Low-resistivity Pd nanopatterns created by a direct electron beam irradiation process free of post-treatment steps

The ability to create metallic patterned nanostructures with excellent control of size, shape and spatial orientation is of utmost importance in the construction of next-generation electronic and optical devices as well as in other applications such as (bio)sensors, reactive surfaces for catalysis, etc. Moreover, development of simple, rapid and low-cost fabrication processes of metallic patterned nanostructures is a challenging issue for the incorporation of such devices in real market applications. In this contribution, a direct-write method that results in highly conducting palladium-based nanopatterned structures without the need of applying subsequent curing processes is presented. Spin-coated films of palladium acetate were irradiated with an electron beam to produce palladium nanodeposits (PdNDs) with controlled size, shape and height. The use of different electron doses was investigated and its influence on the PdNDs features determined, namely: (1) thickness of the deposits, (2) atomic percentage of palladium content, (3) oxidation state of palladium in the deposit, (4) morphology of the sample and grain size of the Pd nanocrystals and (5) resistivity. It has been probed that the use of high electron doses, 30000 μC·cm-2 results in the lowest resistivity reported to date for PdNDs, namely 145.1 μΩ·cm, which is only one order of magnitude higher than metallic palladium. This result paves the way for development of simplified lithography processes of nanostructured deposits avoiding subsequent post-treatment steps.

Direct C-H:C-H Arylation Polymerization of 3,4-Propylenedioxythiophene Derivatives

In this manuscript, we report, for the first time, a direct C-H:C-H arylation process for the polymerization of 3,4-propylenedioxythiophene derivatives. The requirement of aryl halides monomers can be completely excluded in this process, making the process atom economical and environmentally friendly. We could successfully homopolymerize Prodot-diethylhexyl using palladium acetate as catalyst. The optimized process required the stepwise ramping of the temperature from 70 °C to 140 °C. It was also observed that a direct heating of the polymerization mixture to 140 °C results in the decomposition of the catalyst leading to unsuccessful polymerization. At present, the exact mechanism of the whole process is not clear.

Simple, Sensitive, and Easy to use Method for Determination of Palladium Content in Palladium Acetate Using Flame Atomic Absorption Spectrophotometry

A simple, sensitive, and easy to use method for the determination of palladium content in palladium acetate was developed using homogeneous acid digestion of palladium acetate followed by atomic absorption spectrometry (AAS) analysis. Parameters affecting the extraction efficiency of palladium during digestion of palladium acetate were investigated and optimized. The palladium content was measured at 244.7 nm by atomic absorption (AA) spectrometers on PinAAcle™ 900 series with an air-acetylene flame. The linear calibration graph was observed in the range of 2.5-15 ppm with a limit of detection of 8.33 ppm and a correlation coefficient of 0.999970. For 5 replicate analyses of each palladium reference solution the relative standard deviation was within 2.00%.Analytical method validation for the method was carried out and obtained results were satisfactory.To verify, the accuracy parameter of the method validation, for the determination of Pd(II) from sample palladium acetate standard addition method was applied and satisfactory results were obtained. Optimization of analytical method variables during analytical method development is discussed.

Synthesis, Characterization, and Catalytic Application of Palladium Complexes Containing Indolyl-NNN-Type Ligands

In this study, a series of N-heterocyclic indolyl ligand precursors 2-Py-Py-IndH, 2-Py-Pz-IndH, 2-Py-7-Py-IndH, 2-Py-7-Pz-IndH, and 2-Ox-7-Py-IndH (L1H-L5H) were prepared. The treatment of ligand precursors with 1 equivalent of palladium acetate affords palladium complexes 1–5. All ligand precursors and palladium complexes were characterized by NMR spectroscopy and elemental analysis. The molecular structures of complexes 3 and 5 were determined by single crystal X-ray diffraction techniques. The application of those palladium complexes 1–5 to the Suzuki reaction with aryl halide substrates was examined.

Hollow-Shell-Structured Mesoporous Silica-Supported Palladium Catalyst for an Efficient Suzuki-Miyaura Cross-Coupling Reaction

The construction of a high stability heterogeneous catalyst for privileged common catalysis is a benefit in regard to reuse and separation. Herein, a palladium diphenylphosphine-based hollow-shell-structured mesoporous catalyst (HS@PdPPh2@MSN) was prepared by immobilizing bis((diphenylphosphino)ethyltriethoxysilane)palladium acetate onto the inner wall of a mesoporous organicsilicane hollow shell, whose surface was protected by a –Si(Me)3 group. Electron microscopies confirmed its hollow-shell-structure, and structural analyses and characterizations revealed its well-defined single-site active species within the silicate network. As presented in this study, the newly constructed HS@PdPPh2@MSN enabled an efficient Suzuki-Miyaura cross-coupling reaction for varieties of substrates with up to 95% yield in mild conditions. Meanwhile, it could be reused at least five times with good activity, indicating its excellent stability and recyclability. Furthermore, the cost-effective and easily synthesized HS@PdPPh2@MSN made it a good candidate for employment in fine chemical engineering.

Modification of Surface Bond Au Nanospheres by Chemically and Plasmonically Induced Pd Deposition

In this work we investigated methods of modifying gold nanospheres bound to a silicon surface by depositing palladium onto the surfaces of single nanoparticles. Bimetallic Au-Pd nanoparticles can thus be gained for use in catalysis or sensor technology. For Pd deposition, two methods were chosen. The first method was the reduction of palladium acetate by ascorbic acid, in which the amounts of palladium acetate and ascorbic acid were varied. In the second method we utilized light-induced metal deposition by making use of the plasmonic effect. Through this method, the surface bond nanoparticles were irradiated with light of wavelengths capable of inducing plasmon resonance. The generation of hot electrons on the particle surface then reduced the palladium acetate in the vicinity of the gold nanoparticle, resulting in palladium-covered gold nanospheres. In our studies we demonstrated the effect of both enhancement methods by monitoring the particle heights over enhancement time by atomic force microscopy (AFM), and investigated the influence of ascorbic acid/Pd acetate concentration as well as the impact of the irradiated wavelengths on the enhancement effect. It could thus be proven that both methods were valid for obtaining a deposition of Pd on the surface of the gold nanoparticles. Deposition of Pd on the gold particles using the light-assisted method could be observed, indicating the impact of the plasmonic effect and hot electron for Pd acetate reduction on the gold particle surface. In the case of the reduction method with ascorbic acid, in addition to Pd deposition on the gold nanoparticle surface, larger pure Pd particles and extended clusters were also generated. The reduction with ascorbic acid however led to a considerably thicker Pd layer of up to 54 nm in comparison to up to 11 nm for the light-induced metal deposition with light resonant to the particle absorption wavelength. Likewise, it could be demonstrated that light of non-resonant wavelengths was not capable of initiating Pd deposition, since a growth of only 1.6 nm (maximum) was observed for the Pd layer.

Catalyst-Controlled Site-Selective N-H and C3-Arylation of Carba-zole via Carbene Transfer Reactions

A site-selective direct arylation reaction of carbazole and other N-heterocycles with diazo-naphthalen-2(1H)-ones has been developed. While Au(I)-NHC catalysts lead to selective C3-arylation, palladium acetate allows for selective N-H arylation, displaying...

Palladium-catalyzed synthesis of α-aryl acetophenones from styryl ethers and aryl diazonium salts via regioselective Heck arylation at room temperature

Synthesis of α-aryl acetophenones from styryl ethers and aryldiazonium salts is described at room temperature. The reaction is catalyzed by palladium acetate in the absence of ligands and base.

Magnetic palladium nickel carbon nano-composite as a heterogeneous catalyst for the synthesis of distyrylbenzene and biphenyl derivatives

The magnetic palladium nickel carbon (Fe3O4@Pd@Ni/C) nano-composite has been synthesized in a simple one-pot procedure via a hydrothermal approach. Ferric nitrate, palladium acetate, and nickel nitrate were dissolved in water...