Multilayer Nanostructures Research Articles

Catalytic synthesis of 3D graphene nanostructures from biomass-based activated carbon with excellent lithium storage performance

3D multilayer graphene anode materials have shown great potential for energy storage devices due to their extraordinary structural stability combined with unique electrochemical characteristics. Herein, a facile strategy is proposed to synthesize 3D multilayer graphene nanostructures (M-GNS, M refers to graphitization catalyst) via microwave catalytic graphitization incorporated with liquid oxidation and thermal reduction using biomass-based activated carbon. The role of various graphitization catalysts on the characteristics and lithium storage performance of GNS were systematically investigated. Transmission electron microscopy results show that the use of Co led to the formation of multilayer graphene nanostructures with lower thickness compared to Ni and Fe. Various characterization techniques showed that the degree of graphitization in Co-graphitized activated carbon was lower, and the sample was dominated by smaller graphitic structures. When used as lithium-ion battery anode material, Co-GNS delivered superior rate capability (357 mAhg−1 at 5 Ag−1 after 1000 cycles with a capacity retention of ~94 %), and ultrahigh charge capacity (1695 mAhg−1 at 0.1 Ag−1), mainly owing to its thinner multilayer nanostructure.

Deep learning empowering design for selective solar absorber

Abstract The selective broadband absorption of solar radiation plays a crucial role in applying solar energy. However, despite being a decade-old technology, the rapid and precise designs of selective absorbers spanning from the solar spectrum to the infrared region remain a significant challenge. This work develops a high-performance design paradigm that combines deep learning and multi-objective double annealing algorithms to optimize multilayer nanostructures for maximizing solar spectral absorption and minimum infrared radiation. Based on deep learning design, we experimentally fabricate the designed absorber and demonstrate its photothermal effect under sunlight. The absorber exhibits exceptional absorption in the solar spectrum (calculated/measured = 0.98/0.94) and low average emissivity in the infrared region (calculated/measured = 0.08/0.19). This absorber has the potential to result in annual energy savings of up to 1743 kW h/m2 in areas with abundant solar radiation resources. Our study opens a powerful design method to study solar-thermal energy harvesting and manipulation, which will facilitate for their broad applications in other engineering applications.

Rapid assembly of multilayer nanostructured FG/Al energetic materials to obtain high combustion reactivity

Fluorinated reactive materials as new energetic materials are widely studied because of their high combustion heat and the ability to release large amounts of gaseous products. In order to further improve combustion reaction and the energy release efficiency, structural processing strategy is usually adopted to construct unique microstructures for fluorinated reactive materials. In this work, it is found that fluorinated graphene (FG) and nano-aluminum (nAl) can be rapidly assembled by the intercalation-like method to form multilayer nanostructured energetic materials with particle mosaic. Based on this, the energy output performance of these multilayer nanostructured energetic materials can be effectively regulated by changing the ratio of FG to nAl. The shortest laser ignition delay time (8 ms) and the longest burning time (56 ms) can be achieved for the multilayer nanostructured energetic material with proper FG/Al ratio, while the burning rate of the sample spline can reach 14.83 cm/s. In addition, the reaction process of multilayer nanostructured FG/Al energetic materials depends upon oxygen content that participates in the reaction in different atmospheres, leading to the different pressure output performance. This study provides a promising strategy for the further application of fluorinated reactive materials in the field of energetic materials.

Thermomagnetic transition in nanoscale synthetic antiferromagnets Py/NiCu/Py

Using the method of SQUID magnetometry, the features of the antiferromagnet-ferromagnet thermomagnetic transition in arrays of the nanosized disks of Py/NiCu/Py synthetic antiferromagnets (SAFs) have been investigated. The effective interlayer interaction in individual SAFs “ferromagnet/diluted ferromagnet/ferromagnet” (F2/f/F1) changes from high-temperature antiferromagnetic to low-temperature ferromagnetic upon the transition at the Curie temperature TCf of the interlayer f. Temperature dependence of the magnetic parameters of individual layers and their effect on the features of the thermomagnetic transition are determined. The observed properties are important for the development of temperature-controlled nanoscale SAFs and multilayer nanostructures based on them.

Sonochemistry of Liquid-Metal Galinstan toward the Synthesis of Two-Dimensional and Multilayered Gallium-Based Metal-Oxide Photonic Semiconductors.

The scientific field of two-dimensional (2D) nanostructures has witnessed tremendous development during the last decade. To date, different synthesis approaches have been developed; therefore, various exceptional properties of this family of advanced materials have been discovered. It has recently been found that the natural surface oxide films of room-temperature liquid metals is an emerging platform for the synthesis of novel types of 2D nanostructures with numerous functional applications. However, most of the developed synthesis techniques for these materials are based on the direct mechanical exfoliation of 2D materials as research targets. This paper reports a facile and functional sonochemical-assisted approach for the synthesis of 2D hybrid and complex multilayered nanostructures with tunable characteristics. In this method, the intense interaction of acoustic waves with microfluidic gallium-based room-temperature liquid galinstan alloy provides the activation energy for synthesis of hybrid 2D nanostructures. The microstructural characterizations reveal the impact of sonochemical synthesis parameters, including the processing time and composition of the ionic synthesis environment, on the growth of GaxOy/Se 2D hybrid structures and InGaxOy/Se multilayered crystalline structures with tunable photonic characteristics. This technique shows promising potential for synthesis of various types of 2D and layered semiconductor nanostructures with tunable photonic characteristics.

Predictive combining multiple variously hybridized low-dimensional nanocarbons in a single additive for nano-sized energetic materials performance enhancement

We propose to uncover new opportunities for predictive nano-sized energetic materials performance enhancement through manipulating by vibrational interactions, energy exchange as well as heat transfer enhancement within the reaction zones at nanoscale. The combination of multiple carbon nanostructured materials with various hybridizations within a single substance can uncover new unique properties. Due to a recent fundamental discovery the collective atomic vibrations, called phonon waves, manifested in transition domains of multilayer nanostructures, incorporation of self-organized arrays of metastable nanostructures are capable controlling vibrational interactions and energy exchange within the reaction zones at nanoscale. For using this phenomenon, we propose predictive incorporation into the nano-sized energetic material composition of various carbon-based allotropes, used as catalytic nano-additives, combined with assembling them by the self-organized arrays of differently hybridized low-dimensional nanocarbon promoters. For predictive combining of multiple differently hybridized nanocarbons within a single substance we propose to use the energy-driven initiation of the allotropic phase transformations in nanocarbon promoters by concurrent electron and ion irradiation. For fine tuning the collective atomic vibrations, nanoarchitecture and functionality of the mentioned arrays of differently hybridized nanocarbon promoters we propose using combination of a set of techniques: concurrent electron and ion irradiation, using the surface acoustic waves combined with heteroatom doping along with application external electromagnetic fields and using the data-driven nanoscale manufacturing approach.

Layer dependent pyro-phototronic effect in Al/ nanostructured porous silicon multi-layer (PS-ML) UV sensing Schottky photovoltaic device

The present letter reports layer dependent UV (365 nm) photo-sensing performance in Al: PS-ML: p+-Si Schottky photovoltaic device aided by pyro-phototronic behaviour with incremental value of 156%,221%,128% and pyro response and recovery times of 0.4 s, 0.5 s, 0.7 s and 1 s, 1.3 s, 1.1 s for three PS-ML devices respectively. The open circuit voltage (Voc) and Fill factor (FF) for the devices are found to be -194mV,-200mV,-345mVand29%,32%,29%.

Wear and Corrosion Performance of Ti-6Al-4V Alloy Arc-Coated TiN/CrN Nano-Multilayer Film

The objective of this study was to investigate the effect of varying bias parameters (−50 V, −100 V, and −150 V) on the properties of TiN/CrN multilayer films deposited on Ti-6Al-4V alloy using the cathodic arc deposition (CAD) technique. The deposited films were characterized for their composition, structure, morphology, thickness, adhesion, and hardness. Wear and polarization tests were also conducted to determine the optimal bias condition for wear and corrosion resistance. The results showed that the TiN/CrN films possessed a nano-multilayered structure comprising TiN and CrN phases. The hard coating significantly increased the surface hardness of Ti-6Al-4V alloy up to three–five times. The coated specimens demonstrated superior wear resistance compared to the uncoated, with the −150 V specimen exhibiting the least wear rate. Furthermore, the −150 V specimen had the highest polarization impedance value, indicating the best corrosion resistance compared to the other bias conditions. In short, the use of CAD-coated TiN/CrN multilayer film enhanced the surface properties of Ti-6Al-4V alloy, with the best wear and corrosion resistance achieved at −150 V bias. These novel findings have significant implications for improving the performance and durability of Ti-6Al-4V alloy components in various industrial applications.

Remote-Triggered Domino-like Cyclodehydrogenation in Second-Layer Topological Graphene Nanoribbons

Cyclodehydrogenation reactions in the on-surface synthesis of graphene nanoribbons (GNRs) usually involve a series of Csp2-Csp2 and/or Csp2-Csp3 couplings and just happen on uncovered metal or metal oxide surfaces. It is still a big challenge to extend the growth of second-layer GNRs in the absence of necessary catalytic sites. Here, we demonstrate the direct growth of topologically nontrivial GNRs via multistep Csp2-Csp2 and Csp2-Csp3 couplings in the second layer by annealing designed bowtie-shaped precursor molecules over one monolayer on the Au(111) surface. After annealing at 700 K, most of the polymerized chains that appear in the second layer covalently link to the first-layer GNRs that have partially undergone graphitization. Following annealing at 780 K, the second-layer GNRs are formed and linked to the first-layer GNRs. Benefiting from the minimized local steric hindrance of the precursors, we suggest that the second-layer GNRs undergo domino-like cyclodehydrogenation reactions that are remotely triggered at the link. We confirm the quasi-freestanding behaviors in the second-layer GNRs by measuring the quasiparticle energy gap of topological bands and the tunable Kondo resonance from topological end spins using scanning tunneling microscopy/spectroscopy combined with first-principles calculations. Our findings pave the avenue to diverse multilayer graphene nanostructures with designer quantum spins and topological states for quantum information science.

Selectively Manipulating Interactions between Lanthanide Sublattices in Nanostructure toward Orthogonal Upconversion.

Smart control of ionic interactions is a key factor to manipulate the luminescence dynamics of lanthanides and tune their emission colors. However, it remains challenging to gain a deep insight into the physics involving the interactions between heavily doped lanthanide ions and in particular between the lanthanide sublattices for luminescent materials. Here we report a conceptual model to selectively manipulate the spatial interactions between erbium and ytterbium sublattices by designing a multilayer core-shell nanostructure. The interfacial cross-relaxation is found to be a leading process to quench the green emission of Er3+, and red-to-green color-switchable upconversion is realized by fine manipulation of the interfacial energy transfer on the nanoscale. Moreover, the temporal control of up-transition dynamics can also lead to an observation of green emission due to its fast rise time. Our results demonstrate a new strategy to achieve orthogonal upconversion, showing great promise in frontier photonic applications.

Base Elements for Artificial Neural Network: Structure Modeling, Production, Properties

A radical reduction in power consumption is becoming an important task in the development of supercomputers. Artificial neural networks (ANNs) based on superconducting elements of spintronics seem to be the most promising solution. A superconducting ANN needs to develop two basic elements - a nonlinear (neuron) and a linear connecting element (synapse). The theoretical and experimental results of this complex and interdisciplinary problem are presented in this paper. The results of our theoretical and experimental study of the proximity effect in a stacked superconductor/ferromagnet (S/F) superlattice with Co-ferromagnetic layers of various thicknesses and coercive fields and Nb-superconducting layers of constant thickness equal to the coherence length of niobium and some studies using computer simulation of the formation of such multilayer nanostructures and their magnetic properties are presented in this article.

Effect of Different Si Target Currents on Performance of Magnetron Sputtering Wear Resistant Coatings

In order to ameliorate the properties of the coating material on the surface of the key moving parts of artillery, the influence of different Si target currents on microstructure and mechanical performances of magnetron sputtering TiAlMoSiN coating was studied. The phase structure of the coating, microstructure, coating adhesion, friction and wear properties were characterized, respectively. The deposited TiAlMoSiN coatings were mainly composed of TiN phase, Mo2N phase, amorphous Si3N4 phase and amorphous AlN phase. A typical columnar nano-multilayer structure was formed on the TiAlMoSiN coating after magnetron sputtering process. When the Si target current reached 1.0A, the coating hardness was supreme, valued 32.6 GPa. Along with the addition of the Si target current, the hardness and the bonding strength between the coatings and 45 steel substrates declined. As the Si target current was 1.5 A, TiAlMoSiN coating has the lowest friction coefficient and wear rate. Moreover, it was found out the coating with Si target current at 1.0A had shown the optimal surface properties.

Exceptional Sorption of Heavy Metals from Natural Water by Halloysite Particles: A New Prospect of Highly Efficient Water Remediation.

Halloysite particles, with their unique multilayer nanostructure, are demonstrated here as highly efficient and readily available sorbent of heavy metals that can be easily scaled up and used in large-scale water remediation facilities. The various methods of raw material purification were applied, and their effects were verified using techniques such as BET isotherm (determination of specific surface area and size of pores), XRF analysis (composition), and SEM imaging (determination of morphology). A series of adsorption experiments for aqueous solutions of metal ions (i.e., lead, cadmium) were carried out to quantify the sorption capacity of halloysite particles for selected heavy metals. The ability of adequately activated halloysite to efficiently remove heavy metal ions from water solutions was confirmed. The value of the zeta potential of raw and purified halloysite particles in water was determined. This enables us to understand its importance for the sorption of positively charged ions (metal, organics) at various pH values. The adsorption process conducted in the pH range of 6.0-6.5 showed significant improvement compared to the acidic conditions (pH value 3.0-3.5) and resulted in a high sorption capacity of lead ions-above 24.3 mg/g for the sulphuric acid-treated sample. The atomic scale ab initio calculations revealed a significant difference in adsorption energy between the external siloxane surface and cross-sectional interlayer surface, resulting in pronounced adsorption anisotropy. A low energy barrier was calculated for the interlayer migration of heavy metals into the halloysite interior, facilitating access to the active sites in these regions, thus significantly increasing the sorption capacity and kinetics. DFT (density functional theory) calculations supporting this study allowed for predicting the sorption potential of pure halloysite structure towards heavy metals. To confront it with experimental results, it was crucial to determine proper purification conditions to obtain such a developed structure from the mineral ore. The results show a massive increase in the BET area and confirm a high sorption potential of modified halloysite towards heavy metals.

Lead-free MAGeI3 as a suitable alternative for MAPbI3 in nanostructured perovskite solar cells: a simulation study

The lead is a heavy metal with hazardous impacts on environment and human life. Lead-free perovskite solar cells have attracted much attention in recent years, due to eco-friendly characteristics. Meanwhile, Pb-containing cells showed the highest efficiencies among the various types of cells. Hence, designing novel Pb-free solar cells with comparable or better performance than the Pb-containing ones is highly required. In this work, a lead-free methyl-ammonium-germanium-iodide (MAGeI3)-based perovskite solar cell with ITO/TiO2/MAGeI3/Spiro-OMeTAD/Ag multilayer nanostructure has been proposed and its main characteristics including open-circuit voltage (VOC) and power conversion efficiency (η) have been evaluated and compared with those of MAPbI3-based cell, in simulation study. The VOC and η of the MAGeI3-based cell (1.18V and 11.9%) have been found comparable with those of the MAPbI3 one (1.10V and 14.6%). These results can excite more attention to Ge as a more environment-friendly element than Pb, in highly efficient upcoming perovskite solar cells.

Enhanced Imaging Using Inverse Design of Nanophotonic Scintillators

AbstractConverting ionizing radiation into visible light is essential in a wide range of fundamental and industrial applications, such as electromagnetic calorimeters in high‐energy particle detectors, electron detectors, image intensifiers, and X‐ray imaging. These different areas of technology all rely on scintillators or phosphors, i.e., materials that emit light upon bombardment by high‐energy particles. In all cases, the emission is throughspontaneous emission. The fundamental nature of spontaneous emission poses limitations on all these technologies, imposing an intrinsictrade‐offbetween efficiency and resolution in all imaging applications: thicker phosphors are more efficient due to their greater stopping power, which however comes at the expense of image blurring due to light spread inside the thicker phosphors. Here, the concept of inverse‐designed nanophotonic scintillators is proposed, which can overcome the trade‐off between resolution and efficiency by reshaping the intrinsic spontaneous emission. To exemplify the concept, multilayer phosphor nanostructures are designed and these nanostructures are compared to state‐of‐the‐art phosphor screens in image intensifiers, showing a threefold resolution enhancement simultaneous with a threefold efficiency enhancement. The enabling concept is applying the ubiquitous Purcell effect for the first time in a new context—for improving image resolution. Looking forward, this approach directly applies to a wide range of technologies, including X‐ray imaging applications.

Investigation of the Properties of Multilayer Nanostructured Coating Based on the (Ti,Y,Al)N System with High Content of Yttrium

The studies are focused on the properties of the multilayer composite coating based on the (Ti,Y,Al)N system with high content of yttrium (about 40 at.%) of yttrium (Y). The hardness and elastic modulus were defined, and the resistance to fracture was studied during the scratch testing. Two cubic solid solutions (fcc phases), including c-(Ti,Y,Al)N and c-(Y,Ti,Al)N, are formed in the coating. The investigation of the wear resistance of the (Ti,Y,Al)N-coated tools during the turning of steel in comparison with the wear resistance of the tools with the based on the (Ti,Cr,Al)N system coating and the uncoated tools found a noticeable increase (by 250%–270%) in rake wear resistance. Active oxidation processes are observed in the (Ti,Y,Al)N coating during wear. It can be assumed that yttrium oxide is predominantly formed with a possible insignificant formation of titanium and aluminum oxides. At the same time, complete oxidation of c-(Y,Ti,Al)N nanolayers is not observed. Some hypotheses explaining the rather high performance of a coating with a high yttrium content are considered.

Targeted silencing of the MCL-1 gene using multi-layered dendrimer-based nanoconstructs achieves efficient tumor regression in xenografted mice models

The setback in the practical clinical use of RNA interference (RNAi)-based cancer treatment stems from the lack of targeted small interfering RNA (siRNA) delivery. Here, we show that luteinizing hormone-releasing hormone(LHRH) analog-tethered multi-layered polyamidoamine (PAMAM) nanoconstructs silence the anti-apoptotic MCL-1 gene in LHRH receptor overexpressing human breast (MCF-7) and prostate cancer (LNCaP) cells with 70.91 % and 74.10 % efficiency, respectively. These results were confirmed by RT-PCR. The Acridine orange/Ethidium bromide (AO/EB) dual staining revealed that the silencing of MCL-1 induced apoptosis in both the cell lines. In vivo tumor regression studies performed using MCF-7 and LNCaP xenografted severe combined immunodeficiency(SCID) mice demonstrated highly improved tumor regression in groups treated with targeted nanoconstructs complexed with MCL-1 siRNA (T + siMCL-1) compared to the other treatment groups. The quantitative RT-PCR results of tumor tissues demonstrated significant MCL-1 gene silencing, i.e., 73.76 % and 92.63 % in breast and prostate tumors, respectively, after T + siMCL-1 treatment. Reduction in MCL-1 protein expression as assessed by immunohistochemistry further confirmed these results. Furthermore, the caspase 3/7 assay demonstrated apoptosis in the MCL-1 silenced tissues. The study strongly suggests that targeted delivery of siRNAs using multi-layered dendrimer nanostructures could be an effective therapy for LHRH overexpressing cancers.

Layer-by-layer assembly of nanomultilayer structures: Reinforcement of expanded char reduced the toxicity and fire hazard of epoxy resins

Epoxy resins (EP) have been widely applied in chemical engineering, composite materials, and aerospace. Nevertheless, the high fire hazard of flammable epoxy resins, which release considerable hazardous substances and heat during combustion, limits their further application. In this work, a hierarchical structure (Gr/BPA@Si) based on graphene (Gr) assembled with hexagonal boron nitride nanosheets (h-BN) modified with polyaniline (PANI) and epoxy-based polyhedral oligomeric sesquisiloxane (EPOSS) was rationally combined with the conventional P-N-C intumescent system to construct an EP flame retardant. Concretely, the peak heat release rate (PHRR) and total heat release (THR) of the EP matrix incorporating 2 wt% Gr/BPA@Si (Gr/BPA@Si/EP) decreased by 26.7 % and 28.3 %, respectively, and the limiting oxygen index (LOI) increased from 24.7 % to 31.8 %. Moreover, the peak smoke production rate (PSPR) and total smoke release (TSP) were reduced by 27.8 % and 24.7 %, respectively, reflecting attenuated fire toxicity. Mechanistic investigation reveals that the enhanced flame retardancy and smoke suppression properties of the polymers were due to the synergistic effect of Gr/BPA@Si nanosheets and P-N-C intumescent system during the combustion process. This work presents a promising strategy for the development of polymer composites with high fire resistance and smoke suppression capability through the physical barrier effect formed by expansion.

Two-Level 3D Column-like Nanofilms with Hexagonally-Packed Tantalum Fabricated via Anodizing of Al/Nb and Al/Ta Layers-A Potential Nano-Optical Biosensor.

Reanodizing metal underlayers through porous anodic alumina has already been used extensively to fabricate ordered columns of different metal oxides. Here, we present similar 3D multilayered nanostructures with unprecedented complexity. Two-level 3D column-like nanofilms have been synthesized by anodizing an Al/Nb metal layer in aqueous oxalic acid for forming the first level, and an Al/Ta layer in aqueous tartaric acid for forming the second level of the structure. Both levels were then reanodized in aqueous boric acid. The Ta layer deposited on partially dissolved porous anodic alumina of the first level, with protruding tops of niobia columns, acquired a unique hexagonally-packed structure. The morphology of the first and second levels was determined using scanning electron microscopy. Prolonged etching for 24 h in a 50%wt aqueous phosphoric acid was used to remove the porous anodic alumina. The formation mechanism of aluminum phosphates on the second-level columns in the process of long-time cold etching is considered. The model for the growth of columns on a Ta hexagonally-packed structure of the second level is proposed and described. The described approach can be applied to create 3D two- or three-level column-like systems from various valve metals (Ta, Nb, W, Hf, V, Ti), their combinations and alloys, with adjustable column sizes and scaling. The results of optical simulation show a high sensitivity of two-level column-like 3D nanofilms to biomedical objects and liquids. Among potential applications of these two-level column-like 3D nanofilms are photonic crystals for full-color displays, chemical sensors and biosensor, solar cells and thermoresponsive shape memory polymers.

Study of Tribotechnical Properties of Multilayer Nanostructured Coatings and Contact Processes during Milling of Titanium Alloys

The paper presents the results of theoretical and experimental research on tribotechnical characteristics: tool wear on the back surface, tool durability period, critical length of the cutting path before blunting, adhesion component of the friction coefficient, contact processes, temperature, and force dependences for the application of innovative nanostructured multilayer composite coatings on a tool for milling of titanium alloys. The proposed thermodynamic model of cutting tool wear allows us to determine the ways by which cutting tool wear intensity decreases and the conditions of increase in cutting tool wear resistance with wear-resistant coatings. A substantial increase in wear resistance of end mills when processing titanium alloys with the use of innovative multilayer nanostructured coatings is established, in particular an improvement of an average of 1.5–2 times. These positive results are related to a significant decrease in temperature–force loading in the cutting zone, a decrease in the friction coefficient (adhesion component), and the phenomenon of adaptation (self-organization) of friction surfaces during cutting by tools with wear-resistant coatings, contributing to the formation of films of various compounds with shielding, protective, and lubricating properties.