Self‐Assembled Graphene–Enzyme Hierarchical Nanostructures for Electrochemical Biosensing

The self‐assembly of sodium dodecyl benzene sulphonate (SDBS) functionalized graphene sheets (GSs) and horseradish peroxidase (HRP) by electrostatic attraction into novel hierarchical nanostructures in aqueous solution is reported. Data from scanning electron microscopy, high‐resolution transmission electron microscopy, and X‐ray diffraction demonstrate that the HRP–GSs bionanocomposites feature ordered hierarchical nanostructures with well‐dispersed HRP intercalated between the GSs. UV‐vis and infrared spectra indicate the native structure of HRP is maintained after the assembly, implying good biocompatibility of SDBS‐functionalized GSs. Furthermore, the HRP–GSs composites are utilized for the fabrication of enzyme electrodes (HRP–GSs electrodes). Electrochemical measurements reveal that the resulting HRP–GSs electrodes display high electrocatalytic activity to H₂O₂ with high sensitivity, wide linear range, low detection limit, and fast amperometric response. These desirable electrochemical performances are attributed to excellent biocompatibility and superb electron transport efficiency of GSs as well as high HRP loading and synergistic catalytic effect of the HRP–GSs bionanocomposites toward H₂O₂. As graphene can be readily non‐covalently functionalized by “designer” aromatic molecules with different electrostatic properties, the proposed self‐assembly strategy affords a facile and effective platform for the assembly of various biomolecules into hierarchically ordered bionanocomposites in biosensing and biocatalytic applications.     

Characterization,Cathodoluminescence, and Field‐Emission Properties of Morphology‐Tunable CdS Micro/Nanostructures

High‐quality, uniform one‐dimensional CdS micro/nanostructures with different morphologies—microrods, sub‐microwires and nanotips—are fabricated through an easy and effective thermal evaporation process. Their structural, cathodoluminescence and field‐emission properties are systematically investigated. Microrods and nanotips exhibit sharp near‐band‐edge emission and broad deep‐level emission, whereas sub‐microwires show only the deep‐level emission. A significant decrease in a deep‐level/near‐band‐edge intensity ratio is observed along a tapered nanotip towards a smaller diameter part. This behavior is understood by consideration of defect concentrations in the nanotips, as analyzed with high‐resolution transmission electron microscopy. Field‐emission measurements show that the nanotips possess the best field‐emission characteristics among all 1D CdS nanostructures reported to date, with a relatively low turn‐on field of 5.28 V µm^?1 and the highest field‐enhancement factor of 4 819. The field‐enhancement factor, turn‐on and threshold fields are discussed related to structure morphology and vacuum gap variations under emission.     

Stimuli‐Responsive Hybridized Nanostructures

Through innovative nanosynthesis techniques and advanced surface‐passivation methods, diversified luminescent nanocrystals, like quantum dots, metal nanoclusters, carbon dots, and upconversion nanoparticles, are produced successfully to exhibit greatly improved performance in various applications, due to their color tunability and resistance to photobleaching. Their further hybridization with stimuli‐responsive polymers endows the resultant nanohybrids with unique smart functions, which can reversibly respond to external stimuli or environmental changes via alternation in luminescence. Due to their multifunctional properties, these responsive luminescent nanohybrids are attracting more and more interest in foundation research and promising applications recently. Here, important developments and achievements made in this emerging field are summarized to highlight the integration concepts and fabrication methods for luminescent nanohybrids, and their special responsive functions to temperature, pH, fields, and analytes. At the same time, their smart applications are also overviewed for demonstrating novel actions of responsive nanohybrids via various intelligent operations. The aim is to understand and accelerate more advanced developments in creating varied and intelligent nanosystems, and provide perspectives to promote a further revolution of smart materials and technology.     

Rapid Degradation of Azo Dye by Fe‐Based Metallic Glass Powder

The outstanding efficiency of Fe‐based metallic glass powders in degrading organic water contaminants is reported. While the glassy alloy contains 24% chemically inactive metalloid elements, the powders are capable to completely decompose the C₃₂H₂₀N₆Na₄O₁₄S₄ azo dye in aqueous solution in short time, about 200 times faster than the conventional Fe powders. The metastable thermodynamic nature and the particle surface topography are the major factors controlling the chemical performance of the metallic glass. Our findings may open a new opportunity for functional applications of metallic glasses.     

“Ship‐in‐a‐Bottle” Growth of Noble Metal Nanostructures

Noble metal nanostructures are grown inside hollow mesoporous silica microspheres using “ship‐in‐a‐bottle” growth. Small Au seeds are first introduced into the interior of the hollow microspheres. Au nanorods with synthetically tunable longitudinal plasmon wavelengths and Au nanospheres are obtained through seed‐mediated growth within the microspheres. The encapsulated Au nanocrystals are further coated with Pd or Pt shells. The microsphere‐encapsulated bimetallic core/shell nanostructures can function as catalysts. They exhibit high catalytic performance and their stability is superior to that of the corresponding unencapsulated core/shell nanostructures in the catalytic oxidation of o‐phenylenediamine with hydrogen peroxide. Therefore, these hollow microsphere‐encapsulated metal nanostructures are promising as recoverable and efficient catalysts for various liquid‐phase catalytic reactions.     

Three‐Dimensional Nanostructures for Photonics

Recent progress in direct laser writing of three‐dimensional (3D) polymer nanostructures for photonics is reviewed. This technology has reached a level of maturity at which it can be considered as the 3D analogue of planar electron‐beam lithography. Combined with atomic‐layer deposition and/or chemical‐vapor deposition of dielectrics—the 3D analogues of planar evaporation technologies, the 3D polymer templates can be converted or inverted into 3D high‐refractive‐index‐contrast nanostructures. Examples discussed in this review include positive and inverse 3D silicon‐based woodpile photonic crystals possessing complete photonic bandgaps, novel optical resonator designs within these structures, 3D chiral photonic crystals for polarization‐state manipulation, and 3D icosahedral photonic quasicrystals. The latter represent a particularly complex 3D nanostructure.     

Recent Developments in One‐Dimensional Inorganic Nanostructures for Photodetectors

With large surface‐to‐volume ratios and Debye length comparable to their small sizes, one‐dimensional inorganic nanostructures have extensively been investigated and widely used to fabricate high‐performance nano­scale electronic and optoelectronic devices. This feature article reviews the state‐of‐the‐art research activities that focus on the one‐dimensional inorganic nanostructures and their photodetector applications. It begins with a survey of one‐dimensional inorganic nanostructures and the fundamentals of photodetectors. Some remarkable photoresponse characteristics are then presented, which are organized into sections covering several kinds of important nanostructures, such as ZnO, V₂O₅, ZnS, In₂Se₃, InSe, CdS, CdSe, ZnSe, Sb₂Se₃, ZrS₂, Ag₂S, and Zn_xCd_1‐xSe. Each section describes the corresponding photodetective properties in detail. Finally, the article concludes with some perspectives and outlook on the future developments in the field.     

Engineering of Facets,Band Structure,and Gas‐Sensing Properties of Hierarchical Sn2+‐Doped SnO2 Nanostructures

Hierarchical SnO₂ nanoflowers, assembled from single‐crystalline SnO₂ nanosheets with high‐index (11$ \bar 3 $ ) and (10$ \bar 2 $ ) facets exposed, are prepared via a hydrothermal method using sodium fluoride as the morphology controlling agent. Formation of the 3D hierarchical architecture comprising of SnO₂ nanosheets takes place via Ostwald ripening mechanism, with the growth orientation regulated by the adsorbate fluorine species. The use of Sn(II) precursor results in simultaneous Sn²⁺ self‐doping of SnO₂ nanoflowers with tunable oxygen vacancy bandgap states. The latter further results in the shifting of semiconductor Fermi levels and extended absorption in the visible spectral range. With increased density of states of Sn²⁺‐doped SnO₂ selective facets, this gives rise to enhanced interfacial charge transfer, that is, high sensing response, and selectivity towards oxidizing NO₂ gas. The better gas sensing performance over (10$ \bar 2 $ ) compared to (11$ \bar 3 $ ) faceted SnO₂ nanostructures is elucidated by surface energetic calculations and Bader analyses. This work highlights the possibility of simultaneous engineering of surface energetics and electronic properties of SnO₂ based materials.     

Ductile Biodegradable Mg‐Based Metallic Glasses with Excellent Biocompatibility

Magnesium‐based metallic glasses (MMGs) show intriguing potentials for application as implantable biomaterials owing to their disordered atomic structure, good biodegradability, low elastic modulus, high strength, and large elasticity. However, despite of all these advantages, their brittleness is their Achilles’ heel, which severely limits their application as biomedical materials. In the current study, a significantly improved ductility of MMGs under bending and tensile loading through minor alloying with rare‐earth element ytterbium (Yb) at an atomic concentration of 2 and 4% is reported. The enhanced ductility is attributed to the increased density of shear bands close to fracture end and larger plastic zones on the fracture surface. In comparison with that of Yb‐free control, in vitro cell culture study confirms an improved biocompatibility of MMGs alloyed with Yb as determined by MTT, live‐dead, and cytoskeleton staining assays, respectively.     

Tunable Guided‐Mode Resonance Grating Filter

The optical characteristics of shallow 2D nanostructured polycarbonate samples are presented. Tunable guided‐mode resonance filters are experimentally demonstrated for the visible spectral range when functional coatings are applied to 2D nanostructures by means of atomic layer deposition. The wavelength position of the reflection peaks can be easily tuned in a broad range (>150 nm) through rotation of the optical element around the axis normal to the substrate without changing the rest of the optical setup. Rigorous coupled wave approach simulation of model systems is performed to obtain insight into the complexity of the optical properties of these systems. The photonic nanostructures presented here are promising optics for application in ultra‐compact, portable, miniaturized optical systems.     

Suppression of Catastrophic Failure in Metallic Glass–Polyisoprene Nanolaminate Containing Nanopillars

One considerable concern in metallic glass is enhancing ductility by suppressing catastrophic failure by the instantaneous propagation of shear bands. Compressed nanopillars with alternating CuZr metallic glass and polyisoprene nanolaminates exhibit >30% enhancement in plastic flow, as compared with monolithic glass, without sacrifice of strength. A suppression of stochastic strain burst signature in these metallic glass‐polymer composites is reported, which is an undesirable characteristic ubiquitously present in monolithic metallic glass and in metallic glass‐metal composites. The intermittent stochastic signature is quantified in each metallic glass‐containing nanolaminate system by constructing histograms of burst size distributions and provide theoretical foundation for each behavior. The exceptional mechanical properties emergent in these MG‐polymer nanolaminate composites are attributed to the combination of nanometer size‐induced shear band suppression in metallic glasses and the damping capability of the polyisoprene layers.     

Self‐Assembled Sugar‐Substituted Perylene Diimide Nanostructures with Homochirality and High Gas Sensitivity

A new symmetrical sugar‐based perylenediimide derivative PTCDI‐BAG is synthesized and its aggregate morphologies and formation mechanisms are studied in detail in the mixed solvent system water/N,N‐dimethylformamide (H₂O/DMF) with changing volume ratios. PTCDI‐BAG molecules self‐assemble into planar ribbons in 20/80 and 40/60 H₂O/DMF (v/v), but their chiralities are opposite according to recorded circular dichroism (CD) spectra. With a further increase of the water content, only left‐handed helical nanowires are obtained in 60/40 and 80/20 H₂O/DMF (v/v) mixtures. By combining density functional theory (DFT) calculations with the experimental investigations, it is proposed that kinetic and thermodynamic factors play key roles in tuning PTCDI‐BAG structures and helicity. The formation of the ribbon is thermodynamically controlled in the 20/80 H₂O/DMF system, but kinetically controlled nucleation followed by thermodynamically controlled self‐assembly plays the governing roles for the formation of nanoribbons in 40/60 H₂O/DMF. Devices based on single nanoribbons for hydrazine sensing exhibit better performance than nanofiber bundles obtained in this study and achiral nanostructures reported in previous study. This study not only provides an elaborated route to tuning the structures and helicity of PTCDI molecules, but also provides new possibilities for the construction of high‐performance nanodevices.     

Gold Nanobipyramid‐Supported Silver Nanostructures with Narrow Plasmon Linewidths and Improved Chemical Stability

Silver nanostructures with narrow plasmon linewidths and good chemical stability are strongly desired for plasmonic applications. Herein, a facile method is discussed for the preparation of Ag nanostructures with narrow plasmon linewidths and improved chemical stability through Ag overgrowth on monodispersed Au nanobipyramids. Structural evolution from bipyramid through rice to rod is observed, indicating that Ag atoms are preferentially deposited on the side surfaces of Au nanobipyramids. The resultant (Au nanobipyramid)@Ag nanostructures possess high size and shape uniformities, and much narrower plasmon linewidths than other Ag nanostructures. The spectral evolution of the supported Ag nanostructures is ascertained by both ensemble and single‐particle characterizations, together with electrodynamic simulations. Systematic measurements of the refractive index sensing characteristics indicate that Ag nanostructures in this study possess high index sensitivities and figure of merit (sensitivity divided by linewidth) values. Moreover, Ag nanostructures in this study exhibit greatly improved chemical stability. The superior sensing capability of Ag nanostructures in this study is further demonstrated by the detection of sulfide ions at a relatively low detection limit. Taken together, results of this study show that the Au‐nano­bipyramid‐supported Ag nanostructures will be an outstanding candidate for the design of ultrasensitive plasmonic sensing devices as well as for the development of other plasmon‐enabled technological applications.     

Low‐Dimensional Transition Metal Dichalcogenide Nanostructures Based Sensors

Two‐dimensional (2D) transition metal dichalcogenides (TMDs) nanostructures have been widely applied in environmental and biological analysis, biomedicine, electronic devices, and hydrogen evolution catalysis. Meanwhile, this excitement in 2D TMDs has spilled over to their counterparts of different dimensionalities like one‐dimensional (1D) and zero‐dimensional (0D) TMDs nanostructures. Eventual physical and chemical properties of TMDs nanostructures still remain to be highly dependent on their dimensionalities and size scale, and recently creatively exploring these physical and chemical properties is extremely impactful for the sensing field of TMD nanomaterials. Herein, we review a wide range of sensing applications based on not only graphene‐like 2D TMDs nanostructures but also the rapidly emerging subclasses of 1D, and 0D TMDs nanostructures. Their unique and interesting structures, excellent properties, and valid preparation methods are also included and the analytical objectives, ranging from heavy metal ions to small molecules, from DNA to proteins, from liquids to even vapors, can be met with extremely high selectivity and sensitivity. We have also analyzed our current understanding of 0D and 1D TMDs nanostructures and learning from graphene with the goal of contributing fresh ideas to the overall development of more advanced future TMDs based sensors.     

Shell-Isolated Plasmonic Nanostructures for Biosensing,Catalysis, and Advanced Nanoelectronics

Shell-isolated nanostructures, consisting of an inert shell and a plasmonic core, have recently been intensively explored for biosensing, catalysis, and nanoelectronics applications owing to their functional shells and unique plasmonic properties. Such designer shell-isolated plasmonic nanostructures possess the potential to improve the detectability of biosensors and provide powerful platforms to explore in-depth plasmon enhancement principles and finally boost significantly their photo(electro)catalytic efficiency. In addition, such structural optimization and interface nanoengineering promote solid developments of advanced nanoelectronics toward real applications, revealing new electron transport mechanisms and enabling exploration of new functional and integrated optoelectronic devices. In this overview, the state-of-the-art progresses of shell-isolated plasmonic nanostructures (SHIPNSs) in the field of biosensing, photo(electro)catalysis, and nanoelectronics is summarized, focusing on the superiority of the core–shell materials in exploration of biosensing, catalytic enhancement mechanisms, and electron transport principles. A brief overview of synthetic methods is introduced, and then the significant importance of shell-isolated nanomaterials in fabrication and promising direction for future development and challenges are discussed.     

Carbon‐Nanotube‐Reinforced Zr‐Based Bulk Metallic Glass Composites and Their Properties

In this paper, we systematically report the preparation of carbon‐nanotube (CNT)‐reinforced Zr‐based bulk metallic glass (BMG) composites. The physical and mechanical properties of the composites were investigated. Compressive testing shows that the composites still display high fracture strength. Investigation also shows that the composites have strong ultrasonic attenuation characteristics and excellent wave absorption ability. The strong wave absorption implies that CNT‐reinforced Zr‐based BMG composites, besides their excellent mechanical properties, may also have significant potential for applications in shielding acoustic sound or environmental noise.     

2D Chiroptical Nanostructures for High‐Performance Photooxidants

Modulation of the chirality of solid‐like nanoscale membranous structures used as selective photooxidants is an important goal of chemical and materials science. Here, the fabrication of a chiral plasmonic nanoparticle monolayer film which is a highly selective photooxidant under circularly polarized light (CPL) in the visible‐light region is reported. The chiroptical activity of the film can be controlled by altering the amount and stereochemistry of amino acids. The experiments disclose that this stable and reusable catalyst is active in the selective oxidation of glucose enantiomers and CPL of opposite polarization gives around 10.3‐fold increase in conversion rates. The results reveal that the handedness of polarized light dominates the catalytic activity of the chiral film. It is demonstrated that the specific chiral binding of the amino acid ligands and the local field enhancement in the light‐limited regime regulates the selective photocatalytic performance, as confirmed by first‐principles density functional theory and physical field simulations. With the catalyst's signature ability for chiral recognition and switching of handedness of polarized light, the discovery provides a foundation for designing and tailoring chiral inorganic photooxidants. This research also sets an example for the development of light–matter interactions and polarized optics.     

Hierarchical Self‐assembly of Microscale Cog‐like Superstructures for Enhanced Performance in Lithium‐Ion Batteries

Assembling complex nanostructures on functional substrates such as electrodes promises new multi‐functional interfaces with synergetic properties capable of integration into larger‐scale devices. Here, we report a microemulsion‐mediated process for the preparation of CuO/Cu electrodes comprising a surface layer of a densely packed array of unusual cog‐shaped CuO microparticles with hierarchical nanofilament‐based superstructure and enhanced electrochemical performance in lithium‐ion batteries. The CuO particles are produced by thermolysis of Cu(OH)₂ micro‐cog precursors that spontaneously assemble on the copper substrate when the metal foil is treated with a reactive oil‐based microemulsion containing nanometer‐scale aqueous droplets. The formation of the hierarchical superstructure improves the coulombic efficiency, specific capacity, and cycling performance compared with anodes based on CuO nanorods or polymer‐blended commercial CuO/C black powders, and the values for the initial discharge capacity (1052 mA h g^?1) and reversible capacity (810 m A h g^?1) are higher than most copper oxide materials used in lithium‐ion batteries. The results indicate that a fabrication strategy based on self‐assembly within confined reaction media, rather than direct synthesis in bulk solution, offers a new approach to the design of electrode surface structures for potential development in a wide range of materials applications.