Rose-like Morphology Research Articles

Facile synthesis of rose-like composites of zeolites and layered double hydroxides: Growth mechanism and enhanced properties

Excellent performances of various materials often depend on high specific surface areas. Therefore, increase of specific surface areas is one of the most important means to improve the properties and performances of materials. Herein, we report a facile strategy to prepare novel composite materials of zeolites and hydrotalcite-like layered double hydroxides, with high specific surface areas. The composites with a rose-like morphology were synthesized hydrothermally by adding synthetic zeolites to the raw materials used for the formation of hydrotalcite. The resultant composites were shown to contain two distinct layered double hydroxides with different Mg/Al molar ratios. Nitrogen (N2) adsorption−desorption measurements showed that the specific surface areas and the pore volumes of these composites increased by an order of magnitude in comparison with hydrotalcite. The new composites were shown to be capable of effectively removing Cr(VI), Cu(II) and methylene blue from aqueous environments and had better performances for the latter two contaminants than hydrotalcite. Moreover, this strategy potentially opens up the synthesis of new composite materials with tunable compositions and enhanced properties for environmental and other applications.

Bismuth Selenide Nanostructured Clusters as Optical Coherence Tomography Contrast Agents: Beyond Gold-Based Particles.

Optical coherence tomography (OCT) is an imaging technique currently used in clinical practice to obtain optical biopsies of different biological tissues in a minimally invasive way. Among the contrast agents proposed to increase the efficacy of this imaging method, gold nanoshells (GNSs) are the best performing ones. However, their preparation is generally time-consuming, and they are intrinsically costly to produce. Herein, we propose a more affordable alternative to these contrast agents: Bi2Se3 nanostructured clusters with a desert rose-like morphology prepared via a microwave-assisted method. The structures are prepared in a matter of minutes, feature strong near-infrared extinction properties, and are biocompatible. They also boast a photon-to-heat conversion efficiency of close to 50%, making them good candidates as photothermal therapy agents. In vitro studies evidence the prowess of Bi2Se3 clusters as OCT contrast agents and prove that their performance is comparable to that of GNSs.

In Situ-Forming Magnetic Fe3O4 Nanoroses on Defect-Controllable Mesoporous Graphene Oxide for Enzyme-Mimic Sensing

Glucose detection is always a central issue for researchers due to its comprehensive use in the fermentation industry, food industry, and biomedical industry. Due to the easy activity loss and poor stability of the enzymatic sensor, the development of a nonenzymatic sensor is a desired substitution for target recognition. But working under a low alkaline environment with high performance is always a challenge. To address the above issue, an enzymatic oxidation method was used to design a rose-like nano-Fe3O4/GO film to mimic the catalytic function of glucose oxidase. Abundant porous defects with increased oxygen-containing groups were created on the GO surface, and then Fe3O4 crystals were constrained to grow surrounding the defective sites. The rose-like morphology provides an ultrahigh specific surface area to effectively capture OH–, which shows excellent sensitivities of glucose detection in varied pH environments from 9 to 13 at a very low operation potential.

Morphology-Dependent Photocatalytic Degradation of Organic Pollutant and Antibacterial Activity with CdS Nanostructures.

Efficient removal of organic pollutants from waste water by nanostructured photocatalysts has become an emerging research due to its importance in environmental remediation. Herein, CdS nanostructures with different morphologies i.e., spherical, nanopetal and rose-like have been synthesized by wet chemical method using TEA as a structure directing agent. The morphology, crystal structure, composition, surface area and optical properties of the nanostructures are investigated by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDX), Brunauer-Emment-Teller (BET) analyser, Ultraviolet-Visible (UV-Vis) absorption spectroscopy and Photoluminescence (PL) spectroscopy. XRD patterns indicate the existence of hexagonal phase of CdS in all the three morphologies. The SEM images confirm the morphological transformation of spherical CdS nanoparticles (NPs) to nanopetal and rose-like morphology with the increase in concentration of TEA in the synthesis process. UV-visible absorption spectra show that rose-like CdS nanostructure exhibits red-shift of absorption wavelength compared to spherical and nanopetal CdS nanostructures. The increase in intensity of PL peak of rose-like CdS at 576.6 nm compared to that of spherical and nanopetal CdS, confirms the presence of more S vacancies or defect states. The BET specific surface areas of spherical, nanopetal and rose-like CdS nanostructures are determined to be 4.18, 6.64 and 8.93 m₂/g, respectively. The EIS Nyquist plot confirms the higher electron transfer efficiency of rose-like CdS than that of spherical and nanopetal CdS. The photocatalytic activity of these three nanostructures are evaluated for the degradation of methylene blue (MB) dye in water solution under sunlight irradiation. Among the three structures, rose-like CdS nanostructure shows highest photocatalytic efficiency (96.5%) under sunlight irradiation within 120 min of sunlight irradiation. Antibacterial activity of the synthesized CdS nanostructures is performed against two Gram-positive and Gram-negative bacteria and rose-like CdS shows more activity against both types of bacteria than that of spherical and nanopetal CdS.

Versatile MoS2 hollow nanoroses for a quick-witted removal of Hg (II), Pb (II) and Ag (I) from water and the mechanism: Affinity or Electrochemistry?

In this paper, a nano Molybdenum disulphide with an open cavity at the centre (hollow) and a rose flower-shaped structure (MoS2HNR) has been synthesized using a novel, micelle assisted hydrothermal method and has been successfully demonstrated the ability of the nano MoS2 for the simultaneous removal of the toxic metal ions: Hg (II), Pb (II) and Ag (I) from water. A single treatment of contaminated real water samples with MoS2HNR can rapidly (in ∼5- 30 min) decrease the concentration of Hg (II), Pb (II) and Ag (I) simultaneously from 10,000 ppb to 0.49, 20.5, and 11.62 ppb respectively, the levels less than the safe limits suggested by the U.S Environmental Protection Agency (USEPA) with an efficiency of ≥ 99% at a V/m ratio of 10,000, in real water samples. The adsorption capacities for Hg (II), Ag (I) and Pb (II) are ∼1991, 1350 and 1267 mg/g, respectively at pH 7.0 and exhibited high distribution coefficients (Kd) values of ∼108 mL/g. The rose-like morphology and the open cavity of the material attributed to the excellent removal property as the structure offers a large number of active S2− sites for adsorption. A possible mechanism for the high-efficiency removal and the order of adsorption Hg (II) >Ag (I) >Pb (II) is explained based on the affinity between S2− and metal ions and the electrochemistry factor. The MoS2HNR retains its morphology even after six trails of reuse.

Lightweight aerogels based on bacterial cellulose/silver nanoparticles/polyaniline with tuning morphology of polyaniline and application in soft tissue engineering

Herein, polyaniline (PANI) with tuning morphology was in-situ synthesized within bacterial cellulose (BC)/silver nanoparticles hydrogels (AgNPs) that were prepared by green hydrothermal reduction method in different molarity of 0.01 and 0.25 of HCl solution along with the presence of polyethylene glycol (PEG). The synthesis of PANI in the presence of PEG in 0.01 M HCl led to the formation of rose-like morphology within nanocomposite aerogels with a size of 1.5–5.2 μm. All aerogels had the porosity and shrinkage of higher than 80% and lower than 10%, respectively. Rheology results showed a higher value of storage modulus (G′) than that of loss modulus (G″) for all samples over the whole frequency regime. It confirmed by the loss factor (tan δ) value of less than 1 for all hydrogel samples. The synthesis of PANI within BC/Ag in 0.25 M of HCl solution resulted in a substantial rise of G′ to nearly 1.5 × 104 Pa that was one order of magnitude higher than that of other hydrogels. However, the synthesis condition of PANI did not influence the antibacterial activity. In spite of unfavorable cell attachment onto nanocomposite aerogels, the cell proliferation increased steadily over the whole period of incubation.

High-performance supercapacitor electrode based on 3D rose-like β-Ni(OH)2/rGO nanohybrid

Supercapacitors have been extensively used in power storage and power management components for its outstanding performances in recent years. In this paper, the novel 3D rose-like β-Ni(OH)2/rGO nanohybrid is prepared as supercapacitor electrode through one-step hydrothermal method. The prepared Ni(OH)2/rGO nanohybrid exhibited a rose-like morphology with a diameter of about 3 μm, which were assembled from sheets of nickel hydroxide and reduced graphene oxide layered overlap uniformly. In this state, graphene distributed uniformly around the interior of nanohybrid instead of acting as a substrate. The results of electrochemical test show that the specific capacity of Ni(OH)2/rGO nanohybrid could achieve to 802 F/g at 2 A/g. Furthermore, when the current density is 8 A/g, the capacitance still preserved 94.55% after 1000 times constant current charge and discharge. It displays superior cycle stability. Additionally, 3D Ni(OH)2/rGO nanohybrid could be simply transmitted to NiO/rGO nanohybrid. These works are of crucial importance for the research and development of novel supercapacitor electrodes and power storage components.

Concise fabrication of 3D rose-like BiOBrxI1−x with exceptional wide spectrum visible-light photocatalytic activity

In this work, 3D rose-like BiOBrxI1−x photocatalysts with highly efficient visible-light-driven photocatalytic activities were successfully prepared via acetic acid assisted hydrolysis within 15 min at room temperature. The crystal structure, morphology, surface area, composition, interfacial charge separation, band gaps of BiOBrxI1−x solid solutions are characterized by XRD, SEM, HRTEM, BET, XPS, photocurrent and UV–vis DRS. Besides, the photocatalytic properties including degradation, mineralization and reusability of the BiOBr0.8I0.2 were evaluated by bisphenol A (BPA), rhodamine B (RhB) and methyl Orange (MO) as the target pollutant compounds under visible light. Results shows that the larger BET surface area, 3D rose-like morphology, favorable (110) exposed reactive surface, suitable band gap and adequate potential of the valence band give the positive impact on the exceptional visible photocatalytic activity of BiOBr0.8I0.2, which exceeded other reported BiOX-based solid solutions. This work would enlighten an effortless and feasible strategy to fabricate high efficiency catalysts, yet push the forward pace of the photocatalytic practical application.

Gas Sensing Properties of Hydrothermally Synthesized Button Rose-Like WO3 Thin Films

In this paper, we have synthesized the WO3 button rose-like morphology directly grown on glass substrate using NaOH as an etching agent by hydrothermal method at 100°C. The formation of the WO3 button rose and its structural, optical, surface morphological and electrical properties were studied by various characterization techniques. The button rose-like morphology and orthorhombic crystal structure were confirmed by scanning electron microscopy (SEM) and x-ray diffraction techniques (XRD), respectively. The optical spectroscopy measurements reveal the band gap energy of WO3 button rose-like morphology varied between 2.2 and 2.4 eV. It is seen that the button rose-like morphology plays a crucial role in gas sensing properties. The as-synthesized WO3 button rose shows a gas response of about 262% at 6 ppm of NO2 gas. Particularly, this gas sensor shows better gas sensitivity towards NO2 gas than the other gases. Because of the high value of gas sensitivity, the reported WO3 with button rose-like morphology could be a suitable candidate for NO2 sensing.

Rose-like Ni3S4 as battery-type electrode for hybrid supercapacitor with excellent charge storage performance

Rose-like Ni3S4 microflowers are successfully synthesized by a novel two-step hydrothermal technique. X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) characterization are used to identify the spinel structure and rose-like morphology of the synthesized Ni3S4. The cyclic voltammetry and galvanostatic charge–discharge tests demonstrate improved electrochemical performance. The Ni3S4 microflower shows enhanced pseudocapacitive performance of approximately 1797.5 F g−1 at a current density of 0.5 A g−1, and the kinetic analysis reveals a diffusion controlled faradaic characteristic of Ni3S4 (28.66% capacitive contributions). Moreover, a hybrid supercapacitor is successfully assembled with Ni3S4 as the positive electrode and active carbon (AC) as the negative electrode. The Ni3S4//AC device exhibits a relatively high energy density of 18.625 Wh kg−1, a maximum power density of 1500.2 W kg−1 as well as an excellent cycling performance (approximately 93% capacitance retention over 5000 cycles).

3D mesoporous rose-like nickel-iron selenide microspheres as advanced electrocatalysts for the oxygen evolution reaction

The development of efficient and stable non-noble metal-based electrocatalysts for the oxygen evolution reaction (OER) is one of the essential challenges for the upcoming hydrogen economy. Herein, 3D mesoporous nickel iron selenide with rose-like microsphere architecture was directly grown on Ni foam via a successive two-step hydrothermal method. The unique 3D mesoporous rose-like morphology leads to a higher number of active sites as well as fast mass and electron transport through the entire electrode, and facilitates the release of O2 bubbles formed during the OER catalysis. As a result, the synthesized Ni0.76Fe0.24Se exhibits superior OER performances, with an ultralow overpotential of 197 mV needed to produce a current density of 10 mA·cm–2 in 1 M KOH, outperforming all transition metal selenide OER catalysts reported to date.

Hydrothermal synthesis of ammonioalunite with hexagonal rose-like morphology

In this study, a novel superstructure of hexagonal rose-like ammonioalunite was produced by hydrothermal synthesis in acidic condition. Urea was a precipitant in the system. The sharp peaks in the XRD pattern and the clear electron diffraction spots in selected-area electron diffraction (SAED) pattern indicated that ammonioalunite was highly crystallized. SEM images proved that the average diameter of the prepared ammonioalunite is ∼8 μm with a thickness of ∼6 μm. This highly ordered 3D superstructure can expand the scope of potential applications of ammonioalunite in the areas of ceramics, catalysis, electronics, and optoelectronics. The possible mechanism is that the rose-like ammonioalunite was obtained by self-assembling from nanosheets with spiral growth.

Hierarchically nanostructured vanadium nitride microspheres assembled with porous nanosheets fabricated by a template-free route

In this research, hierarchically nanostructured vanadium nitride (VN) microspheres were successfully prepared by a template-free method. ZnO, behaving as a sacrificial phase, was selectively leached out during nitridation of Zn3(OH)2(V2O7)·(H2O)2 microspheres with NH3, inducing a network structure. The VN microsphere was assembled with porous nanosheets. Extraordinary, the VN microsphere mimicked the morphology of the initial precursor and exhibited a rose-like morphology. The diameter of the microsphere was in the range of 1–3µm, and the thickness of the porous nanosheets was typically approximately 30nm. In addition, this facile and novel synthetic strategy can be further extended to the preparation of other hierarchically nanostructured transition metal nitrides.

Template Free Architecture of Hierarchical Nanostructured ZnIn₂S₄ Rose-Like Flowers for Solar Hydrogen Production.

We have demonstrated the controlled synthesis of hierarchical nanostructured ZnIn₂S₄ using a facile template free hydrothermal/solvothermal method. The effect of solvents on the morphology and microstructure of ZnIn₂S₄ has been studied by using water, methanol and ethylene glycol as a solvents. The hierarchical nanostructure, i.e., rose-like morphology composed of very thin (5–6 nm) nanoplates of length ˜1 μm which was obtained in aqueous mediated ZnIn₂S₄. The porous structure (distorted flowers) and agglomerated nanoparticles were obtained using methanol-and ethylene glycol-mediated ZnIn₂S₄. Considering the band gap in the visible region, ZnIn₂S₄ is used as a solar light driven photocatalyst. An ecofriendly photocatalytic process for the conversion of poisonous H₂S into H₂ which is a green unconventional energy source has been demonstrated. The nanostructured ZnIn₂S₄ is employed as a photocatalyst for hydrogen production from H₂S via a solar light-driven eco-friendly approach. The stable photocatalytic activity of hydrogen evolution, i.e., 3964 μmol ⁻¹ was obtained using 0.5 gm of such hierarchical nanostructured ZnIn₂S₄ under visible light irradiation. The unique hierarchical nanostructured ZnIn₂S₄ ternary semiconductor having hexagonal layer is expected to have potential applications in solar cells, LEDs, charge storage, electrochemical recording, thermoelectricity, other prospective electronic and optical devices.

Metal occupancy and its influence on thermal stability of synthetic saponites

Due to high surface acidity and thermal stability, saponite has important applications in various fields. In this study, saponites with different Mg/Zn ratios (0–6) and a fixed Si/Al ratio of 5.43 were synthesized under hydrothermal condition. The resultant synthetic saponites were characterized by using XRD, FTIR, TG, SEM and MAS NMR. The characterization results demonstrated that, with a decrease of Mg/Zn ratio, both the crystallinity and layer stacking order of saponite were increased, and rose-like morphology was observed in Zn-saponite. Al3+ preferentially occupied tetrahedral sites in Si-O tetrahedral sheet in all synthetic saponites. A decrease of Mg/Zn ratio in octahedral sheet could improve the substitution extent of Al3+ for Si4+ and resulted in an increase of Al(IV)/Al(VI) ratio in the resultant saponite, which might be a crucial factor to control the crystal growth of saponite. The dehydroxylation temperature of saponite depended strongly on the Mg/Zn ratio and the replacement of Al3+ for Mg2+ and Zn2+ in octahedral sheets, due to their different bond strength. A ‘one-to-one’ mode was proposed for the substitution of Al3+ for Mg2+ and Zn2+ in octahedral sheets of the synthetic saponites.

Ultrasound-enhanced milling in the synthesis of phase-pure, highly crystalline ZnAl-layered double hydroxide of low Zn(II) content

Dry milling followed by ultrasonic irradiation in the presence of small amounts of aqueous NaOH, was used to synthesise ZnAl-layered double hydroxide (LDH). The synthetic conditions were optimised and the Zn(OH)2, ZnO, and Al(OH)3 contaminants were removed by rinsing with aqueous NH3 solution from the sample prepared in the optimum conditions. Thus, phase-pure ZnAl-layered double hydroxide was obtained with high crystallinity. All materials produced during the syntheses were characterised by X-ray diffractometry, and a rose-like morphology was observed by scanning electron microscopy in the phase-pure sample. By changing the initial Zn/Al ratio, it was revealed that an LDH with low zinc content was always formed, probably through substitution of some of the Zn2+ ions by Al3+ ions in the gibbsite lattice.

Synthesis, morphology, and luminescence of ZnNb2O6 nanocrystals by hydrothermal method

The effect of hydrothermal treatment conditions on the formation, morphology, crystal growth, and photoluminescence of columbite-type ZnNb2O6 nanocrystals having rose-like morphology that were directly formed from aqueous precursor solutions of ZnSO4 and NbCl5 in the presence of aqueous ammonia was investigated. The crystallization of ZnNb2O6 nanocrystals was observed at 210 °C, but the hydrothermal treatment at 240 °C for 5 h under weakly basic condition around pH=8.4 was necessary for the sufficient crystallite growth of columbite-type ZnNb2O6 phase. On the other hand, the solid product formed at 240 °C from the precursor solution at pH=9.0 was almost amorphous. The observation by means of the transmission electron microscopy, selected area diffraction, and energy dispersive X-ray spectrometry showed that the ZnNb2O6 particles with the morphology like flower or rose consisted of arrayed nanosized-sheets having crystallite size of 11 nm. The ZnNb2O6 particles grew from about 1 to 4μm accompanying crystal growth with morphological change into rose-like shape via the solution and precipitation mechanism as hydrothermal holding time at 240 °C increased from 5 to 72 h. The as-prepared ZnNb2O6 nanocrystals showed a broad-band emission in the UV-blue region centered at 420 nm (and peaked at 360 nm) under excitation at 276 nm.

Green engineered ZnO nanopowders by Banyan Tree and E. tirucalli plant latex: auto ignition route, photoluminescent and photocatalytic properties

A simple and eco-friendly solution combustion route was used to prepare ZnO nanoparticles (ZNPs) using Banyan Tree (BT) and Euphorbia tirucalli (ET) plant latexes as fuels. The final products were characterized by powder x-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), UV-visible, scanning electron microcopy (SEM) and transmission electron microscopy (TEM). The PXRD result reveals the formation of hexagonal phase with Wurtzite structure. The crystallite size obtained from TEM was found to be ∼20–25 nm. SEM results reveal rose-like morphology with BT latex and hexagonal shaped with ET latex. The energy band gap of ZNPs obtained by BT and ET latex were found to be 3.20 and 3.38 eV, respectively. Photoluminescence (PL) emission peaks at ∼421, 458, 505, 522, 628 and 695 nm were observed in both the samples when excited at 383 nm. These emission peaks were mainly attributed to deep level oxygen (blue–green) defect and exciton (UV) defects, respectively. The international commission on illumination (CIE) chromaticity co-ordinates, as well as co-ordinated color temperature (CCT), were estimated from the emission spectra; the values (x, y) were very close to national television system committee (NTSC) standard values of pure white emission. Photocatalytic activity (PCA) of ZNPs prepared was studied in detail. The ZNPs prepared using BT latex showed highest PCA under sunlight. The results demonstrate that the synthesized product could be quite useful for display applications as well as photocatalyst. Further, the material prepared by this route was found to be non-toxic, environmentally friendly and could be a potential alternative to economical routes.

Additive-free solvothermal synthesis of hierarchical flower-like LiFePO4/C mesocrystal and its electrochemical performance

Three dimensional hierarchical flower-like lithium iron phosphate (LiFePO4) mesocrystals were successfully synthesized via a solvothermal approach with the utilization of a mixture of water/ethylene glycol/dimethylacetamide (H2O/EG/DMAC) as co-solvent. No other surfactant or template agent was used and beautiful micro-sized LiFePO4 mesoporous structures with a special rose-like morphology were obtained. The hierarchical LiFePO4 mesocrystals were assembled by well crystallized nano-sized LiFePO4 thin plates with a thickness around 100 nm. The characteristics and electrochemical dynamics as well as performance of the obtained hierarchical flower-like LiFePO4 mesocrystals were carefully investigated. The flower-like hierarchical LiFePO4 mesocrystals showed a high initial lithium intercalation capability of 147 mA h g−1 at a current density of 17 mA g−1 (0.1 C), which should be attributed to the high specific surface area resulting from the mesoporous superstructure and well crystallized LiFePO4 nano-plate composition units. Polyvinylpyrrolidone (PVP) was introduced during the solvothermal synthesis as an in situ carbon coating source. The obtained flower-like C-coated LiFePO4 mesocrystals exhibited even better initial lithium intercalation capability of 161 mA h g−1 at 0.1 C and showed improved lithium storage performance at high rates as well as good cyclic stability.

Hydrothermal Synthesis and Characterization of Novel MoS<sub>2</sub> Nanoflowers Directed by Ionic Liquid

MoS2 with rose-like morphology have been successfully synthesized using by an ionic liquid-directed hydrothermal synthesis. XRD results showed that the as-prepared MoS2 directed by ionic liquid Brij56 have the good peaks. SEM images revealed that the MoS2 nanoflowers had rose-like morphology composed of many stacked sheets. TEM images showed that MoS2 nanoflowers have incompactly petal-like stacked structure. These results showed that ionic liquid Brij56 could effectively influence the morphology of MoS2. Ionic liquid played a crucial role as a structure-directed reagent in the formation of MoS2 nanoflowers and the possible growth mechanism of MoS2 nanoflowers was also discussed.