Current research into semiconductor clusters is focused on the properties of quantum dots-fragments of semiconductor consisting of hundreds to many thousands of atoms-with the bulk bonding geometry and with surface states eliminated by enclosure in a material that has a larger band gap. Quantum dots exhibit strongly size-dependent optical and electrical properties. The ability to join the dots into complex assemblies creates many opportunities for scientific discovery.

Semiconductor Clusters, Nanocrystals, and Quantum Dots

This review describes a new paradigm of electronics based on the spin degree of freedom of the electron. Either adding the spin degree of freedom to conventional charge-based electronic devices or using the spin alone has the potential advantages of nonvolatility, increased data processing speed, decreased electric power consumption, and increased integration densities compared with conventional semiconductor devices. To successfully incorporate spins into existing semiconductor technology, one has to resolve technical issues such as efficient injection, transport, control and manipulation, and detection of spin polarization as well as spin-polarized currents. Recent advances in new materials engineering hold the promise of realizing spintronic devices in the near future. We review the current state of the spin-based devices, efforts in new materials fabrication, issues in spin transport, and optical spin manipulation.

http://science.sciencemag.org/content/sci/294/5546/1488.full.pdf

Spintronics: a spin-based electronics vision for the future.

Spintronics, or spin electronics, involves the study of active control and manipulation of spin degrees of freedom in solid-state systems. This article reviews the current status of this subject, including both recent advances and well-established results. The primary focus is on the basic physical principles underlying the generation of carrier spin polarization, spin dynamics, and spin-polarized transport in semiconductors and metals. Spin transport differs from charge transport in that spin is a nonconserved quantity in solids due to spin-orbit and hyperfine coupling. The authors discuss in detail spin decoherence mechanisms in metals and semiconductors. Various theories of spin injection and spin-polarized transport are applied to hybrid structures relevant to spin-based devices and fundamental studies of materials properties. Experimental work is reviewed with the emphasis on projected applications, in which external electric and magnetic fields and illumination by light will be used to control spin and charge dynamics to create new functionalities not feasible or ineffective with conventional electronics.

/pdf/spintronics-fundamentals-and-applications-2dx38n6phu.pdf

Spintronics: Fundamentals and applications

Dye-sensitized solar cells (DSCs) offer the possibilities to design solar cells with a large flexibility in shape, color, and transparency. DSC research groups have been established around the worl ...

/pdf/dye-sensitized-solar-cells-50b0w2bhsr.pdf

Dye-Sensitized Solar Cells

Semiconductor nanocrystals were prepared for use as fluorescent probes in biological staining and diagnostics. Compared with conventional fluorophores, the nanocrystals have a narrow, tunable, symmetric emission spectrum and are photochemically stable. The advantages of the broad, continuous excitation spectrum were demonstrated in a dual-emission, single-excitation labeling experiment on mouse fibroblasts. These nanocrystal probes are thus complementary and in some cases may be superior to existing fluorophores.

https://science.sciencemag.org/content/sci/281/5385/2013.full.pdf

Semiconductor Nanocrystals as Fluorescent Biological Labels

Inorganic nanoparticles of a variety of materials have been obtained by chemical methods. Under the kinetic control, small variations in the synthesis recipe may yield crystals of different sizes, shapes and structures. Co nanocrystals are of particular interest: besides achieving size control, at least three nearly isoenergetic crystal structures (face-centered cubic, hexagonal close-packed and epsilon) can be synthesized, and shape control (spheres, prisms, cubes, rods and disks) is also possible. Although shape and structure should be intrinsically related, the relationship between these two characteristics has not been deeply explored up to this moment. Here, we present our latest results on Co nanoparticles, analyzing the influence of some parameters on particle shape and structure. In particular, the influence of ligand type and temperature has been tackled.

Surfactant and temperature influence on Co nanocrystal structure and shape

Correspondence should be addressed to W. J. Parak, Wolfgang.parak@physik.uni-marburg.deReceived 20 July 2007; Accepted 13 December 2007Recommended by Marek OsinskiGold-DNA conjugates were investigated in detail by a comprehensive gel electrophoresis study based on 1200 gels. A controllednumber of single-stranded DNA of diﬀerent length was attached speciﬁcally via thiol-Au bonds to phosphine-stabilized colloidalgold nanoparticles. Alternatively, the surface of the gold particles was saturated with single stranded DNA of diﬀerent length eitherspeciﬁcally via thiol-Au bonds or by nonspeciﬁc adsorption. From the experimentally determined electrophoretic mobilities, esti-mates for the eﬀective diameters of the gold-DNA conjugates were derived by applying two diﬀerent data treatment approaches.The ﬁrst method is based on making a calibration curve for the relation between eﬀective diameters and mobilities with goldnanoparticles of known diameter. The second method is based on Ferguson analysis which uses gold nanoparticles of known di-ameter as reference database. Our study shows that eﬀective diameters derived from gel electrophoresis measurements are aﬀectedwith a high error bar as the determined values strongly depend on the method of evaluation, though relative changes in size uponbinding of molecules can be detected with high precision. Furthermore, in this study, the speciﬁc attachment of DNA via gold-thiolbonds to Au nanoparticles is compared to nonspeciﬁc adsorption of DNA. Also, the maximum number of DNA molecules thatcan be bound per particle was determined.Copyright © 2007 T. Pellegrino et al. This is an open access article distributed under the Creative Commons Attribution License,which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

/pdf/researcharticle-gel-electrophoresis-of-gold-dna-1t79ag2xil.pdf

A. P. Alivisatos

Papers

Surfactant and temperature influence on Co nanocrystal structure and shape

ResearchArticle Gel Electrophoresis of Gold-DNA Nanoconjugates