Synthesis and characterization of Pd nanoparticle-modified magnetic Sm<Subscript>2</Subscript>O<Subscript>3</Subscript>–ZrO<Subscript>2</Subscript> as effective multifunctional catalyst for reduction of 2-nitrophenol and degradation of organic dyes

In this study, Pd nanoparticle-modified magnetic Sm₂O₃–ZrO₂ material (Pd–Fe₃O₄–Sm₂O₃–ZrO₂) as multifunctional catalyst was fabricated and used for catalytic reduction of 2-nitrophenol compound, degradation of methylene blue and rhodamine B dyes, which are toxic pollutants. The magnetic material was used for the first time as a catalyst for the reduction and degradation studies. Pd nanoparticle-modified magnetic Sm₂O₃–ZrO₂ catalyst was prepared using the deposition–precipitation methods and were characterized by X-ray diffraction, scanning electron microscopy, atomic absorption spectrometry, Raman spectroscopy and BET surface analyzer. The Pd nanoparticle-modified magnetic Sm₂O₃–ZrO₂ material can lead to high catalytic activity for the reduction of 2-nitrophenol and degradation of rhodamine B and methylene blue with >?95% conversion within ~?2 and 80 s even when the content of Pd in it is as low as 5.8 wt%.     

The preparation of new palladium (II) complexes with Schiff base type ligands and its impregnated Al2O3 materials: As the catalysts for degradation/reduction of organic dyes

The removal of organic dyes used in many sectors such as textile, paper, leather, and packaging from water sources is very important in terms of preventing the spread of industrial pollutants to the environment. Transition metal complexes supported to an inorganic solid material are frequently used for the degradation/reduction of organic dyes causing this pollution. In this study, new Pd (II) complexes with Schiff base ligands were synthesized and structurally characterized by nuclear magnetic resonance (NMR), Fourier-transform infrared spectroscopy (FT-IR), mass spectrometry (MS), and single-crystal X-ray diffraction (sc-XRD) spectroscopic methods. Then, the Al₂O₃-impregnated materials of these Pd (II) complexes were prepared and characterized by scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDX), FT-IR, and thermogravimetry (TG) techniques. The catalytic activities of the synthesized Pd (II) complexes and their Al₂O₃-impregnated materials were comparatively analyzed to investigate the degradation/reduction of organic dyes (2-nitroaniline, 4-nitroaniline, 4-nitrophenol, eosin yellow, and methylene blue). The catalytic results indicate that Al₂O₃-impregnated materials are very active catalysts for the degradation/reduction of organic dyes under those circumstances. Conversions of up to 98% for all substrates were obtained after 5 min at ambient temperature.     

Three‐Dimensional Nitrogen‐Doped Reduced Graphene Oxide–Carbon Nanotubes Architecture Supporting Ultrafine Palladium Nanoparticles for Highly Efficient Methanol Electrooxidation

A three‐dimensional (3D) nitrogen‐doped reduced graphene oxide (rGO)–carbon nanotubes (CNTs) architecture supporting ultrafine Pd nanoparticles is prepared and used as a highly efficient electrocatalyst. Graphene oxide (GO) is first used as a surfactant to disperse pristine CNTs for electrochemical preparation of 3D rGO@CNTs, and subsequently one‐step electrodeposition of the stable colloidal GO–CNTs solution containing Na₂PdCl₄ affords rGO@CNTs‐supported Pd nanoparticles. Further thermal treatment of the Pd/rGO@CNTs hybrid with ammonia achieves not only in situ nitrogen‐doping of the rGO@CNTs support but also extraordinary size decrease of the Pd nanoparticles to below 2.0 nm. The resulting catalyst is characterized by scanning and transmission electron microscopy, X‐ray diffraction, Raman spectroscopy, and X‐ray photoelectron spectroscopy. Catalyst performance for the methanol oxidation reaction is tested through cyclic voltammetry and chronoamperometry techniques, which shows exceedingly high mass activity and superior durability.     

Graphene-supported small-sized palladium nanoparticles made by facile photochemical approaches

To achieve small-sized and well-dispersed palladium (Pd) nanoparticles, we make use of effective photochemical approaches to synthesis of clean Pd nanoparticles on the surface of graphene at room temperature. By modulating the photochemical reaction conditions, the size and dispersion of graphene–Pd composites can be well controlled, where PdCl₄²⁻ and graphene oxide (GO) are the reaction precursors, Hantzsch 1,4-dihydropyridine (HEH) is used as an electron donor and an amine-type ligand to stabilize small Pd nanoparticles on the surface of graphene. As a result, the easy and effective photochemical approaches to the graphene–Pd composites with well-dispersed, small-sized Pd nanoparticles and highly conductive reduced GO, are established. Good to excellent yields have also been achieved with the graphene-supported Pd nanoparticles catalysts for the Suzuki coupling reaction.     

A High-Performance Catalytic and Recyclability of Phyto-Synthesized Silver Nanoparticles Embedded in Natural Polymer

The present work deals with phytogenic synthesis of Ag NPs in the natural polymer alginate as support material using Aglaia elaeagnoidea leaf extract as a reducing, capping, and stabilizing agent. Ag nanoparticles embedded in alginate were characterized using UV–Vis absorption spectroscopy, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, transmission electron microscopy techniques and selected area electron diffraction techniques. The formation of AgNPs embedded in the polymer was in spherical shape with an average size of 12 nm range has been noticed. The prepared embedded nanoparticles in polymer were evaluated as a solid heterogeneous catalyst for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) and methylene blue to leuco methylene blue in the liquid phase using sodium borohydride (NaBH₄) as reducing agent. The silver nanoparticles embedded polymer exhibited extraordinary catalytic efficacy in reduction of 4-NP to 4-AP and the rate constant is 0.5054 min^?1 at ambient conditions. The catalyst was recycled and reused up to 10 cycles without significant loss of catalytic activity. The preparation of Ag–CA composite was facile, stable, efficient, eco-friendly, easy to recycle, non-toxic, and cost effective for commercial application.     

Synthesis of Core-Shell (Pd-Au) Bimetallic Nanoparticles in Microemulsions

Palladium-gold core-shell nanoparticles were synthesized in the aqueous domains of water in oil microemulsions by the sequential reduction of H₂PdCl₄ and HAuCl₄. The nanoparticles were characterized by ultraviolet-visible (UV-vis) spectroscopy and transmission electron microscopy (TEM). The UV-vis spectra confirm the presence of palladium nanoparticles after reducing H₂PdCl₄. These particles have been used as seeds for the core-shell particles. UV-vis spectra show that, after reducing HAuCl₄, the surface plasmon absorption of the nanoparticles is dominated by gold, revealing the encapsulation of the palladium seeds. These results agree with crystallographic analysis performed with high-resolution TEM pictures, as well as with selected area electron diffraction. The TEM pictures show the core-shell nanoparticles with an average diameter of 9.1 nm, as compared with 5 nm for the palladium seeds, in good agreement with the used Pd:Au molar ratio.     

Size-Controlled Synthesis of Palladium Nanoparticles

Palladium nanoparticles protected by PVP were obtained first by reducing PdCl₂ with NaBH₄ solution. Then different size palladium nanoparticles with a large size range (1.49 nm ～ 23.26 nm) were prepared by the multi-step reduction of PdCl₂ by hydrogen adsorbed on the surface of palladium nanoparticles. Transmission electron microscopy (TEM) and x-ray diffraction (XRD) were used to characterize the nanoparticles. The increasing value of average diameter from the first to the eighth reduction reaction is about 0.58 nm, from the ninth to the fifteenth reduction reaction the value is about 2.44 nm.     

Synthesis and characterization of magnetic poly(acrylic acid) hydrogel fabricated with cobalt nanoparticles for adsorption and catalytic applications

The present study aimed to synthesize poly(acrylic acid) hydrogel embedded with magnetic cobalt (Co) nanoparticles and to investigate their potential in adsorption and catalysis. The hydrogel was prepared by facile free radical polymerization reaction and Co nanoparticles were fabricated within hydrogel by reducing Co (II) ions using NaBH₄ as reducing agent. Co nanoparticles within hydrogel system imparted magnetic properties to the resulting composite gel and also increased the adsorption capacity. The swelling study of hydrogel was carried out by gravimetric analysis. Different functional groups were identified by Fourier Transform Infrared Spectroscopy and Transmission Electron Microscopy analysis was done to investigate dispersion of Co nanoparticles in hydrogel. The bare hydrogel along with Co nanoparticles loaded gel were tested as adsorbent systems for the removal of a cationic dye (methylene blue) from aqueous solution. 95% removal of methylene blue was achieved with a highest adsorption capacity of 836.5 mg/g of adsorbent. The famous adsorption isotherms were used to evaluate adsorption data. Results showed that Freundlich isotherm model was followed with R² value of 0.95. The hydrogel was also used for catalytic reduction in a toxic pollutant, i.e., 4-nitrophenol. Experimental data for 4-nitrophenol reduction followed pseudo first order kinetics model. Activation energy and apparent rate constant were calculated as 9.24 kJ/mol and 0.24 min⁻¹, respectively. Recycling of the magnetic poly(acrylic acid) hydrogel fabricated with Cobalt nanoparticles was carried out for four consecutive cycles and no significant loss in catalytic activity was observed.

     

Preparation of a novel Fe3O4/graphene oxide hybrid for adsorptive removal of methylene blue from water

In this work, a novel Fe₃O₄/graphene oxide (GO) hybrid was prepared and its removal ability of cationic methylene blue dye from water was investigated. To improve the dispersability of Fe₃O₄/GO hybrid in water, GO was first modified by polyethylene glycol (PEG) via a click approach before deposition of Fe₃O₄ nanoparticles onto its surface. The successful modification of GO surface and the deposition of Fe₃O₄ nanoparticles were confirmed by transmission electron microscopy directly. The saturation magnetization of the resultant Fe₃O₄/GO hybrid is 7.8 eum/g. The adsorption capacities of Fe₃O₄/GO hybrid for methylene blue at 35 and 60°C were as high as 96.05 and 120.05 mg/g, respectively. Moreover, the Langmuir, Freundlich, and Temkin models are used to investigate the isothermal adsorption behavior of Fe₃O₄/GO hybrid.     

Short time deposition of TiO2 nanoparticles on SiC as photocatalysts for the degradation of organic dyes

The deposition of TiO₂ nanoparticles on SiC was carried out by mechanical milling under different conditions. SiC–TiO₂ samples were used as photocatalysts for the degradation of organic dyes such as methylene blue and rhodamine B. A short time deposition of TiO₂ nanoparticles was observed during mechanical milling (2 min at 200 rpm) to cover the SiC particles. The presence of SiC and TiO₂ (anatase and rutile) was confirmed by means of X-ray diffraction after thermal treatment at 450 °C. The deposition of TiO₂ on SiC was corroborated by scanning electron microscopy analysis; the thickness of the thin layer of TiO₂ deposited on SiC increases as the proportion of TiO₂ increases. The energy band gap values obtained for these compounds were around 3.0 eV. SiC–TiO₂ photocatalysts prepared by mechanical milling exhibited better activity under UV-light irradiation for the degradation of methylene blue and rhodamine B than commercial TiO₂ powder (titania P25).     

Pulsed Corona Discharge for Degradation of Methylene Blue in Water

A pulsed corona discharge in multiwire-plate geometry, generated above water was studied for the removal of organic compounds in liquids. The degradation of methylene blue (MB) and the formation of hydrogen peroxide (H₂O₂) were investigated. The MB solution was rapidly decolorized, evidencing the degradation of the dye after approximately 10 min plasma treatment. Nitrate, formate, sulphate and chlorine ions have been detected in the treated solution, explaining partly the change in the solution properties with plasma exposure, i.e. increase of electrical conductivity and decrease of pH. It was found that the concentration of H₂O₂ generated in water increased with plasma exposure time, reaching 200 mg/L after 30 min treatment. In the MB solution less hydrogen peroxide was detected, suggesting reactions with the dye and its degradation products. The addition of FeCl₂ catalyst had a slight favorable effect on methylene blue degradation due to Fenton’s reaction. It was observed that MB and H₂O₂ concentrations continue to decrease after the plasma treatment was stopped, suggesting that active species which accumulate in the solution may react post-plasma with methylene blue and its degradation products.     

Palladium Nanoparticles Embedded into Graphene Nanosheets: Preparation,Characterization, and Nonenzymatic Electrochemical Detection of H2O2

A novel nonenzymatic H₂O₂ sensor based on a palladium nanoparticles/graphene (Pd‐NPs/GN) hybrid nanostructures composite film modified glassy carbon electrode (GCE) was reported. The composites of graphene (GN) decorated with Pd nanoparticles have been prepared by simultaneously reducing graphite oxide (GO) and K₂PdCl₄ in one pot. The Pd‐NPs were intended to enlarge the interplanar spacing of graphene nanosheets and were well dispersed on the surface or completely embedded into few‐layer GN, which maintain their high surface area and prevent GN from aggregating. XPS analysis indicated that the surface Pd atoms are negatively charged, favoring the reduction process of H₂O₂. Moreover, the Pd‐NPs/GN/GCE could remarkably decrease the overpotential and enhance the electron‐transfer rate due to the good contact between Pd‐NPs and GN sheets, and Pd‐NPs have high catalytical effect for H₂O₂ reduction. Amperometric measurements allow observation of the electrochemical reduction of H₂O₂ at 0.5 V (vs. Ag/AgCl). The H₂O₂ reduction current is linear to its concentration in the range from 1×10^?9 to 2×10^?3 M, and the detection limit was found to be 2×10^?10 M (S/N=3). The as‐prepared nonenzymatic H₂O₂ sensor exhibits excellent repeatability, selectivity and long‐term stability.     

Surfactant Assisted Hydrothermal Synthesis of Superparamagnetic ZnFe<Subscript>2</Subscript>O<Subscript>4</Subscript> Nanoparticles as an Efficient Visible-Light Photocatalyst for the Degradation of Organic Pollutant

Super paramagnetic ZnFe₂O₄ nanoparticles were prepared by a surfactant assisted (ethylamine) hydrothermal method along with heat treatment. The nanoparticles were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, high resolution scanning electron microscopy, Transmission electron microscopy, vibrating sample magnetometer and diffuse reflectance spectra technique. From the analyses, influence of calcination temperature on the structural, vibrational, morphological, magnetic and optical properties of ZnFe₂O₄ nanoparticles were investigated. The ZnFe₂O₄ nanoparticles with an average particle size of 17 nm showed high photocatalytic activity in the degradation of methylene blue (90 %). This work demonstrates that ZnFe₂O4 can be used as a potential monocomponent in visible-light photocatalysis for the degradation of organic pollutants. Furthermore, the products were super paramagnetic and could be conveniently separated within 15 min and recycled by using simple magnet, which is very beneficial for the degradation of organic pollutants.     

Synthesis and Electrocatalytic Activity of 3Au?1Pd Alloy Nanoparticles/Graphene Composite for Bisphenol A Detection

In this study, a 3Au? 1Pd alloy nanoparticles/graphene composite (3Au? 1Pd alloy NPs/GN) with carboxyl groups and hydroxyl groups was prepared facilely by co‐reduction of graphene oxide (GO), HAuCl₄, K₂PdCl₄, with an Au? Pd alloy molar ratio of 3 : 1. The composite modified glass carbon electrode (GCE) showed a good performance for detecting bisphenol A (BPA) due to the enhanced electron transfer kinetics and large active surface area. The effective enrichment of BPA is attributed to the carboxyl groups and hydroxyl groups on the composite. According to the results of differential pulse voltammetry (DPV), the BPA oxidation current is linear to its concentration in the range of 10 nM–5.0 µM (R=0.998), and the detection limit is found to be 4.0 nM (S/N=3).     

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.     

A simple and greener approach for the synthesis of PVC supported Pd (0): application to Heck and Sonogashira reactions in water

Preparation of PVC-supported Pd nanoparticles through the reduction of PdCl₂ by a non-toxic and eco-friendly route, employing sodium formate and NaOH in ethanol–water system has been described. The prepared PVC supported Pd nanoparticles were employed as catalyst in the cross coupling reactions, that is, Heck and Sonogashira reactions in water medium to afford the respective products in good to excellent yields.     

Cu-石墨烯类Fenton催化剂的制备及催化活性

通过一步水热法制备了Cu-石墨烯（Cu-RGO）催化剂,实现了Cu纳米颗粒的可控生长和氧化石墨烯（GO）还原的同步进行,并将所制备的Cu-RGO用于亚甲基蓝（MB）的催化降解研究。在H₂O₂存在条件下,当GO与Cu的质量比为3：17时,经过4h催化反应,Cu-RGO催化剂对亚甲基蓝的降解率可达到99.5%,经过6次循环使用对亚甲基蓝的降解率仍保持在98.1%以上,Cu-RGO催化剂展现了较高的催化活性及良好的稳定性。     

Enhanced adsorption of methylene blue onto graphene oxide-doped XFe<Subscript>2</Subscript>O<Subscript>4</Subscript> (X = Co,Mn, Ni) nanocomposites: kinetic,isothermal, thermodynamic and recyclability studies

The nanocomposites XFe₂O₄/GO with various metal sites (X = Co, Mn, and Ni) were successfully synthesized via the polymerized complex method. The XFe₂O₄/GO family was characterized using X-Ray diffraction analysis, scanning electron microscopy (SEM), and a vibrating sample magnetometer. We also investigated the effect of three fundamental parameters (initial concentration, dosage, and pH) on the removal of methylene blue using the response surface methodology. A high F value, very low P value (< 0.00001), a non-significant lack of fit, and the determination coefficient (R ² > 0.95) demonstrated a strong correlation between experimental and predicted values of the responses. The predicted optimal conditions for maximum removal efficiency were easily determined to adhere to the following trend for actual test experiments: MnFe₂O₄/GO (60.1%) < CoFe₂O₄/GO (80.3%) < NiFe₂O₄/GO (87.7%). Moreover, the adsorption behavior was well-described by the Langmuir isotherm and a pseudo-second-order kinetic model. The maximum capacity for adsorption of methylene blue onto XFe₂O₄/GO was found from 42.2 to 80.6 mg/g. Moreover, the XFe₂O₄/GO could be regenerated for several cycles without a considerable decrease in removal yield, suggesting that this highly promising XFe₂O₄/GO could be applied as an efficient and novel adsorbent.     

Cu-石墨烯类Fenton催化剂的制备及催化活性

通过一步水热法制备了Cu-石墨烯(Cu-RGO)催化剂,实现了Cu纳米颗粒的可控生长和氧化石墨烯(GO)还原的同步进行,并将所制备的Cu-RGO用于亚甲基蓝(MB)的催化降解研究。在H2O2存在条件下,当GO与Cu的质量比为3∶17时,经过4 h催化反应,Cu-RGO催化剂对亚甲基蓝的降解率可达到99.5%,经过6次循环使用对亚甲基蓝的降解率仍保持在98.1%以上,CuRGO催化剂展现了较高的催化活性及良好的稳定性。     

Intermetallic PdBi aerogels with improved catalytic performance for the degradation of organic pollutants in water

It is always highly pursued to develop efficient and durable catalysts for catalytic applications. Herein, intermetallic PdBi aerogels with tunable activity were prepared successfully via a surfactant-free spontaneous gelation process. The prepared PdBi aerogels have a three-dimensional high porous structure and plentiful active sites pervaded on the ultrathin interlinked nanowires network. These unique structures, as well as the synergistic effect between Pd and Bi, can accelerate mass and electron transfer, and improve the atom utilization ratio of Pd atoms to promote the catalytic efficiency. As a proof-of-concept application, the optimized Pd₂Bi₁ aerogels exhibit 4.2 and 6.2 times higher catalytic activity for the reduction of 4-nitrophenol (4-NP) and methylene blue (MB) than those of commercial Pd/C, respectively. With the introduction of non-noble metal of Bi, the cost of the resulted PdBi aerogels can be dropped significantly while the catalytic capability of PdBi aerogel will be improved sharply. This strategy will bring good hints to rationally design fine catalysts for various applications.