This article provides an overview of the key concepts and recent theoretical developments in computational modeling of complex metal hydrides with a focus on applications in hydrogen storage. Density functional theory based first-principles calculations have played an important role in understanding the structural and thermodynamic properties of these materials. Methods for predicting crystal structures and hydrogen positions in complex hydrides have been developed to complement experimental synthesis and characterization. Together with an efficient formalism for determining multinary phase diagrams under variable temperature and hydrogen pressure (the grand-canonical linear programming method), they constitute a complete first-principles framework for designing new hydrogen storage reactions. We also review the progress in modeling reaction kinetics in a prototypical complex hydride (i.e., a transition metal catalyzed sodium alanate [NaAlH4]). While many aspects of titanium-doped NaAlH4 remain hotly disputed, we discuss areas where satisfactory quantitative understanding has been achieved: diffusive metal mass transport, bulk substitution of Ti, and hydrogen dissociation.

Organic single crystals are an established part of the emerging field of organic optoelectronics, because they provide an ideal platform for the studies of the intrinsic physical properties of organic semiconductors. As organic crystals have low melting temperatures and high vapor pressures and are soluble in numerous organic solvents, both solution and gas-phase methods can be used for crystal growth. The nature of the individual molecules and the interactions between molecules determine which growth method is preferred for particular materials. Organic semiconductors with very low decomposition or melting temperatures can be grown from solutions, whereas semiconductors with high vapor pressures can be grown using physical vapor transport methods. High-quality crystals can be obtained using both methods. Crystal growth and crystal engineering of multicomponent organic compounds are emerging fields that can provide a variety of new materials with different physical properties. The growth of large crystals from the melt by zone melting, the Bridgman, or the Czochralski methods has been used to produce stable materials used in wafer manufacturing or large scintillator detectors. In this article, single-crystal growth methods for organic semiconductors are discussed with the aim of preparing high-quality specimens for determination of the basic properties of organic semiconductors.

Ionic liquids (ILs) are a very interesting new class of fluid materials because of their unique characteristics, such as wide chemical, thermal, and electrochemical stability, high ion conduction, non-detectable vapor pressure, nonflammability, and good-to-excellent capability to dissolve inorganic, organic, and polymer compounds. ILs are proposed for a very wide variety of applications, including electrochemical devices. However, high purity ILs, particularly for high-energy electrochemical applications, are not widely available commercially. In addition, solvent restriction and environmental impact, as well as the possibility to fully recycle chemicals and reagents, represent the most stringent requirements for the future synthesis processes of ILs. This article reviews synthesis route improvements in terms of environment impact solvents, chemical recycling and cost, and process yield for obtaining high purity (below 50 ppm) ILs.

Microfluidic paper-based analytical devices (μPADs) use the passive capillary-driven flow of aqueous solutions through patterned paper channels to transport a sample fluid into distinct detection zones that contain the reagents for a chemical assay. These devices are simple, affordable, portable, and disposable; they are, thus, well suited for diagnostic applications in resource-limited environments. Adding screen-printed electrodes to the detection zones of a μPAD yields a device capable of performing electrochemical assays (an EμPAD). Electrochemical detection has the advantage over colorimetric detection that it is not affected by interference from the color of the sample and can be quantified with simple electronics. The accessibility of EμPADs, however, is limited by the requirement for an external potentiostat to power and interpret the electrochemical measurement. New developments in paper-based electronics may help loosen this requirement. This review discusses the current capabilities and limitations of EμPADs and paper-based electronics, and sketches the ways in which these technologies can be combined to provide new devices for diagnostic testing.

Novel electronic and magnetic phases are being observed at interfaces between insulating, non-magnetic oxide compounds, with the most notable example being the interface between SrTiO3 and LaAlO3. The basic properties of these interfaces will be discussed, as well as prospects for applications and possible future developments.

Surface-enhanced Raman spectroscopy (SERS) is highly dependent upon the substrate, where excitation of the localized metal surface plasmon resonance enhances the vibrational scattering signal of proximate analyte molecules. This article reviews recent progress in the fabrication of SERS substrates and the requirements for characterization of plasmonic materials as SERS platforms. We discuss bottom-up fabrication of SERS substrates and illustrate the advantages of rational control of metallic nanoparticle synthesis and assembly for hot spot creation. We also detail top-down methods, including nanosphere lithography for the preparation of tunable, highly sensitive, and robust substrates, as well as the unique benefits of tip-enhanced Raman spectroscopy for simultaneous acquisition of molecular vibrational information and high spatial resolution imaging. Finally, we discuss future prospects and challenges in SERS, including the development of surface-enhanced femtosecond stimulated Raman spectroscopy, microfluidics with SERS, creating highly reproducible substrates, and the need for reliable characterization of substrates.

The exotic features of quantum mechanics have the potential to revolutionize information technologies. Using superposition and entanglement, a quantum processor could efficiently tackle problems inaccessible to current-day computers. Nonlocal correlations may be exploited for intrinsically secure communication across the globe. Finding and controlling a physical system suitable for fulfilling these promises is one of the greatest challenges of our time. The nitrogen-vacancy (NV) center in diamond has recently emerged as one of the leading candidates for such quantum information technologies thanks to its combination of atom-like properties and solid-state host environment. We review the remarkable progress made in the past years in controlling electrons, atomic nuclei, and light at the single-quantum level in diamond. We also discuss prospects and challenges for the use of NV centers in future quantum technologies.

A quantum information processor must perform accurate manipulations of many quantum degrees of freedom without introducing strong interactions with the environment that lead to the loss of quantum coherence. Spins in semiconductors have been shown to have long coherence times, so semiconducting quantum processors are feasible if the necessary manipulations can be performed without introducing excessive spin decoherence. To perform the necessary manipulations of single spins and to control the couplings between different spins, fine control of electronic energy levels and wave function overlaps is required. Electrically gated quantum dots have the promise of enabling such control, because the same gates that are used to define the quantum dot can be used to perform the necessary manipulations. This article describes recent progress toward the development of high-fidelity qubits using top-gate defined semiconductor quantum dots.

Using computational modeling, we describe and explain the effects resulting from surfaces and interfaces in core–shell nanoparticles. We outline the basis of the atomistic spin model, which is used to simulate the equilibrium and dynamic magnetic properties of magnetic nanoparticles. The physical origin of magnetic surface anisotropy is described, along with its effect on the magnetic spin configuration and energy landscape. Importantly, it is shown that a cubic anisotropic surface can be induced, which leads to a complex energy landscape with a non-trivial size dependence. Additional microstructural effects in realistic nanoparticle microstructures are investigated, and fundamental magnetic properties can be significantly altered as a result. Finally, an important effect known as exchange bias is also described. Exchange bias causes an enhancement of the thermal stability of magnetic nanoparticles, but due to its atomic origin, it also leads to complicated physical behavior.

Bioinspired surfaces with special wettability have rapidly emerged at the forefront of materials research. What is behind biological surfaces with special wettability, and how can we realize special wettability properties for artificial materials? This article describes how the interplay between unique multiscale (micro- and nanoscale) structures of biological surfaces and intrinsic material properties plays a crucial role in achieving the desired wettability and functionalities. Taking inspiration from natural surfaces, researchers have designed and created novel interfacial materials with versatile special wettability, such as superantiwetting surfaces (superhydrophobic and superoleophobic), smart switchable surfaces, and water collecting surfaces.

Emissive saturated colors are key components of new generations of lighting and display technologies. Quantum dots have evolved in the past two decades to fulfill many of the requirements of color purity, stability, and efficiency that are critical to transitioning these materials from the laboratory into these markets. A fundamental feature of quantum dots is the tunability of their emission color through precise control of their size and composition, giving access to UV, visible, and near-infrared wavelengths. Continuing improvements in engineering core–shell quantum dot structures, where a 1–10 nm binary, ternary, or alloyed semiconductor core particle is surrounded by a shell composed of one or more semiconductors of a wider bandgap, have resulted in materials with fluorescence quantum yields that approach unity, narrow symmetric spectral line shapes, and remarkable stabilities. In this article, we review progress in the development of highly luminescent core–shell quantum dots of different semiconductor families in view of their integration in light-emitting applications. CdSe-based quantum dots already fulfill many of the requirements of lighting and display applications in terms of fluorescence quantum yield, color purity, and stability.

The nitrogen-vacancy (NV) center in diamond offers the opportunity to develop quantum technologies that leverage the defect’s atom-like properties using established engineering techniques from the semiconductor industry. While many NV center applications are motivated by the remarkable properties of isolated NV centers in bulk diamond, realizing these technologies requires addressing a number of device and materials engineering challenges unique to creating and controlling individual semiconductor spins. We review recent advances in interfacing NV centers with on-chip electronics that enable control over the defect’s spin and orbital degrees of freedom and review fabrication techniques for creating single NV centers with nanometer-scale placement accuracies. We also discuss efforts, motivated by the success of diamond NV center applications, to identify defect spins with similar properties to the NV center in more technologically mature semiconductors such as SiC.

Aluminum hydride (AlH3), and the complex aluminum hydrides (e.g., M3AlH6, MAlH5, M2AlH7, M(AlH4)n), make up a fascinating class of materials that have received considerable attention over the past 60 years for their use as explosives, reducing agents, solid rocket propellants, as well as a hydrogen source for portable power systems. The recent renaissance in hydrogen storage research, particularly for automotive applications, has generated renewed interest in aluminum-based hydrides due to their capacity to store up to 11 wt% hydrogen with volumetric capacities up to 150 g H2/L (more than twice that of liquid hydrogen). In addition, hydrogen can be released from these materials by low temperature thermolysis (<100°C), making them well-suited for proton exchange membrane fuel cells and other low temperature applications. This article covers recent research on aluminum-based hydrides, including crystal structures, thermodynamics, kinetics, hydrogenation conditions, and regeneration methods.

Molecular imaging scans cellular and molecular targets in living subjects through the introduction of imaging agents that bind to these targets and report their presence through a measurable signal. The picomolar sensitivity, signal stability, and high multiplexing capacity of Raman spectroscopy satisfies important needs within the field of molecular imaging, and several groups now utilize Raman and surface-enhanced Raman spectroscopy to image molecular targets in small animal models of human disease. This article details the role of Raman spectroscopy in molecular imaging, describes some substrates and imaging agents used in animal models, and illustrates some examples.