Mrs Bulletin最新文献

Abstract

This study investigated the precipitation strengthening of chemically disordered Cu-rich phase and its effect on the mechanical properties of Cu-doped Fe18Cr14Ni3Mo austenitic steels. A high density of Cu-rich nanoprecipitates with fully coherent structure were formed in the austenitic matrix. These nano-sized Cu-rich nanoprecipitates improved the strength of alloys by hindering the movement of grain boundaries, revealing the disordering strengthening effect. Meanwhile, dense precipitates prevented grain growth, thereby improving grain refinement and further increasing the strength. Particularly, samples with Cu alloying exhibited a more pronounced grain refinement effect on grain-refined samples compared to ones without alloying, thus showing a more significant strengthening effect. The findings of this study not only offer guidance for the design of high-strength materials via disordering effects but also provide new insights in fabricating the ultrafine grain materials.

Impact statement

In this study, we successfully prepared forged austenitic steels with Cu-rich phases via a cold rolling process. Dense Cu-rich phases improved alloy strength by hindering dislocation movement and preventing grain growth, leading to grain refinement. The influence of Cu-rich phase precipitation on mechanical properties and microstructures of Fe18Cr14Ni3Mo4Cu austenitic steels, both virgin and grain-refined, was systematically analyzed and compared. Results showed that mechanical property enhancement in Cu-doped samples was mainly due to grain-refinement and precipitation strengthening. Notably, the role of Cu-rich phases in grain refinement became more significant after cold rolling. Compared to the grain-refined undoped Cu samples, the average grain size of the Cu-doped grain-refined samples was reduced by a factor of 3.2, and the yield strength was increased by a factor of 1.4, demonstrating the effect of Cu-rich phases in preventing grain growth and achieving grain refinement.

Graphical abstract

Abstract

Spider silk is an archetypal biopolymer material with extreme tensile properties arising from its complex hierarchical assembly. While recent advances in sequencing have yielded abundant insights, relatively little is known concerning post-translational modifications (PTMs) in spider silk. Here, we probe the PTM landscape of dragline silk from the Jorō spider (Trichonephila clavata) using a combination of mass spectroscopy and solid-state nuclear magnetic resonance (NMR). The results reveal a wide array of potential modifications, including hydroxyproline, phosphorylation, and dityrosine cross-links, encompassing the different spidroin constituents. Notably, the MaSp3 repetitive region displayed numerous PTMs, whereas MaSp1 and MaSp2 variants showed distinct phosphorylation patterns in its terminal domains. The N-terminal domain (NTD) phosphorylation sites were found predominantly at the dimer interface, suggesting a modulatory function with respect to its pH-driven dimerization function, a hypothesis supported by studies using phosphomimetic NTD mutants. Possible roles of phosphoserine in limiting β-sheet formation, and hydroxyproline in disrupting β-turns are also discussed.

Impact statement

Spider silk is an archetypal biomaterial that can outperform our most sophisticated artificial fibers. The secret to its mechanical properties lies in its complex hierarchical structure—encompassing the nano- to macroscales—that forms through a process of molecular self-assembly of the constituent spidroin proteins. While recent advances in "biomateriomics” have given us tremendous insights into the sequence–function relationships that determine spider silk behavior, the picture is still far from complete. One area that has received little attention is posttranslational modifications (PTMs). PTMs are ubiquitous biological phenomena that are crucial for providing dynamic control of the proteome, and effectively expand the structural and functional design space of proteins beyond that provided by the canonical amino acids. Here, we undertook a comprehensive analysis of PTMs from spider dragline silk fiber, which revealed numerous potential sites for a wide array of modifications. The results provide a fascinating window into additional layers of complexity underlying the mechanical behavior of spider silk, and suggest further avenues for creating novel, dynamically tunable, bioinspired materials.

Graphical abstract

Hybrid halide perovskites (HPs) are emerging as the most promising materials for near-future photovoltaics (PV) due to their unique optoelectronic properties, such as their low defect density and broad absorption, making them highly efficient photoactive materials. Meanwhile, their low cost and low embodied energy, together with their solution processability and the possibility to create solar cells on flexible substrates, make them among the potential winning concepts for the next-generation PV market. Large-scale marketing, however, requires solving current challenges, which mainly relate to device longevity and scaling up. In this article, we put in perspective the key aspects of HP materials and HP-solar cells, briefly discussing their historical path to high efficiency, reviewing the state of the art, presenting their main advantages over existing technologies, and the main challenges the research community needs to overcome. Recent achievements and hot areas today critical for market uptake will be presented.

Graphical abstract

An exciton is a bound pair of negatively charged electron and positively charged hole (electron vacancy within a solid), both of which are held together by their mutual Coulomb attraction to form a bound state. One hundred years after their discovery, excitons act as the backbone of a large class of low-dimensional and quantum materials showing a truly “exotic” set of physical, chemical as well as biophysical properties. In this issue of MRS Bulletin, we designate all such materials whose properties are crucially dependent on the presence of these excitons as “Excitonic materials.” Current studies of these materials are progressing rapidly in newer directions, including those in novel materials and next-generation technologies. Therefore, the main focus of this issue is to catch recent progresses in the physics of “excitons” and “excitonic materials,” encompassing both fundamental understandings of the nature of these quasiparticles and their emerging device applications in various fields. This article is an overview of this issue, recalling the basics of exciton physics, the historical contexts, and recent progresses without claiming to be exhaustive.

Graphical Abstract

Within the last few years, Rydberg excitons, bound electron–hole pairs in highly excited states, have emerged as a promising technology platform for quantum nonlinear optics, quantum information processing, and quantum sensing. The advanced device designs and sensing concepts in these fields require strong nonlinearities at the few-photon or few-carrier level. Rydberg states offer the required strong nonlinearities as the relevant physical quantities at the heart of such nonlinear effects scale strongly with the principal quantum number, n, of the excited state: For example, their polarizability scales as (n^7), resulting in an enormous sensitivity to external fields. We review recent experimental and theoretical results that pave the way toward quantum sensing of the electric fields originating from static charge carriers and strongly diluted electron–hole plasmas. We also discuss the strong nonlinear optical properties of Rydberg excitons and how they could be utilized in terms of sensing.

Graphical abstract

The regime of strong coupling between photons and excitons gives rise to hybrid light–matter particles with fascinating properties and powerful implications for semiconductor quantum technologies. As the properties of excitons crucially depend on their host crystal, a rich field of exciton–polariton engineering opens by exploiting the diversity of semiconductors currently available. From dimensionality to binding energy to unusual orbitals, various materials provide different fundamental exciton properties that are often complementary, enabling vast engineering possibilities. This article aims to showcase some of the main materials for strong light–matter engineering, focusing on their fundamental complementarity and what this entails for future quantum technologies.

Graphical abstract

Abstract

As quantum communication channels, single photons render an excellent platform, which is why they are called flying qubits. They are easily transported over long distances via fibers or even satellites due to their remarkably weak interaction with each other. Therefore, some sort of link between photons is required to carry out quantum operations. Ideally, this process is carried out on a robust solid-state chip infrastructure. In this context, excitons (i.e., bound electron–hole pairs in semiconductors) are an ideal connection between photons and the solid state. Due to their mostly strong dipole character, excitons can be efficiently created by photons and inversely create photons upon recombination. This makes excitons in various semiconductor platforms key players in modern quantum technology approaches. While in extended crystal systems, excitons can be transported, their confinement to quasi-0D is used to create stationary solid-state qubits. In addition, excitons provide interactions with other degrees of freedom that can be harnessed in quantum technologies (i.e., spin or mechanical excitations of the host crystal lattice). Here, we review different approaches that use static or dynamic strain to tailor the optical properties of excitons or provide transport channels for excitons. We highlight approaches in traditional bulk semiconductor platforms and modern van der Waals semiconductors.

Graphical abstract

Metal-halide perovskites (MHPs) with unique electronic and optical properties have emerged as promising materials with a broad spectrum of applications in photovoltaics, optoelectronic, and photonic devices. The distinct properties and tremendous potential of MHPs are intricately defined by excitons and collective quantum states. This article reviews the excitonic states and coordinated interplay of charge, spin, and lattice. We discuss the recent experimental and theoretical discoveries of excitonic phenomena, as well as correlated states involving condensation and cooperative emission. Additionally, our exploration extends to the structural properties of MHPs that facilitate the emergence of robust quantum states, even at room temperatures. Finally, an overview of the remaining challenges and potential applications of MHPs in quantum optics, coherent light sources, electrically driven amplified spontaneous emission, and superfluorescent lasing is provided.

Graphical abstract

Abstract

Mycelium is crucial in decomposing biomass and cycling nutrients in nature. While various environmental factors can influence mycelium growth, the role of substrate mechanics is not yet clear. In this study, we investigate the effect of substrate stiffness on mycelium growth. We prepared agar substrates of different concentrations to grow the mycelium, but kept other environmental and chemical conditions consistent. We made a time-lapse recording of the growing history with minimum interruption. We repeated our tests for different species. Our results generally support that mycelium grows faster on a stiffer substrate, Ganoderma lucidum gives the highest growth rate and Pleurotus eryngii is most sensitive to substrate stiffness. We combined experimental characterization and computational simulation to investigate the mechanism and discovered that mycelium concentrates on the surface of a rigid substrate, but penetrates the soft one. Our Monte Carlo simulations illustrate that such a penetration allows mycelium to grow in the three-dimensional space, but effectively slows down the surface occupation speed. Our study provides insights into fungal growth and reveals that the mycelium growth rate can be tuned through substrate stiffness, thus reducing the time for producing mycelium-based composites.

Impact statement

We used agar substrates and tuned its stiffness to culture mycelium and compared tune its stiffness to culture mycelium and compare its growth in a well-controlled condition. Our results revealed that mycelium grows faster on stiffer substrates, thus fully occupying the petri dish surface more quickly. We repeated our study several times by testing four species, P. eryngii, G. lucidum, Trametes versicolor, and Flammulina velutipes, and the stiffest substrate always gives the highest mean growing rate than others. The G. lucidum shows the highest spreading rate that is obtained on the stiffest substrate as 39.1 ± 2.0 mm²/h. We found that the mycelium on a soft substrate will grow into the substrate instead of spreading on the stiffer surface. Our Monte Carlo simulations further show that once the fibers grow into a three-dimensional substrate, its growth is slower than growing on a two-dimensional surface, providing a microscopic mechanism of the substrate stiffness effect. This study’s analysis of how substrate stiffness impacts mycelium growth is new, bridging a critical knowledge gap in understanding the relationship between substrate mechanics and fungal ecology. The knowledge from this study has a potential in accelerating sustainable manufacturing of mycelium-based composite by adjusting substrate mechanics.

Graphical Abstract