Ionic Liquid Assisted Synthesis of Au–Pd Bimetallic Particles with Enhanced Electrocatalytic Activity

Morphology‐ and composition‐controlled synthesis of Au–Pd bimetallic particles was realized by a facile ionic liquid assisted route at room temperature. The morphologies of the synthesized particles, such as nanoflake‐constructed spheres with a core–shell structure, nanoparticle‐constructed spheres, and nanoparticle‐constructed dendrites, could be well controlled by the present route. The ionic liquid was found to play a key role in the formation of these interesting particles. Moreover, the composition (Au:Pd) of the particles could be modulated by means of the molar ratio of the metal precursors in the feeding solutions. The Au–Pd bimetallic particles exhibit high electrocatalytic activity toward oxidation of ethanol and formic acid. Furthermore, cyclic voltammetric studies on the as‐prepared Au–Pd bimetallic particles revealed good electroactivity for H₂O₂, which results in an effective amperometric H₂O₂ sensor.     

A Green Synthesis of Nanosheet‐Constructed Pd Particles in an Ionic Liquid and Their Superior Electrocatalytic Performance

The ionic liquid 1‐ethyl‐3‐methylimidazolium acetate ([EMIM]Ac) is investigated as a solvent for the synthesis of Pd particles. Interestingly, nanosheet‐constructed Pd particles could be successfully synthesized in [EMIM]Ac without any additional reducing agent and template under ionothermal conditions. [EMIM]Ac itself works as the solvent, the reducing agent, and the template for the formation of these interesting Pd particles, making this method complementary to the well‐known ionic‐liquid‐precursor approach. Furthermore, [EMIM]Ac can be recycled with no loss of activity for the formation of nanosheet‐constructed Pd particles within our studied cycles. Specifically, the nanosheet‐constructed Pd particles exhibit superior electrocatalytic activity and stability towards ethanol oxidation and formic acid oxidation compared with commercially available Pd black catalyst, thus demonstrating their promising applications in fuel‐cell area. The current approach, thus, presents a green approach towards the synthesis of Pd particles, using only a simple palladium salt and an ionic liquid.     

Immobilization of Pd(II) Catalysts for Cyclopropanation in Ionic Liquid

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Immobilization of Pd（Ⅱ）Catalysts for Cyclopropanation in Ionic Liquid

Cyclopropanation of styrene with ethyl diazoacetate catalyzed by Pd(Ⅱ） in ionic liquid [omim][BF4] was investigated.Palladium catalysts can be effectively immobilized in ionic liquid.The catalysts PdCl2 and cyclopalladated complex 2 contained in ionic liquid could be recycled for 6 and 7 times,respectively,without losing the efficiency.     

Room‐Temperature Suzuki‐Miyaura Reaction Catalyzed by Palladium Nanoparticles in Lactate‐Anion Ionic Liquid

A palladium nanoparticle catalyst (PdNPs@[Bmim]Lac) has been prepared by a simple, mild and efficient chemical approach using 1‐butyl‐3‐methylimidazolium lactate ([Bmim]Lac) ionic liquid) as a stabilizer. This catalyst exhibits excellent activity, stability, recyclability and simple manipulation in Suzuki‐Miyaura reactions at room temperature in air.     

羧基功能化离子液体修饰Pd纳米微粒的制备及结构表征

1-methyl-3-(ω-carboxyl)decyl imidazolium bromine ([C₁₁OOHmim]Br) ionic liquid was synthesized and [C₁₁OOHmim]Br modified Pd nanoparticles were prepared in solution. The morphology and structure of Pd nanoparticles were investigated by IR, TEM, XRD, XPS. The results indicated that the Pd nanoparticles were face-centered cubic structure and the diameter was between 10～30 nm. [C₁₁OOHmim]Br was connected to the surface of Pd nanoparticles by carboxyl and Pd nanoparticles with different sizes could be obtained by varying the amount of the modifier.     

Catalytic Transfer Hydrogenation and Hydrogenolysis in Ionic Liquids with Pd/MgLa Mixed Oxide and Pd/MgAl Hydrotalcite as Recyclable Catalysts

A new Pd/MgLa mixed oxide and the known Pd/MgAl hydrotalcite catalysts were applied and recycled successfully in catalytic transfer hydrogenation reactions in ionic liquids. Some α,β‐unsaturated carboxylic acid derivatives were hydrogenated in excellent yields. The catalysts were recycled without significant loss of activity. Besides that, a number of halogenated aromatic compounds were dehalogenated under similar catalytic transfer conditions.     

Click Ionic Liquids: A Family of Promising Tunable Solvents and Application in Suzuki–Miyaura Cross‐Coupling

A series of click ionic salts 4 a – 4 n was prepared through click reaction of organic azides with alkyne‐functionalized imidazolium or 2‐methylimidazolium salts, followed by metathesis with lithium bis(trifluoromethanesulfonyl)amide or potassium hexafluorophosphate. All salts were characterized by IR, NMR, TGA, and DSC, and most of them can be classified as ionic liquids. Their steric and electronic properties can be easily tuned and modified through variation of the aromatic or aliphatic substituents at the imidazolium and/or triazolyl rings. The effect of anions and substituents at the two rings on the physicochemical properties was investigated. The charge and orbital distributions based on the optimized structures of cations in the salts were calculated. Reaction of 4 a with PdCl₂ produced mononuclear click complex 4 a‐Pd , the structure of which was confirmed by single‐crystal X‐ray diffraction analysis. Suzuki–Miyaura cross‐coupling shows good catalytic stability and high recyclability in the presence of PdCl₂ in 4 a . TEM and XPS analyses show formation of palladium nanoparticles after the reaction. The palladium NPs in 4 a are immobilized by the synergetic effect of coordination and electrostatic interactions with 1,2,3‐triazolyl and imidazolium, respectively.     

Nanoparticle Capping Agent Controlled Electron‐Transfer Dynamics in Ionic Liquids

Herein, we report a change in the mechanism of the oxidation of silver nanoparticles (Ag NPs) with the molecular weight of a poly(ethylene) glycol (PEG) capping agent. Characterisation of the modified nanoparticles is undertaken using dynamic light scattering and UV/Vis spectroscopy. Electrochemical analyses reveal that the oxidation of 6000 molecular weight (MW) PEG is consistent with a polymer‐gated mechanism, whilst for 2000 MW PEG the polymer does not hinder the oxidation. The 10,000 MW PEG Ag NPs are rendered almost electrochemically inactive. This study demonstrates the ability to alter and better understand the electron‐transfer mechanism in a room temperature ionic liquid (RTIL) by systematically altering the capping agent.     

In Situ Formation of Au–Pd Bimetallic Active Sites Promoting the Physically Mixed Monometallic Catalysts in the Liquid‐Phase Oxidation of Alcohols

The catalytic oxidation of alcohols with molecular oxygen on supported nanometallic catalysts represents one of the green methods in a crucial process for the synthesis of fine chemicals. We have designed an experiment using physically mixed Au/AC and Pd/AC (AC=activated carbon) as the catalyst in the liquid‐phase oxidation of benzyl alcohol by aerobic oxygen. The evolution of the physically mixed catalyst structures at different stages in the catalytic reaction was investigated by aberration‐corrected high‐resolution transmission electron microscopy and spatially resolved element mapping techniques at the nanometre scale, and they were also compared with the structure of the bimetallic alloy. For the first time we show the formation of surface Au–Pd bimetallic sites by reprecipitation of Pd onto Au nanoparticles. Negligible Au leaching was observed. The in situ structural evolution can be directly correlated to the great enhancement of the catalyst activity. Moreover, we distinguish the different behaviours of Au and Pd, thus suggesting an oxygen differentiating mechanism for Au and Pd sites. The findings are of great importance to both the understanding of the structure–activity correlation and the design of highly active catalysts in green chemistry.     

Gold Nanoparticles Grown on Ionic Liquid‐Functionalized Single‐Walled Carbon Nanotubes: New Materials for Photothermal Therapy

Gold nanoparticles were grown on single‐walled carbon nanotubes (SWNTs) coated with a thiol‐functionalized ionic liquid resulting in the formation of core‐shell structures referred to as SWNT‐IL‐Au nanohybrid materials. The nanohybrid materials were characterized by high‐resolution transmission electron microscopy (HR‐TEM), Raman‐, and UV/Vis absorption spectroscopy. The nanohybrid materials were found to enter lysosomes in HeLa cells and show negligible cytotoxicity. Interestingly, they have an enhanced NIR absorption that is effectively transferred into heat to cause localized hyperthermia, resulting in rapid cell death; overall, the material appears to have excellent properties for photothermal therapeutic applications.     

Palladium nanoparticles‐decorated triethanolammonium chloride ionic liquid‐modified TiO2 nanoparticles (TiO2/IL‐Pd): A highly active and recoverable catalyst for Suzuki–Miyaura cross‐coupling reaction in aqueous medium

In this work, an easily obtained procedure was successfully implemented to prepare novel palladium nanoparticles decorated on triethanolammonium chloride ionic liquid‐functionalized TiO₂ nanoparticles [TiO₂/IL‐Pd]. Different methods were carried out for characterizations of the synthesized nanocatalyst (HR‐TEM, XPS, XRD, FE‐SEM, EDX, FT‐IR and ICP). TiO₂/IL‐Pd indicated good catalytic activity for the Suzuki–Miyaura cross‐coupling reaction of arylboronic acid with different aryl halides in aqueous media at ambient temperature. The recycled catalyst was investigated with ICP to amount of Pd leaching after 6 times that had diminished slightly, Thus, was confirmed that the nanocatalyst has a good sustainability for C–C Suzuki–Miyaura coupling reaction. The catalyst can be conveniently separated by filtration of the reaction mixture and reused for 6 times without significant loss of its activity. It supplies an environmentally benign alternative path to the existing protocols for the Suzuki–Miyaura reaction.