Flower-shaped ZnO Nanostructures Research Articles

Electrochemical Performance of Flower-like ZnO Nanostructure Crystal for Supercapacitor Electrode Applications

straightforward, easy and low-cost process using cetyltrimethylammonium bromide (CTAB) as a templated sonochemical production method was used to prepare ZnO nanostructures with the appearance of flowers. The morphological characteristics of ZnO materials have a more significant impact on variables like the CTAB template and sonochemical reaction time. The advantage of the flower-like ZnO materials is the more active reaction centre, which improves redox processes and results in outstanding electrochemical attributes like greater specific capacitance, excellent rate capability and better cyclic stability. The specific capacitance of the flower-shaped ZnO nanostructures (ZnO-2) from the cyclic voltammetric (CV) analysis was found to be 425 F g–1 at a scan rate of 5 mV s–1 and the charge/discharge study renders the specific capacitance is 426 F g–1 at a current density of 1 Ag–1. After 3000 CV cycles at a scan rate of 100 mV s–1, 89% of the initial capacitance still was retained in the long-term cyclic stability analysis. The distinctive flower-like ZnO nanostructures can be extended more for supercapacitor device applications.

Seedless and surfactant-free growth of flower-shaped ZnO nanostructures: Growth evolution mechanism

In this work, an innovative seedless and surfactant-free chemical bath deposition (CBD) method at low temperature was applied to obtain flower-shaped ZnO nanostructures (FZONSs) on glass and [Formula: see text]-type silicon substrates for the first time. Structural properties of these FZONSs were examined. The NSs were produced from zinc nitrate hexahydrate and hexamethylenetetramine, HMTA solution without any catalyst, template, or seed layer. An electric soldering iron pen was used to simultaneously heat the substrate and aqueous mixture of the constituents to grow the FZONSs. Field emission scanning electron microscopy images of the samples showed the presence of three-dimensional (3D) flower-shaped nanomorphology. Energy-dispersive X-ray spectroscopy detected the right trace elements in the FZONSs. X-ray diffraction analysis of the as-grown samples confirmed the existence of high purity nanocrystalline hexagonal phase of ZnO with preferred growth along (002) lattice planer orientation. The growth of ZnO nanorods into unified flower-like morphology was interpreted using a nucleation dissolution-mediated recrystallization mechanism. The fabricated FZONSs may provide potential in various applications including advanced catalysts, sensing devices, and solar cells.

Synthesis and characterization of ZnO nanoflowers under temperature effect

Synthesis of flower-shaped ZnO nanostructures composed of hexagonal ZnO nanorods was achieved by the solution process using zinc acetate dihydrate and sodium hydroxide at very low temperature of 90 8C in 30 min. The individual nanorods are of hexagonal shape with sharp tip, and base diameter of about 300–350 nm. Detailed structural characterizations demonstrate that the synthesized products are single crystalline with the wurtzite hexagonal phase, grown along the [0 0 0 1] direction. The IR spectrum shows the standard peak of zinc oxide at 523 cm-1. Raman scattering exhibits a sharp and strong E2 mode at 437 cm-1 which further confirms the good crystallinity and wurtzite hexagonal phase of the grown nanostructures. The photoelectron spectroscopic measurement shows the presence of Zn, O, C, zinc acetate and Na. The binding energy ca. 1021.2 eV (Zn 2p3/2) and 1044.3 eV (Zn 2p1/2), are found very close to the standard bulk ZnO binding energy values. The O 1s peak is found centered at 531.4 eV with a shoulder at 529.8 eV. Room-temperature photoluminescence (PL) demonstrate a strong and dominated peak at 381 nm with a suppressed and broad green emission at 515 nm, suggests that the flower-shaped ZnO nanostructures have good optical properties with very less structural defects.

Direct Growth of Flower-Shaped ZnO Nanostructures on FTO Substrate for Dye-Sensitized Solar Cells

The proposed work reports that ZnO nanoflowers were grown on fluorine-doped tin oxide (FTO) substrates via a solution process at low temperature. The high purity and well-crystalline behavior of ZnO nanoflowers were established by X-ray diffraction. The morphological characteristics of ZnO nanoflowers were clearly revealed that the grown flower structures were in high density with 3D floral structure comprising of small rods assembled as petals. Using UV absorption and Raman spectroscopy, the optical and structural properties of the ZnO nanoflowers were studied. The photoelectrochemical properties of the ZnO nanoflowers were studied by utilizing as a photoanode for the manufacture of dye-sensitized solar cells (DSSCs). The fabricated DSSC with ZnO nanoflowers photoanode attained reasonable overall conversion efficiency of ~1.40% and a short-circuit current density (JSC) of ~4.22 mA cm−2 with an open circuit voltage (VOC) of 0.615 V and a fill factor (FF) of ~0.54. ZnO nanostructures have given rise to possible utilization as an inexpensive and efficient photoanode materials for DSSCs.

Gas sensing properties of ZnO nanostructures (flowers/rods) synthesized by hydrothermal method

Here, we report the hydrothermal synthesis of flower-shaped ZnO nanostructures and investigated their morphology-dependent gas sensing properties. Scanning electron microscope (SEM) study confirmed the formation of two kinds of floral structures. At short reaction time, flower-like structures (2–3 μm in size) composed of nanoparticles are formed, whereas floral assemblies (˜ 5 μm) of nanorods are formed at long reaction time. X-ray diffraction (XRD) confirmed the formation of the hexagonal wurtzite structure of ZnO. The average crystallite size of prepared nanoflowers and nanorods were found to be 21 nm and 43 nm, respectively. These results are supported by transmission electron microscopy (TEM). The band gap of ZnO nanostructures was calculated from the UV–vis absorption spectrum and found to be 3.0 eV and 3.19 eV for ZnO nanoflowers and nanorods, respectively. Broad absorption peak in the visible region of photoluminescence (PL) spectra confirmed the presence of oxygen vacancies in both specimens. Furthermore, morphology dependent gas sensing property was investigated for ethanol, benzene, carbon monoxide, and nitrogen dioxide at different operating temperatures and concentrations. Although both morphologies have shown good sensitivity and selectivity towards NO2 at ppb, the response of nanoflower was higher than that of nanorods, which was attributed to its relatively higher surface area and amount of surface defects.

Fabrication and Characterization of Dye-Sensitized Solar Cells Based on Flower Shaped ZnO Nanostructures.

Herein, we report a facile synthesis, characterization and dye sensitized solar cell (DSSC) application of flower-shaped ZnO nanostructures. The flower-shaped ZnO nanostructures were synthesized by low-temperature hydrothermal process and characterized in detail by several techniques. The detailed morphological studies confirmed that the flower-shaped structures are formed by the accumulation of several nanoneedles which are axially arranged through their bases in a special fashion that they made flower-like morphologies. The compositional, structural and optical characterizations revealed that the synthesized flowers possess high purity, well-crystallinity with the wurtzite hexagonal phase and good optical properties. The synthesized flower-shaped ZnO nanostructures were used as photoanode to fabricate DSSC which attained a reasonable solar to electrical conversion efficiency of ~1.1%, open-circuit current (VOC) of 0.611 V, short circuit current (JSC) of 3.53 mA/cm2 and fill factor (FF) of 0.51.

Hydrothermal Synthesis and Responsive Characteristics of Hierarchical Zinc Oxide Nanoflowers to Sulfur Dioxide

Sulfur dioxide, SO2, is one of the most important decomposition byproducts of sulfur hexafluoride, SF6, under partial discharge in GIS apparatus. The sensing performances of semiconductor gas sensors can be improved by morphology tailoring. This paper reported the synthesis method, structural characterization, and SO2responsive characteristics of hierarchical flower-shaped ZnO nanostructures. Hierarchical ZnO nanoflowers were successfully prepared via a facile and simple hydrothermal method and characterized by X-ray powder diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy, respectively. Planar chemical gas sensor was fabricated and its responsive characteristics towards SO2were systematically performed. The optimum operating temperature of the fabricated sensor was measured to be about 260°C, and the corresponding maximum responses were 16.72 and 26.14 to 30 and 60 ppm of SO2. Its saturated gas concentration was 2000 ppm with a response value of 67.41. Moreover, a quick response and recovery feature (7 s and 8 s versus 80 ppm of SO2) and good stability were also observed. All results indicate that the proposed sensor is a promising candidate for detecting SF6decomposition byproduct SO2.

Synthesis and characterisation of flower shaped Zinc Oxide nanostructures and its antimicrobial activity

Flower shaped Zinc Oxide nanostructures was synthesized using a simple method without using any structure directing agents. Elemental analysis, crystalline nature, shape and size were examined using Powder X-ray Diffraction (XRD), scanning electron microscopy (SEM), High Resolution Transmission Electron Microscopy (HRTEM) and Energy Dispersive X-ray Spectroscopy (EDAX). XRD revealed the formation of hexagonal ZnO nanostructures. SEM and TEM analyses revealed the formation of crystalline ZnO flowers in which a bunch of ZnO nanorods assembled together to form a leaf like structure followed by flower shaped ZnO nanostructures. Thus synthesised ZnO nanostructures showed good antimicrobial activity towards gram-positive bacteria Staphylococcus aureus as well as gram-negative bacteria Escherichia coli with a MIC/MBC of 25mg/L.

Hydrothermally grown ZnO nanoflowers for environmental remediation and clean energy applications

Well-crystalline flower-shaped ZnO nanostructures were synthesized by simple hydrothermal process at low-temperature of 145°C and utilized as a photocatalyst and photo-anode material for photocatalytic degradation and dye-sensitized solar cell applications, respectively. The detailed morphological and the structural characterizations revealed that the synthesized products were flower-shaped, grown in very high-density, and possessed well-crystalline wurtzite hexagonal phase. The chemical composition confirmed the pure phase and good optical properties of as-synthesized ZnO flowers. The as-synthesized ZnO flowers were used as an efficient photocatalyst for the photocatalytic degradation of Rhodamine B which exhibit ∼84% degradation within 140min. Moreover, the as-synthesized ZnO flowers were utilized as photo-anode material for the fabrication of dye-sensitized solar cells (DSSCs) which exhibited overall light-to-electricity conversion efficiency of ∼1.38%, open-circuit current (VOC) of 0.621V, short-circuit current (JSC) of ∼3.52mA/cm2 and fill factor (FF) of 0.64.

Propeller-Shaped ZnO Nanostructures Obtained by Chemical Vapor Deposition: Photoluminescence and Photocatalytic Properties

Propeller-shaped and flower-shaped ZnO nanostructures on Si substrates were prepared by a one-step chemical vapor deposition technique. The propeller-shaped ZnO nanostructure consists of a set of axial nanorod (50 nm in tip, 80 nm in root and 1 μm in length), surrounded by radial-oriented nanoribbons (20–30 nm in thickness and 1.5 μm in length). The morphology of flower-shaped ZnO nanostructure is similar to that of propeller-shaped ZnO, except the shape of leaves. These nanorods leaves (30 nm in diameter and 1–1.5 μm in length) are aligned in a radial way and pointed toward a common center. The flower-shaped ZnO nanostructures show sharper and stronger UV emission at 378 nm than the propeller-shaped ZnO, indicating a better crystal quality and fewer structural defects in flower-shaped ZnO. In comparison with flower-shaped ZnO nanostructures, the propeller-shaped ZnO nanostructures exhibited a higher photocatalytic property for the photocatalytic degradation of Rhodamine B under UV-light illumination.

Highly-sensitive cholesterol biosensor based on well-crystallized flower-shaped ZnO nanostructures

This paper reports the fabrication of highly-sensitive cholesterol biosensor based on cholesterol oxidase (ChO x) immobilization on well-crystallized flower-shaped ZnO structures composed of perfectly hexagonal-shaped ZnO nanorods grown by low-temperature simple solution process. The fabricated cholesterol biosensors reported a very high and reproducible sensitivity of 61.7 μA μM −1 cm −2 with a response time less than 5 s and detection limit (based on S/N ratio) of 0.012 μM. The biosensor exhibited a linear dynamic range from 1.0–15.0 μM and correlation coefficient of R = 0.9979. A lower value of apparent Michaelis–Menten constant ( K m app), of 2.57 mM, exhibited a high affinity between the cholesterol and ChO x immobilized on flower-shaped ZnO structures. Moreover, the effect of pH on ChO x activity on the ZnO modified electrode has also been studied in the range of 5.0–9.0 which exhibited a best enzymatic activity at the pH range of 6.8–7.6. To the best of our knowledge, this is the first report in which such a very high-sensitivity and low detection limit has been achieved for the cholesterol biosensor by using ZnO nanostructures modified electrodes.

ZnO nanostructured microspheres and grown structures by thermal treatment

Synthesis of flower-shaped ZnO nanostructures composed of ZnO nanosticks was achieved by the solution process using zinc acetate dihydrate, sodium hydroxide and polyethylene glycol-20000 (PEG-20000) at 180°C for 4 h. The diameter of individual nanosticks was about 100 nm. Detailed structure characterizations demonstrate that the synthesized products are wurtzite hexagonal phase, grown along the [001] direction. The infrared (IR) spectrum shows the standard peak of zinc oxide at 571 cm−1. Raman scattering exhibits a sharp and strong E 2 mode at 441 cm−1 which further confirms the good crystal and wurtzite hexagonal phase of the grown nanostructures.

Low-Temperature Growth of Flower-Shaped UV-Emitting ZnO Nanostructures on Steel Alloy by Thermal Evaporation

Flower-shaped ZnO nanostructures, containing the triangular-shaped petals (sharpened tips and wider bases) have been achieved by simple thermal evaporation of high purity metallic zinc powder in the presence of oxygen at 440 degrees C on steel alloy substrate without the use of metal catalyst or additives. Detailed structural studies confirm that the obtained flower-shaped nanostructures are single crystalline and possesses a wurtzite hexagonal structure, grown along the c-axis in the [0001] direction. Raman and room temperature photoluminescence analysis substantiate a wurtzite hexagonal phase with a good crystal quality and a strong UV emission at 378 nm, respectively, indicating few or no structural defects. Additionally, a detailed possible growth mechanism has also been discussed.

Synthesis and characterization of novel flower-shaped ZnO nanostructures

Flower-shaped ZnO nanostructures have been successfully fabricated via the oxidation of metallic Zn powder mixed with some Sn powder. Investigation results demonstrate that the ZnO flowers are made up of nanorods, nanosaws, or double-sided nanocombs. And all of these nano-structures are single crystal of wurtzite hexagonal phase. For the formation of such ZnO flower structures, the additive of tin powders is very important. They could be evaporated and oxidized to SnO x to affect the growth action in the experiment process. A possible mechanism has been supposed here to explain this phenomenon. Finally, the corresponding room-temperature photoluminescence has also been discussed in the paper.

Low temperature solution synthesis and characterization of ZnO nano-flowers

Synthesis of flower-shaped ZnO nanostructures composed of hexagonal ZnO nanorods was achieved by the solution process using zinc acetate dihydrate and sodium hydroxide at very low temperature of 90 °C in 30 min. The individual nanorods are of hexagonal shape with sharp tip, and base diameter of about 300–350 nm. Detailed structural characterizations demonstrate that the synthesized products are single crystalline with the wurtzite hexagonal phase, grown along the [0 0 0 1] direction. The IR spectrum shows the standard peak of zinc oxide at 523 cm −1. Raman scattering exhibits a sharp and strong E 2 mode at 437 cm −1 which further confirms the good crystallinity and wurtzite hexagonal phase of the grown nanostructures. The photoelectron spectroscopic measurement shows the presence of Zn, O, C, zinc acetate and Na. The binding energy ca. 1021.2 eV (Zn 2p 3/2) and 1044.3 eV (Zn 2p 1/2), are found very close to the standard bulk ZnO binding energy values. The O 1s peak is found centered at 531.4 eV with a shoulder at 529.8 eV. Room-temperature photoluminescence (PL) demonstrate a strong and dominated peak at 381 nm with a suppressed and broad green emission at 515 nm, suggests that the flower-shaped ZnO nanostructures have good optical properties with very less structural defects.

Flower-shaped ZnO nanostructures obtained by cyclic feeding chemical vapour deposition:structural and optical properties

Flower-shaped ZnO nanostructures were grown on Si(100) and Si(111) substrates by cyclicfeeding chemical vapour deposition without the use of a metal catalyst. The structuresobtained on the Si(100) substrate exhibited triangle-shaped leaves with lengths anddiameters in the ranges 300–400 and 90–130 nm, respectively. Uniformly shaped leaves withhexagonal facets originating from one centre were observed on the flower-shapedstructures grown on the Si(111) substrate. Transmission electron microscopy andselected area electron diffraction patterns showed that these structures are highlycrystalline, with the wurtzite hexagonal phase, and preferentially oriented in thec-axis direction. Unlike star-shaped ZnO nanostructures grown on Au-coated siliconsubstrates, the flower-shaped nanostructures showed sharp and strong UV emission at378 nm and broad and weak green emission at 520 nm, indicating a good crystal quality andfew structural defects.