Characterization of Proton-Irradiated Polyaniline Nanoparticles Using Terahertz Thermal Spectroscopy

Seung Jae Oh,Yoochan Hong,Jin-Suck Suh,Yong-Min Huh,Ki-Young Jeong,Inhee Maeng,Jaemoon Yang

doi:10.3390/cryst11070765

Abstract

In this study, we investigated the changes in the molecular structure of polyaniline (PANI) nanoparticles illuminated by a proton beam using terahertz (THz) thermal spectroscopy based on the terahertz time-domain spectroscopy technique. PANI nanoparticles in water were exposed to a proton beam of 35 MeV energy with a particle fluence of 1013 particles/cm2. The photothermal properties of this solution of PANI nanoparticles were characterized using THz thermal spectroscopy. We measured the changes in the amplitudes of the reflected THz pulses to identify the variations in temperature induced by the photothermal effects of the PANI nanoparticle solution. The amplitude of a reflected THz pulse of the PANI solution not exposed to the proton beam increased when illuminated by an infrared light source, whereas that of THz signals of the PANI solution exposed to the proton beam hardly exhibited any changes. This implies that the molecular structure of PANI nanoparticles can be varied by a proton beam with a particle fluence above 1013 particles/cm2.

Highlights

Recent advances in cancer treatment technologies allow direct removal of tumors using various non-contact methods, such as radiation therapy using proton or neutron rays, ultrasound, laser, and thermal therapy [1]
Owing to the advances in nanotechnology, tumor removal by localized thermal therapy based on targeted photothermal nanoparticles, wherein the local temperature is increased by laser irradiation, has been increasingly studied [4]
When fusion therapy using radiation and localized photothermal treatment is considered, the changes in the material properties of photothermal nanoparticles which could be occurred during radiation therapy must be evaluated because, unlike metal nanoparticles, polymer nanoparticles we used can be distorted and the photothermal efficiency of the nanoparticles could be decreased under the illumination of proton or neutron rays

Summary

Introduction

Recent advances in cancer treatment technologies allow direct removal of tumors using various non-contact methods, such as radiation therapy using proton or neutron rays, ultrasound, laser, and thermal therapy [1]. Owing to the advances in nanotechnology, tumor removal by localized thermal therapy based on targeted photothermal nanoparticles, wherein the local temperature is increased by laser irradiation, has been increasingly studied [4] This therapy kills only targeted cancerous tissues rather than normal tissues. THz time-domain spectroscopy (THz-TDS) can directly measure the temperature of the water without contact and enable to obtain the temperature distribution of layer between the plastic well dish and water under the laser irradiation. Such advantages of THz-TDS allowed the development of THz photothermal imaging, which could perform targeted cancer imaging using targeted nanoparticles [10,11]. We investigated the thermal properties of PANI nanoparticles with and without proton irradiation using THz thermal spectroscopy to verify its applicability in the non-contact monitoring of photothermal effects

PANI Particles and Proton Beam Irradiation

Terahertz Thermal Spectroscopy