Engineering Bulk,Layered, Multicomponent Nanostructures with High Energy Density

The precise control of individual components in multicomponent nanostructures is crucial to realizing their fascinating functionalities for applications in electronics, energy‐conversion devices, and biotechnologies. However, this control remains particularly challenging for bulk, multicomponent nanomaterials because the desired structures of the constitute components often conflict. Herein, a strategy is reported for simultaneously controlling the structural properties of the constituent components in bulk multicomponent nanostructures through layered structural design. The power of this approach is illustrated by generating the desired structures of each constituent in a bulk multicomponent nanomaterial (SmCo + FeCo)/NdFeB, which cannot be attained with existing methods. The resulting nanostructure exhibits a record high energy density (31 MGOe) for this class of bulk nanocomposites composed of both hard and soft magnetic materials, with the soft magnetic fraction exceeding 20 wt%. It is anticipated that other properties beyond magnetism, such as the thermoelectric and mechanical properties, can also be tuned by engineering such layered architectures.     

Ultrasensitive Physical,Bio, and Chemical Sensors Derived from 1‐, 2‐, and 3‐D Nanocellulosic Materials

Sensors are of increasing interest since they can be applied to daily life in different areas from various industrial sectors. As a natural nanomaterial, nanocellulose plays a vital role in the development of novel sensors, particularly in the context of constructing multidimensional architectures. This review summarizes the utilization of nanocellulose including cellulose nanofibers, cellulose nanocrystals, and bacterial cellulose for sensor design, mainly focusing on the influence of nanocellulose on the sensing performance of these sensors. Special attention is paid to nanocellulose in different forms (1D, 2D, and 3D) to highlight the impact of nanocellulose constructed structures. The aim is to provide a critical review on the most recent progress (especially after 2017) related to nanocellulose‐containing sensors, since there are significantly increasing research activities in this area. Moreover, the outlook for the development of nanocellulose‐containing sensors is also provided at the end of this work.     

Dry Autoclaving for the Nanofabrication of Sulfides,Selenides, Borides,Phosphides, Nitrides,Carbides, and Oxides

This review compiles various nanostructures fabricated by a distinct “dry autoclaving” approach, where the chemical reactions are carried out without solvents; above the dissociation temperature of the chemical precursor(s) at elevated temperature in a closed reactor. The diversity to fabricate carbides (SiC, Mo₂C, WC), oxides (VOx‐C, ZnO, Eu₂O₃, Fe₃O₄, MoO₂), hexaborides (LaB₆, CeB₆, NdB₆, SmB₆, EuB₆, GdB₆), nitrides (TiN, NbN, TaN), phosphides (PtP₂, WP), sulfides (ZnS, FeS/C, SnS/C, WS₂, WS₂/C), and selenides (Zn_1‐xMn_xSe/C, Cd_1‐xMn_xSe/C), with various shapes and sizes is accounted with plausible applications. This unique single‐step, solvent‐free synthetic process opens up a new route in the growing nanomaterials science; owing to its considerable advantages on the existing approaches.     

Geometrically Structured Nanomaterials for Nanosensors,NEMS, and Nanosieves

Recently, geometrically structured nanomaterials have received great attention due to their unique physical and chemical properties, which originate from the geometric variation in such materials. Indeed, the use of various geometrically structured nanomaterials has been actively reported in enhanced-performance devices in a wide range of applications. Recent significant progress in the development of geometrically structured nanomaterials and associated devices is summarized. First, a brief introduction of advanced nanofabrication methods that enable the fabrication of various geometrically structured nanomaterials is given, and then the performance enhancements achieved in devices utilizing these nanomaterials, namely, i) physical and gas nanosensors, ii) nanoelectromechanical devices, and iii) nanosieves are described. For the device applications, a systematic summary of their structures, working mechanisms, fabrication methods, and output performance is provided. Particular focus is given to how device performance can be enhanced through the geometric structures of the nanomaterials. Finally, perspectives on the development of novel nanomaterial structures and associated devices are presented.     

Use of ionic liquids in synthesis of nanocrystals,nanorods and nanowires of elemental chalcogens

Nanocrystals of elemental chalcogens have been synthesized solvothermally by using elemental chalcogen powder (Se and Te) and NaBH₄ in imidazolium[BMIM]-based ionic liquids as solvents at 180–200°C. Nanorods and nanowires of Se and Te have been obtained when polyethyleneglycol was used as a co-solvent. Se nanowires have been prepared by using an ionic liquid with a small amount of water at room temperature. Sulfur microspheres have been prepared by heating sulfur powder in a mixture of [BMIM][BF₄] and polyethyleneglycol over the temperature range 150–250°C. The nanostructures obtained are single crystalline in all the cases.     

Observation of Extremely Large, Field-Dependent Diamagnetism at 300 K in Certain Disordered Organic Materials

Samples of some nonconjugated polymers exhibiting unusual conducting properties reveal huge, field-dependent diamagnetism at 300 K if concentration of charge carriers exceeds certain threshold about 210¹⁸ cm^–3. Data obtained are consistent with theory of local electronic nanostructures that combine ferromagnetic ground state with some features of superconductors.     

Piezoresistivity,Strain, and Damage Self‐Sensing of Polymer Composites Filled with Carbon Nanostructures

Previous and current research on piezoresistivity of polymer composites filled with carbon nanostructures is reviewed. The review covers the use of the coupled electro‐mechanical response of these materials to self‐sense their strain and damage during mechanical loading. The mechanisms yielding changes in electrical resistance upon mechanical loading in polymer composites filled with carbon nanostructures are first discussed. Published knowledge is then summarized, starting with framework literature on carbon black and graphite and then moving to more recent research on carbon nanotubes, exfoliated graphite, and few‐layer graphene sheets. Piezoresistive studies of polymer nanocomposites with aligned carbon fillers are also reviewed. It is aimed that this review contributes in collecting, organizing, and summarizing the knowledge, foundations, and state of the art on the piezoresistive response of polymer composites filled with different carbon allotropes, providing new perspectives and advancing towards the fast development of smart self‐sensing carbon filled nanocomposites.

     

DNA-Based Plasmonic Heterogeneous Nanostructures: Building,Optical Responses,and Bioapplications

The integration of multiple functional nanoparticles into a specific architecture allows the precise manipulation of light for coherent electron oscillations. Plasmonic metals-based heterogeneous nanostructures are fabricated by using DNA as templates. This comprehensive review provides an overview of the controllable synthesis and self-assembly of heterogeneous nanostructures, and analyzes the effects of structural parameters on the regulation of optical responses. The potential applications and challenges of heterogeneous nanostructures in the fields of biosensors and bioanalysis, in vivo monitoring, and phototheranostics are discussed.     

Fatigue‐Free,Electrically Reliable Copper Electrode with Nanohole Array

Design and fabrication of reliable electrodes is one of the most important challenges in flexible devices, which undergo repeated deformation. In conventional approaches, mechanical and electrical properties of continuous metal films degrade gradually because of the fatigue damage. The designed incorporation of nanoholes into Cu electrodes can enhance the reliability. In this study, the electrode shows extremely low electrical resistance change during bending fatigue because the nanoholes suppress crack initiation by preventing protrusion formation and damage propagation by crack tip blunting. This concept provides a key guideline for developing fatigue‐free flexible electrodes.     

Improving Biocompatibility of Implantable Metals by Nanoscale Modification of Surfaces: An Overview of Strategies,Fabrication Methods,and Challenges

The human body is an intricate biochemical–mechanical system, with an exceedingly precise hierarchical organization in which all components work together in harmony across a wide range of dimensions. Many fundamental biological processes take place at surfaces and interfaces (e.g., cell–matrix interactions), and these occur on the nanoscale. For this reason, current health‐related research is actively following a biomimetic approach in learning how to create new biocompatible materials with nanostructured features. The ultimate aim is to reproduce and enhance the natural nanoscale elements present in the human body and to thereby develop new materials with improved biological activities. Progress in this area requires a multidisciplinary effort at the interface of biology, physics, and chemistry. In this Review, the major techniques that have been adopted to yield novel nanostructured versions of familiar biomaterials, focusing particularly on metals, are presented and the way in which nanometric surface cues can beneficially guide biological processes, exerting influence on cellular behavior, is illustrated. Frontispiece adapted from Reference 94 .

     

Highly Symmetric,Self-Assembling 3D DNA Crystals with Cubic and Trigonal Lattices

The rational design of nanoscopic DNA tiles has yielded highly ordered crystalline matter in 2D and 3D. The most well-studied 3D tile is the DNA tensegrity triangle, which is known to self-assemble into macroscopic crystals. However, contemporary rational design parameters for 3D DNA crystals nearly universally invoke integer numbers of DNA helical turns and Watson–Crick (WC) base pairs. In this study, 24-bp edges are substituted into a previously 21-bp (two helical turns of DNA) tensegrity triangle motif to explore whether such unconventional motif can self-assemble into 3D crystals. The use of noncanonical base pairs in the sticky ends results in a cubic arrangement of tensegrity triangles with exceedingly high symmetry, assembling a lattice from winding helical axes and diamond-like tessellation patterns. Reverting this motif to sticky ends with Watson–Crick pairs results in a trigonal hexagonal arrangement, replicating this diamond arrangement in a hexagonal context. These results showcase that the authors can generate unexpected, highly complex, pathways for materials design by testing modifications to 3D tiles without prior knowledge of the ensuing symmetry. This study expands the rational design toolbox for DNA nanotechnology; and it further illustrates the existence of yet-unexplored arrangements of crystalline soft matter.     

Surface-Enhanced Infrared Absorption Spectroscopic Investigation of Benzamide Thin-Film Formation,Stability, and Catalysis on Gold and Silver Nanostructures

Benzamide (BA), a simple molecule that can be utilized in material chemistry and chemical engineering as well as pharmacological and medicinal applications, has been characterized on vacuum-evaporated silver and gold nanostructures with SEIRA spectroscopy and density functional theory (DFT) calculation under ambient conditions. Assessments of thin-film formation on the metal nanoparticles indicated that BA readily ionizes in both the monolayer and multilayer when deposited from nonpolar solvents. Investigation on the stability of BA on metal nanostructures showed that unionized BA desorbs from the nanosurface within days while ionized BA on silver nanostructures can undergo further oxidation over time, producing surface-adsorbed phenyl isocyanate. Also, a brief investigation on variables influencing IR signal enhancement provided by the metal nanosurfaces was conducted; in general, gold nanostructures provide more enhancement than silver.     

Highly Polar Linkers (Urea,Carbamate, Thiocarbamate) for Superoleophobic/Superhydrophobic or Oleophobic/Hydrophilic Properties

Due to the much lower surface tension of oils in comparison to water, it is extremely difficult to obtain superoleophobic properties and also both oleophobic and hydrophilic properties. While the obtaining of superoleophobic properties needs extremely complex surface structures such as reentrant structures to impede the oil wetting, the obtaining of both oleophobic and hydrophilic properties needs the use of both oleophobic materials (fluorinated materials) and hydrophilic materials (charged or polar species). Here, by electropolymerization of original 3,4‐ethylenedioxythiophene derivatives containing both fluorinated chains (C₈F₁₇, C₆F₁₃, or C₄F₉) and highly polar linkers (thiocarbamate SCONH, carbamate OCONH, and urea NHCONH), the possibility to obtain superoleophobic properties and also both oleophobic and hydrophilic properties is reported for the first time. More precisely superoleophobic properties are obtained with different fluorinated chain lengths and linkers while the obtaining of both oleophobic and hydrophilic properties is possible only with the most polar urea NHCONH linkers.     

Fabrication of nanoscale rings, dots, and rods by combining shadow nanosphere lithography and annealed polystyrene nanosphere masks

The application of shadow nanosphere lithography for the preparation of large-area, two-dimensional, metallic nanostructures of different shape is described. Through changing the mask morphology by temperature processing and varying the evaporation conditions, particles with morphologies such as rings, rods, and dots have been produced. This process allows outstanding control of the size and morphology of the particles. The efficient technique is shown to scale down the size of metallic nanoparticles from 200 to 30 nm, while preserving the original nanosphere spacing and order. The 150-nm-diameter Fe rings produced by this method show ferromagnetic behavior, which was predicted by theoretical simulation. All the experimental results were confirmed by computer simulations, which also showed the possibility of creating periodic arrays of any other geometrical shape.