Although scanning transmission electron microscopy (STEM) images of individual heavy atoms were reported 50 years ago, the applications of atomic-resolution STEM imaging became wide spread only after the practical realization of aberration correctors on field-emission STEM/TEM instruments to form sub-Ångstrom electron probes. The innovative designs and advances of electron optical systems, the fundamental understanding of electron–specimen interaction processes, and the advances in detector technology all played a major role in achieving the goal of atomic-resolution STEM imaging of practical materials. It is clear that tremendous advances in computer technology and electronics, image acquisition and processing algorithms, image simulations, and precision machining synergistically made atomic-resolution STEM imaging routinely accessible. It is anticipated that further hardware/software development is needed to achieve three-dimensional atomic-resolution STEM imaging with single-atom chemical sensitivity, even for electron-beam-sensitive materials. Artificial intelligence, machine learning, and big-data science are expected to significantly enhance the impact of STEM and associated techniques on many research fields such as materials science and engineering, quantum and nanoscale science, physics and chemistry, and biology and medicine. This review focuses on advances of STEM imaging from the invention of the field-emission electron gun to the realization of aberration-corrected and monochromated atomic-resolution STEM and its broad applications.

Nickel-coated carbon nanotubes (Ni-CNTs) were achieved by electroless plating. Laser cladded IN718 and IN718 with 10, 30, and 50 wt% additions of Ni-CNTs were fabricated. The structural evolution of CNTs in the laser-deposited layers was studied; the microstructure, tensile, and wear properties of the laser-cladded alloys were characterized. The results show that CNTs in the laser-deposited layers are mostly transformed to carbon nanoproducts (CNPs) in the forms of graphene nanosheets, graphene fragments, carbon nanoribbons, and diamond-like nanoparticles by unzipping, interbonding, collapsing, and curvature of CNTs. The interdendritic Laves phase formation is dramatically depressed due to the addition of Ni-CNTs, but the excess addition of the Ni-CNTs can undesirably increase the formation of NbC. The addition of Ni-CNTs effectively improves the tensile and wear properties. The most superior tensile and wear properties are achieved in the layers with 30 and 50 wt% additions of Ni-CNTs, respectively. The generation of intermetallic phase and CNPs are revealed to be two dominant effects both on the tensile and wear properties of the laser-cladded alloys.

Growing zinc oxide (ZnO) nanowires (NWs) on yarns promotes smart sensing and creates opportunities for new applications. ZnO NWs sensing performance is influenced by its dimensions, which can be tailored by controlling the growth parameters. In this study, we investigated the effect of the growth parameters (time, temperature, and precursor concentration ratio) on the NWs’ morphology, dimensions, and piezoelectric performance. Our results showed that ZnO NWs produced with 6 and 9 h had long nanowires; however, they mainly got tangled with the nanowires on the adjacent fibers and peeled-off the fiber surface. Growth at a 1:1 precursor concentration ratio for 9 h produced the same nanowires’ length (~3 μm) as growth at a 3:1 precursor concentration ratio for 3 h. Among all of the studied growth conditions, ZnO NWs produced with a 3:1 precursor concentration ratio at 90 °C for 3 h showed uniform dimensions and stable electrical charge output.

Grain boundary (GB) motions, such as migration, sliding and rotation, have been shown to play a vital role in the mechanical performance of polycrystalline metals. Despite extensive efforts have been made on the pure polycrystalline metals, few attentions have been paid to those in alloys. In this work, taking conventional nanoscale Cu–Al binary alloy system as an example, we intend to shed some light on understanding its GB motions under shear loading by means of molecular dynamics (MD) simulations. It is found that either shear-coupled GB migration or sliding motion can be observed, depending on GB tilt angles, temperatures and Al solute concentrations. By systematical MD simulations, the Al concentration required for transition between shear-coupled migration and sliding is found to decrease with increasing tilt angles (θ ≤ 50°) at fixed temperature, whereas it switches to the opposite trend for larger tilt angles. Furthermore, the GBs migrate much slower comparing with those in pure Cu, which shows the drag effects of the Al solutes in the alloy form. Moreover, the critical stress during shear loading shows a linear dependence on 2/3 power of the temperature.

Titanium dioxide (TiO2) is a semiconductor that can be applied in different technological areas. In this work, we investigated the modifications of the electrical properties of thin films composed of TiO2 nanoparticles produced with different morphologies. The solvothermal route used for the synthesis allowed the production of nanoparticles with functionalized surfaces due to oleate groups. It was possible to modulate nanocrystals shape and size due to the detachment crystal growth mechanism, by changing the reaction time. Nanorods were obtained using 4 h of synthesis, and an increase in the reaction time to 64 h led to a bipyramidal morphology. The functionalization by the organic ligand allowed the preparation of stable colloidal solutions, which were used to prepare thin films by the dip-coating method. The films presented a homogeneous surface, an average thickness around 100 nm, and no agglomerations were observed. The electrical resistance measurements indicated a typical behavior of semiconductors, and they were dependent on the nanoparticle morphology. An exploratory test indicated that the thin films prepared using nanorod particles presented a higher electrical response compared with isotropic particles, when exposed in a liquefied petroleum gas vapor atmosphere. Therefore, the morphology of the nanoparticles is a key factor for the further application of these thin films in gas sensing. Employing an easy methodology which required simple apparatus, and by using reaction time modulation only, it was possible to prepare homogeneous thin films with a tunable electrical response.

Metallic thin-film composite membranes are produced by sputtering metal films onto commercial polymer membranes. The separations capability of the membrane substrate is enhanced with the addition of a 10 nm Ta film. The addition of a tantalum layer decreases the molecular weight cutoff of the membrane from 70 kDa dextran (19 nm) to below 5 kDa (6 nm). Water flux drops from 168 LMH/bar (LMH: liters/meters2/hour) (polymer support) to 8.8 LMH/bar (Ta composite). A nanoporous layer is also added to the surface through Mg/Pd film deposition and dealloying. The resulting nanoporous Pd is a promising catalyst with a ligament size of 4.1 ± 0.9 nm. The composite membrane's ability to treat water contaminated with chlorinated organic compounds (COCs) is determined. When pressurized with hydrogen gas, the nanoporous Pd composite removes over 70% of PCB-1, a model COC, with one pass. These nanostructured films can be incorporated onto membrane supports enabling diverse reactions and separations.

In this study, a hybrid dual drug-loaded hydroxyapatite-oxidized dextran methacrylate core–shell nanocarrier was formulated and explored for combinatorial delivery of doxorubicin (DOX) and methotrexate (MTX) to bone cancer. The synthesized nanocarrier was well characterized by different techniques. In vitro drug release studies in both acidic (pH 5) and alkaline (pH 7.4) conditions showed sequential release of MTX followed by DOX in a sustained manner for 10 days. Biocompatibility and cytotoxicity studies performed using drug-loaded nanoparticles (NPs) on fibroblast L929 cells and osteosarcoma MG63 cells (OMG63) showed that the NPs were highly biocompatible and showed concentration-dependent toxicity. Gene expression studies in OMG-63 cells exhibited the upregulation of caspase-3 and BAX which confirmed the apoptosis induced by dual drug-loaded NPs. The nanocarrier is expected to be a potential bone void filling material, as well as a platform for sequential delivery of DOX and MTX for the treatment of bone cancer.

The strain rate sensitivity (m) of (Ni0.92Zr0.08)100−xAlx (0 ≤ x ≤ 4 at.%) eutectic with varying average lamellae thickness (λw) in the range of 39–275 nm has been investigated in the strain rate range of 8 × 10−5 and 8 × 10−3 s−1 at room temperature. The microstructure of the nano-/ultrafine eutectic composites (NECs) is comprised of alternate lamellae of fcc γ-Ni and Ni5Zr along with 20–31 vol% γ-Ni dendritic phase. The m value of all the investigated NECs lies between 0.0080 and 0.0102, whereas the activation volume (V*) has been estimated to be between 29.7b3 and 49.8b3. High-resolution transmission electron microscopy studies confirm the dislocation-mediated plastic flow including dislocation–lamellae interaction, and their pile-up at the interface, which result in the narrow variation of m for a wide range of λw due to its interlocked lamellar microstructure. A mathematical model has been developed to correlate the m with λw for the experimented NECs with wide microstructure length scale and solute content.

A novel g-C3N4 nanoparticle@porous g-C3N4 (CNNP@PCN) composite has been successfully fabricated by loading g-C3N4 nanoparticles on the porous g-C3N4 matrix via a simply electrostatic self-assembly method. The composition, morphological structure, optical property, and photocatalytic performance of the composite were evaluated by various measurements, including XRD, SEM, TEM, Zeta potential, DRS, PL, FTIR, and XPS. The results prove that the nanolization of g-C3N4 leads to an apparent blueshift of the absorption edge, and the energy band gap is increased from 2.84 eV of porous g-C3N4 to 3.40 eV of g-C3N4 nanoparticle (Fig. 6). Moreover, the valence band position of the g-C3N4 nanoparticle is about 0.7 eV lower than that of porous g-C3N4. Therefore, the photo-generated holes and electrons in porous g-C3N4 can transfer to the conduction band of g-C3N4 nanoparticle, thereby obtaining higher separation efficiency of photo-generated carriers as well as longer carrier lifetime. Under visible-light irradiation, 6CNNP@PCN exhibits the highest photocatalytic performance (Fig. 8) on MB, which is approximately 3.4 times as that of bulk g-C3N4.

Novel three-dimensional (3D) hierarchical macro- to nano-porous titanium (Ti) and TiMo alloys with sufficient compressive strength (CS) were prepared using NaCl spacer and dealloying methods. The dealloying process was implemented by the heat treatment of TiCu and TiMoCu master alloys in Mg powders. The 3D-hierarchical porous structures were composed of large pores having a mean size of 400 μm with interconnected micro-pores in the size of 10–30 μm, where the pore walls possessed numerous nano-pores with a size range of 10–50 nm. The CS and elastic modulus values were 72.4 MPa and 2.67 GPa as well as 92.62 MPa and 3.36 GPa for Ti and TiMo, respectively. The hierarchical porous structure is beneficial for the fast nucleation of bone-like apatite after immersion in simulated body fluid (SBF). In addition, TiMo samples after NaOH and heat treatments provide better apatite formation after soaking in SBF for a week, in comparison with the samples without treatment.

In this paper, we report a recent theoretical study of the calculation of the binding energy and photoionization cross section of a single dopant in a spherical hollow or core/shell quantum dot taking into account the interaction of the electron with longitudinal optical phonons. Using Frolich approach and Lee-low Pines transformation, we determine the impact of different parameters such as shell thickness and dopant position on the energy and optical response of a bound polaron for two types of ionic II–VI semiconductors CdTe and ZnSe with different phonon coupling constants. Regardless of the material used, the electron–phonon interaction visibly reduces binding energy. For photoionization cross section, a redshift of resonance peaks was found when the effect of phonons is taken into consideration or when the donor is moved away from the shell center. These calculations provide us insights when choosing between materials for optoelectronic applications.

Herein, we report a synthetic route capable of producing superparamagnetic, stable and biocompatible glucosamine (GLU) nanocarriers, composed by colloidal iron oxide nanoparticles (ION, ~6 nm) surface-functionalized with GLU dispersed in physiological media (pH 7.2). The route consists first of the preparation of ION by aqueous alkaline co-precipitation of 1:2 Fe(II)/Fe(III) followed by surface treatment with citric acid, activation of acidic groups via carbodiimide intermediary and further amidation using GLU as the amine reactant. Results from cell viability tests performed with human dental pulp tissue cells suggest that ION–GLU nanocolloids are biocompatible and non-toxic for two different concentrations and several hours of incubation. Moreover, optical microscopy shows that ION–GLU adsorbs at the cells walls and also transposes them, reaching cytoplasm and nucleus as well. All findings point out the promising use of ION–GLU as biocompatible nanocarriers for GLU delivery such as in articulation diseases.

In this study, uniaxial tensile loading simulations were performed on several single crystalline copper nanoporous (NP) structures with varying relative density (RD) via molecular dynamics simulations. From the results, two distinctive deformation patterns were observed: structures with a low RD went through coarsening, and structures with a high RD did not. During coarsening, dislocations are nucleated because of the high surface stress induced by the thin ligaments. These dislocations drive the merging of ligaments as well as nodes and lead to an increase in the differences between the size of nodes and ligaments. The disproportional nodes and ligaments result in a lowered strength. In addition, larger nodes provide more favorable circumstances for the formation of sessile dislocations, which hinder the movement of other propagating Shockley partials and result in strain hardening. Subsequently, lower RD structures offer anomalously high strain-hardening potential, whereas high RD structures show better strength but poor deformability. These results help us in better understanding the plastic behavior of NP structures as a function of their RD.

Bioactive dressings which can treat any kind of chronic or acute wounds and can fully replace the conventional gauzes and superabsorbent dressings have proven to be a future market of wound care products in recent times. These dressings are multifunctional, which can effectively combat the wound infection, remove the exudate, promote angiogenesis, and protect the wound from external trauma. Proper selection of bioactive and polymer defines its efficiency. Current research unveils the therapeutic efficacy of curcumin–honey-loaded multilayered polyvinyl alcohol/cellulose acetate electrospun nanofibrous mats as an interactive bioactive wound dressing material. Scanning electron microscopy and Fourier transform infrared spectroscopy analysis infers uniform encapsulation and chemical compatibility of herbal actives and polymer, inside the nanofibrous layers. The as-spun mat shows potential resistance towards Escherichia coli and ∼90% antioxidant activity against diphenyl-picrylhydrazyl (DPPH)–free radical. Additionally, water absorbency, water vapor transmission rate, and wettability analysis show quick and excellent absorption with controlled transmission of wound exudate.

In the past decade, the emergence of high-entropy alloys (HEAs) and other high-entropy materials (HEMs) has brought about new opportunities in the development of novel materials for high-performance applications. In combining solid-solution (SS) strengthening with grain-boundary strengthening, new material systems—nanostructured or nanocrystalline (NC) HEAs or HEMs—have been developed, showing superior combined mechanical and functional properties compared with conventional alloys, HEAs, and NC metals. This article reviews the processing methods, materials, mechanical properties, thermal stability, and functional properties of various nanostructured HEMs, particularly NC HEAs. With such new nanostructures and alloy compositions, many interesting phenomena and properties of such NC HEAs have been unveiled, for example, extraordinary microstructural and mechanical thermal stability. As more HEAs or HEMs are being developed, a new avenue of research is to be exploited. The article concludes with perspectives about future directions in this field.

Modern electronics have been geared toward exploring novel electronic materials that can encompass a broad set of unusual functionalities absent in conventional platforms. In this regard, two-dimensional (2D) transition metal dichalcogenide (TMD) semiconductors are highly promising, owing to their large mechanical resilience coupled with superior transport properties and van der Waals (vdW) attraction-enabled relaxed assembly. Moreover, 2D TMD heterolayers based on chemically distinct constituent layers exhibit even more intriguing properties beyond their mono-component counterparts, which can materialize only when they are manufactured on a technologically practical wafer-scale. This mini-review provides a comprehensive overview of recent progress in exploring wafer-scale 2D TMD heterolayers of various kinds. It extensively surveys a variety of manufacturing strategies and discusses their scientific working principles, resulting 2D TMD heterolayers, their material properties, and device applications. Moreover, it offers extended discussion on remaining challenges and future outlooks toward further improving the material quality of 2D TMD heterolayers in both material and manufacturing aspects.

We show interlayer stacking shifts occur in transition metal dichalcogenides (TMD) bilayers due to the strain introduced during sample heating, and attributed to rippling of one layer relative to the other. The atomic structure of the interlayer stacking is studied using annular dark field scanning transmission electron microscopy with an in situ heating holder. Before heating, bilayers show uniform interlayer stacking of AA′ and AB. When heated, contrast change is seen and associated with interlayer stacking changes at the atomic scale due to ripples. When cooled down to room temperature, these contrast features disappear, confirming it is a reversible process that is not related to defects or vacancies. Because the bottom layer is attached to the in situ heating chip made from Si3N4 and the top layer is in contact with the underlying TMD layer with weak van der Waals interaction, the two layers experience different forces during thermal expansion.

Microstructural evolution of Cu–Nb oxide nanocomposite alloys during ball milling is investigated using a two-step ball-milling approach. In the first step, Cu and Nb powders are milled to create a two-phase alloy comprising a Cu-rich matrix containing a high density of 20- to 30-nm Nb precipitates. In the second step, this nanocomposite is co-milled with CuO, resulting in the reduction of CuO and the oxidation of the Nb nanoprecipitates. Transmission electron microscopy characterization shows that three distinct types of Nb oxide precipitates evolve at different levels of strain. First, nanocrystalline NbO particles (∼10 nm) are formed by dissolved Nb in Cu reacting with oxygen evolved from the CuO. Next, the Nb nanoprecipitates in Cu further reduce CuO to form Nb/Nb oxide and NbO/Nb oxide core–shell inclusions (20–30 nm). These inclusions coalesce during additional milling to form amorphous Nb oxide agglomerates (>700 nm after 50 h). The growth of Nb precipitates during step-one milling, the initial growth of NbO nanoparticles, and the formation of core–shell Nb oxide precipitates during step-two milling are attributed to the convective transport of atoms and clusters combined with shear-induced agglomeration.

The hexagonal boron nitride (h-BN) as a wide bandgap semiconductor is an attractive material for deep ultraviolet (DUV) generation. In this paper we study the prospect of using the stacking hexagonal boron nitride nanosheets (h-BNNS) for generating DUV emission by impact excitation in alternating current driven thin electroluminescence devices (ACTEL) based on BN phosphors having different morphologies. A theoretical approach considered is based on the impact excitation model for generating DUV from stacking h-BNNS under a high electric field. It was found that in the h-BNNS with a thickness of 90 nm biased at 3.33×109 V/m, the quantum yield can reach to 86.8%, and the power conversion efficiency of 1.68%. To achieve the same quantum yield and power conversion efficiency for the ACTEL based on h-BN single crystal, the active phosphor layer should be 2 μm thick when biased at 1.5×108 V/m.

C-reactive protein (CRP) and cardiac troponin I (cTnI) biomolecules represent the earliest enzymes that appear in the blood when a cardiac injury occurs. Real-time and selective detection of these biomarkers is essential for the prediction and detection of cardiovascular diseases at an early stage. Here we report on the label-free specific detection of both proteins at picomolar concentrations using fabricated nanowire-based biosensors. We demonstrate a novel functionalization technique based on the attachment of dibenzocyclooctyne (DBCO)-linked troponin-specific aptamers to azide-functionalized silicon (Si) nanowire (NW) surface. Due to the fast and reliable immobilization of cTnI-specific aptamers and CRP-specific antibodies on the Si NWs, the fabricated devices can rapidly detect target biomolecules demonstrating high sensitivity. We confirm the attachment of proteins to the surface of Si NWs by atomic force microscopy (AFM). Moreover, we demonstrate that nanowire structures of different sizes enable the detection of biomarkers in a wide concentration range (from 1 pg/ml to 1 µg/ml), corresponding to CRP and cTnI elevation levels during the early stage of disease formation.