Vila Verde, ASA; (2012) Computational study of defects and heat transfer in gold nanostructures. Doctoral thesis , UCL (University College London).

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Abstract

Gold nanoparticles are promising tools for cancer therapy and cell imaging due to their non-toxicity, high heat conduction and tunable optical properties for the infraredvisible region. Nanoparticles production often involves thermal annealing, a process that changes the structure of the nanoparticle by mechanisms that are not yet well understood. For any of the biomedical applications, the nanoparticles are organically-coated to allow targeting and efficient uptake by cancer cells. Once the nanoparticles are inside the cell, their optical tunability allows the use of specific wavelengths strongly absorbed or scattered by the particles but poorly interacting with the medium to induce hyperthermia or obtain an image of the cell. In any case, the nanoparticle is expected to heat up. Although the propagation of heat is well understood at the macroscale, the details of the heat transfer at the nanoscale are still poorly understood. In this work, we use classical, equilibrium molecular dynamics simulations to create nanoparticles and investigate how their crystalline structure and the number and type of defects evolves as a function of annealing conditions. We use both analytical methods and classical non-equilibrium molecular dynamics simulations to investigate the effects of the particle size and the type of interface on the heat transfer properties of bare and organic-coated gold nanoparticles embedded in water. Water was chosen to mimic the cellular medium because it is the most abundant cellular component. Our simulations with a slab system of water and gold suggest that the material present at the interface between the gold and the water affects the heat transfer in the system. Moreover, our analytical calculations and computational results indicate that the heat transfer is dominated by the heat conduction in the medium for large nanoparticles, while for smaller nanoparticles the interface controls the overall heat propagation.

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