Three-dimensional Nanostructures Research Articles

Tailoring Defects in B, N-Codoped Carbon Nanowalls for Direct Electrochemical Oxidation of Glyphosate and its Metabolites.

Tailoring the defects in graphene and its related carbon allotropes has great potential to exploit their enhanced electrochemical properties for energy applications, environmental remediation, and sensing. Vertical graphene, also known as carbon nanowalls (CNWs), exhibits a large surface area, enhanced charge transfer capability, and high defect density, making it suitable for a wide range of emerging applications. However, precise control and tuning of the defect size, position, and density remain challenging; moreover, due to their characteristic labyrinthine morphology, conventional characterization techniques and widely accepted quality indicators fail or need to be reformulated. This study primarily focuses on examining the impact of boron heterodoping and argon plasma treatment on CNW structures, uncovering complex interplays between specific defect-induced three-dimensional nanostructures and electrochemical performance. Moreover, the study introduces the use of defect-rich CNWs as a label-free electrode for directly oxidizing glyphosate (GLY), a common herbicide, and its metabolites (sarcosine and aminomethylphosphonic acid) for the first time. Crucially, we discovered that the presence of specific boron bonds (BC and BN), coupled with the absence of Lewis-base functional groups such as pyridinic-N, is essential for the oxidation of these analytes. Notably, the D+D* second-order combinational Raman modes at ≈2570 cm-1 emerged as a reliable indicator of the analytes' affinity. Contrary to expectations, the electrochemically active surface area and the presence of oxygen-containing functional groups played a secondary role. Argon-plasma post-treatment was found to adversely affect both the morphology and surface chemistry of CNWs, leading to an increase in sp3-hybridized carbon, the introduction of oxygen, and alterations in the types of nitrogen functional groups. Simulations support that certain defects are functional for GLY rather than AMPA. Sarcosine oxidation is the least affected by defect type.

Assembly of ligation chain reaction and DNA triangular prism for miRNA diagnostics

Controllable assembly of DNA nanostructure provides a powerful way for quantitative analysis of various targets including nucleic acid molecules. In this study, we have designed detachable DNA nanostructures at electrochemical sensing interface and constructed a ligation chain reaction (LCR) strategy for amplified detection of miRNA. A three-dimensional DNA triangular prism nanostructure is fabricated to provide suitable molecule recognition environment, which can be further regenerated for additional tests via convenient pH adjustment. Target triggered LCR is highly efficient and specific towards target miRNA. Under optimal experimental conditions, this approach enables ultrasensitive exploration in a wide linear range with a single-base resolution. Moreover, it shows excellent performances for the analysis of cell samples and clinical serum samples.

Multiscale Lamellar Regulation of Three-Dimensional Graphene-like Nanostructures for Electromagnetic Interference Shielding and Thermal Management

Multiscale Lamellar Regulation of Three-Dimensional Graphene-like Nanostructures for Electromagnetic Interference Shielding and Thermal Management

Unlocking low-concentration NH3 gas sensing: An innovative MOF-derived In2O3/Co3O4 nanocomposite approach

Ammonia (NH3) is an odorless gas with a pungent smell that can affect health differently based on exposure and concentration. In this study, indium oxide was decorated with cobalt oxide (In2O3/Co3O4) flower-like nanocomposites (NFs) as gas-sensitive materials, revealing p-type semiconducting characteristics. The detection of ammonia (NH3) at low concentrations is a significant challenge for chemoresistive gas sensors. Porous Co3O4 nanoflowers were combined with In2O3 nanoparticles to form p-n heterojunctions for NH3 detection. The p-n heterojunction effect and the capability of the sub-valent band to hold vacancies within In2O3 nanoparticles effectively inhibit electron-hole recombination and extend the carrier lifetime. The In2O3/Co3O4 = 0.04 ratio-based gas sensor exhibited excellent selectivity, achieving a low detection limit of 500 ppb for NH3 at 250 °C. The rapid diffusion of gas within the porous Co3O4 NSs and In2O3 nanoparticles accounted for the high response (7.72) and fast response/recovery time (92 s/51 s) of the In2O3/Co3O4-based gas sensor to 10 ppm NH3. This study presents a method for fabricating NH3 gas sensors with trace-level detection capabilities by adjusting the band structure of nanoparticles and three-dimensional metal-oxide nanostructures.

Exploring the effect of morphology on electrochemical performance of nickel and cobalt metal-organic frameworks and their derivatives for supercapacitor and hydrogen evolution

This study explores the novel approach of investigating the use of binder-free nickel and cobalt metal-organic frameworks and their metal oxide derivatives in 1D, 2D, and 3D morphologies on Ni foam for applications in supercapacitors and hydrogen evolution. This research work involves changing parameters like precursor concentration, organic linkers, and reaction time, leading to the formation of stable one-, two-, and three-dimensional NiO and Co3O4 nanostructures. The morphologies of pristine MOFs and their corresponding oxides were comprehensively verified through FESEM analysis. Significantly, the materials with two-dimensional growth exhibited superior electrochemical performance in supercapacitors and good electrocatalytic performance in hydrogen evolution reaction when compared to their one-dimensional and three-dimensional counterparts. Among them, 2D NiO demonstrated exceptional performance as a supercapacitor electrode, with a specific capacity of 688.13 C g−1 (1376.26 F g−1) at 1 A g−1, surpassing 1D and 3D NiO nanostructures. It also demonstrated good stability by retaining 93.1 % of its initial capacity after 5000 cycles at 10 A g−1. The assembled asymmetric supercapacitor (ASC) achieved a high energy density of 65.27 Wh kg−1 at 375 W kg−1, maintaining 33.18 Wh kg−1 even at 7500 W kg−1. It also maintained 87.8 % retention of its initial capacity up to 5000 cycles at 10 A g−1. Furthermore, when tested for HER, all oxides exhibited better performances with specifically 2D NiO exhibiting good catalytic performance, reaching 10 mA cm−2 at a low overpotential of 129 mV (vs. RHE) and displaying remarkable stability over 24 h. This study upholds the superiority of two-dimensional sheet-like structures with interconnected network of nanoparticles in electrochemical and electrocatalytic performance compared to one-dimensional rod-like and three-dimensional pyramid-like structures.

Electrolyte solvents as architects: How solvents guide the spontaneous formation of 3D porous nanostructures in Alloy- and Conversion-type battery anodes

During battery cycling, fragmented anode materials following alloying, conversion, and conversion-alloying reactions spontaneously form three-dimensional (3D) porous nanostructures, influenced by the electrolyte solvent. While it is known that various solvents can enhance anode energy capacity, rate performance, and cycling stability by promoting this 3D structure, the specific solvent property responsible for this transformation was unclear. Our study investigates the role of 48 commercial solvents in Sn nanoparticle self-assembly, using both experimental and simulation methods. We discovered that solvent electrophilicity is crucial in initiating a solvation layer, guiding the development of the 3D nanostructure. This finding is significant in addressing anode fragmentation issues in alloying, conversion, and conversion-alloying processes. The resulting 3D nanostructures show enhanced mechanical and chemical resilience, offering a cost-effective and robust method to improve battery performance. Our research provides new insights into nanostructured anode design, paving the way for advanced battery technologies and enhancing our understanding of nanostructure formation in batteries.

Template free growth of cobalt catalyst-assisted horizontally aligned carbon nanorod arrays by MW-CVD utilizing mild oxidant in the plasma

The synthesis of three-dimensional carbon nanostructures without templates remains a substantial challenge. The present research enables skillfully generating horizontally-aligned carbon-nanorod-arrays (HA-CNRA), using microwave plasma-enhanced chemical vapor deposition (MW-PECVD) on quartz substrates coated with Co catalyst layers annealed at diverse temperatures. In this method, a gas mixture comprising C2H2, H2, and CO2 was used for the CNRA growth at a low substrate temperature of ∼300 °C. Electron-microscopy observation confirms the autonomous growth of individual hollow CNRs. A discernible peak at 1340 cm−1, G band peak at 1596 cm−1, and 2670 cm−1 peak (2D band) were observed, indicating a well-graphitized feature of the CNRs, which was further ascertained by the corresponding X-ray diffraction planes of (002) and (101) orientations. In the optimally grown film, a homogeneous array of nanorods with an average diameter of ∼450 nm was obtained. The C 1s spectra peaked at 284.6 eV confirming the presence of crystalline sp2-hybridized nanorods. The novelty of the work lies in enabling the Co catalyst-assisted template-free growth of HA-CNRA by low-temperature MW-CVD, utilizing the reactant atomic species like H and O from the (C2H2 + H2 + CO2)-plasma and preserving the growth continuity through a specific shadow masking configuration deployed atop the developing plane, thereby inducting a diffuse plasma on the substrate and restricting the direct collision of energetic particles with the developing network. Due to the adjustable size, shape, and advantageous architectural characteristics, horizontally-aligned CNRA manifests significant potential as electrode materials for energy storage applications, specifically in batteries and electrochemical capacitors.

Fabrication of SERS composite substrates using Ag nanotriangles-modified SiO2 photonic crystal and the application of malachite green detection

A novel surface-enhanced Raman scattering (SERS) composite substrates on the basis of Ag triangular nanoplates(Ag TNPs)-modified SiO2 photonic crystals (PC) is fabricated and applied to the SERS detection of malachite green (MG). It consists of uniformly arranged Ag TNP@SiO2, a new PC. Notably, Ag TNP are uniformly aligned on the SiO2 surface, forming a three-dimensional high-density hotspot nanostructure. With the tip “hot spots” of Ag TNPs, Bragg diffraction of SiO2 and coupling enhancement between Ag TNPs and SiO2, the SERS enhancement of this composite substrates was multiplied. The effect on the SERS of Ag TNP@SiO2 composite substrate was systematically optimized by tuning Ag TNP size, size of SiO2 microspheres, coverage of Ag TNPs on SiO2 and fabrication method of Ag TNPs and PC. Moreover, the uniform of SERS composite substrates and Raman signal was dramatically increased by the method of vertical deposition. Eventually, the SERS composite substrates were employed in MG detection. Its broad detection range of 1 pM–1 μM and low limit of detection (LOD) of 0.49 pM indicated acceptable sensitivity and repeatability. This work illustrates the promising applicability in food safety analysis based on SERS composite substrates composed by Ag TNP@SiO2 with numerous SERS enhancements and excellent stability.

Fabrication of Rhenium Disulfide/Mesoporous Silica Core-Shell Nanoparticles for a pH-Responsive Drug Release and Combined Chemo-Photothermal Therapy.

A stimuli-responsive drug delivery nanocarrier with a core-shell structure combining photothermal therapy and chemotherapy for killing cancer cells was constructed in this study. The multifunctional nanocarrier ReS2@mSiO2-RhB entails an ReS2 hierarchical nanosphere coated with a fluorescent mesoporous silica shell. The three-dimensional hierarchical ReS2 nanostructure is capable of effectively absorbing near-infrared (NIR) light and converting it into heat. These ReS2 nanospheres were generated by a hydrothermal synthesis process leading to the self-assembly of few-layered ReS2 nanosheets. The mesoporous silica shell was further coated on the surface of the ReS2 nanospheres through a surfactant-templating sol-gel approach to provide accessible mesopores for drug uploading. A fluorescent dye (Rhodamine B) was covalently attached to silica precursors and incorporated during synthesis in the mesoporous silica walls toward conferring imaging capability to the nanocarrier. Doxorubicin (DOX), a known cancer drug, was used in a proof-of-concept study to assess the material's ability to function as a drug delivery carrier. While the silica pores are not capped, the drug molecule loading and release take advantage of the pH-governed electrostatic interactions between the drug and silica wall. The ReS2@mSiO2-RhB enabled a drug loading content as high as 19.83 mg/g doxorubicin. The ReS2@mSiO2-RhB-DOX nanocarrier's cumulative drug release rate at pH values that simulate physiological conditions showed significant pH responsiveness, reaching 59.8% at pH 6.8 and 98.5% and pH 5.5. The in vitro testing using HeLa cervical cancer cells proved that ReS2@mSiO2-RhB-DOX has a strong cancer eradication ability upon irradiation with an NIR laser owing to the combined drug delivery and photothermal effect. The results highlight the potential of ReS2@mSiO2-RhB nanoparticles for combined cancer therapy in the future.

Molecular insights into strengthening of biomineral apatite with carbon nanofillers: A simulation study

Biomineral apatite (Ap) has been widely utilized in clinical bone graft procedures for over 25 years. However, its lower tensile strength and fracture toughness compared to natural bone limit its application in large load-bearing systems. This approach aims to enhance the mechanical performance of Ap while preserving its bioactivity, thereby expanding its potential clinical applications. In this study, the creation and processing of carbon nanofiller-based Ap nanocomposites, including pristine and vacancy-defective carbon nanofillers, are investigated using molecular dynamics simulations. The mechanical behaviour of Ap nanocomposites reinforced with three types of carbon nanofillers (CNF) is examined: (i) three-dimensional metallic carbon nanostructure with interlocking hexagons T6B (beam-like), (ii) carbon nanotubes (CNT), and (iii) three-dimensional metallic carbon nanostructure with interlocking hexagons T6P (plate-like). The analysis encompasses detailing the methodology utilized for modelling the equilibrated structures of CNF/Ap nanocomposites, along with the characterization of their elastic parameters. Computational findings reveal the significant impact of CNT chirality, Aspect Ratio (AR) of T6B and orientation of T6P on the mechanical properties of the nanocomposites and observed inclusion of CNF enhances the mechanical properties compared with those of pure Ap. The findings indicate that the lower diameter CNT and smaller cross-sectional area of T6B exhibit higher tensile strength compared to the larger CNT diameter and larger cross-sectional area of T6B of the same length. Further, the analysis highlights the substantial influence of vacancy defects concentration on CNF on the mechanical behaviour of nanocomposites, with an increase in defects correlating to a decrease in the mechanical strength of both CNF and CNF-based nanocomposites.

Synergistic enhancement of wearable biosensor through Pt single-atom catalyst for sweat analysis

Real-time monitoring of biological markers in sweat is a valuable tool for health assessment. In this study, we have developed an innovative wearable biosensor for precise analysis of glucose in sweat during physical activities. The sensor is based on a single-atom catalyst of platinum (Pt) uniformly dispersed on tricobalt tetroxide (Co3O4) nanorods and reduced graphene oxide (rGO), featuring a unique three-dimensional nanostructure and excellent glucose electrocatalytic performance with a wide detection range of 1–800 μM. Additionally, density functional theory calculations have revealed the synergetic role of Pt active sites in the Pt single-atom catalyst (Co3O4/rGO/Pt) in glucose adsorption and electron transfer, thereby enhancing sensor performance. To enable application in wearable devices, we designed an S-shaped microfluidic chip and a point-of-care testing (POCT) device, both of which were validated for effectiveness through actual use by volunteers. This research provides valuable insights and innovative approaches for analyzing sweat glucose using wearable devices, contributing to the advancement of personalized healthcare.

A Rapid Self-Assembling Peptide Hydrogel for Delivery of TFF3 to Promote Gastric Mucosal Injury Repair.

Self-assembled peptide-based nanobiomaterials exhibit promising prospects for drug delivery applications owing to their commendable biocompatibility and biodegradability, facile tissue uptake and utilization, and minimal or negligible unexpected toxicity. TFF3 is an active peptide autonomously secreted by gastric mucosal cells, possessing multiple biological functions. It acts on the surface of the gastric mucosa, facilitating the repair process of gastric mucosal damage. However, when used as a drug, TFF3 faces significant challenges, including short retention time in the gastric mucosal cavity and deactivation due to degradation by stomach acid. In response to this challenge, we developed a self-assembled short peptide hydrogel, Rqdl10, designed as a delivery vehicle for TFF3. Our investigation encompasses an assessment of its properties, biocompatibility, controlled release of TFF3, and the mechanism underlying the promotion of gastric mucosal injury repair. Congo red/aniline blue staining revealed that Rqdl10 promptly self-assembled in PBS, forming hydrogels. Circular dichroism spectra indicated the presence of a stable β-sheet secondary structure in the Rqdl10 hydrogel. Cryo-scanning electron microscopy and atomic force microscopy observations demonstrated that the Rqdl10 formed vesicle-like structures in the PBS, which were interconnected to construct a three-dimensional nanostructure. Moreover, the Rqdl10 hydrogel exhibited outstanding biocompatibility and could sustainably and slowly release TFF3. The utilization of the Rqdl10 hydrogel as a carrier for TFF3 substantially augmented its proliferative and migratory capabilities, while concurrently bolstering its anti-inflammatory and anti-apoptotic attributes following gastric mucosal injury. Our findings underscore the immense potential of the self-assembled peptide hydrogel Rqdl10 for biomedical applications, promising significant contributions to healthcare science.

Low-Temperature Deposition of Diamond Films by MPCVD with Graphite Paste Additive

Modern integrated circuits (ICs) take advantage of three-dimensional (3D) nanostructures in devices and interconnects to achieve high-speed and ultra-low-power performance. The choice of electrical insulation materials with excellent dielectric strength, electrical resistivity, strong mechanical strength, and high thermal conductivity becomes critical. Diamond possesses these properties and is recently recognized as a promising dielectric material for the fabrication of advanced ICs, which are sensitive to detrimental high-temperature processes. Therefore, a high-rate low-temperature deposition technique for large-grain, high-quality diamond films of the thickness of a few tens to a few hundred nanometers is desirable. The diamond growth rate by microwave plasma chemical vapor deposition (MPCVD) decreases rapidly with lowering substrate temperature. In addition, the thermal conductivity of non-diamond carbon is much lower than that of diamond. Furthermore, a small-grain diamond film suffers from poor thermal conductivity due to frequent phonon scattering at grain boundaries. This paper reports a novel MPCVD process aiming at high growth rate, large grain size, and high sp3/sp2 ratio for diamond films deposited on silicon. Graphite paste containing nanoscale graphite and oxy-hydrocarbon binder and solvent vaporizes and mixes with gas feeds of hydrogen, methane, and carbon dioxide to form plasma. Rapid diamond growth of diamond seeds at 450 °C by the plasma results in large-grained diamond films on silicon at a high deposition rate of 200 nm/h.

Facile synthesis of Au–TiO2/Bacterial cellulose aerogel nanocomposites with enhanced photocatalytic degradation of methylene blue under UV irradiation

The Au–TiO2/Bacterial cellulose aerogel nanocomposites (Au–TiO2/BC NCs) with remarkable photocatalytic properties and designed to solve agglomeration and reusability challenges in wastewater treatment have been successfully synthesized. The integration of gold nanoparticles (Au NPs) with TiO2, in conjunction with bacterial cellulose (BC) serving as a three-dimensional nanostructure, resulted in the formation of Au–TiO2/BC NCs through mechanical compositing, a confirmation obtained through various characterization techniques including XRD, SEM, SEM-EDS, TEM, TEM-EDS, BET, XPS, FT-IR, Spectrofluorometer, Raman, and UV–vis spectroscopy. The combination of Au–TiO2 nanoparticles with BC showcased homogeneous coverage over BC nanostructures, attributed to BC's unique properties, particularly its surface hydroxyl groups that prevent TiO2 agglomeration, along with uniform distribution of Au nanoparticles on TiO2 layers. Photocatalytic activity, assessed through methylene blue (MB) degradation under both UV and direct sunlight irradiation, demonstrated significantly improved efficiency with AuNPs, achieving approximately 90% degradation in the Au–TiO2/BC NCs under UV irradiation. The synthesized NCs exhibited stability with a slight performance reduction after cyclic tests, indicating potential for wastewater treatment applications under diverse light conditions. The integration of Au NPs onto TiO2 surfaces amplified light-induced reactions, addressing critical challenges in environmental remediation, particularly in the degradation of persistent environmental pollutants. This study offers valuable insights, positioning Au–TiO2/BC NCs as promising candidates for sustainable environmental remediation, emphasizing reusability, enhanced photocatalytic performance, and a straightforward synthesis process under both UV and direct sunlight irradiation.

Large-scale SU-8 Micro-Pole-Arrays decorated with Hierarchical Metal-Dielectric-Metal nanostructures as sensitive 3D SERS substrates

Dielectric layer-mediated surface-enhanced Raman scattering (SERS) substrates are currently explored for ultrasensitive detection and expected to provide uniform SERS response by the virtue of three-dimensional micro-nanostructures, dielectric layer, and plasmonic metal nanostructures. For this purpose, the present work reports on the development of the metal-dielectric-metal (MDM) three-dimensional (3D) micro-pole-arrays structure based on SU-8 colloid lithography. By utilizing the large-scale periodic arrangement characteristics of SU-8 colloidal lithography, along with the hot spot effect created by the nano-gap between MDM, we successfully prepared an array of SERS substrates that exhibit both periodicity and multi-dimensional plasmonic coupling effect. Compared to a single metal nanoparticle substrate, the SERS activity of the substrate is significantly enhanced, and the substrate has trace detection ability (LOD of detection of 10−12 mol/L for R6G). The enhancement factor (EF) is 5.72 × 107. Periodicity ensures that the prepared substrate has good reproducibility (RSD < 8 %) and stability. Furthermore, the substrate modified with HS-β-CD demonstrated potential for rapid trace SERS detection of polychlorinated biphenyls (PCB-77) (LOD of 10−8 mol/L for PCB-77). The results indicate that the proposed substrate has the potential for application in the preparation of SERS sensors with high sensitivity and uniformity.

Three-dimensional nanostructures of crosslinked aramid nanofibers with exceptional mechanical and thermal insulation characteristics

Despite the remarkable attributes of aramid nanofibers, which include a high aspect ratio, elevated strength and modulus, as well as exceptional chemical and thermal stabilities, their utilization in three-dimensional porous nanostructures remains constrained due to the inherent challenge of agglomeration between adjacent fibers. This study presents a novel approach involving citric acid-assisted crosslinking to mitigate aramid nanofiber agglomeration. By facilitating the formation of covalent bonds between aramid nanofibers and citric acid, this method leads to the development of a three-dimensional open-porous structure. The chemically crosslinked aramid nanofibers/citric acid composite demonstrated notable enhancements in physical, mechanical, and thermal insulation properties, including an ultra-low density of 8.7 mg cm−3, exceptional compressive and tensile strengths at 3.04 MPa and 287 kPa, respectively, and a low thermal conductivity of 40 mW m−1 K−1. These advancements can be attributed to the preservation of the porous structure achieved through established covalent bonds. These findings carry significant implications for unlocking the potential of aramid nanofibers, particularly in advancing fields like thermal maintenance, insulation, construction of ultra-light structures, and the mitigation of vibration or impact energy in demanding environments.

Achieving high selectivity and activity of CO2 electroreduction to formate by in-situ synthesis of single atom Pb doped Cu catalysts

Exploring highly selective and stable electrocatalysts is of great significance for the electrochemical conversion of CO2 into fuel. Herein, a three-dimensional (3D) nanostructure catalyst was developed by doping Pb single-atom (PbSA) in-situ on carbon paper (PbSA100-Cu/CP) through a low-energy and economical method. The designed catalyst exhibited abundant active sites and was beneficial to CO2 adsorption, activation, and subsequent conversion to fuel. Interestingly, PbSA100-Cu/CP showed a prominent Faraday efficiency (FE) of 97 % at –0.9 V versus reversible hydrogen electrode (vs. RHE) and a high partial current density of 27.9 mA·cm−2 for formate. Also, the catalyst remained significantly stable for 60 h during the durability test. The reaction mechanism was investigated by density functional theory (DFT), demonstrating that the doping PbSA induced the electrons redistribution, promoted the formate generation, reduced the rate-determining step (RDS) energy barrier, and inhibited the hydrogen evolution reaction. The study aims to provide a new strategy for developing of single-atom catalysts with high selectivity and stability, which will help reduce environmental pressure and alleviate energy problems.

Accelerating water dissociation at hierarchical nanostructured electrocatalyst for efficient hydrogen evolution

The sluggish kinetics of the water electrolysis reaction is a key issue for hydrogen production, so the rational design of a high-efficiency hydrogen evolution reaction (HER) electrocatalyst with various structures has attracted extensive attention. Herein, a coaxial hierarchical three-dimensional (3D) nanostructure, Pt@Mo–S–Ni-CNTs, was prepared. In this nanostructure, carbon nanotubes (CNTs) as the core, Mo–S–Ni ultrathin nanosheets as shells, and ultrasmall metal nanoparticles (NPs) were grown uniformly on the surface of Mo–S–Ni nanosheets (NSs). At a current density of 10 mA m−2, the catalyst under investigation has remarkable hydrogen evolution reaction (HER) activity under acidic conditions. The overpotential (η10) is measured to be 61.2 mV, while the Tafel slope is determined to be 40.2 mV dec−1. Meanwhile, in an alkaline medium, η10 is 80.5 mV and the Tafel slope is 52.3 mV dec−1. It also shows great mass activities of 1.32 A mg−1 and 1.86 A mg−1, which are higher than those of commercial Pt/C HER catalysts. Impressively, the excellent HER activity and durability of Pt@Mo–S–Ni-CNTs are mainly attributed to the close binding effects among Pt, MoS2, and NiS. Theoretical simulations show that the MoS2/NiS interfaces facilitate H2O dissociation and that Platinum (Pt) enhances the absorption of hydrogen atoms (H) and increases the charge transfer kinetics of the Mo–S–Ni, thus significantly improving the HER activity. This work highlights the importance of engineering interface nanosheets based on transition-metal dichalcogenides for enhanced HER performance.

Crystal plasticity simulations reveal cooperative plasticity mechanisms leading to enhanced strength and toughness in gradient nanostructured metals

Heterogeneous deformation is thought to provide the strengthening in gradient nanostructured metals, but the underlying plasticity mechanisms and optimal gradient structures for attaining improved mechanical performance remain elusive. Through crystal plasticity simulations of three-dimensional heterogeneous nanostructures, we reveal the heterogeneous-deformation-induced plasticity mechanisms which evoke increased flow strength and strain hardening. We have developed a synthetic microstructure generation algorithm which replicates both the microstructural features and external geometry of experimentally characterized samples—providing a direct comparison between the mechanical response recorded in simulations and experiments. Aligning well with experiments, the simulations show synergistically enhanced mechanical properties. High strain hardening rates directly correlate to large stress gradients that emerge due to heterogeneous deformation. Samples with smooth grain size gradients exhibit the most extreme stress gradients and correspondingly higher strain hardening rates. Large increases in dislocation density—especially within larger grains—and high intra- and inter-granular crystal rotation are plasticity mechanisms common to samples which exhibit high mechanical performance. Although the nanostructural gradients have pronounced influence over the mechanical performance, samples with the same grain size and dislocation density gradients exhibit varied mechanical properties. We show that the distribution of initial grain orientations and the microstructural constraints placed on larger grains also influence the active plasticity mechanisms providing improved mechanical properties.

Direct-write 3D printing of plasmonic nanohelicoids by circularly polarized light

Chiral plasmonic surfaces with 3D "forests" from nanohelicoids should provide strong optical rotation due to alignment of helical axis with propagation vector of photons. However, such three-dimensional nanostructures also demand multi-step nanofabrication, which is incompatible with many substrates. Large-scale photonic patterns on polymeric and flexible substrates remain unattainable. Here, we demonstrate the substrate-tolerant direct-write printing and patterning of silver nanohelicoids with out-of-plane 3D orientation using circularly polarized light. Centimeter-scale chiral plasmonic surfaces can be produced within minutes using inexpensive medium-power lasers. The growth of nanohelicoids is driven by the symmetry-broken site-selective deposition and self-assembly of the silver nanoparticles (NPs). The ellipticity and wavelength of the incident photons control the local handedness and size of the printed nanohelicoids, which enables on-the-fly modulation of nanohelicoid chirality during direct writing and simple pathways to complex multifunctional metasurfaces. Processing simplicity, high polarization rotation, and fine spatial resolution of the light-driven printing of stand-up helicoids provide a rapid pathway to chiral plasmonic surfaces, accelerating the development of chiral photonics for health and information technologies.