Browsing by Subject "Orientation control"

Now showing 1 - 3 of 3

Open Access
Liquid interface self-assembly with colloidal quantum wells
(Springer Singapore, 2022-10-28) Erdem, Onur; Demir, Hilmi Volkan
In this chapter, we discuss our methodologies for the self-assembly of colloidal nanoplatelets (NPLs) at the liquid interface. We also review other recent studies on orientation-controlled platelet assembly on liquid interfaces. We compare the results of the reported studies and discuss the parameters that affect the NPL orientation at the liquid interface.
Open Access
Liquid-interface orientation-dictated self-assembly of colloidal semiconductor nanocrystals and its applications
(2023-08) Waris, Mohsin
Over the past, different techniques have been used for the self-assembly of nanocrystals (NCs). Recently, the orientation control over the assembly of anisotropic NCs has been achieved using liquid-interface self-assembly, which is a simple yet vastly applicable technique. Here, we propose and show the first account of the application of this method to assemble multi-layered alternating-orientation NC films, with distinct orientation control of our choice over the NCs in each layer. Being laterally atomically flat, these anisotropic NCs belong to a class of quasi-two-dimensional nanocrystals with one confined dimension. Exhibiting extraordinarily large absorption cross-sections, ultra-narrow emission linewidths, and intrinsic structural anisotropy, these nanoplatelets (NPLs) possess characteristics comparable to those of epitaxially grown quantum wells, though while offering low-cost solution-based synthesis and processability at the same time. Due to this anisotropy, the emission of these NPLs is directional with mostly in-plane transition dipole moments, making them favorable for a variety of optoelectronic active media with orientation control over their deposited films. To achieve this, we have assembled the NPL films with one defined orientation and successfully attained their orientation control using macroscopic parameters, including the evaporation rate of the solvent and subphase selection to be used as the active layers for a number of optoelectronic devices. We demonstrated different multi-layered structures of these NPLs with varying orientations. The resulting surface roughness in all these films was successfully kept, on average, with Sq smoother than 2 nm. We further extended this self-assembly technique to different classes of nanocrystals including large hexagonal NPLs (with around 100 nm in lateral dimensions) and cubic quantum dots (with around 15 nm on each side) to show the versatility of our method. The findings of this thesis indicate that our orientation-dictated self-assembly approach holds great promise for constructing complex colloidal structures made of these oriented nanocrystals as the building blocks.
Open Access
Orientation and control of a flexible spacecraft: planar motion
(IEEE, 1990) Morgül, Ömer
We consider a flexible spacecraft modeled as a rigid body which rotates in an inertial frame; a light flexible beam is clamped to the rigid body at one end and free at the other end. We assume that the flexible spacecraft performs only planar motions. We pose two control problems; namely, the orientation and the stabilization of the system. It is shown that suitable boundary controls applied to the free end of the beam and suitable control torques applied to the rigid body solve the problems posed above.