Nature has developed myriad ways for organisms to interact with their environment using light and electronic signals. Optical and electronic properties can be observed macroscopically by measuring light emission or electrical current, but are conferred at the molecular level by the arrangement of small biological molecules, specifically proteins. Here, we present a brief overview of the current uses of proteins for applications in optical and electronic materials. We provide the natural context for a range of light-emitting, light-receiving, and electronically conductive proteins, as well as demonstrate uses in biomaterials. Examples of how genetic engineering has been used to expand the range of functional properties of naturally occurring proteins are provided. We touch on how approaches to patterning and scaffolding optical and electronic proteins can be achieved using proteins with this inherent capability. While much research is still required to bring their use into the mainstream, optical and electronic proteins have the potential to create biomaterials with properties unmatched using conventional chemical synthesis.

Plasmonic nanostructures possess broadly tunable optical properties with catalytically active surfaces. They offer new opportunities for achieving efficient solar-to-chemical energy conversion. Plasmonic metal–semiconductor heterostructures have attracted heightened interest due to their capability of generating energetic hot electrons that can be collected to facilitate chemical reactions. In this article, we present a detailed survey of recent examples of plasmonic metal–semiconductor heterostructures for hot-electron-driven photochemistry, including plasmonic metal–oxide, plasmonic metal–two-dimensional materials, and plasmonic metal–metal–organic frameworks. We conclude with a discussion on the remaining challenges in the field and an outlook regarding future opportunities for designing high-performance plasmonic metal–semiconductor heterostructures for photochemistry.

Electrochemical water splitting is one of the promising energy-conversion technologies to utilize intermittent renewable energy and produce hydrogen for clean energy. Pyrite-type transition-metal dichalcogenides have great potential to be applied for energy conversion. This article reviews recent progress in the performance of pyrite-type nanomaterials on the hydrogen evolution reaction, including an overview of crystal and electronic structure of pyrites and the principles of improving electrocatalytic activity and stability for S-based, Se-based, ternary, and other pyrites.

Transient electronics represents recent technology that can partially or completely degrade, dissolve, or disintegrate under certain conditions in actively and passively controlled ways. They offer applications as eco-friendly alternatives to existing electronic components, implantable biomedical devices, and software/hardware protection systems. The degradable characteristics of materials and circuits, however, lead to various fabrication issues and difficulties in manufacturing complex systems requiring fine and elaborate design layouts and microfabrication procedures under thermally and chemically harsh conditions. Identifying advanced materials and the development of manufacturing processes compatible with established transient materials have been conducted for several years to address these issues. In this article, we focus on recent trends in manufacturing technologies for transient electronic systems, including direct fabrication of electronics on transient substrates using organic–inorganic electronic materials, screen-printing approaches particularly for conductive traces, microfabrication combined with multiple transfer-printing techniques, and large-scale, foundry-compatible technologies.

Additive manufacturing (AM) comprises a group of transformative technologies that are likely to revolutionize manufacturing. In particular, laser-based metal AM techniques can not only fabricate parts with extreme complexity, but also provide innovative means for designing and processing new metallic systems. However, there are still several technical barriers that constrain metal AM. Overcoming these barriers requires a better understanding of the physics underlying the complex and dynamic laser–metal interaction at the heart of many AM processes. This article briefly describes the state of the art of in situ/operando synchrotron x-ray imaging and diffraction for studying metal AM, mostly the laser powder-bed fusion process. It highlights the immediate impact of operando synchrotron studies on the advancement of AM technologies, and presents future research challenges and opportunities.

Low-dimensional superconductors have been at the forefront of physics research due to their rich physical properties such as high-temperature (Tc) superconductivity. In this article, we review the field of emergent high-Tc superconductivity at interfaces of heterostructures, focusing on the experimental advances and its physical mechanism. Charge transfer between constituent materials leads to two-dimensional carrier confinement that facilitates occurrence of superconductivity at the interface. We discuss the similarities between bulk high-Tc superconductors and interface systems, as well as implications from a survey of interface superconductors. We expect that the hybrid heterostructures and the ability to manipulate them on an atomic scale could be an enormously fertile ground to explore superconductivity with higher critical temperature Tc.

At the forefront of developments in synchrotron x-ray microscopy, nanoscale-resolution high-dimensional spectrotomography under controlled sample environments has been demonstrated. Such cutting-edge experimental capability has been broadly applied to scientific studies in the field of energy materials science, where the dynamically evolving structural and chemical defects play a vital role in the functionality. In this article, we review novel developments of this technique from both experimental and data/information mining perspectives. Using studies on lithium-ion battery electrode materials as examples, we highlight the rich information in the high-dimensional and high-resolution x-ray tomographic data, which can be used to interpret the complicated thermal-electro-chemo-mechanical interplay that occurs under the operating conditions and collectively determines battery performance. We also discuss the frontier challenges in this field and our perspectives of the future directions in the context of projected major developments in the landscape of large-scale x-ray facilities across the globe.

One of the leading challenges in chemical sciences is the separation of complex mixtures. This is of vital importance for areas such as commodity chemical generation, where there is a need for the generation of high-purity chemical streams. Due to this, there has been a strong push toward the investigation of new materials capable of achieving chemoselective separation, with self-assembled materials having shown a great deal of promise for such separations. Many self-assembled materials are desirable candidates due to their low-cost synthesis, structural self-regulation, tunable properties, and an overall ease of composite material preparation. In this article, we aim to introduce examples of novel self-assembled materials and their practical usage in chemical separations. The specific approaches to fabricate these materials, as well as the strengths and shortcomings associated with their structures, will also be described. The strategies presented here will emphasize the production and employment of nonconventional self-assembled materials that exhibit a high potential for the advancement of the science of chemical separations.

Topological quantum materials are a class of compounds featuring electronic band structures, which are topologically distinct from common metals and insulators. These materials have emerged as exceptionally fertile ground for materials science research. The topologically nontrivial electronic structures of these materials support many interesting properties, ranging from the topologically protected states, manifesting as high mobility and spin-momentum locking, to various quantum Hall effects, axionic physics, and Majorana modes. In this article, we describe different topological matters, including topological insulators, Weyl semimetals, twisted graphene, and related two-dimensional Chern magnetic insulators, as well as their heterostructures. We focus on recent materials discoveries and experimental advancements of topological materials, and their heterostructures. Finally, we conclude with prospects for the discovery of additional topological materials for studying quantum processes, quasiparticles and their composites, as well as exploiting potential applications of these materials.

Atomic electron tomography (AET) has become a powerful tool for atomic-scale structural characterization in three and four dimensions. It provides the ability to correlate structures and properties of materials at the single-atom level. With recent advances in data acquisition methods, iterative three-dimensional (3D) reconstruction algorithms, and post-processing methods, AET can now determine 3D atomic coordinates and chemical species with sub-Angstrom precision, and reveal their atomic-scale time evolution during dynamical processes. Here, we review the recent experimental and algorithmic developments of AET and highlight several groundbreaking experiments, which include pinpointing the 3D atom positions and chemical order/disorder in technologically relevant materials and capturing how atoms rearrange during early nucleation at four-dimensional atomic resolution.

Transient energy supply remains one of the key challenges limiting the development of transient implantable medical devices for monitoring, diagnosis, and treatment of diseases within a predetermined time frame. A key feature of such devices is their controllable degradation during service life. An on-board transient energy supply with predictable performance over time is required to drive transient electronics. In this article, we present recent advances in the development of materials for biodegradable energy-storage devices (batteries and supercapacitors) and biodegradable energy-harvesting systems (enzymatic biofuel cells and triboelectric nanogenerators). Future perspectives, challenges, and opportunities related to energy materials for transient power sources will also be summarized.

Metal-halide perovskites, in particular their nanocrystal forms, have emerged as a new generation of light-emitting materials with exceptional optical properties, including narrow emissions covering the whole visible region with high photoluminescence quantum efficiencies of up to near-unity. Remarkable progress has been achieved over the last few years in the areas of materials development and device integration. A variety of synthetic approaches have been established to precisely control the compositions and microstructures of metal-halide perovskite nanocrystals (NCs) with tunable bandgaps and emission colors. The use of metal-halide perovskite NCs as active materials for optoelectronic devices has been extensively explored. Here, we provide a brief overview of recent advances in the development and application of metal-halide perovskite NCs. From color tuning via ion exchange and manipulation of quantum size effects, to stability enhancement via surface passivation, new chemistry for materials development is discussed. In addition, processes in optoelectronic devices based on metal-halide perovskite NCs, in particular, light-emitting diodes and radiation detectors, will be introduced. Opportunities for future research in metal-halide perovskite NCs are provided as well.

Additive manufacturing is a revolutionary three-dimensional (3D) printing technology that has applications in a vast number of fields from aerospace to biological engineering. In the field of bioengineering, it was recently discovered that the principles used in 3D bioprinting of organs and tissues could also be used to 3D print biological materials produced by genetically engineered bacteria. This new technology requires the development of modified bio-ink and optimized printing parameters to promote bacterial physiology while allowing printability. In this article, we highlight the recent advancements in additive manufacturing of engineered living materials using bacteria and their potential applications. We will discuss recent progress and significance of additive manufacturing of proteins and polypeptides produced in situ by engineered bacteria to make multifunctional materials. Finally, we discuss the challenges and prospects of this technology and highlight some of the biomaterials that may benefit from additive manufacturing with bacteria.

Liquid phase (or liquid cell) transmission electron microscopy (LP-TEM) has been established as a powerful tool for observing dynamic processes in liquids at nanometer to atomic length scales. However, the simple act of observation using electrons irreversibly alters the nature of the sample. A clear understanding of electron-beam-driven processes during LP-TEM is required to interpret in situ observations and utilize the electron beam as a stimulus to drive nanoscale dynamic processes. In this article, we discuss recent advances toward understanding, quantifying, mitigating, and harnessing electron-beam-driven chemical processes occurring during LP-TEM. We highlight progress in several research areas, including modeling electron-beam-induced radiolysis near interfaces, electron-beam-induced nanocrystal formation, and radiation damage of soft materials and biomolecules.

Sustainable and green energy sources are in high demand to meet the current human energy needs and environmental requirements. Hydrogen energy, with the highest energy density and zero carbon emission, is considered a potential solution. Hydrogen is primarily produced by splitting water. Rationally designed electrocatalysts are required to promote the cathodic hydrogen evolution reaction (HER) and the anodic oxygen evolution reaction (OER). Organic polymer matrices provide new opportunities for electrocatalytic water splitting due to their special physical and chemical characteristics and thermal stability. This article explains the role of organic polymers in electrocatalytic water decomposition from three aspects: ion-conductive polymers, conjugated conductive polymers, and carbon materials derived from organic polymers. We hope that this article will provide more rational ideas and promote the design of organic polymers for water-splitting electrocatalysis, and furnish more technical insights for the future of water electrolysis.

Nanostructures of plasmonic metals naturally combine strong light–matter interactions with catalytic activity, enabling new opportunities for light harvesting, catalytic chemistry, and artificial photosynthesis. Numerous studies have demonstrated that the optical excitation of localized surface plasmons generates hot electrons that can activate adsorbates triggering or facilitating chemical reactions on the surface of the nanoparticle. Going beyond such hot-electron-activated chemistry, a body of studies has shown that electron and hole carriers can be harvested from a plasmonically excited nanoparticle and utilized as redox equivalents for driving chemical reactions involving charge transfer. This article reviews such photoredox chemistry driven by plasmonic excitation of metal nanoparticles. Under certain conditions, a plasmonically excited nanoparticle can catalyze multielectron, multiproton transformations such as the photosynthesis of CO2 to hydrocarbons. We describe how the free energy of plasmonically generated charge carriers can be harvested and utilized for thermodynamically uphill reactions involving the formation of energy-rich chemical bonds or the development of molecular complexity. We end with a discussion of future opportunities in plasmon-excitation-driven photoredox chemistry.

The field of nonlinear optics is a well-established discipline that relies on macroscopic media and employs propagation distances longer than a wavelength of light. Recent progress with electromagnetic metamaterials has allowed for the expansion of this field into new directions of new phenomena and novel functionalities. In particular, nonlinear effects in thin, artificially structured materials such as metasurfaces do not rely on phase-matching conditions and symmetry-related selection rules of natural materials; they may be substantially enhanced by strong local and collective resonances of fields inside the metasurface nanostructures. Consequently, nonlinear processes may extend beyond simple harmonic generation and spectral broadening due to electronic nonlinearities. This article provides a brief review of basic concepts and recent results in the field of nonlinear optical metasurfaces.

Implantable neural interfaces are important tools to accelerate neuroscience research and translate clinical neurotechnologies. The promise of a bidirectional communication link between the nervous system of humans and computers is compelling, yet important materials challenges must be first addressed to improve the reliability of implantable neural interfaces. This perspective highlights recent progress and challenges related to arguably two of the most common failure modes for implantable neural interfaces: (1) compromised barrier layers and packaging leading to failure of electronic components; (2) encapsulation and rejection of the implant due to injurious tissue–biomaterials interactions, which erode the quality and bandwidth of signals across the biology–technology interface. Innovative materials and device design concepts could address these failure modes to improve device performance and broaden the translational prospects of neural interfaces. A brief overview of contemporary neural interfaces is presented and followed by recent progress in chemistry, materials, and fabrication techniques to improve in vivo reliability, including novel barrier materials and harmonizing the various incongruences of the tissue–device interface. Challenges and opportunities related to the clinical translation of neural interfaces are also discussed.

Synchrotron x-rays are a powerful tool to probe real-time changes in the microstructure of materials as they respond to an external stimulus, such as phase transformations that take place in response to a change in temperature. X-ray imaging techniques include radiography and tomography, and have been steadily improved over the last decades so that they can now resolve micrometer-scale or even finer structural changes in bulk specimens over time scales of a second or less. Under certain conditions, these imaging approaches can also give spatially resolved chemical information. In this article, we focus on the liquid to solid transformation of metallic alloys and the temporal and spatial resolution of the accompanying segregation of alloying elements. The solidification of alloys provides an excellent case study for x-ray imaging because it is usually accompanied by the progressive, preferential segregation of one or more of the alloying elements to either the solid or the liquid, and gives rise to surprisingly complex chemical segregation patterns. We describe chemical mapping investigations of binary and quasi-binary alloys using radiography and tomography, and recent developments in x-ray fluorescence imaging that offer the prospect of a more general, multielement mapping technique. Future developments for synchrotron-based chemical mapping are also considered.

Self-assembly enables hierarchical organization and compartmentalization of matter previously observed only in natural materials. Simple chemical motifs can be used to fabricate structures with diverse range of architectures and properties. The design principles, originally found in nature, are being implemented in self-assembled materials. The examples include high mechanical strength of bones and nacre achieved through hierarchical organic–inorganic organization, and DNA nanotechnology enabled by complementary bonding of DNA molecules. Building materials with controlled architectures from the nanoscale to the macroscale will lead to a combination of properties that will have significant impacts on fields ranging from tissue regeneration to optoelectronics.