Theory of the Optical Properties of a DNA-Modified Gold Nanoparticle System

TL;DR

This paper presents a simple theoretical model for understanding the melting behavior and optical properties of DNA-modified gold nanoparticle aggregates, aligning well with experimental observations.

Contribution

It introduces a lattice-based model combined with the discrete dipole approximation to analyze optical changes during melting of nanoparticle-DNA systems.

Findings

Optical extinction changes sharply at melting transition.

Larger particles exhibit higher and narrower melting transitions.

Model predictions agree with experimental data.

Abstract

We describe a simple model for the melting and optical properties of a DNA/gold nanoparticle aggregate. The aggregate is modeled as a cluster of gold nanoparticles on a periodic lattice connected by DNA bonds, and the extinction coefficient is computed using the discrete dipole approximation. The optical properties at fixed wavelength change dramatically at the melting transition, which is found to be higher and narrower in temperature for larger particles, and much sharper than that of an isolated DNA link. All these features are in agreement with available experiments.