Dandelion-like Morphology Research Articles

Dandelion-like ZIF-67 supported ternary transition metal borides as efficient hydrolysis catalysts for KBH4

The development of high-efficient and low-cost catalysts is crucial for promoting KBH4 hydrolysis to produce hydrogen. Herein, ZIF-67 supported cobalt-molybdenum-nickel based boride (Co–Mo–Ni–B/ZIF-67) nanocomposites with dandelion-like morphology were designed as catalysts of KBH4 hydrolysis reaction and were synthesized via the chemical reduction process. Moreover, the element ratio and the loading amount of Co–Mo–Ni–B were optimized, and effects of KBH4 concentration, KOH concentration, and reaction temperature on catalytic performances were studied. As expected, ZIF-67 substrate avoids the agglomeration of amorphous Co–Mo–Ni–B, and the synergy between ZIF-67 and uniformly dispersed Co–Mo–Ni–B active substances accelerates hydrogen generation rate. As a result, the maximum hydrogen generation rate of 17400 mL min−1 g−1 is achieved with the optimized KOH concentration of 10% and KBH4 concentration of 6% at the reaction temperature of 30 °C. In addition, Co–Mo–Ni–B/ZIF-67 exhibits moderate durability performance with a cyclic retention rate of 51.9 % after five cycles. This dandelion-like structure design provides an idea for the development of efficient catalyst for hydrolysis of borohydrides.

PEG-Coated MnZn Ferrite Nanoparticles with Hierarchical Structure as MRI Contrast Agent.

In this work, MnZn ferrite nanoparticles with hierarchical morphology were synthesized hydrothermally, and their surface characteristics were improved by the PEGylation process. In vitro MRI studies were also conducted to evaluate the ability of the synthesized nanoparticles as a contrast agent. All results were compared with those obtained for MnZn ferrite nanoparticles with normal structure. Microstructural evaluations showed that in ferrite with hierarchical morphology, the spherical particles with an average size of ~20 nm made a distinctive structure consisting of rows of nanoparticles which is a relatively big assembly like a dandelion. The smaller particle size and dandelion-like morphology led to an increase in specific surface area for the hierarchical structure (~69 m2/g) in comparison to the normal one (~30 m2/g) with an average particle size of ~40 nm. In vitro MRI, cytotoxicity and hemocompatibility assays confirmed the PEG-coated MnZn ferrite nanoparticles with hierarchical structure synthesized in the current study can be considered as an MRI contrast agent.

Synthesis of highly regular dandelion-like hydroxyapatite particles—a Taguchi experimental design approach

This study provides a method for the synthesis of hydroxyapatite having a highly regular dandelion-like morphology with high degree of phase purity.

MnO2 modified perovskite oxide SrCo0.875Nb0.125O3 as supercapacitor electrode material

Cobalt-based perovskite SrCo0.875Nb0.125O3 is an advantageous electrode material for supercapacitors. However, the particle form of SrCo0.875Nb0.125O3 is not conducive to the electrochemical behavior. Based on this, surface MnO2 modified SrCo0.875Nb0.125O3 on carbon cloth (MnO2@SrCo0.875Nb0.125O3@CC) has been prepared as supercapacitor electrode. The dandelion-like morphology of MnO2 significantly increases the specific surface area and inhibits the grain agglomeration of SrCo0.875Nb0.125O3, thus promoting the ion diffusion during the electrochemical process. As a result, the electrochemical performance of the composite is significantly optimized due to the synergistic effect of SrCo0.875Nb0.125O3 and MnO2. The MnO2@SrCo0.875Nb0.125O3@CC electrode yields an ultra-high specific capacitance of 2066.0 mF cm−2 at 2 mA cm−2 current density. Compared with SrCo0.875Nb0.125O3@CC electrode and MnO2@CC electrode, this work provides a much improved performance. Besides, an asymmetric supercapacitor composed of MnO2@ SrCo0.875Nb0.125O3@CC as positive electrode and CuS@CC as negative electrode exhibits a voltage window of 1.8 V and a specific capacitance of 114.6 mF cm−2 when the current density is 3 mA cm−2. A high energy density of 51.57 μ Wh cm−2 is achieved at a power density of 4.86 mW cm−2 for the device.

Bioinspired dandelion-like silica nanoparticles modified with L-glutathione for highly efficient enrichment of N-glycopeptides in biological samples

The pretreatment of complicated biological samples to eliminate the interference of nonglycopeptides and improve the efficiency of glycopeptides detection is crucial in glycoproteomics research. Hydrophilic interaction chromatography (HILIC) has been adopted for enrichment of glycosylated peptides following identification with mass spectrometry, but it is still urgent to develop novel hydrophilic materials to save cost and improve enrichment efficiency. Scientists are pursuing to fabricate freestanding intelligent artificial materials. One promising approach is to use biomimic material. In our case, “one-pot” strategy was developed to prepare bioinspired nano-core-shell silica microspheres (CSSMs), employing tetrapropylorthosilicate as the silicon source and phenolic resin as the soft template. The pore structure of the obtained microspheres diverged from the center to the outside with diameter ranged from 150 to 340 nm, and shell layer ranged from 25 to 83 nm by adjusting the preparation parameters. Some of them showed dandelion-like morphology. After hydrophilic modification, these CSSMs exhibited great hydrophilicity and could be used as sorbents for enriching N-glycopeptides from complicated biological samples in HILIC. Up to 594 unique N-glycopeptides and 367 N-glycosylation sites from 182 N-glycoproteins were unambiguously identified from 2 μL of human serum, which was superior to the enrichment performance of many HILIC materials in reported papers, demonstrating great potential advantages in proteomic application.

Hybrid Transition Metal Dichalcogenide/Graphene Microspheres for Hydrogen Evolution Reaction.

A peculiar 3D graphene-based architecture, i.e., partial reduced-Graphene Oxide Aerogel Microspheres (prGOAM), having a dandelion-like morphology with divergent microchannels to implement innovative electrocatalysts for the hydrogen evolution reaction (HER) is investigated in this paper. prGOAM was used as a scaffold to incorporate exfoliated transition metals dichalcogenide (TMDC) nanosheets, and the final hybrid materials have been tested for HER and photo-enhanced HER. The aim was to create a hybrid material where electronic contacts among the two pristine materials are established in a 3D architecture, which might increase the final HER activity while maintaining accessible the TMDC catalytic sites. The adopted bottom-up approach, based on combining electrospraying with freeze-casting techniques, successfully provides a route to prepare TMDC/prGOAM hybrid systems where the dandelion-like morphology is retained. Interestingly, the microspherical morphology is also maintained in the tested electrode and after the electrocatalytic experiments, as demonstrated by scanning electron microscopy images. Comparing the HER activity of the TMDC/prGOAM hybrid systems with that of TMDC/partially reduced-Graphene Oxide (prGO) and TMDC/Vulcan was evidenced in the role of the divergent microchannels present in the 3D architecture. HER photoelectron catalytic (PEC) tests have been carried out and demonstrated an interesting increase in HER performance.

Novel ultra-sensitive dandelion-like Bi2WO6 nanostructures for ethylene glycol sensing application

The novel dandelion-like Bi2WO6 nanostructures with layered perovskites were successfully fabricated through a one-step hydrothermal path which is economic and simple. The fact that the single phase Bi2WO6 dandelion was prepared and the sample possessed uniformly dandelion-like morphology comprising of edge nanosheets was confirmed by multifarious characterized results. Benefiting from such an unparalleled 3D morphology, n-type semiconductor 3D Bi2WO6 dandelion was made into gas sensor who exhibited unique good ethylene glycol sensing properties at a lower optimum operational temperature of 270 °C, i.e., high response value, excellent repeatability, a detection minimum limit of 1 ppm and so forth. Hence the novel 3D Bi2WO6 dandelion could be an ultra-sensitive ethylene glycol candidate semiconductor material.

Effect of carriers on deposition morphologies and catalytic performances of NiCo2O4

In this study, NiCo2O4 with different morphologies were fabricated using carriers by homogeneous coprecipitation combined with a sintering method. The phase and microstructure were characterized by XRD, SEM, EDS, TEM and BET, and the catalytic performances were investigated by NaBH4 hydrolysis experiments. These studies revealed that the deposition morphology of NiCo2O4 can be adjusted by using different kinds of carrier templates, and the supported NiCo2O4 samples presented the pine-needle-like, network-like, ball-cactus-like and dandelion-like morphologies respectively. The optimal catalytic activity, durability and stability make the network-like NiCo2O4 an appropriate catalyst for hydrogen generation of NaBH4 hydrolysis. It was found that the network-like NiCo2O4 is the most reusable and durable catalyst for ten consecutive cycles and 100% hydrogen generation conversion rate without obvious decrease among these morphologies.

Morphology dependant electrochemical performance of hydrothermally synthesized NiCo2O4 nanomorphs

The spinel nanostructured nickel cobaltite (NiCo2O4) with different morphologies has been successfully synthesized via facile surfactant assisted hydrothermal route. Tri-ethanolamine ethoxylate (TEA-ethoxylate) and PEG-600 were used as surfactants. The synthesized samples were characterized using various physicochemical techniques and were further used for fabrication of electrode for supercapacitor application. The effect of reaction temperature and surfactant on typical morphology of product and their electrochemical properties has been explored. The morphological features of as-synthesized samples were studied by Field emission scanning electron microscopy (FESEM). The surface area, pore volume and pore diameter were estimated by BET-BJH surface area analysis. The dandelion-like morphology of nickel cobaltite showed the highest surface area (58.76 m2 g−1) with uniform porosity. This morphology provides numerous electrochemical active sites for high electrochemical performance and resulted into the high specific capacitance (479 Fg−1 at scan rate 5 mVs−1) with high energy density (21.3 Whkg−1) and power density (150 Wkg−1).

Controllable synthesis of Eu3+ ions doped Zn(OH)F and ZnO micro-structures: Phase, morphology and luminescence property

Eu3+ ions doped Zn(OH)F and ZnO micro-structures with specific morphologies were synthesized by a simple hydrothermal method only through altering the addition amount of NH4F and hexamethylenetetramine (HMT). The phase structure, morphology and luminescence properties of the as-prepared samples were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), photoluminescence (PL) spectra and lifetime. The results indicate that the obtained Zn(OH)F:Eu3+ samples possess net-like and dandelion-like morphologies, which have an identical orthorhombic phase structure. It is found that the addition amount of raw materials such as NH4F and HMT plays a critical role for the formation of Zn(OH)F:Eu3+. If the addition amounts of NH4F or HMT are reduced by half, the hexagonal ZnO:Eu3+ sample with peanut-like morphology can be obtained. Under the excitation of UV light, both the as-prepared Zn(OH)F:Eu3+ and ZnO:Eu3+ samples exhibit the characteristic emission of the doped Eu3+.

A novel biomimetic dandelion structure-inspired carbon nanotube coating with sulfur as a lithium–sulfur battery cathode

Lithium–sulfur (Li–S) batteries have attracted considerable attention because of their high theoretical energy density. However, poor conductivity and a large volume change in S during cycling, together with a shuttle effect of polysulfides, severely restrict the battery performance, and remain a great challenge. Herein, inspired by a natural dandelion structure, we present a novel biomimetic S-coated carbon nanotube composite consisting of dandelion-like three-dimensional carbon nanotubes coated with S particles on the surface. Carbon nanotubes provide high-speed electron transfer pathways for S during cycling, while the special dandelion-like morphology provides a suitable environment for accommodating the volume change in S upon charge–discharge. The dandelion-like S-coated carbon nanotube-based Li–S batteries exhibit a stable capacity exceeding 760 mAh g−1 after 500 cycles at 0.1 C, along with a Coulombic efficiency as high as 99.9%. Even under repeated rounds of rate-performance measurements, and cycling at different charge versus discharge rates, the batteries retain high capacities and good recovery capabilities. In addition, the proportion of capacitive contribution in the overall capacity is high, indicating a good reversible capacity provided by the composite.

Influence of Ni/Cu ratio in nickel copper carbonate hydroxide on the phase and electrochemical properties

Transition metal compounds containing nickel and copper have been investigated as electrode materials for energy storage. (Ni,Cu)(OH)2CO3 and α-Ni(OH)2 with different Ni/Cu ratios are synthesized by a simple hydrothermal method. All the samples show the similar dandelion-like morphology. It is demonstrated that the mole ratio of Ni to Cu is a key factor to influence the phase and electrochemical performances of the products. Carbonate anions will be intercalated into nickel copper layered double hydroxides with a hydrotalcite structure when the sample is nickel-rich, which will lead to much better electrochemical properties compared with the copper-rich samples with crystalline (Ni,Cu)(OH)2CO3 structure. Among all the materials, sample (Ni0.89Cu0.11)2(OH)2CO3 can deliver the highest specific capacitance of 1017.3 F g−1 at 1 A g−1 and retain 68.5% of the original value after 4000 cycles at 5 A g−1. Meanwhile, an asymmetric capacitor which is assembled by using the optimized material as a positive electrode and activated carbon as a negative electrode exhibits a high energy density of 38.56 Wh kg−1 at a power density of 850.01 W kg−1 and a high power density of 8407.4 W kg−1 at an energy density of 21.7 Wh kg−1. Based on the above results, nickel copper carbonate hydroxides are of potential application for energy storage.

ChemInform Abstract: Pd@Pt Core-Shell Nanoparticles with Branched Dandelion-Like Morphology as Highly Efficient Catalysts for Olefin Reduction.

A facile synthesis based on the addition of ascorbic acid to a mixture of Na2 PdCl4, K2 PtCl6, and Pluronic P123 results in highly branched core-shell nanoparticles (NPs) with a micro-mesoporous dandelion-like morphology comprising Pd core and Pt shell. The slow reduction kinetics associated with the use of ascorbic acid as a weak reductant and suitable Pd/Pt atomic ratio (1:1) play a principal role in the formation mechanism of such branched Pd@Pt core-shell NPs, which differs from the traditional seed-mediated growth. The catalyst efficiently achieves the reduction of a variety of olefins in good to excellent yields. Importantly, higher catalytic efficiency of dandelion-like Pd@Pt core-shell NPs was observed for the olefin reduction than commercially available Pt black, Pd NPs, and physically admixed Pt black and Pd NPs. This superior catalytic behavior is not only due to larger surface area and synergistic effects but also to the unique micro-mesoporous structure with significant contribution of mesopores with sizes of several tens of nanometers.

Pd@Pt Core-Shell Nanoparticles with Branched Dandelion-like Morphology as Highly Efficient Catalysts for Olefin Reduction.

A facile synthesis based on the addition of ascorbic acid to a mixture of Na2 PdCl4, K2 PtCl6, and Pluronic P123 results in highly branched core-shell nanoparticles (NPs) with a micro-mesoporous dandelion-like morphology comprising Pd core and Pt shell. The slow reduction kinetics associated with the use of ascorbic acid as a weak reductant and suitable Pd/Pt atomic ratio (1:1) play a principal role in the formation mechanism of such branched Pd@Pt core-shell NPs, which differs from the traditional seed-mediated growth. The catalyst efficiently achieves the reduction of a variety of olefins in good to excellent yields. Importantly, higher catalytic efficiency of dandelion-like Pd@Pt core-shell NPs was observed for the olefin reduction than commercially available Pt black, Pd NPs, and physically admixed Pt black and Pd NPs. This superior catalytic behavior is not only due to larger surface area and synergistic effects but also to the unique micro-mesoporous structure with significant contribution of mesopores with sizes of several tens of nanometers.

Synthesis of nanofiber-composed dandelion-like CoNiAl triple hydroxide as an electrode material for high-performance supercapacitor

In this work, CoNiAl triple hydroxide with nanofiber-composed dandelion-like morphology was synthesized on nickel foam by a hydrothermal route. This delicate nanostructure was initiated from the rolling up of hydroxide nanosheets. The hierarchical nanostructure and optimized molar ratio of Co, Ni, and Al guarantees the high electrochemical performance of obtained samples. The maximum specific capacitance of 2,791 F g−1 for the as-prepared CoNiAl hydroxides was achieved at scan rate of 5 mV s−1 in 3 M KOH aqueous solution. The capacitance of material still remained 85 % after 2,000 charge–discharge cycles. These results demonstrated that the as-prepared CoNiAl triple hydroxide can be applied as a high-performance electrode material for supercapacitor.

Synthesis of nanocrystalline copper oxide with dandelion-like morphology by homogeneous precipitation method

Nanocrystalline copper oxide with dandelion-like morphology has been successfully synthesized by a simple homogeneous precipitation method using copper acetate and ammonia solution. It was obtained at low temperature (∼80°C) in short precipitation time. The formation of dandelion-like microspheres and their size depend on calcination temperature. The synthesized samples were characterized by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermal gravimetric analysis (TGA), UV–Visible diffuse reflectance spectroscopy (UV–Vis DRS), surface area measurements, field emission scanning electron microscopy (FE-SEM) coupled with energy dispersive X-ray analysis. The nanocrystalline copper oxide has been explored as a good catalyst for reduction of 4-nitrophenol with sodium borohydride.

Facile Synthesis of 3D Hierarchical Dandelion-like Co3O4 Microspheres for Superior Ethanol Gas Sensing Properties

Abstract Novel hierarchical dandelion-like Co3O4 microspheres have been successively synthesized via a facile solvothermal reaction and subsequent calcination. The calcined products exhibit well-fined dandelion-like morphology with sizes of about 2 µm. These microspheres are composed of numerous 1D nanorods arranged radially on the surface. The evolution process of dandelion-like microspheres has been investigated, and a possible evolution mechanism has been proposed. When evaluated as a gas sensor, the obtained dandelion-like Co3O4 microspheres exhibit superior ethanol gas sensing performance.

Influence of Alkali Treatment on Ti6Al4V Alloy and the HA Coating Deposited by Hydrothermal-Electrochemical Methods

Abstract The aim of this work is to investigate the influence of NaOH pretreatment time on the phases and morphologies of Ti6Al4V substrates and hydroxyapatite (HA) coatings. Ti6Al4V substrates were pretreated with a sodium hydroxide (NaOH) solution for different amounts of time (12, 24, 36, 48, and 60 h). After NaOH pretreatment, a three-dimensional porous network of sodium titanate gel was observed on the Ti6Al4V surface. Subsequently, HA deposition was achieved using the hydrothermal-electrochemical methods, while the electrolyte solution containing NaCl, K 2 HPO 4 ·3H 2 O, and CaCl 2 , was maintained at 120 °C and applied by a constant current density of 1.25 mA/cm 2 for 120 min. The results indicate that the growth pattern and micromorphology of the HA coating are all influenced by different pretreatment time. After pretreating Ti6Al4V substrates with NaOH for 12 h, needle-like structures are primarily formed on the HA coating, and some dandelion-like morphologies are presented. During 48 h NaOH solution pretreatment, the dandelion-like structures increase with the increase of time. However, the amount of the dandelion-shaped HA drops slightly, when pretreatment time is longer than 48 h. The orientation index of the (002) plane of HA reaches the minimum when Ti6Al4V substrates are pretreated for 48 h, whereas the crystallinity is the highest for this pretreatment time.

Effect of TiO<sub>2</sub> Seed Layer Thickness to the Growth of TiO<sub>2</sub> Nanostructures by Immersion Method for Memristive Device Application

TiO2 nanostructures were successfully grown on TiO2 thin film by solution-based method at low temperature. TiO2 thin film as a seed layer for the nanostructures growth was deposited on ITO substrate by RF magnetron sputtering method at 40 and 60 nm thicknesses. Then the TiO2 nanostructures were synthesized on the samples by keeping them floating with TiO2 layer facing down the vessel in 10M NaOH solution at 80°C for 45 min. Effect of seed layer thickness to the growth of TiO2 nanostructure and its memristive behaviour were investigated. Surface morphology and current-voltage measurement for its memristive behaviour were measured by FESEM image and Keithley 4200 semiconductor characterization system. It was found that 60 nm-TiO2 thin film result in the formation of dandelion-like morphology of TiO2 nanowires and gives better memristive behavior with larger switching loops when positive voltage was applied to the sample.

Solvothermal growth of three-dimensional TiO2 nanostructures and their optical and photocatalytic properties

Abstract Three-dimensional (3D) titania nanostructures assembled with ordered rutile nanorods have been fabricated via a surfactant-free and single-step solvothermal route. The effects of preparation parameters, including the reaction temperatures and the reactant concentrations, on the microstructure, optical properties and photocatalytic activity of the 3D TiO 2 nanostructures were investigated. The results revealed that 3D TiO 2 microspheres possessed a dandelion-like morphology composed of radially packed rutile nanorods. Increasing the reaction temperature leads to the formation of larger rutile crystals, but reduced the aspect ratios of nanorods. The morphology of products was dominated by irregular shapes with low titanium precursor concentration. The optical reflectance, absorption and photocatalytic properties of the samples were found to be significantly dependent on their morphology. 3D dandelion-like structures with tapered tips showed lower reflectance, more efficient light harvesting, higher surface area and consequently higher photocatalytic activity compared with those with flat tops and fragment of nanorod sectors. Moreover, TiO 2 products prepared with 0.4 M titanium precursor solution at 150 and 120 °C showed better or equivalent photocatalytic activity compared with Degussa P25 owing to high light harvesting ability as well as less aggregation for the unique 3D dandelion-like hierarchical structure. The growth mechanism of the 3D dandelion-like nanostructures under various preparation conditions was also discussed.