Preparation of PtAu Alloy Colloids by Laser Ablation in Solution and Their Characterization

Abstract

Stable PtAu alloy colloids with a wide range of compositions were prepared using pulsed laser ablation on single metal-mixture targets in water. The concentration of Pt in the alloys can be tuned by varying the Pt/Au ratio in the targets, which are made by compression molding a mixture of Pt and Au powders at different ratios. Such fabricated PtAu alloy nanoparticles (NPs) show a face-centered cubic structure, and their composition basically follows that of their corresponding targets. The effect of aqueous solution pH and ablating laser fluence on the formation and structure of alloy NPs was further investigated. It is found that PtAu alloy colloids of identical composition can be achieved over a pH range extending from 4.0 to 11.0 and at fluences varying from 4 to 150 J cm–2 as long as the targets of the same composition are used. This finding suggests that alloy formation is essentially insensitive to both factors in certain ranges, and the method developed herein for the alloy NP formation is quite robust. Moreover, the surface composition, estimated from electrochemical measurements, is identical to the overall composition of the NPs estimated from Vegard’s law and X-ray diffraction data, which is a strong indication of the uniform composition on the surface and in the interior of these alloy NPs.

Alloying colloidal silver nanoparticles with gold disproportionally controls antibacterial and toxic effects

“…However, both studies used alloy colloids with a core to shell increase in the silver ratio and explained the reduced cytotoxic effects with this heterogenic ultrastructure of the particles. In our case, homogeneous ultrastructure has been observed for Ag-Au alloy fabricated by laser ablation in liquid [65] and has also been reported into detail for other metal alloy nanoparticles fabricated by laser ablation [34]. In consequence, heterogeneity cannot be taken as explanation.…”

“…Hence, toxicological analysis of laser-generated colloids reveals toxicity only for nanoparticles and not for residual chemicals [28,29], like it is the case with chemically prepared colloids [30,31]. This method enables ablation of different alloy materials, especially if the targets consist of fully miscible elements such as Ag and Au, or Pt and Ir [32][33][34]. The availability of any desired Ag/Au ratio in a solid alloy, in combination with its ablation in liquid by lasers, gives access to colloidal alloy nanoparticles with defined compositions [35,36].…”

Interaction of colloidal nanoparticles with their local environment: the (ionic) nanoenvironment around nanoparticles is different from bulk and determines the physico-chemical properties of the nanoparticles

“…An indirect verification of a pI value in ligand-free noble metal systems was recently found for Au 50 Pt 50 -alloy NPs which were laser-ablated at different pHs. Here, a steep increase in NP size owing to agglomeration processes was found at pH , 7 [118]. A titration of ligand-free gold NPs in order to determine the pI value was performed for NPs obtained from gas-phase synthesis [95] and laser ablation in liquid [103,119] by monitoring the zeta-potential at different pH values.…”

Substrate-induced assembly of PtAu alloy nanostructures at choline functionalized monolayer interface for nitrite sensing

“…They usually demonstrate higher catalytic activity, faster response rate, and better resistance to deactivation for various chemical processes [3,4], which are ascribed to electronic (ligand) effects and/or geometric effects caused by the surface atomic environment of distinct metal atoms [5][6][7]. In recent years, a variety of intriguing strategies have been designed to prepare alloy nanoparticles, such as laser ablation [8], cathodic corrosion [9], chemical reduction [10,11], salt impregnation [12], colloidal synthesis [13], and dendrimer templating method [14]. These methods are helpful for the study of alloy nanomaterials, while relatively time-consuming operations, complicated experimental conditions, or surface contamination arising from surfactant are commonly involved, which hinder their further applications [3,5].…”