Three-dimensional Array Research Articles

Au Nanoparticles Decorated CoP Nanowire Array: A Highly Sensitive, Anticorrosive, and Recyclable Surface-Enhanced Raman Scattering Substrate.

Metal-semiconductor composites are promising candidates for surface-enhanced Raman scattering (SERS) substrates, but their inert basal plane, poor active sites, and limited stability hamper their commercial prospects. Herein, we report a three-dimensional CoP nanowire array decorated with Au nanoparticles on carbon cloth (Au@CoP/CC) as a self-supporting flexible SERS substrate. The Au nanoparticles spontaneously grew on the surface of the CoP nanowire array to form efficient SERS hot spots by a redox reaction with HAuCl4 without any additional reducing agents. Such Au@CoP/CC substrate exhibited a limit of detection of 10-11 M using rhodamine 6G as a model dye with outstanding corrosion resistance ability even under extreme acid and alkali conditions, which is better than many recently reported Au-based SERS substrates. Finite-difference time-domain simulation results demonstrated that Au@CoP/CC can provide a high density of regions with intense local electric field enhancement. Moreover, Au@CoP/CC can degrade target organic dyes for the self-cleaning and reproduction of SERS-active substrates under visible light irradiation. This work provides a novel means of using the plasmonic metal-transition metal phosphide composites for high-performance SERS sensing and photodegradation.

Abruptly Autofocusing Vortex Beams for Rapid Controllable Femtosecond Two-Photon Polymerization.

Micro-fabrication based on structured-beam-assisted Two-Photon Polymerization (2 PP) provides a rapid and flexible method for the manufacture of microstructures with complex morphologies. The tunable Abruptly Autofocusing Vortex (AAFV) beams were designed theoretically and generated experimentally based on a single-phase-only Spatial Light Modulator (SLM). Their specific spatial intensity distributions were further utilized to assist the fabrication of a bowl-shaped Three-Dimensional (3D) micro-trap array via 2 PP with a one-step exposure technique. Finally, the fabricated microstructures act as a novel tool for the trapping and spatial positioning of micro-particles with different diameters, which shows potential applications in fiber optics and cell study.

A three-dimensional perspective of phosphorus retention across a field-buffer strip transition

Vegetated filter strips (VFS) act as buffer zones between fields and water bodies that are supposed to retain incoming runoff, sediment, and nutrients. The factors that govern nutrient retention and cycling in VFS are complex and act in all three dimensions. A key element that determines VFS effectivity is flow type, e.g., sheet vs. concentrated flow. These aspects are, however, often insufficiently accounted for in VFS research and design recommendations. In this study, we attempt to tackle these shortcomings by examining the nutrient distribution in detail at two field-VFS transitions, applying a three-dimensional sampling array together with extensive laboratory analyses. Concentrated runoff was the dominant type we found and we argue that flow convergence is the norm rather than the exception. Further complicating this issue is that entry locations of runoff may vary, calling for more sophisticated sampling designs. Overall trends were similar across the analyzed nutrient fractions (different K- and P-pools) and there were distinct trends of decreasing nutrients along the longitudinal (from the field to the VFS) and vertical planes. The horizontal plane (from outside to inside the area of concentrated flow) showed mostly inconclusive or U-shaped gradients. Both sites were similar and close to each other, nevertheless, there were significant differences that affected nutrient retention in the VFS which were linked to site-specific factors. The spatial extent (i.e., width) is often considered the main variable in VFS designs. However, other VFS traits such as vegetation type and structure, as well as external factors such as field topography and the severity of erosive events are equally important and should be attributed more significance.

Fabrication PANI/NiMn/NMP composite via electrodeposition with an activated process of converse voltage for energy storage

Growing active materials on conductive substrates and constructing three-dimensional structures are indispensable to prepare high energy density supercapacitors. Here, the composite material PANI/NiMn/NMP with a three-dimensional multi-layer structure and polyaniline as the interlayer was prepared on carbon cloth substrate by electrochemical deposition method. The interlayer of polyaniline strengthens the interface between the active material and the conductive substrate, which can effectively improve the cycle stability of the prepared integrated electrode. And the three-dimensional array structure provides abundant active sites and promotes the rapid transport of ions and electrons. NiMn-LDH that has been treated with electrochemical activation and the coating of NiMn phosphate with high conductivity can effectively improve the specific capacitance and cycling stability of the electrode material. The test results show that PANI/NiMn/NMP has high specific capacitance (2013 F g−1) and good cycling stability (retaining 87.38 % of the initial capacity after 5000 cycles). Furthermore, the asymmetric supercapacitor obtained by assembling PANI/NiMn/NMP and activated carbon has an energy density of 41.23 W h kg−1 at a power density of 673.2 W kg−1.

A modeling framework to quantify the intermediate layer impact in III–V//Si multijunction solar cells

Multijunction solar cells (MJSCs) are capable of converting sunlight to electricity more efficiently than single-junction solar cells. The intermediate scattering layers between the individual junctions contribute to high efficiency by impacting the generated currents, photon recycling (PR), as well as luminescent coupling (LC) in the device. The MJSC efficiency can be simulated using expressions that involve a simplified and idealized intermediate layer structure but cannot accurately reflect its actual performance. This work, however, aims to establish a systematic optical model for MJSCs with complicated intermediate layers. It begins with incorporating the LC and PR effects into the developed model, emphasizing requirements for the cut-off wavelength and long-wavelength transmission of the intermediate layer. Furthermore, a three-dimensional metallic nanocylinder array is designed as the intermediate layer to improve device performance. With the model, high-performance MJSCs can be designed and optimised by quantifying the impact of PR and LC on device parameters.

Two-dimensional lateral anatase-rutile TiO2 phase junctions with oxygen vacancies for robust photoelectrochemical water splitting

Exploiting the photoelectrode materials with broad solar light response, high-efficient separation of photogenerated charges and abundant active sites is extremely vital yet enormously challenging. Herein, an innovative two-dimensional (2D) lateral anatase-rutile TiO2 phase junctions with controllable oxygen vacancies perpendicularly aligned on Ti mesh is presented. Our experimental observations and theoretical calculations corroborate explicitly that the 2D lateral phase junctions together with three-dimensional arrays not only exhibit the high-efficient photogenerated charges separation guaranteed by the build-in electric field at the side-to-side interface, but also furnish enriching active sites. Moreover, the interfacial oxygen vacancies generate new defect energy levels and serve as electron donors, hence extending visible light response and further accelerating the separation and transfer of photogenerated charges. Profiting from these merits, the optimized photoelectrode yield a pronounced photocurrent density of 1.2 mA/cm2 at 1.23 V vs. RHE with Faradic efficiency of 100%, which is approximately 2.4 times larger than that of pristine 2D TiO2 nanosheets. Furthermore, the incident photon to current conversion efficiency (IPCE) of the optimized photoelectrode is also boosted within both ultraviolet and visible light regions. This research is envisioned deliver the new insight in developing the novel 2D lateral phase junctions for PEC applications.

Improving the GeAsSe Ovonic Threshold Switching Characteristics by Carbon Buffer Layers for Ultralow Leakage Current (∼0.4 nA) and Low Drift Characteristics

Volatile Ovonic threshold switching (OTS) selectors have been regarded as the critical component of highly integrated three-dimensional (3D) cross-point array nonvolatile memory systems. However, relatively high leakage current hinders the further reduction of power consumption in the crossbar array. In addition, the threshold voltage drift phenomenon hinders the improvement of device reliability. Utilizing the buffer layer can effectively reduce the interaction between electrodes and the active layer in the cross-point architecture. Here, it manifests that leakage current can be reduced to ∼0.4 nA with a 5 nm thick amorphous carbon layer as a buffer layer in the GeAsSe-based OTS device, where the carbon layer stabilizes the composition of GeAsSe during the electrical switching cycles. It is also found that the carbon layer leads to a lower threshold voltage drift (35.6 mv/dec) and excellent endurance (>109 cycles with ∼0.4 nA ON-state current). The conduction mechanism analysis demonstrates that the inhibition of the carbon layer on drift originates from the high barrier height from delocalized states transformed into localized states. This work clearly demonstrates the role of the carbon layer and facilitates future 3D crossbar-storage technology applications.

Application of a capacitively-loaded split-ring metamaterial lens in a 0.3 T magnetic resonance imaging system

In this work, it is demonstrated that metamaterial lenses can help to increase the signal-to-noise ratio of magnetic resonance imaging coils in low-field magnetic resonance imaging systems. In low-field magnetic resonance imaging systems, the dominant source of noise in the signal-to-noise ratio comes from the metallization of the coil and the noise sample or tissue is negligible, unlike high-field magnetic resonance imaging systems. A metamaterial lens consisting of a three-dimensional array of capacitively loaded split rings was fabricated and tested on a 0.3 T MRI system. The experiment was performed for a configuration in which the metamaterial lens is far enough from the coil so that the additional losses that can be introduced into the coil by the metamaterial lens are also negligible, as are the tissue losses.

Three-dimensional WO3 nanorod arrays on Si as photoanodes for efficient photoelectrochemical water splitting

Arrays of WO3–Si forest hierarchical structures have been successfully synthesized by growing WO3 nanorod on the surface of vertically aligned n-Si micropillar arrays using a chemical vapor deposition technique. The three-dimensional (3D) WO3–Si nanorod forest improves photoelectrochemical performances; it exhibits higher photocurrent density and a more negative onset potential of 0.5 V vs. reversible hydrogen electrode compared with the WO3 nanorod array on planar Si substrate. More importantly, this directly grown 3D hierarchical structure exhibits extraordinary stability for water oxidation with negligible losses of photoactivity for 24 h in a neutral pH solution. The enhanced photostability is attributed not only to the formation of O vacancies in WO3, which is resistive to photocorrosion but also the multiple internal reflection in 3D hierarchical structure. Our work demonstrates the importance of structural innovation in improving solar water efficiency.

Multifunctional MXene Conductive Zwitterionic Hydrogel for Flexible Wearable Sensors and Arrays.

Conductive hydrogels have good prospects in the fields of flexible electronic devices and artificial intelligence due to their biocompatibility, durability, and functional diversity. However, the process of hydrogel polymerization is time-consuming and energy-consuming, and freezing at zero temperature is inevitable, which seriously hinders its applications and working life. Herein, zwitterionic conductive hydrogels with self-adhesive and antifreeze properties were prepared in one minute by introducing two-dimensional (2D) MXene nanosheets into the autocatalytically enhanced system composed of tannic acid-modified cellulose nanofibers and zinc chloride. The system has strong environmental applicability (-60 to 40 °C), good stretchability (ductility ≈ 980%), durable adhesion (even after 30 days of exposure to air), and strong electrical conductivity (20 °C, 30 mS cm-1). By virtue of these advantages, the prepared zwitterionic hydrogels can be developed into flexible strain sensors to monitor large human movements and subtle physiological signals over a wide temperature range and to capture signals from handwriting and voice recognition. In addition, multiple flexible sensors can be assembled into a three-dimensional (3D) array, which can detect the magnitude and spatial distribution of strain or force. These results demonstrate that the prepared zwitterionic hydrogels have promising applications in the fields of medical monitoring and artificial intelligence.

A Three-Dimensional Neuromorphic Photosensor Array for Nonvolatile In-Sensor Computing.

In-sensor computing hardware based on emerging reconfigurable photosensors can effectively reduce redundant data and decrease power consumption, which can greatly promote the evolution of machine vision. However, because of the complex device structures and low integration abilities, the common architectures mainly lie in two dimensions, resulting in low time and area efficiencies. Here we propose a three-dimensional (3D) neuromorphic photosensor array for parallel in-sensor image processing. It is constructed on a vertical Graphite/CuInP2S6/Graphite photosensor unit, where the directional Cu+ ion migrations after voltage pulse programming enable a reconfigurable photovoltaic effect and an in-sensor computing capability. With a memristor-like device structure, van der Waals interfaces, and a high uniformity with a low crosstalk problem, a 10 × 10 array is fabricated for intelligent image recognition. Furthermore, using a vertically stacked 3D 3 × 3 × 3 array, we demonstrate an in-sensor convolution strategy with high time and area efficiencies.

Three-dimensional gradient index microlens arrays for light-field and holographic imaging and displays.

The geometric, intensity, and chromatic distortions that are a result of the limitations of the material and processes used to fabricate micro-optical lens arrays (MLAs) degrade the performance of light-field systems. To address these limitations, inkjet print additive manufacturing is used to fabricate planar gradient index (GRIN) lenslet arrays, in which volumetric refractive index profiles are used to embed optical functions that would otherwise require multiple homogeneous index MLA surfaces. By tailoring the optical ink feedstock refractive index spectra, independent control over dispersion is achieved, and achromatic performance is made possible. Digital manufacturing is shown to be beneficial for optimizing individual micro-optical channels in arrays wherein the shape, size, aspect ratio, focal length, and optical axis orientation of the lenslets vary as a function of the position within the optical field. Print fabrication also allows opaque inter-lens baffling and aperture stops that reduce inter-channel cross talk, improve resolution, and enhance contrast. These benefits are demonstrated in a light-field display testbed.

Three-dimensional porous AuNPs-decorated polyaniline array for ultrasensitive determination of trace Cd(II) and Pb(II) in drinking water

Herein, a three-dimensional porous nanomaterials AuNPs-decorated polyaniline nanowire arrays/carbon nanotube (Au-PANI-array@CNT) was constructed by modified dilute polymerization and redox reaction. The Au-PANI-array@CNT exhibited a larger specific surface area (50.03 m2 g−1) and abundant mesopores (average pore size: 19.6 nm), due to the vertical growth of PANI nanowire arrays on CNT. The Au-PANI-array@CNT composite with a three-dimensional interconnected porous structure exhibited abundant electroactive sites and high adsorption capacity, significantly enhancing the deposition and electrochemical reaction process of heavy metals. The AuNPs embedded on PANI nanowries can provide high catalytic activity and multidimensional electron transport channels, further improving the detection sensitivity. A sensing platform with ultra-high sensitivity (2091, 3890 μA μM−1 cm−2) and lower limit of detection (0.18, 0.15 nM) for Cd(II) and Pb(II) determination was developed based on the three-dimensional porous PANI composite. Furthermore, the sensing mechanism of Au-PANI-array@CNT with Cd(II) was explored by XPS and FTIR spectroscopy. The current response only decreased by 5% after being stored at room temperature for 2 months, indicating that the sensor has high reproducibility and stability. Finally, the analysis of drinking water samples verified the excellent practicability of the sensor for the simultaneous measurement of trace levels (nM) of Cd(II) and Pb(II).

Acoustic similarity of flight calls corresponds with the composition and structure of mixed-species flocks of migrating birds: evidence from a three-dimensional microphone array.

Animals that migrate in mixed-species groups may communicate with both conspecific and heterospecific individuals, providing a low-cost mechanism for navigation whenever individuals share similar migratory routes or destinations. Many migratory birds produce calls while flying, but the function of these calls, and the forces contributing to their evolution, are poorly known. We studied flight calls in mixed-species groups of wood warblers (Parulidae), a biodiverse group of migratory songbirds. We used a spatial approach to examine whether acoustic similarity of flight calls varies with group composition, recording flight calls of mixed-species flocks with a wireless microphone array and triangulating the positions of birds in three dimensions. We found that the acoustic similarity of flight calls was correlated with spatial proximity: birds with similar calls fly closer together during migration. We also found relationships between acoustic similarity, flock size and mixed-species flock diversity: birds with similar calls fly in smaller flocks and in flocks with lower species diversity. Our results support the idea that migrating birds use flight calls to maintain contact with acoustically similar individuals in mixed-species flocks, with communication transcending species boundaries. These results suggest that acoustically similar flight calls are used as cues of group assembly for migratory animals. This article is part of the theme issue 'Mixed-species groups and aggregations: shaping ecological and behavioural patterns and processes'.

A 3-D Metal-Printed Dual-Polarized Ridged Waveguide Slot Array Antenna for X-Band Applications

A compact three-dimensional (3-D) metal-printed ridged waveguide slot array antenna with wideband, dual linear polarization and low cross-polarization is presented for X-band applications. The proposed design achieves a compact structure due to the method of using a ridged waveguide (RWG). A vertically linear polarized (VP) array is realized through eight longitudinal shunt slots etched on the non-ridged broad wall of the RWG, while a horizontally linear polarized (HP) array is realized through eight V-shaped slots cut on the ridged broad wall of the RWG. To extend the operating bandwidth, each 1 × 8-element linear array is separated into two 1 × 4-element sub-arrays through a central feeding technique. The two sub-arrays of the VP array are excited with equal amplitude and are 180° out-of-phase through a T-junction power divider, which connects the coaxial feed and the radiated waveguide, while the two HP subarrays are directly excited by a coaxial feed with equal amplitude and remain in phase. The feed structure uses coaxial probes directly attached to the RWG to provide good mechanical stability and low voltage around the feed. An optimized 2 × 8-element dual-polarized array is fabricated using 3-D metal-printing technology for experimental verification. The measured −10 dB impedance bandwidth of the VP array is 1.2 GHz (12.2%) and, of the HP array, is 1.1 GHz (11.2%) with maximum gains of 14.6 and 15.5 dBi, respectively. There is good polarization purity over the entire operating bandwidth with a cross-polarization level better than −40 dB in the main beam direction. The isolation between two orthogonal polarized arrays is greater than 40 dB over the whole band.

Facile microwave plasma driven 3D-WSe2 2H-1T phase modulation for improving NO2 gas sensing performance

In recent years, transition metal dichalcogenides (TMDs) have been widely used for gas sensors. Here, three-dimensional (3D) WSe2 nanosheet arrays were surface treated by microwave plasma. Based on the original 3D structure, a 1T/2H hybrid phase structure was constructed by phase modulation, and Se vacancies were introduced to effectively improve its gas sensing performance. After only 60 s of treatment, the response (52.24 %), response/recovery time of the sample for 1 ppm NO2 were significantly improved with excellent stability and selectivity at room temperature. The intrinsic mechanism of its performance enhancement was elicited through various characterizations and molecular model construction. It is demonstrated that microwave plasma is a promising treatment method to improve the gas-sensitive performance of TMDs.

2D fin field-effect transistors integrated with epitaxial high-k gate oxide.

Precise integration of two-dimensional (2D) semiconductors and high-dielectric-constant (k) gate oxides into three-dimensional (3D) vertical-architecture arrays holds promise for developing ultrascaled transistors1-5, but has proved challenging. Here we report the epitaxial synthesis of vertically aligned arrays of 2D fin-oxide heterostructures, a new class of 3D architecture in which high-mobility 2D semiconductor fin Bi2O2Se and single-crystal high-k gate oxide Bi2SeO5 are epitaxially integrated. These 2D fin-oxide epitaxial heterostructures have atomically flat interfaces and ultrathin fin thickness down to one unit cell (1.2 nm), achieving wafer-scale, site-specific and high-density growth of mono-oriented arrays. The as-fabricated 2D fin field-effect transistors (FinFETs) based on Bi2O2Se/Bi2SeO5 epitaxial heterostructures exhibit high electron mobility (μ) up to 270 cm2 V-1 s-1, ultralow off-state current (IOFF) down to about 1 pA μm-1, high on/off current ratios (ION/IOFF) up to 108 and high on-state current (ION) up to 830 μA μm-1 at 400-nm channel length, which meet the low-power specifications projected by the International Roadmap for Devices and Systems (IRDS)6. The 2D fin-oxide epitaxial heterostructures open up new avenues for the further extension of Moore's law.

Syntheses, crystal structures and Hirshfeld surface analysis of three salts of 1-(4-nitro-phenyl)-piperazine.

The structures and Hirshfeld surface analysis of three salts of 1-(4-nitro-phenyl)-piperazine are discussed. In 4-(4-nitro-phen-yl)piperazin-1-ium salicylate (C10H14N3O2 +·C7H5O3 -), there are strong hydrogen bonds between cation and anion and the 4-nitro-phenyl substituent occupies an equatorial position in the piperazinium ring. The cation and anion are linked together by supra-molecular inter-actions [graph-set notation of hydrogen bonding (6) propagating in the a-axis direction]. Additionally, there is π-π stacking involving the salicylate anion and the piperazinium cation in adjacent asymmetric units as well as a C-H⋯π inter-action between a hydrogen atom on the piperazine ring and the phenyl ring within the salicyclate anion. In bis-[4-(4-nitro-phen-yl)piperazin-1-ium] bis-(4-fluoro-benzoate) trihydrate (2C10H14N3O2 +·2C7H4FO2 -·3H2O), there are two cations, two anions, and three water mol-ecules of solvation in the asymmetric unit, all linked by hydrogen bonds [graph-set notation of hydrogen bonding R 2 2(20) between adjacent cations and R 3 3(9) between a cation and its adjacent anion]. In the anion, the 4-nitro-phenyl ring occupies an axial substitution position in the piperazinium ring, which is relatively rare. Within the asymmetric unit, the phenyl groups in the cations show an offset π-π inter-action. Additionally, there is a C-H⋯π inter-action between a hydrogen atom on the phenyl ring within a cation and the phenyl ring within an anion. In 4-(4-nitro-phen-yl)piperazin-1-ium 3,5-di-nitro-benzoate (C10H14N3O2 +·C7H4N2O6 -), there is a strong N-H⋯O hydrogen bond linking the cation and anion and the 4-nitro-phenyl ring occupies an axial substitution position in the piperazinium ring, as seen in the previous structure. In the crystal, the cation and the anion form a complex three-dimensional hydrogen-bonded array involving R 2 2(8), R 4 4(12) and R 4 4(20) rings propogating in the a-axis direction. The nitro-phenyl group is disordered with occupancies of 0.806 (10) and 0.194 (10).

Analysis of Milk Microstructure Using Raman Hyperspectral Imaging

Optical spectroscopic analysis of the chemical composition of milk in its natural state is complicated by a complex colloidal structure, represented by differently sized fat and protein particles. The classical techniques of molecular spectroscopy in the visible, near-, and mid-infrared ranges carry only bulk chemical information about a sample, which usually undergoes a destructive preparation stage. The combination of Raman spectroscopy with confocal microscopy provides a unique opportunity to obtain a vibrational spectrum at any single point of the sample volume. In this study, scanning confocal Raman microscopy was applied for the first time to investigate the chemical microstructure of milk using samples of various compositions. The obtained hyperspectral images of selected planes in milk samples are represented by three-dimensional data arrays. Chemometric data analysis, in particular the method of multivariate curve resolution, has been used to extract the chemical information from complex partially overlaid spectral responses. The results obtained show the spatial distribution of the main chemical components, i.e., fat, protein, and lactose, in the milk samples under study using intuitive graphical maps. The proposed experimental and data analysis method can be used in an advanced chemical analysis of natural milk and products on its basis.

Construction of NiFe-Layered Double Hydroxides Arrays as Robust Electrocatalyst for Oxygen Evolution Reaction

Electrochemical water splitting is considered to be an important method for efficient hydrogen production to alleviate energy shortage and environmental pollution, but its development is currently limited by the slow oxygen evolution reaction (OER). To solve the sluggish reaction kinetics of OER, the focus is on the exploration of low-cost and efficient electrocatalysts, which is quite significant for the development of electrochemical water splitting. Herein, a NiFe layered double hydroxides (LDH) electrocatalyst (denoted as FNH) is achieved by a simple one-step hydrothermal method. The experimental results show that due to the synergistic interaction of introduced Fe species, the FNH possesses a special three-dimensional (3D) vertical nanosheet array structure, which results in efficient ion access. More importantly, the strong electronic interaction between Fe and Ni sites results in the optimized electronic structure of the Ni sites, which not only generates abundant Ni3+ sites as optimized active sites for OER, but also decrease the charge transfer resistance. Thus, the FNH catalyst exhibits an extraordinary overpotential of 386.8 mV to deliver 100 mA cm−2, showing better activity than that of RuO2, and satisfactory cycling stability after continuous operation for 28 h. Our work provides an easy-to-implement method to obtain high-efficiency OER electrocatalysts.