Evaporation-Induced Assembly of Quantum Dots into Nanorings

Abstract

Herein, we demonstrate the controlled formation of two-dimensional periodic arrays of ring-shaped nanostructures assembled from CdSe semiconductor quantum dots (QDs). The patterns were fabricated by using an evaporative templating method. This involves the introduction of an aqueous solution containing both quantum dots and polystyrene microspheres onto the surface of a planar hydrophilic glass substrate. The quantum dots became confined to the meniscus of the microspheres during evaporation, which drove ring assembly via capillary forces at the polystyrene sphere/glass substrate interface. The geometric parameters for nanoring formation could be controlled by tuning the size of the microspheres and the concentration of the QDs employed. This allowed hexagonal arrays of nanorings to be formed with thicknesses ranging from single dot necklaces to thick multilayer structures over surface areas of many square millimeters. Moreover, the diameter of the ring structures could be simultaneously controlled. A simple model was employed to explain the forces involved in the formation of nanoparticle nanorings.

A colloidoscope of colloid-based porous materials and their uses

“…If a colloid-decorated substrate is wetted by a dispersion of nanoparticles, capillary forces confine the liquid to the necks in between particles and between the particles and the substrate during the drying process, leading to the formation of ring structures from nanoparticles deposited selectively at the contact points. 128 (B) Three-dimensional colloidal assemblies. Three-dimensional (3D) colloidal crystals are predominantly prepared by convective assembly processes in which the colloidal particles are deposited from a dispersion via a receding meniscus.…”

Evaporation of Droplets of Surfactant Solutions

“…Evaporation of liquid droplets in a gas volume has implications in different areas: spray drying and production of fine powders [1][2][3], spray cooling [4][5][6], fuel preparation [7-10], air humidifying [11], heat exchangers [12], drying in evaporation chambers of air conditioning systems [11,12], fire extinguishing [13,14], fuel spray auto ignition (Diesel) [15], solid surface templates from evaporation of nanofluid drops (coffee-ring effect) [16], spraying of pesticides [1][2][3], painting, coating and inkjet printing [17], printed MEMS devices, micro lens manufacturing, spotting of DNA microarray data [3,[18][19]. Because of such wide range of industrial applications this phenomenon has been under investigation for many years, both for pure fluids and for complex fluids.…”

Aharonov-Bohm quantum rings in high-Qmicrocavities

“…In order to estimate experimental conditions for the observation of the predicted emission spectra, we use the following values of the other system parameters: a typical radius of experimentally attainable 21,22,24 QRs, R = 20 nm, and the electron effective mass M = 0.05m e . This gives the energy scale of the QR interlevel separation ε QR 2 meV and the magnitude of the magnetic field, which produces a magnetic flux through the QR equal to a half of the flux quantum, B 2 T. Unless specified otherwise, all the calculations are made in the presence of a weak lateral electric field E ⊥ p with the magnitude E = 0.1ε QR /eR = 20 kV m −1 .…”

“…[11][12][13][15][16][17][18][19][20] On the other hand, there is a considerable interest in nonsimply-connected nanostructures, such as quantum rings (QRs), which have been obtained in various semiconductor systems. [21][22][23][24] This interest is caused by a wide variety of purely quantum mechanical topological effects which are observed in ringlike nanostructures and are absent in quantum dots. The star among them is the Aharonov-Bohm effect, 25,26 in which a phase of a quantum particle is influenced by a vector potential which results in magnetic-flux-dependent oscillations of the particle energy.…”