Strain Engineering Research Articles

Strain engineering in monolayer graphene via ZnO array substrates in schottky junction for enhanced optoelectronic performance

Strain engineering in monolayer graphene via ZnO array substrates in schottky junction for enhanced optoelectronic performance

Lattice strain engineering of Ni-doped Pd nanoparticles: Realizing efficient and CO-resistant alkaline hydrogen oxidation

Lattice strain engineering of Ni-doped Pd nanoparticles: Realizing efficient and CO-resistant alkaline hydrogen oxidation

Deletion of atypical type II restriction genes in Clostridium cellulovorans using a Cas9-based gene editing system.

The anaerobic bacterium Clostridium cellulovorans is a promising candidate for the sustainable production of biofuels and platform chemicals due to its cellulolytic properties. However, the genomic engineering of the species is hampered because of its poor genetic accessibility and the lack of genetic tools. To overcome this limitation, a protocol for triparental conjugation was established that enables the reliable transfer of vectors for markerless chromosomal modification into C. cellulovorans. The availability of reporter genes is another requirement for strain engineering and biotechnological applications. In this work, the oxygen-free fluorescence absorption-shift tag (FAST) system was used to characterize promoter strength in C. cellulovorans. Selected promoters were used to establish a CRISPR/Cas system for markerless chromosomal modifications. For stringent control of expression of Cas9, a theophylline-dependent riboswitch was used, and additionally, the anti-CRISPR protein AcrIIA4 was used to reduce the basal activity of the Cas9 in the off-state of the riboswitch. Finally, the newly established CRISPR/Cas system was used for the markerless deletion of the genes encoding two restriction endonucleases of a type II restriction-modification (RS) system from the chromosome of C. cellulovorans. In comparison to the WT, the conjugation efficiency when using the deletion mutant as the recipient strain was improved by about one order of magnitude, without the need for prior C. cellulovorans-specific in vivo methylation of the conjugative plasmid in the E. coli donor strain. KEY POINTS: • Quantification of heterologous promoters enables rational choice for genetic engineering. • CRISPR/Cas with riboswitch and anti-CRISPR allows efficient gene deletion in C. cellulovorans. • Conjugation protocol and type II REase deletion enhance genetic accessibility.

Towards higher electro-optic response in AlScN

Novel materials with large electro-optic (EO) coefficients are essential for developing ultra-compact broadband modulators and enabling effective quantum transduction. Compared to lithium niobate, the most widely used nonlinear optical material, wurtzite AlScN, offers advantages in nano-photonic devices due to its compatibility with integrated circuits. We perform detailed first-principles calculations to investigate the electro-optic effect in Al1−xScxN alloys and superlattices. At elevated Sc concentrations in alloys, the EO coefficients increase; importantly, we find that cation ordering along the c axis leads to enhanced EO response. Strain engineering can be used to further manipulate the EO coefficients of AlScN films. With applied in-plane strains, the piezoelectric contributions to the EO coefficients increase dramatically, even exceeding 250 pm/V. We also explore the possibility of EO enhancement through superlattice engineering, finding that nonpolar a-plane (AlN)m/(ScN)n superlattices increase EO coefficients beyond 40 pm/V. Our findings provide design principles to enhance the electro-optic effect through alloy engineering and heterostructure architecture.

Interfacial Strain-Driven Large Topological Hall Effects in Supermalloy Thin Films with Noncoplanar Spin Textures.

Materials exhibiting topological transport properties, such as a large topological Hall resistivity, are crucial for next-generation spintronic devices. Here, we report large topological Hall resistivities in epitaxial supermalloy (NiFeMo) thin films with [100] and [111] orientations grown on single-crystal MgO (100) and Al2O3 (0001) substrates, respectively. While X-ray reciprocal maps confirmed the epitaxial growth of the films, X-ray stress analyses revealed large residual strains in the films, inducing tetragonal distortions of the cubic NiFeMo unit cells. Magnetic force microscopy showed the presence of skyrmion-like features, which may arise from strain-induced spin texturing in the films. Magneto-optic Kerr effect confirmed a 4-fold magnetic anisotropy in the NiFeMo/MgO (100) film which exhibited a more pronounced topological Hall effect compared to that in the NiFeMo/Al2O3 (0001) film. We envisage that the strain-induced disruption of the centrosymmetry in the NiFeMo films possibly leads to Dzyaloshinskii-Moriya (DM) interactions within the spins. This gives rise to the skyrmion-like spin textures and notable topological Hall effects near room temperature hitherto unobserved in NiFeMo thin films. Theoretical simulations based on DM interactions strongly correlate the experimental results and corroborate with the presence of skyrmion-like spin textures in the films. The modulation of topology and magnetism in NiFeMo thin films through strain engineering may provide useful direction for the pursuit of quantum Hall effect based spintronic devices.

Strain Engineering of Ru–Co2Ni Nanoalloy Encapsulated with Carbon Nanotubes for Efficient Anion and Proton Exchange Membrane Water Electrolysis

AbstractAlloying atomically dispersed noble metals with earth‐abundant transition metal nanoparticles (NPs) presents a promising approach to enhance the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in water electrolysis. However, the challenge remains of reducing the size of the NPs without sacrificing high activity and durability. In this study, Ru–Co2Ni nanoalloy particles (NAPs) encapsulated in nitrogen‐doped carbon nanotubes (NCNTs) are introduced, forming a core‐shell electrocatalyst (Ru–Co2Ni@NCNT). This design leverages Ru site optimization, CNT density control, strain engineering, efficient water dissociation, and outstanding bubble release dynamics within the core‐shell structure. These factors significantly improve catalytic performance with low overpotentials of 35 and 57 mV overpotential in 1.0 m KOH and 0.5 m H2SO4 solutions, respectively, at a current density of 10 mA cm−2. Density functional theory (DFT) calculations reveal that while Ru sites serve as active sites, they also modify the electronic structure of Co and Ni, optimizing their hydrogen adsorption energies and improving HER efficiency. The Ru–Co2Ni@NCNT catalyst is successfully integrated into both anion exchange membrane (AEM) and proton exchange membrane (PEM) electrolyzers, demonstrating stable operation at 0.5 A cm−2 for 500 h, underscoring its potential for efficient and durable hydrogen production.

Dynamic tuning of terahertz atomic lattice vibration via cross-scale mode coupling to nanomechanical resonance in WSe2 membranes

Nanoelectromechanical systems (NEMS) based on atomically-thin tungsten diselenide (WSe2), benefiting from the excellent material properties and the mechanical degree of freedom, offer an ideal platform for studying and exploiting dynamic strain engineering and cross-scale vibration coupling in two-dimensional (2D) crystals. However, such opportunity has remained largely unexplored for WSe2 NEMS, impeding exploration of exquisite physical processes and realization of novel device functions. Here, we demonstrate dynamic coupling between atomic lattice vibration and nanomechanical resonances in few-layer WSe2 NEMS. Using a custom-built setup capable of simultaneously detecting Raman and motional signals, we accomplish cross-scale mode coupling between the THz crystal phonon and MHz structural vibration, achieving GHz frequency tuning in the atomic lattice modes with a dynamic gauge factor of 61.9, the best among all 2D crystals reported to date. Our findings show that such 2D NEMS offer great promises for exploring cross-scale physics in atomically-thin semiconductors.

Engineered CRISPR-Cas9 for Streptomyces sp. genome editing to improve specialized metabolite production

The CRISPR-Cas9 system has frequently been used for genome editing in Streptomyces; however, cytotoxicity, caused by off-target cleavage, limits its application. In this study, we implement innovative modification to Cas9, strategically addressing challenges encountered during gene manipulation using Cas9 within strains possessing high GC content genome. The Cas9-BD, a modified Cas9 with the addition of polyaspartate to its N- and C-termini, is developed with decreased off-target binding and cytotoxicity compared with wild-type Cas9. Cas9-BD and similarly modified dCas9-BD have been successfully employed for simultaneous biosynthetic gene cluster (BGC) refactoring, multiple BGC deletions, or multiplexed gene expression modulations in Streptomyces. We also demonstrate improved secondary metabolite production using multiplexed genome editing with multiple single guide RNA libraries in several Streptomyces strains. Cas9-BD is also used to capture large BGCs using a developed in vivo cloning method. The modified CRISPR-Cas9 system is successfully applied to many Streptomyces sp., providing versatile and efficient genome editing tools for strain engineering of actinomycetes with high GC content genome.

Manipulating Intracellular Oxidative Conditions to Enhance Porphyrin Production in Escherichia coli.

Being essential intermediates for the biosynthesis of heme, chlorophyll, and several other biologically critical compounds, porphyrins have wide practical applications. However, up till now, their bio-based production remains challenging. In this study, we identified potential metabolic factors limiting the biosynthesis of type-III stereoisomeric porphyrins in Escherichia coli. To alleviate this limitation, we developed bioprocessing strategies by redirecting more dissimilated carbon flux toward the HemD-enzymatic pathway to enhance the production of type-III uroporphyrin (UP-III), which is a key precursor for heme biosynthesis. Our approaches included the use of antioxidant reagents and strain engineering. Supplementation with ascorbic acid (up to 1 g/L) increased the UP-III/UP-I ratio from 0.62 to 2.57. On the other hand, overexpression of ROS-scavenging genes such as sod- and kat-genes significantly enhanced UP production in E. coli. Notably, overexpression of sodA alone led to a 72.9% increase in total porphyrin production (1.56 g/L) while improving the UP-III/UP-I ratio to 1.94. Our findings highlight the potential of both antioxidant supplementation and strain engineering to mitigate ROS-induced oxidative stress and redirect more dissimilated carbon flux toward the biosynthesis of type-III porphyrins in E. coli. This work offers an effective platform to enhance the bio-based production of porphyrins.

Promoter engineering with programmable upstream activating sequences in Aspergillus Niger cell factory

BackgroundAspergillus niger is an important industrial filamentous fungus used to produce organic acids and enzymes. A wide dynamic range of promoters, particularly strong promoters, are required for fine-tuning the regulation of gene expression to balance metabolic flux and achieve the high yields of desired products. However, the limited understanding of promoter architectures and activities restricts the efficient transcription regulation of targets in strain engineering in A. niger.ResultsIn this study, we identified two functional upstream activation sequences (UAS) located upstream of the core promoters of highly expressed genes in A. niger. We constructed and characterized a synthetic promoter library by fusing the efficient UAS elements upstream of the strong constitute PgpdA promoter in A. niger. It demonstrated that the strength of synthetic promoters was fine-tuned with a wide range by tandem assembly of the UAS elements. Notably, the most potent promoter exhibited 5.4-fold higher activity than the strongest PgpdA promoter reported previously, significantly extending the range of strong promoters. Using citric acid production as a case study, we employed the synthetic promoter library to enhance citric acid efflux by regulating the cexA expression in A. niger. It showed a 1.6-2.3-fold increase in citric acid production compared to the parent strain, achieving a maximum titer of 145.3 g/L.ConclusionsThis study proved that the synthetic promoter library was a powerful toolkit for precise tuning of transcription in A. niger. It also underscores the potential of promoter engineering for gene regulation in strain improvement of fungal cell factories.

Control of the Phase Distribution in TMDs by Strain Engineering and Kirigami Techniques.

Materials exhibiting both metallic and semiconducting states, including two-dimensional transition metal dichalcogenides (TMDs), have numerous applications. We therefore investigate the effects of axial and shear strains on the phase energetics of pristine and striped TMDs using density functional theory and classical molecular dynamics simulations. We demonstrate that control of the phase distribution can be achieved by the integration of strain engineering and Kirigami techniques. Our results extend the understanding of the phase energetics in TMDs and reveal an effective strategy for creating virtually defect-free metal-semiconductor-metal junctions.

Nanowrinkle waveguide in graphene for enabling secure Dirac fermion transport

Abstract Localized states in graphene have garnered significant attention in quantum information science due to their potential applications. Despite graphene’s superior transport and electronic properties compared to other semiconductors, achieving nanoscale confinement remains challenging due to its gapless nature. In this study, we explore the unique transport properties along nanowrinkles in monolayer graphene. We demonstrate the creation of a one-dimensional conduction channel by alternating pseudomagnetic fields along the nanowrinkle, enabling ballistic Dirac fermion transport without leakage. This suggests a feasible method for secure quantum information transfer over long distances. Furthermore, we extend our analysis to bent nanowrinkles, showcasing well-guided Dirac fermion propagation unless the bent angle is sufficiently large. Our demonstration of the nanowrinkle waveguide in graphene introduces a novel approach to controlling Dirac fermion transport through strain engineering, for quantum information technology applications.

Strain engineering tuned vibrational dynamics of 2D transition metal dichalcogenide heterostructures: a first-principles investigation.

Controlling vibrational modes and energy gap by creating van der Waals (vdW) heterostructures through strain engineering is a novel approach to tailor the vibrational and electronic properties of two-dimensional materials. Numerous theoretical and experimental studies have significantly contributed to analyzing the properties of transition metal dichalcogenides, known for their multifunctional applications. In this study, we investigate the strain and stacking dependent vibrational properties of WSe2/MoSe2and MoSe2/WSe2/MoSe2vdW heterostructures usingfirst-principlesbased density functional theory calculations. The dynamical stability of all vdW heterostructures makes them feasible in fabrication. Our phonon calculations and zone center phonon modes analysis signify that the interlayer interaction influences interlayer breathing and shear phonon modes, which play an important role in thermal properties. The effect of strain engineering on the vibrational modes and energy gap of vdW heterostructures are further discussed. The tensile and compressive biaxial strain on the vdW heterostructures results in phonon softening and hardening, respectively.

Addressing genome scale design tradeoffs in Pseudomonas putida for bioconversion of an aromatic carbon source

Genome-scale metabolic models (GSMM) are commonly used to identify gene deletion sets that result in growth coupling and pairing product formation with substrate utilization and can improve strain performance beyond levels typically accessible using traditional strain engineering approaches. However, sustainable feedstocks pose a challenge due to incomplete high-resolution metabolic data for non-canonical carbon sources required to curate GSMM and identify implementable designs. Here we address a four-gene deletion design in the Pseudomonas putida KT2440 strain for the lignin-derived non-sugar carbon source, p-coumarate (p-CA), that proved challenging to implement. We examine the performance of the fully implemented design for p-coumarate to glutamine, a useful biomanufacturing intermediate. In this study glutamine is then converted to indigoidine, an alternative sustainable pigment and a model heterologous product that is commonly used to colorimetrically quantify glutamine concentration. Through proteomics, promoter-variation, and growth characterization of a fully implemented gene deletion design, we provide evidence that aromatic catabolism in the completed design is rate-limited by fumarase hydratase (FUM) enzyme activity in the citrate cycle and requires careful optimization of another fumarate hydratase protein (PP_0897) expression to achieve growth and production. A double sensitivity analysis also confirmed a strict requirement for fumarate hydratase activity in the strain where all genes in the growth coupling design have been implemented. Metabolic cross-feeding experiments were used to examine the impact of complete removal of the fumarase hydratase reaction and revealed an unanticipated nutrient requirement, suggesting additional functions for this enzyme. While a complete implementation of the design was achieved, this study highlights the challenge of completely inactivating metabolic reactions encoded by under-characterized proteins, especially in the context of multi-gene edits.

X-ray Nanoimaging of a Heterogeneous Structural Phase Transition in V2O3.

Controlling the Mott transition through strain engineering is crucial for advancing the development of memristive and neuromorphic computing devices. Yet, Mott insulators are heterogeneous due to intrinsic phase boundaries and extrinsic defects, posing significant challenges to fully understanding the impact of microscopic distortions on the local Mott transition. Here, using a synchrotron-based scanning X-ray nanoprobe, we studied the real-space structural heterogeneity during the structural phase transition in a V2O3 thin film. Through temperature-dependent metal-insulator phase coexistence mapping, we report a variation in the local transition temperature up to 7 K across the film and nanoscale transition hysteresis. Furthermore, we reveal that the spatial heterogeneity of the transition is closely tied to the tilting of crystallographic planes. Our work highlights the impact of local heterogeneity on the Mott transition and lays the groundwork for future innovations in harnessing strain heterogeneity within Mott systems for the next-generation computational technologies.

Enhanced carrier mobility in strain-engineered PdAs2 monolayer boosted by suppressing interband scattering.

Strain engineering is an effective method to modulate the electronic properties of two-dimensional materials. In this study, we theoretically studied the carrier mobility of the PdAs2 monolayer under different biaxial tensile strains based on the state-of-the-art electron-phonon coupling theory. We observe that the carrier mobility is largely enhanced for both n-type and p-type PdAs2 monolayers. The electron mobility experiences a rapid increase under tensile strain over 2% and can reach 670 cm2 V-1 s-1 under 4% strain, which is higher than common 2D semiconductors. The rapid increase of electron mobility originates from the ordering change of the conduction bands and the suppressed interband scattering. Our study highlights the role of electron-phonon coupling in the electron transport and provides new insights into the optimization of carrier mobility.

Activating the Screened Thermoelectric and Photocatalytic Water-Splitting Potential in Janus Sn2XY (X ≠ Y = Te, Se, and S) Monolayers via Doping and Strain Engineering

Activating the Screened Thermoelectric and Photocatalytic Water-Splitting Potential in Janus Sn₂XY (X ≠ Y = Te, Se, and S) Monolayers via Doping and Strain Engineering

Modulation of the octahedral structure and potential superconductivity of La3Ni2O7 through strain engineering

Modulation of the octahedral structure and potential superconductivity of La3Ni2O7 through strain engineering

Cluster Engineering in Water Catalytic Reactions: Synthesis, Structure-Activity Relationship and Mechanism.

Four fundamental reactions are essential to harnessing energy from water sustainably: oxidation reduction reaction (ORR), oxygen reduction reaction (OER), hydrogen oxidation reaction (HOR), and hydrogen evolution reaction (HER). This review summarizes the research advancements in the electrocatalytic reaction of metal nanoclusters for water splitting. It covers various types of nanoclusters, particularly those at the size level, that enhance these catalytic reactions. The synthesis of cluster-based catalysts and the elucidation of the structure-activity relationships and reaction mechanisms are discussed. Emphasis is placed on utilizing atomically precise cluster materials and the interplay between the carrier and cluster in water catalysis, especially for applying catalytic engineering principles (such as synergy, coordination, heterointerface, and lattice strain engineering) to understand structure-activity relationships and catalytic mechanisms for cluster-based catalysts. Finally, the field of cluster water catalysis is summarized and prospected. We believe that developing cluster-based catalysts with high activity, excellent stability, and high selectivity will significantly promote the development of renewable energy conversion reactions.

Enhanced Cooperative Generalized Compressive Strain and Electronic Structure Engineering in W-Ni3N for Efficient Hydrazine Oxidation Facilitating H2 Production.

As promising bifunctional electrocatalysts, transition metal nitrides are expected to achieve an efficient hydrazine oxidation reaction (HzOR) by fine-tuning electronic structure via strain engineering, thereby facilitating hydrogen production. However, understanding the correlation between strain-induced atomic microenvironments and reactivity remains challenging. Herein, a generalized compressive strained W-Ni3N catalyst is developed to create a surface with enriched electronic states that optimize intermediate binding and activate both water and N2H4. Multi-dimensional characterizations reveal a nearly linear correlation between the hydrogen evolution reaction (HER) activity and the d-band center of W-Ni3N under strain state. Theoretically, compressive strain enhances the electron transfer capability at the surface, increasing donation into antibonding orbitals of adsorbed species, which accelerates the HER and HzOR. Leveraging both compressive strain and the modified electronic structure from W incorporation, the W-Ni3N catalysts demonstrate outstanding bifunctional performance, achieving overpotentials of 46mV for HER at 10mA cm-2 and 81mV for HzOR at 100mA cm-2. Furthermore, W-Ni3N catalyst achieves efficient overall hydrazine splitting at a low cell voltage of 0.185V for 50mA cm-2, maintaining stability for ≈450 h. This work provides new insights into the dual engineering of strain and electronic structure in the design of advanced catalysts.