A novel multifunctional and biocompatible ultrananocrystalline diamond (UNCD) film technology developed recently represents a new material with a unique combination of functionalities, including biocompatibility, to enable a new generation of implantable medical devices and scaffolds for tissue engineering. Following a description of the synthesis and properties of UNCD films and a comparison with other diamond film technologies, this article focuses on descriptions of key UNCD-based medical devices to treat specific medical conditions requiring effective therapies: (1) A UNCD-coated microchip (artificial retina) implantable inside the eye on the retina to restore partial vision to people blinded by retinitis pigmentosa and macular degeneration produced by genetically induced degeneration of the retina photoreceptors. (2) A UNCD-coated intraocular device for treatment of glaucoma in the eye. (3) UNCD-coated metal dental implants with potential order of magnitude longer life and superior performance than current implants.

The effects of a magnetic field on the current in sandwich devices of a nonmagnetic material in-between two ferromagnetic electrodes are well known. However, magnetic-field effects also occur in the responses of devices of organic semiconductors sandwiched in-between non-ferromagnetic electrodes, providing an entirely new route toward organic spintronics. The precise origins of these “intrinsic” magnetic field effects are still unclear. They appear to be related to spin-selective reactions between paramagnetic entities such as electrons, holes, and triplet excitons. We present an overview of these effects and discuss three recent developments that shed new light on them: (1) tuning of the effects in molecularly engineered systems, (2) the discovery of ultrahigh magnetoresistance in molecular wires, and (3) the discovery of “fringe-field” magnetoresistance.

Organic materials are fascinating and promising candidates for nanoscale spintronic devices and may open viable routes toward quantum computing. Previous experiments on spin transport in organic devices, through break junctions or spin valves, unveiled exciting new frontiers of molecular magnetism. However, much more effort is needed to understand the properties of organic/magnetic interfaces at a microscopic level. In this article, we show how spin-polarized scanning tunneling microscopy and spectroscopy (SP-STM/STS) can provide unprecedented insights into organic/magnetic interfaces as an initial step toward favorably tailoring such interfaces in order to increase device efficiency. Based on the unique combination of spin-sensitivity, atomic-scale spatial resolution, and high-energy resolution, SP-STM/STS has proven to be an invaluable method for exploring spatial and bias dependences of spin-polarized currents through individual molecules as well as for revealing individual spin-split molecular orbitals interacting with ferromagnetic substrates.

We review the first 10 years of research on organic spin-valve devices in the field of organic spintronics. The device figure of merit, magnetoresistance, is governed by the hyperfine interaction of the organic interlayer and the ability of the ferromagnetic electrodes to inject spin-polarized carriers. By choosing a deuterated π-conjugated polymer with a relatively long spin diffusion length as the organic interlayer and using a thin LiF buffer layer to raise the Fermi level of the cathode, a bipolar spin-valve device could be obtained in which the electroluminescence emission intensity is controlled by an external magnetic field. We show that the underlying physics of this spin-organic light-emitting diode is very different from that of a unipolar organic spin valve because of the magnetic properties of the spin-polarized bipolar space charge limited current in the device.

The thermoelectric properties of Bi2Sr2Co2Ox (BSC-222) bulk materials prepared by three different processing methods, i.e., conventional sintering, hot pressing, or partial melting, were investigated and compared. The electrical current, temperature difference for Seebeck coefficient, and thermal diffusion were measured in the same direction. The hot pressing and partial melting are effective processing methods for improving the electrical transport property in BSC-222 bulk materials due to an improvement of density in hot-pressed samples or by grain growth during partial melting process. For partially melted samples, a decrease in the thermal conductivity is also observed. The highest dimensionless thermoelectric figure of merit (ZT) values have been obtained in the sample prepared by partial melting method, for which ZT has been increased by a factor of 2.7 by comparison with bulk materials prepared by conventional sintering. At 700 °C in air, ZT value reaches 0.27 for partially melted Bi2Sr2Co2Ox bulk materials. This study shows that optimized electrical and thermal transport properties can be achieved in BSC-222 bulk materials possessing microstructures with both large average grain size and appropriate bulk density.

The solid-state phase transitions of bismuth(III) oxide (Bi2O3) nanoparticles were investigated by complementary methods such as differential scanning calorimetry, differential thermal analysis with combined thermogravimetry and mass spectrometry, and high-temperature x-ray diffraction as compacted nanopowder. At room temperature the particles resided in the β-phase, which is usually a metastable high-temperature phase of bulk Bi2O3. The complementary experimental methods were linked and a nanophase (tetragonal β-phase) → bulk-phase (monoclinic α-phase) transition was identified which was preceded by crystal growth and evaporation of O and C containing species. It was also shown that the atmosphere (more precisely its absolute pressure) has an influence on the transition behavior. An interpretation was proposed that successfully explains all observations from this work and from literature: A sudden destabilization takes place around 735 K due to the loss of the stabilizing, carbonized surface. This leads to the observed transformation to the bulk-phase. But if the particles are smaller than a certain, critical size in the nanorange and are not allowed to grow, they remain in the nanophase until they melt.

In this study, thermodynamic properties of BC2N under extreme conditions have been reported by using first-principle calculations and quasi-harmonic Debye model. Isochoric heat capacity (Cv) of BC2N at normal temperature and pressure is 23.15 kJ mol−1 K−1 and it increases with the temperature and decreases with the pressure. In the low temperature region, pressure has no obvious influence on phonons and thus the decrease of Cv is very slow. In the medium temperature region, the decrease of Cv becomes steep. The reason is that high pressure plays an important role in controlling the vibration of atoms. In the high temperature region, the decrease of Cv becomes slow. Debye temperature (θ) decreases with the temperature. However, the tendency is not obvious in the low temperature region but very clear in high temperature. Moreover, θ increases with pressure and the amplitude is larger in higher temperature. Because of the four covalent bonds with different strength and distribution asymmetric thermal expansion along different axes occurs. The value of thermal expansion coefficient along c axis is more than that of along a and b axes.

In this work, mechanical stability, thermodynamic and elastic properties of rhodium (Rh), rhodium monohydride (RhH), and the newly discovered rhodium dihydride (RhH2) under high temperature and pressure are studied by ab initio method together with quasiharmonic Debye model. Mechanical stability test indicates that RhH2 is no longer mechanically stable when pressure is higher than 22.7 GPa, which is quite less than the dynamically stable pressure (90 GPa). The heat capacity at constant volume (Cv) of Rh, RhH, or RhH2 increases proportional to T3 at low temperature, and tends to Dulong–Petit limit (about 241.67, 478.47, and 706.15 J/(kg·K), respectively). The thermal expansion coefficient (α) of Rh, RhH, and RhH2 increases acutely when temperature is not more than 300 K. And then, the increase of α slows down. The α reduces with pressure transiently. H atom's entering in fcc-Rh lattice would greatly change the electron density distribution, which would cause obvious difference in thermodynamic and elastic properties between Rh, RhH, and RhH2.