PNNL-13501 - Pacific Northwest National Laboratory

Examination of the Use of Diazoluminomelanin as a Component of a Three-Dimensional Imaging
System for Localization of Ionizations Due to Boron Absorption of Neutrons
Study Control Number: PN00042/1449
John A. Leonowich, Matthew H. Smith
Diazoluminomelanin is a unique biopolymer that has found use in the field of radio frequency radiation dosimetry.
Investigation of diazoluminomelanin’s response to ionizing radiation will provide information on a material that could be
used to perform dosimetry on more than one physical agent and that could contribute to improved ionizing radiation
dosimetry for medical treatment and occupational safety.
Project Description
The purpose of this project was to determine whether
diazoluminomelanin would respond to ionizing radiation,
particularly neutrons. The response of diazoluminomelanin
to radio frequency radiation has already been
investigated and is the subject of continuing research by
the Air Force Research Laboratory. Obtaining an output
signal from diazoluminomelanin can be difficult due to
self absorption of light emission. Evaluation of solids
containing diazoluminomelanin did not yield an output
signal significantly above background. However,
measurement methods using diazoluminomelanin in
liquid form are presently being evaluated for response to
ionzing radiation. These methods are similar to processes
currently used to perform radio frequency radiation
measurements. Once a response to ionzing radiation is
established, diazoluminomelanin will be incorporated into
human phantoms for use in determining radiation dose for
medical applications and verifying the performance of
phantoms used to calibrate in vivo counting systems.
Introduction
Diazoluminomelanin is a unique biopolymer, because it
exhibits the properties of luminescence, fluorescence, and
slow fluorescence with a broad optical absorption
spectrum. When it is properly activated, diazoluminomelanin
can absorb and store electromagnetic radiation
energy, and on subsequent activation, diazoluminomelanin
can release that energy via rapid luminescence
followed by slow fluorescence. Its ionic state can be
manipulated after its synthesis, resulting in different
extents of oxidation and reduction. Considerable work
has been done on exploring the response of
diazoluminomelanin to radio frequency radiation.
The work on this project is focused on investigating the
response of diazoluminomelanin to ionizing radiation.
While diazoluminomelanin has primarily been used in
liquid form for radio frequency dosimetry, efforts were
made on this project to use diazoluminomelanin in a
solid form. One problem encountered using this method
is the self-absorption of light emitted by
diazoluminomelanin during fluorescence. Once this
problem is overcome, the energy- and dose-dependent
properties of diazoluminomelanin will be investigated.
The long-term goal is to demonstrate the use of
diazoluminomelanin in human phantoms using threedimensional
imaging equipment to capture light emission.
This application will benefit ionizing radiation dosimetry
for medical treatment and occupational safety.
Results and Accomplishments
Diazoluminomelanin in a solid form was investigated
using three different preparations. First, undiluted
diazoluminomelanin was allowed to dry on filter paper
media. Second, diazoluminomelanin was diluted with
sodium hydroxide prior to drying on the filter paper.
Third, diazoluminomelanin was incorporated into a solid
foam material.
After exposure to ionizing radiation, a readout of delayedfluorescence
was attempted by stimulating the samples
with ultraviolet light (365 nm) and observing for
fluorescence at 486 nm. A fluorescence signal above
background was difficult to discern. This was most likely
due to self-absorption of the light signal in the diazoluminomelanin.
This phenomena has been noted during
the radio frequency dosimetry studies of diazoluminomelanin.
Further dilution of the diazoluminomelanin is
proposed as a way to overcome this problem.
Human Health and Safety 289