Nanoscale Components Research Articles

Quantum Statistical Transport Phenomena in Memristive Computing Architectures

The advent of reliable, nanoscale memristive components is promising for next generation compute-in-memory paradigms, however, the intrinsic variability in these devices has prevented widespread adoption. Here we show coherent electron wave functions play a pivotal role in the nanoscale transport properties of these emerging, non-volatile memories. By characterizing both filamentary and non-filamentary memristive devices as disordered Anderson systems, the switching characteristics and intrinsic variability arise directly from the universality of electron transport in disordered media. Our framework suggests localization phenomena in nanoscale, solid-state memristive systems are directly linked to circuit level performance. We discuss how quantum conductance fluctuations in the active layer set a lower bound on device variability. This finding implies there is a fundamental quantum limit on the reliability of memristive devices, and electron coherence will play a decisive role in surpassing or maintaining Moore's Law with these systems.

Metal-Bridged Graphene-Protein Supraparticles for Analog and Digital Nitric Oxide Sensing.

Self-limited nanoassemblies, such as supraparticles (SPs), can be made from virtually any nanoscale components, but SPs from nanocarbons including graphene quantum dots (GQDs), are hardly known because of the weak van der Waals attraction between them. Here it is shown that highly uniform SPs from GQDs can be successfully assembled when the components are bridged by Tb3+ ions supplementing van der Waals interactions. Furthermore, they can be coassembled with superoxide dismutase, which also has weak attraction to GQDs. Tight structural integration of multilevel components into SPs enables efficient transfer of excitonic energy from GQDs and protein to Tb3+ . This mechanism is activated when Cu2+ is reduced to Cu1+ by nitric oxide (NO)-an important biomarker for viral pulmonary infections and Alzheimer's disease. Due to multipronged fluorescence enhancement, the limit of NO detection improves 200 times reaching 10 × 10-12 m. Furthermore, the uniform size of SPs enables digitization of the NO detection using the single particle detection format resulting in confident registration of as few as 600 molecules mL-1 . The practicality of the SP-based assay is demonstrated by the successful monitoring of NO in human breath. The biocompatible SPs combining proteins, carbonaceous nanostructures, and ionic components provide a general path for engineering uniquely sensitive assays for noninvasive tracking of infections and other diseases.

Microarchitectural Silk Fibroin/Hyaluronic Acid Scaffold via Slight Biodegradation

Silk-based scaffolds with hierarchical structure possess the capacities of promoting cells adhesion, proliferation and neotissue formation, which have been one of the candidates in tissue engineering. However, the ways to construct hierarchical structures in scaffolds are very limited, rather than introducing other nanoscale components. In this study, a hierarchical porous structure was directly established in silk fibroin/hyaluronic acid (SF/HA) scaffold through slight degradation technique. The resulting SF/HA scaffold presented desirable microarchitecture and appropriate porosity attribute to partial hydrolysis of SF molecules. The compression test showed that the SF/HA scaffolds was better than SF scaffolds in terms of compression stress and Young’s modulus. More importantly, the SF/HA scaffolds displayed good cytocompatibility as to supporting cells adhesion and proliferation. This paper provides a new strategy for preparing SF-based scaffolds with hierarchical porous structure in tissue engineering.

Empirical metal-oxide RRAM device endurance and retention model for deep learning simulations

Memristive devices including resistive random access memory (RRAM) cells are promising nanoscale low-power components projected to facilitate significant improvement in power and speed of Deep Learning (DL) accelerators, if structured in crossbar architectures. However, these devices possess non-ideal endurance and retention properties, which should be modeled efficiently. In this paper, we propose a novel generalized empirical metal-oxide RRAM endurance and retention model for use in large-scale DL simulations. To the best of our knowledge, the proposed model is the first to unify retention-endurance modeling while taking into account time, energy, SET-RESET cycles, device size, and temperature. We compare the model to state-of-the-art and demonstrate its versatility by applying it to experimental data from fabricated devices. Furthermore, we use the model for CIFAR-10 dataset classification using a large-scale deep memristive neural network (DMNN) implementing the MobileNetV2 architecture. Our results show that, even when ignoring other device non-idealities, retention and endurance losses significantly affect the performance of DL networks. Our proposed model and its DL simulations are made publicly available.

Macroscopic materials assembled from nanoparticle superlattices.

Nanoparticle assembly has been proposed as an ideal means to program the hierarchical organization of a material by using a selection of nanoscale components to build the entire material from the bottom up. Multiscale structural control is highly desirable because chemical composition, nanoscale ordering, microstructure and macroscopic form all affect physical properties1,2. However, the chemical interactions that typically dictate nanoparticle ordering3-5 do not inherently provide any means to manipulate structure at larger length scales6-9. Nanoparticle-based materials development therefore requires processing strategies to tailor micro- and macrostructure without sacrificing their self-assembled nanoscale arrangements. Here we demonstrate methods to rapidly assemble gram-scale quantities of faceted nanoparticle superlattice crystallites that can be further shaped into macroscopic objects in a manner analogous to the sintering of bulk solids. The key advance of this method is that the chemical interactions that govern nanoparticle assembly remain active during the subsequent processing steps, which enables the local nanoscale ordering of the particles to be preserved as the macroscopic materials are formed. The nano- and microstructure of the bulk solids can be tuned as a function of the size, chemical makeup and crystallographic symmetry of the superlattice crystallites, and the micro- and macrostructures can be controlled via subsequent processing steps. This work therefore provides a versatile method to simultaneously control structural organization across the molecular to macroscopic length scales.

Tribological Fracture of Ferritic-Pearlitic Steel with Nano and Submicron Structure during Sliding Friction

An urgent task of tribology is to study the wear mechanisms of various materials for the development of stable wear-resistant microstructures and optimal modes of their production. The purpose of this work is to assess the wear resistance of low-alloy steel with a submicrocrystalline ferritic matrix, reinforced with nano- and microspheres of cementite, as well as to reveal the features of its destruction by friction based on the analysis of friction surfaces. Steel nanostructuring was carried out using cold (at room temperature) equal-channel angular pressing and subsequent annealing. The process of steel wear in coarse-grained and nanosubmicron states has been studied at various stages of tribological loading under sliding friction conditions using optical and scanning electron microscopy, profilometry, and analysis of changes in the roughness parameters of friction surfaces. It is shown that the formation in steel of a heterogeneous structure “submicron ferrite matrix - nanoscale carbide phase” provided an increase in wear resistance by more than two times. The features of contact fracture are revealed, which determine the increase in the wear resistance of steel upon refining the structure and indicate significant differences in the nature of the metal tribological strength formation, depending on the level of dispersion of microstructural elements. The results obtained can be used in the development of technological processes for the formation of nanoscale structural components and improving the properties of traditional low-alloy steels.

Applications of nanotechnology in 3D printed tissue engineering scaffolds

Tissue engineering is an interdisciplinary field that aims to combine life sciences and engineering to create therapies that regenerate functional tissue. Early work in tissue engineering mostly used materials as inert scaffolding structures, but research has shown that constructing scaffolds from biologically active materials can help with regeneration by enabling cell-scaffold interactions or release of factors that aid in regeneration. Three-dimensional (3D) printing is a promising technique for the fabrication of structurally intricate and compositionally complex tissue engineering scaffolds. Such scaffolds can be functionalized with techniques developed by nanotechnology research to further enhance their ability to stimulate regeneration and interact with cells. Nanotechnological components, nanoscale textures, and microscale/nanoscale printing can all be incorporated into the manufacture of 3D printed scaffolds. This review discusses recent advancements in the merging of nanotechnology with 3D printed tissue engineering scaffolds, with a focus on applications of nanoscale components, nanoscale texture, and innovative printing techniques and the effects observed in vitro and in vivo.

Self-assembly of millimeter-scale magnetic particles in suspension.

Self-assembly is ubiquitous at all scales in nature. Most studies have focused on the self-assembly of micron-scale and nano-scale components. In this study, we explore the self-assembly of millimeter-scale magnetic particles in a bubble-column reactor to form 9 different structures. Two component systems (N-N and S-S particles) assemble faster than one-component systems (all particles have N-S poles) because they have more numerous bonding pathways. In addition, two-components add control to process initiation and evolution, and enable the formation of complex structures such as squares, tetrahedra and cubes. Self-assembly is collision-limited, thus, the formation time increases with the total number of bonds required to form the structure and the injected power. The dimensionless Mason number captures the interplay between hydrodynamic forces and magnetic interactions: self-assembly is most efficient at intermediate Mason numbers (the system is quasi-static at low Mason numbers with limited chances for particle interaction; on the other hand, hydrodynamic forces prevail over dipole-dipole interactions and hinder bonding at high Mason numbers). Two strategies to improve yield involve (1) the inclusion of pre-assembled nucleation templates to prevent the formation of incorrect initial structures that lead to kinetic traps, and (2) the presence of boundaries to geometrically filter unwanted configurations and to overcome kinetic traps through particle-wall collisions. Yield maximization involves system operation at an optimal Mason number, the inclusion of nucleation templates and the use of engineered boundaries (size and shape).

Molecular Origin of Electrical Conductivity in Gold-Polythiophene Hybrid Particle Films.

Hybrid electronic materials combine inorganic metals and semiconductors with π-conjugated polymers. The orientation of the polymer molecules in relation to the inorganic components is crucial for electrical material properties and device performance, but little is known of the configuration of π-conjugated polymers that bind to inorganic surfaces. Highly curved surfaces are common when using nanoscale components, for example, metal nanocrystal cores covered with conductive polymers. It is important to understand their effect on molecular arrangement. Here, we compare the molecular structures and electrical conductivities of well-defined nanoscale gold spheres and rods with shells of the covalently bound polythiophene PTEBS (poly[2-(3-thienyl)-ethyloxy-4-butylsulfonate]). We prepared aqueous sinter-free inks from the particles and printed them. The particles formed highly conductive films immediately after drying. Films with spherical metal cores consistently had 40% lower conductivities than films based on nanorods. Raman and X-ray photoelectron spectroscopy revealed differences in the gold-sulfur bonds of PTEBS on rods and spheres. The fractions of bond sulfur groups implied differences in the alignment of PTEBS with the surface. More polymer molecules were bound in an edge-on configuration on spheres than on rods, where almost all polymers aligned "face-on" with the metal surface. This leads to different interface resistances: gold-polythiophene-gold interfaces between rods with π-π-tacked face-on PTEBS apparently foster electron transport along the surface-normal direction, while edge-on PTEBS does not. Molecular confinement thus increases the conductivity of hybrid inks based on highly curved nanostructures.

A Gd@C82 single-molecule electret.

Electrets are dielectric materials that have a quasi-permanent dipole polarization. A single-molecule electret is a long-sought-after nanoscale component because it can lead to miniaturized non-volatile memory storage devices. The signature of a single-molecule electret is the switching between two electric dipole states by an external electric field. The existence of these electrets has remained controversial because of the poor electric dipole stability in single molecules. Here we report the observation of a gate-controlled switching between two electronic states in Gd@C82. The encapsulated Gd atom forms a charged centre that sets up two single-electron transport channels. A gate voltage of ±11 V (corresponding to a coercive field of ~50 mV Å-1) switches the system between the two transport channels with a ferroelectricity-like hysteresis loop. Using density functional theory, we assign the two states to two different permanent electrical dipole orientations generated from the Gd atom being trapped at two different sites inside the C82 cage. The two dipole states are separated by a transition energy barrier of 11 meV. The conductance switching is then attributed to the electric-field-driven reorientation of the individual dipole, as the coercive field provides the necessary energy to overcome the transition barrier.

Morphological Changes and Cellular Uptake of Functionalized Graphene Oxide Loaded with Protocatechuic Acid and Folic Acid in Hepatocellular Carcinoma Cancer Cell.

The development of nanocomposites has swiftly changed the horizon of drug delivery systems in defining a new platform. Major understanding of the interaction of nanocomposites with cells and how the interaction influences intracellular uptake is an important aspect to study in order to ensure successful utilisation of the nanocomposites. Studies have suggested that the nanocomposites’ ability to permeate into biological cells is attributable to their well-defined physicochemical properties with nanoscale size, which is relevant to the nanoscale components of biology and cellular organelles. The functionalized graphene oxide coated with polyethylene glycol, loaded with protocatechuic acid and folic acid (GOP-PCA-FA) nanocomposite intracellular uptake was analysed using transmission electron microscope. The accumulation of fluorescent-labelled nanocomposites in the HepG2 cell was also analysed using a fluorescent microscope. In vitro cellular uptake showed that there was uptake of the drug from 24 h into the cells and the release study using fluorescently tagged nanocomposite demonstrated that release and accumulation were observed at 24 h and 48 h. Moreover, the migration ability of tumor cells is a key step in tumor progression which was observed 48 h after treatment. The GOP serves as a potential nanocarrier system which is capable of improving the therapeutic efficacy of drugs and biomolecules in medical as well as pharmaceutical applications through the enhanced intracellular release and accumulation of the encapsulated drugs. Nonetheless, it is essential to analyse the translocation of our newly developed GOP-PCA-FA, and its efficiency for drug delivery, effective cellular uptake, and abundant intracellular accumulation would be compromised by possible untoward side effects.

Theranostic Pretargeting Drug Delivery and Imaging Platforms in Cancer Precision Medicine.

Theranostics are nano-size or molecular-level agents serving for both diagnosis and therapy. Structurally, they are drug delivery systems integrated with molecular or targeted imaging agents. Theranostics are becoming popular because they are targeted therapeutics and can be used with no or minimal changes for diagnostic imaging to aid in precision medicine. Thus, there is a close relation between theranostics and image-guided therapy (IGT), and theranostics are actually a subclass of IGT in which both therapeutic and imaging functionalities are attributed to a single platform. An important theranostics strategy is biological pretargeting. In pretargeted IGT, first, the target is identified by a target-specific natural or synthetic bioligand followed by a nano-scale or molecular drug delivery component, which form therapeutic clusters by in situ conjugation reactions. If pretargeted drug delivery platforms are labeled with multimodal imaging probes, they can be used as theranostics for both diagnostic imaging and therapy. Optical and nuclear imaging techniques have mostly been used in proof-of-concept studies with pretargeted theranostics. The concept of pretargeting in theranostics is comparatively novel and generally requires a confirmed overexpression of surface receptors on targeted cells/tissue. In addition, the receptors should have natural or synthetic bioligands to be used as pretargeting components. Therefore, applications of pretargeting theranostics are still limited to several cancer types, which overexpress cell-surface markers on the target cancer cells. In this review, recent discoveries of pretargeting theranostics in breast, ovarian, prostate, and colorectal cancers are discussed to highlight main strengths and potential limitations the strategy.

High‐performance HTL‐free perovskite solar cell: An efficient composition of ZnO NRs, RGO, and CuInS2 QDs, as electron‐transporting layer matrix

AbstractA hole‐transporting layer (HTL)‐free perovskite solar cell (PSC) with fluorine‐doped tin oxide (FTO)/nanocomposite electron‐transporting layer (ETL)/perovskite/Au structure is presented that takes advantage of a novel ternary nanocomposite constructed of zinc oxide (ZnO) nanorods, reduced graphene oxide (RGO), and copper indium sulfide quantum dots (CuInS2 QDs), as ETL. Concisely, the photoelectric and photovoltaic properties of all the individual, binary, and ternary composites were monitored by using of the photoluminescence (PL) spectroscopy, UV‐visible (vis) spectroscopy, J‐V curves, and incident photon‐to‐current conversion efficiency (IPCE) spectra studies. The comparative values exhibited a noticeable benefit for the ZnO‐RGO5%‐CuInS220% ternary nanocomposite as an appropriate ETL for PCS. Also, the comparative structural studies on the individual nanoscale components, binary, and ternary nanocomposite (with different percentages of CuInS2 QDs) were precisely performed by Fourier transform infrared (FT‐IR), energy‐dispersive X‐ray (EDX), X‐ray diffraction (XRD), Raman spectroscopy, and field emission scanning electron microscopy (FESEM), as well. Overall, after careful optimization of the ETL, a15.74% efficiency was resulted through applying the prepared ZnO‐RGO5%‐CuInS220% composite in a HTL‐free PCS with 0.33 cm2 active area.

Nanoscale element behavior in a continuum.

Patterns in materials are not just decoration but also important for function. In view of this, the dynamics of patterning procedures in materials has been investigated as an important developmental procedure. In this study, nanoscale components in a continuum are traced in terms of natural patterning procedures. Externally applied compressive or extensive forces to an elastic thin sheet commonly induce an orientated lateral line pattern. From a nanoscale element point of view, the dynamics of natural arrangements, forming anisotropic patterns in preference to isotropy, still remains unclear. In this study, new developmental procedures for line patterns are suggested by stimuli-responsive viscoelastic nanocomposite network model systems. Forces originating from an internal source without directional orientation generate lines in preference to isotropic patterns. With repeated, non-oriented (or isotropic) and self-modulated strain variations, stress is accumulated to drive anisotropic orientations and further lines. The anisotropic elemental arrangement is justified by the equilibrium between the short-range attraction and long-range repulsion from a bottom-up viewpoint. This study suggests a new material design methodology that is useful for electrical devices, biomedical devices and other patterned soft condensed matter in conjunction with line patterns typically generated in a broad range of viscoelastic materials.

Don't Forget Langmuir-Blodgett Films 2020: Interfacial Nanoarchitectonics with Molecules, Materials, and Living Objects.

Designing interfacial structures with nanoscale (or molecular) components is one of the important tasks in the nanoarchitectonics concept. In particular, the Langmuir-Blodgett (LB) method can become a promising and powerful strategy in interfacial nanoarchitectonics. From this viewpoint, the status of LB films in 2020 will be discussed in this feature article. After one section on the basics of interfacial nanoarchitectonics with the LB technique, various recent research examples of LB films are introduced according to classifications of (i) growing research, (ii) emerging research, and (iii) future research. In recent LB research, various materials other than traditional lipids and typical amphiphiles can be used as film components of the LB techniques. Two-dimensional materials, supramolecular structures such as metal organic frameworks, and biomaterials such as DNA origami pieces are capable of working as functional components in the LB assemblies. Possible working areas of the LB methods would cover emerging demands, including energy, environmental, and biomedical applications with a wide range of functional materials. In addition, forefront research such as molecular manipulation and cell fate control is conducted in LB-related interfacial science. The LB technique is a traditional and well-develop methodology for molecular films with a ca. 100 year history. However, there is plenty of room at the interfaces, as shown in LB research examples described in this feature article. It is hoped that the continuous development of the science and technology of the LB method make this technique an unforgettable methodology.

Электродуговой синтез материала на основе графита и карбида молибдена

Представлены результаты экспериментальных исследований синтеза карбида молибдена в плазме дугового разряда постоянного тока безвакуумным методом. Установлено влияние амплитуды тока разрядного контура на фазовый состав продукта синтеза. Продукт синтеза содержит микроразмерную компоненту и наноразмерную. В составе микроразмерной составляющей методами растровой электронной микроскопии и рентгеновской дифрактометрии идентифицированы углеродные волокна со структурой графита, а также модифицированные волокна, содержащие графит и карбид молибдена. Наноразмерная компонента содержит скопления частиц, представляющих собой графитовую матрицу, в которую погружены частицы карбида молибдена.

Energy harvesting from a nanopiezoelectric/piezomagnetic sandwich beam with porous properties

Piezoelectric/piezomagnetic energy harvester has attracted great interest, which can convert magnetic energy into electric power. However, the challenges are how to provide lasting electric energy to the nanoscale components and avoid the inherent brittleness of the piezoelectric and piezomagnetic materials. Therefore, a nanoporous piezoelectric/piezomagnetic beam with a storage circuit is proposed to be an energy harvester in this paper. The nanoporous beam is treated as a sandwich composite beam with the piezoelectric/piezomagentic core bulks and the surface or interface layers. Based on the surface effect theory and the Boit’s porous elasticity, the governing equations and the analytical solutions of the nanoporous piezoelectric/piezomagnetic energy harvester with the flexural mode are obtained. The numerical calculation points out that the resonant frequency, output power density and the output voltage depend on the surface materials parameters, porosity properties, solid-fluid coupling effects, the geometrical dimensions, as well as the piezoelectric/piezomagnetic materials composition of the structure. The results reveal that the resonant frequency interval can be controlled and the output electric power can be improved by adjusting the materials and geometrical parameters.

Nanojoining and tailoring of current–voltage characteristics of metal-P type semiconductor nanowire heterojunction by femtosecond laser irradiation

Selective engineering of the interface between nanoscale components and the electrical properties of heterojunctions is key to the development of next-generation nanoscale circuit elements. In this paper, we show how laser processing of a metal-P type semiconductor nanoscale heterojunction between Ag and CuO nanowires can be used to control the nature of the electrical contact by reducing the Schottky barrier at the Ag–CuO interface to Ohmic contact. Elimination of the Schottky barriers occurs in response to lattice matching of Ag(111)∥CuO(111) planes at the interface induced by controlled irradiation with femtosecond (fs) laser pulses. An interdiffusion region with a mixed Ag/CuO composition is also present over a localized area of the interface between the Ag and CuO nanowires after fs laser processing, but both Ag and CuO nanowires remain crystalline away from the heterojunction. In addition, the Ag nanowire becomes totally embedded in the larger CuO nanowire after irradiation. Fabricated nanowire devices from Ag–CuO nanowire heterojunctions transition from a double-Schottky contact configuration prior to laser processing to a rectifying behavior as irradiation time increases. This study illustrates that fs laser processing can be highly effective in the engineering of electrical performance in metal–semiconductor nanoscale heterojunction devices.

Self-healing biomaterials: The next generation is nano.

The U.S. Agency for Healthcare Research and Quality estimates that there are over 1 million total hip and total knee replacements each year in the U.S. alone. Twenty five percent of those implants will experience aseptic loosening, and bone cement failure is an important part of this. Bone cements are based on poly(methyl methacrylate) (PMMA) systems that are strong but brittle polymers. PMMA-based materials are also essential to modern dental fillings, and likewise, the failure rates are high with lifetimes of 3-10 years. These brittle polymers are an obvious target for self-healing systems which could reduce revision surgeries and visits to dentist. Self-healing polymers have been described in the literature since 1996 and examples from Roman times are known, but their application in medicine has been challenging. This review looks at the development of self-healing biomaterials for these applications and the challenges that lie between development and the clinic. Many of the most promising formulations involve introducing nanoscale components which offer substantial potential benefits over their microscale counterparts especially in composite systems. There is substantial promise for translation, but issues with toxicity, robustness, and reproducibility of these materials in the complex environment of the body must be addressed. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Implantable Materials and Surgical Technologies > Nanomaterials and Implants.

Self-propagating high-temperature synthesis of ceramic composite material based on Al2O3 - SiO2 - ZrB2

The present work is devoted to the production of a ceramic composite material in the mode of self-propagating high-temperature synthesis from a mixture of powder reagents: ZrO2, Al, SiO2, B, and Zr. The adiabatic combustion temperature was calculated for the stoichiometric composition of ZrO2-Al-SiO2 and for compositions with the addition of an energy additive from powders x (Zr + 2B), where x e [10-30] wt. %. It was found that an increase in the fraction of Zr + 2B leads to the refinement of structural elements. An increase in its content to 30 wt. % leads to the formation of nanoscale structural components in the material. As a result of varying the initial composition, a ceramic composite material based on Al2O3-SiO2-ZrB2 was obtained containing an oxide matrix with particles of zirconium diboride distributed from 61 to 77 wt. %. It is shown that as a result of the SHS of the selected compositions, mullite is formed. Using SEM, EDS and XRD methods, we studied the structural features and phase composition of the materials obtained.