Ultrasmall Palladium Nanoparticles Research Articles

Nanodiamond Supported Ultra-Small Palladium Nanoparticles as an Efficient Catalyst for Suzuki Cross-Coupling Reactions

A nanocatalyst comprising ultra-small palladium nanoparticles supported on nanodiamonds (ultra-small Pd/rNDs) was fabricated via a reduction of palladium (II) salt on oxidized nanodiamond. The prepared catalyst was characterized using XRD, XPS, ICP-MS, AAS, and TEM/HRTEM techniques, including STEM-EDS chemical mapping, which revealed that the modified material is a combination of reduced nanodiamond decorated with palladium nanoparticles. The as-prepared and well-characterized ultra-small Pd supported on rNDs displayed superb catalytic activity for Suzuki–Miyaura cross-coupling reactions at low temperature without any toxic solvents, to obtain the respective products in good-to-excellent yields (75–98%). The catalyst was easily separated from the reaction solution and was reused four times without loss of catalytic activity or chemical stability.

Ultrasmall Palladium Nanoparticles Confined within Dendronized Polymers as High-Efficiency Catalysts

Ultrasmall Palladium Nanoparticles Confined within Dendronized Polymers as High-Efficiency Catalysts

Polydopamine-Pd nanozymes as potent ROS scavengers in combination with near-infrared irradiation for osteoarthritis treatment

Excessive reactive oxygen species (ROS) in joints could lead to gradual degeneration of the extracellular matrix (ECM) and apoptosis of chondrocytes, contributing to the occurrence and development of osteoarthritis (OA). Mimicking natural enzymes, polydopamine (PDA)-based nanozymes showed great potential in treating various inflammatory diseases. In this work, PDA loaded with ultra-small palladium (PDA-Pd) nanoparticles (NPs) was employed to scavenge ROS for OA therapy. As a result, PDA-Pd effectively declined the intracellular ROS levels and exhibited efficient antioxidative and anti-inflammatory capacity with good biocompatibility in IL-1β stimulated chondrocytes. Significantly, assisted with near-infrared (NIR) irradiation, its therapeutic effect was further enhanced. Further, NIR-stimulated PDA-Pd suppressed the progression of OA after intra-articular injection in the OA rat model. With favorable biocompatibility, PDA-Pd exhibits efficient antioxidative and anti-inflammatory capacity, leading to the alleviation of OA in rats. Our findings may provide new insights into the treatment of various ROS-induced inflammatory diseases.

Organo-Nanocups Assist the Formation of Ultra-Small Palladium Nanoparticle Catalysts for Hydrogen Evolution Reaction.

Ultra-small palladium nanoparticles were synthesized and applied as catalysts for a hydrogen evolution reaction. The palladium metal precursor was produced via beta-cyclodextrin as organo-nanocup (ONC) capping agent to produce ultra-small nanoparticles used in this study. The produced ~3 nm nanoparticle catalyst was then characterized via X-ray diffraction (XRD), transmission electron microscopy (TEM), ultraviolet-visible spectroscopy (UV-Vis), and Fourier transform infrared spectroscopy (FTIR) to confirm the successful synthesis of ~3 nm palladium nanoparticles. The nanoparticles’ catalytic ability was explored via the hydrolysis reaction of sodium borohydride. The palladium nanoparticle catalyst performed best at 303 K at a pH of 7 with 925 μmol of sodium borohydride having an H2 generation rate of 1.431 mL min−1 mLcat−1. The activation energy of the palladium catalyst was calculated to be 58.9 kJ/mol.

The Ultrasmall Palladium Nanoparticles Catalyzed Telomerization of CO2 with 1,3‐Butadiene at Room Temperature: Selective Synthesis of δ‐Lactone

AbstractAn efficient method for the selective synthesis of δ‐lactone from CO2 and 1,3‐butadiene was developed by using ultrasmall palladium nanoparticles as a catalyst for the first time. Palladium nanoparticles (1.90±0.39 nm) were generated in situ in the presence of Pd(acac)2, tetrabutylammonium acetate (TBAAc), and PPh3 as the precatalyst, stabilizer, and reductant, respectively. Maximum yield (86 % with 96 % selectivity) with satisfactory conversion (89 %) and turnover number (1271) was achieved under mild conditions.

In-situ confinement of ultrasmall palladium nanoparticles in silicalite-1 for methane combustion with excellent activity and hydrothermal stability

Maximizing the use of palladium without compromises in catalytic activity and stability in the combustion of methane is extremely challenging due to the harsh operation conditions. To achieve this goal, a series of core-shell-structured catalysts with different amounts of palladium nanoparticles confined in hydrophobic silicalite-1 (Pd@S-1) was designed. Unexpectedly, a volcanic trend between catalytic activity and palladium loading was found as the loading increased from 0.3 wt% to 1.6 wt%, among which the 0.6 wt%Pd@S-1 exhibited the highest catalytic activity with a complete combustion temperature of 380 °C. Besides, the 0.6 wt%Pd@S-1 showed an ultrahigh stability in the high temperature applications due to the spatial confinement of palladium inside the rigid zeolite matrix. Moreover, owing to the hydrophobicity of the pure silica zeolite, the Pd@S-1 could selectively hinder the diffusion of water vapor into the palladium sites, leading to the outstanding water-resistance ability.

Scalable α-Arylation of Nitriles in Aqueous Micelles using Ultrasmall Pd Nanoparticles: Surprising Formation of Carbanions in Water

A scalable synthetic method is described for both the preparation of ultrasmall palladium nanoparticles and their subsequent use in catalyzing an α-arylation reaction of nitriles in aqueous micelle...

PVP-PS supported ultra-small Pd nanoparticles for the room temperature reduction of 4-nitrophenol

A facile method for the synthesis of ultra-small palladium (Pd) nanoparticles by polyol method is described. Pd nanoparticles are stabilized/caped by poly(N-vinylpyrrolidone) (PVP) and PVP capped Pd nanoparticles encapsulated by polystyrene. The resulting nanocatalyst was investigated for catalytic reduction of 4-nitrophenol under ambient conditions. Optimized reactions conditions showed that 20 mg of the catalyst and 1.0 M NaBH4 are the ideal conditions to achieve the best activity.

Formation and stabilization of colloidal ultra-small palladium nanoparticles on diamine-modified Cr-MIL-101: Synergic boost to hydrogen production from formic acid

Ultra-small nano-sized palladium particles were successfully stabilized within the pores of diamine groups grafted open metal site metal-organic frameworks of Cr-MIL-101; coordinated diamine groups of ethylene diamine (ED) and propyl diamine (PD) on the active site of chromium units of Cr-MIL-101. The physiochemical properties of the Pd@Cr-MOFs were investigated using FTIR, XRD, SEM/EDX mapping, TEM, BET, and AAS. The Cr-MIL-101 stabilized ultra-small Pd nanoparticles, Pd@(ethylene diamine)/Cr-MIL-101, and Pd@(propyl diamine)/Cr-MIL-101, displayed catalytic activity for clean dehydrogenation of formic acid and generation of hydrogen at room temperature. The resultant Pd@ED/Cr-MIL-101 catalyst indicates high catalytic activity with turnover frequency (TOF) of 583 h−1 at 328 K, which is superior to most of the reported catalysts, including Pd@PD/Cr-MIL-101 with TOF 532 h−1. Our studies open up a new method to the design of an ultra-small metal nanoparticle for the catalytic dehydrogenation of HCOOH.

Structure and Composition Modification of Ultrasmall Palladium Nanoparticles upon Hydrogenation from First Principles

Palladium-based materials exhibit a high affinity for hydrogen, making them ideal candidates for hydrogen storage or hydrogen sensing applications owing to the existence of a hydride phase. From the theoretical point of view, a bulk or slab is often used to model such systems but lacks the flexibility to adapt its lattice parameter to an increased load of hydrogen. Using density functional theory, we follow the change in the structure and composition of small palladium nanoparticles upon hydrogenation. We show that a cuboctahedral nanoparticle with hydrogen in the core and on the surface is a relevant model under experimental conditions. CO and NO are then adsorbed on this nanoparticle to highlight the crucial importance of hydrogen loading when considering palladium nanomaterials for-wider sensing applications.

Ultra-small palladium nano-particles synthesized using bulky S/Se and N donor ligands as a stabilizer: application as catalysts for Suzuki-Miyaura coupling.

Two chalcogenated ligands L1 and L2 containing anthracene core and amine functionality have been synthesized. Both the ligands have been characterized using 1H and 13C{1H} NMR techniques. The structure of L1 has also been corroborated by single crystal X-ray diffraction. Application of L1 and L2 as stabilizers for palladium nano-particles (NPs) has been explored and six different types of NPs 1–6 have been prepared by varying the quantity of stabilizer. The nano-particles have been characterized by PXRD, EDX, and HRTEM techniques. The size of NPs has been found to be in the range of ∼1–2 nm, 2–3 nm, 4–6 nm, 1–2 nm, 1–2 nm and 3–5 nm for 1–6 respectively. The catalytic activities of 1–6 have been explored for Suzuki–Miyaura coupling of phenyl boronic acid with various aryl halides. These NPs showed good catalytic activity for various aryl chlorides/bromides at low catalyst loading (5 mg). Among 1–6, the highest activity has been observed for NPs 1, probably due to their relatively small size and high uniformity in the dispersion. The recyclability of the NPs upto 5 catalytic cycles is a distinct advantage.

Synthesis and Catalytic Activity of Alkylamine-Capped Ultra-small Palladium Nanoparticles for Organic Pollutant Degradation

Over the past few decades, increasing attention has been focused on overcoming the scarcity of fresh water resources, with the rapid effluents of dyes from modern chemical industries causing issues in photosynthetic activity of aquatic organisms. In the process of recycling wastewater, the degradation of dye pollutants such as 4-nitrophenol, methylene blue, and methyl orange has become more crucial. Noble metal (silver, gold, palladium, and platinum) materials have significant potential applications in the areas of water purification, conversion of automobile exhaust emissions, and catalysis. Ultra-small alkylamine-capped palladium nanoparticles (APd NPs) with sizes below 10 nm are synthesized using hexadecylamine (HDA) as a stabilizing material, and HDA can prevent the irreversible aggregation of small-sized nanoparticles in solution-based reactions. The fabricated ultra-small APd NPs are investigated using UV–Vis, XRD, SEM, TEM, FTIR and TGA studies. In the presence of NaBH4 as a reducing agent, the APd NPs achieve high catalytic performance toward the degradation of dye pollutants such as 4-nitrophenol, methylene blue and methyl orange. Catalytic activity of alkylamine capped palladium nanoparticles for organic pollutant degradation.

A facile route for the preparation of new Pd/La2O3 catalyst with the lowest palladium loading by a new reduction system as a high performance catalyst towards ethanol oxidation

In this work, a novel method is introduced for the production of uniformly ultra-small palladium nanoparticles (PdNPs) using lanthanum oxide nanoparticles (La2O3NPs) as an adsorbing support and a promoter. Here, the Zn/HCl system is also adopted as a reducing agent. The high distribution and small-size PdNPs, decorated on clean surface of La2O3NPs, are successfully fabricated. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transition electron microscopy (TEM) and energy dispersive X-ray analysis (EDS) are used to investigate the structure, morphology and chemical composition of the samples. Electrochemical measurements show the new catalyst with outstanding performance in terms of mass current density and stability in comparison to the commercially available Pd/C catalyst for ethanol oxidation.

Covalent functionalization of graphene with 1,5-diaminonaphthalene and ultrasmall palladium nanoparticles for electrocatalytic oxygen reduction

1,5-diaminonaphthalene and ultrasmall palladium nanoparticles (PdNPs) embedded electrochemically reduced graphene oxide (denoted as ERGO-DAN-Pd) was successfully synthesized and employed as a cathode catalyst for enhanced oxygen reduction reaction (ORR) in direct alkaline fuel cells (DAFCs). The physical properties of ERGO-DAN-Pd were investigated using several instrumental methods. The morphological characterizations demonstrate that the ultrasmall PdNPs were homogeneously dispersed on the ERGO-DAN film. X-ray analysis confirmed the successful covalent functionalization of graphene sheets with DAN. The electrocatalytic activity of ERGO-DAN-Pd towards ORR was excellent compared to other electrodes in 0.1 M KOH electrolyte. Particularly, it showed 1.8 and 2.7 magnitude higher mass activity with large specific activity compared to 20 wt.% Pt/C and nonfunctionalized ERGO/Pd, respectively. Moreover, the reaction kinetic parameters confirmed that the ORR at ERGO-DAN-Pd catalyst was followed by a 4e− process with faster electron transfer rate per O2 with better stability and fuel selectivity than state-of-the-are Pt/C for DAFCs application.

Electrochemical synthesis of nanocomposite of palladium nanoparticles with polymer viologen-containing nanocapsule

An efficient mediated electrosynthesis of the spherical (85 nm) nanocomposite material Pd@p(MVCA8+-co-St) was carried out in an aqueous medium. Ultrasmall palladium nanoparticles (3—8 nm) are stabilized in nanocapsules of water-soluble nanoparticles of the copolymer p(MVCA8+-co-St) consisting of tetraviologen calix[4]resorcinol (MVCA8+) with styrene (St). The role of the mediator is played by viologen units of a polymer nanoparticle at potentials of the MV2+/MV∙+ redox couple. The high catalytic activity of the nanocomposite material in the reduction of nitrophenol with sodium borohydride is shown.

Maghemite decorated with ultra-small palladium nanoparticles (γ-Fe2O3–Pd): applications in the Heck–Mizoroki olefination, Suzuki reaction and allylic oxidation of alkenes

γ-Fe2O3–Pd NPs for Heck, Suzuki and allylic oxidation reaction under milder conditions.

Synergetic catalysis of palladium nanoparticles encaged within amine-functionalized UiO-66 in the hydrodeoxygenation of vanillin in water

Ultrasmall palladium nanoparticles (1.5–2.5 nm) encapsulated within the highly porous and hydrothermally stable amine-functionalized metal–organic framework UiO-66 exhibit excellent catalytic activity for the selective conversion of vanillin to 2-methoxy-4-methylphenol.

Methylviologen Mediated Electrosynthesis of Palladium Nanoparticles Stabilized with CTAC

Efficient electrosynthesis of ultrasmall palladium nanoparticles stabilized with CTA+ cetyltrimethylammonium cations (Pd@CTA+) was carried out in an aqueous medium by methylviologen mediated electroreduction of poorly soluble aggregates ([PdCl4]2−·2CTA+)n of [PdCl4]2− anionic complex with CTA+ cations on a glassy carbon electrode at potentials of the MV2+/MV•+ redox couple. ([PdCl4]2−·2CTA+)n aggregates are reduced directly on the electrode at a low rate and the generated metal is deposited on the electrode. In the case of mediated reduction, the metal is not deposited on the cathode, and after passing of Q = 2 F quantitative conversion from [PdCl4]2− to Pd@CTA+ nanoparticles occurs in the solution bulk. These particles are positively charged (zeta-potential is 66.8 mV) and their hydrodynamic diameter is 18 nm. Separated Pd@CTAC nanoparticles are combined into larger aggregates due to coalescence of the organic shell. The predominant shape of metal nanoparticles is an imperfect sphere with a diameter of 5 ± 3 nm, and the average size of the metal crystallites is 4.66 nm.

Ultra-small Palladium Nanoparticle Decorated Carbon Nanotubes: Conductivity and Reactivity.

Carbon nanotubes decorated with ultra-small metal nanoparticles are of great value in catalysis. We report that individual multiwalled carbon nanotubes decorated with ultra-small palladium nanoparticles can be detected by using the nano-impacts method. The high conductivity and reactivity of each decorated carbon nanotube is directly evidenced; this is achieved through studying the proton-reduction reaction for the underpotential deposition of hydrogen onto the nanoparticles decorated on the carbon nanotube walls. The reductive spikes from current amplification are analyzed to estimate the approximate length of the decorated carbon nanotubes, revealing that the decorated carbon nanotubes are electroactive along its entire length of several micrometers.

A simple method for the preparation of ultra-small palladium nanoparticles and their utilization for the hydrogenation of terminal alkyne groups to alkanes.

A simple and convenient method for the preparation of ultra-small palladium nanoparticles (Pd-NPs) by a modified digestive ripening method is described. These nanoparticles catalyse the hydrogenation of the terminal alkyne groups to alkanes selectively, and show no effect on other labile protecting and internal alkyne or internal/external alkene groups present in the molecule.