Self-assembled Hierarchical Nanostructures Research Articles

Nanorods Assembled Hierarchical Bi2S3 for Highly Sensitive Detection of Trace NO2 at Room Temperature

The bismuth sulfide nanostructure has become a promising gas sensing material thanks to its exceptional intrinsic properties. However, pristine Bi2S3 as a room-temperature sensing material cannot achieve the highly sensitive detection of ppb-level NO2 gas. Herein, 1D nanorods with self-assembled hierarchical Bi2S3 nanostructures were obtained via a simple hydrothermal process. The as-prepared hierarchical Bi2S3 nanostructures exhibited outstanding NO2 sensing behaviors, such as a high response value (Rg/Ra = 5.8) and a short response/recovery time (τ90 = 28/116 s) upon exposure to 1 ppm NO2. The limit of detection of hierarchical Bi2S3 was down to 50 ppb. Meanwhile, the sensor exhibited excellent selectivity and humidity tolerance. The improved NO2 sensing properties were associated with the self-assembled hierarchical nanostructures, which provided a rich sensing active surface and accelerated the diffusion and adsorption/desorption processes between NO2 molecules and Bi2S3 materials. Additionally, the sensing response of hierarchical Bi2S3 nanostructures is much higher at 100% N2 atmosphere, which is different from the chemisorption oxygen model.

Large-Scale Assembly of Peptide-Based Hierarchical Nanostructures and Their Antiferroelectric Properties.

An effective strategy is developed to create peptide-based hierarchical nanostructures through the meniscus-driven self-assembly in a large area and fabricate antiferroelectric devices based on these nanostructures for the first time. The diphenylalanine hierarchical nanostructures (FF-HNs) are self-assembled by vertically pulling a substrate from a diphenylalanine (FF) solution dissolved in a miscible solvent under precisely controlled conditions. Owing to the unique structural properties of FF nanostructures, including high crystallinity and α-helix structures, FF-HNs possess a net electrical dipole moment, which can be switched in an external electric field. The mass production of antiferroelectric devices based on FF-HNs can be successfully achieved by means of this biomimetic assembly technique. The devices show an evident antiferroelectric to ferroelectric transition under dark conditions, while the ferroelectricity is found to be tunable by light. Notably, it is discovered that the modulation of antiferroelectric behaviors of FF-HNs under glutaraldehyde exposure is due to the FF molecules that are transformed into cyclophenylalanine by glutaraldehyde. This work provides a stepping stone toward the mass production of self-assembled hierarchical nanostructures based on biomolecules as well as the mass fabrication of electronic devices based on biomolecular nanostructures for practical applications.

Hierarchical cage-frame type nanostructure of CeO2 for bio sensing applications: from glucose to protein detection

Self-assembled hierarchical nanostructures are slowly superseding their conventional counterparts for use in biosensors. These morphologies show high surface area with tunable porosity and packing density. Modulating the interfacial interactions and subsequent particle assembly occurring at the water-and-oil interface in inverse miniemulsions, are amongst the best strategies to stabilize various type of hollow nanostructures. The paper presents a successful protocol to obtain CeO2 hollow structures based biosensors that are useful for glucose to protein sensing. The fabricated glucose sensor is able to deliver high sensitivity (0.495 μA cm−2 nM−1), low detection limit (6.46 nM) and wide linear range (0 nM to 600 nM). CeO2 based bioelectrode can also be considered as a suitable candidate for protein sensors. It can detect protein concentrations varying from 0 to 30 µM, which is similar or higher than most reports in the literature. The limit of detection (LOD) for protein was ∼0.04 µM. Therefore, the hollow CeO2 electrodes, with excellent reproducibility, stability and repeatability, open a new area of application for cage-frame type particles.

Fragmented lignin-assisted synthesis of a hierarchical ZnO nanostructure for ammonia gas sensing.

In the present study, we demonstrated the use of fragmented lignin in the synthesis of a hierarchical-type structure of ZnO nanorods. Lignin was isolated from bagasse by the microwave assisted method and its fragmentation was achieved in alkaline conditions along with hydrogen peroxide. Lignin and fragmented lignin were purified by crystallisation followed by column chromatography and characterized by UV-visible spectroscopy, Frontier infra-red spectroscopy (FTIR), 1H-NMR and high resolution mass spectroscopy (HRMS). Fragmented lignin was utilized as a template for the synthesis of ZnO nanorods, which were characterized by powder XRD, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and UV-DRS for the determination of crystal structure, particle morphology and band gap. XRD of the ZnO samples revealed a hexagonal wurtzite structure. The morphology of ZnO without fragmented lignin showed agglomerated nanoparticles and with fragmented lignin, a self-assembled hierarchical nanostructure due to nanorods of 30 nm diameter and 200–500 nm length was observed. The fragmented lignin showed a pronounced effect on the particle size and morphology of ZnO nanoparticles. We measured the response of the hierarchical ZnO nanostructure (50 ppm) for sensing NH3 in terms of change in voltage across known resistance. We observed the response and recovery upon introduction of the analyte ammonia gas at 175 °C.

Understanding the Apparent Non-Reliability in the Sensing Characteristics of MnO2 Self-Assembled Hierarchical Nanostructure

In this paper, the self-assembled hierarchical nanostructure of MnO2, consisting of 3-D nanoflowers and 1-D nanorods, was synthesized by employing a hydrothermal technique. The gas sensing property of the same was investigated and the apparent anomaly concerning the n-type material characteristics and p-type sensing behavior was explained using the underlying mechanistic framework. The morphological (field emission scanning electron microscopy, transmission electron microscopy), structural (X-ray diffraction), and surface compositional (X-ray photoelectron spectroscopy) characterizations were carried out in detail, to establish the formation of $\delta$ -MnO2 (nanosheets having thicknesses ~ 5–18 nm) and $\alpha$ -MnO2 (nanorods having diameters ~ 20–24 nm) in the synthesized hierarchical nanostructure. The self-assembled MnO2 nanostructure offered pulse-like gas sensing performance with very fast response time and recovery time at room temperature. A possible sensing mechanism has also been furnished considering the effect of Mn interstitials (Mn ${_{i}}$ ) reduction from Mn4+/Mn3+ states to Mn3+/Mn2+ states (in the presence of methanol), to explain the apparent anomaly in the sensing characteristics.

Hierarchical three-dimensional manganese doped cobalt phosphide nanowire decorated nanosheet cluster arrays for high-performance electrochemical pseudocapacitor electrodes.

Ternary metal phosphides with a self-assembled hierarchical nanostructure are promising electrode materials for energy storage and conversion, due to the unique architecture and synergistic effects in bimetallic nanostructures. In this communication, we demonstrate hierarchical Mn-doped cobalt phosphide nanowire decorated nanosheet cluster arrays with robust adhesion on Ni foam (Mn-CoP/NF) as a binder-free electrode for supercapacitors. Such a 3D electrode exhibits boosted areal specific capacitance over that for a single metal counterpart, with the accomplishment of 8.66 F cm-2 capacitance at 1 mA cm-2. Utilizing the Mn-CoP/NF electrode as an anode and an activated carbon (AC) electrode as a cathode, an asymmetric supercapacitor (ASC) of Mn-CoP//AC attains a high area capacitance of 2.05 F cm-2 at 5 mA cm-2 and a high capacitance retention of 88.9% after 4000 cycles. In addition, the assembled ASC shows superior electrochemical performances with a high energy density of 35.21 W h kg-1 at a power density of 193 W kg-1 and of 30.87 W h kg-1 even at 1939 W kg-1.

Self-Assembled Hierarchical Formation of Conjugated 3D Cobalt Oxide Nanobead-CNT-Graphene Nanostructure Using Microwaves for High-Performance Supercapacitor Electrode.

Here we report the electrochemical performance of a interesting three-dimensional (3D) structures comprised of zero-dimensional (0D) cobalt oxide nanobeads, one-dimensional (1D) carbon nanotubes and two-dimensional (2D) graphene, stacked hierarchically. We have synthesized 3D self-assembled hierarchical nanostructure comprised of cobalt oxide nanobeads (Co-nb), carbon nanotubes (CNTs), and graphene nanosheets (GNSs) for high-performance supercapacitor electrode application. This 3D self-assembled hierarchical nanostructure Co3O4 nanobeads-CNTs-GNSs (3D:Co-nb@CG) is grown at a large scale (gram) through simple, facile, and ultrafast microwave irradiation (MWI). In 3D:Co-nb@CG nanostructure, Co3O4 nanobeads are attached to the CNT surfaces grown on GNSs. Our ultrafast, one-step approach not only renders simultaneous growth of cobalt oxide and CNTs on graphene nanosheets but also institutes the intrinsic dispersion of carbon nanotubes and cobalt oxide within a highly conductive scaffold. The 3D:Co-nb@CG electrode shows better electrochemical performance with a maximum specific capacitance of 600 F/g at the charge/discharge current density of 0.7A/g in KOH electrolyte, which is 1.56 times higher than that of Co3O4-decorated graphene (Co-np@G) nanostructure. This electrode also shows a long cyclic life, excellent rate capability, and high specific capacitance. It also shows high stability after few cycles (550 cycles) and exhibits high capacitance retention behavior. It was observed that the supercapacitor retained 94.5% of its initial capacitance even after 5000 cycles, indicating its excellent cyclic stability. The synergistic effect of the 3D:Co-nb@CG appears to contribute to the enhanced electrochemical performances.

Self-assembled hierarchical nanostructures of Bi2WO6 for hydrogen production and dye degradation under solar light

Photocatalytic dye degradation and H2 generation are demonstrated using 3D hierarchical nanostructures of orthorhombic Bi2WO6 synthesized by a solvothermal method.

Microwave-assisted synthesis of self-assembled BiO1.84H0.08 hierarchical nanostructures as a new photocatalyst

Self-assembled hierarchical nanostructures of BiO1.84H0.08 spheres have been successfully synthesized by a rapid, one-pot, low-temperature hydrothermal route under microwave irradiation. The as-prepared hierarchically nanostructured BiO1.84H0.08 possesses a high surface area of 113m2g−1. By adjusting the reaction temperature and reactant concentration, the morphology of the as-formed BiO1.84H0.08 nanostructures can be tailored. As a new photocatalyst, the flower-like spherical BiO1.84H0.08 exhibits enhanced photocatalytic activity for degradation of Rhodamine B (RhB) under UV–visible light. The synthetic procedure is simple, efficient, and scalable for mass production. Therefore, the as-formed BiO1.84H0.08 hierarchical nanostructures may offer great potential applications for decomposition of organic contaminants.

Self-Assembled Hierarchical Nanostructures Composed of Novel Chalcopyrite Nanosheets for Photovoltaic Properties

Self-assembled nanostructures of CulnGaSe2 (CIGS) comprising of nanosheets with sheet thickness of 20 nm have been developed via one-step electrochemically alloying technique. These self-assembled nanoplates exhibit highly intersecting behavior and transform from CuSe to CIGS as the reduction potential was varied. The morphological analysis indicated that the process resulted in a progression of crystallites to a series of heavy dense intersecting nanoplates. Further analyses revealed that the nanostructures keep their integrity on heat treatment. The structure confirms the inclusion of Indium and Gallium at higher reduction potentials and its transition from pseudoamorphous to polycrystalline structure. A strong correlation between reduction potential, and the composition was established. The spectroscopic and optical spectra clearly prove that the direct band gap for the as-grown and annealed thin films, and appropriate for solar cell applications. These self-assembled dense interweaved nanoplates structure have not been observed previously in CIGS semiconductor system and have potential implications forenergy applications.

Multiscale Modeling of Elasticity and Fracture in Organic Nanotubes

AbstractCyclic peptide nanotubes (CPNs) have unique chemical and mechanical features that squarely position them to tackle persistent challenges in sensor technologies, tissue scaffolds, templates for organic and hybrid electronics, and ultrasmall electromechanical systems. These self-assembled hierarchical nanostructures are highly organized at the nanoscale and feature exceptional thermodynamical stability arising from the collective action of secondary interactions, in particular intersubunit hydrogen-bond networks. Understanding the elasticity and fracture behavior of CPNs through a multiscale analysis is crucially important for developing science-based approaches for designing the molecular subunits and hierarchical assemblies of these materials. In pursuit of addressing this need, a methodology is proposed for linking atomistic simulation results into coarser descriptions of these self-assembling soft nanostructures. This approach involves estimation of the free-energy landscape of the system along ...

Rational growth of ternary Zn2GeO4 nanorods and self-assembled hierarchical nanostructures

Hierarchical self-assembled 3-D ternary Zn2GeO4 nanorods have been successfully synthesized using a simple hydrothermal method. They are formed by two basic parts: a 3-D crystal base and 1-D nanorods nucleated from this base. Mechanisms of this micro/nanostructure growth are suggested to be governed by the change of concentration of ammonia and the reaction time during the self-assembly process. Good crystal lattice quality and morphology were demonstrated by XRD, SEM and TEM analyses. The micro/nanostructures are expected to be promoted in construction of micro/nano-optoelectronic devices.

Self-Assembled Hierarchical Structure of Fullerene Building Blocks; Single-Walled Carbon Nanotubes and C60

We report a self-assembled hierarchical nanostructure produced by mixing two carbon nanobuilding blocks—fullerene nanospheres (C60) and (10,10) armchair single-walled carbon nanotubes— at ambient temperature and pressure. It was found that upon mixing the fullerene building blocks, they self-assemble into films with smectic liquid crystal-like periodicity. The films wrap around to form nanospheres (50 to 150 nm in diameter) with central cavities resembling pitted nanofruits that are connected by a network of stems. Raman spectroscopy showed 10 cm–1 softening in the frequency of the G+ mode of the assembled nanotubes indicating significant alteration in the assembly’s electronic structure. The current findings point out a new rich subject to explore which could promote engineered nanostructured assemblies leading to many advances in materials science and biological and environmental fields.

A self-assembled hierarchical nanostructure comprising carbon spheres and graphene nanosheets for enhanced supercapacitor performance

A self-assembly approach is used to fabricate a hierarchical nanostructure using functionalized carbon spheres as nano-spacers to separate graphene nanosheets. The nanostructure significantly enhances capacitance of a graphene supercapacitor by more than 70%, while providing a universal method to self-assembling various carbons into hierarchical structures for energy conversion/storage systems.

ZnO Nanotube Arrays and Nanotube-Based Paint-Brush Structures: A Simple Methodology of Fabricating Hierarchical Nanostructures with Self-Assembled Junctions and Branches

ZnO nanotube arrays and self-assembled hierarchical nanostructures are reported here. The ZnO nanostructures were synthesized on Zn foils by a simple solvothermal approach. The hierarchical nanostructures resemble the paint-brush morphology, which consisted of a bunch of self-assembled thin nanowires on a comparatively thick ZnO nanotube wall. Successful creation of surface roughness through controlled etching of the ZnO nanotube walls provided the secondary nucleation centers for the nanowires.