Multilayer Nanostructures Research Articles

Design of Ni(OH)2/M-MMT Nanocomposite With Higher Charge Transport as a High Capacity Supercapacitor.

Nano-petal nickel hydroxide was prepared on multilayered modified montmorillonite (M-MMT) using one-step hydrothermal method for the first time. This nano-petal multilayered nanostructure dominated the ion diffusion path to be shorted and the higher charge transport ability, which caused the higher specific capacitance. The results showed that in the three-electrode system, the specific capacitance of the nanocomposite with 4% M-MMT reached 1068 F/g at 1 A/g and the capacity retention rate was 70.2% after 1,000 cycles at 10 A/g, which was much higher than that of pure Ni(OH)2 (824 F/g at 1 A/g), indicating that the Ni(OH)2/M-MMT nanocomposite would be a new type of environmentally friendly energy storage supercapacitor.

Multilayered Mesoporous Composite Nanostructures for Highly Sensitive Label-Free Quantification of Cardiac Troponin-I.

Cardiac troponin-I (cTnI) is a well-known biomarker for the diagnosis and control of acute myocardial infarction in clinical practice. To improve the accuracy and reliability of cTnI electrochemical immunosensors, we propose a multilayer nanostructure consisting of Fe3O4-COOH labeled anti-cTnI monoclonal antibody (Fe3O4-COOH-Ab1) and anti-cTnI polyclonal antibody (Ab2) conjugated on Au-Ag nanoparticles (NPs) decorated on a metal–organic framework (Au-Ag@ZIF-67-Ab2). In this design, Fe3O4-COOH was used for separation of cTnI in specimens and signal amplification, hierarchical porous ZIF-67 extremely enhanced the specific surface area, and Au-Ag NPs synergically promoted the conductivity and sensitivity. They were additionally employed as an immobilization platform to enhance antibody loading. Electron microscopy images indicated that Ag-Au NPs with an average diameter of 1.9 ± 0.5 nm were uniformly decorated on plate-like ZIF-67 particles (with average size of 690 nm) without any agglomeration. Several electrochemical assays were implemented to precisely evaluate the immunosensor performance. The square wave voltammetry technique exhibited the best performance with a sensitivity of 0.98 mA mL cm−2 ng−1 and a detection limit of 0.047 pg mL−1 in the linear range of 0.04 to 8 ng mL−1.

Machine Learning Methods and Sustainable Development: Metal Oxides and Multilayer Metal Oxides

The development of nanotechnologies and new methods of machine learning are responsible for the significant attention and demand for metal oxides and multilayer metal-oxide nanostructures [...]

Investigation of Interfacial Microstructures of TiN/AlN Multilayers by Neutron Reflectometry

Three alternate TiN/AlN nanostructured multilayers with the TiN layer thicknesses of 60, 70, and 120 Å and the AlN layer thickness of 10 Å were fabricated using dc reactive magnetron sputtering. Microstructural characterizations of the three nano-scale films were performed using nonpolarized specular neutron reflectometry. The results showed that the three TiN/AlN multilayer thin films were typical superlattice films and the thicknesses of the TiN layer and AlN layer in the multilayers were consistent with the design thickness nearly. The interface roughness was asymmetric in all the samples. The interface of AlN growing on TiN was much sharper than that of TiN growing on AlN and the latter was the diffusion interface in the TiN/AlN multilayer films.

High-loaded nanobelt-array/nanobelt-microsphere multilayer Li4Ti5O12 self-supported on Ti foils for high-performance lithium ion battery

A high-loaded porous nanobelt-constructed multilayer hierarchical Li4Ti5O12 nanostructure (NBMH-LTO) is prepared via a hydrothermal process with the presence of NaF. This novel NBMH-LTO contains a nanobelt array layer directly grown on the Ti substrate and upper hollow microsphere-layers consisting of nanobelts. The self-standing Li4Ti5O12 nanobelts on conductive Ti foil can be directly used as anode in flexible and foldable lithium ion batteries without using conductive additives or binders. Furthermore, N-doped NBMH-LTO (NBMHNLTO) electrode is successfully obtained via a simple vapor-solid reaction process between NBMH-LTO and NH3, and it exhibits a high areal capacity of 0.71 mAh cm−2 at 0.1 mA cm−2 and excellent rate/cyclic performance. Additionally, the NBMHNLTO electrode also displays excellent performance at low temperature, after 100 cycles at -20 °C (1 mA cm−2), the capacity retention rate can reach to 98.6%. The enhanced performance of NBMHNLTO can be attributed to its high active materials load benefited from the new synthesis strategy, good electronic connection profited from the unique 3D network of nanbelts, and the further improved electron conductivity due to the presence of Ti3+in nanobelts.

Synthesis and characterization of some C-Ti based multilayer and composite nanostructures

Carbon-Titanium multilayer and composite thin films were obtained by Thermionic Vacuum Arc (TVA) method. The nanostructured films consisted by a carbon base layer and seven alternatively Titanium and Carbon layers were deposed on Silicon substrate. As well, to give C-Ti multilayer films with different percentages in Ti and C of layers, a thick Carbon base layer was deposed on Si substrate, and then seven Ti-C layers. In order to achieve the successively layers with C, and Ti different percentages, were adjusted the discharge parameters of C and Ti plasma sources to obtain the desired composition of layers. By changing of substrate temperature, and on the other hand the bias potential up to –700V, different batches of samples were obtained. Characterization of structural properties of films was achieved by Grazing Incidence X-ray Diffraction (GIXRD) and Electron Microscopy technique (TEM). The measurements show that increase of the substrate temperature reveal the changes in TixCy lattice parameters. The tribological measurements were performed using a ball-on-disk system with normal forces of 0.5, 1, 2, 3N respectively and a Bruker Hystrion TI 980 TriboIndenter. Was found that the coefficient of friction depends on the synthesis temperature, bias voltage and also by the C content, Ti content and amount of TiC nanocrystallites. To characterize the electrical conductive properties, the electrical surface resistance versus temperature have been measured, and then the electrical conductivity is calculated. Using the Wiedeman-Frantz law was obtained the thermal conductivity.

Supercapacitor Based on Nanostructured Multilayer Films Consisting of Polyelectrolyte/Graphene Oxide‐MnO2‐ZnO for Energy Storage Applications

The development of new technologies has increased the demand for energy storage devices with high performance. In this sense, supercapacitors appear as a prominent alternative due to their high power density, fast charge–discharge time, environment friendly, and long‐term cycle stability. Carbon materials and transition metal oxides have been reported as attractive materials to achieve supercapacitors with enhanced properties. This study investigates nanostructured films, using the layer‐by‐layer (LbL) method, consisting of MnO2‐ZnO nanostructures embedded into reduced graphene oxide (rGO) and combined with polyallylamine hydrochloride (PAH) polyelectrolyte for supercapacitor applications. The film morphology and the incorporation of MnO2‐ZnO nanostructures in rGO layers are analyzed by scanning electron microscopy images. The electrochemical properties are evaluated by cyclic voltammetry and galvanostatic charge–discharge measurements. A high capacitance is reached for a 20‐bilayer PAH/rGO‐MnO2‐ZnO LbL film at a 1 mV s−1 and 1.15 A g−1 with values of 1650 F g−1 and 26 mF cm−2. Furthermore, the film exhibits high energy and power densities of 112.3 Wh kg−1 and 404.4 W kg−1, respectively, as well as high capacitive retention and cycle stability. These findings indicate the potential application of PAH/rGO‐MnO2‐ZnO LbL films as supercapacitor electrodes and envisage further studies of LbL nanostructured systems for energy storage applications.

Bimodal multilayer nanostructure based on vanadium dioxide phase transition: absorber and hot electron photodetector

Bimodal multilayer nanostructure based on vanadium dioxide phase transition: absorber and hot electron photodetector

A Constrained Assembly Strategy for High-Strength Natural Nanoclay Film.

Developing high-performance materials from existing natural materials is highly desired because of their environmental friendliness and low cost; two-dimensional nanoclay exfoliated from layered silicate minerals is a good building block to construct multilayered macroscopic assemblies for achieving high mechanical and functional properties. Nevertheless, the efforts have been frustrated by insufficient inter-nanosheet stress transfer and nanosheet misalignment caused by capillary force during solution-based spontaneous assembly, degrading the mechanical strength of clay-based materials. Herein, a constrained assembly strategy that is implemented by in-plane stretching a robust water-containing nanoclay network with hydrogen and ionic bonding is developed to adjust the 2D topography of nanosheets within multilayered nanoclay film. In-plane stretching overcomes capillary force during water removal and thus restrains nanosheet conformation transition from nearly flat to wrinkled, leading to a highly aligned multilayered nanostructure with synergistic hydrogen and ionic bonding. It is proved that inter-nanosheet hydrogen and ionic bonding and nanosheet conformation extension generate profound mechanical reinforcement. The tensile strength and modulus of natural nanoclay film reach up to 429.0 MPa and 43.8 GPa and surpass the counterparts fabricated by normal spontaneous assembly. Additionally, improved heat insulation function and good nonflammability are shown for the natural nanoclay film and extend its potential for realistic uses.

Microstructural evolution of Cu/W nano-multilayers filler metal during thermal treatment

Copper/Tungsten (Cu/W) nano-multilayers show potential for application as novel low-temperature brazing filler metals. Therefore, researchers are interested in understanding phase stability and microstructural evolution of the nano-multilayers during thermal treatment. A repetition of 50 alternating nanolayers of Cu and W with individual thicknesses of 10 nm were prepared by magnetron-sputtering on silicon substrates. The structural evolution of Cu/W nano-multilayers (NMLs) within the temperature range 400 °C–800 °C was monitored using real-time in-situ XRD, SEM, TEM, SAXS, DSC and in-house XRD system. The results showed that the melting point of Cu/W nano-multilayers determined using DSC was 793.694 °C was remarkably lower than the melting point of bulk Cu(1083 °C) and W (3140 °C). After annealing at 400 °C for 30 min, the surface of the NMLs exhibited more copper grains, with significant coarsening of the copper grains. The layered structure of the Cu/W NMLs was unaffected after annealed at 400 °C. When annealed at 600 °C for 30 min, some Cu particles migrated into the W layers along the internal interface leading to cracks which partially collapsed the original stratified structure. The nano-multilayered structure was completely destroyed when annealed at 800 °C. Further, the in-situ XRD results showed that the copper grains grew substantially, while the tungsten size remained unchanged with increasing temperature.

Nanostructured Top Contact as an Alternative to Transparent Conductive Oxides in Tandem Perovskite/c-Si Solar Cells

In the competition of solar cell efficiency, besides top-performance multijunction cells, tandem cells based on perovskites are also breaking efficiency records to enter into the 30% range. Their design takes advantage of the rapid development of perovskite cells, and the good sharing of the available spectrum between the perovskite, absorbing at short wavelengths, and the c-Si or similar lower band gap material, working at longer wavelengths. In this paper, we present a novel tandem solar cell that combines crystalline silicon (c-Si) and perovskites cells. We analyzed the device with computational electromagnetism based on the finite element method. Our design arranges the perovskite solar cell as a multilayer 1D grating, which is terminated with a gold thin film (top metallic contact). This multilayer nanostructure is placed on top of the c-Si cell and a thin protective dielectric layer of aluminum nitride covers the whole device. The short-circuit current of the perovskite cell is maximized by maintaining the current-matching conditions with the output from the c-Si cell. This optimization considers the geometrical parameters of the grating: period and thickness of the active layer of the perovskite cell. We compared the simulated short-circuit current of this device to the planar tandem solar cell with indium tin oxide (top contact). The comparison shows a slight increment, around 3%, of our device’s performance. Moreover, it has the potential capability to circumvent postprocessing procedures used with transparent contact oxides, which can reduce the device’s final efficiency. Furthermore, our proposed design can take advantage of photolithographic and nanoimprint techniques, enabling large-scale production at a relatively low cost.

Alloying reactions in nanostructured multilayers during intense deformation

Abstract Under intense deformation of metallic multilayer samples, a nanometer-scale layer thickness and grain size develops during repeated cold-rolling. Along with the evolution of the highly refined microstructure, a nanoscale interfacial alloying occurs that can result in an amorphization reaction. The deformation of multilayers exhibits driven system behavior during alloying. As the length scale of the layer thickness converges to the length scale of the mixing zone during rolling, amorphization develops in appreciable volumes. The results from selected experiments demonstrate that the relative specific interfacial area is the key microstructural metric to describe the deformation-driven alloying.

Calculation of the Kapitza resistance at the silicon - alpha–quartz interface for various temperatures

When considering the thermal processes of multilayer nanostructures, a significant part of the energy is dissipated at the boundaries of the layers; to take this factor into account, the Kapitza resistance is used in the simulation. In this study, we calculate the thermal resistance at the Si/SiO2 interface (alpha-quartz) structures for the temperature range up to 567 K. The calculations are carried out based on the acoustic and diffuse mismatch models. The results obtained, in particular, can be used in constructing models of heat transfer in microelectronics.

Evaluation of AES depth profiles with serious artefacts in C/W multilayers

Ion beam mixing was applied to produce tungsten carbide nano-layers in C/W nano-multilayer structures, which was studied by Auger electron spectroscopy depth profiling. The destructive AES depth profiling caused serious artefacts such as tungsten-carbide production at the interfaces, even when choosing the optimal sputter removal conditions. Here we show that ion mixing due to the AES depth profiling could be described by TRIDYN simulation, and compound formation could be also estimated by introducing a simple model. Thus, despite the serious artefact production the original pristine depth distribution could be reconstructed. This evaluation method has been checked on C/W layer systems containing tungsten-carbide enrichment in the interface region (due to high energy ion beam mixing); the true in-depth distribution could be reconstructed. It has been found also that with increasing carbide formation the artefact production decreases allowing the use the AES depth profiling without reconstruction.

Плазмон-активированный фёрстеровский перенос энергии в молекулярных системах

To explain the experimentally observed effect of silver nanoparticles on the fluorescence of organic dyes and the nonradiative intermolecular transfer of electronic excitation energy in multilayer nanostructures, the previously proposed theoretical model of plasmon resonance in spherical nanoparticles of metals was used. The rates of radiative and nonradiative (FRET) processes in film structures with Ag nanoparticles were calculated for fluorescein and rhodamine B molecules, as well as for two-component systems fluorescein–nile red (NR) and rhodamine B–NR. A version of the model was used that takes into account the effect of NPs on FRET between molecules, the radiative decay of donor and acceptor molecules, and the energy transfer from the dye to plasmonic nanoparticles. The calculation of the UDA rate for pairs with different energy transfer efficiency showed a greater increase in the UDA parameter for the fluorescein–nile red pair than for the rhodamine B–nile red pair. Estimation of the fluorescence enhancement factor of donor and energy acceptor molecules and the rate of energy transfer from the dye to silver NPs showed their insignificant contribution to the formation of the resulting energy transfer efficiency enhancement in the presence of plasmonic NPs.

Plasmon-activated Forster energy transfer in molecular systems

To explain the experimentally observed effect of silver nanoparticles on the fluorescence of organic dyes and the nonradiative intermolecular transfer of electronic excitation energy in multilayer nanostructures, the previously proposed theoretical model of plasmon resonance in spherical nanoparticles of metals was used. The rates of radiative and nonradiative (FRET) processes in film structures with Ag nanoparticles were calculated for fluorescein and rhodamine B molecules, as well as for two-component systems fluorescein-nile red (NR) and rhodamine B-NR. A version of the model was used that takes into account the effect of NPs on FRET between molecules, the radiative decay of donor and acceptor molecules, and the energy transfer from the dye to plasmonic nanoparticles. The calculation of the UDA rate for pairs with different energy transfer efficiency showed a greater increase in the UDA parameter for the fluorescein-nile red pair than for the rhodamine B-nile red pair. Estimation of the fluorescence enhancement factor of donor and energy acceptor molecules and the rate of energy transfer from the dye to silver NPs showed their insignificant contribution to the formation of the resulting energy transfer efficiency enhancement in the presence of plasmonic NPs. Keywords: energy transfer, silver nanoparticles, plasmon, model

Determination of the thicknesses and depths of subsurface nanostructures using a scanning electron microscope

The calculated ratios of the signal of backscattered electrons for multilayer nanostructures are derived depending on the energy of probing electrons and composition of multicomponent samples. From experimentally measured signals and calculated ratios, not only thicknesses but also, for the first time, depths of occurrence of local microheterogeneities of three-dimensional nanostructures were determined. The studies were carried out by a non-destructive method of detecting backscattered electrons in a scanning electron microscope. Keywords: multilayer nanostructures, scanning electron microscopy.

Cu-induced NiCu-P and NiCu-Pi with multilayered nanostructures as highly efficient electrodes for hydrogen production via urea electrolysis.

Since urea is commonly present in domestic sewage and industrial wastewater, its use in hydrogen production by electrolysis can simultaneously help in water decontamination. To achieve this goal, the development of highly active and inexpensive urea electrolysis catalysts is necessary. This study deals with the preparation of multilayered nickel and copper phosphides/phosphates (NiCu-P/NF and NiCu-Pi/NF) supported on Ni foam (NF) and their application as new electrocatalyst types for the electrolysis of urea-containing wastewaters. In these materials, Cu atoms induce the formation of multilayer nanostructures and modulate electron distribution, allowing for the exposure of additional active sites and acceleration of the process kinetics. NiCu-P/NF is used as a cathode and NiCu-Pi/NF as an anode in an electrolysis cell and exhibits significant catalytic activity and stability in the urea oxidation reaction (UOR) and the hydrogen evolution reaction (HER). The NiCu-Pi/NF||NiCu-P/NF electrolysis cell, operating with an alkaline urea-containing aqueous electrolyte, achieves a current density of 10 mA cm- at a potential of 1.41 V, which is less than required by the RuO2||Pt/C cell utilizing commercial noble metal-based electrodes. The study provides a novel strategy for designing efficient catalysts to produce hydrogen by urea electrolysis.

Magnetic impedance of film nanostructures for stray magnetic field evaluation of microparticles in magnetic composites

Longitudinal giant magnetoimpedance effect of [Fe21Ni79/Cu]5/Cu/[Fe21Ni79/Cu]5 film element was investigated depends on stray magnetic field of epoxy magnetic composite with 30% weight concentration of iron oxide magnetic microparticles. Configuration of an experiment was a model of thrombus detection in a blood vessel. Stray magnetic field was varied by movement of a magnetic composite above the element perpendicular to the long side. Composite was either magnetized or not to the state of remanence. As the magnetic composite approaches the GMI element, MI ratio curves are smoothed and shifted along the field axis and maximum value of the MI ratio decreases. Magnetic properties of magnetic composite and film element were investigated as well. Keywords: Magnetoimpedance effect, multilayered film nanostructures, composite materials, biodetection.

Engineering Er3+-sensitized nanocrystals to enhance NIR II-responsive upconversion luminescence.

An Er3+-sensitized system with a high response to 1550 nm radiation in the second near-infrared window (NIR II) has been considered for a new class of potential candidates for applications in bio-imaging and advanced anti-counterfeiting, yet the achievement of highly efficient upconversion emission still remains a challenge. Here, we constructed a novel Er3+-sensitized core-shell-shell upconversion nanostructure with a Yb3+-enriched core as the emitting layer. This designed nanostructure allows the Yb3+ emitting layer to more efficiently trap and lock excitation energy by combining the interfacial energy transfer (IET) from the shell (Er3+) to the core (Yb3+), high activator Yb3+ content, and minimized energy back-transfer. As a result, the NIR II emission at 1000 nm is remarkably enhanced with a high quantum yield (QY) of 11.5%. Based on this trap and lock-in effect of the excitation energy in the Yb3+-enriched core, highly efficient 1550 nm-responsive visible and NIR upconversion emissions are also achieved by co-doping with other activator ions (e.g., Ho3+ and Tm3+). Our research provides a new functional design for improving NIR II-responsive upconversion luminescence, which is significant for developing practical applications.