| AVS 66th International Symposium & Exhibition | |
| Plasma Science and Technology Division | Monday Sessions |
| Session PS1-MoA |
| Session: | Plasma-Liquid Interactions, Medicine, and Agriculture |
| Presenter: | Tommaso Gallingani, Alma Mater Studiorum-University of Bologna, Italy, Italia |
| Authors: | T. Gallingani, Alma Mater Studiorum-University of Bologna, Italy, Italia N.H. Abuyazid, Case Western Reserve University M. Gherardi, Alma Mater Studiorum-University of Bologna, Italy V. Colombo, Alma Mater Studiorum-University of Bologna, Italy C.J. Hogan, University of Minnesota, Minneapolis R.M. Sankaran, Case Western Reserve University |
| Correspondent: | Click to Email |
Because of their unique features and low-temperature chemistry, non-thermal, atmospheric-pressure (AP) plasmas have attracted interest for material synthesis in multiphase environments where the plasma is in contact with a liquid surface. In the most common configuration, the reaction interface is highly localized, leading to inhomogeneities and mass transport limitations. In light of these issues, liquid water jet and a liquid aerosol have been proposed as alternative strategies that allow continuous liquid flow and promote more controlled reaction. However, applications of these multiphase systems are complicated and limited by lack of knowledge of reaction mechanisms.
Here, we carried out a detailed study of a flow-through, liquid-droplet plasma system using an online ion mobility spectrometry (IMS) system to characterize precursor to particle conversion. IMS measures the electrical mobility of aerosol particles providing real time size distribution. The focus of our study was silver nitrate (AgNO3) which has been well-studied in plasma-liquid synthesis and, thus, provides a straightforward chemistry to benchmark our results . Liquid droplets containing AgNO3 were produced by a Venturi effect nebulizer and carried in by an argon flow into an AP dielectric barrier discharge (DBD). The DBD configuration was a quartz tube with two ring electrodes in parallel to avoid any metal in contact with the plasma and driven by an alternating current high voltage generator. The effluent of the reactor was diluted by a flow of nitrogen gas and coupled to the inlet of a commercial IMS system. For a given flow rate, precursor concentration, and plasma power, our results show that the mean particle diameter decreases from 38 to 26 nm when the plasma is on which could be ascribed to AgNO3 reduction to silver (Ag). The synthesized Ag nanoparticles (NPs) were collected either by electrostatic precipitation or filtration for materials analysis. NPs size distribution and morphology were assessed by transmission electron microscopy and found to have good agreement with IMS data. Ultraviolet-visible absorbance showed the well-known localized surface plasmon resonance peak for Ag at approximately 400 nm, confirming a successful conversion. We also performed a control experiment with a diffusion dryer to remove the water and only introducing dried AgNO3. The lack of any reduction to Ag NPs suggested that the mechanism involves water and plasma species alone cannot reduce AgNO3. This study provides important insight into liquid-droplet-based multiphase plasma reactors which are a novel approach to synthesizing NPs from precursors that are not available as a vapor.