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

It is common to measure the peak absorbance of the plasmonic nanoparticles in solution and then get the following:  Molarity (moles/liter) Number of particles per ml  Weight concentration (ug/ml) I wrote a small python function to extract these parameters.  The following inputs are needed for the function d_nm :   diameter of the particle in nanoparticle od Read More …

Coupled Dipole Approximation in Python

Coupled dipole approximation (CDA) method is a numerical method to calculate the optical properties (scattering and absorption) of interacting dipoles. This method is used in discrete dipole approximation method (like in DDSCAT software), where a big particle (also known as target) is broken into lot of interacting dipoles arranged in cubic lattice. CDA can also Read More …

Fitting Complex Metal Dielectric Functions with Differential Evolution Method

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 model shown below. $$\epsilon(\omega)=1-\frac{f_1\omega_p^2}{(\omega^2+i\Gamma_1\omega)}+\sum_{j=2}^{n}\frac{f_j\omega_p^2}{(\omega_{o,j}^2-\omega^2-i\Gamma_j\omega)}$$ The first term is Read More …

DDSCAT on amazon EC2

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 how easy it was to install Read More …