LiF Nanoparticles Enhance Targeted Degradation of Organic Material under Low Dose X-ray Irradiation

Felix Maye,Ayse Turak

doi:10.3390/radiation1020012

Abstract

The targeted irradiation of structures by X-rays has seen application in a variety of fields. Herein, the use of 5–10 nm LiF nanoparticles to locally enhance the degradation of an organic thin film, diindenoperylene, under hard X-ray irradiation, at relatively low ionizing radiation doses, is shown. X-ray reflectivity analysis indicated that the film thickness increased 12.04 Å in air and 11.34 Å in a helium atmosphere, under a radiation dose of ∼65 J/cm2 for 3 h illumination with a bi-layer structure that contained submonolayer coverage of thermally evaporated LiF. This was accompanied by significant modification of the surface topography for the organic film, which initially formed large flat islands. Accelerated aging experiments suggested that localized heating was not a major mechanism for the observed changes, suggesting a photochemical mechanism due to the formation of reactive species from LiF under irradiation. As LiF has a tendency to form active defects under radiation across the energy spectrum, this could could open a new direction to explore the efficacy of LiF or similar optically active materials that form electrically active defects under irradiation in various applications that could benefit from enhanced activity, such as radiography or targeted X-ray irradiation therapies.

Highlights

As a source of ionizing radiation, X-rays generate electrons, break bonds, or produce highly reactive free radicals in organic systems, such as polymers, small molecular weight molecules, DNA, and cells [1,2]
As lithium fluoride (LiF) has a tendency to form active defects under radiation across the energy spectrum, this could could open a new direction to explore the efficacy of LiF or similar optically active materials that form electrically active defects under irradiation in various applications that could benefit from enhanced activity, such as radiography or targeted X-ray irradiation therapies
We show that LiF nanoparticles were able to significantly enhance the local degradation of an organic thin film under hard X-ray irradiation at relatively low ionizing radiation doses

Summary

Introduction

As a source of ionizing radiation, X-rays generate electrons, break bonds, or produce highly reactive free radicals in organic systems, such as polymers, small molecular weight molecules, DNA, and cells [1,2]. Oxygen and moisture can react with the free radicals, excited state molecules, polarons, singlet or triplet excitons, or other charged components resulting in oxidative degradation [3,4,5]. Though this can often be undesirable, there are a number of applications were targeted irradiation damage can be utilized, such as in X-ray lithography [6], microradiography, [7], luminescent photonics [7,8], imaging [7], and treatment of drug-resistant bacteria or cancers [8,9,10,11]. An in-situ targeted approach that could enhances the local efficacy of low-dose

Methods

Results

Conclusion