Kunihito Tanaka

The aqueous extract of the leaves of Odontonema strictum (OSM) is used in folk medicine for its antihypertensive properties, and it contains a wide range of secondary metabolites, mostly polyphenols such as verbascoside and isoverbascoside, which could play a major role in the preparation of silver nanoparticles. In this study, we aimed to prepare AgNPs for the first time using the OSM leaf extract (OSM-AgNPs) to investigate their free radical-scavenging potency against 1,1-diphenyl-2-picrylhydrazyl (DPPH) and hydrogen peroxide (H2O2). Dynamic light scattering (DLS), UV/Vis, Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), and X-ray photoelectron spectroscopy (XPS) were used to characterize the OSM-AgNPs. With a size around 100 nm and a ζ-potential of −41.1 mV, OSM-AgNPs showed a good stability and a better colloidal property due to electrostatic repulsion and the dispersity. The strong absorption peak at 3 keV in the EDX spectra indicated that silver was the major constituent. Additionally, the existence of silver atoms was confirmed by the Ag 3d5/2 peak around 367 eV in the XPS spectra. IC50 values of 116 μg/mL and 4.4 μg/mL were obtained for the scavenging activities of DPPH and H2O2, respectively. The synthetic OSM-AgNPs can be further exploited as potential antioxidant agents.

<title>Abstract</title>The atmospheric pressure low-temperature homogeneous discharge using helium and nitrogen, both known for industrial applications, was reviewed. In case of helium, metastable atoms (2¹s and 2³s) produced in the glow discharge were able to dissociate mixed molecular gases to produce radicals or atoms. Radical species undergo chemical reactions, such as oxidation or nitration reaction and form products on the electrode surfaces. Applications of helium atmospheric pressure glow discharge including surface treatment of plastic films to enhance adhesibility with glue, weakening strength with pressure-sensitive glue, and deposition of solid material on a flat plate or powder surfaces, were described. Moreover, the microwave low-temperature discharge using nitrogen, as a cost-saving carrier gas, were introduced for the surface cleaning of silicon wafer.