Synthesis of composition-tunable Pd–Cu alloy nanoparticles by double target sputtering

Abstract

In this work, we introduce a green synthesis technique, double-target sputtering into a liquid polymer – polyethylene glycol (PEG, M. W. = 600), to synthesize palladium–copper (Pd–Cu) alloy nanoparticles (NPs) dispersed in PEG.

Sputtering onto liquids: a critical review

“…Yonezawa's group has shown that stirring of the host liquid during sputtering of Au onto PEG helps to decrease the size of final Au NPs by almost a factor of two, from 7.4 ± 2.1 nm to 3.7 ± 0.9 nm [207]. Stirring was applied in [121,127,137,140,199,202,203,[205][206][207][208]210,223,224]. It was noticed that an increase in the rotation speed leads to a decrease in the NP size and size distribution [127].…”

“…It should be noted that, in the case of noble metals, secondary growth processes were mentioned for dispersions of Au [ 115 , 118 , 138 , 140 , 143 – 144 167 , 183 , 189 , 195 ], Ag [ 131 , 164 , 185 , 196 ], and Pt [ 185 ] NPs. When metals such as Ti [ 179 , 197 ], Cu [ 117 , 155 , 174 – 175 189 , 198 – 199 ], Fe/Al [ 200 ], Mo [ 201 ], or In [ 187 ] were sputtered , the products were oxidized due to reaction with the host liquid and/or air after removing the samples from the vacuum chamber.…”

“…The team of Yonezawa performed, first, the synthesis of Pd/Cu alloy NPs with a wide range of composition by varying the intensity on the targets during co-SoL [ 199 ]. However, they reported an unexpectedly high content of Pd within the alloy NPs together with a large dispersion of NPs composition under the same conditions measured by STEM-EDS as compared to XPS and XRD analysis.…”

“…However, they reported an unexpectedly high content of Pd within the alloy NPs together with a large dispersion of NPs composition under the same conditions measured by STEM-EDS as compared to XPS and XRD analysis. They suspect that Cu atoms in the alloy NPs oxidized and further dissolved, leaving the Pd/Cu alloys NPs with an excess of Pd [ 199 ]. The same year, they synthesized Pt/Au NPs with a wide range of composition from 20 to 100 atom % of Pt by co-SoL.…”

Pt/Ag Solid Solution Alloy Nanoparticles in Miscibility Gaps Synthesized by Cosputtering onto Liquid Polymers

“…Sputtering is a conventional physical technique for the fabrication of thin films or creation of NPs directly on solid substrates from the bulk target in a vacuum and dry conditions. , Nonvolatile or low volatile liquids as the substrates, − e.g., silicone oils, ionic liquids, ,,, and liquid polymers, ,− have been used for obtaining NPs dispersed in liquids for a long time continuous sputtering. Compared with the traditional chemical reduction method, cosputtering can simultaneously produce metal atoms and clusters of two or more metals for making alloy NPs at room temperature regardless of the difference in redox potentials of metals and without using toxic reductants. − Moreover, it is capable of varying the properties of NPs by varying the size, composition, composition distribution, and structures of NPs via adjusting the sputtering parameters such as the currents applied to the metal targets. − Cosputtering onto liquid allows obtention of solid solution alloys of metal pairs that have miscibility gaps and/or form intermetallic compounds in the phase diagram such as Au/Pd, Pt/Au, Au/Cu, and Cu/Pd. − However, so far, there has been no report on cosputtering onto liquid at room temperature of Pt/Ag NPs below 3 nm, their fine structure, and whether solid solution alloys can be attained, especially for the composition in the miscibility gap. Furthermore, the correlation of particle size and composition varied with the metal pairs; that is, the size–composition relation is not obvious in cosputtered Au/Cu and Cu/Pd whereas highly correlated in Pt/Au NPs. − This relation has not been addressed for cosputtered Pt/Ag NPs.…”