Abstract
In this study, we developed a simple-to-use approach based on an atmospheric pressure plasma jet to synthesize aqueous Au nanoparticles (AuNP). Special attention was paid to the different reaction dynamics and AuNP properties under AC and pulse-power-driven plasma jets (A-Jet and P-Jet, respectively). The morphology of the AuNP, optical emissions, and chemical reactions were analyzed. Further, a copper mesh was placed above the reaction cell to evaluate the role of electrons and neutral species reduction. A visible color change was observed after the A-Jet treatment for 30 s, while it took 3 min for the P-Jet. The A-Jet treatment presented a much higher AuNP growth rate and a smaller AuNP diameter compared with the P-Jet treatment. Further analysis revealed an increase in chemical concentrations (Cl− and H2O2) and liquid conductivity after plasma treatment, with a higher increased amplitude for the A-Jet case. Moreover, the electrons alone had little effect on AuNP generation, while neutral species showed a clear Au+ reduction effect, and a unique coupling effect between both reactions was observed. The different reaction dynamics between the A-Jet and P-Jet were attributed to their different local heating effects and different discharge power during the reaction.
Highlights
High-quality gold nanoparticles (AuNPs) play a crucial role in numerous fields, including catalysis, optoelectronics, medical imaging, and sensors [1,2]
We developed a one-step approach based on an atmospheric pressure plasma jet that directly interacts with liquids to generate aqueous Au nanoparticles (AuNP)
To explain the mechanism involved in A-Jet and P-Jet AuNP synthesis, optical emission spectroscopy was used to investigate the active species generated in the plasma jet
Summary
High-quality gold nanoparticles (AuNPs) play a crucial role in numerous fields, including catalysis, optoelectronics, medical imaging, and sensors [1,2]. The electron energy generated by atmospheric pressure plasma can reach up to a few electron volts; it is able to initiate the direct reduction of metal ions in the gas–liquid interface. Other oxidative species, such as OH· and H2O2, can have possible reactions with chloroauric acid [AuClx(OH)4−x]− to form AuNP because AuCl−x has a strong oxidation ability [7]. We developed a one-step approach based on an atmospheric pressure plasma jet that directly interacts with liquids to generate aqueous AuNPs. By applying the plasma jet above the liquid surface, the AuNP can be produced by plasma–liquid interaction. The chemical reactions in the liquid by A-Jet and P-Jet were analyzed to explain the synthesis mechanisms involved in the A-Jet and the P-Jet
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