Flower-like Microstructures Research Articles

Enriching the active sites of nanosheets assembled as flower-like MoS2 microstructure by controllable morphology for electrochemical hydrogen evolution reaction

With their tunable electronic structure, transition metal dichalcogenides offer a high surface area and enhanced active sites, making them a promising electrocatalyst for hydrogen production techniques. However, restacking of 2D layers and particle aggregation during material preparation negate its advantages. Herein, we developed a flower-like morphology with numerous molybdenum disulfide (1T/2H MoS2) nanosheet petals. The final formation and arrangements of MoS2 were validated through three distinct approaches: air (AD-M), vacuum (VD-M), and freeze-drying (FD-M). Interestingly, the drying phenomenon effectively alters the stacking and aggregation between the flower petals in the MoS2 and the electrocatalytic activity. Among the different drying processes, the FD-M exhibits minimal stacking and agglomeration between the nanoflowers. The FD-M exhibits remarkable catalytic activity in 1 M KOH for HER, reaching 10 mA cm−2 at a low overpotential (η10) of 198 mV and a small Tafel slope of 58.5 mV dec−1, which is lower than the AD-M (228 mV) and VD-M (215 mV). The FD process modulates the electronic structure of MoS2 by lowering stacking between layers, which effectively increases the ECSA and boosts the HER performance.

Synthesis of flower-like covalent organic frameworks for photocatalytic selective oxidation of sulfide

BackgroundCovalent organic frameworks (COFs)-based photocatalysts have garnered significant attention for their potential in highly efficient and selective sulfide oxidation. However, the current synthesis methods of COF-based catalysts involve complex multi-step procedures, and better methods need to be upgraded for synthesis. MethodsIn this study, a flower-like COF-based photocatalyst (f-COFs) was synthesized by one-pot method at room temperature using zinc chloride (ZnCl2) as catalyst. The photocatalytic performance of f-COFs was investigated using methyl phenyl sulfide as substrate. Significant FindingsZinc ions remain on the f-COFs synthesized by this method. EDX analysis and XPS techniques were used to confirm the presence of zinc ions. The presence of zinc ions controls the self-assembly of COFs to form unique flower-like microstructure. Its flower-like microstructure provides a strong light absorption capacity. At the same time, the recombination of charge is inhibited, thus promoting the energy and electron transfer during the photocatalytic reaction. These properties allow reactive oxygen species to be prevalent in the reaction process of f-COFs as a photocatalyst, driving the conversion of methyl phenyl sulfide to sulfoxide within 5 h with excellent performance of 95 % conversion and 99 % selectivity.

Polyaniline-coated flower-like iron oxide served as anode material for superior-performance lithium-ion batteries

Transition metal oxides applied in anode for lithium-ion batteries are susceptible to particle aggregation during the cycling test, resulting in a low capacity retention during cycling process. In this study, Fe2O3/polyaniline microflowers were prepared via a simple liquid-phase oxidation and calcination process followed by polyaniline coating. Several characterization techniques demonstrated their morphology and chemical composition. When applied in anode for lithium-ion batteries, Fe2O3/polyaniline microflowers exhibit an ultrahigh specific capacity of 1847.1 mAh g−1 over 100 cycles at 0.1 A/g. A high specific capacity of 619.8 mAh g−1 was achieved after 300 cycles at 1.0 A/g. The high performance is mainly due to the polyaniline coating and flower-like microstructures, which can mitigate the volume change, improve the electrical conductivity and cycling stability, and contribute to the rapid Li+ diffusion. This work provides a new route for synthesizing advanced-performance Fe2O3-based anode material.

Enhanced photocatalytic H2 production activity by loading Ni complex on flower-like MoS2 nanomaterials

BackgroundExploring efficient H2-production photocatalysts is very important for converting solar energy to chemical energy. Some approaches were developed to prevent the recombination of photogenerated electron-hole pairs, ultimately enhancing the photocatalytic H2 production activity. Methods3D flower-like MoS2 nanomaterials were surface-modified by the Ni complex as the redox mediator to make the composite photocatalysts. This work investigated the effect of zeta potential on the Ni-complex loading, charge separation, and photocatalytic H2 production activity of MoS2. Significant findingsThe Ni-complex with central cation can be loaded on MoS2 with negative zeta potential due to the columb attraction force. The photogenerated carriers can transfer from MoS2 to the central Ni ion of the complex due to the ligands-stabilized multiple oxidation states of Ni, leading to suppressed charge recombination. The FE-TEM mapping and XPS confirm the loading of Ni complex. The photoluminescence, photocurrent response, and EIS tests confirm the improved photoinduced charge separation of the Ni complex-modified photocatalyst. The flower-like microstructure of MoS2 provides a large specific surface area and high light absorption. The H2 production activity of MoS2-Ni complex photocatalyst (3320 μmol g−1 h−1) is higher than that of the pristine MoS2 photocatalyst (2576 μmol g−1 h−1).

ECL cytosensor for sensitive and label-free detection of circulating tumor cells based on hierarchical flower-like gold microstructures

The development of sensitive and efficient cell sensing strategies to detect circulating tumor cells (CTCs) in peripheral blood is crucial for the early diagnosis and prognostic assessment of cancer clinical treatment. Herein, an array of hierarchical flower-like gold microstructures (HFGMs) with anisotropic nanotips was synthesized by a simple electrodeposition method and used as a capture substrate to construct an ECL cytosensor based on the specific recognition of target cells by aptamers. The complex topography of the HFGMs array not only catalyzed the enhancement of ECL signals, but also induced the cells to generate more filopodia, improving the capture efficiency and shortening the capture time. The effect of topographic roughness on cell growth and adhesion propensity was also investigated, while the cell capture efficiency was proposed to be an important indicator affecting the accuracy of the ECL cytosensor. In addition, the capture of cells on the electrode surface increased the steric hindrance, which caused ECL signal changes in the Ru(bpy)32+ and TPrA system, realizing the quantitative detection of MCF-7 cells. The detection range of the sensor was from 102 to 106 cells mL−1 and the detection limit was 18 cells mL−1. The proposed detection method avoids the process of separation, labeling and counting, which has great potential for sensitive detection in clinical applications.

Ultrathin needle-like NiMoO4/MoO3 heterostructure for supercapacitor and overall water splitting applications

In this study, the morphology of NiMoO4/MoO3 heterostructure was adjusted by adding various amounts of polyvinylpyrrolidone (PVP) as soft-template agent during in-situ solvothermal growth on nickel foam. The electrochemical and physiochemical properties of the free-binder electrode were studied as a function of PVP contents. By adding a proper amount of PVP, the morphology of NiMoO4/MoO3 nanocomposites changed from the agglomerated spherical nanoparticles to the flower-like morphology with the well-distributed nanoneedle-like building blocks. The flower-like NiMoO4/MoO3 heterostructures showed the highest specific capacitance of 3626 Fg−1 at 1 A g−1 and a rate-capability of 76 % by the increase of current density from 1 to 5 A g−1. In alkaline water splitting application, the flower-like microstructure showed the excellent electrocatalytic activity including the low overpotentials of 169 and 318 mV for hydrogen and oxygen evolution reactions, respectively.

S doping in CoOHS modified hollow fiber membranes boosting electron transfer between activated PMS and pollutants in a continuous flow reactor

The surface-sulfurized CoAl-LDH (CoOHS) modified hollow fiber membranes (HFM@(PDA/PEI)@CoOHS) demonstrated excellent peroxymonosulfate (PMS) activation for oxytetracycline (OTC) degradation, with high removal efficiency and detoxification capacities, thanks to the coexistence of S-doping species, flower-like microstructures, and hollow fiber membrane support. Meanwhile, the hollow tube morphology of HFM@(PDA/PEI)@CoOHS is easily separated for recycling. With the combination of competitive radical quenching experiments, EPR, and electrochemical analysis, the 1O2 and enhanced electron transfer can be accounted for OTC oxidation. Therein, S doping species are able to promote the Co(III)/Co(II) redox cycle by forming more metastable catalyst/PMS* complexes to enhance electron transfer between OTC and PMS* complexes. A continuous flow reactor with hollow fiber membranes was used to evaluate the OTC removal in practice. Using computational fluid dynamics (CFD), the flow within the modified hollow fiber membrane was modeled. Additionally, HFM@(PDA/PEI)@CoOHS is recyclable after 5 cycles with a degradation efficiency of 86.17%. This research paves the way for an innovative strategy for designing continuous flow reactors functioning as PMS activators, opening up possibilities for practical applications in organic pollutant removal.

Interlayer spacing-controlled carnation flower-like microstructure of nickel-manganese layered double hydroxide for enhancing hybrid supercapacitor performance

Energy harvested from intermittent sources can be stored in supercapacitors for high-power delivery with long cycling stability. Binary layered double hydroxide (LDH) materials have great potential for hybrid supercapacitor applications owing to their mixed and tunable charges and layered structure. This study presents carnation flower-like, 3D micro-structured NiMn-LDH prepared by a facile single-step hydrothermal synthesis using hexamethylenetetramine to produce hydroxides. The 3D structure was assembled from ultrathin 2D NiMn-LDH nanosheets, and the largest interlayer spacing was obtained by optimizing synthesis parameters, such as Ni:Mn molar ratio and reaction temperature, ensuring a fast diffusion and thus the best energy storage performance. The optimized NiMn-LDH electrode delivered a high specific capacity of 612 C g−1 with an excellent rate capability of 67% at 20 A g−1 in a three-electrode test. An asymmetric device assembled using NiMn-LDH and reduced graphene oxide as positive and negative electrodes provided a high energy density of 60.0 Wh kg−1 and power density of 17.7 kW kg−1 with 90.4% capacity retention after 10,000 charge–discharge cycles. This superior result highlights the potential industrial applications, such as portable electronics and trams.

Silicon flower structures by maskless plasma etching

Silicon nano/microstructures are widely utilized in the semiconductor industry, and plasma etching is the most prominent method for fabricating silicon nano/microstructures. Among the variety of silicon nano/microstructures, black silicon with light-trapping properties has garnered broad interest from both the scientific and industrial communities. However, the fabrication mechanism of black silicon remains unclear, and the light absorption of black silicon only focuses on the near-infrared region thus far. Herein, we demonstrate that black silicon can be fabricated from individual flower-like silicon microstructures. Using fluorocarbon gases as etchants, silicon flower microstructures have been formed via maskless plasma etching. Black silicon forming from silicon flower microstructures exhibits strong absorption with wavelength from 0.25 μm to 20 μm. The result provides novel insight into the understanding of the plasma etching mechanism in addition to offering further significant practical applications for device manufacturing.

Electroplating of hydrophobic/hydrophilic ZnO nano-structural coatings on metallic substrates

In the present work, ZnO thin film is shown as a coating on an aluminum substrate. In order to synthesize ZnO thin films, electroplated Zn thin layers were thermally oxidized in atmospheric air for different times (1h–4h) at a fixed annealing temperature of 500 °C. The samples were characterized by scanning electron microscopy (FEG-SEM) equipped with energy dispersive x-ray analysis (EDX), a profilometer, x-ray diffraction (XRD), and Raman spectroscopy. The wettability properties of the synthesized films were evaluated by measuring the contact angle between the surface of the films and a deposited water drop (WCA). The FEG-SEM images show that the surface morphologies change throughout treatment time. The sample treated for 2 h shows flower-like microstructures with an average size of 100 μm, which are covered with spherical ZnO nanostructures with a size less than 50 nm. Measured surface roughness ranges from 5.800 μm to 6.560 μm. Layers thicknesses vary between 31 and 38 μm. Structural characterization by XRD demonstrates that the synthesized ZnO thin films were polycrystalline and have Wurtzite hexagonal structures, grown manly along the (101) plan. The estimated crystallite sizes are in the nanometric scale and reach their maximum value for the sample treated for 2 h. This annealing time corresponds to the low dislocation density (δ) and low lattice strain (ε), indicating fewer defects. The Raman analysis shows five normal vibrational modes, which correspond to the ZnO Wurtzite structure. It was possible to obtain both hydrophobic and hydrophilic surfaces; the shape and surface roughness of the as-prepared films had an impact on the results. The largest measured contact angle, of 97°, was obtained after annealing for 2 h at 500 °C.

Formation of floral microstructures of the refractory negative thermal expansion ceramic MgO-doped Zr2P2WO12 following acid corrosion

Refractory negative thermal expansion (NTE) materials can reduce stress when subjected to drastic temperature changes and therefore have potential applications in fire-fighting field. However, NTE ceramics are susceptible to impact damage due to their poor mechanical properties. We have found that treatment of a ceramic with hydrofluoric acid (HF) generated floral microstructures that enhanced the ceramic's impact resistance. Specifically, pellets of a refractory NTE ceramic, Zr2P2WO12 (ZWP) ceramics, containing various doping ratios of MgO) are fabricated and then treated with hydrofluoric acid (HF) to induce the formation of flower-like microstructures. Structural analyses show that the concentration of MgO in the ZWP pellets affects the morphology of the microstructures. The crystal orientation of ZWP appears after HF acid corrosion, and the formation of floral particles corresponded to the content of MgO. This investigation demonstrates that HF treatment can alter the microstructure of a refractory NTE ceramic and may have wide application for enhancing such ceramics' mechanical properties.

Thermo-optic response and mechanical properties of hybrid polyurethane elastomers via silicon group-induced microphase separation evolution

In this study, silicon hybrid polyurethane elastomers (SPUs) with flower-like microstructure were constructed by a two-step method according to incorporating diphenylsilanediol (DPSD) into hard segments. The reinforced microphase separation of SPUs was estimated by combining Fourier transform infrared spectrometer (FT-IR) characterization with differential scanning calorimeter (DSC) and dynamic mechanical analyzer (DMA). The silicon heteroatom-inducing flower-withering like morphology for SPUs was found with increasing silicon groups, which revealed an evolution from flowers-blossoming to broken petals like microdomain due to the ordered aggregation of hard segments. In addition, the reversible thermo-optic response of SPUs, a sharp transition from light opaque at room temperature to more than 55% transmission at 160 °C, was observed, attributing to “sea-island” or bi-continuous structural evolution owing to hydrogen bond dissociation or recombination with changing the temperature. Comparing with pure PU, the enhanced mechanical properties of SPUs were achieved, more than 20 times tensile strength (14.75 ± 2.52 MPa) and more than 3 times elongation at break (293.31 ± 2.87%). In sum, the study was of great significance for designing novel functional segmented PU materials.

Preparation of porous metakaolin-based geopolymer foam as an efficient adsorbent for dye removal from aqueous solution

Dye removal from aqueous solutions as one of the dangerous and non-degradable pollutants is one of the critical environmental issues discussed today. In this research, metakaolin-based geopolymer foam adsorbent was fabricated using a templating emulsion/chemical foaming method, characterized, and utilized to remove methylene blue dye from an aqueous solution. Dye adsorption studies were performed using batch experiments and operational parameters such as contact time, initial pH solution, temperature, initial dye concentration, adsorbent dose, and pHPZC the adsorbent investigated. The various kinetic models (pseudo-first-order, pseudo-second-order, and intraparticle diffusion) and isotherms (Langmuir, Freundlich, and Temkin) were used to analyze the experiment results. The fabricated adsorbent surface includes the bulk porous structure consisting of novel flower-like hierarchical microstructures made up of dozens of nanorods building block units. The adsorption results were fitted to the pseudo-second-order kinetic with an equilibrium time of 120 min and Freundlich isotherm models. The highest methylene blue adsorption was obtained up to 90 %. Maximum adsorption capacity was obtained at 12.5 mg/g for 10 mg/L dye solution in 40 °C and pH = 13. According to the thermodynamic investigation, the methylene blue adsorption on the geopolymer foam adsorbent was performed as spontaneous and endothermic due to the negative value of the ΔG° and positive value of ΔH°. The prepared adsorbent could remove different cationic and anionic dyes from aqueous solutions but exhibited the highest adsorption efficiency towards cationic dyes. The prepared geopolymer exhibited good adsorption performance as a promising adsorbent for dye wastewater.

Flower-like ZnCo2O4 microstructures with large specific surface area serve as battery-type cathode for high-performance supercapacitors

In this work, flower-like ZnCo2O4 microstructures were synthesized through an initial solvothermal method and combined with an extra calcination treatment. The mixed solvent containing glycerol and isopropyl alcohol in different volume ratio played an important role for the formation of MFs with different size, namely the ZnCo2O4 MFs-20/20 and ZnCo2O4 MFs-5/35. These ZnCo2O4 MFs were assembled by many porous nanosheets with thin thickness and exhibited huge specific surface area. Benefitting from this significant feature, these MFs presented outstanding electrochemical properties. Under the current load of 1 A g−1, the ZnCo2O4 MFs-20/20 delivered a specific capacity of up to 373.2C g−1, which was superior to that (315.6C g−1) of ZnCo2O4 MFs-5/35. At the same time, they also demonstrated a good rate performance with 72.4 % and 76.9 % capacity retention under 10 A g−1, respectively. To evaluate the practical application of these MFs in supercapacitor, a hybrid supercapacitor (HSC) was assembled using such ZnCo2O4 MFs as cathode and activated carbon (AC) as anode. The ZnCo2O4 MFs-20/20//AC HSC delivered a high energy density of up to 44.9 W h kg−1 at 1077.7 W kg−1, and the ZnCo2O4 MFs-5/35//AC HSC exhibited an inferior energy density of 37.2 W h kg−1. Both HSCs presented superior cycling property over 5000 cycles at a high current load of 8 A g−1. These electrochemical results suggest that the ZnCo2O4 MFs in this work can serve as advanced cathode for the assembly of high-performance hybrid supercapacitor, and may have brilliant commercial prospect in the field of electrochemical energy storage.

BiOI/Bi2MoO6 p-n Junction to Enhance Visible Light Photocatalytic Activity toward Environmental Remediation.

Photocatalytic degradation of organic pollutants via semiconductors with high visible light response and effective carrier separation is an economical and green route to greatly achieve environmental remediation. Herein, an efficient BiOI/Bi2MoO6 p-n heterojunction was in situ fabricated through hydrothermal method by substituting Mo7O246- species for I ions. The characteristic p-n heterojunction exhibited a strongly enhanced visible light responsive absorption from 500 to 700 nm owing to the narrow band gap of BiOI and a greatly effective separation of photoexcited carriers because of the built-in electric field on the interface between BiOI and Bi2MoO6. Moreover, the flower-like microstructure also promoted the adsorption of organic pollutants owing to the large surface area (about 10.36 m2/g), good for further photocatalytic degradation. As a result, BiOI/Bi2MoO6 p-n heterojunction showed an excellent photocatalytic activity of RhB of almost 95% in a short time of 90 min under wavelength longer than 420 nm, 2.3 and 2.7 times higher compared with single BiOI and Bi2MoO6, respectively. This work offers a promising approach to purify the environment through the utilization of solar energy by constructing efficient p-n junction photocatalysts.

Constructing flower-like TiO2/Bi2O3 p-n heterojunction with enhanced visible-light photocatalytic performance

Coupling morphology modification with heterojunction is an effective strategy to promote the photocatalytic activity of TiO2-based photocatalysts for wastewater treatment. In this work, we devise a novel flower-like TiO2/Bi2O3 (FTB) photocatalyst through the deposition of Bi2O3 nanoparticles on the surface of flower-like TiO2 (FT). Various characterization techniques reveal the successful construction of p-n heterojunction at the interfaces of flower-like TiO2 and Bi2O3, which promotes efficient charge separation. Benefiting from the narrow bandgap of Bi2O3 and flower-like microstructure, the photocurrent of FTB is about 1.67 times higher than that of FT, leading to higher photo-degradation rate (92.7%) of levofloxacin than that (∼80%) of FT photocatalyst. More important, FTB presents a good anti-interference capability for environmental factors including solution pH, ionic strength, and water matrix. Additionally, the photocatalytic performance and microstructure of FTB photocatalyst remain unchanged before and after five cycles, suggesting a good cyclability. Therefore, this work offers a new insight in constructing TiO2-based photocatalysts with advanced performance for efficient removal of antibiotics.

Dual role of flower-like Fe3O4/Ag microstructure in electrocatalytic detection and catalytic reduction of 4-nitrophenol

In this work, a novel Ag-incorporated 3D flower-like porous Fe3O4 magnetic microstructure (Fe3O4/Ag-FM) was effectively prepared via a quasi-reverse emulsion soft template approach and reductive deposition of Ag nanoparticles. The synthesized Fe3O4/Ag-FM material was applied for the electrochemical sensing and catalytic reduction of 4-nitrophenol (4-NP). Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques were used to determine the electrochemical sensing ability of the synthesized material. Results showed that the fabricated Fe3O4/Ag-FM-based electrode detected a low concentration of 4-NP (0.093 μM) and a linear response in the range of 1.0–15 μM. Furthermore, the Fe3O4/Ag-FM material also exhibited excellent reduction ability towards 4-NP with the assistance of NaBH4. This is because a synergistic effect formed between Ag nanoparticles and flower-like Fe3O4 magnetic microstructure enhanced the catalytic activity towards electrochemical detection and reduction of 4-NP. Overall, the current strategy could help design and synthesize future catalysts that can work as sensors and catalysts.

Open 3D structure of Ni2−xSnxP/C microflowers electrodes assisted by ion-exchange in metal-organic skeleton for battery-supercapacitor hybrids

Transition metal phosphides are promising electrode materials for battery-type supercapacitors. Herein, the Ni2−xSnxP/C microflowers electrode materials are synthesized through ion-exchange of metal-organic frameworks and subsequent calcination processes. The introduction of Sn species significantly alters the microstructure of Ni2−xSnx-MOF and Ni2−xSnxP/C. The optimum Ni1.6Sn0.4P/C exhibits 3D (3-dimensional) open flower-like microstructures, which are composed of large quantities of nanorods. As battery-supercapacitor hybrid electrode materials, the as-prepared Ni1.6Sn0.4P/C exhibits an excellent specific capacity of 839.6 C g−1 at the current density of 1 A g−1 and superior capacity retention in a three-electrode system. Moreover, the assembled Ni1.6Sn0.4P/C//AC asymmetric supercapacitor demonstrates a high energy density of 59.3 Wh kg−1 at the power density of 750 W kg−1, and good cycling stability with 92% capacity retention after 5000 cycles at current densities of 10 A g−1. Therefore, the Ni1.6Sn0.4P/C with flower-like microstructures are expected to be an ideal battery-type electrode material for high-performance energy storage devices in the future.

One-step construction of α-MnMoO4 microstructures with enhanced lithium storage properties

Due to the synergistic effects of multiple transitional metals, high theoretical specific capacity and good electrical conductivity, α-MnMoO4 exhibits superior performance and can be utilized as one prospective lithium-ion battery anode material. Herein, a new solvothermal reduction method was adopted for the synthesis and construction of α-MnMoO4 microstructures. Both dart-like and nanosheet-based flower-like α-MnMoO4 microstructures can be prepared by tuning the initial amount of molybdenum acetylacetone during the reaction process. The electrochemical measurements show that the dart-like α-MnMoO4 microstructures and nanosheet-based flower-like α-MnMoO4 microstructures deliver the stable specific capacities of 951.4 and 861.4 mA h g−1 at a current density of 0.5 A g−1 after 400 cycles. The excellent capacity, stable and sustainable cyclic performance are much superior to the reported α-MnMoO4 particles. The improved electrochemical performance proves that α-MnMoO4 microstructures can be served as one prospective anode of lithium-ion batteries.

Synthesis of 3D flowerlike S-scheme Bi4O5I2/BiOI heterojunction with synergistic effect of adsorption and photocatalysis

Three-dimensional (3D) flowerlike Bi4O5I2/BiOI heterojunction composed of ultrathin nanosheets with a thickness of 13 nm was prepared in urea aqueous solution (pH 5–6). Whereas, if urea was not added, pure BiOI was obtained at same pH range and Bi4O5I2/BiOI nanosheets (∼20 nm) could be synthesized at a pH value high to 11. Bi4O5I2/BiOI-urea exhibited superior photodegradation activity for bisphenol A (BPA, 95 %) within 120 min of visible-light illumination, which was better than Bi4O5I2/BiOI-H2O (70 %) and BiOI (40 %). And Bi4O5I2/BiOI-urea also presented excellent adsorption performance for MG with a maximum adsorption capacity of 138 mg g−1. The improved photocatalytic and adsorption performance could be ascribed to 3D flower-like hierarchical microstructures and high specific surface area due to the coordination effect of urea.