Hi, I am trying to learn the theoretical modelling of silver nanoparticle using the Mie scattering theory. After that, I discovered a software named Mieplot developed by Philip Laven, where it solved the problem. But, I am still in the learning mood to understand the basic about it.
During the modelling, I was trying to find out the spectra of silver nanoparticle for different particle sizes where the surrounding medium is water. I have observed that for particle size with a diameter of 50 nanometer, it appears a small shoulder near the bigger peak. But, the smaller peak is becoming more bigger while I am increasing the particle size of nanoparticle. It is showing 2 peaks with a particle size of 100 nanometer. I have attached the spectrum of 50 nanometers 100 nanometers.
Please, anyone could help me with a suggestion what is the significance of these two peaks for silver nanoparticle? While the other particles like gold are not showing this phenomenon. What reason behind this? Thank you.
Shaon Debnath
OK, I have just a little time now so will provide you with some background webinar material (registration required). The first webinar will explain the basis of Mie theory (it's named after a person, Gustav Mie, so Mie is always with upper case). Look at the resonances within the (small) particle - these can be responsible for multiple peaks:
The life of Gustav Mie and the development of the Lorenz-Mie solution to Maxwell’s equations
https://www.malvernpanalytical.com/en/learn/events-and-training/webinars/W140225Gustav-mie-maxwell.html
Here's something general on Ag colloids and then metal colloids. I spent my Ph.D time in the 70's (that's the 1970's not my 70's) on this topic:
Silver colloids and invisible ink
https://www.malvernpanalytical.com/en/learn/events-and-training/webinars/W150902SilverColloidInvisibleInk.html
Metal colloids - their preparation, application and characterization
https://www.malvernpanalytical.com/en/learn/events-and-training/webinars/W160218MetalColloids.html
I'll revert next week to your specific question in MiePlot.
BTW, I avoided borohyride reduction like the plague - everything gets contaminated with intractable B which has adverse effects in many applications.
Shaon Debnath
What optical properties and wavelengths are you using? MiePlot is an excellent program, by the way. Remember all ’real world’ Ag has an oxide film on the surface - this affects all and is responsible for the bactericide properties. Your end application is?
Dear Dr Alan,
Many many thanks for your prompt reply.
The spectra that I have attached, is not my experimental spectra. During using the Mie Plot software, I was trying to see the theoretical spectra of silver nanoparticles how it is shiting the peak wavelength. As I have chosen monodisperse silver nanoparticle, why I am having the two peaks in the spectra?
I am trying to use the surface plasmon resonance property of silver nanoparticle to develop a pH sensor.
Thank you.
Shaon Debnath
I know it’s a theoretical spectrum. I’m very familiar with MiePlot. The optical properties of the particle (real and imaginary parts of the RI) are vital in this size region. What did you use for silver? It’s not apparent from the plots.
For small silver particles, a core-shell model could be considered more appropriate but we’ll address this later.
Dear Dr. Alan,
I am a new use of Mie Plot, so I am trying to learn it by myself.
In the software, I went to the option of Advanced-Sphere-Silver. Similarly, I have chosen the surrounding medium with water. Then I have selected Qext/Qsca/Qabs Vs. wavelength option to run the plot.
I have synthesized the silver nanoparticle using Sodium borohydride, Trisodium citrate then I got the absorption spectra using a UV-Vis spectrophotometer.
Now, I am looking to fit or compare the absorption spectra that I have obtained from the UV-Vis spectrometer with the mie plot.
Please, I will highly appreciate your suggestion about Mie plot to understand it very well. Thank you.
Shaon Debnath
OK, I have just a little time now so will provide you with some background webinar material (registration required). The first webinar will explain the basis of Mie theory (it's named after a person, Gustav Mie, so Mie is always with upper case). Look at the resonances within the (small) particle - these can be responsible for multiple peaks:
The life of Gustav Mie and the development of the Lorenz-Mie solution to Maxwell’s equations
https://www.malvernpanalytical.com/en/learn/events-and-training/webinars/W140225Gustav-mie-maxwell.html
Here's something general on Ag colloids and then metal colloids. I spent my Ph.D time in the 70's (that's the 1970's not my 70's) on this topic:
Silver colloids and invisible ink
https://www.malvernpanalytical.com/en/learn/events-and-training/webinars/W150902SilverColloidInvisibleInk.html
Metal colloids - their preparation, application and characterization
https://www.malvernpanalytical.com/en/learn/events-and-training/webinars/W160218MetalColloids.html
I'll revert next week to your specific question in MiePlot.
BTW, I avoided borohyride reduction like the plague - everything gets contaminated with intractable B which has adverse effects in many applications.
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