Formation Of Hierarchical Nanostructures Research Articles

Formation of hierarchical TiO2 nanoporous structure from free-standing TiO2 nanotubes layers

Hierarchical TiO2 nanoporous structures with tailored porosity have been fabricated by simply annealing of free-standing TiO2 nanotubes (TNTs) layers in the presence of in situ trapped F-species. The hierarchical nanostructures consist of concatenated anatase TiO2 nanoparticles (NPs). TiO2 with different hierarchical nanostructure are obtained by changing the annealing rate of the free-standing TNTs layers. The hierarchical structure with nanopores formation in the walls of TNTs is achieved when the annealing rate is 3 °C/min. Increase in the annealing rate of the free-standing TNTs layers leads to the formation of hierarchical nanostructure of anatase TiO2 NPs morphologically resembling beads threaded into linear strings. The TiO2 hierarchical nanostructure undergoes two evolution steps, which include formation of nanopores in the walls of nanotubes and finally to concatenated anatase TiO2 NPs when the annealing rate is increased. Results show that hierarchical nanoporous structure of anatase TiO2 consist of nanopores whose diameter varies from 20 to 100 nm. EDX analysis confirms the presence of C and F-species in the as-prepared free-standing TNTs layer in significant amount. It is found that the hierarchical TiO2 nanostructure formation mainly depends upon the annealing rate and presence of F-species. GAXRD, Raman analysis and SAED pattern exhibits enhancement in the crystallinity of the hierarchically TiO2 nanostructure. This study provides an easy method for the synthesis of the hierarchical anatase TiO2 nanostructure on a large scale.

Self-Supporting Three-Dimensional ZnIn2S4/PVDF–Poly(MMA-co-MAA) Composite Mats with Hierarchical Nanostructures for High Photocatalytic Activity

This paper reports the fabrication of self-supporting three-dimensional ZnIn2S4/PVDF–poly(MMA-co-MAA) (ZIS/Polymer) composite mats with hierarchical nanostructures by a simple combination of an electrospinning technique and a hydrothermal process and their high photocatalytic activity. The characterization results show that ZnIn2S4 (ZIS) nanosheets with a thickness of about 20 nm distribute uniformly on the surface of the nanofiber polymers to form mats. The coverage density of the ZIS nanosheet coating on the surface of the polymer mats could be controlled by simply adjusting the amount ratios of feeding reactants to polymers. Furthermore, the growth process of ZIS coating is investigated based on time-dependent experiments. The obtained ZIS/Polymer heteroarchitectures show high photocatalytic property and stability to degrade methyl orange (MO) because of the formation of hierarchical nanostructures, which might improve the adsorption and catalysis of the dyes. Due to the self-supporting property of the mats, the ZIS/Polymer mats could be laid or hung conveniently anywhere under solar irradiation and recycled easily, which provides a solution to the separation problem for conventional catalysts that are small in size. The study may open a new way to build hierarchical device fabrics with optical and catalytic properties.

Template-free solvothermal synthesis of 3D hierarchical nanostructured boehmite assembled by nanosheets

In the absence of template and surfactant, hierarchical nanostructured boehmite was synthesized via a simple solvothermal route using aluminum nitrate as aluminum source and isopropanol–toluene mixture as solvent. The crystal structures, morphologies and textural properties of products were characterized by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and N2 adsorption–desorption technique. The as-obtained hierarchical nanostructures consist of nanosheets keeping Brunauer–Emmett–Teller (BET) specific surface area and pore volume of ca. 264.7m2/g and 1.2cm3/g, respectively. The experimental results show that the longer reaction time and the lower reaction temperature are unfavorable to the formation of hierarchical nanostructures. Moreover, the properties of solvent have important influence on the morphology of product. The possible formation mechanism of boehmite hierarchical nanostructures was proposed and discussed.

Hierarchical Metallic and Ceramic Nanostructures Produced via a Hybrid Approach Combining Laser Interference Ablation and Block Co-Polymer Phase Separation

ABSTRACTWe report on the formation of hierarchical nanostructures of Au, Pt, Fe2O3 and PdO2 using a hybrid technique combining laser interference patterning (LIP) and block copolymer phase separation (BCPS). By varying the loading time of the block copolymer with metallic salts and the laser interference technique, different types of hierarchical square, triangular, linear and circular arrays can be formed. Such a robust method can be applied to other metallic and ceramic materials and has potential for use in the large-scale production of nano-catalysts, photonics, optoelectronics, MEMS devices and bio-sensors.

Studies of Thermal Stability of Multivalent DNA Hybridization in a Nanostructured System

A fundamental understanding of molecular self-assembly processes is important for improving the design and construction of higher-order supramolecular structures. DNA tile based self-assembly has recently been used to generate periodic and aperiodic nanostructures of different geometries, but there have been very few studies that focus on the thermodynamic properties of the inter-tile interactions. Here we demonstrate that fluorescently-labeled multihelical DNA tiles can be used as a model platform to systematically investigate multivalent DNA hybridization. Real-time monitoring of DNA tile assembly using fluorescence resonance energy transfer revealed that both the number and the relative position of DNA sticky-ends play a significant role in the stability of the final assembly. As multivalent interactions are important factors in nature's delicate macromolecular systems, our quantitative analysis of the stability and cooperativity of a network of DNA sticky-end associations could lead to greater control over hierarchical nanostructure formation and algorithmic self-assembly.

Kinetics of formation of hierarchical nanostructures in polystyrene films containing fullerene

Kinetics of formation of hierarchical nanostructures in polystyrene films containing fullerene

Hierarchical Nanostructures of Bent-Core Molecules Blended with Poly(styrene-b-4-vinylpyridine) Block Copolymer

We report the phase structures observed in blends of poly(styrene-b-4-vinylpyridine) (PS-b-P4VP) block copolymer (BCP) and a bent-core molecule 1-[4‘-(3‘ ‘,4‘ ‘,5‘ ‘-tridecyloxybenzoyloxy)phenyleneoxycarbonyl]-3-[(4‘-hydroxyphenyl)oxycarbonyl]benzene (BP). Hydrogen bonding between the terminal −OH group of BP and pyridine of P4VP led to the formation of P4VP(BP)n complex, which exhibited liquid crystalline (LC) order. This LC ordering, combined with microphase separation of the BCP, led to the formation of hierarchical nanostructures. The phase structures of the blend samples were investigated as a function of the concentration of BP using small-angle and wide-angle X-ray scattering and transmission electron microscopy techniques. By increasing the BP content, BCP phase morphology transformed from lamellae to cylinders. In the two cases investigated, the P4VP/BP complex formed a bilayer smectic A LC structure within the BCP domains, and these layered structures were oriented perpendicular to the BCP inter...