Nanoparticles semiconductor

During the past two decades, the synthesis or preparation of II-VI semiconductor nanopartides has experienced an enormous development, to the point where the pubhshed material related to the topic has become virtually unmanageable. Nevertheless, the aim of this chapter is to provide a chronological overview of some of the major historical lines in this area, starting with the earliest studies with CdS nanocrystals prepared in aqueous solution. At several points in the story - mostly when successful preparations are first described - the chapter branches into evolving sub-fields, leading to Sections 3.2.1.2 and 3.2.I.3. The remainder of the review then relates to matters distinct from these preparational approaches. More complicated nanoheterostructures, in which two compounds are involved in the build-up of spherically layered particles, are detailed in Sections 3.2.1.4 and 3.2.1.5. 

Naturally, in all chapters, the view of the author is indicated with regards to the importance of the studies under review for the evolution of the subject as a whole. Besides this necessarily subjective viewpoint, it is not impossible that other important work might have been overlooked. Thus, even if a particular chapter provides little more than a list of references, questions such as What has been done in this field may be answered, but never those such as What has not been done yet  

Henglein s CdS nanoparticles were prepared from Cd(C104)2 and Na2S on the surface of commercial silica particles. The absorption onset is shifted considerably to 

This series spanned a range of sizes, from more or less molecular species to fragments of the bulk lattice containing tens of thousands of atoms. The remarkable quality of these particles can be seen clearly in several features of the absorption spectra, such as the steepness of the absorption onset, the narrow absorption bands, and the occurrence of higher energy transitions. Subsequently, major progress was made in the preparation of such systems within about a decade of these initial findings. 

As determined using pulse radiolysis experiments, an excess electron on the surface of CdS colloids causes a bleaching of the optical absorption at wavelengths close to the onset of absorption [27]. A year later, the results of a study were reported (originally from the Henglein group, but frequently cited since then [28]) which referred to CdS sols with particle sizes ranging from 4 to 6 nm (as measured via 

Once the crystal comprises a few tens of atoms, there is an identifiable core, in which the local bonding geometry closely resembles that of bulk solids. As mentioned in the precedent section, nanoparticles constitute the bridge between the atomic-molecular and the extended crystalline limits. In simple metals, the Fermi level, EF, lies in the center of a band. The relevant energy spacing is still very small and above a few K, the electrical and 

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Metallic and semiconductor nanoparticles or nanocrystals —chunks of matter intennediate in size and physical properties between single atoms and tire macroscopic bulk materials—are of great interest botli for tlieir... 

Behboudnia, M. and Azizianekalandaragh, Y. (2007). Synthesis and characterization of CdSe semiconductor nanoparticles by ultrasonic irradiation. Mater. Sci. and Eng. B, 138, 65-68. 

Gaunt, J. A. Knight, A. E. Windsor, S. A. and Chechik, V. (2005). Stability and quantum yield effects of small molecules additives on solutions of semiconductor nanoparticles. /. Colloid and Interface Science, 290 (2), 437-443. 

Malik, M. A. Revaprasadu, N. and O Brien, P. (2001). Air-stable single-source precursors for the synthesis of chalcoeenide semiconductor nanoparticles. Chem. Mater., 13, 913-920. 

Generation of nanoparticles under Langmuir monolayers and within LB films arose from earlier efforts to form nanoparticles within reverse micelles, microemulsions, and vesicles [89]. Semiconductor nanoparticles formed in surfactant media have been explored as photocatalytic systems [90]. One motivation for placing nanoparticles within the organic matrix of a LB film is to construct a superlattice of nanoparticles such that the optical properties of the nanoparticles associated with quantum confinement are preserved. If mono-layers of capped nanoparticles are transferred, a nanoparticle superlattice can be con-... 

C. Langmuir-Blodgett Films Containing Semiconductor Nanoparticles... 

Formation of Semiconductor Nanoparticles Underneath Langmuir Monolayers... 

Formation of Semiconductor Nanoparticles Inside Langmuir-Blodgett Films... 

The formation of semiconductor nanoparticles and related stmctures exhibiting quantum confinement within LB films has been pmsued vigorously. In 1986, the use of the metal ions in LB films as reactants for the synthesis of nanoscale phases of materials was described [167]. Silver particles, 1-2 mn in size, were produced by the treatment of silver be-henate LB films with hydrazine vapor. The reaction of LB films of metal salts (Cd, Ag, Cu, Zn, Ni, and Pb ) of behenic acid with H2S was mentioned. The use of HCl, HBr, or HI was noted as a route to metal halide particles. In 1988, nanoparticles of CdS in the Q-state size range (below 5 mn) were prepared inside LB films of cadmium arachi-... 

In an effort to restrict the location of semiconductor nanoparticles in LB films and inhibit aggregation, the formation of CdS in LB films of calixarenes was investigated [195]. Limiting areas of 3.0 nm and 1.8 nm were obtained on 0.5 mM CdCli, compatible with the cross-sectional areas of the calixarenes. Y-type LB fdms were prepared at 25 mN m on glass, quartz, and silicon. The substrates had been made hydrophobic by treatment with a silane vapor. After H2S treatment overnight in sealed jars, UV absorbance spectra and XPS data were obtained. The absorption edge for the CdS particles formed in the calixarene LB films transferred at pH 5.5 was 3.3 eV as compared with 2.7 eV for films formed in cad-... 

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). 

FIG. 42 Schematic of the self-aggregation process for semiconductor nanoparticles. 

Katz E, WiUner 1, Wang J (2004) Electroanalytical and bioelectroanalytical systems based on metal and semiconductor nanoparticles. Electroanalysis 16 19-44 Pardo-Yissar V, Katz E, Wasserman J, Willner 1 (2003) Acetylcholine esterase-labeled CdS nanoparticles on electrodes Photoelectrochemical sensing of the enzyme inhibitors. J Am Chem Soc 125 622-623... 

Curii ML, Agostiano A, Leo G, Mallardi A, Cosma P, Monica MD (2002) Development of a novel enzyme/semiconductor nanoparticles system for biosensor apphcation. Mater Sci Eng C 22 449-452... 

Magnetic field effects on the photoelectrochemical reactions of photosensitive electrodes are very important for practical applications of the MFEs in controlling the photoelectronic functions of molecular devices. Previously, we have examined MFEs on the photoelectrochemical reactions of photosensitive electrodes modified with zinc-tetraphenylporphyrin-viologen linked compounds [27, 28] and semiconductor nanoparticles [29, 30[. However, MEEs on the photoelectrochemical reactions of photosensitive electrodes modified with nanoclusters have not yet been reported. 

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. 

Pant and Levinger have measured the solvation dynamics of water at the surface of semiconductor nanoparticles [48,49]. In this work, nanoparticulate Zr02 was used as a model for the Ti02 used in dye-sensitized solar photochemical cells. Here, the solvation dynamics for H2O and D2O at the nanoparticle surface are as fast or faster than bulk water motion. This is interpreted as evidence for reduced hydrogen bonding at the particle interface. 

Abstract A convenient method to synthesize metal nanoparticles with unique properties is highly desirable for many applications. The sonochemical reduction of metal ions has been found to be useful for synthesizing nanoparticles of desired size range. In addition, bimetallic alloys or particles with core-shell morphology can also be synthesized depending upon the experimental conditions used during the sonochemical preparation process. The photocatalytic efficiency of semiconductor particles can be improved by simultaneous reduction and loading of metal nanoparticles on the surface of semiconductor particles. The current review focuses on the recent developments in the sonochemical synthesis of monometallic and bimetallic metal nanoparticles and metal-loaded semiconductor nanoparticles. 

In this review, the potential uses of sonochemistry for the preparation of monometallic and bimetallic metal nanoparticles and metal-loaded semiconductor nanoparticles have been highlighted. While specific examples available in the literature were discussed, the sonochemical technique seems to offer a platform technique that could be used for synthesizing a variety of functional materials. Most of the studies to date deal with laboratory scale exploration , it would be ideal if the concepts are tested under large scale experimental conditions involving specific applications. The authors sincerely hope that the information provided in this review would prompt such experimental investigation in a new dimension. 

Zhu et al. [94] reported the synthesis of Sn02 semiconductor nanoparticles by ultrasonic irradiation of an aqueous solution of SnCLj and azodicarbonamide under ambient air. They found that the sonochemically synthesized Sn02 nanoparticles improved remarkably the performance of Li ion batteries such that there was about threefold increase (from 300 to 800 mAh/g) in the reversible capacity in the first lithiation to delithiation cycles. Similarly the irreversible capacity also increased by about 70% (from 800 to 1400 mA h/g). Wang et al. [95] reported the synthesis of positively charged tin porphyrin adsorbed onto the surface of silica and used as photochemically active templates to synthesise platinum and palladium shell and... 

Galoppini E (2004) Linkers for anchoring sensitizers to semiconductor nanoparticles. Coor-din Chem Rev 248 1283-1297... 

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