqueous medium has been carried out using gelatin. The main advantage of using gelatin as a stabilizing agent is that it provides long-term stability for nanoparticles by preventing particles agglomeration. The particles have been characterized using X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscopy (SEM), energy dispersive X-ray (EADX), and thermogravimetric analysis (TGA). TEM image shows the formation of CoO-NPs with average particle size of 28 nm which agrees well with the XRD data. Cobalt oxide nanoparticles modified carbon paste electrode (CoO-NPs/CPE) displayed excellent electrochemical catalytic activities towards the oxidation of glucose. The electrocatalytic response showed a wide linear range of 7–1000 µM, as well as its experimental limit of detection can be achieved 5.3 µM. The modified electrode for glucose determination is of the property of simple preparation, good stability and high sensitivity.     

Adsorption and Photodegradation of Methylene Blue by Using PAni/TiO2 Nanocomposite

In this study, polyaniline-titanium dioxide (PAni-TiO₂) nanocomposite has been prepared and was utilized as an effective catalyst for photodegradation of methylene blue (MB) dyes from aqueous solution. Adsorption characteristic on the PAni-TiO₂ surface and the aqueous solubility of the dyes also play an important role in the photodegradation of dye. Adsorption and photodegradation process occurs simultaneously on the surface of the catalyst at first adsorption occurs (21.5%) on the outer surface of the catalyst and then photodegrade the material up to (66.5%). In reaction mechanism OH^· makes the vital role to the degradation of methylene blue and its intermediates. To know the surface and stability of the photocatalyst, it was characterized by FTIR, TEM, TGA–DTA, XRD, UV-vis spectrophotometer, and SEM analysis. Kinetic data indicate that up to 20 minutes photodegradation rates usually follows the pseudo-first-order reaction. After 20 minutes, it follows the Langmuir-Hinshelwood (LH) kinetics. Photo reactivity of PAni-TiO₂ was studied with pH of solution, dosage of photocatalyst and concentration of dye. The reaction rate constant (r) and equilibrium binding constant (K) values were incredibly significant than other catalyst.     

Sol–gel process of carbon-supported nickel nanoparticles using different solvents and protecting atmospheres

Carbon-supported nickel nanoparticles have been prepared by a sol–gel process under N₂ or H₂ atmospheres using different solvents such as distilled water, ethanol, acetone and 1-propanol. In the aqueous sol–gel process, nickel nanoparticles with pure face-centered-cubic (fcc) phase can be obtained under N₂ atmosphere by using nickel nitrate, tartaric acid and sodium dodecyl sulfonate. When organic solvents are applied, nickel (Π) acetylacetone is required in order to obtain nickel nanoparticles with pure fcc phase under N₂ atmosphere. When the protecting atmosphere is H₂, nickel nitrate can be used to obtain nickel particles with pure fcc phase. Nickel nanoparticles with grain sizes of 4–6 nm in diameter can be prepared by using nickel (Π) acetylacetone [Ni(acac)₂], citric acid and hexadecylamine with solvent being acetone. 1-propanol is also effective in the preparation of nickel nanoparticles in this sol–gel process. We suggest that this sol–gel may be used for other metallic nanocrystals.     

Immobilization of cellulose extracted from Robinia Pseudoacacia seed fibers onto chitosan: Chemical characterization and study of methylene blue removal

The design of economical adsorbents to remove pollutants from contaminated water is attracting more attention. In this study, cellulose was successfully extracted from Robinia Pseudoacacia seed fibers and immobilized onto chitosan beads. The prepared spherical beads were then used for the biosorption of methylene blue dye from aqueous media. Samples were investigated using several analytical methods, namely FT-IR, XRD, EDX, SEM, and TGA analyses. The adsorption experiments showed that combining cellulose with chitosan improved the removal of methylene blue. The maximum uptake amount of methylene blue using cellulose–chitosan composite beads was 55 mg/g. However, it was about 35 mg/g at 20 °C for chitosan beads. The kinetic data complied strongly with the pseudo-second order equation, suggesting that the biosorption phenomenon has predominantly a chemical nature. Overall, the current study has shown a promising technique to design new adsorbents from abundant natural polymers for eliminating cationic dyes from water.     

A Novel Green Synthesis of Silver Nanoparticles Using Gum Karaya: Characterization,Antimicrobial and Catalytic Activity Studies

Stable silver nanoparticles have been synthesized using gum karaya acting as both reducing and stabilizing agent without using any synthetic reagent. The reaction is performed using water, which is an environmentally safe solvent. This reaction was carried out in an autoclave at a pressure of 15 psi and 120 °C temperature by varying the time. The influence of different parameters such as time, change of concentration of silver nitrate and concentration of gum karaya on the formation of silver nanoparticles has been studied. The synthesized silver nanoparticles are characterized by UV–Vis spectroscopy, FTIR, XRD and TEM. UV–Vis analysis of the sample confirmed the formation of silver nanoparticles exhibiting a sharp peak at a wavelength of 420 nm. TEM micrographs showed the formation of well-dispersed silver nanoparticles of size 2–4 nm. The antimicrobial activity of silver nanoparticles stabilized in gum karaya is tested against Escherichia coli, Micrococcus luteus and is found to be possessing inhibiting property. The silver nanoparticles stabilized in gum karaya exhibited very good catalytic activity and the kinetics of the reaction was found to be pseudo first order with respect to the 4-nitrophenol.     

Synthesis of highly stable silver nanoparticles using imidazolium-based ionic liquid

Highly stable, aqueous dispersions, and hydrophilic ionic liquid-capped silver nanoparticles with positive surface charge were synthesized by in situ reduction of AgNO₃ with NaBH₄ in the presence of an imidazolium-based ionic liquid, viz., 1-dodecyl-3-methylimidazolium chloride ([C₁₂mim][Cl]) at room temperature. Prepared silver nanoparticles were characterized by UV–vis spectra, transmission electron microscopy (TEM), and zeta potential. UV–visible spectrum of the aqueous medium peaked at 407 nm corresponding to the plasmon absorbance of silver nanoparticles. TEM analysis revealed the spherical shape of the particles with sizes about 9 nm and low polydispersed. The surface charge of the synthesized silver nanoparticles was determined as +5.0 mV. The ionic liquid ([C₁₂mim][Cl]) capped silver nanoparticles were stable for at least 8 months.     

Study on Green Synthesis of Gold Nanoparticles and Their Potential Applications as Catalysts

Gold being the most biocompatible metal nanoparticle has become an important biosynthesized drug to be studied in recent field of bioscience. The fungus Aspergillus fischeri has been isolated from fruit crop and thus exploited for the synthesis process. Synthesized GNPs were characterized by UV–visible spectroscopy showed absorption spectra in the range of 530–550 nm at different concentrations of HAuCl4. At the optimum reaction concentration of 1 mM HAuCl4, absorption peak was obtained at 543 nm. The GNPs have been further characterized by X-ray diffraction, FTIR, DLS and TEM analysis. The DLS graph showed that the particles were monodispersed. The TEM image showed the formation of spherical shaped GNPs in the range of 50 nm which was in accordance of the particle size analysis by DLS. The potential applications of the gold nanoparticles are yet to be explored and thus, we have conducted a time dependent comparative catalytic activity for methylene blue degradation of chemically synthesized and biosynthesized GNPs which showed biosynthesized ones are better catalysts than chemical ones.     

Mixed ligand complexes of tungsten(VI) containing aroyl hydrazones and isothiocyanate

Five complexes [WO(NCS)₄L–L] (where L–L = benzoic acid[1-(Furan-2-yl)methylene]hydrazide(BFMH), benzoic acid[(thiophen-2-yl)methylene]hydrazide(BTMH), benzoic acid[1-(thiophen-2-yl)ethylidene]hydrazide(BTEH), benzoic acid(phenylmethylene)hydrazide(BPMH) and benzoic acid[1-(anisol-3-yl) methylene]hydrazide(BAMH)) have been prepared by reaction of ammonium tetraisothiocyanatodioxotungstate(VI) with the corresponding ligand in aqueous medium in the presence of hydrochloric acid. The complexes have been characterized by elemental analysis, molar conductivity, magnetic moment measurements, IR, electronic spectra, thermogravimetric analysis TGA/DTA and ¹H NMR.     

Optimization and detailed stability study on Pb doped ceria nanocubes for enhanced photodegradation of several anionic and cationic organic pollutants

A series of Pb doped CeO₂ nanocubes with seven different Pb loadings (2–12 mol%) were synthesized via modified hydrothermal technique. The prepared samples were characterized by XRD, XPS, FT-IR, TGA, SEM, HR-TEM, EDS and UV–Vis DRS analysis. According to XRD analysis, the crystalline structure of synthesized pure CeO₂ and Pb-doped CeO₂ samples are cubic structure. The ceria nanocubes showed an increase in amount of oxygen vacancies with increasing the dopant concentrations. When the doping level of Pb is 6 mol%, the optical band gap of Pb-CeO₂ is smaller than that of pure CeO₂ nanocubes. The HR-TEM results confirms the cubic structure of 6% Pb-CeO₂ with average crystallite size of about 15 nm. The photocatalytic ability of Pb-CeO₂ catalysts were studied by degrading several anionic and cationic organic pollutants like methylene blue (MB), methylene orange (MO), methylene red (MR), rhodamine B (RhB), reactive blue 160 (RB160), salicylic acid (SA), coumarin and phenol. The 6% Pb-CeO₂ nanocubes shows better photocatalytic performance against anionic dyes especially for MB. To find the optimum condition for better photocatalytic performance of 6% Pb-CeO₂ nanocubes, the photocatalytic process was conducted in different initial reaction conditions like reaction temperature, catalytic dosage, dye concentration and pH of the reaction solution. The stability and recyclability of 6% Pb-CeO₂ photocatalyst was studied by XRD, FT-IR and EDS analysis after 5 cycles of MB degradation. The hydroxyl radical estimation and trapping experiments were conducted to observe the photocatalytic mechanism process in 6% Pb-CeO₂ nanocubes. The perfect doping concentration for better organic pollutant degradation by Pb-CeO₂ is found to be 6 mol% of Pb.     

Methylene blue removal from aqueous solution by magnetic clinoptilolite/chitosan/EDTA nanocomposite

In this study, clinoptilolite as a natural zeolite which was magnetized using precipitation of maghemite nanoparticles was coated by chitosan and then modified by thylenediamine tetra-acetic acid to add functional groups and its performance in the removal of toxic methylene blue from aqueous solution was investigated. Synthesized magnetic nanocomposite was characterized by VSM, XRD, SEM, and FTIR analyses. The saturation magnetization of the final nanocomposite was obtained as 22.2 emu/g. In addition, the factors affecting adsorption process and its optimization were investigated using response surface methodology and central composite design. Data obtained by different isotherm, adsorption kinetic and thermodynamic models were also studied. The results showed good agreement of these data with the Freundlich isotherm model (R ² = 0.99), and it was found that adsorption follows the second-order kinetics model (R ² = 1). Negative values of ΔG and positive values of ΔH obtained from this adsorption thermodynamic study revealed that the methylene blue adsorption process is exothermic and spontaneous. The optimum conditions to ensure maximum adsorption efficiency were determined, and included pH = 5.54, adsorbent amount of 0.03 g, temperature of 31.18 °C, and initial solution concentration of 16.21 mg/l which resulted in a removal efficiency of 99.44%. The results indicated that this nanocomposite can be used as a proper adsorbent for adsorbing methylene blue and other dye contaminants.