Flower-like Architectures Research Articles

XPS investigation of MnO2 deposits functionalized with graphitic carbon nitride

Composite materials based on MnO2 deposits functionalized with graphitic carbon nitride (gCN) nanostructures are promising (photo)electrocatalysts for oxygen evolution reaction (OER). Besides the individual properties of the two electrode components, mutual interactions at their interface can also exert a significant influence on functional performances. In this work, MnO2 deposits are synthesized by plasma enhanced-chemical vapor deposition on Ni foam supports and subsequently decorated with two different forms of carbon nitride via electrophoretic deposition. Structural and morphological analyses revealed the formation of β-MnO2 2D structures hierarchically assembled into flowerlike architectures, whose surface appeared decorated by 3D particles built up from gCN nanoflakes. Based on the intimate contact between the two semiconductors, an effective electronic and chemical coupling was established at their interface. In the following, we report on a comparative XPS characterization of a bare MnO2 electrode material and of two MnO2-gCN composite systems prepared from different carbon nitride powders. Survey spectra as well as detailed scans for C 1s, N 1s, O 1s, and Mn 2p regions are presented and critically discussed.

Fabrication of Porous Ni-Co LDH Nanocomposites as Efficient Electrodes for Supercapacitors

Nowadays, there is constant demand for the development of energy storage materials using advanced methodologies. In this scenario, a large-scale environmentally friendly synthesis was chosen to prepare Ni-Co-layered double hydroxide (LDH) composites for asymmetric supercapacitors. The developed materials had a flower-like porous architecture with very low dimensional layers and a large surface area. The developed Ni-Co/LDH composite electrodes showed impressive specific capacitance of 1095.1 F/g at a current density of 1 A/g and maintained 492.5 F/g even at a current density of 20 A/g. In particular, the Ni-Co/LDH composites maintained 86.9% of their initial capacitance even after 5000 cycles at a high current density of 2 A/g. Furthermore, an asymmetric supercapacitor with Ni-Co/LDH composites demonstrated an excellent energy density of 40.7 Wh/kg at a power density of 750 W/kg.

Morphology-steered synthesis of Ce-MnO2 catalysts for catalytic oxidation of ethane at low temperature

Ce-MnO2 catalysts with nanosheets-stacked flower-like architecture were prepared by hydrothermal method, and Ce0.5Mn1 sample exhibited excellent catalytic performance for ethane combustion, with T90 at 310 °C. The apparent activation energy of the Ce0.5Mn1 sample (70.7 kJ mol−1) was comparatively lower than that of pure MnO2 (112.4 kJ mol−1). The formation of CeMn solid solution reduced the sizes of the Ce-MnO2 crystallites, affording higher SBET. Electron transfer and redistribution in the CeMn solid solution enhanced the activation of surface oxygen (OA) and generated more oxygen vacancies. The increasing OA species and highly mobile lattice oxygen boosted the oxidation of ethane. Also, the Ce0.5Mn1 catalyst exhibited enhanced H2O resistance with an ethane conversion over 95 % at 350 °C. Moreover, the morphologies of the CexMn1 catalysts were significantly influenced by Ce doping. Variations in Ce3+ amount significantly altered the thickness of the nanosheets, and the structure displayed more surface defects with considerable active sites. This work provides insights into the design of a promising MnO2-based catalyst for the mitigation of light alkanes.

Cu-doped flower-like SnO2 architecture toward promoting SO2 detection: Fast equilibrium and low trace monitoring

Design of practical tin oxide (SnO2) semiconductor gas sensors is fundamental strategy to detect hazardous gases such as SO2. However, challenges remain in the detection of SO2 gas at low concentration and slow equilibrium between gas adsorption and desorption. Herein, the superior performance of nanostructured of Cu-doped flower-like SnO2 architecture via feasible hydrothermal method demonstrated for the detection of SO2 gas at low concentration (1–20 ppm) and fast gas adsorption and desorption equilibrium (14 s) towards 5 ppm SO2. Furthermore, the as fabricated 3 mol% Cu-doped SnO2 shows an outstanding gas response (∼ 4.05–20 ppm SO2) at the working temperature of 300 ℃. The Cu-doping strategy may pave the way to ultrasensitive SO2 gas sensor possessing low trace monitoring and fast equilibrium ability to satisfy the increasing demand for toxic SO2 gas detection.

Construction of a BiOI/ZnO heterojunction on biomass Juncus effusus fiber for photodegradation of organic pollutants

Semiconductor heterojunction engineering and three-dimensional (3D) architecture construction have been considered highly desirable strategies to enhance photocatalytic performance. Herein, a BiOI/ZnO composite photocatalyst with a 3D flower-like architecture was successfully prepared, which was stably immobilized on three-dimensional porous lignocellulosic biomass Juncus effusus (JE) fiber. The outstanding photocatalytic performance of the BiOI/ZnO-JE fiber was confirmed by the degradation of tetracycline hydrochloride (TC, 90%), ciprofloxacin (CIP, 79%), and norfloxacin (NOR, 81%). The enhanced photocatalytic activities were mainly attributed to the synergistic absorption performance of the lignocellulosic JE and the effective transfer and separation of charges. Moreover, the hydroxyl (·OH) and superoxide radicals (·O2−) are the main reactive species in the photocatalytic process according to the analysis. This work may provide a novel perspective for constructing high-performance lignocellulosic-based photocatalytic materials.

Facile preparation and high microwave absorption of flower-like carbon nanosheet aggregations embedded with ultrafine Mo2C

Rational regulation of microstructure and components is vital for excellent microwave absorption performance. In this study, we report flower-like carbon nanosheet architectures embedded with ultrafine Mo2C as a microwave absorber, prepared via simple carbothermal reduction using Mo-polydopamine as the precursor. We found that the particle size of the obtained Mo2C/C composites could be simply tailored by the added ammonium molybdate content in the initial solution for the preparation of the Mo-polydopamine precursor. This helped tailor the BET surface area, which significantly impacts microwave absorption performance. The sample with a BET surface area of 173.31 m2g−1 displayed high-efficiency microwave absorption, and the effective absorbing band reached up to 7.04 GHz (10.96–18 GHz) with the matching thickness of 2.9 mm at relatively low filler loading (only 10 wt%). Thus, the excellent microwave absorption performance and simple preparation process of the flower-like Mo2C@C composites are promising for applications requiring lightweight and broadband microwave absorption.

Fabrication of multi-scale CdS/ZnO heteroarchitectures with boosted dual photocatalytic activities for hydrogen generation and organic dye degradation under solar light

Binary multi-scale CdS/ZnO heterogeneous architectures comprised of zero-dimensional (0D) CdS nanoparticles depositing onto 3D flower-like architectures self-aggregated by 2D ZnO nanoflakes have been successfully fabricated by a facile aqueous chemical process. The H2-generation rate of the optimized CZ-3 is calculated to be 15.682 mmol g−1 h−1 under simulated solar irradiation, which is 15.25, 101.17 and 39.70 times higher than that of pristine ZnO, bare CdS, and the physical mixture, respectively. The photocatalytic oxidation kinetics rate constant over the optimal CZ-3 in degradation of Congo red is measured to be 0.05686 min−1 under simulated sunlight, which reaches 7.21, 9.07, 5.82 folds higher than that of pristine ZnO, pure CdS, and the physical mixture, respectively. The dual boosted photocatalytic performance of CdS/ZnO composite is assigned to the synergetic multi-scale heteroarchitecture with the interfacial heterojunction. The photocatalytic electron transfer mechanism is proposed based on the perfect band matching and the free radical experiments.

Tailoring NH4+ storage by regulating oxygen defect in ammonium vanadate

Defect engineering is an effective strategy for modifying the energy storage materials to improve their electrochemical performance. However, the impact of oxygen defect and its content on the electrochemical performances in the burgeoning aqueous NH4+ storage field remains explored. Therefore, for the first time in this work, an oxygen-defective ammonium vanadate [(NH4)2V10O25·8H2O, denoted as Od-NHVO] with a novel 3D porous flower-like architecture was achieved via the reduction of thiourea in a mild reaction condition, which is a facile method that can realize the intention to regulate the oxygen defect content, with the capability of mass-production. The as-prepared OdM-NHVO with moderate oxygen defect content can deliver a stable specific capacitance output (505 F g−1, 252 mAh g−1 at 0.5 A g−1 with ∼80% capacitance retention after 10,000 cycles), which benefits from extra active sites, unimpeded NH4+-migration path and relatively high structure integrity. In contrast, low oxygen defect content will lead to the torpid electrochemical reaction kinetics while too high content of it will reduce the charge-storage capability and induce structural disintegration. The superior NH4+-storage behavior is achieved with the reversible intercalation/de-intercalation process of NH4+ accompanied by forming/breaking of hydrogen bond. As expected, the assembled flexible OdM-NHVO//PTCDI quasi-solid-state hybrid supercapacitor (FQSS HSC) also exhibits high areal capacitance, energy density and reliable flexibility. This work provides a new avenue for developing materials with oxygen-deficient structure for application in various aqueous non-metal cation storage systems.

A MOF-derived porous In2O3 flower-like hierarchical architecture sensor: near room-temperature preparation and fast trimethylamine sensing performance

A MOF-derived porous In2O3 flower-like hierarchical architecture sensor is prepared at near room temperature, which exhibits a high response and a fast response speed towards trimethylamine.

One-pot synthesis of flower-like Ni-Co/reduced graphene oxide layered double hydroxide nanocomposites as advanced electrodes for high-performance asymmetric supercapacitors

Novel electrode materials with appropriate architectures are always desired to increase the energy density of supercapacitors. Here, the design and fabrication of NiCo-layered double hydroxides (NC-LDH) in composition with reduced graphene oxide (rGO) were prepared as high-performance electrodes for supercapacitors. In particular, a facile and one-pot scheme was designed for the growth of NC/rGO-LDH composites, which exhibited a high specific surface area of 204 m2/g. The compositional features of the composites, i.e., a two-dimensional flower-like layered architecture and conductive rGO, contributed to their highly impressive specific capacitance (1913.5 F/g at 1 A/g) and excellent cyclic performance. Furthermore, an asymmetric supercapacitor was designed using NC/rGO-LDH composites as the positive electrode and activated carbon as the negative electrode, which displayed a high energy density of 59.2 Wh/kg at a power density of 750 W/kg.

Novel FeVO4/CuS heterojunction nanocomposite as a high-performance visible-light-active photocatalyst for ibuprofen degradation in aquatic media

Herein, we report the fabrication of type-II FeVO4/CuS heterojunction nanocomposite by a versatile reflux-assisted co-precipitation procedure. The hybrid FeVO4/CuS heterostructure with a band gap of 1.95 eV, demonstrated excellent degradation efficiency of ibuprofen antibiotic (∼95%) after 90 min of visible-light irradiation, which displayed remarkably enhanced photocatalytic degradation (1.75 fold higher) in comparison to pristine FeVO4 structure. The superior photocatalytic performance of the FeVO4/CuS nanocomposite is associated with hierarchical flower-like architectures, great visible-light harvesting, and poor electron-hole recombination due to the fabrication of type-II heterojunction. In addition, we introduced an obvious photocatalytic destruction mechanism, which indicated that superoxides (•O2−) and holes (h+) were the invasive species in antibiotic degradation on the FeVO4/CuS photocatalyst. Consequently, the as-prepared FeVO4/CuS heterojunction photocatalyst is a promising candidate for the development of future photocatalysts towards the elimination of antibiotics under sun light irradiation at short process time.

One-step construction of Ni2S-coated graphene nanosheets with flower-like architecture as binder-free electrode for efficient supercapacitor applications

Assembly of Ni2S-coated rGO flower-like hierarchical microstructure on Ni foam (Ni2S@rGO/Ni foam) was fabricated by simply heating Ni foam in the alkaline solution containing GO, thiosulfate and TG at 60 °C. Two novel reactions are involved in the fabrication of Ni2S@rGO/Ni foam. One is the redox reaction between Ni foam and graphene oxide (GO). During the reaction, GO was reduced to reduced graphene oxide (rGO) while elemental nickel was oxidized to Ni cation. Another is the hydrolysis of thiosulfate in alkaline solution catalyzed by 1-thioglycerol (TG). The product of the hydrolysis reaction is S2−, which may react with transition metal cations to form transition metal sulfide (TMS). Ni2S@rGO/Ni foam exhibits high capacitance (3.92 F cm−2 at 10 mA cm−2) and long cycling life (55.5 % retention after 5000 charge/discharge cycles). The excellent energy storage performances of the supercapacitor device with Ni2S@rGO/Ni foam and activated carbon (AC) as positive and negative electrodes exhibit the great application potential of Ni2S@rGO/Ni foam.

Well-assembled nanosheets of nickel-cobalt double hydroxide flower as a reversible faradic battery-type electrode material for high-performance hybrid supercapacitor

The design and advancement of the interconnected three-dimensional (3D) porous nanoarchitecture electrode materials with fascinating electrochemical performance are in high demand for high-performance hybrid supercapacitors (HSCs). Herein, we report a facile fabrication of 3D flower-like nickel-cobalt double hydroxides (NiCoDH) architecture via a template-free hydrothermal approach. The NiCoDH flower-like architecture is composed of self-assembling and interconnecting many thin nanosheets with thicknesses ranging from 11–16 nm. The open void space and vertically oriented nanosheets in the NiCoDH flower-like architecture could shorten the pathway for the charge and electrons transport and offer abundant electroactive sites for redox reactions to enhance the electrochemical performance of the electrode material. The flower-like NiCoDH electrode material reveals a high specific capacity (Qs) of 731 C g−1 at the current of 1 A g−1 and retains 461 C g−1 even at 20 A g−1, signifying the high rate capability of the obtained electrode material. The HSC is constructed by adopting the NiCoDH and activated carbon (AC) as the positrode and negatrode, respectively. Further, the HSC supplies a Qs of 352 C g−1, and it offers a high energy density of 58.30 Wh kg−1 at the power density of 21.09 kW kg−1 and an excellent long-term cyclic life (∼90.4% retention over 10,000 repeated GCD cycles).

Surfactant-assisted self-assembly of flower-like ultrathin vanadium disulfide nanosheets for enhanced hybrid capacitive deionization

Increasing the salt adsorption capacity (SAC) and durability of electrode materials for hybrid capacitive deionization (HCDI) remain grand challenges. Herein, highly electro-adsorptive and durable vanadium disulfide (VS2) electrode material obtained by a surfactant-assisted hydrothermal method is reported. The distinct three-dimensional flower-like architecture and ultrathin thickness of VS2 nanosheets play a vital role in boosting HCDI performance by exposing a large number of accessible adsorption sites and facilitating the mass transfer of sodium ions. When used in the HCDI system, the flower-like VS2 electrode delivers a high salt adsorption capacity of 72 mg g−1 in 500 mg L−1 NaCl solution at 1.6 V, outperforming the bulk VS2 counterpart with a relatively increased thickness of nanosheets. Moreover, after 10 h of cycling test, the SAC of the flower-like VS2-based HCDI system remains at 93 % of the initial value, showing excellent operation stability. This surfactant-assisted morphology engineering of VS2 nanosheets with ultrathin thickness and unique three-dimensional architecture provides new insight into designing layered electrode materials for efficient HCDI.

Efficient Removal of Methylene Blue and Ciprofloxacin from Aqueous Solution Using Flower-like, Nanostructured ZnO Coating under UV Irradiation.

Flower-like ZnO architectures assembled with many nanorods were successfully synthesized through Thermionic Vacuum Arc, operated both in direct current (DC-TVA) and a pulsed mode (PTVA), and coupled with annealing in an oxygen atmosphere. The prepared coatings were analysed by scanning-electron microscopy with energy-dispersive X-ray-spectroscopy (SEM-EDX), X-ray-diffraction (XRD), and photoluminescence (PL) measurements. By simply modifying the TVA operation mode, the morphology and uniformity of ZnO nanorods can be tuned. The photocatalytic performance of synthesized nanostructured ZnO coatings was measured by the degradation of methylene-blue (MB) dye and ciprofloxacin (Cipro) antibiotic. The ZnO (PTVA) showed enhancing results regarding the photodegradation of target contaminants. About 96% of MB molecules were removed within 60 min of UV irradiation, with a rate constant of 0.058 min−1, which is almost nine times higher than the value of ZnO (DC-TVA). As well, ZnO (PTVA) presented superior photocatalytic activity towards the decomposition of Cipro, after 240 min of irradiation, yielding 96% degradation efficiency. Moreover, the agar-well diffusion assay performance against both Gram-positive and Gram-negative bacteria confirms the degradation of antibiotic molecules by the UV/ZnO (PTVA) approach, without the formation of secondary hazardous products during the photocatalysis process. Repeated cyclic usage of coatings revealed excellent reusability and operational stability.

Insight into the Growth Mechanism of Mixed Phase CZTS and the Photocatalytic Performance.

In this work, CZTS particles with a mixed phase of wurtzite and kesterite were synthesized by the solvothermal method. The time-dependent XRD patterns, Raman spectra, SEM, and EDS analysis were employed to study the growth mechanism of CZTS. The results revealed that the formation of CZTS started from the nucleation of monoclinic Cu7S4 seeds, followed by the successive incorporation of Zn2+ and Sn4+ ions. Additionally, the diffusion of Zn2+ into Cu7S4 crystal lattice is much faster than that of Sn4+. With increasing time, CZTS undergoes a phase transformation from metastable wurtzite to steady kesterite. The morphology of CZTS tends to change from spherical-like to flower-like architecture. The mixed-phase CZTS with a bandgap of 1.5 eV exhibited strong visible light absorption, good capability for photoelectric conversion, and suitable band alignment, which makes it capable to produce H2 production and degrade RhB under simulated solar illumination.

A comparative study on the acetone sensing properties of ZnO disk pairs, flowers, and walnuts prepared by hydrothermal method

The synthesis of sensing materials in suitable morphology and microstructure is critical for fabricating fast, highly responsive, and reliable acetone sensing devices for human safety and health. Herein, ZnO disk pairs, flower-like, and walnut-like hierarchical architectures were prepared by varying the relative amount of citric acid and NaOH to Zinc acetate dihydrate during the hydrothermal process. At the lowest prime working temperature, the ZnO flowers exhibited the highest gas response, stability, and selectivity towards acetone due to the highest degree of (001) facet exposure and Schottky barrier height, the largest BET specific surface area and BJH average pore size. At the same temperature, the ZnO walnuts displayed the shortest response/recovery time and the lowest limit of detection due to the highest content of surface oxygen vacancy and the high reactivity of adsorbed O2– ions; the ZnO disk pairs showed unique selectivity towards ethylene glycol monomethyl ether due to the highest degree of (100) facet exposure and the smallest BJH average pore size. Replacing Zinc acetate dehydrate by Zinc nitrate hexahydrate improved the acetone sensing performance of the ZnO flowers in terms of response value, stability, and selectivity at the expense of a higher LOD and a slower recovery speed.

Synthesis of carnation flower-like Bi2O2CO3 photocatalyst and its promising application for photoreduction of Cr(VI)

In this study, we have synthesized high-quality carnation flower-like Bi2O2CO3 hierarchical architectures via a hydrothermal route. The as-synthesized Bi2O2CO3 photocatalyst was systematically characterized and analyzed by various techniques. Its photocatalytic activity was investigated by simulated-sunlight driving photoreduction of Cr(VI), revealing that it exhibits excellent photocatalytic removal of Cr(VI). The effects of various factors (H2SO4, NaOH, Cr(VI) concentration, catalyst dosage) on the photoreduction efficiency and involved mechanism were systematically investigated and discussed. In addition, we have also systematically examined the effects of various parameters (H2SO4 concentration, 1,5-diphenylcarbazide (DPC) concentration, Cr(VI) concentration, reaction time t and reaction temperature T) on the absorbance of the Cr(VI) solution, with the aim of correctly determining the Cr(VI) concentration according to UV–vis absorption measurements using DPC as the chromogenic agent.

Simulation of reconfigurable double-input optical gates based on a microring flower-like structure, part II. Combinational logic gates.

A microring flower-like architecture is introduced to obtain optical logic gates that can be reconfigured. The proposed design can operate as a time-division multiplexer, a half adder/subtractor, and an optical single bit comparator circuit. The optical pump pulses modulate the microring resonators in this arrangement. Green lasers with a resonant wavelength of 532 nm are used to generate the optical pump pulses. To theoretically analyze the structure, the signal flow graph approach is applied. The proposed structure's performance is investigated by calculating certain figures of merit for the resulting output data streams. Outputs of the presented combinational logic gates are optimized by designing the most proper geometry of flower-like structure and simultaneously by opting for the best input port to drop port's optical path. It is demonstrated that proper distinguishing between 0 and 1 levels occurs in the output. The compact structure proposed is simple, expandable, and reconfigurable. The proposed structure can be used as a key component in high-speed optical networks, according to simulation results.

Hollow flower-like Cr2V4O13 hierarchical micro-nano architectures: Controlled self-assembly synthesis and the outstanding catalytic performances for ammoxidation of chlorotoluenes

The controlled synthesis of hierarchical micro-nano materials has attracted great interest due to their wide applications in catalysis and many other fields. In this paper, hollow flower-like Cr2V4O13 hierarchical micro-nano structures were successfully synthesized via a facile hydrothermal process and subsequent calcination treatment. The samples were characterized by XRD, TGA, FT-IR, SEM, TEM, XPS, TPR and N2 adsorption-desorption. SEM and TEM micrographs showed that the as-obtained Cr2V4O13 had a three-dimensional (3-D) hollow flower-like superstructure assembled by numerous nanoflakes with widths of 0.2 µm and thickness of about 30 nm. The micro-nano structured Cr2V4O13 exhibited high activity and selectivity in continuous ammoxidation of chlorotoluenes to the corresponding chlorobenzonitriles. To the best of our knowledge, this is the highest activity reported for selective ammoxidation of chlorotoluenes with Cr-V-O binary catalysts. The unique catalytic behavior of Cr2V4O13 was ascribed to the micro-nano hierarchical architecture and the increased active surface sites.