Spider dragline silk is a self-assembling protein that rivals many engineering fibers in strength, extensibility, and toughness, making it a versatile biocompatible material. Here, atomistic-level structures of wildtype MaSp1 protein from the Nephila clavipes spider dragline silk sequences, obtained using an in silico approach based on replica exchange molecular dynamics and explicit water, are subjected to nanomechanical testing and released preceding failure. We approximate the relaxation time from an exponential decay function, and identify permanent changes in secondary structure. Our work provides fundamental insights into the time-dependent properties of silk and possibly other protein materials.

It is widely believed that switching to the conductive state in memristive materials is triggered by the external field that drives defect dynamics. In polycrystalline materials, grain boundaries are further believed to cause switching by enabling faster defect motion. Here, we report a first-principle study of oxygen vacancy dynamics at a grain boundary (GB) in polycrystalline ZnO and show that switching to the conductive state is triggered by a recombination-enhanced motion of vacancies perpendicular to the GB. We call this mechanism the “breathing” trigger of memristive switching.

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.

Colloidal semiconductor nanocrystals, also known as “quantum dots” (QDs), represent an example of a disruptive technology for display and lighting applications. The QDs’ high luminescence efficiency and precisely tunable, narrow emission are nearly ideal for achieving saturated colors and enriching the display or TV color gamut. Quantum dot light-emitting diodes (QLEDs) can provide saturated emission colors and allow inexpensive solution-based device fabrication on almost any substrate. The first incorporation of QDs into the consumer market is using them as optical down-converters. Blue light from an efficient high energy light source (e.g., GaN blue LED) is absorbed and reemitted at any desired lower energy wavelength. Alternatively, electric current can be used for direct excitation of QDs. QLEDs are an exciting technical challenge and commercial opportunity for display and solid-state lighting applications. Recent developments in the field show that efficiency and brightness of QLEDs can match those of organic LEDs.

Kohn–Sham density functional theory is the most widely used method of electronic-structure calculation in materials physics and chemistry because it reduces the many-electron ground-state problem to a computationally tractable self-consistent one-electron problem. Exact in principle for the ground-state energy and electron density, it requires in practice an approximation to the density functional for the exchange-correlation energy. Common approximations fall on the rungs of a ladder, with higher rungs being more complicated to construct and use but potentially more accurate. Each rung of the ladder introduces an additional ingredient to the energy density. From bottom to top, the rungs are (1) the local spin density approximation, (2) the generalized gradient approximation (GGA), (3) the meta-GGA, (4) the hybrid functional, and (5) the generalized random phase approximation. The semi-local rungs (1–3) are important, because they are computationally efficient, they can be constructed non-empirically, they can serve as input to fourth-rung functionals, and the meta-GGA by itself can be accurate for equilibrium properties. Recent and continuing improvements to the meta-GGA are emphasized here.

Colloidal quantum dots (QDs) hold great promise as electrically excited emitters in light-emitting diodes (LEDs) for solid-state lighting and display applications, as highlighted recently by the demonstration of a red-emitting QD-LED with efficiency on par with that of commercialized organic LED technologies. In the past five years, important advances have been made in the synthesis of QD materials, the understanding of QD physics, and the integration of QDs into solid-state devices. Insights from this progress can be leveraged to develop a set of guidelines to direct QD-LED innovation. This article reviews the fundamental causes of inefficiency in QD-LEDs understood to date and proposes potential solutions. In particular, we emphasize the challenge in developing QD emitters that exhibit high luminescent quantum yields in the combined presence of charge carriers and electric fields that appear during traditional LED operation. To address this challenge, we suggest possible QD chemistries and active layer designs as well as novel device architectures and modes of QD-LED operation. These recommendations serve as examples of the type of innovations needed to drive development and commercialization of high-performance QD-LEDs.

Lighting consumes almost one-fifth of all electricity generated today. In principle, with more efficient light sources replacing incandescent lamps, this demand can be reduced at least twofold. A dramatic improvement in lighting efficiency is possible by replacing traditional incandescent bulbs with light-emitting diodes (LEDs) in which current is directly converted into photons via the process of electroluminescence. The focus of this article is on the emerging technology of LEDs that use solution-processed semiconductor quantum dots (QDs) as light emitters. QDs are nano-sized semiconductor particles whose emission color can be tuned by simply changing their dimensions. They feature near-unity emission quantum yields and narrow emission bands, which result in excellent color purity. Here, we review spectroscopic studies of QDs that address the problem of nonradiative carrier losses in QD-LEDs and approaches for its mitigation via the appropriate design of QD emitters. An important conclusion of our studies is that the realization of high-performance LEDs might require a new generation of QDs that in addition to being efficient single-exciton emitters would also show high emission efficiency in the multicarrier regime.