Dots, quantum

Empedocles S A, Norris D J and Bawendi M G 1996 Photoluminescence spectroscopy of single CdSe nanocrystallite quantum dots Phys. Rev. Lett. 77 3873-6... 

Clusters are intennediates bridging the properties of the atoms and the bulk. They can be viewed as novel molecules, but different from ordinary molecules, in that they can have various compositions and multiple shapes. Bare clusters are usually quite reactive and unstable against aggregation and have to be studied in vacuum or inert matrices. Interest in clusters comes from a wide range of fields. Clusters are used as models to investigate surface and bulk properties [2]. Since most catalysts are dispersed metal particles [3], isolated clusters provide ideal systems to understand catalytic mechanisms. The versatility of their shapes and compositions make clusters novel molecular systems to extend our concept of chemical bonding, stmcture and dynamics. Stable clusters or passivated clusters can be used as building blocks for new materials or new electronic devices [4] and this aspect has now led to a whole new direction of research into nanoparticles and quantum dots (see chapter C2.17). As the size of electronic devices approaches ever smaller dimensions [5], the new chemical and physical properties of clusters will be relevant to the future of the electronics industry. 

Empedocles S A and Bawendi M G 1997 Quantum-confined Stark effect in single CdSe nanocrystalline quantum dots Science 278 2114-17... 

Mews A et al 1994 Preparation, oharaoterization and photophysios of the quantum dot quantum well system CdS/HgS/CdS J. Phys. Chem. 98 934... 

Heath J R, Shiang J J and Alivisatos A P 1994 Germanium quantum dots optical properties and synthesis J. Chem. Phys. 101 1607... 

Micic O et at 1994 Synthesis and characterization of InP quantum dots J. Phys. Chem. 98 4966... 

Micic O I ef a/1996 Highly efficient band-edge emission from InP quantum dots Appi. Phys. Lett. 68 3150... 

Dabbousi B O ef a/1997 (CdSe)ZnS oore-shell quantum dots synthesis and oharaoterization of a size series of highly luminesoent nanoorystallites J. Phys. Chem. B 101 9463... 

Murray C B, Kagan C R and Bawendi M G 1995 Self-organization of CdSe nanoorystallites into three-dimensional quantum dot superlattioes Science 270 1335... 

Brus L E 1993 NATO ASI School on Nanophase Materials ed G C Had]lpanayls (Dordrecht Kluwer) Allvisatos A P 1996 Semiconductor clusters, nanocrystals and quantum dots Science 271 933 Heath J R and Shlang J J 1998 Covalency In semiconductor quantum dots Chem. See. Rev. 27 65 Brus L 1998 Chemical approaches to semiconductor nanocrystals J. Phys. Chem. Solids 59 459 Brus L 1991 Quantum crystallites and nonlinear optics App/. Phys. A 53 465... 

Bawendl M G, Stelgerwald M L and Brus L E 1990 The quantum mechanics of larger semiconductor clusters ( quantum dots ) Ann. Rev. Phys. Chem. 41 477... 

Guzellan A A et al 1997 Colloidal chemical synthesis and characterization of InAs nanocrystal quantum dots Appl. Phys. Lett. 69 1432... 

Cerullo G, De Silverstri S and Banin U 1999 Size-dependent dynamics of coherent acoustic phonons in nanocrystal quantum dots Phys. Rev. B 60 1928... 

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... 

Nanoclusters/Polymer Composites. The principle for developing a new class of photoconductive materials, consisting of charge-transporting polymers such as PVK doped with semiconductor nanoclusters, sometimes called nanoparticles, Q-particles, or quantum dots, has been demonstrated (26,27). 

Band gap engineetring confined hetetrostruciutres. When the thickness of a crystalline film is comparable with the de Broglie wavelength, the conduction and valence bands will break into subbands and as the thickness increases, the Fermi energy of the electrons oscillates. This leads to the so-called quantum size effects, which had been precociously predicted in Russia by Lifshitz and Kosevich (1953). A piece of semiconductor which is very small in one, two or three dimensions - a confined structure - is called a quantum well, quantum wire or quantum dot, respectively, and much fundamental physics research has been devoted to these in the last two decades. However, the world of MSE only became involved when several quantum wells were combined into what is now termed a heterostructure. 

Figure 7.5. Quantum-dot vertical-cavity surface-emitting semiconductor laser, svith an active layer consisting of self-assembled InojiGaAso s quantum dots (Fasor 1997),...

The birth of the field of carbon nanotubes is marked by the publication by lijima of the observation of multi-walled nanotubes with outer diameters as small as 55 A, and inner diameters as small as 23 A, and a nanotube consisting of only two coaxial cylinders [2]. This paper was important in making the connection between carbon fullerenes, which are quantum dots, with carbon nanotubes, which are quantum wires. FurtheiTnore this seminal paper [2] has stimulated extensive theoretical and experimental research for the past five years and has led to the creation of a rapidly developing research field. 

In conclusion, wc have shown the interesting information which one can get from electrical resistivity measurements on SWCNT and MWCNT and the exciting applications which can be derived. MWCNTs behave as an ultimate carbon fibre revealing specific 2D quantum transport features at low temperatures weak localisation and universal conductance fluctuations. SWCNTs behave as pure quantum wires which, if limited in length, reduce to quantum dots. Thus, each type of CNT has its own features which are strongly dependent on the dimensionality of the electronic gas. We have also briefly discussed the very recent experimental results obtained on the thermopower of SWCNT bundles and the effect of intercalation on the electrical resistivity of these systems. 

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. 

The bromination of the phenyl group in TgPhg has been reported by He et al. but few characterization data were given. The product, Tg[C6H4-Br]g, obtained in a 60% yield was subject to Pd catalyzed arylations to form the first organic-based quantum dot-like materials (Figure 19). ... 

Alivisatos, A. P. (1996). Semiconductor clusters, nanocrystals, and quantum dots. Science, 271 933-937. 

Costa-Fernandez, J. M. Pereiro, R. and Sanz-Medel, A. (2006). The use of luminescent quantum dots for optical sensing. Trends in Anal. Chem., 25,207-218. 

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