B Some Questions About Gold Nanoparticles

[pauladancer]

Hello!
I am in my last year of high school physics, and for our final project we are given the opportunity to research a topic we are interested in. My chosen subject is the use of gold nanoparticles in cancer treatment. Although I have just begun my research, I am having a tough time finding answers to a few of my questions. Some of them I have no idea how to answer and some of them I have a general idea of what is going on, but I just want to ensure that I have the right information before I put it into my project. The questions that I have at the moment are:

On an atomic level, why do the gold nanoparticles heat up when exposed to infrared EMR?
Why are scientists using the wavelength of EMR that they are using? (approx. 782 nm)
Since this is below the threshold frequency of gold, the photoelectric effect will not occur. Would an ejected electron not damage the cancer further or would it cause more damage to healthy cells?
Does the Compton effect occur in this type of treatment? Does it have different advantages/disadvantages than using the photoelectric effect?

These are all of the questions I can think of right now, and I'm sure I'll have more in the future once I get deeper into my research. Any help would be greatly appreciated, even if you could just point me in the right direction in terms of a paper to read or something along those lines. I'm so excited to learn more about this topic and look forward to reading your answers. Thank you! :)

 

[jedishrfu]

This article may help

http://www.physicscentral.com/explore/action/pnb-nanotherapy.cfm

 

[pauladancer]

This article may help

http://www.physicscentral.com/explore/action/pnb-nanotherapy.cfm

Thank you! This looks like it will be a very useful article in my research.

 

[erioizanami]

Hey pauladancer,

To answer a few of your questions:
On an atomic level, why do the gold nanoparticles heat up when exposed to infrared EMR?
This is due to the absorption of the incident photons. In quantum physics you learn that photons ("particles of light") have a small amount of momentum and that when a photon is absorbed by a crystal this momentum is absorbed by the crystal lattice. This increase in momentum causes vibrations in the crystal lattice, which correlates directly to the temperature of the particle.

Why are scientists using the wavelength of EMR that they are using?
The wavelength of the incident light is chosen so that the tissues of the body do not block the light from getting to the particles. Note that a smaller wavelength (energy of a photon is inversely related to the wavelength, meaning that a smaller wavelength will have higher energy) may result in the particles getting hotter faster, but the light will be blocked by the surrounding tissues in the body.

Since this is below the threshold frequency of gold, the photoelectric effect will not occur. Would an ejected electron not damage the cancer further or would it cause more damage to healthy cells?
Note that in order for the photoelectric effect to occur the incident photons must have a certain "threshold energy". For gold, the energy needed to eject an electron is fairly high, and thus a photon with a correspondingly small wavelength is needed to make this occur. We learned earlier that the tissues of the body block photon of small wavelengths, this makes the ejection of an electron from the gold nano particle impossible within the cell without destroying the surrounding tissue as well.

Does the Compton effect occur in this type of treatment? Does it have different advantages/disadvantages than using the photoelectric effect?
The Compton effect always occurs, but in this case it is unrelated to the mechanism by which these particles work. To elaborate, you learn in solid-state physics that electrons contribute minimally to the specific heat of a material, therefore the increased momentum of an electron doesn't contribute much to the temperature of the material.

Hope this helps a bit. :)

 

[pauladancer]

Thank you so much! That really helps me to understand the topic better. I will definitely refer to this when I'm doing my write up (: