The new field of nano-ionics is expected to yield large improvements in the performance of oxide-based energy generation and storage devices based on exploiting size effects in ion conducting materials. The search for novel materials with enhanced ionic conductivity for application in energy devices has uncovered an exciting new facet of oxide interfaces. With judicious choice of the constituent materials, oxide heterostructures can exhibit enhanced ion mobility compared to the bulk counterparts. Here we review recent experimental and theoretical progress on enhancement of oxide-ion conductivity arising in oxide ultrathin layers and at their interfaces, and describe the different scenarios, space-charge effects, epitaxial strain, and atomic reconstruction at the interface, proposed to account for the observed conductivity enhancement.

Nitrogen-vacancy (NV) color centers in diamond are currently considered excellent solid-state magnetic field sensors. Their long coherence times at room temperature and their atomic size allow for achieving both high magnetic field sensitivity and nanoscale spatial resolution in ambient conditions. This article reviews recent progress in magnetic field imaging with NV centers. We focus on two topics: scanning probe techniques with single NV centers and their application in the imaging of nanoscale magnetic structures, as well as recent development of magnetometers with ensembles of NV centers, which image magnetic fields at micron-length scales with extremely high sensitivities.

The hydrogenation of metals often leads to changes in optical properties in the visible range. This allows for fundamental studies of the hydrogenation process, as well as the exploration of various applications using these optical effects. Here, we focus on recent developments in metal hydride-based optical fiber and plasmonic sensors and smart windows. Both applications benefit from the existence of a reflective metallic state, which is lost on hydrogenation and allows for large reversible optical changes. In this article, we review the status of both technologies and their prospects for applications.

Ionic liquids are well suited to the electrochemical synthesis of freestanding metallic nanowires as well as macroporous metals and semiconductors. Such materials are potentially interesting for future generation Li-ion batteries. As the energy density of current Li-ion batteries barely exceeds 0.15 kWh/kg (in contrast to the 12 kWh/kg of hydrocarbons), there is a need for new anode and cathode materials if electrically driven cars are to have more than a 150 km cruising range at an affordable price. Freestanding aluminum nanowires and macroporous aluminum are easily feasible from AlCl3-based ionic liquids and show promising charge/discharge behavior even with ionic liquids as electrolytes. The challenges and the potential to make nanowires or macroporous structures of semiconductors (Si, Ge) are also briefly discussed.

State-of-the-art colloidal quantum dots (CQDs) exhibit excellent properties as pure color red, green, and blue (RGB) phosphors for light-emitting applications ranging from solid-state lighting to flat panel displays. Progress in controlling the chemical synthesis of II–VI semiconductor nanocrystals has enabled a better understanding of the fundamental physical processes that dictate their interactions with light at the quantum level. In this article, we review recent work that extends this understanding and the corresponding utility to a higher excitation regime, where optical gain and laser action have been demonstrated across the RGB color spectrum from a single material. Recent developments have surmounted some fundamental challenges to CQDs for optical gain and have made gains toward their possible future as full-color palette lasers.

Rechargeable batteries are essentially unstable systems with respect to charging/discharging. The main electrode reactions of all battery chemistries are well known but are valid and reversible only at small currents. When batteries are used with nonzero current, gradients in voltage, current, and temperature will arise and initiate a number of less understood parasitic reactions. If all these rather complicated and interconnected reactions are not reversible upon charging/discharging, the battery will derail after a number of charging/discharging cycles. This article describes two ways to improve performance. One is to choose applications where the battery is not deeply discharged, such as in hybrid electric vehicles. In battery electric vehicle applications, this would correspond to working with a significantly oversized battery. The second way is to improve uniformity and quality of design and materials of metal hydride electrodes; however, this will also drastically increase cost, and for a battery application, the total throughput of available energy over the lifetime cost of the battery must be maximized. Uniform metal hydride particles with a large and uniform reaction surface are examples of how to increase battery performance by making the electrodes work under more ideal conditions, which slows down the deteriorating influence from the parasitic reactions.

Fifteen years ago, the field of cell and organ printing began with a few research groups looking to take newly developed direct-write tools and apply them to living cells. Initial experiments demonstrated cell viability and functionality post-deposition. Recently, research has begun in earnest to create three-dimensional cellular constructs that mimic both the heterogeneous structure and function of natural tissue. Several companies are now marketing cell printers, expanding access to a wider group of scientists and accelerating the pace of development. This article describes the past decade and a half of research by showing examples of some of the most sophisticated work, comparing the approaches and tools used in the field, and predicting the products that will arrive in the not too distant future.

The ability to control the shape of metal nanocrystals is central to advances in many areas of modern science and technology, including catalysis, plasmonics, electronics, and biomedicine. This article provides a brief overview of our recent efforts toward the development of solution-phase methods for shape-controlled synthesis of metal nanocrystals. While the synthetic methods only involve simple redox reactions, we have been working diligently to understand the complex nucleation and growth mechanisms leading to the formation of metal nanocrystals with desired shapes and related properties. We hope this review will inspire new ideas and concepts in the general area of nanomaterial synthesis, expand our ability to engineer the properties of metals for various applications, and contribute to the realization of sustainable use for some of the scarcest materials.

The use of the nitrogen-vacancy (NV) center in diamond as a single spin sensor or magnetometer has attracted considerable interest in recent years because of its unique combination of sensitivity, nanoscale resolution, and room temperature operation. These properties, together with long-term photostability of the NV fluorescence and the inherent biocompatibility of diamond, make the NV system ideal for applications in biology. This article focuses on the role of the NV center in biological applications from optical tracking to nanoscale sensing.

When colloidal nanoparticles made of soft magnetic materials have strong interparticle interactions, new magnetic phases may be formed, such as super-ferromagnets or super-spin glasses, with different local temperature and field-dependent magnetization dynamics. Magneto-transport experiments on nanoscale tunnel junctions formed in magnetic nanoparticle arrays, defined either by scanning probe tips or patterned nanoscale electrodes, can be used as probes of the magnetization dynamics.

There are numerous applications of nanoporous materials, including gas storage, separation, and purification. In recent years, the number of available nanoporous materials has increased substantially, with new material classes, such as metal-organic frameworks and microporous organic polymers, joining the traditional adsorbents, which include activated carbons, porous silicas, and zeolites. The determination of the gas adsorption properties of these materials is critical to both the development of new materials for targeted applications and the assessment of the suitability of a material for a particular technology. In this article, we provide an overview of nanoporous materials and their gas adsorption properties, existing and future applications for new materials, adsorption measurement methods, and the experimental challenges involved in the determination of gas adsorption both at elevated pressures and from multicomponent mixtures.

A review is presented of the development of in situ high-resolution transmission electron microscopy (HRTEM) and its application to directly study the atomic behavior in thermally activated material reactions. Not only are the atomic re-arrangements continuously recorded, but kinetic measurements can be made at controlled elevated temperatures. Examples include work on the atomic motion on CdTe surface ledges, solid phase epitaxial regrowth of silicon, crystallization of amorphous silicon and of amorphous tantalum oxide thin films, solid-state amorphization at metal-silicon interfaces, metal-induced crystallization of amorphous silicon, germanium and carbon, phase separation and crystallization in hafnium silicate thin films, and “spiking” across thin gate oxides separating nickel silicide from a monocrystalline silicon substrate. The future prospects of in situ HRTEM are discussed, and the increasing breadth of application of this approach is recognized, especially in light of the advances in HRTEM capabilities.

This article provides an overview of the basic aspects of the structure and dynamics of excitons in molecular crystals that give rise to their unique spectroscopic behavior. The two different types of optically accessible excitons, charge-transfer and Frenkel, are described and their different properties discussed. Particular attention is paid to the spin properties of Frenkel excitons (i.e., singlet and triplet) and also to their coupling to intramolecular vibrations. Experimental challenges in the study of molecular crystal optical properties are also reviewed, including their high optical density, complex refractive index behavior, and issues with sample crystallinity and chemical purity. Once created, excitons in molecular crystals can exhibit interesting dynamical behavior, including diffusion over large length scales and ionization into electron–hole pairs. Exciton–exciton interactions are also important, ranging from fusion or annihilation (two excitons combine into one exciton) to fission (one exciton splits into two excitons). The long-range diffusion and exciton fission effects have particular relevance for the design of organic photovoltaic materials.

Watson and Crick’s discovery of the structure of DNA in 1953 and the near-simultaneous advent of the first silicon transistor in 1954 spurred parallel historic advances over the following decades in molecular biology and materials technology. As these two expansive fields of research have progressed, important areas of overlap have included the extensive use of materials innovations in biological research, such as in microscopy and measurement systems, while materials research has benefited from efforts to mimic design principles utilized in nature. Until relatively recently, however, the molecular mechanisms that underpin nature’s biological orchestra have remained largely outside the purview of materials research. Now, with new abilities to harness and modify biomolecular and cellular systems, evidence is mounting that biology can be fruitfully utilized to directly engineer technological materials. This article aims to highlight the importance of DNA-driven routes to new materials while providing a brief overview of the genetic engineering platforms that make these routes possible. Emphasis is placed on the fact that it is now possible to genetically evolve materials technologies in a manner that mimics the genetic evolution of biominerals in nature.

Biological materials are effectively synthesized, controlled, and used for a variety of purposes in Nature—in spite of limitations in energy, quality, and quantity of their building blocks. Whereas the chemical composition of materials in the living world plays some role in achieving functional properties, the way components are connected at different length scales defines what material properties can be achieved, how they can be altered to meet functional requirements, and how they fail in disease states and other extreme conditions. Recent work has demonstrated this using large-scale computer simulations to predict materials properties from fundamental molecular principles, combined with experimental work and new mathematical techniques to categorize complex structure-property relationships into a systematic framework. Enabled by such categorization, we discuss opportunities based on the exploitation of concepts from distinct hierarchical systems that share common principles in how function is created, even linking music to materials science.