In this work, we investigate the minute circular dichroism effects of single nanoparticles.To this aim, we apply photothermal imaging with a polarization-modulated heating beam. This new technique,... Show moreIn this work, we investigate the minute circular dichroism effects of single nanoparticles.To this aim, we apply photothermal imaging with a polarization-modulated heating beam. This new technique, which we call photothermal circular dichroism microscopy, probes circular dichroism in an absorption measurement, unlike other techniques which usually probe the extinction. We also investigate in detail how to avoid measurement artefacts such as leakage of linear dichroism and residual intensity modulation.We then study the CD of formally achiral and wet-chemically synthesized chiral nanoparticles. We find that the achiral spherical-like particles, can exhibit considerable circular dichroism, some of them display almost as strong CD as specially designed chiral particles. Furthermore, we find that the control of handedness of the synthesized chiral particles is only limited and that, even from a geometric perspective, the relation between the 3D shape of these particles and their handedness is not straightforward.In the last chapter, we apply our method to magnetic samples which exhibit circular dichroism through their magnetization but not due to their shape. The excellent sensitivity of photothermal microscopy not only allows us to perform magnetic imaging of particles, but we also succeeded in obtaining magnetization curves of single particles and estimating their magnetization. Show less
Gold nanoparticles show surprisingly strong interactions with light in the visible range, which can be divided into scattering, absorption, and photoluminescence. When a nanoparticle absorbs light,... Show moreGold nanoparticles show surprisingly strong interactions with light in the visible range, which can be divided into scattering, absorption, and photoluminescence. When a nanoparticle absorbs light, the corresponding energy is converted to heat, which can affect the environment of the (hot) nanoparticle. This thesis uses scattering and photoluminescence to study the behaviour of optically heated single gold nanoparticles: it discusses the behaviour of single plasmonic vapour nanobubbles, which occur around highly heated nanoparticles immersed in a liquid, the detection of chirality in nano-objects through their absorption and the photothermal effect, the behaviour of gold nanoparticles under sub-picosecond pulsed excitation, and the temperature dependence of pulse-excited photoluminescence of such particles. Show less
