Application of Direct Current Atmospheric Pressure Glow Microdischarge Generated in Contact with a Flowing Liquid Solution for Synthesis of Au-Ag Core-Shell Nanoparticles.

Anna Dzimitrowicz,Marcin Nyk,Pawel Pohl,Piotr Jamroz

doi:10.3390/ma9040268

Abstract

A direct current atmospheric pressure glow microdischarge (dc-μAPGD) generated between an Ar nozzle microjet and a flowing liquid was applied to produce Au-Ag core-shell nanoparticles (Au@AgCSNPs) in a continuous flow system. Firstly, operating dc-μAPGD with the flowing solution of the Au(III) ions as the cathode, the Au nanoparticles (AuNPs) core was produced. Next, to produce the core-shell nanostructures, the collected AuNPs solution was immediately mixed with an AgNO3 solution and passed through the system with the reversed polarity to fabricate the Ag nanoshell on the AuNPs core. The formation of Au@AgCSNPs was confirmed using ultraviolet-visible (UV-Vis) absorbance spectrophotometry, transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopy (EDS). Three localized surface plasmon resonance absorption bands with wavelengths centered at 372, 546, and 675 nm were observed in the UV-Vis spectrum of Au@AgCSNPs, confirming the reduction of both the Au(III) and Ag(I) ions. The right configuration of metals in Au@AgCSNPs was evidenced by TEM. The Au core diameter was 10.2 ± 2.0 nm, while the thickness of the Ag nanoshell was 5.8 ± 1.8 nm. The elemental composition of the bimetallic nanoparticles was also confirmed by EDS. It is possible to obtain 90 mL of a solution containing Au@AgCSNPs per hour using the applied microdischarge system.

Highlights

Over the last few years, a significant increase in the scientific interest of metallic structures of nanometric size has been observed
The color of the Au nanoparticles (AuNPs) precursor (HAuCl4 ) solutions was yellowish, and was changed to ruby red following the first treatment with dc-μAPGD, which is characteristic of the AuNPs formation
The dc‐μAPGD system was adapted for the synthesis of the Au@AgCSNPs

Summary

Introduction

Over the last few years, a significant increase in the scientific interest of metallic structures of nanometric size has been observed. The special properties of such nanoparticles (NPs), the high surface area to volume ratio, have resulted in the rapid development of their synthesis and characterization methods [1,2,3,4]. It was established that the exceptional properties of CSNPs could be tailored by altering the ratio between their core and shell, or by changing the kind of the applied material [12,17]. The Au@AgCSNPs, being inorganic/inorganic CSNPs and consisting of an Au core and an Ag shell, have been acknowledged to display many unique optical [11,18], catalytic [19], oxidative [20], and biosensoring properties [21], due to the properties of both noble metals nanostructures

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