When metal chalcogen is exposed to gamma radiation, what are parameters that related to nano size?
Here is an application of nanoparticles
for detection of radiation. Glass that
lights up upon being irradiated is processed
to nanoparticles smaller than the wavelength
of blue light. As an effect, scattering
of the light is avoided.
http://www.newscientist.com/blogs/onepercent/2012/05/jesse-emspak-contributora-pair.html
Regards,
Joachim
Here is an application of nanoparticles
for detection of radiation. Glass that
lights up upon being irradiated is processed
to nanoparticles smaller than the wavelength
of blue light. As an effect, scattering
of the light is avoided.
http://www.newscientist.com/blogs/onepercent/2012/05/jesse-emspak-contributora-pair.html
Regards,
Joachim
Hi Ahmed,
That's a good question. I'm assuming that you are interested in dose enhancement from nanoparticles which is quite contentious. Ultimately, x-rays and gamma rays could interact with a gold nanoparticle to cause ionization. This theoretically could produce a dose enhancement in two ways: 1) through increased photoelectric absorption relative to a similar volume of tissuse and 2) through the emission of auger electrons.
I'll start with the auger electrons. These electrons have very low energies - typically below 100 eV - which is a problem. According to NISTs ESTAR website, a 10 keV electron (100 times more energetic than the auger electron) has a linear range in water of only 2 micrometers. Therefore, a 10 keV photo-electron (much-less an auger electron) would not have sufficient energy to penetrate into a cell's nucleus to cause a strand break.
Next, is the photoelectric effect on gold. This is more effective and could cause a dose enhancement since the photo-electrons are energetic and because the gold will have a higher photoelectric cross section relative to water (tissue). Yet, for everything I've seen, the concentrations of gold nanoparticles needed to cause a dose enhancement are on the order of several mg per gram of tissue - which is extremely high and toxic to a cell.
I think that one potentially interesting line of research with nanoparticles is getting them to transport preferentially into a cell nucleus. A vast majority of this type of research that I've seen has been using non-radioactive techniques to kill tumor cells.
Dear David
Over the past years, we have conducted some experiments on the radiation attenuation properties of nano-sized and micro-sized materials. As you believe that the dose enhancement of nanoparticles is due to 1) increased photoelectric absorption and 2) the emission of auger electrons, can you explain how nano-sized materials have more photoelectric interactions per unit mass for photons with a specific energy?
We previously showed that nano-structured WO3/PVC samples present a significant greater potential in absorbing low energy X-ray photons compared to that of the samples produced with microstructured WO3/PVC. We also reported that the smaller size of the nano-structured WO3 particles can guarantee a better radiation shielding property. However, we did not study the mechanisms of this phenomena. The abstract of our paper that is published in the Medical Physics International Journal is enclosed.
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