Nanostructure Arrays Research Articles

Dynamic Hyperspectral Holography Enabled by Inverse-Designed Metasurfaces with Oblique Helicoidal Cholesterics.

Metasurfaces are flat arrays of nanostructures that allow exquisite control of phase and amplitude of incident light. Although metasurfaces offer new active element for both fundamental science and applications, the challenge still remains to overcome their low information capacity and passive nature. Here, by integrating an inverse-designed-metasurface with oblique helicoidal cholesteric liquid crystal (ChOH), simultaneous spatial and spectral tunable metasurfaces with a high information capacity for dynamic hyperspectral holography, are demonstrated. The inverse design facilitates a single-phase map encoding of ten independent holographic images at different wavelengths. ChOH provides precise spectral modulation with narrow bandwidth and wide tunable regime in response to programmed stimuli, thus enabling dynamic switching of the multicolor holography. The results provide simple and generalizable principles for the rational design of interactive metasurfaces that will find numerous applications, including security platform.

Adhesion measurement of living cells based on electrical impedance.

Cells adherence provides specific information about physiology and pathology, the adhesion measurement between living cells and nanostructures can be measured by atomic force microscopy, but this detection technique is difficult to operate and costly. The adhesion height and effective contact area between cells and substrates are also the key factors affecting measurement value of the overall impedance. These factors change with structural parameters of the substrates, so the adhesion measurement between living cells and substrate can be indirectly reflected by the impedance value. To establish a mapping relationship between the impedance measurement and the adhesion measurement of living cells. The possibility of dynamic measurement of adhesion is realized by this method, and the experimental process is simplified. Laser interference technology was used to prepare nanoarray structures with different periods on the surface of silicon wafers for cells culture. Under the same experimental conditions, the impedance of living cells on the substrates of different cycle sizes were measured. The adhesion between cells and different substrates were analyzed by measuring impedance after the interaction between cells and substrate. The adhesion of living cells on the substrates of different sizes be analyzed, and the mapping relationship between the impedance and the adhesion measurement was established. The results showed that, the larger the impedance value between cells and substrate, the larger the effective contact area and the smaller the gap between them. The difference of adhesion height and effective adhesion area between living cells and substrates were obtained. This paper, a new method to measure the adhesion properties of living cells is presented, which provides theoretical basis for the related research.

Multiscale modulation of ultra-small ruthenium anchored on bimetallic sulfides for seawater electrolysis at ampere-level current density

Developing efficient and stable electrocatalysts is the critical challenge for hydrogen evolution reaction (HER) from seawater electrolysis. The design of catalysts for seawater HER needs to consider not only high intrinsic activity determined by the electronic structure, but also favorable mass transfer at the catalyst's surface. Herein, a unique nanoarray hybrid heterojunction consisting of ultra-small Ru nanoparticle (NPs) decorated on the surface of NiMo bimetallic sulfides (NiMoSx) is proposed. This Ru/NiMoSx heterostructure delivers an ampere-level current density of 1.0 A cm−2 at an overpotential of only 208 mV in alkaline seawater, which is far superior to the performance of commercial Pt/C. In situ spectroscopy and electronic structural analysis demonstrate that the atom-level synergy between Ru NPs and NiMoSx heterostructure makes the electron transfer from Ru to Ni/Mo, weakening the interaction of Ru and H atom, eventually facilitating the H desorption. Also, the results of contact angle tests and simulation calculations reveal that the micro-level modulation of nanoarray structure favors the diffusion of electrolyte and bubble, ensuring rapid mass transfer and exposing multiple active sites. With the multiscale modulation including optimized electronic structure and fast mass transfer, both H2 generation and transportation for Ru/NiMoSx are all prompted, thus leading to outstanding seawater HER performance.

Theoretical exploration of photoemission characteristics of GaAs nanowire array cathode based on photon-enhanced thermionic emission

The theoretical photoemission models of single GaAs nanowire and nanowire array cathode based on photon-enhanced thermionic emission (PETE) mechanism are respectively developed by utilizing two-dimensional continuity equations. Based on the built models in this work, the effect of several key factors on the quantum efficiency are also discussed. Results show that GaAs nanowire cathode exhibits the superiority of photoemission performance compared with GaAs film cathode at the spectral range of 300∼600 nm. Besides, the optimal wire diameter of GaAs nanowire cathode is in the range of 340∼360 nm. In addition, the nanowire cathode with low electron affinity of 0.3 eV achieves PETE effect under low temperature of 400 K, which is conducive to improve the stability of cathode. Moreover, increasing the incident light angle or decreasing the array spacing provides an effective method of obtaining high quantum efficiency of nanowire array cathode. Furthermore, the numerical difference between quantum efficiency and effective quantum efficiency implies that the low collection efficiency of emitted electrons is the main issue that hinders the application of PETE cathodes of GaAs nanowire array. The proposed GaAs nanowire array model would provide theoretical guidance for optimum design of PETE cathodes with nanoarray structure.

Synthesis of flower-type nanorods with Zn-doped manganese vanadate (Mn(VO3)2) and carbon nanofibers (CNFs) for enhanced performance in battery-type supercapacitors

Among the various novel electrode materials prepared to enhance the electrochemical performance of supercapacitors, ordered nanoarray structures stand out as highly promising candidates for use as binder-free electrodes. In this study, flower type nanorods of zinc manganese vanadate (MnZn3(VO4)2) grown on 3-D nickel foam, with additional incorporation of Carbon nanofibers (CNFs)(MZVC) by using a one-step hydrothermal method. The nanostructured MZVC electrode exhibited a specific capacitance of 469 Fg−1 at a current density of 0.5 Ag−1, surpassing the specific capacitance values of the pristine electrodes (ZV-304 Fg−1, MV-263 Fg−1) and MZV − 333 Fg−1) at the same current density. Remarkably, the MZVC composite electrode exhibited an exceptional retention rate of approximately 82.6 % even after 5000 charge–discharge cycles. All of the fabricated electrodes underwent comprehensive characterization utilizing different analytical techniques to assess their structural, and surface morphological attributes. Further, Electrochemical behavior was assessed for ZV, MV, MZV, and MZVC nanostructures through cyclic voltammetry (CV), galvanostatic charge /discharge (GCD), and electrochemical impedance spectroscopy (EIS). This 3D porous flower-type electrode structure offers an abundance of active sites for electrochemical reactions, enables efficient electron and ion transport, and mitigates the aggregation of MZVC flower structures throughout prolonged cycling.

Probing Temperature-Induced Plasmonic Nonlinearity: Unveiling Opto-Thermal Effects on Light Absorption and Near-Field Enhancement.

Precise measurement and control of local heating in plasmonic nanostructures are vital for diverse nanophotonic devices. Despite significant efforts, challenges in understanding temperature-induced plasmonic nonlinearity persist, particularly in light absorption and near-field enhancement due to the absence of suitable measurement techniques. This study presents an approach allowing simultaneous measurements of light absorption and near-field enhancement through angle-resolved near-field scanning optical microscopy with iterative opto-thermal analysis. We revealed gold thin films exhibit sublinear nonlinearity in near-field enhancement due to nonlinear opto-thermal effects, while light absorption shows both sublinear and superlinear behaviors at varying thicknesses. These observations align with predictions from a simple harmonic oscillation model, in which changes in damping parameters affect light absorption and field enhancement differently. The sensitivity of our method was experimentally examined by measuring the opto-thermal responses of three-dimensional nanostructure arrays. Our findings have direct implications for advancing plasmonic applications, including photocatalysis, photovoltaics, photothermal effects, and surface-enhanced Raman spectroscopy.

The Role of ZO-2 in Modulating JAM-A and γ-Actin Junctional Recruitment, Apical Membrane and Tight Junction Tension, and Cell Response to Substrate Stiffness and Topography.

This work analyzes the role of the tight junction (TJ) protein ZO-2 on mechanosensation. We found that the lack of ZO-2 reduced apical membrane rigidity measured with atomic force microscopy, inhibited the association of γ-actin and JAM-A to the cell border, and instead facilitated p114RhoGEF and afadin accumulation at the junction, leading to an enhanced mechanical tension at the TJ measured by FRET, with a ZO-1 tension probe, and increased tricellular TJ tension. Simultaneously, adherens junction tension measured with an E-cadherin probe was unaltered. The stability of JAM-A and ZO-2 binding was assessed by a collaborative in silico study. The absence of ZO-2 also impacted the cell response to the substrate, as monolayers plated in 20 kPa hydrogels developed holes not seen in parental cultures and displayed a retarded elongation and formation of cell aggregates. The absence of ZO-2 was sufficient to induce YAP and Snail nuclear accumulation in cells cultured over glass, but when ZO-2 KD cells were plated in nanostructured ridge arrays, they displayed an increased abundance of nuclear Snail and conspicuous internalization of claudin-4. These results indicate that the absence of ZO-2 also impairs the response of cells to substrate stiffness and exacerbates transformation triggered by substrate topography.

Ordered FeCo2O4 & polypyrrole particles/branch nanotrees arrays grown on carbon fiber cloth substrate for energy storage applications

Supercapacitors are being utilized in energy storage devices with increasing interest a reason of their characteristics, which include high specific power, rapid charge and discharge rates, and long-term cycle stability. Most recently, research has concentrated on creating nanostructures to improve supercapacitors capacitance. The enhanced specific surface area of a material facilitates rapid diffusion of electrolyte ions; carbon fiber cloth (CFC) has been specifically utilized as a templates, leading to theoretical and practical advantages. In addition, the FeCo2O4 (FCO) and polypyrrole (PPy) to the CFC substrate is believed to be significant in enhancing the electrochemical behavior of supercapacitors. This study investigates the design approach of nanotree, configurations, and electrochemical characteristics of FCO-PPy on CFC for utilization in supercapacitors. The results of this research offer promising prospects for the advancement of future technologies to store energy. Porous FeCo2O4–polypyrrole (FCO-PPy) nanostructured arrays on CFC have been synthesis by a simple hydrothermal process with addition annealing process. The present research exhibits a unique nanostructure that exhibits exceptional electrochemical performance, characterized by a high capacitance and a desirable cycle life even under high rates of operation. The FCO-PPy nanowire arrays supported by CFC demonstrated a high specific capacitance of 1070 F g−1 at current densities of 2 A g−1 in a 2 M KOH aqueous solution when tested as an electrode in a system of supercapacitors. In addition, the FCO,CFC&PPy nanocomposite electrode shows excellent performance and long-term cyclic stability (90% capacitance retention after 10,000 cycles). The fabrication method presented here is cost-effective, facile, and scalable, which can open a new pathway for real device applications. Utilizing energy storage sustainability goods in business, adopting environmentally friendly chemicals, and being cost-conscious can considerably extend battery life. This includes breakthrough technology to mix modern materials, new electrode materials, new battery designs, and supercapacitors to revolutionize energy storage.

Helical Superstructures from the Hierarchical Self-Assembly of Coil-Coil Block Copolymer Guided by Side Chain Amyloid-β(17-19) LVF Peptide.

The rational design of precisely controlled hierarchical chiral nanostructures from synthetic polymers garnered inspiration from sophisticated biological materials. Since chiral peptide motifs induce helix formation in macromolecules, herein we report the synthesis of a novel type of hybrid polymer consisting of a β-sheet forming a LVF [L = leucine, V = valine, and F = phenylalanine] tripeptide pendant polymethacrylate block and a poly[poly(ethylene glycol) methyl ether methacrylate] (PPEGMA) block. The designed block copolymer self-organized into helical superstructures with a left-handed twisting sense, as visualized by field emission scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. This intriguing hierarchical self-assembly is driven by the minimalistic peptide motif that itself has a high propensity to adopt an antiparallel β-sheet conformation. We also report the generation of a diverse array of nanostructures, including spherical micelles, spindle micelles, rod-like micelles, vesicles, helical supramolecular fibers, and helical toroids via self-assembly of the designed block copolymer in tetrahydrofuran/water mixed solvents. To realize the observable helical superstructure, a twisted two-dimensional core-shell tape is proposed as a structure model in which the peptide segments form an antiparallel β-sheet with a polymer shell. The findings contribute to the advancement of a helical polymer or the superhelical self-assembly of polymers, paving the way for diverse applications in materials science and related fields.

Visible Meta-Displays for Anti-Counterfeiting with Printable Dielectric Metasurfaces.

Metasurfaces, 2D arrays of nanostructures, have gained significant attention in recent years due to their ability to manipulate light at the subwavelength scale. Their diverse applications range from advanced optical devices to sensing and imaging technologies. However, the mass production of dielectric metasurfaces with tailored properties for visible light has remained a challenge. Therefore, the demand for efficient and cost-effective fabrication methods for metasurfaces has driven the continuing development of various techniques. In this research article, a high-throughput production method is presented for multifunctional dielectric metasurfaces in the visible light range using one-step high-index TiO2-polymer composite (TPC) printing, which is a variant of nanoprinting lithography (NIL) for the direct replication of patterned multifunctional dielectric metasurfaces using a TPC material as the printing ink. The batch fabrication of dielectric metasurfaces is demonstrated with controlled geometry and excellent optical response, enabling high-performance light-matter interactions for potential applications of visiblemeta-displays.

The mechanism underlying asymmetric bending of lateral petals in Delphinium (Ranunculaceae)

During the process of flower opening, most petals move downward in the direction of the pedicel (i.e., epinastic movement). In most Delphinium flowers, however, their two lateral petals display a very peculiar movement, the mirrored helical rotation, which requires the twist of the petal stalk. However, in some lineages, their lateral petals also exhibit asymmetric bending that increases the degree of mirrored helical rotation, facilitating the formation of a 3D final shape. Notably, petal asymmetric bending is a novel trait that has not been noticed yet, so its morphological nature, developmental process, and molecular mechanisms remain largely unknown. Here, by using D.anthriscifolium as a model, we determined that petal asymmetric bending was caused by the localized expansion of cell width, accompanied by the specialized array of cell wall nano-structure, on the adaxial epidermis. Digital gene analyses, gene expression, and functional studies revealed that a class I homeodomain-leucine zipper family transcription factor gene, DeanLATE MERISTEM IDENTITY1 (DeanLMI1), contributes to petal asymmetric bending; knockdown of it led to the formation of explanate 2D petals. Specifically, DeanLMI1 promotes cell expansion in width and influences the arrangement of cell wall nano-structure on the localized adaxial epidermis. These results not only provide a comprehensive portrait of petal asymmetric bending for the first time but also shed some new insights into the mechanisms of flower opening and helical movement in plants.

Controllable Synthesis of Flower-like Hierarchical CuCo2S4 Nanostructure Arrays for High-Performance Hybrid Supercapacitors

Transition metal sulfides (TMSs) are considered as attractive materials in the areas of energy storage because of their unique redox properties, excellent electronic conductivity, as well as environmental friendliness. However, poor cyclic stability and limited electrochemical active sites hinder their further application. To address this issue, a flower-like hierarchical CuCo2S4 structure is constructed by a two-step hydrothermal method. In this nanostructure, CuCo2S4 grows outward to form a tightly bound hierarchical structure on the nickel foams (NFs). This oriented structure can provide more laminar gaps for electrolyte ion diffusion, exposing more reaction sites to increase the ion transport efficiency between the layers, reducing the ion transport resistance and improving the reaction kinetics. Thus, the CuCo2S4 electrode exhibits excellent energy storage performance, exhibiting a high specific capacity of 1415.6 F g−1 at 1 A g−1. After 10,000 cycles of 10 A g−1, it still has 91.9% of the initial performance. In addition, an asymmetrical supercapacitor (ASC) was constructed by choosing CuCo2S4 as the anode and RGO as the cathode, which has the maximum energy density (61.8 Wh Kg−1) at 812.1 W Kg−1 and significant cycling endurance (92.05% retention) at 10,000 turns. Briefly, the researchers successfully constructed an array of CuCo2S4 flower-like hierarchical nanostructures and confirmed their potential application in supercapacitors.

Damage Behavior with Atomic Force Microscopy on Anti-Bacterial Nanostructure Arrays

The atomic force microscope is a versatile tool for assessing the topography, friction, and roughness of a broad spectrum of surfaces, encompassing anti-bacterial nanostructure arrays. Measuring and comparing all these values with one instrument allows clear comparisons of many nanomechanical reactions and anomalies. Increasing nano-Newton-level forces through the cantilever tip allows for the testing and measuring of failure points, damage behavior, and functionality under unfavorable conditions. Subjecting a grade 5 titanium alloy to hydrothermally etched nanostructures while applying elevated cantilever tip forces resulted in the observation of irreversible damage through atomic force microscopy. Despite the damage, a rough and non-uniform morphology remained that may still allow it to perform in its intended application as an anti-bacterial implant surface. Utilizing an atomic force microscope enables the evaluation of these surfaces before their biomedical application.

Fabrication of silver nanostructure array patterns (SNAPs) on silicon wafer for highly sensitive and reliable SERS substrates

Metal nanostructure arrays with large amounts of nano-gaps are important for surface enhanced Raman scattering applications, though the fabrications of such nanostructures are difficult due to the complex and multiple synthetic steps. In this research, we report silver nanostructure array patterns (SNAPs) on silicon wafer, which is fabricated with semiconductor manufacturing technology, Cu2O electrochemistry deposition, and Ag In-situ oxidation–reduction growth. Benefiting from the dense and uniform distribution of Ag nanowires, the fabricated SNAPs demonstrate a very strong and uniform surface-enhanced Raman scattering (SERS) effect. The efficiency of SNAPs was investigated by using rhodamine 6G (R6G) dye as an analyte molecule. The results show that the minimum detectable concentration of R6G can reach as low as 10−11 M, and the Raman signals in the random region show good signal homogeneity with a low relative standard deviation (RSD) of 4.77 %. These results indicate that the SNAPs perform a great sensitivity and uniformity as a SERS substrate. Furthermore, we used the SNAPs substrate to detect antibiotic sulfadiazine. The main peaks in sulfadiazine Raman and vibration modes assignments were obtained and the quantitative analysis model was established by principal component analysis (PCA). The detection and application results of sulfadiazine indicate that the SNAPs substrate can be applied for trace detection of antibiotics. In addition, we have cited the application of the SNAPs substrate in anti-counterfeiting labels. These practical applications demonstrate that the fabricated SNAPs can potentially provide a way to develop low-cost SERS platforms for environmental detections, biomedicine analysis, and commodities anti-counterfeiting.

Capillary-Assisted Assembly of Soft Conductive Polymer Nanopillar/Tube Arrays and Applications.

Nanopillar/tube arrays have emerged as encouraging platforms, possessing remarkable advantages, including large specific areas and highly aligned orientations. Despite the progress of nano/microfabrication technologies, facile and controllable fabrication of conductive polymer nanopillar/tube arrays remains challenging. In this study, we demonstrate that the air-liquid interfacial self-assembly can be extended to obtain three-dimensional nanostructured arrays. A smart and novel method is proposed for preparing uniform conductive polymer nanopillar/tube arrays by a template-mediated interfacial synthesis approach. By utilizing capillary force, precise control processes of the nanostructure and patterned structure can be easily realized. Furthermore, a transfer strategy is devised, allowing for scalable fabrication and expansion of the applicability. Applications, including antibacterial surfaces and actuators, have been demonstrated. We extend the air-liquid interfacial synthesis technique as a powerful and universal strategy for producing ordered nanopillar/tube arrays and show the great potential of soft nanostructured arrays as advanced platforms in diverse applications.

Advanced Tuneable Micronanoplatforms for Sensitive and Selective Multiplexed Spectroscopic Sensing via Electro-Hydrodynamic Surface Molecular Lithography.

Micro- and nanopatterning of materials, one of the cornerstones of emerging technologies, has transformed research capabilities in lab-on-a-chip diagnostics. Herein, a micro- and nanolithographic method is developed, enabling structuring materials at the submicron scale, which can, in turn, accelerate the development of miniaturized platform technologies and biomedical sensors. Underpinning it is the advanced electro-hydrodynamic surface molecular lithography, via inducing interfacial instabilities produces micro- and nanostructured substrates, uniquely integrated with synthetic surface recognition. This approach enables the manufacture of design patterns with tuneable feature sizes, which are functionalized via synthetic nanochemistry for highly sensitive, selective, rapid molecular sensing. The development of a high-precision piezoelectric lithographic rig enables reproducible substrate fabrication with optimum signal enhancement optimized for functionalization with capture molecules on each micro- and nanostructured array. This facilitates spatial separation, which during the spectroscopic sensing, enables multiplexed measurement of target molecules, establishing the detection at minute concentrations. Subsequently, this nano-plasmonic lab-on-a-chip combined with the unconventional computational classification algorithm and surface enhanced Raman spectroscopy, aimed to address the challenges associated with timely point-of-care detection of disease-indicative biomarkers, is utilized in validation assay for multiplex detection of traumatic brain injury indicative glycan biomarkers, demonstrating straightforward and cost-effective micro- and nanoplatforms for accurate detection.

Ion Beam Etching of Anodic Aluminium Oxide Barrier Layer for Au Nanorod-Based Hyperbolic Metamaterials

Porous anodic aluminium oxide (AAO) is widely used as a template for the electrodeposition of ordered arrays of one-dimensional nanostructures. Prior to template filling, the barrier layer, which blocks the...

Abrasive-free chemical-mechanical planarization (CMP) of gold for thin film nano-patterning.

Despite high demand for gold film nanostructuring, patterning gold at the nanoscale still presents considerable challenges for current foundry-compatible processes. Here, we present a method based on abrasive-free chemical mechanical planarization (CMP) to planarize nanostructured gold surfaces with high selectivity against SiO2. The method is efficient in a damascene process and industry-compatible. Investigations into the material removal mechanism explore the effects of CMP parameters and show that the material removal rate is highly tunable with changes in slurry composition. Millimeter-scale arrays of gold nanostructures embedded in SiO2 were fabricated and the planarization dynamics were monitored over time, leading to the identification of distinct planarization phases and their correlation with the material removal mechanism. Finally, plasmonic cavities of gold nanostructure arrays over a gold mirror were fabricated. The cavities exhibited efficient plasmonic resonance in the visible range, aligning well with simulation results.

Fe/Au galvanic nanocells to generate self-sustained Fenton reactions without additives at neutral pH.

The generation of reactive oxygen species (ROS) via the Fenton reaction has received significant attention for widespread applications. This reaction can be triggered by zero-valent metal nanoparticles by converting externally added H2O2 into hydroxyl radicals (˙OH) in acidic media. To avoid the addition of external additives or energy supply, developing self-sustained catalytic systems enabling onsite production of H2O2 at a neutral pH is crucial. Here, we present novel galvanic nanocells (GNCs) based on metallic Fe/Au bilayers on arrays of nanoporous silica nanostructures for the generation of self-sustained Fenton reactions. These GNCs exploit the large electrochemical potential difference between the Fe and Au layers to enable direct H2O2 production and efficient release of Fe2+ in water at neutral pH, thereby triggering the Fenton reaction. Additionally, the GNCs promote Fe2+/Fe3+ circulation and minimize side reactions that passivate the iron surface to enhance their reactivity. The capability to directly trigger the Fenton reaction in water at pH 7 is demonstrated by the fast degradation and mineralization of organic pollutants, by using tiny amounts of catalyst. The self-generated H2O2 and its transformation into ˙OH in a neutral environment provide a promising route not only in environmental remediation but also to produce therapeutic ROS and address the limitations of Fenton catalytic nanostructures.

A scalable fabrication method for gold nanodisk-upconverting nanoparticle hybrid nanostructures.

Plasmonic nanostructures can be used to enhance the efficiency of upconversion nanoparticles (UCNPs) and enable new functionalities. However, the fabrication of these hybrid plasmon-UCNP nanostructures has traditionally relied on either wet chemistry or nanolithography routes that are difficult to control, scale up, or both. In this work, we present a scalable nanofabrication process, capable of producing a massive array of gold-UCNP hybrid nanostructures over a few mm2 area and with excellent uniformity in the photoluminescence intensity. This new approach combines the scalability of the bottom-up self-assembly method and the precision of the top-down nanolithography approach. It provides an efficient alternative route for the production of plasmonically enhanced UCNPs. A detailed discussion on the optimization of the UCNP self-assembly, the gold nanodisk lithography, and the nanopattern transfer processes is presented here. Additionally, we showcase the potential of this new approach for fabricating mechanical force sensors based on the selective plasmonic enhancement of the UCNP emission. This new approach holds great potential in facilitating the production of plasmonically enhanced UCNPs that can be deployed for both imaging and sensing applications.