Plasma‐Assisted Dissociation of Organometallic Vapors for Continuous, Gas‐Phase Preparation of Multimetallic Nanoparticles

Abstract

Metal nanoparticles (NPs) are characterized by novel electronic, optical, magnetic, and catalytic properties radically different from their bulk counterparts. A special class of metal NPs because of their unique multifunctional [1][2][3] and synergistic [4,5] properties is multimetallic NPs which are composed of two or more distinct metal elements with alloyed, coreshell, or other architectures. Despite the development of numerous synthetic routes for metal NP synthesis, the preparation of multimetallic NPs with controlled size, composition, morphology, and purity remains a significant challenge. Broadly speaking, multimetallic NPs have been synthesized by two strategies, that is, either in the liquid or gas phase. Liquid-phase methods involve the reduction of a metal salt dissolved in solution by a chemical reducing agent, such as NaBH 4 . [6] However, when two or more metal salts are co-reduced to produce multimetallic NPs, differences in the reduction potential for the individual metal ions result in random particle compositions or morphologies. [7,8] In addition, surfactants, which are needed to control particle nucleation and growth, can adversely affect particle properties. [9] Alternatively, metal NPs have been produced in the gas phase, without chemical reducing agents or surfactants, by flame pyrolysis [10] and laser ablation. [11,12] Unfortunately, these gas-phase approaches are complex and have suffered from excessive particle growth and aggregation, making them far less useful than liquidphase approaches for metal NP synthesis. [13] Moreover, few reports exist of multimetallic NP synthesis in the gas phase. [14][15][16] Herein, we present a plasma-based scheme for the preparation of multimetallic NPs. Nanoparticles are synthesized from vapors of organometallic compounds such as bis(cyclopentadienyl)nickel [Ni(Cp) 2 ] [17] or copper acetylacetonate [Cu(acac) 2 ] [18] that have a long history in metal-organic chemical vapor dep-

On the non‐thermal plasma synthesis of nickel nanoparticles

“…Nickel and other metallic particles have been produced in atmospheric pressure microplasmas starting from metalorganic precursors. While there is no reported data regarding the throughput and the precursor utilization rate in such systems, the authors of these reports suggest that the particles are generated via a homogeneous nucleation process and the particles are effectively carbon‐free . While understanding the details of particle nucleation is far from trivial, our results do not rule out that particle formation may occur via homogeneous nucleation in our low‐pressure process as well.…”

“…While there is no reported data regarding the throughput and the precursor utilization rate in such systems, the authors of these reports suggest that the particles are generated via a homogeneous nucleation process and the particles are effectively carbon-free. [12a, 13,22] While understanding the details of particle nucleation is far from trivial, our results do not rule out that particle formation may occur via homogeneous nucleation in our low-pressure process as well. The relatively low dissociation energy of nickelocene, combined with the RGA precursor consumption data, are consistent with this interpretation.…”

Fuel Cell Electrodes From Organometallic Platinum Precursors: An Easy Atmospheric Plasma Approach

“…In this process, the precursors are often dissociated in the plasma volume to nucleate particles in the gas phase. In this case, the process requires the sublimation of the metallic powder and an extremely short residence time (∼1 ms) of the vapor in the atmospheric micro‐discharge for a very high plasma power …”

“…In this case, the process requires the sublimation of the metallic powder and an extremely short residence time ($1 ms) of the vapor in the atmospheric microdischarge for a very high plasma power. [22,23] The anchoring of metallic nanoparticles on a support requires the presence of anchoring sites. Many studies concerning the plasma activation of carbon supports were conducted to improve the interfacial interactions between the support and the deposited metal nanoparticles.…”

A facile synthesis of high quality nanostructured CeO2 and Gd2O3-doped CeO2 solid electrolytes for improved electrochemical performance

“…Atmospheric-pressure plasma techniques have been used in several applications such as surface treatment, 18 thin film deposition, 19 and nanoparticle fabrication. 20 Here, we report the use of an atmospheric pressure plasma jet (APPJ) in conjunction with nitrate salt precursor solutions in a fast oxidation process for the one-step fabrication of CeO 2 and 10GDC NPs. So far, the synthesis of CeO 2 and GDC NPs using an atmospheric plasma process has not been investigated.…”