Variety Of Nanostructures Research Articles

Facile preparation of diverse copper oxide nanostructures and their characterization

Copper oxide (CuO) nanostructures, such as nanoshuttles, nanodisks and nanoparticles are synthesized by simple hydrothermal and wet chemical methods. The CuO nanostructures are prepared by thermal dehydration of Cu(OH)2·H2O crystal hydrate without any additives. The CuO nanostructures are characterized by energy dispersive X-ray absorption spectroscopy (EDAS), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, UV-vis spectroscopy and X-ray diffraction (XRD) techniques. The SEM images show that diameter of CuO nanoshuttles ranges from 300–400 nm and length of ∼1 μm. The platelet-like porous CuO nanoparticles have thickness of 0.2–0.4 μm and width of 0.5–1.5 μm. The CuO nanodisks have diameter of 500–700 nm and thickness of 60–120 nm. The EDAS analysis confirms purity of CuO samples. The FTIR spectra of CuO nanostructures exhibit that the vibration peaks correspond to stretching vibrations of CuO bond.

Self-Assembly of Amphiphiles into Vesicles and Fibrils: Investigation of Structure and Dynamics Using Spectroscopy and Microscopy Techniques.

Amphiphiles are a class of molecules which are known to assemble into a variety of nanostructures. The understanding and applications of self-assembled systems are based on what has been learned from biology. Among the vast number of self-assemblies, in this article, we have described the formation, characterization, and dynamics of two important biologically inspired assemblies: vesicles and fibrils. Vesicles, which can be classified into several categories depending on the sizes and components, are of great interest due to their potential applications in drug delivery and as nanoscale reactors. The structure and dynamics of vesicles can also mimic the complex geometry of the cell membrane. On the other hand, the self-assembly of proteins, peptides, and even single amino acids leads to a number of degenerative disorders. Thus, a complete understanding of these self-assembled systems is necessary. In this article, we discuss recent work on vesicular aggregates composed of phospholipids, fatty acids, and ionic as well as nonionic surfactants and single amino acid-based fibrils such as phenylalanine and tyrosine. Beside the characterization, we also emphasize the excited-state dynamics inside the aggregates for a proper understanding of the organization, reactivity, and heterogeneity of the aggregates.

Tale of Alkyl Chains: Chain-Length Effect-Directed Formation of Complex Self-Assembly Behaviors at the Liquid/Solid Interface for Unsymmetrically Substituted Fluorenone Derivatives

Structural diversity induced by the chain-length effect in the field of two-dimensional self-assembly has gained immense attention because of its potential application in nanoscience and crystal engineering. By modifying the two side chains in a certain molecule by one carbon atom and gradually increasing the alkyl chain length, seven fluorenone derivatives (F–CnCn+1, n = 11–17) were synthesized. At the 1-octanoic acid/graphite interface, diverse nanostructures of hexamer-I, tetramer, dimer, alternate-I, hexamer-II, and alternate-II were recorded. The arrangement for the two side chains which differ from each other only by one carbon atom was discussed from the viewpoint of thermodynamics and kinetics. The alkyl chain in the same length was speculated to show selective identification during the self-assembly process, which was favored in consideration of dense packing and maximizing the molecular interplay. Three forces such as dipole–dipole, hydrogen bonding, and van der Waals (vdWs) interactions coopera...

A general soft-enveloping strategy in the templating synthesis of mesoporous metal nanostructures

Metal species have a relatively high mobility inside mesoporous silica; thus, it is difficult to introduce the metal precursors into silica mesopores and suppress the migration of metal species during a reduction process. Therefore, until now, the controlled growth of metal nanocrystals in a confined space, i.e., mesoporous channels, has been very challenging. Here, by using a soft-enveloping reaction at the interfaces of the solid, liquid, and solution phases, we successfully control the growth of metallic nanocrystals inside a mesoporous silica template. Diverse monodispersed nanostructures with well-defined sizes and shapes, including Ag nanowires, 3D mesoporous Au, AuAg alloys, Pt networks, and Au nanoparticle superlattices are successfully obtained. The 3D mesoporous AuAg networks exhibit enhanced catalytic activities in an electrochemical methanol oxidation reaction. The current soft-enveloping synthetic strategy offers a robust approach to synthesize diverse mesoporous metal nanostructures that can be utilized in catalysis, optics, and biomedicine applications.

Recent Advances of Plasmonic Organic Solar Cells: Photophysical Investigations.

The surface plasmon resonance (SPR) of metallic nanomaterials, such as gold (Au) and silver (Ag), has been extensively exploited to improve the optical absorption, the charge carrier transport, and the ultimate device performances in organic photovoltaic cells (OPV). With the incorporation of diverse metallic nanostructures in active layers, buffer layers, electrodes, or between adjacent layers of OPVs, multiple plasmonic mechanisms may occur and need to be distinguished to better understand plasmonic enhancement. Steady-state photophysics is a powerful tool for unraveling the plasmonic nature and revealing plasmonic mechanisms such as the localized surface plasmon resonance (LSPR), the propagating plasmon-polariton (SPP), and the plasmon-gap mode. Furthermore, the charge transfer dynamics in the organic semiconductor materials can be elucidated from the transient photophysical investigations. In this review article, the basics of the plasmonic mechanisms and the related metallic nanostructures are briefly introduced. We then outline the recent advances of the plasmonic applications in OPVs emphasizing the linkage between the photophysical properties, the nanometallic geometries, and the photovoltaic performance of the OPV devices.

Multifunctional Self-Assembling Peptide-Based Nanostructures for Targeted Intracellular Delivery: Design, Physicochemical Characterization, and Biological Assessment.

Peptide amphiphiles (PAs), consisting of a hydrophobic alkyl chain covalently bound to a hydrophilic peptide sequence, possess a versatile molecular design due to their combined self-assembling features of amphiphile surfactants and biological functionalities of peptides. Through rational design, PAs can self-assemble into a variety of nanostructures with controlled shape, size, and biological functionality to deliver therapeutic and imaging agents to target cells. Here, we describe principles to design multifunctional PAs for self-assembly into micellar nanostructures and targeted intracellular delivery. The PA micelles are designed to display a tumour targeting sequence on their surfaces and direct their interactions with specific cells. This targeting sequence includes an enzymatic sensitive sequence that can be cleaved upon exposure to matrix metalloproteinase 2 (MMP-2), an enzyme overexpressed in tumor environment, allowing the presentation of a cell-penetrating domain. The presentation of this domain will then facilitate the delivery of therapeutics for cancer treatment inside targeted cells. Methods to characterize the key physicochemical properties of PAs and their assemblies, including secondary structure, critical micelle concentration, shape and size, are described in detail. The enzyme responsiveness of PA assemblies is described with respect to their degradation by MMP-2. Protocols to evaluate the cytotoxicity and cellular uptake of the micellar carriers are also included.

A thermo-/pH-responsive hydrogel (PNIPAM-PDMA-PAA) with diverse nanostructures and gel behaviors as a general drug carrier for drug release

The aim of this research was to develop thermo- and pH-responsive hydrogels based on H-bonds for the sustained release of the small-molecule model drug Methylene Blue (MB).

Time dependent aggregation induced emission enhancement and the study of molecular packing in closely related azo-phenol BODIPY species.

Fluorescent azo-phenol BODIPYs (1-3) have been obtained by the substituent (-OCH3/-CH3) directed synthesis of ortho (L1) and para (L2-L3) azo-phenol aldehydes. These display aggregation caused quenching (ACQ, 1) and aggregation induced emission enhancement (AIEE, 2 and 3) depending on the position of azo relative to the phenolic hydroxyl group. An intriguing time dependent morphological transition from nanospheres to ordered nanorods and subsequent emission changes in AIEE active azo-phenol BODIPYs have been successfully realized by time dependent fluorescence, scanning electron (SEM), transmission electron (TEM) and fluorescence optical microscopy (FOM) studies. The existence of one-dimensional (1D) nanorods as ultimate species in these compounds (2-3) has been supported by crystal packing patterns. Diverse aggregated forms and hierarchical nanostructures have been related to variable extents of fluorescence enhancement. The plausible charge transfer process and its role in AIEE have been supported by DFT studies.

Design of diverse nanostructures by hydrothermal and microemulsion routes for electrochemical water splitting.

Hydrothermal and microemulsion methods are low temperature methods used to obtain nanostructures of definite morphologies, sizes, facet termination and other structural features which result in the corresponding unique response to chemical, electrochemical or photochemical stimuli. An efficient catalyst to electrochemically split water to produce hydrogen and oxygen is of scientific, economic and societal relevance, especially due to the abundance of the starting material, water, and due to the product hydrogen, which is an ideal fuel, due to its highest mass density and clean combustion in air. In this review we focus on the hydrogen evolution reaction, HER, and the oxygen evolution reaction, OER, activity of the electrocatalysts produced by hydrothermal or microemulsion methods. The variation in electrochemical response resulting from the unique shape, composition and nano-architecture is discussed. Broadly, the catalysts were categorized as binary and ternary metal alloys as well as metal chalcogenides and oxides. This compilation would aid in the design of more effective water splitting electrocatalysts as well as in the selection of appropriate candidates for advanced mechanistic studies.

Shape-Controlled 3D Periodic Metal Nanostructures Fabricated via Nanowelding.

A novel method for fabricating 3D metallic nanostructures to be used in polarized color filters based on nanoimprint lithography, electron-beam evaporation, and nanowelding is proposed. The shape of the nanostructures can be controlled by adjusting the temperature for the nanowelding process. Ag nanowires deposited on polymer patterns are accumulated by the nanowelding process to build up diverse 3D nanostructures. The morphologies of the fabricated 3D nanostructures are analyzed using scanning electron microscopy, atomic force microscopy, and focused ion beam; the heating temperature is varied from 90 to 130 °C in steps of 10 °C. In order to analyze the recrystallization phenomenon after welding, transmission electron microscopy is utilized. The 3D metallic nanostructure has different morphologies and optical properties corresponding to welding temperature conditions and accumulated layer thicknesses. Based on preliminary experimental results, the process parameters are optimized and a polarized color filter is fabricated. Optical characteristics of the filter are evaluated using polarizer and spectrometer. Through this work, it is shown that the proposed method is an effective way to realize various 3D metallic nanostructures for special optical properties, therefore the method based on nanowelding can be utilized in fabrication of functional metamaterials, optical filters, biosensors, and others.

Two-dimensional assembly of giant molecules

This mini review summarizes recent progress on two-dimensional (2D) self-assembly of giant molecules. Two critical factors with significant impact on the formation of nanostructure are highlighted, i.e., the dimensional constraint of 2D geometry, and the conformational constraint imposed the rigid molecular nanoparticles (MNPs). Diverse 2D nanostructures have been fabricated in condensed state and solution by rational molecular design. The collective secondary interactions between functional groups on the periphery of the MNPs and their persistent shape, together with the dimensional limit, change the free energy landscape and lead to unconventional nanostructures. The unique molecular properties of giant molecules endow these 2D structures with promising technological applications.

Polymorphic design of DNA origami structures through mechanical control of modular components

Scaffolded DNA origami enables the bottom-up fabrication of diverse DNA nanostructures by designing hundreds of staple strands, comprised of complementary sequences to the specific binding locations of a scaffold strand. Despite its exceptionally high design flexibility, poor reusability of staples has been one of the major hurdles to fabricate assorted DNA constructs in an effective way. Here we provide a rational module-based design approach to create distinct bent shapes with controllable geometries and flexibilities from a single, reference set of staples. By revising the staple connectivity within the desired module, we can control the location, stiffness, and included angle of hinges precisely, enabling the construction of dozens of single- or multiple-hinge structures with the replacement of staple strands up to 12.8% only. Our design approach, combined with computational shape prediction and analysis, can provide a versatile and cost-effective procedure in the design of DNA origami shapes with stiffness-tunable units.

Phase behaviors of a mixture of two kinds of Pluronic triblock copolymers in aqueous solution

A new method to easily derive the phase transition of amphiphilic block copolymer in aqueous solution is suggested in this study. Using two kinds of Pluronic triblock copolymers, which have different mass fractions of the hydrophilic part of the block copolymer, the mixed block copolymers in aqueous solution self-assembled into a variety of nanostructures. Small angle neutron scattering revealed that the block copolymer complex formed spheres, cylinders, and vesicles depending on both the concentration of another Pluronic block copolymer (Pluronic PE6200) as an additive and temperature. This phase behavior can be easily explained in terms of the hydrophobicity of the block copolymer by increasing its effective hydrophobic moiety and temperature.

Fabrication of highly ordered 2D metallic arrays with disc-in-hole binary nanostructures via a newly developed nanosphere lithography

2D metallic arrays with binary nanostructures derived from a nanosphere lithography (NSL) method have been rarely reported. Here, we demonstrate a novel NSL strategy to fabricate highly ordered 2D gold arrays with disc-in-hole binary (DIHB) nanostructures in large scale by employing a sacrificing layer combined with a three-step lift-off process. The structural parameters of the resultant DIHB arrays, such as periodicity, hole diameter, disc diameter and thicknesses can be facilely controlled by tuning the nanospheres size, etching condition, deposition angle and duration, respectively. Due to the intimate interactions between two subcomponents, the DIHB arrays exhibit both an extraordinary high surface-enhanced Raman scattering enhancement factor up to 5 × 108 and a low sheet resistance down to 1.7 Ω/sq. Moreover, the DIHB array can also be used as a metal catalyzed chemical etching catalytic pattern to create vertically-aligned Si nano-tube arrays for anti-reflectance application. This strategy provides a universal route for synthesizing other diverse binary nanostructures with controlled morphology, and thus expands the applications of the NSL to prepare ordered nanostructures with multi-function.

Complex nano-patterning of structural, optical, electrical and electron emission properties of amorphous silicon thin films by scanning probe

Abstract Preparation of nanoscale templates represents an important step for synthesis and assembly of diverse nanostructures and nanoscale devices. We show that complex nano-structural templates in a thin (40 nm) layer of hydrogenated amorphous silicon (a‐Si:H) can be prepared by using locally applied electric field in an atomic force microscope (AFM). Depth of the resulting structures (1–40 nm) can be controlled by the process parameters (magnitude of electric field, exposure time, or nano-sweeping of the tip). We demonstrate that complex patterns can be scribed into the a‐Si:H layer in that way. The prepared patterns exhibit different structural, optical, electrical, and electron emission properties, compared to the surroundings as detected by Raman micro-spectroscopy, scanning electron microscopy (SEM), and conductive AFM. The silicon thin films with locally modified properties can be useful in themselves or can serve as templates for further nanoscale growth or assembly.

Diverse Supramolecular Nanofiber Networks Assembled by Functional Low-Complexity Domains.

Self-assembling supramolecular nanofibers, common in the natural world, are of fundamental interest and technical importance to both nanotechnology and materials science. Despite important advances, synthetic nanofibers still lack the structural and functional diversity of biological molecules, and the controlled assembly of one type of molecule into a variety of fibrous structures with wide-ranging functional attributes remains challenging. Here, we harness the low-complexity (LC) sequence domain of fused in sarcoma (FUS) protein, an essential cellular nuclear protein with slow kinetics of amyloid fiber assembly, to construct random copolymer-like, multiblock, and self-sorted supramolecular fibrous networks with distinct structural features and fluorescent functionalities. We demonstrate the utilities of these networks in the templated, spatially controlled assembly of ligand-decorated gold nanoparticles, quantum dots, nanorods, DNA origami, and hybrid structures. Owing to the distinguishable nanoarchitectures of these nanofibers, this assembly is structure-dependent. By coupling a modular genetic strategy with kinetically controlled complex supramolecular self-assembly, we demonstrate that a single type of protein molecule can be used to engineer diverse one-dimensional supramolecular nanostructures with distinct functionalities.

NiCo2 S4 Materials for Supercapacitor Applications.

Cobalt-nickel sulfide (NiCo2 S4 ) shows extensive potential for innovative photoelectronic and energetic materials owing to distinctive physical and chemical properties. In this review, representative strategies for the fabrication and application of NiCo2 S4 and composite nanostructures are outlined for supercapacitors, with the aim of promoting the development of NiCo2 S4 and their composites in the supercapacitor field through an analysis and comparison of diverse nanostructures. A brief introduction into the structures, properties, and morphologies are presented. Further prospects and promising developments of the materials in the supercapacitor field are also proposed.

H‐bonding Assisted Self‐Assembled One‐Dimensional Nanotubes of Redox Active Triphenylamine‐Benzothiadiazole Derivative

AbstractControl over the one‐dimensional (1D) nanotubular structures significant in organic electronics. Although, p‐ and n‐type derivatives have shown diverse nanostructures, however very few ambipolar derivatives reported until now because of constrained structural properties. By considering this issue, three triphenylamine‐benzothiadiazole based ambipolar derivatives (TBE, TBAc and TBAm) synthesized and TBAm forms 1D nanotubes exclusively. DFT and spectroelectrochemical studies displayed the formation of stable cation and anion radicals of TBAm under controlled potential of 1.30 V. UV‐vis, emission (steady‐state and TCSPC) and microscopic analyses revealed TBAm exists as J‐aggregates and further leads to nanotubes by utilizing directional amide H‐bonding, together with π‐π stacking and van der Waals interactions. Consequently, these properties aid to design novel materials, which pave the way towards efficient organic field effect transistors.

Ionic Complexes of Metal Oxide Clusters for Versatile Self-Assemblies

The combination of rational design of building components and suitable utilization of driving force affords spontaneous molecular assemblies with well-defined nanostructure and morphology over multiple length scales. The serious challenges in constructing assemblies with structural advantages for the realization of functions programmed into the building components usually lie ahead since the process that occurs does not always follow the expected roadmap in the absence of external intervention. Thus, prefabricated intermediates that help in governing the target self-assemblies are developed into a type of unique building blocks. Metal oxide cluster polyanions are considered as a type of molecular nanoclusters with size scale and structural morphology similar to those of many known inorganic particles and clusters but possess distinctive characteristics. Following the understanding of these clusters in self-assembly and the rationalization of their most efficient design strategy and approach, the obtained fundamental principles can also be applied in common nanoparticle- and cluster-based systems. On the other hand, the deliberate synergy offered by organic countercations that support the self-assembly of these clusters greatly expands the opportunity for the functionalization of complex building units via control of multiple interactions. The ionic combination of the inorganic clusters with hydrophilicity and the cationic organic component with hydrophobicity leads to discrete properties of the complexes. Significantly, the core-shell structure with rigid-flexible features and amphiphilicity will pave the way for hierarchical self-assemblies of the obtained complexes, while the intrinsic characteristics of the metal oxide clusters can be modulated through external physicochemical stimuli. Within this context, over the past decade we have extensively explored the ionic combination of inorganic polyanionic clusters with cationic organic amphiphiles and devoted our efforts to establishing the general rules and structure-property relationships of the formed complexes for constructing self-assemblies at the interface, in solution, and in solid matrixes. Specific interest has been focused on the functional synergy deriving from the incompatible components in highly organized self-assemblies. In this Account, we describe the recent progress on the ionic complexation of polyoxometalate clusters with cationic amphiphiles and the construction of diverse self-assembled nanostructures. First, the fundamental structural characteristics and molecular geometries of the prepared complexes are analyzed. The construction principle and diversity of the self-assembly based on the complexes and the smart stimuli response are then discussed, subject to the adjustment of various non-covalent interactions occurring in the assemblies. Subsequently, we enumerate the functional applications of the ionic complexes assembling into organic, inorganic, and even biological matrixes. The inspiration from the construction of ionic complexation and self-assembly in this Account provides vivid profiles for the design of hybrid materials involving nanoclusters and/or nanoparticles with rich potentials in addition to polyoxometalate chemistry.

Controllable Self-Assembly of Amphiphilic Zwitterionic PBI Towards Tunable Surface Wettability of the Nanostructures.

Amphiphilic molecules have received wide attention as they possess both hydrophobic and hydrophilic properties, and can form diverse nanostructures in selective solvents. Herein, we report an asymmetric amphiphilic zwitterionic perylene bisimide (AZP) with an octyl chain and a zwitterionic group on the opposite imide positions of perylene tetracarboxylic dianhydride. The controllable nanostructures of AZP with tunable hydrophilic/hydrophobic surface have been investigated through solvent-dependent amphiphilic self-assembly as confirmed by SEM, TEM, and contact angle measurements. The planar perylene core of AZP contributes to strong π-π stacking, while the amphiphilic balance of asymmetric AZP adjusts the self-assembly property. Additionally, due to intermolecular π-π stacking and solvent-solute interactions, AZP could self-assemble into hydrophilic microtubes in a polar solvent (acetone) and hydrophobic nanofibers in an apolar solvent (hexane). This facile method provides a new pathway for controlling the surface properties based on an asymmetric amphiphilic zwitterionic perylene bisimide.