Coupled quantum dots

Ient93] Lent, C.S., P.D.Tougaw and W.Porod, Bistable saturation in coupled quantum dots for quantum cellular automata, Appl. Phys. Lett. 62 (1993) 714-716. 

Related effects have been noted in proton decay [Lane 1983] more recently for radiative decay in cavities [Kofman 1996], in Rabi oscillations betwen coupled quantum dots [Gurvitz 1997], in photodetachment [Lewenstein 2000]. See also [Facchi 2000 (a)]. 

Shiang J J et al 1998 Cooperative phenomena in artificial solids made from silver quantum dots the importance of classical coupling J. Phys. Chem. 102 3425... 

Chen, J. C., Chang, A. M. and Melloch, M. R. (2004) Transition between quantum states in a parallel-coupled double quantum dot. Phys. Rev. Lett., 92, 176801-1-176801-4. 

In addition to the photoluminescence red shifts, broadening of photoluminescence spectra and decrease in the photoluminescence quantum efficiency are reported with increasing temperature. The spectral broadening is due to scattering by coupling of excitons with acoustic and LO phonons [22]. The decrease in the photoluminescence quantum efficiency is due to non-radiative relaxation from the thermally activated state. The Stark effect also produces photoluminescence spectral shifts in CdSe quantum dots [23]. Large red shifts up to 75 meV are reported in the photoluminescence spectra of CdSe quantum dots under an applied electric field of 350 kVcm . Here, the applied electric field decreases or cancels a component in the excited state dipole that is parallel to the applied field the excited state dipole is contributed by the charge carriers present on the surface of the quantum dots. 

Dendrimers can be used to effectively coat and passivate fluorescent quantum dots to make biocompatible surfaces for coupling proteins or other biomolecules. In addition, the ability of dendrimers to contain guest molecules within their three-dimensional structure also has led to the creation of dendrimer-metal nanoclusters having fluorescent properties. In both applications, dendrimers are used to envelop metal or semiconductor nanoparticles that possess fluorescent properties useful for biological detection. 

The following sections discuss many of the major particle types and provide bioconjugation options for the coupling of ligands to the surface of functionalized particles. Some additional nanoparticle constructs, including gold particles, dendrimers, carbon nanotubes, Buckyballs and fullerenes, and quantum dots are discussed more fully elsewhere (see Chapter 7 Chapter 9, Section 10 Chapter 15 and Chapter 24). 

Evident Technologies (2005) Coupling of sulfhydryl-modified oligonucleotides to amine-EviTags using BMPA and EDC, web site quantum dot protocols. 

Gryczynski I, Malicka J, Jiang W, Fischer H, Chan WCW, Gryczynski Z, Grudzinski W, Lakowicz JR (2005) Surface-plasmon-coupled emission of quantum dots. J Phys Chem B 109 1088-1093... 

Chromatographic approaches have been also used to separate nanoparticles from samples coupled to different detectors, such as ICP-MS, MS, DLS. The best known technique for size separation is size exclusion chromatography (SEC). A size exclusion column is packed with porous beads, as the stationary phase, which retain particles, depending on their size and shape. This method has been applied to the size characterization of quantum dots, single-walled carbon nanotubes, and polystyrene nanoparticles [168, 169]. Another approach is hydro-dynamic chromatography (HDC), which separates particles based on their hydro-dynamic radius. HDC has been connected to the most common UV-Vis detector for the size characterization of nanoparticles, colloidal suspensions, and biomolecules [170-172]. 

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