To realize optical manipulation and measurement for isolated quantum dots (QDs) in gaseous phase, we are developing experimental apparatus for dispersing QDs into a gas by using droplets of organic solvents. The droplet was generated with a nebulizer using a piezoelectric element and was monitored by observing the scattered light. The time variation of the QD density was also monitored by observing the fluorescence from the QDs. In the case of the diethyl ether solution of CdSe/ZnS core-shell type QDs, it was confirmed that the evaporation of the droplet was enhanced with a liquid-nitrogen trap and its typical lifetime was roughly 30 s, which was considered to be determined from the descent by the force of the gravity, the evaporation, and the diffusion.
Superfluid helium having extremely low temperature, negligibly small viscosity, and huge thermal conductivity provides us a unique opportunity to generate a novel cryogenic space for the fabrication of nanostructures and the manipulation of their motion. Here we fabricated metallic nano- and micro-particles by laser ablation in superfluid helium and selectively trapped superconducting particles with a quadrupole magnetic field utilizing perfect diamagnetism caused by Meissner effect. We also discuss the size dependence of the superconducting transition temperatures of the trapped metallic particles by changing the temperature of liquid helium.
The emission spectra of CdSe/ZnS core-shell dots have been monitored after the dilution of their toluene solution with organic
solvents (toluene, n-hexane, diethyl ether, acetone, ethanol, and methanol). In addition to the well-known difference of the emission
efficiency according to the solvent, we found their time variation depending on the solvent. From the discussion based on the solubility
of the capping organic ligand, hexadecylamine (HDA), to each solvent it is suggested that the observed time variation is caused by the
liquation of the capping molecules form the dot surface and the resulting change of the number of the trap site for charges in the