One-step synthesis of hollow porous gold nanoparticles with tunable particle size for the reduction of 4-nitrophenol

Hollow porous gold nanoparticles (HPGNPs) were synthesized via a one-step solution phase method at ambient temperature. The particle size, ranging from 80nm to 350nm, was easily controlled by changing the concentration of HAuCl4. The morphology and the structure of the as-prepared HPGNPs were investigated by SEM, TEM, HRTEM and XPS. Langmuir isotherm analysis yielded values of 8973m(2)/g for the outer surface area and 58724m(2)/g for the inner surface area for the 80nm HPGNPs. Due to a special hollow porous nanostructure, the HPGNPs exhibited superior catalytic activity and stability for the reduction of 4-nitrophenol (4-NP). No significant inactivation of the 80nm HPGNPs was observed, even after recycling for six cycles or storing for more than 1 month. Due to these excellent properties, it is expected that HPGNPs can be used in such applications as water pollutant removal and environmental remediation.

Enhanced Activity of Supported Ni Catalysts Promoted by Pt for Rapid Reduction of Aromatic Nitro Compounds

To improve the activities of non-noble metal catalysts is highly desirable and valuable to the reduced use of noble metal resources. In this work, the supported nickel (Ni) and nickel-platinum (NiPt) nanocatalysts were derived from a layered double hydroxide/carbon composite precursor. The catalysts were characterized and the role of Pt was analysed using X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), energy dispersive X-ray spectroscopy (EDS) mapping, and X-ray photoelectron spectroscopy (XPS) techniques. The Ni²⁺ was reduced to metallic Ni⁰ via a self-reduction way utilizing the carbon as a reducing agent. The average sizes of the Ni particles in the NiPt catalysts were smaller than that in the supported Ni catalyst. The electronic structure of Ni was affected by the incorporation of Pt. The optimal NiPt catalysts exhibited remarkably improved activity toward the reduction of nitrophenol, which has an apparent rate constant (K_a) of 18.82 × 10⁻³ s⁻¹, 6.2 times larger than that of Ni catalyst and also larger than most of the reported values of noble-metal and bimetallic catalysts. The enhanced activity could be ascribed to the modification to the electronic structure of Ni by Pt and the effect of exposed crystal planes.

A ternary Cu2O-Cu-CuO nanocomposite: a catalyst with intriguing activity

In this work, the syntheses of Cu2O as well as Cu(0) nanoparticle catalysts are presented. Copper acetate monohydrate produced two distinctly different catalyst particles with varying concentrations of hydrazine hydrate at room temperature without using any surfactant or support. Then both of them were employed separately for 4-nitrophenol reduction in aqueous solution in the presence of sodium borohydride at room temperature. To our surprise, it was noticed that the catalytic activity of Cu2O was much higher than that of the metal Cu(0) nanoparticles. We have confirmed the reason for the exceptionally high catalytic activity of cuprous oxide nanoparticles over other noble metal nanoparticles for 4-nitrophenol reduction. A plausible mechanism has been reported. The unusual activity of Cu2O nanoparticles in the reduction reaction has been observed because of the in situ generated ternary nanocomposite, Cu2O-Cu-CuO, which rapidly relays electrons and acts as a better catalyst. In this ternary composite, highly active in situ generated Cu(0) is proved to be responsible for the hydride transfer reaction. The mechanism of 4-nitrophenol reduction has been established from supporting TEM studies. To further support our proposition, we have prepared a compositionally similar Cu2O-Cu-CuO nanocomposite using Cu2O and sodium borohydride which however displayed lower rate of reduction than that of the in situ produced ternary nanocomposite. The evolution of isolated Cu(0) nanoparticles for 4-nitrophenol reduction from Cu2O under surfactant-free condition has also been taken into consideration. The synthetic procedures of cuprous oxide as well as its catalytic activity in the reduction of 4-nitrophenol are very convenient, fast, cost-effective, and easily operable in aqueous medium and were followed spectrophotometrically. Additionally, the Cu2O-catalyzed 4-nitrophenol reduction methodology was extended further to the reduction of electronically diverse nitroarenes. This concise catalytic process in aqueous medium at room temperature revealed an unprecedented catalytic performance which would draw attention across the whole research community.

Porous CuO nanostructure as a reusable catalyst for oxidative degradation of organic water pollutants

Porous CuO nanostructure exhibits high catalytic activity for the degradation of methylene blue and methyl orange in the presence of H₂O₂.

In situ generated nickel on cerium oxide nanoparticle for efficient catalytic reduction of 4-nitrophenol

Absorption spectra recorded using UV-visible spectrometer during the reduction process of 4-nitrophenol to 4-aminophenol in the presence of reducing agent (NaBH₄) and catalyst (Ni(NO₃)₂/CeO₂).

Flow hydrogenation of p-nitrophenol with nano-Ag/Al2O3

Herein, we report the first continuous-flow hydrogenation of p-nitrophenol to p-aminophenol with molecular hydrogen, as a reducting agent.

Shape-controlled synthesis of 3D copper nicotinate hollow microstructures and their catalytic properties

View of the process of preparation and catalysis of Cu hollow microstructures.

Sulfuric disazo dye stabilized copper nanoparticle composite mixture: synthesis and characterization

A copper nanoparticle–sulfuric disazo dye (Cu–SD1) composite was synthesized using the sol–gel method.

Self-assembly of porous copper oxide hierarchical nanostructures for selective determinations of glucose and ascorbic acid

CuO with flower and hallow sphere-like morphology were fabricated via one pot hydrothermal method. The effect of copper ions source upon the CuO nanostructures assembly, selectivity and sensitivity in the electrochemical processes is explored.

Simultaneous catalytic degradation/reduction of multiple organic compounds by modifiable p(methacrylic acid-co-acrylonitrile)–M (M: Cu, Co) microgel catalyst composites

The reactants easily diffuse into a microgel network, adsorb at the surface of catalyst nanoparticles and reduce in the presence of reducing agents.

Facile synthesis and characterization of beta lactoglobulin–copper nanocomposites having antibacterial applications

The synthesis of Cu⁰ nanoparticles and Cu–protein nanocomposites is a great challenge.

Solvent-thermal preparation of a CuCo2O4/RGO heterocomposite: an efficient catalyst for the reduction of p-nitrophenol

The catalytic activity of an as-synthesized CuCo₂O₄/RGO composite was researched in the reduction of p-nitrophenol to p-aminophenol by NaBH₄, which exhibited complete conversion in 6 min.

Nitroarene reduction: a trusted model reaction to test nanoparticle catalysts

Nitrophenol reduction to aminophenol with a reducing agent is conveniently carried out in aqueous medium mainly with a metal or metal oxide catalyst. This reduction is presently considered as a benchmark reaction to test a catalyst nanoparticle. Thousands of original reports have enriched this field of nanoparticle catalyzed reaction. Synthesis of different metal and metal oxide nanoparticles and their composites along with their role as catalysts for nitrophenol reduction with varying reducing agents have been elucidated here. The progress of the reaction is conveniently monitored by UV-visible spectrophotometry and hence it becomes a universally accepted model reaction. In this review we have discussed the reaction kinetics considering its elegance and importance enlightening the long known Langmuir-Hinshelwood mechanism and Eley-Rideal mechanism at length, along with a few other mechanisms recently reported. A brief description of the synthetic procedures of various nanoparticles and their respective catalytic behaviour towards nitroarene reduction has also been accounted here.

Versatile hierarchical Cu/Fe3O4 nanocatalysts for efficient degradation of organic dyes prepared by a facile, controllable hydrothermal method

A novel monodispersed hierarchical nanocomposite catalyst, Cu/Fe₃O₄, aimed at efficient degradation of traditional dyes, was successfully synthesized through a short-time, facile, eco-friendly hydrothermal method.

A study of the catalytic ability of in situ prepared AgNPs–PMAA–PVP electrospun nanofibers

The catalysis of nanomaterials is interesting and attractive. Herein, electrospinning was employed to afford poly(methyl acrylate) (PMAA)–poly(vinyl pyrrolidone) (PVP) electrospun nanofibers.

An efficient Ag-nanoparticle embedded semi-IPN hydrogel for catalytic applications

Silver nanoparticle embedded semi-IPN hydrogels based on a combination of poly(acrylamide) and poly(aspartic acid) for catalytic application.

Synthesis of dendrimer-templated Pt nanoparticles immobilized on mesoporous alumina for p-nitrophenol reduction

Dendrimer-templated mesoporous alumina-supported Pt nanocatalysts were prepared and used to catalyze reduction reaction after calcination at different temperatures in nitrogen.

Synthesis of copper oxide/reduced graphene oxide nanocomposite and its enhanced catalytic activity towards reduction of 4-nitrophenol

Graphene oxide (GO) and its derivatives have attracted extensive interest in many fields, including catalytic chemistry, organic synthesis, and electrochemistry.

Synthesis of high surface area mixed metal oxide from the NiMgAl LDH precursor for nitro-aldol condensation reaction

NiMgAl mixed oxide catalyzes nitro-aldol condensation reaction at room temperature under solvent free conditions exhibiting 99% conversion.

In situ synthesis of environmentally benign montmorillonite supported composites of Au/Ag nanoparticles and their catalytic activity in the reduction of p-nitrophenol

Montmorillonite clay supported in situ synthesized metal nanoparticles with catalytic activity was provided.

Controllable synthesis of Ni/SiO2 hollow spheres and their excellent catalytic performance in 4-nitrophenol reduction

Hierarchical Ni nanoparticle supported silica hollow microspheres were synthesized by a unique and simple two-step method. Excellent catalytic activity in the reduction of 4-nitrophenol can be achieved on the catalysts.