Hierarchical Flower-like Nanostructures Research Articles

On-Electrode Synthesis of Shape-Controlled Hierarchical Flower-Like Gold Nanostructures for Efficient Interfacial DNA Assembly and Sensitive Electrochemical Sensing of MicroRNA.

The performance for biomolecular detection is closely associated with the interfacial structure of a biosensor, which profoundly affects both thermodynamics and kinetics of the assembly, binding and signal transduction of biomolecules. Herein, it is reported on a one-step and template-free on-electrode synthesis method for making shape-controlled gold nanostructures on indium tin oxide substrates, which provide an electrochemical sensing platform for ultrasensitive detection of nucleic acids. Thus-prepared hierarchical flower-like gold nanostructures (HFGNs) possess large surface area that can readily accommodate the assembly of DNA probes for subsequent hybridization detection. It is found that the sensitivity for electrochemical DNA sensing is critically dependent on the morphology of HFGNs. By using this new strategy, a highly sensitive electrochemical biosensor is developed for label-free detection of microRNA-21 (miRNA-21), a biomarker for lung cancers. Importantly, it is demonstrated that this biosensor can be employed to measure the miRNA-21 expression level from human lung cancer cell (A549) lysates and worked well in 100% serum, suggesting its potential for applications in clinical diagnosis and a wide range of bioanalysis.

Design and construction of three-dimensional flower-like CuO hierarchical nanostructures on copper foam for high performance supercapacitor

We have developed a simple and cost-effective one-step surface oxidation method to synthesize three-dimensional (3D) flower-like, similar to that of a blooming chrysanthemum, CuO hierarchical nanostructures directly on a copper foam, which is acting as the Cu source and the current collector. The as-prepared sample can be directly used as a binder-free electrode for supercapacitors. Benefiting from the novel synthesis strategy and the 3D connect/quasi-connect structures, the as-prepared CuO/copper foam electrode can provide massive active sites for redox reactions, high electronic conductivity, short diffusion pathway for ions and effectively electrolyte penetrating. These characteristics together with the synergy effect between CuO and copper foam substrate lead to a high capacitance of 1641.4mFcm−2, good rate capability (77.2% retention upon increasing the current density by 10 times) and good cyclability (79% retention after 10000 cycles). These results suggest that the CuO electrode demonstrates a good potential for high performance energy storage devices.

Enhanced selective acetone sensing characteristics based on Co-doped WO3 hierarchical flower-like nanostructures assembled with nanoplates

Co-doped WO3 hierarchical flower-like nanostructures assembled with nanoplates (FNPs) were synthesized by a one-step hydrothermal route. The as-synthesized FNPs were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS). The gas sensing properties of the pure and Co-doped WO3 FNPs were tested to various volatile organic compounds (VOCs). Among pure and Co-doped WO3 FNPs, 0.6at% Co-doped WO3 presented the best properties. It was found that 0.6at% Co-doped WO3 FNPs exhibited quite short response and recover time of about 2s and 10s in response to 100ppm acetone gas. And the response of 0.6at% Co-doped WO3 FNPs to 100ppm acetone gas was 103, which was about 5 times higher than pure WO3. The improvement of gas sensing properties could be attributed to the morphology changes of Co-doped WO3 FNPs as well as the defect of WO3 lattice and Co catalysis effect to promote gas adsorption.

SDS-assisted hydrothermal synthesis of NiO flake-flower architectures with enhanced gas-sensing properties

A facile hydrothermal route was developed for the preparation of well-aligned hierarchical flower-like NiO nanostructure with the assistance of SDS that served as a structure-directing agent as well as a capping agent in the process of aggregation and assembly. Notably, the NiO sensors exhibit enhanced gas-sensing performance towards ethanol, which could be explained in association with the ultrathin nanosheets that are close to Debye length (LD) scale and thus get the majority carriers fully depleted due to the ionization of adsorbed oxygen, abundant effective gas diffusion paths as well as high surface-to-volume ratio to promote sufficient contact and reaction between the NiO sample and ethanol molecules, and numerous miniature reaction rooms assembled with nanosheets to make the test gas molecules stay long enough for completed gas-sensing reactions. Besides, a novel growth mechanism with the passage of reaction time was also proposed in detail.

A high sensitive and low detection limit of formaldehyde gas sensor based on hierarchical flower-like CuO nanostructure fabricated by sol–gel method

The hierarchical flower-like CuO nanostructure was synthesized by a facile sol–gel method without template. Indirectly-heated sensors are fabricated by coating the sol–gel on ceramic tubes with signal electrodes and subsequent annealing. The obtained nanostructures are analyzed by X-ray diffraction and scanning electron microscopy. Their gas sensing performances were investigated. The results indicated that the sensor based on hierarchical flower-like CuO exhibited excellent sensing properties towards ethanol, formaldehyde, acetone and dimethylbenzene. The sensor based on the CuO exhibited the optimal gas sensing performance, giving a ppb-level detection limit and a high response (Rg/Ra) of 1.378 to 50 ppb formaldehyde at 250 °C. The response and recovery time of the flower-like CuO nanostructure sensor are 11.9 and 8.4 s, respectively. The significantly enhanced sensing properties to formaldehyde could be attributed to the changes in crystallite size and specific surface area. The results indicate that the hierarchical flower-like CuO nanostructure gas sensor can be a simple and useful platform for formaldehyde and other volatile organic compounds sensing application.

One-step solution synthesis and formation mechanism of flower-like ZnO and its structural and optical characterization

The regular hierarchical flower-like ZnO nanostructures assembled by nanosheets were successfully synthesized by one-step solution route with citrate assistance at room temperature. It was demonstrated that the concentration of citrate and the molar ratio of Zn2+/OH− had strong effect on the formation of nanosheets and self-assembly flower-like nanostructures. A reasonable formation mechanism of the flower-like nanostructures was proposed. According to UV–vis spectrum, the flower-like ZnO nanostructures exhibited strong light absorption, and the value of band gap of the obtained ZnO was estimated to be 3.26eV. Moreover, the room-temperature photoluminescence (PL) spectrum of the sample presented only a near-band edge emission at 382nm.

Facile Preparation of Ag2ZnGeO4 Flower-like Hierarchical Nanostructure and Its Photocatalytic Activity

In this study, Ag2ZnGeO4 flower-like hierarchical nanostructure was prepared using a simple and mild method. The as-prepared samples were characterized with X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, UV–vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, and N2 adsorption and desorption isotherms. Meanwhile, the photocatalytic activity of the as-prepared samples was explored using Rhodamine B as a model pollutant. The results indicated that the Ag2ZnGeO4 hierarchical nanostructures obtained consisted of nanoplates and nanorods, and adopted spherical flower-like morphology. Moreover, the as-prepared Ag2ZnGeO4 hierarchical nanostructure was an efficient and stable visible-light photocatalyst for the degradation of organic dyes in water. After visible light irradiation for 105 min, the degradation of Rhodamine B was up to 92%. Moreover, the photocatalytic activity of Ag2ZnGeO4 remained unchanged after three successive cycles.

Synthesis of flower-like cuo hierarchical nanostructures as an electrochemical platform for glucose sensing

Flower-like CuO hierarchical nanostructures were synthesized on copper foil substrate through a simple wet chemical route in alkaline media at room temperature. SEM images collected at different reaction times revealed the transformation of initially formed Cu(OH)2 nanowires to flower-like CuO nanostructures. The hierarchical structure of the as-prepared CuO showed high electrocatalytic activity towards the oxidation of glucose making it a promising electrode material for the development of non-enzymatic glucose sensor. The amperometric sensor exhibited a wide linear response to glucose ranging from 4.5 × 10−5 to 1.3 × 10−3 mol L−1 (R2 = 0.99317) at fixed potential of 0.3 V. The detection limit was 6.9 × 10−6 mol L−1 (LOD = 3σ/s) with a sensitivity of 1.71 μA μmol−1 cm−2. Moreover, the developed sensor offers a fast amperometric response, good selectivity and stability.

Nanotechnology: a clean and sustainable technology for the degradation of pharmaceuticals present in water and wastewater.

Pharmaceuticals, newly recognized classes of environmental pollutants, are becoming increasingly problematic contaminants of either surface water or ground water around industrial and residential communities. Pharmaceuticals are constantly released into aquatic environments, mainly due to their widespread consumption and complicated removal in wastewater treatment plants. Heterogeneous photocatalysis appear to be one of the most destructive advanced oxidation processes (AOPs) for organic contaminants and are possible to obtain complete mineralization of organic pollutants into eco-friendly end products under visible and solar light irradiation. In this study, flower-like In2S3 hierarchical nanostructures were successfully prepared via a facile solution-phase route, using thioacetamide as both sulfur source and capping agent. X-ray diffractometry (XRD) of the flowers revealed that the cubic structure of In2S3; morphological studies examined by scanning electron microscopy (SEM) showed the synthesized In2S3 nanostructure was flower-like hierarchitecture assembled from nanoscale flakes. X-ray photoelectron spectroscopy (XPS) analysis confirmed the stoichiometry of In2S3 nanoflowers. Furthermore, the photocatalytic activity studies revealed that the prepared indium(III) sulfide(In2S3) nanoflowers exhibit an excellent photocatalytic performance, degrading rapidly the aqueous pharmaceutical solution of Lisinopril under visible light irradiation. These results suggest that In2S3 nanoflowers will be a promising candidate of photocatalyst working in thevisible light range.

Facile template-free fabrication of novel flower-like γ-Al2O3nanostructures and their enhanced Pb(ii) removal application in water

Novel hierarchical flower-like γ-Al2O3 nanostructures were successfully fabricated via a facile template-free and cost-efficient process, in which the presence of urea had a crucial influence on their morphology control. Upon the addition of urea, the morphology gradually evolved from nanoparticles to flake-like nanopetals which finally self-assembled to flower-like architectures, and increasing the concentration of urea could increase the density of nanoparticles composed of flake-like nanopetals. Further application in water showed excellent adsorption performance for lead (Pb(II)) removal.

Synthesis of hierarchical flower-like SnO2 nanostructures and their photocatalytic properties

SnO2 nanostructures were prepared successfully through a template-free and surfactant-free hydrothermal method. The prepared SnO2 nanostructures were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Raman spectra and UV–vis absorption spectra. Photocatalytic activity was evaluated using the degradation of organic dye methyl orange. Furthermore, the possible growth and photodegradation mechanism of the as-prepared sample were also briefly discussed.

Growth characteristics and influencing factors of 3D hierarchical flower-like SnS2 nanostructures and their superior lithium-ion intercalation performance

3D hierarchical SnS2 nanoflowers are prepared by a template-free, inexpensive and controllable approach for their application to Li-ion batteries. They are composed of intertwining twisted nanosheets as the building unit. Their formation mechanism is explored through a group of time-dependent experiments. It is for the first time found that the morphological evolution, phase transition and composition changes occur simultaneously during their growth process. Three influencing factors, namely precursor concentration, reaction temperature and time, are examined by the observation of SnS2 nanostructures, to achieve the controlled synthesis of high-quality 3D SnS2 hierarchitectures. Irregular SnS2 nanoparticles are produced for a comparison with the SnS2 nanoflowers in terms of Li-ion insertion properties. The former shows smaller capacities and poorer rate capability than the latter. In tests the former exhibits capacities of 249.5–404.5 mA h g−1 at 100 mA g−1 over 50 battery cycles, while the latter could deliver capacities of 432–519 mA h g−1. In addition, the former displays capacities of 372 to 105 mA h g−1 while the latter shows capacities of 498 to 297 mA h g−1 as the current arises from 100 to 800 mA g−1. Redox reaction characteristics and Li-ion transfer kinetics at the two SnS2 anodes are studied with differential capacity curves and electrochemical impedance spectroscopy. It is concluded that the excellent electrochemical behaviors of SnS2 nanoflowers derive from their structural merits such as large surface area, hierarchical porous structure and sheet-like building units that endow them with improved electrode reactions and charge transfer kinetics.

Synthesis of Mg-doped hierarchical ZnO nanostructures via hydrothermal method and their optical properties

Hierarchical flower-like ZnO nanostructures and Mg-doped ZnO flower-like hierarchical nanostructures composed of porous nanosheets were synthesized via a one-step hydrothermal method. In this method, Zn(NO3)2·6H2O was used as a precursor and Mg(NO3)2·6H2O was the dopant. FESEM, EDS, XRD, UV–vis absorption spectra and PL spectra were used to characterize the samples. It demonstrates that small portions of Mg are successfully incorporated into the lattice of the ZnO nanostructures. The incorporation of Mg into ZnO is supported by broadening and higher Bragg angle shift in XRD pattern and EDS analysis. Cell Parameters of hierarchical flower-like Mg-doped ZnO nanostructures are obtained from Rietveld analysis. The decrease of c-axis indicates that substitution by Mg2+ is the dominant doping form in the hierarchical ZnO nanostructures. PL spectra show that the effective Mg doping suppresses the near band gap emission and the green emission. The band edge emission shifts to the blue with increasing amount of Mg doping, reflecting the change in the excitons energy seen in the absorption spectra. The defect band is believed to be due to deep traps and becomes dominant at high levels of doping. All the results show that the molar ratio of Mg and Zn determines the structure, surface morphology and optical properties of the samples significantly.

Hierarchical flower-like nanostructures of anatase TiO2 nanosheets dominated by {001} facets

Hierarchical nanostructures of anatase TiO2 with high specific surface area are specially significant in various applications. In this work, we using a one-pot, template-free method that employed ethanol as mild solvent and obtained hierarchical flower-like TiO2 nanostructures. Interestingly, the hierarchical structures are assembled by ultrathin nanosheets dominated by {001} facets, and the thickness of nanosheets are about 10 nm. We find that the reaction time plays an important role in the growth mechanism and the hierarchical flower-like of anatase TiO2 was governed by a nucleation and nuclei growth-dissolution-recrystallization growth mechanism from time-dependent morphology evolution. The experimental parameters which influence the morphologies, such as reaction species and temperature, were further studied. The results show that the hierarchical flower-like nanostructures of anatase TiO2 nanosheets dominated by {001} facets exhibit higher photocatalytic activity in the degradation of methylene blue under ultraviolet–visible light irradiation, can be attributed to the synergetic effect of the architecture, high crystallinity, large specific surface areas, and the exposed highly activity {001} facets of the photocatalysts.

Synthesis of three-dimensional flower-like hierarchical ZnO nanostructure and its enhanced acetone gas sensing properties

A three-dimensional (3D) flower-like hierarchical ZnO nanostructure was successfully synthesized via a facile and efficient hydrothermal method. The sample was characterized by XRD, FESEM, Raman, UV–vis DRS and Photoluminescence (PL) techniques. The XRD pattern revealed that the sample was well-crystallized in a hexagonal wurtzite structure. FESEM images showed that the as-prepared ZnO exhibited a nanosheet-assembled hierarchical flower-like ZnO nanostructure, which was self-assembled by thin and uniform nanosheets with a thickness of approximately 30 nm. Raman spectra exhibited that the sample kept the crystal structure of the bulk ZnO and possessed more surface defects. UV–vis spectra showed that a significant blue-shift in the absorption edge for the as-prepared ZnO as compared to the commercial ZnO. PL spectra indicated that the concentration of surface oxygen vacancies in the as-prepared ZnO was much higher than that of the commercial ZnO. Furthermore, the nanosheet-assembled flower-like ZnO nanostructure exhibited excellent gas sensing properties towards acetone, indicating that the as-prepared ZnO architecture is a promising material for gas sensors.

Template-free synthesis and photocatalytic properties of flower-like ZnOHF nanostructures

A facile one-step solution-based method with the assistance of N,N-dimethylformamide (DMF) has been developed to prepare well-dispersed hierarchical flower-like ZnOHF nanostructures, in which DMF acts not only as solvent but also as surface-functionalizing agent. The prepared ZnOHF are characterized for the structural and morphological properties by XRD, SEM and TEM. The SEM and TEM results indicate that the hierarchical ZnOHF nanoflowers are assembled by numerous nanowires. The amount of DMF and reaction time play crucial roles in the formation of hierarchical nanowires-assembled ZnOHF nanoflowers. After calcination, the ZnOHF is completely transformed into ZnO while the flower structures are perfectly retained. The hierarchical ZnOHF and ZnO nanoflowers exhibit specific surface areas up to 48.8m2/g and 71.2m2/g, respectively. The as-obtained ZnOHF and ZnO nanoflowers exhibit excellent UV light photocatalytic activity for photodegradation of Rhodamine B.

Synthesis of Fe3O4 flower-like hierarchical nanostructures with high adsorption performance toward dye molecules

3D assembly of iron oxide nanosheets with flower-like structures were synthesized via decomposition of different iron alkoxide precursors by heat treatment. The products were characterized by X-ray diffraction, scanning electronic microscopy and N2 adsorption/desorption isotherm, methods. The SEM results show that both samples have flower like structure but one of them is composed of smooth nanosheets and the other one of rough nanosheets. BET surface area and pore size distribution of samples were obtained using N2 adsorption data. The obtained nanostructured flower-like iron oxide act as highly effective sorbent for fast removal of organic dyes pollutants, such as Reactive Orange (RO), Reactive Yellow (RY) and Bismarck Brown (BB), from simulated sewage system. The adsorption equilibrium and kinetic data were modeled with classical and recently developed models.

Attomolar Level Detection of Raman Molecules with Hierarchical Silver Nanostructures Including Tiny Nanoparticles between Nanosized Gaps Generated in Silver Petals.

We developed a route for synthesizing Ag nanostructures with tunable morphologies for ultrasensitive surface-enhanced Raman spectroscopy. Through the consecutive addition of three reducing agents (i.e., 4-mercaptobenzoic acid, trisodium citrate, and ascorbic acid) to an aqueous solution of silver nitrate, hierarchical flower-like Ag nanostructures were produced. The nanostructures had Ag petals in which nanosized gaps were generated, and small Ag nanoparticles were incorporated within the gaps. Theoretically, the nanostructures exhibited highly enhanced electric fields in the outer-shell regions where the small Ag nanoparticles were densely located. Combining the enhanced field effect with resonance effect of a Raman-active molecule (methylene blue) at a specific wavelength, measurable Raman signals were obtained at concentrations as low as 100 attomolar (10(-16) M; corresponding to 10(-21) mol). Key factors were discussed for the synthesis of the Ag nanostructures while finely controlling the morphologies of hierarchical Ag nanostructures, thereby modulating the intensity of surface-enhanced resonance Raman spectroscopy (SERRS) signals. Therefore, this synthetic method produces highly promising nanostructures for SERRS-based applications.

Controllable synthesis of hierarchical flower-like ZnO nanostructures assembled by nanosheets and its optical properties

The uniform and regular hierarchical flower-like ZnO nanostructures assembled by nanosheets have been controllably synthesized by a facile and efficient solution route on a large scale without using any templates, substrate or seed layers. The results of the experiment indicated that reaction temperature, time and the molar ratio of Zn2+/OH− had a strong influence on the formation of the hierarchical flower-like ZnO nanostructures. ZnO with flower-like nanostructures can be controllable synthesized with appropriate temperature, time and the molar ratio of Zn2+/OH−. The optical properties of the as-synthesized ZnO were investigated by UV–Vis absorption and photoluminescence. Consequently, the value of the band gap for this kind of ZnO crystals was calculated to be 3.26eV and the ZnO nanostructures possess a relatively strong UV emission, violet emission and a blue emission. Moreover, The ZnO may be tempting for further application such as photocatalyst, gas sensors and UV lasers. The facile and efficient solution route has high potentials to synthesize ZnO crystals on a large scale for industry application.

Rapid room-temperature synthesis and visible-light photocatalytic properties of BiOI nanoflowers

Uniform hierarchical BiOI nanoflowers composed of nanoplates with rough surfaces have been synthesized by a mild and rapid room-temperature solution synthesis approach. The effects of reaction parameters on the formation of 3D flower-like nanostructure were discussed. The morphology variations of the nanostructures were achieved by simply varying the reaction parameters in the system. The photocatalytic properties of the obtained samples for photodegradation of RhB dye under visible light irradiation were investigated, indicating that the flowerlike BiOI hierarchical nanostructure exhibits much higher photocatalytic activity than the sphere-like BiOI nanostructures owing to the larger surface areas, higher light absorption, and better photo-induced charge separation.