Facile synthesis of highly dispersed palladium/polypyrrole nanocapsules for catalytic reduction of p-nitrophenol

In Situ Construction of Co-MoS2/Pd Nanosheets on Polypyrrole-Derived Nitrogen-Doped Carbon Microtubes as Multifunctional Catalysts with Enhanced Catalytic Performance

The structural design of multiple functional components could integrate synergistic effects to enhance the catalytic performance of MoS₂-based composites for catalytic applications. Herein, one-dimensional (1D) Co-MoS₂/Pd@NCMTs composites were designed to prepare Co-doped MoS₂/Pd nanosheets (NSs) on N-doped carbon microtubes (NCMTs) from tubular polypyrrole (PPy) as multifunctional catalysts. The Co-MoS₂/Pd@NCMTs composites integrated the synergistic effects of Co-doping, a 1D tubular structure, and noble-metal Pd decoration. Thus, a higher catalytic activity was observed in 4-nitrophenol (4-NP) reduction and peroxidase-like catalysis than other components, such as MoS₂, MoS₂@NCMTs, and Co-MoS₂@NCMTs. Remarkably, the results indicated that the dissolution, diffusion, and redistribution led to the dissolution of MoO₃@ZIF-67 cores and generation of Co-doped MoS₂ NSs. Benefiting from the synergistic effect from these components, Co-MoS₂/Pd@NCMTs were considered as a facile colorimetric sensing platform for detecting tannic acid. Moreover, outstanding performance was realized in the reduction of 4-NP with the composites. Thus, we provide a simple synthetic strategy for simultaneously integrating electronic engineering and structural advantages to develop an efficient MoS₂-based multifunctional catalyst.

A Rotavirus Virus-Like Particle Confined Palladium Nanoreactor and Its Immobilization on Graphene Oxide for Catalysis

Abstract

In this work, a new viral protein cage based nanoreactor was successfully constructed via encapsulating Tween 80 stabilized palladium nanoparticles (NPs) into rotavirus capsid VP2 virus-like particles (i.e. Pd@VP2). The effects of stabilizers including CTAB, SDS, Tween 80 and PVP on controlling the particle size of Pd NPs were investigated. They were further immobilized on graphene oxide (i.e. Pd@VP2/GO) by a simple mixing method. Some characterizations including FT-IR and XPS were conducted to study adsorption mode of Pd@VP2 on GO sheets. Their catalytic performance was estimated in the reduction of 4-nitrophenol (4-NP). Results showed that Tween 80 stabilized Pd NPs with the molar ratio of Pd to Tween 80 at 1:0.1 possessed the smallest size and the best stability as well. They were encapsulated into viral protein cages (mean size 49 ± 0.26 nm) to assemble confined nanoreactors, most of which contained 1-2 Pd NPs (mean size 8.15 ± 0.26 nm). As-prepared Pd@VP2 indicated an enhanced activity (apparent reaction rate constant k _app  = (3.74 ± 0.10) × 10^-3 s^-1) for the reduction of 4-NP in comparison to non-confined Pd-Tween80 colloid (k _app  = (2.20 ± 0.06) × 10^-3 s^-1). It was logically due to confinement effects of Pd@VP2 including high dispersion of Pd NPs and high effective concentration of substrates in confined space. Pd@VP2 were further immobilized on GO surface through C-N bond. Pd@VP2/GO exhibited good reusability after recycling for four runs, confirming the strong anchoring effects of GO on Pd@VP2.

Graphic Abstract

Highly efficient and magnetically recyclable Pd catalyst supported by iron-rich fly ash@fly ash-derived SiO2 for reduction of p-nitrophenol

In this study, a magnetically recyclable Pd catalyst was developed by using the novel support of iron-rich coal fly ash/silica (IRFA@SiO₂) for highly efficient reduction of p-nitrophenol (p-NP). IRFA microspheres were coated with amorphous SiO₂ synthesized from non-magnetic coal fly ash (NMFA) and then loaded with Pd by impregnation method for the synthesis of Pd/IRFA@SiO₂. Various surface analyses demonstrated that amorphous SiO₂ was well deposited on the surface of IRFA, providing a unique three-dimensionally structured SiO₂ layer to suppress aggregation of IRFA and enhance dispersion of Pd nanoparticles. Pd/IRFA@SiO₂ exhibited a significantly enhanced p-NP reduction than those of Pd/IRFA, Pd/Al₂O₃, and Pd/SiO₂. Compared to other Pd- and metal-loaded catalysts, Pd/IRFA@SiO₂ showed ˜4000× enhancements in k_obs-p-NP/C_M (L min^-1 g_M^-1, M = precious metals) values and ˜3800× increases in price-normalized k_obs-p-NP values, indicating that Pd/IRFA@SiO₂ is a highly efficient and cost-effective alternative catalyst. The catalyst was successfully recycled five times without significant leaching of Pd, Si, and heavy metals because of the magnetic property of Pd/IRFA@SiO₂. The experimental results suggest the applicability of the surface-modified IRFA support for the development of novel magnetically recoverable catalysts without severe toxicity problems.

An efficient thin-walled Pd/polypyrrole hybrid nanotube biocatalyst for sensitive detection of ascorbic acid

Controllable fabrication of novel and uniform noble metal nanoparticles on a specific support with a superior catalytic or electrocatalytic performance is of significantly importance for practical applications. In this report, we demonstrated an effective way to fabricate uniform thin-walled Pd/polypyrrole (PPy) hollow nanotubes. The prepared Pd/PPy hybrid nanotubes exhibited an excellent peroxidase-like activity to oxidize a typical peroxidase substrate such as 3,3',5,5'-tetramethylbenzidine in comparison with traditional Pd/C and Pd black catalysts. The outstanding catalytic activity of the Pd/PPy hybrid nanotubes for peroxidase mimicking could be resulting from their unique hollow characteristic and an interfacial effect between PPy and Pd components. Based on the favorable catalytic property of the Pd/PPy hybrid nanotubes, a convenient and rapid colorimetric way to sensitively determine ascorbic acid has been presented. The detection limit was around 0.062 μM and an excellent selectivity was also achieved. The developed detection system in this study could be extended to the fields of bioscience and biotechnology with promising prospects.

Sonochemical synthesis of Fe3O4@NH2-mesoporous silica@Polypyrrole/Pd: A core/double shell nanocomposite for catalytic applications

There is a growing interest in sonochemistry for either the controlled design of nanostructured materials or for the synthesis of polymers and polymer composites. It is fast and highly efficient method that provides materials with exceptional and enhanced structural and chemical properties. Herein, we take advantage of the versatile sonochemical process in order to design core/double layered shell nanocomposite denoted by Fe₃O₄@NH₂-mesoporous silica@ PPy/Pd. This magnetic, multicomponent material was designed in a three-step sono-process: (i) synthesis of magnetic core, (ii) cure of mesoporous silica, and (iii) sonochemical deposition of PPy/Pd. This last step was achieved within 1 h, a much shorter duration compared to conventional routes which usually take several hours to few days. The final nanocomposite can be recovered with a simple magnetic stick. X-ray diffraction patterns highlighted the presence of zerovalent palladium on the surface of the magnetic nanocomposite. The catalytic activity of the solid support was investigated by the study of the p-nitrophenol (p-NP) reduction and the Methyl Orange (MO) degradation in aqueous media. Results showed a very high catalytic efficiency, a high conversion yield of p-NP into 4-aminophenol (more than 94%) and an almost entire degradation of MO (99%) with a fast kinetics fitting to the first order model. This work demonstrates conclusively the benefits of sonochemistry in the design of metal nanoparticle-decorated inorganic/polymer hybrid system with outstanding performances.

Synthesis of silver-anchored polyaniline–chitosan magnetic nanocomposite: a smart system for catalysis

A novel and smart four component system composed of chitosan, polyaniline, magnetite and silver was exploited for catalysis.

NH2- or PPh2-functionalized linkers for the immobilization of palladium on magnetite nanoparticles?

The influence of the linker in the immobilization of Pd NPs on magnetic NPs has been demonstrated.

Highly water-dispersible magnetite-supported Pd nanoparticles and single atoms as excellent catalysts for Suzuki and hydrogenation reactions

The linker dpa enables the deposition of palladium on magnetite nanoparticles that show excellent catalytic behavior in water or water/ethanol solvents.

Chain-like Fe3O4@resorcinol-formaldehyde resins–Ag composite microstructures: facile construction and applications in antibacterial and catalytic fields

Chain-like Fe₃O₄@RF–Ag microstructures with excellent antibacterial and catalytic activities were constructed by a simple two-step route.

NiCo nanotubes plated on Pd seeds as a designed magnetically recollectable catalyst with high noble metal utilisation

The tailored structure of a bifunctional, semi-homogeneous NiCo-nanotube catalyst system with embedded Pd nanoparticles, is synthesised by electroless plating.

Investigating the Dispersion Behavior in Solvents, Biocompatibility, and Use as Support for Highly Efficient Metal Catalysts of Exfoliated Graphitic Carbon Nitride

The liquid-phase exfoliation of graphitic carbon nitride (g-C3N4) to afford colloidal dispersions of two-dimensional flakes constitutes an attractive route to facilitate the processing and implementation of this novel material toward different technological applications, but quantitative knowledge about its dispersibility in solvents is lacking. Here, we investigate the dispersion behavior of exfoliated g-C3N4 in a wide range of solvents and evaluate the obtained results on the basis of solvent surface energy and Hildebrand/Hansen solubility parameters. Estimates of the three Hansen parameters for exfoliated g-C3N4 from the experimentally derived data yielded δD ≈ 17.8 MPa(1/2), δP ≈ 10.8 MPa(1/2), and δH ≈ 15.4 MPa(1/2). The relatively high δH value suggested that, contrary to the case of other two-dimensional materials (e.g., graphene or transition metal dichalcogenides), hydrogen-bonding plays a substantial role in the efficient interaction, and thus dispersibility, of exfoliated g-C3N4 with solvents. Such an outcome was attributed to a high density of primary and/or secondary amines in the material, the presence of which was associated with incomplete condensation of the structure. Furthermore, cell proliferation tests carried out on thin films of exfoliated g-C3N4 using murine fibroblasts suggested that this material is highly biocompatible and noncytotoxic. Finally, the exfoliated g-C3N4 flakes were used as supports in the synthesis of Pd nanoparticles, and the resulting hybrids exhibited an exceptional catalytic activity in the reduction of nitroarenes.

Templated assembly of BiFeO₃ nanocrystals into 3D mesoporous networks for catalytic applications

The self-assembly of uniform nanocrystals into large porous architectures is currently of immense interest for nanochemistry and nanotechnology. These materials combine the respective advantages of discrete nanoparticles and mesoporous structures. In this article, we demonstrate a facile nanoparticle templating process to synthesize a three-dimensional mesoporous BiFeO₃ material. This approach involves the polymer-assisted aggregating assembly of 3-aminopropanoic acid-stabilized bismuth ferrite (BiFeO₃) nanocrystals followed by thermal decomposition of the surfactant. The resulting material consists of a network of tightly connected BiFeO₃ nanoparticles (∼6-7 nm in diameter) and has a moderately high surface area (62 m(2) g(-1)) and uniform pores (ca. 6.3 nm). As a result of the unique mesostructure, the porous assemblies of BiFeO₃ nanoparticles show an excellent catalytic activity and chemical stability for the reduction of p-nitrophenol to p-aminophenol with NaBH4.

4-Mercaptophenyldiphenylphosphine as linker to immobilize Pd onto the surface of magnetite nanoparticles. Excellent catalytic efficiency of the system after partial linker removal

The catalytic efficiency of Pd nanoparticles supported on Fe₃O₄ NPs strongly improves after partial removal of the Sdp linker.

Gold nanoparticle modified magnetic fibrous silica microspheres as a highly efficient and recyclable catalyst for the reduction of 4-nitrophenol

Au nanoparticles were immobilized on magnetic fibrous silica microspheres as highly active and recyclable nanocatalysts for the catalytic reduction of 4-nitrophenol to 4-aminophenol.

Pd nanoparticles partially embedded in the inner wall of nitrogen-doped carbon hollow spheres as nanoreactors for catalytic reduction of 4-nitrophenol

Pd@nitrogen-doped carbon nanoreactors (Pd@NC) were synthesized by partially embedding small Pd nanoparticles in the inner wall of the nitrogen-doped carbon shells. Such embedment is critical for improving catalytic activity and stability.

Highly facile and efficient assembly of palladium nanoparticles on polystyrene microspheres and their application in catalysis

Herein we develop a facile and effective strategy for the synthesis of composite particles composed of polystyrene microspheres decorated with palladium nanoparticles, which exhibited excellent catalytic activity and stability towards the reduction of p-nitrophenol by NaBH₄.

Controllable synthesis of core–satellite Fe3O4@polypyrrole/Pd nanoarchitectures with aggregation-free Pd nanocrystals confined into polypyrrole satellites as magnetically recoverable and highly efficient heterogeneous catalysts

A soft template-assisted redox strategy has been developed to fabricate core–satellite Fe₃O₄@PPy/Pd nanocomposites as efficient nanocatalysts for reduction of nitroaromatics.