Quantum dots system

First of all, we formulate a standard discrete-level model to describe nanoscale interacting quantum systems (quantum dot, system of quantum dots, molecule, below nanosystem , central system , or simply system ) coupled to free... 

These observations and one further criterion start to define quantum dot systems. The second major possibility is the coating of the central particle with a second material e.g. CdS or ZnS on top of CdSe. When a wider band gap material is coated onto the outside of a narrow band gap material the confinement on the core is enhanced, leading to enhanced optical properties, especially photoluminescence efficiencies. 

We have studied the optical properties of a novel microcavity - quantum dot system consisting of a melamine formaldehyde latex microsphere coated by a thin shell of CdTe nanocrystals. The coupling between the emission from nanocrystals and spherical cavity modes was realized. Periodic narrow peaks of the emission spectra corresponding to the whispering gallery modes were detected and a threshold behavior of the emission intensity on excitation power was observed. 

Matrix-stabilized (glass, NaCl) CuCl nanocrystals is a typical zero-dimensional material, which constitutes a quantum dot system in which excitons are weakly confined [4]. Small angle X-ray scattering study has established that the resultant... 

Small nanocrystals of ZnS and of its chemical twin CdS have been found to behave as quantum dots — systems with physical properties intermediate between those of bulk materials and single molecules [144,234,237-242]. Accordingly, these nanoparticles have drawn much attention as promising fluorescent labels for biology, so that the interaction of proteins and nucleic acids with the CdS and ZnS quantum dots has been intensively studied (see [242-248] for reviews). It is noteworthy that the ZnS particles obtained from hydrothermal vent plumes could pass through 200 nm filters [249] and, hence, can be reasonably categorized as nanoparticles. 

Chen, H., R. Li, L. Lin, G. Guo, and J. M. Lin. 2010. Determination of L-ascorbic acid in human serum by chemiluminescence based on hydrogen peroxide-sodium hydrogen carbonate-CdSe/CdS quantum dots system. Talanta 81 1688-1696. 

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. 

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

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. 

In the traditional lithography approach, researchers continued to consider the idea that modem STM (scanning tunnel Microscopy) could be the proper tool for the formation of two-junction systems when working with very small particles. This consideration had related the studies of single-electron phenomena to the concept of quantum dots (Glazman and Shechter 1989). 

Moreover, the possibility of considering single-electron phenomena in a frame of a dot-based system theory allows consideration of even semiconductor nanoparticles as quantum dots, useful for single-electron junctions (Averin et al. 1991). 

The approach described represents one more step toward the realization of a completely stand-alone single-electron junction based on nanoparticles and produced in organic matrix. Quantum dot synthesis directly on the tip of a metal stylus does not require the use of STM for localizing the particle position and requires only the use of atomically flat electrodes and a feedback system for maintaining a desirable double-barrier structure. 

Particularly attractive for numerous bioanalytical applications are colloidal metal (e.g., gold) and semiconductor quantum dot nanoparticles. The conductivity and catalytic properties of such systems have been employed for developing electrochemical gas sensors, electrochemical sensors based on molecular- or polymer-functionalized nanoparticle sensing interfaces, and for the construction of different biosensors including enzyme-based electrodes, immunosensors, and DNA sensors. Advances in the application of molecular and biomolecular functionalized metal, semiconductor, and magnetic particles for electroanalytical and bio-electroanalytical applications have been reviewed by Katz et al. [142]. 

Although the studies with SPD techniques have provided significant results on the intermittency in quantum dots, the systems of observation were limited to immobile quantum dots in solids, such as polymer films and glass matrices. The immobilization results in intrinsic heterogeneity of the local environment around each quantum dot the SPD cannot cover the photophysical kinetics in quantum dots in solution of a more homogeneous environment. In addition, the SPD approaches needed conventional bin-time longer than 10 ms for reliable determination of on and off states. This also limits the elucidation of relaxation dynamics for shorter time scales. 

Swift, J. L., Heuff, R. F. and Cramb, D. T. (2006) A two-photon excitation fluorescence cross-correlation assay for a model ligand-receptor binding system using quantum dots. Biophys. J., 90, 1396-1410. 

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