Semiconductor nanoclusters

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). 

N,N-bis(4-methylphenyl)-N,iV-bis(4-ethylphenyl)-[l,l -(3,3 -dimethyl)biphenyl]-4,4 -diamine [115310-63-9] (ETPD) (8) -doped PMPS (Table 1, entry 22), hole mobihty approaching 10 cm /Vs at 2.5 x 10 V/cm was observed (48). This is the highest recorded hole mobihty for disordered organic systems. From this perceptive, it is very interesting to study the carrier mobihty of polymers heavily doped with semiconductor nanoclusters. 

Volume 103 Semiconductor Nanoclusters - Physical, Chemical, and Catalytic Aspects edited by P.V. Kamat and D. Meisel... 

Sant PA, Kamat PV (2002) Interparticle electron transfer between size-quantized CdS and T102 semiconductor nanoclusters. Phys Chem Chem Phys 4 198-203... 

Semiconductor nanoclusters trapped in AOT w/o microemulsions are reported to exhibit longer excited state lifetimes (about 10-100 ns) than those in aqueous solution or in monophasic organic solvents [213]. Clearly the surfactant-nanoparticle interaction is very important not only in restricting growth but also in extending the hfetimes of the excited states. Tata et al. [214] have shown that the removal of water from the micelles leads to a strong increase in fluorescence intensity, and the addition of specific quencher, 4-hydroxythiophenol, leads to variations in quenching efficiencies. 

Theoretical chemistry at York University was strengthened in the 1990s with the appointments of Bill Pietro in 1991 and Rene Fournier in 1996. Pietro wrote part of the Gaussian code as a graduate student and several modules of SPARTAN while an assistant professor at the University of Wisconsin. While he was in Madison he developed a research program based on molecular electronic devices.236 He expanded his interests to several facets of molecular electronics, including molecular electroluminescent materials, molecular electronic devices (diodes, switches, and sensors), and functionalized semiconductor nanoclusters.237 These new materials not only are scientifically very exciting, but they offer the possibility of revolutionary impact on the future of the electronics industry. 

H. Noglik and W. J. Pietro, Chem. Mater., 7, 1333 (1995). Surface Functionalization of Cadmium Sulfide Quantum Confined Semiconductor Nanoclusters. 2. Formation of a Quantum Dot Condensation Polymer. 

Kamat, Prashant V., Native and Surface Modified Semiconductor Nanoclusters. 44 273... 

Figure 1 Photoinduced charge transfer processes in semiconductor nanoclusters, (a) Under bandgap excitation and (b) sensitized charge injection by exciting adsorbed sensitizer (S). CB and VB refer to conduction and valence bands of the semiconductor and et and ht refer to trapped electrons and holes, respectively.

Figure 5 Excited state processes of a dye molecule adsorbed on a semiconductor nanocluster.

The thin semiconductor particulate film prepared by immobilizing semiconductor nanoclusters on a conducting glass surface acts as a photosensitive electrode in an electrochemical cell. An externally applied anodic bias not only improves the efficiency of charge separation by driving the photogenerated electrons via the external circuit to the counter electrode compartment but also provides a means to carry out selective oxidation and reduction in two separate compartments. This technique has been shown to be veiy effective for the degradation of 4-chlorophenol [116,117], formic acid [149], and surfactants [150] and textile azo dyes [264,265]. 

The feasibility of synthesizing composite semiconductor nanoclusters by chemical precipitation or electrochemical deposition opens up a wide array of possi-... 

Composite semiconductor nanoclusters can be classified into two categories, namely, capped- and coupled-type heterostructures. The capped nanoclusters essentially have a core-shell geometry while in a coupled system two semiconductor nanoclusters are in contact with each other. The principle of charge separation in capped and coupled semiconductor systems is illustrated in Fig. 12. 

An interesting aspect of composite semiconductor nanoclusters is their ability to rectify the charge carrier flow following the bandgap excitation of the... 

Kamat, P. V. Native and surface modified semiconductor nanoclusters. In Molecular Level Artificial Photosynthetic Materials. Progress in Inorganic Chemistry Series, vol. 44, J. Meyer, ed., Wiley New York, 1997, p. 273. 

Kamat PV. Composite Semiconductor Nanoclusters. Studies in surface science and catalysis. Amsterdam Elsevier, 1996. 

Semiconductor nanoclusters (quantum dots) possess chemical and physical properties that differ substantially from those of the analogous bulk solids [36-38]. Quantum dots have been synthesized using hosts such as zeolites [39], porous glass [40], micelles [41], membranes [42], and anionic polymers [43]. The synthesis and characterization of CdS quantum dots in dendrimer hosts have been studied [44-48]. Here, two PAMAM dendrimers are used one is G3.5 with surface carboxyl group and the other is G4 with surface amino group. Mixing solutions of Cd2+ and S2 in pure methanol result in a yellow precipitate of... 

Kamat, P.V. (1997). Native and surface modified semiconductor nanoclusters. Molecular Level Artificial Photo synthetic Materials, 44, 273-343. 

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