Effect of Atmospheric-Pressure Plasma Jet of Neon on 7-Acetoxy-6-(2,3-Dibromopropyl)-4,8-Dimethylcoumarin Molecule


JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, vol.86, no.6, 2017 (SCI-Expanded) identifier identifier


Atmospheric-pressure low-temperature plasma jets and their applications are a topic of great interest in the fields of physics, technology, and medicine. In this study, the used self-made plasma jet is based on a dielectric barrier discharge (DBD) in neon (Ne) with typical processing parameters, such as frequency in the kHz range and voltage in the kV range. The plasma is characterized by optical emission spectroscopy (OES). These types of plasma can be used in various applications such as surface modification, inactivation of microorganisms, and chemical decomposition. This study is concerned with the Fourier transform infrared spectrum (FT-IR) and ultraviolet-visible (UV-vis) absorption spectroscopy of the large 7-acetoxy-6-(2,3-dibromopropyl)-4,8-dimethylcoumarin molecule (abbreviated as 7AC) dissolved in ethanol and methanol solvents and their modification after atmospheric-pressure plasma treatment (APPT) with the DBD. The research is motivated by the significance of this molecule in different fields of application. Also the changes in the structure are recorded. After APPT, the peak corresponding to the carbonyl bond at a wavenumber of 1715 cm(-1) disappears in the IR spectrum of the ethanol solution, and when splitting at a wavenumber of 1405 cm(-1) is observed, the peak at 1224 cm(-1) is found to disappear after plasma is applied. It is seen new peaks at frequencies of 432 and 655 cm(-1) are formed. When the same situation is analyzed for the 7AC molecule dissolved in methanol, a new peak is observed at 1634 cm(-1). The intensities of the peaks at 3433 and 2075 cm(-1) also increase and there is a large change in the wavenumber at 600 cm(-1). In the UV spectra, a significant increase in the absorbance of the 7AC molecule dissolved in ethanol is observed after APPT, whereas a small decrease in the absorbance of the 7AC molecule dissolved in methanol is obtained. Owing to the lack of symmetry, many normal bands of vibrations are mixed.