Nanoparticles quantum-size effect

Zhou, H.S., Honma, 1., Komiyama, H. and Haus, J.W. (1994) Controlled synthesis and quantum-size effect in gold-coated nanoparticles. Physical Review B - Condensed Matter, 50, 12052-12057. 

Semiconductor nanoparticles have been intensively studied because of their properties of quantum size effects [54]. A number of synthetic techniques have been reported and their characteristics have been studied by various spectroscopic methods [55, 56]. However, magnetic field effects (MFEs) on the photoelectrochemical properties of semiconductor nanocrystals had not until now been reported. 

Bimetallic nanoparticles (including monometallic ones) have attracted a great interest in scientific research and industrial applications, owing to their unique large sur-face-to-volume ratios and quantum-size effects [1,2,5,182]. Since industrial catalysts usually work on the surface of metals, the metal nanoparticles, which possess much larger surface area per unit volume or weight of metal than the bulk metal, have been considered as promising materials for catalysis. 

The rapid development of nanotechnology has revolutionized scientific developments in recent decades [1]. The synthesis, characterization, and application of functionalized nanoparticles are currently a very active field of research [2], Due to the size limitation of metal nanoparticles, they show very unique properties, which are called nano-size effect or quantum-size effect , which is different from those of both bulk metals and metal atoms. Such specific properties are usually dominated by the atoms located on the surface. In nanoparticles systems, the number of atoms located on the surface of the particles increases tremendously with decreasing of the particle diameter [3]. 

Lemire C, Meyer R, Shaikhutdinov S, Freund HJ. 2004. Do quantum size effects control CO adsorption on gold nanoparticles Angew Chem Int Ed 43 118-121. 

Boeva, V.I., Solovievb, A., Silva, C.J.R., and Gomes, M.J.M. (2005) Incorporation of CdS nanoparticles from colloidal solution into optically clear ureasilicate matrix with preservation of quantum size effect. Solid State Sci. 8(1), 50-58. 

Here, n is the exciton effective mass parallel to the c axis and Lz is the (average) thickness of the WS2 nested structure (Lz=nx 0.6.2 nm, where n is the number of WS2 layers) in the nanoparticle. In a previous study of ultrathin films of 2H-WSe2, AEg of the A exciton was found to obey Eq. (1) over a limited thickness range. The parameter AEg exhibited a linear dependence on 1/Z for Lz in the range of 4-7 nm and became asymptotically constant for Lz> 8 nm (91). A similar trend is observed for IF-WS2 and MoS2, as shown in Fig. 23 (90). Therefore, the quantum size effect... 

Wang Y, Herron N (1991) Nanometer-sized semiconductor clusters material synthesis, quantum size effects, and photophysical properties. J Phys Chem 95 525-532 Ward MH, Cantor KP, Riley D, Merkle S, Lynch CF (2003) Nitrate in public water supplies and risk of bladder cancer. Epidemiology 14 183-190 Ward MH, Mark SD, Cantor KP, Weisenburger DD, Correa-VUlasenore A, Zahm SH (1996) Drinking water and the risk of non-Hodgkin s lymphoma. Epidemiology 7 465 71 Warheit DB (2004) Nanoparticles health impacts Mater Today 7 32-35... 

Nanoparticles, which often show enhanced catalytic abilities [32, 33] unusual optical properties [34], and novel quantum size effects [35], have been widely used in fields such as catalysis [36, 37], sensing [38], optoelectronics [39], and microelectronics [40]. Nanoparticle catalysis is industrially and experimentally important because a large variety of C-C coupling [41] and alcohol oxidation [32] can be effectively catalyzed by nanoparticles. In this part, we will present a brief review on recent advances in supported nanoparticle heterogeneous catalysts on various mesoporous materials. Heterogeneous nanoparticle catalysts have several... 

Synthesis ofPt and Au Nanoparticle Arrays in Mesoporous Silica Films and their Electric/Magnetic Properties in Terms of the Quantum-Size Effect... 

Monticone S, Tufeu R, Kanaev AV, Scolan E, Sanchez C (2000) Quantum size effect in Xi02 nanoparticles does it exist Appl Surf Sci 162-163 565-570... 

Instead, optical measurement was applied to clarify the formation mechanism of Agl nanoparticles in diluted suspensions. Figure 4.4.10A shows the absorption spectra of the 1-day aged suspension containing 3.33 X 10-4 M Ag+ and 6.67 X 10-4 M I- as a function of RSH concentration. When the content of RSH increased from 0 to 6.67 X I0-3 M (curves a-d), the absorption spectra of Agl particles blue-shifted, suggesting the quantum size effect. The relationship between the particle diameter, d (A), and the concentration of RSH, c (A/), was plotted in the inset, which shows the double-logarithmic linear line of d versus c. The aggregation number is found to be proportional to the cube of the size. The same relationship was reported on the formation of CdS nanoparticles (37). These correlations indicate that Agl and CdS have the same ionic nature and have the same reaction modules of thiols. 

A general feature of doped semiconductive NC materials is described in a review paper authored by Bhargava, one of the founders of this area (8). It is generally accepted that solid particles are richer in crystallographical defects when their diameter becomes smaller. Quantum size effects associated with nanoparticles are very sensitive to the defects. In most cases, defects influence negatively the luminescent properties of phosphors. Most of these drawbacks of NC phosphors are attributed to the larger specific surface area, since defects tend to concentrate themselves in a near-surface region. 

Ultimately an understanding of electron transfer processes in dye-sensitized solar cells must be expressed in terms of a model which takes the specific nature of metal oxide surfaces into account [97]. Moreover, the nanostructured devices often involve oxide nanoparticles which approach the limit where quantum-size effects become important. It would be a great step forward if this could be incorporated into an electron-transfer model. 

Generally, quantum size effects are not expected in lanthanide-doped nanoinsulators such as oxides since the Bohr radius of the exciton in insulating oxides, like Y2O3 and Gd2C>3, is very small. By contrast, the exciton Bohr radius of semiconductors is larger (e.g., 2.5 nm for CdS) resulting in pronounced quantum confinement effects for nanoparticles of about 2.5 nm or smaller (Bol et al., 2002). Therefore, a possible influence of quantum size effects on the luminescence properties of lanthanide ions is expected in semiconductor nanocrystals. 

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