M. Stamenova and S. Sanvito
This article reviews recent advances towards the development of a truly atomistic time-dependent theory for spin-dynamics. The focus is on the s-d tight-binding model [where conduction electrons (s) are exchange-coupled to a number of classical spins (d)], including electrostatic corrections at the Hartree level, as the underlying electronic structure theory. In particular, the article considers one-dimensional (1D) magnetic atomic wires and their electronic structure, described by means of the s-d model. The discussion begins with an overview of the model spin Hamiltonian, followed by molecular-dynamics simulations of spin-wave dispersion in a s-d monoatomic chain and spin impurities in a non-magnetic chain. The current-induced motion in a magnetic domain wall (DW) is also explored, along with how an electric current can affect the magnetization landscape of a magnetic nano-object. The article concludes with an assessment of spin-motive force, and especially whether a driven magnetization dynamics can generate an electrical signal.
A. Burke, D. Carroll, Frank Torti, and S.V. Torti
This article examines the potential of bifunctional nanomaterials for the imaging and treatment of cancer. Several nanomaterials possess properties desirable for a cancer therapy and have been the subject of research as anticancer agents. Those that have received the most attention include encapsulated iron oxides, single- and multiwalled carbon nanotubes, gold nanorods and gold nanoshells. This article first considers thermal ablative therapy incancer, focusing on the mechanisms of thermotoxicity and thermoresistance before discussing a number of nanomaterials with applications for cancer treatment. In particular, it evaluates the use of nanomaterials in thermal therapy. It also looks at gold nanoshells and nanorods, taking into account their physical properties, and concludes with an assessment of iron-oxide nanoparticles and future directions for nanomaterials as multifunctional agents for cancer therapy.
P. Zrazhevskiy and X. Gao
This article discusses the use of bioconjugated quantum dots (QDs) for tumor molecular imaging and profiling. The need for personalized diagnostics and therapy is becoming apparent in all areas of medicine, and especially urgent and sought after in treating cancer. Mechanisms of cancerogenesis and cancer response to therapy remain poorly understood, thus precluding accurate cancer diagnosis, prognosis, and effective treatment. Accurate molecular profiling of individual tumors is one key to effective treatment. This article first considers the photophysical properties of QDs before reviewing the most common methods for engineering QD-based probes for biomedical applications, including water solubilization and bioconjugation approaches. It also describes a number of techniques for molecular imagingand profiling of tumors, ranging from QD-based multicolor flow cytometry and applications of QDs in high-resolution correlated fluorescence/electron microscopy, QD bioprobes for molecular profiling of tumor-tissue sections and microarrays, and QD-oligonucleotide bioconjugates for in-situ hybridization.
Carbon-nanotube field emission electron and X-ray technology for medical research and clinical applications
Sigen Wang, Otto Zhou, and Sha Chang
This article describes carbon-nanotube based X-ray technologies for medical research and clinical applications, including an X-ray source, microfocus X-ray tube, microcomputed tomography scanner, stationary digital breast tomosynthesis, microradiotherapy system, and single-cell irradiation system. It first examines electron field emission from carbon nanotubes before discussing carbon-nanotube field emission electron and X-ray technologies in greater detail. It highlights the enormous promise of these systems in commercial and research application for the future in diagnostic medical imaging; in-vivo imaging of small-animal modelsfor pre-clinical cancer studies; security screening; industrial inspection; cancer radiotherapy of small-animal models for pre-clinical cancer studies; and basic cancer research using single-cell irradiation.
K.S. Thygesen and A. Rubio
This article focuses on correlated electron transport in molecular junctions. More specifically, it considers how electronic correlation effects can be included in transport calculations using many-body perturbation theory within the Keldysh non-equilibrium Green’s function formalism. The article uses the GW self-energy method (G denotes the Green’s function and W is the screened interaction) which has been successfully applied to describe quasi-particle excitations in periodic solids. It begins by formulating the quantum-transport problem and introducing the non-equilibrium Green’s function formalism. It then derives an expression for the current within the NEGF formalism that holds for interactions in the central region. It also combines the GW scheme with a Wannier function basis set to study electron transport through two prototypical junctions: a benzene molecule coupled to featureless leads and a hydrogen molecule between two semi-infinite platinum chains. The results are analyzed using a generic two-level model of a molecular junction.
This article examines many novel effects related to the magnetic, electric, elastic and transport properties of Josephson nanocontacts and nanogranular superconductors using a realistic model of two-dimensional Josephson junction arrays. The arrays were created by a 2D network of twin-boundary dislocations with strain fields acting as an insulating barrier between hole-rich domains in underdoped crystals. The article first describes a model of nanoscopic Josephson junction arrays before discussing some interesting phenomena, including chemomagnetism and magnetoelectricity, electric analog of the ‘fishtail‘ anomaly and field-tuned weakening of the chemically induced Coulomb blockade, a giant enhancement of the non-linear thermal conductivity in 2D arrays, and thermal expansion of a singleJosephson contact.
Philip G. Collins
This article examines the physical consequences of defects and disorder in carbon nanotubes (CNTs). It begins with a pedagogical categorization of the types of defects and disorder found in CNTs, including lattice vacancies and bond rotations, and goes on to discuss considers two primary sources of disorder: the environment surrounding a CNT and the substrate supporting it. It then considers various experimental methods for locating defects in CNTs, including atomic-resolution scanning tunnelling microscopy, transmission electron microscopy, electrochemical and chemoselective labelling, optical spectroscopy, and electrical conductance. The article concludes with a review of the long-range consequences of defects and disorder on the physical properties of CNTs such as chemical reactivity, electrical transport, and mechanical effects.
Nian Lin and Sebastian Stepanow
This article describes the use of supramolecular chemistry to design low-dimensional nanostructures at surfaces. In particular, it discusses the design strategies of two types of low-dimensional supramolecular nanostructures: structures stabilized by hydrogen bonds and structures stabilized by metal-ligand co-ordination interactions. After providing an overview of hydrogen-bond systems such as 0D discrete clusters, 1D chains, and 2D open networks and close-packed arrays, the article considers metal-co-ordination systems. It also presents experimental results showing that both hydrogen bonds and metal co-ordination offer protocols to achieve unique nanostructured systems on 2D surfaces or interfaces. Noting that the conventional 3D supramolecular self-assembly has generated a vast number of nanostructures revealing high complexity and functionality, the article suggests that 2D approaches can be applied to substrates with different symmetries as well as physical and chemical properties.
Sven Stafström and Mikael Unge
This article examines disorder-induced electron localization in molecular-based materials, using DNA and pentacene molecular crystals as examples. In DNA, the disorder is intrinsic and strong, resulting in very short localization lengths. The pentacene crystal, on the other hand, is intrinsically homogeneous and the disorder is extrinsic and weak, which makes a metal–insulator transition (MIT) possible. After providing an overview of carbon-based materials for electronic applications, the article explains the methodology for calculating the localization properties of a DNA double strand and a pentacene molecular crystal, namely Hamiltonian, transfer matrix, and finite-size scaling. It also discusses the results, which show a substantial increase in the localization length of the electronic state with correlated disorder as compared to the case of uncorrelated disorder.
Joshua D. Carter, Chenxiang Lin, Yan Liu, Hao Yan, and Thomas H. LaBean
This article examines the DNA-based self-assembly of nanostructures. It first reviews the development of DNA self-assembly and DNA-directed assembly, focusing on the main strategies and building blocks available in the modern molecular construction toolbox, including the design, construction, and analysis of nanostructures composed entirely of synthetic DNA, as well as origami nanostructures formed from a mixture of synthetic and biological DNA. In particular, it considers the stepwise covalent synthesis of DNA nanomaterials, unmediated assembly of DNA nanomaterials, hierarchical assembly, nucleated assembly, and algorithmic assembly. It then discusses DNA-directed assembly of heteromaterials such as proteins and peptides, gold nanoparticles, and multicomponent nanostructures. It also describes the use of complementary DNA cohesion as 'smart glue' for bringing together covalently linked functional groups, biomolecules, and nanomaterials. Finally, it evaluates the potential future of DNA-based self-assembly for nanoscale manufacturing for applications in medicine, electronics, photonics, and materials science.