| AVS 58th Annual International Symposium and Exhibition | |
| Plasma Science and Technology Division | Monday Sessions |
| Session PS+BI-MoA |
| Session: | Multiphase (Liquid, Solid, Gas) and Biological Related Plasmas |
| Presenter: | Maria Antoaneta Bratescu, Nagoya University, Japan |
| Authors: | M.A. Bratescu, Nagoya University, Japan O. Takai, Nagoya University, Japan N. Saito, Nagoya University, Japan |
| Correspondent: | Click to Email |
The Solution Plasma Processing (SPP) has been developed in our laboratory to synthesize nanoparticles and to improve surface properties of carbon nanomaterials by decorating with different nanoparticles or binding functional groups on the surface. The purpose of the present study is to investigate the mechanism of the Au nanoparticles (NP) formation in the SPP and to correlate the SPP properties with the Au NPs characteristics (morphology, size and surface functionalization). The investigation was conducted by changing the solution pH, using the same surfactant and keeping the same processing parameters.
The Au NPs were synthesis in an aqueous solution of 1 mM HAuCl4·3H2O used as precursor, 1 mM hexadecyltrimethylammonium chloride (CTAC) used as surfactant, and NaOH used to adjust the solution pH (3.2, 6.5 and 11.2). The plasma was produced by using a pulsed high voltage (HV) power supply with the peak voltage and current of 2 kV and 1 A, respectively and the pulse width of about 1 μs. Plasma was characterized by optical emission spectroscopy (OES). The OES gives information about the presence of the relative number densities of the radicals as H, OH, O, and O2 and from these data the electron temperature and density were evaluated.
On surface, in high vacuum environment, the Au NPs were characterized by Transmission Electron Microscopy (TEM), Secondary Ion Mass Spectrometry Time of Flight (SIMS - ToF) and X-rays Photoelectron Spectroscopy (XPS). In solution, as prepared, the Au NPs were characterized by UV-visible spectroscopy and Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) spectroscopy.
The size of the synthesized Au NPs depends on the initial pH of the solution. In a low pH solution, the particle size was around 15 – 20 nm diameter and in a solution with a higher pH value than 6, the NPs diameter was found to be 2 – 5 nm. The negative SIMS-ToF measurements reveals the presence of the Au-, AuCl- and AuN- ions in the solution with a pH 3 and AuO- in a solution with pH 11. In a solution before plasma processing, with a low pH value the negative ions Au2Cl- and Au3Cl2- were detected, which can suggest an initial agglomeration of Au atoms in solution. The binding functional groups on the Au NPs are confirmed by the XPS analysis.
The correlation among information of the Au NPs morphology, the binding atoms on Au surface, plasma electron temperature and density and the formation of the Au complexes, during the Au NPs synthesis will be presented and discussed.