Calculating molarity, weight concentration from absorbance value for plasmonic nanoparticles in solution

Posted on Wed 20 June 2018 in Plasmonics

It is common to measure the peak absorbance of the plasmonic nanoparticles in solution and then get the following:

  1. Molarity (moles/liter)
  2. Number of particles per ml
  3. Weight concentration (ug/ml)

I wrote a small python function to extract these parameters.  The following inputs are needed for the function

  1. d_nm …

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Fitting Complex Metal Dielectric Functions with Differential Evolution Method

Posted on Wed 13 April 2016 in Plasmonics

The real and imaginary part of dielectric permittivity of the metals is important to simulate the optical properties of metal films and nanoparticles. Permittivity data is obtained experimentally by ellipsometry and is fitted with analytical models. The most common model for fitting experimental data is with Drude-Lorentz …

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Generating plasmonic metal dielectric functions in Python

Posted on Thu 10 September 2015 in Plasmonics • Tagged with Python

I keep needing a python code to generate the dielectric functions of plasmonic materials such as Au, Ag, Pd, and Pt. So I wrote a python version of LD.m.

LD.m is a matlab file written by Bora Ung …

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DDSCAT on amazon EC2

Posted on Thu 03 September 2015 in Plasmonics • Tagged with DDSCAT

Amazon provides high performance computing capabilities through their EC2 service. You can find more information here

They provide a 750 hr free instance with their a free-tier program. If you want more resources, you can pay for it. See the pricing, pricing seem very reasonable.

I wanted to see …

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Plasmonic Materials in MEEP > 1.2

Posted on Sat 13 June 2015 in Plasmonics • Tagged with electromagnetism, FDTD, MEEP, octave, Plasmonics

Here is how I was implementing plasmonic materials in meep 1.1. Unlike Meep 1.1, Meep >= 1. 2 changed the way materials are defined.

Here I will describe how to change the material definition code from meep1.1 to meep 1.2 . Please note that one can still use …

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Electric field at localized plasmon resonance using MEEP

Posted on Tue 22 January 2013 in Plasmonics • Tagged with electromagnetism, FDTD, MEEP, Plasmonics

This article is about simulating localized plasmon resonances in metal nanospheres using MEEP package. Generally, I am interested in solving three problems in LSPR systems:

Calculate the extinction, scattering, absorption spectra of metal nanoparticle

The procedure for doing this is very similar to the method I mentioned here.

Calculating the …

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Surface plasmon dispersion relation for thin metal films

Posted on Wed 07 December 2011 in Plasmonics • Tagged with electromagnetism, octave, Plasmonics


A thin metal film in dielectric (also known as dielectric-metal-dielectric configuration) can support surface plasmons that are different in nature to the ones observed in thick metal-dielectric interfaces. Unlike, a single mode that is observed in thick metal film, thin metal films exhibit two types of modes for the …

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Scattering / extinction / absorption cross-sections of silver nanowires (infinite cylinders) using meep

Posted on Wed 01 June 2011 in Plasmonics • Tagged with electromagnetism, FDTD, MEEP, octave, photonics, Plasmonics

Particles scatter and absorb electromagnetic radiation. One often needs to compare the amount of scattering/absorption/extinction for particles of different shapes, composition, sizes and incident light properties (polarization, frequency and angle). In this regard, the concept of cross-sections comes into picture. There are three types of cross-sections, 1) scattering …

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Arbitrary 2d shapes in MEEP

Posted on Tue 10 May 2011 in Plasmonics • Tagged with electromagnetism, FDTD, MEEP, octave, photonics, Plasmonics

In MEEP (1.1.1), dielectric structures are often created by constructive geometry (adding and subtracting primitive shapes). The primitive shapes that are allowed are blocks, cylinders, ellipsoids and cones. To create a complex shape, one has to decompose the geometry into these primitive shapes. Over the weekend, I was …

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Plasmonic materials in MEEP

Posted on Wed 27 April 2011 in Plasmonics • Tagged with electromagnetism, FDTD, Free Software, Matlab, MEEP, octave, photonics, Plasmonics, SERS


The aim of this post is to share my experience in incorporating dielectric function of metals such as gold and silver into MEEP (a free finite difference time domain package) code. The incorporation is not an easy task and can be daunting for the first time user.

Metals such …

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