Flower-like Microstructures Research Articles

Synergistic effect of oxygen vacancy and nitrogen doping on enhancing the photocatalytic activity of Bi2O2CO3 nanosheets with exposed {0 0 1} facets for the degradation of organic pollutants

Single-crystalline bare Bi2O2CO3 (BOC) nanosheets with exposed {001} facets and nitrogen-doped Bi2O2CO3 (NBOC) flower-like microstructures were synthesized by a simple hydrothermal method. The nitrogen-doped Bi2O2CO3 flower-like microstructures with oxygen vacancy (UV-NBOC) were obtained by irradiating the NBOC microstructures with UV light for 2h in ethanol. The UV–vis diffuse reflectance spectra showed that the NBOC and UV-NBOC nanosheets exhibit an obvious red shift in light absorption band compared with the pure BOC nanosheets. Rhodamine B (RhB) was chosen as a model organic pollutant to verify the influence of oxygen vacancy and nitrogen doping on the photocatalytic activity of Bi2O2CO3 under simulated solar light irradiation. Judging from the kinetics of RhB photodegradation over the synthesized samples, a synergistic effect between oxygen vacancy and nitrogen doping was found with a remarkable increase (more than 10 and 2 times) in the photocatalytic activity of UV-NBOC compared with BOC and NBOC, respectively. Moreover, the UV-NBOC also exhibited an excellent cyclability and superior photocatalytic activity toward degradation of other organic pollutants (methylene blue, Congo red, Bisphenol A) under simulated solar light irradiation.

MoS2 microflowers based electrochemical sensing platform for non-enzymatic glucose detection

The detection of glucose plays a critical role in the areas of clinical diagnosis, food analysis, and biotechnology. Here, a MoS2 mircoflower based non-enzymatic glucose sensing strategy was suggested. The MoS2 microflowers were synthesized by hydrothermal method using cetyltrimethylammonium bromide (CTAB) as surfactant and fabricated a non-enzymatic glucose biosensor. The experimental results showed that the prepared MoS2 were flower-like microstructures. Moreover, when pH = 8, concentration of CTAB is 16 mM, and annealing temperature is 500 °C, the MoS2 microflowers is more suitable to fabricate electrode. Electrochemical tests showed that the electrode exhibited synergistic electrocatalytic activity with a high sensitivity of 570.71 μA mM−1. A good linear relationship between the anodic peak current and glucose concentration was obtained in the range from 0 to 30 mM. This work puts the flower-like MoS2 materials into application as the electrochemical sensing platform for non-enzymatic glucose detection.

Cleaner production in the Shea industry via the recovery of Spent Shea Waste for reuse in the construction sector

The Shea industry is catching major international attention in recent times because of its socioeconomic value, tremendous potential of ensuring food security as well as its wide-ranging industrial applications. The increased demand for the Shea butter product, which has led to the commercialization of various Shea butter extractive plants without appropriate mechanisms of dealing with the massive spent Shea waste generated, has necessitated the current investigation. Instrumental methods were used to study the suitability of recovering spent Shea waste for reuse in the construction sector towards a cleaner industrial production. The X-rays fluorescence analysis of this waste shows K (2.11 wt.%), Al (0.37 wt.%), Ca (0.36 wt.%), Si (0.35 wt.%) and Mg (0.10 wt.%) as key replacement cations at appreciable levels and a good diversity of inorganic fluxes at trace levels. Infrared and ultimate analyses of spent Shea waste revealed a largely organic materials with well-defined organic functional group bands at 3369 cm−1 2924 cm−1, 2856 cm−1, 1741 cm−1, 1616 cm−1, 1452 cm−1, 1369 cm−1, 1033 cm−1, 756 cm−1 and 640 cm−1. Its pore forming ability was demonstrated via the 76 wt.% reduction in weight at 800 °C firing temperature. The broad differential thermal analysis exothermic peak and the estimated higher heating value of 19.55 MJ/kg shows an excellent biofuel waste. X-ray diffraction and scanning electron microscopy studies revealed the varying flower-like polycrystalline microstructures of this waste. The various characterization studies portrayed spent Shea waste as suitable materials for reuse in improving clay brick making economically. Consequently, the implementation of mechanisms for the widespread reusing of spent Shea waste material towards a cleaner production in the Shea industry is highly recommended.

Electrostatic spray deposition of Ca3Co4O9 + δ layers to be used as cathode materials for IT-SOFC

In this paper, the deposition of Ca3Co4O9+δ layers on CGO substrates using electrostatic spray deposition (ESD) technique, starting from calcium and cobalt nitrates as precursor salts, is reported. The microstructure was investigated as a function of process parameters such as nozzle-to-substrate distance, solvent composition, substrate temperature, flow rate and deposition time, based on an upper and a lower value. Films with controlled microstructures were obtained after annealing at 880°C for 2h in air. The formation of Ca3Co4O9+δ was confirmed by X-ray diffraction, which also showed evidence of Co3O4 traces. As shown by in-situ X-ray diffraction, Ca3Co4O9+δ starts to form at 625°C and decomposes at 950°C, but the transformation is reversible. Interestingly, the initial morphology of the films was maintained after annealing at either 700 or 880°C, with the appearance of faceted crystals forming a gypsum flower-like microstructure. AC impedance spectroscopy was carried out at intermediate temperatures (600–800°C) under air on 2 batches of symmetrical cells based on ESD and screen-printed electrodes, respectively. This work confirmed the beneficial impact of the ESD technique. The area-specific resistance was improved by at least 23% at 600°C and 40% at 800°C for the sample prepared by ESD compared to the reference one prepared by screen printing. This improvement was explained by a better interface between the electrode and the electrolyte.

High open voltage and superior light-harvesting dye-sensitized solar cells fabricated by flower-like hierarchical TiO2 composed with highly crystalline nanosheets

The morphology, microstructure and crystallography of titanium dioxide (TiO2) have great effect on the photoelectric performance of dye-sensitized solar cells (DSSCs). Herein, flower-like 3D TiO2 microstructures based on well-defined high-crystalline nanosheets are synthesized through a facile hydrothermal method. Especially, morphological evolution process and mechanism of this hierarchical structure are investigated. Due to the highly crystalline nature and smaller surface area of these nanosheets, the corresponding device shows an extremely high open-current voltage up to 0.84 V, which results from the less electron recombination. When applied as a scattering layer on top of the nanoparticle layer, the power conversion efficiency (PCE) can be significantly improved and give birth to a PCE value of 9.6%, which is 24.6% higher than that of an analogous device using nanoparticles (NP) (7.7%). As reflected by diffusion reflection spectra, intensity of the modulated photocurrent/photovoltage spectroscopy (IMPS/IMVS) and electrochemical impedance spectra (EIS), this hierarchical structure can not only enhance light harvesting, but also reduce electron recombination, facilitate electron transport and improve electron collection efficiency.

Morphology-tunable synthesis of ZnO microstructures under microwave irradiation: formation mechanisms and photocatalytic activity

The morphologies and surface conditions of ZnO microstructures have been controlled facilely via a microwave-assisted one-pot synthetic route by varying the ammonia concentration of the reaction mixture. Ammonia affects the nucleation, growth, and hydrolysis kinetics of a zinc glycerolate intermediate to induce shape variation from flower-like ZnO microstructures to various ZnO twin microstructures with a preferred exposure of ± (0001) polar planes. The as-prepared ZnO microstructures are mesoporous, as they have large specific surface areas and high specific pore volumes that have resulted from the microwave-assisted fast hydrolysis of the zinc glycerolate intermediate microstructures. Owing to the novel features of microwaves, the ZnO microstructures have numerous microcracks and wrinkles on their surfaces and show characteristic defect-driven orange emission, whose intensity increases with the specific surface area. The photocatalytic degradation rate constant of rhodamine B via our prepared ZnO microstructures has been found to increase linearly with the specific surface area, the specific pore volume, and the polar-surface exposure. Our simple and rapid microwave-assisted synthetic method is considered to be beneficial to the development of morphology-controlled metal oxides that are applicable for eco-friendly waste-water treatments.

Microstructure, growth process and enhanced photocatalytic activity of flower-like ZnO particles

A simple hydrothermal process was developed to synthesize flower-like ZnO microstructures that exhibited excellent photocatalytic activity.

Lithium‐Ion Batteries: 3D Interconnected Networks of Graphene and Flower‐Like Cobalt Oxide Microstructures with Improved Lithium Storage (Adv. Mater. Interfaces 1/2016)

In article number 1500419, M. M. Shaijumon and co-workers fabricate a completely inter-connected three dimensional reduced graphene oxide (rGO)–cobalt oxide composite material with unique flower-like cobalt oxide microstructures uniformly embedded in a graphene hydrogel matrix (CoO-GHG). The resulting synergistic improvement of porosity and conductivity of the composite material leads to significantly enhanced electrochemical performance as an anode for lithium-ion batteries.

One-step room temperature rapid synthesis of Cu2Se nanostructures, phase transformation, and formation of p-Cu2Se/p-Cu3Se2heterojunctions

A tetragonal Cu2Se film containing a well-aligned nanosheet array with scattered 3D flower-like microstructures on top was synthesized for the first time by a rapid one-step low-energy route, which is beneficial for large scale industrial production due to savings in energy, time and expensive instruments. Phase transformation occurred after scraping the film from the Cu substrate, and heating or grinding the Cu2Se powder in air. The Cu2Se/Cu3Se2 composite containing p-Cu2Se/p-Cu3Se2 heterojunctions was obtained by simply calcining the Cu2Se in air at 300 °C for 3 h. The composite has enhanced gas sensing properties towards acetone gas and a lower band gap energy compared to Cu2Se.

Hierarchical flower-like Co–Cu mixed metal oxide microspheres as highly efficient catalysts for selective oxidation of ethylbenzene

The selective oxidation of alkanes and alkylaromatics to corresponding alcohols, ketones or carboxylic acids is of great importance for the production of high added-value raw materials in the fine chemical industry. The design and synthesis of cost-effective and recyclable heterogeneous oxidation catalysts has become one of the most active research areas. In this work, a series of novel Al2O3@Co–Cu–Al mixed metal oxide (Al2O3@CoCuAl-MMO) catalysts with hierarchical flower-like microstructure were successfully prepared via a Co–Cu–Al layered double hydroxide precursor route, and their catalytic performance was investigated in the liquid-phase selective oxidation of ethylbenzene using tert-butyl hydroperoxide as oxidant without the addition of any organic solvents. The characterization results revealed that the incorporation of copper into the MMO could induce the formation of the interactions between the Co–Cu species, and thus catalytic performance of as-formed Al2O3@CoCuAl-MMO catalysts was significantly promoted. In the selective oxidation of ethylbenzene, a high conversion of 92.8% with an acetophenone selectivity of 89.4% was achieved over the Al2O3@CoCuAl-MMO catalyst with a Cu/(Cu+Co) molar ratio of 0.25. The high catalytic efficiency was attributed mainly to the synergistic effect between highly dispersed active Co and Cu species. More importantly, the obtained catalysts having good recyclability and stability displayed good catalytic performance in the oxidation of other alkanes and alkylaromatics including 1,2,3,4-tetrahydronaphthalene, toluene, cumene, and methylcyclohexane.

Laser ablation processing of zinc sheets in hydrogen peroxide solution for preparing hydrophobic microstructured surfaces

Hydrophobic microstructured surfaces were prepared by nanosecond (ns) and femtosecond (fs) laser ablation of zinc sheets in hydrogen peroxide aqueous solution. It was found that ZnO and Zn(OH)2 were generated after ns or fs laser ablation. The ns laser-ablated sample, on which clustered flower-like microstructures composed of nanoneedles occurred, exhibited superhydrophobicity with a water contact angle (WCA) of 158.5° and a water sliding angle (WSA) of 4.3°. In contrast, the fs laser-ablated sample, which was covered with non-directional flaky nanostructures, showed high hydrophobicity with a WCA of 145.7° and a WSA of 12.5°. The one-step method proposed here may be useful for fabricating self-cleaning functional surfaces and devices.

Formation and self-assembly growth of palladium nanospheres into flowerlike microstructures using hydrogen peroxide as a sole reducing and shape-controlling agent

A novel and facile green synthetic method for creating flowerlike palladium microstructures (FPdµSTs) using hydrogen peroxide (H2O2) as a sole reducing and shape-controlling agent was developed. FPdµSTs with particle size in the range of 1–5 μm were successfully synthesized. Morphology (size and shape) and complexity of the FPdµSTs could be tuned through the synthetic conditions (i.e., concentrations of H2PdCl4 and H2O2). H2O2 played an important role in creating palladium microstructures by reduction of H2PdCl4 under acidic condition. The time-dependent investigation on the particle growth suggested that the FPdµSTs evolved from spherical palladium nanoparticles with a particle size of 3 nm. The small particles, which were formed at the early stage of the reaction, aggregated and grew into complex flowerlike microstructures.

Electrochemical Synthesis and Deposition of Surface-Enhanced Raman Scattering-Active Silver Microstructures on a Screen-Printed Carbon Electrode

We demonstrated a series of Ag microstructures with controlled morphologies directly deposited on a screen-printed carbon electrode by using electrochemical procedures in the presence of different electrolytes. Scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and high-resolution X-ray diffractometry were used for characterizing as-prepared Ag substrates. Thereafter, the potential of the flower-like Ag microstructures for use in surface-enhanced Raman scattering (SERS) applications was investigated. The flower-like Ag microstructures provided a more intense SERS signal because of extremely intense local electromagnetic fields. The enhancement factor value was approximately 1.2 × 106 for 4-mercaptobenzoic acid molecules. The percentage of relative standard deviation of SERS signals was lower than 2.1%. Determining the SERS spectra of 4,4′-dimercapto-azobenzene, 5,5′-dithiobis-2-nitrobenzoic acid, adenine, and single-stranded DNA (fumarylacetoacetate hydro...

The role of amine derivatives in the formation of hierarchical Pt micro/nanostructures

We discussed the formation of platinum hierarchical micro/nanostructure by varying the synthesis time using two amine derivatives, e.g. Monoethanolamine (MEA) and Diethanolamine (DEA) as the reducing agent. This work shows that the amine derivatives play a crucial role in controlling the reducing rate as Pt synthesised with DEA exhibited the fastest growth process whilst the synthesis time influences the development of Pt anisotropic structures. With a shorter synthesis time of 5 h, both particles synthesised using MEA and DEA exhibit small flower-like structures, while a larger network of flower-like microstructure was established at 9 h. The optimum condition for Pt assisted MEA and DEA is 7th hour for MEA and 5th hour for DEA. The particles produced using DEA during the 5th hour of synthesis time had a large electrochemical surface area (5.90 cm−2g−1), high catalytic activity and greater tolerance against CO adsorption. For particles synthesised with MEA, at the 7th hour, the reaction produces bigger flower-like particles comprised of collective triangular petals having 4.88 cm−2g−1 electrochemical surface areas and exhibit greater stability at a longer period.

Synthesis and Characteristics of Hierarchical Co3O4 Powders

Co3O4 samples with hierarchical structure were synthesized successfully by the morphology-conserved transformation method. The XRD and XPS results show that the obtained samples have the typical spinel Co3O4 phase. The FT-IR spectrum shows that the precursors consist of Co–EG coordination polymer. The SEM images show that the obtained samples have the morphology of flower-like microspheres. The authors found that the key step of the obtaining of hierarchical Co3O4 flower-like microspheres by the morphology-conserved transformation method is to construct flower-like microstructures of the cobalt-containing precursors via manipulating the synthetic parameters in a facile ethylene glycol–mediated solvothermal reaction.

Template-free biosynthesis of flowerlike CuO microstructures using Cinnamomum camphora leaf extract at room temperature

Flower-like Copper Oxide microstructures (CuOMFs) are fabricated through a simple bioreduction route using Cinnamomum Camphora (C. camphora) leaf extract at room temperature without the addition of any templates and additives. X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM and TEM), and energy dispersed X-ray were used to characterized and verify the nature of the CuOMFs. The results showed that the CuOMFs of average size 1.3±2.0µm consisted of several 2D nanorods. The plant extract acted as both reducing and stabilizing agent.

Highly stabilized and rapid sensing acetone sensor based on Au nanoparticle-decorated flower-like ZnO microstructures

Hierarchical flower-like ZnO microstructures were synthesized by a two-step hydrothermal method. Flower-like ZnO microstructures were made up of ZnO nanorods (NBs) with the diameters of about 100 nm. Then Au nanoparticles (NPs) with the diameter of 10–20 nm were decorated on the surface of flower-like ZnO microstructures by the wet decorating process. The properties of the sensing material were analyzed with X-Ray diffraction (XRD), Scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDX), Transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). Gas sensing device was prepared by thick film technology and tested primarily for acetone gas at different testing temperatures as well as concentrations. At the optimum operating temperature of 280 °C the sensor showed a good response and rapid response-recovery time. Furthermore, because of the stable microstructure the sensor had an excellent stability for six months.

Shape-Controlled Synthesis of NiCo2 O4 Microstructures and Their Application in Supercapacitors.

The shape-controlled synthesis of NiCo2 O4 microstructures through a facile hydrothermal method and subsequent calcinations was explored. By employing CoSO4 , NiSO4 , and urea as the starting reactants, flower-like NiCo2 O4 microstructures were obtained at 100 °C after 5 h without the assistance of any additive and subsequent calcination at 300 °C for 2 h; dumbbell-like NiCo2 O4 microstructures were prepared at 150 °C after 5 h in the presence of trisodium citrate and subsequent calcination at 300 °C for 2 h. The as-prepared NiCo2 O4 microstructures were characterized by X-ray powder diffraction, field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, and (high-resolution) transmission electron microscopy. Both the flower-like and dumbbell-like NiCo2 O4 microstructures could be used as electrode materials for supercapacitors, and they exhibited excellent electrochemical performance, including high specific capacitance, good rate capability, and excellent long-term cycle stability. Simultaneously, the shape-dependent electrochemical properties of the product were investigated.

Porous hematite microflowers toward the adsorption of organic pollutants from water

Porous flower-like hematite microstructures assembled with porous nanosheets were prepared by thermal decomposition of a precursor which was obtained using FeCl3·6H2O, urea, and polyvinylpyrrolidone (PVP) in the solvent of ethylene glycol (EG) via a simple solution method. Because of the high specific surface area and porous structure, such α-Fe2O3 microflowers showed excellent adsorption performances for the Congo red in wastewater treatment with a maximum removal capacity of 628.9mg/g. The adsorption rate and adsorption isotherm were also investigated, and were well represented by the Langmuir model. These hematite flowers may hold great potential as environmentally friendly dye adsorbent candidate in decontamination of water.

3D porous flower-like SnO2 microstructure and its gas sensing properties for ethanol

The porous flower-like SnO2 architecture, consisting of numerous aggregative nanosheets was successfully synthesized via a facile hydrothermal process and subsequent calcination. The morphology and gas-sensing property were mainly studied. The pores on its surface provided much active center and gas diffusion ways. The sensor based on this architecture showed the high response, fast response/recovery time and good selectivity toward ethanol at 300°C. The sensitivity was about 208 and the response-recovery time were around 8 and 7s for 500ppm ethanol, respectively. The results indicated that porous flower-like SnO2 architecture was a potential candidate for fabricating effective ethanol sensor. Furthermore, the possible growth mechanism and the ethanol sensing mechanism of the architecture were discussed, too.