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
DNA-hosted silver clusters (Ag:DNAs) have attracted a lot of attention due to their small size (~20 atoms), wide range of applications in chemistry and biology, and sequence-dependent optical... Show moreDNA-hosted silver clusters (Ag:DNAs) have attracted a lot of attention due to their small size (~20 atoms), wide range of applications in chemistry and biology, and sequence-dependent optical tunability. Most of the previous studies are focused on the ensemble of emitters in solution. However, little is known about the optical properties of individual emitters, which is a crucial step towards understanding of their real nature, otherwise lost in ensemble averaging. We show that the excitation and emission spectra of individual emitters are broad even at 1.7 K (FWHM ~25 nm). Also, polarization measurements indicate that the excitation is not strongly dependent on the polarization of excitation light, whereas the emission is highly linearly polarized. Furthermore, from time-resolved measurements, we can conclude that the emission of single emitters can be fitted with single exponential decay curve, whereas the emitters organized with nanometer precision on the DNA scaffolds show double–exponential decay. This indicates the interaction between densely packed Ag:DNAs. Finally, we show that the DNA tubes can be used as a nano-contact glue between the colloidal particles functionalized with short DNA strands. Show less
