Flower-shaped Nanostructures Research Articles

Flower-like nickel oxide nanostructures: Superior ammonia gas sensing and efficient dye removal behavior under UV–visible light illumination

In this study, we fabricated the NiO nanostructures using a straightforward solvothermal technique. The NiO nanoparticles were characterized using various analytical techniques. The FESEM images clearly show the flower-like structure of NiO nanoparticles. These nanostructures were then employed as a sensor to detect the presence of highly toxic ammonia (NH3) gas. The flower-shaped nanostructures of NiO played a vital role in improving sensing performance. Moreover, the NiO sensor displayed rapid response to 100 ppm ammonia at room temperature, with responses/recovery times of 40 s/44 s. This research holds promise as a viable approach for effectively sensing and detecting NH3 gas. The NiO exhibited excellent photocatalytic activity and degradation rates of 80% and 84.75% for Methyl orange (MO) and methylene blue dye (MB) respectively under UV-visible light irradiation. The NiO nanoflower remains unaffected after recycling MB dye degradation. This effective photocatalytic performance might be due to the formation of flower-like morphology. This underscores the potential of NiO as a promising candidate for applications in environmental and healthcare safety applications.

Influence of defects on the linear and nonlinear optical properties of Cu-doped rutile TiO2 microflowers.

Defects and disorder work as controlling parameters to alter the electronic structure of nanostructures and significantly influence their electronic, magnetic, and nonlinear optical (NLO) properties. In this study, we found that defect engineering is an effective strategy for tailoring the linear and nonlinear optical properties of Cu-doped titanium oxide (TiO2) flower-shaped nanostructures. The concentration of chemical doping of Cu in the TiO2 lattice creates intermediate defect states that impact electronic bandgap reduction and tunable defect luminescence. The estimation of the bandgap from density functional theory calculation follows the same trend of bandgap narrowing with Cu doping. The XPS study reveals that oxygen defects are responsible for bandgap narrowing and quenching of the PL intensity. A single-beam Z-scan technique with open and closed aperture configurations using ultrashort pulses centered at 532 nm excitation wavelength was used to study the NLO measurements. The open aperture reveals saturable absorption, whereas the closed aperture shows self-focusing behavior. The nonlinear absorption coefficient and refractive index extracted from NLO measurements demonstrate the linear dependence on the defect concentration and bandgap. The effects of heterogeneous dopants and lattice disorder on the nonlinear absorption behavior of these nanostructures are discussed in comparison with the figure of merit, non-linear refractive index, and absorption coefficient. The tunable NLO properties achieved by controlling such dopant-induced defects boost the scope of these nanostructures as optical limiting, optical switching, and optical photodiode applications.

Structural, morphological, and magneto-optical investigations of pure and (Sn, Zn) co-doped CuO nanoparticles: A novel corrosion inhibitor in acidic media

The present study reports work to synthesize metal oxide semiconductors of pure and (Sn, Zn) co-doped copper oxide (CuO) nanoparticles, with the chemical formula of Cu1–2xSnxZnxO (x = 0.000, 0.005, 0.010, and 0.020), via the co-precipitation method. The structural, morphological, optical, and magnetic properties were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV–vis), photoluminescence spectroscopy (PL), and vibrating-sample magnetometer (VSM), respectively. XRD results revealed the successful preparation of the monoclinic CuO phase, with small traces of secondary phase SnO appearing at samples of x = 0.010 and x = 0.020. The size of the prepared nanoparticles, obtained from XRD and TEM, showed an overall decrease when increasing the (Sn, Zn) co-doping concentrations, leading to an increase in the surface area appropriate for magnetic applications. At samples of x = 0.005 and x = 0.010, the co-dopants changed morphology from large spheres into nanorods and nanokernels. The diameters of the nanorods increased from 8.5 nm to 24.15 nm, while their lengths decreased from 51 nm to 48 nm. However, a flower-shaped nanostructure was observed in the x = 0.020 sample. FTIR confirmed the fingerprint vibration modes represented by antisymmetric vibration νas(Cu─O) in the crystal lattice. The first decrease in size was accompanied by a decrease in the energy gap caused by the lattice shrinkage, which in turn is caused by the vacancies and energy states in the bandgap stimulated by Sn and Zn ions. Following this decrease, there was an increase in the energy gap because of the shift in Fermi level to a higher energy state that is suitable for solar cell applications. PL results confirmed the excitation dependence nature of these nanoparticles. Correspondingly, the prepared nanoparticles can be utilized as potential applicants for blue chip and near-UV white light-emitting devices. VSM data revealed that paramagnetic and weak ferromagnetic behavior coexist in the co-doped nanoparticle samples. Through the electrochemical impedance spectroscopy and polarization measurements, the anticorrosion performance of these nanoparticles on mild steel has been studied in 0.5 M HCl solutions at 30 °C. The impedance results revealed that the corrosion process takes place under activation control. The polarization measurements showed that the prepared nanoparticles behave as a mixed-type inhibitor with 83 % efficiency in the x = 0.020 sample.

Hydrophilic ionic liquid assisted hydrothermal synthesis of ZnO nanostructures with controllable morphology.

Nanostructured ZnO with controllable morphology was prepared by a hydrothermal method in the presence of three different hydrophilic ionic liquids (ILs), 1-ethyl-3-methylimidazolium methylsulfate, ([C2mim]CH3SO4), 1-butyl-3-methylimidazolium methylsulfate, ([C4mim]CH3SO4) and 1-ethyl-3-methylimidazolium ethylsulfate, ([C2mim]C2H5SO4) as soft templates. The formation of ZnO nanoparticles (NPs) with and without IL was verified using FT-IR and UV-visible spectroscopy. X-ray diffraction (XRD) and selected area electron diffraction (SAED) patterns indicated the formation of pure crystalline ZnO with a hexagonal wurtzite phase. Field emission scanning electron microscopic (FESEM) and high-resolution transmission electron microscopic (HRTEM) images confirmed the formation of rod-shaped ZnO nanostructures without using IL, whereas the morphology varied widely following addition of ILs. With increasing concentrations of [C2mim]CH3SO4, the rod-shaped ZnO nanostructures transformed into flower-shaped nanostructures whereas with rising concentrations of [C4mim]CH3SO4 and [C2mim]C2H5SO4 the morphology changed into petal- and flake-like nanostructures, respectively. The selective adsorption effect of the ILs could protect certain facets during the formation of ZnO rods and promote the growth in directions other than [0001] to yield petal- or flake-like architectures. The morphology of ZnO nanostructures was, therefore, tunable by the controlled addition of hydrophilic ILs of different structures. The size of the nanostructures was widely distributed and the Z-average diameter, evaluated from dynamic light scattering measurements, increased as the concentration of the IL increased and passed through a maximum before decreasing again. The optical band gap energy of the ZnO nanostructures decreased when IL was added during the synthesis which is consistent with the morphology of the ZnO nanostructures. Thus, the hydrophilic ILs serve as self-directing agents and soft templates for the synthesis of ZnO nanostructures and the morphology and optical properties of ZnO nanostructures are tunable by changing the structure of the ILs as well as systematic variation of the concentration of ILs during synthesis.

Phase-Tuned MoS2 and Its Hybridization with Perovskite Oxide as Bifunctional Catalyst: A Rationale for Highly Stable and Efficient Water Splitting.

The efficient realization of bifunctional catalysts has immense opportunities in energy conversion technologies such as water splitting. Transition metal dichalcogenides (TMDs) are considered excellent hydrogen evolution catalysts owing to their hierarchical atomic-scale layered structure and feasible phase transition. On the other hand, for efficient oxygen evolution, perovskite oxides offer the best performance based on their rational design and flexible compositional structure. A unique way to achieve an efficient hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in a single-cell configuration is through the hybridization of TMDs with perovskite oxides to form a bifunctional electrocatalyst. Here, we report a simple yet effective strategy to inherently tune the intrinsic properties of a TMD based on MoS2 and its hybridization with LaCoO3 perovskite oxide to deliver enhanced electrocatalytic activity for both the HER and OER. Detailed Raman and XPS measurements highlighted a clear phase transformation of MoS2 from a semiconducting to metallic phase by effectively tailoring the precursor compositions. Based on this, the morphological features yielded an interesting spherical flower-shaped nanostructure with vertically aligned petals of MoS2 with increased surface-active edge sites suitable for the HER. Subsequent hybridization of nanostructured MoS2 with LaCoO3 provides a bifunctional catalytic system with an increased BET surface area of 33.4 m2/g for an overall improvement in water splitting with a low onset potential (HER: 242 mV and OER: 1.6 V @10 mA cm-2) and Tafel slope (HER: 78 mV dec-1; OER: 62.5 mV dec-1). Additionally, the bifunctional catalyst system exhibits long-term stability of up to ∼400 h under continuous operation at a high current density of 50 mA cm-2. These findings will pave the way for developing cost-effective and less complex bifunctional catalysts by simply and inherently tuning the influential material properties for full-cell electrochemical water splitting.

Cu Nano-Roses Self-Assembly from Allium cepa, L., Pyrolysis by Green Synthesis of C Nanostructures

Carbon nanostructures are achieved by bio-waste Allium cepa, L., (onion vulgaris) peels through pyrolysis at 900 °C. They contain dispersed elements derived by their bio-precursors, like Mg, Ca, S, Na, K, and Cu. Here, we report the self-assembly of new Cu flower-shaped nanostructures organized as nano-roses. Remarkably, the nano-roses show rolled-up petals of Cu0 with a high chemical stability in air, exhibiting an intrinsic pure Cu crystalline phase. This suggests the exceptional potentiality to synthesize Cu0 nanostructures with novel physical/chemical properties. The size, morphology, and chemical composition were obtained by a combination of high-resolution scanning electron microscopy, energy dispersive X-ray spectroscopy, energy dispersive X-ray diffraction, and Raman spectroscopy.

Synthesis and antibacterial activity of cellulose acetate sheets modified with flower-shaped AlOOH/Ag

Modified cellulose acetate antibacterial material was obtained by immobilizing Al/Ag nanoparticles on fabric fibres in water and subsequent hydrolysis of this nanoparticles under mild reaction condition. AlOOH/Ag self-assembled flower-shaped nanostructures consist of AlOOH nanoplates and Ag inclusions. The AlOOH nanosheets size is of 150–300 nm, thickness is 5–7 nm. The silver inclusions were from 5 to 30 nm in size. Flower-shaped AlOOH/Ag nanostructures change the charge of fibres and stabilize Ag nanoparticles against agglomeration. The positive charge of the modified fibres improves the bacteria adsorption due to electrostatic interaction. The antibacterial activity of the nanoparticles and modified material arise due to the slow Ag+ migration into the medium from stabilized Ag nanoparticles. The nanoparticles and modified cellulose acetate sheets were characterized by transmission and scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction analysis, FTIR spectroscopy. The release of silver ions to the medium remains low for 70 h with AlOOH/Ag@CA reducing all the tested bacterial strains below the limit of detection (102 CFU/mL) within 3 h for Escherichia coli and 6 h for MRSA due to local effects of silver on adsorbed bacteria. The antibacterial activity of modified cellulose acetate fabric allows this method of modification to be exploited to produce materials for biomedical applications.

Highly sensitive formaldehyde gas sensors based on Y-doped SnO2 hierarchical flower-shaped nanostructures

In this work, we have successfully prepared Y-doped SnO2 hierarchical flower-like nanostructures through a facile one-step hydrothermal method for the purpose of improving the formaldehyde gas sensing performance of conventional SnO2 semiconductor nanomaterials. The products were characterized by diverse techniques, which revealed that trivalent Y cations have been introduced into the crystal lattice of SnO2 and they exhibited lots of regular flower-like nanostructures consisting of several layers of rough and porous flakes. At an optimal working temperature of 180 °C, the fabricated gas sensor based on Y-doped SnO2 shown much better gas sensing properties to formaldehyde compared with SnO2 due to the combination of this distinctive three-dimensional hierarchical flower-like nanostructures and doping of Y ions. In particular, the detectable formaldehyde minimum limit has been reduced to 1 ppm. Consequently, Y-doped SnO2 hierarchical flower-like nanostructures are expected to become ideal gas sensing materials of highly sensitive gas sensors for formaldehyde detection due to their excellent gas sensing performance.

Nanosheets Self-Assembled 3D LiFeO4/Graphene as Cathode Material for Lithium-Ion Batteries

In order to understand the feasibility of using graphene as cathode materials for lithium-ion batteries, this paper uses graphene as an additive to prepare graphene-coated three-dimensional flower-shaped FeO4 nanostructures by one-step hydrothermal method. The obtained composite nano-material is composed of FeO4 nano flower-balls assembled by graphene and dozens of nanosheets. The crystal structure and morphology of the material were characterized by XRD and SEM, and their electrochemical properties were also studied. After cycling 50 times at a current density of 1000 m Ah/g, the reversible capacity of the FeO4/graphene composite still reaches 503.1 m Ah/g and the capacity retention rate is as high as 82%.

Preparations of Bi-doped SnO2 hierarchical flower-shaped nanostructures with highly sensitive HCHO sensing properties

In order to improve the gas sensing performance of traditional SnO2 semiconductor nanomaterials, Bi-doped SnO2 hierarchical flower-shaped nanostructures had been synthesized by a one-step hydrothermal route. Diverse techniques characterization results collectively revealed that Bi ions have been successfully doped into SnO2 lattice and samples present numerous uniform flower-shaped nanostructures composed of many layered petal-like thin nanosheets. Benefiting from such unique 3D hierarchical flower-shaped nanostructures and Bi doping, the sensors based on Bi-doped SnO2 exhibited superior gas sensing performance concluding higher response value, faster response/recovery time, good stability and excellent selectivity to HCHO at the optimum operating temperature of 170 °C. Therefore, Bi-doped SnO2 hierarchical flower-shaped nanostructures could be used as a candidate semiconductor gas sensing materials for manufacturing highly sensitive HCHO gas sensors in the future.

Synthesis of flower-shaped hybrid nano structures with standard plant molecules and their antimicrobial, peroxidase-like activities

Synthesis of flower-shaped hybrid nano structures with standard plant molecules and their antimicrobial, peroxidase-like activities

Flower-shaped gold nanoparticles: Preparation, characterization, and electrocatalytic application

The modification of a glassy carbon electrode with gold nanoparticles was pursued, characterized, and examined for electrocatalytic applications. The fabrication process of this electrode involved assembling the gold nanoparticles atop of amino group grafted glassy carbon electrode. The scanning electron microscopy indicated the deposition of gold nanoparticles in flower-shaped nanostructures with an average particle size of ca. 150nm. Interestingly, the electrode exhibited outstanding enhancement in the electrocatalytic activity toward the oxygen evolution reaction, which reflected from the large negative shift (ca. 0.8V) in its onset potential, in comparison with that observed at the bulk unmodified glassy carbon and gold electrodes. Alternatively, the Tafel plot of the modified electrode revealed a significant increase (∼one order of magnitude) in the apparent exchange current density of the oxygen evolution reaction upon the modification, which infers a faster charge transfer. Kinetically, gold nanoparticles are believed to facilitate a favorable adsorption of OH− (fundamental step in oxygen evolution reaction), which allows the charge transfer at reasonably lower anodic polarizations.

A facile route for the flowerlike Mg7B4O13 · 7H2O nanostuctures: Synthesis, growth mechanism and thermal treatment

In the presence of the surfactant poly(vinyl pyrrolidone) (PVP), 3D hierarchical flower-shaped Mg7B4O13·7H2O nanostructures were synthesized via a facile precipitation process using Mg(NO3)2·6H2O and Na2B4O7·10H2O as the raw materials. The nanostructures with diameters of 0.8–1.2μm are composed of numerous polycrystalline nanosheets with thickness of about 10nm. The possible growth mechanism for the flower-shaped nanostructures was proposed based on the systematic structural and property characterizations including XRD, SEM, TEM, IR and N2 adsorption–desorption. The phase transformation can be observed during the calcination process, and the flower-shaped nanostructures can be successfully maintained after calcination at 550°C and 650°C. The adsorption–desorption experiments show the appearance of mesopores before and after calcination co-existed with small amount of macropores. The highest surface area of 111m2/g and largest pore volume of 0.37cm3/g are obtained in these hierarchical porous Mg3B2O6 nanoflowers. These novel porous borate-based materials could be applied in drug delivery, catalysis, environmental abatement, energy storage, etc.

Synthesis of magnetic nanostructures: Shape tuning by the addition of a polymer at low temperature

We report a simple method for shape-controlled synthesis of iron oxide spinels such as magnetite (Fe3O4) and maghemite (γ-Fe2O3) nanostructures using a thermoresponsive polymer poly(vinyl methyl ether) (PVME) by the alkaline hydrolysis of iron salt at low temperature (20 °C). Microscopic analysis confirmed the formation of needle- and flower-shaped iron oxide nanostructures depending on reaction conditions. High-resolution transmission electron microscopic analysis of the needle- and flower-shaped nanostructures as well as their corresponding selected area electron diffraction patterns revealed that the formed nanostructures are crystalline in nature. X-ray diffraction study reveals the formation of well-crystalline pure Fe3O4 and γ-Fe2O3 nanostructures under different reaction conditions. Fourier transform Infra-red spectroscopic analysis confirms the adsorption of PVME on the surface of iron oxide nanostructures. Finally, the magnetic properties of γ-Fe2O3 and Fe3O4 nanostructures is studied that shows the superparamagnetic behavior of the formed iron oxide nanostructures.

A nanoflower shaped gold-palladium alloy on graphene oxide nanosheets with exceptional activity for electrochemical oxidation of ethanol

We report on a new and facile method for the preparation of well-dispersed gold-palladium (AuPd) flower-shaped nanostructures on sheets of graphene oxide (GO). Transmission electron microscopy and high angle annular dark field STEM were used to characterize the morphology and composition of the new nanohybrids. The AuPd/GO composites display high electrocatalytic activity for the oxidation of ethanol in strongly alkaline medium as examined by cyclic voltammetry and chronoamperometry. Both the current density (13.16 mA · cm−2 at a working potential of −0.12 V) and the long-time stability are superior to a commercial Pd-on-carbon catalyst which is attributed to the cooperative action of the catalytic activities of Au and Pd, and the good dispersion of the alloy on the nanosheets.

Facile Route to an Efficient NiO Supercapacitor with a Three-Dimensional Nanonetwork Morphology

NiO nanostructures with three distinct morphologies were fabricated by a sol-gel method and their morphology-dependent supercapacitor properties were exploited. The nanoflower- shaped NiO with a distinctive three-dimensional (3D) network and the highest pore volume shows the best supercapacitor properties. The nanopores in flower-shaped nanostructures, offering advantages in contact with and transport of the electrolyte, allow for 3D nanochannels in NiO structure, providing longer electron pathways. The XPS and EIS data of the NiO nanostructure confirm that the flower-shaped NiO, which has the lowest surface area among the three morphologies, was effectively optimized as a superior electrode and yielded the greatest pseudocapacitance. This study indicates that forming a 3D nanonetwork is a straightforward means of improving the electrochemical properties of a supercapacitor.

Self-assembly of hierarchical ZnSnO3-SnO2 nanoflakes and their gas sensing properties

A new type of hierarchical ZnSnO3-SnO2 flower-shaped nanostructure composed of thin nanoflakes as secondary units is successfully prepared through a simple hydrothermal process. The polyhedral ZnSnO3 core acts as a sacrificed template for the growth of hierarchical SnO2 nanoflakes, and the average thickness of SnO2 nanoflakes is around 25 nm. The time-dependent morphology evolution of ZnSnO3-SnO2 samples was investigated, and a possible formation mechanism of these hierarchical structures is discussed. The gas sensor based on these novel ZnSnO3-SnO2 nanostructures exhibits high response and quick response- recovery traits to ethanol (C2H5OH). It is found that ZnSnO3-SnO2 nanoflakes have a response of 27.8 to 50×10−6 C2H5OH at the optimal operating temperature of 270 °C, and the response and recovery time are within 1.0 and 1.8 s, respectively.

Synthesis and Room Temperature Ferromagnetism of Flower-shaped Mn Doped ZnO Nanostructures

Large-scale flower-shaped Mn doped ZnO nanostructures have been grown on silicon substrates by simple thermal evaporation at atmospheric pressure. The flower-shaped nanostructure makes up of many nanorods, which are rooted in one center. Analysis of X-ray diffraction, high-resolution transmission electron microscopy and Raman spectra results reveal that the products are of single phase with wurtzite structure. Elemental mapping results show that no impurity clusters exist in the doped materials. The photoluminescence spectra demonstrate that many oxygen vacancies exist in the doped materials, and the crystal quality is improved and the content of oxygen vacancies is decreased by annealing treatment. The flower-shaped Mn doped ZnO nanostructures exhibit ferromagnetic ordering above room temperature, and its magnetization is decreased by the annealing treatment, which indicates that the magnetic behavior of the doped materials may be related to the interaction between Mn doping and the oxygen vacancies.

Morphology and phase selective synthesis of Cu xO ( x = 1, 2) nanostructures and their catalytic degradation activity

Cu x O ( x = 1, 2) nanocrystals have been synthesized by the composite-hydroxide-mediated approach. The obtained nanocrystals were characterized by X-ray diffraction, energy dispersive X-ray spectroscopy, scanning electron microscopy, transmission electron microscopy, and UV–vis spectrum. The morphology of the nanocrystals changed from sphere-shaped nanostructures to flower-shaped nanostructures, and finally to nanowires associated with phase transformation from CuO to Cu 2O by increasing the temperature. The possible phase transformation mechanism was discussed. The catalytic degradation activity of the Cu x O ( x = 1, 2) nanocrystals to methyl orange was also investigated. The photocatalytic ability of the sphere-shaped nanostructures is much higher than that of the nanowires, owing to its absorption of wider range of light energy. This work provides a new facile synthesis route of Cu x O ( x = 1, 2) nanocrystals and suggests their possible application in organic pollutants removal.

Self-assembled 3-D flower-shaped SnO2 nanostructures with improved electrochemical performance for lithium storage

Abstract Flower-shaped SnO 2 nanoplates were successfully synthesized via a simple hydrothermal treatment of a mixture of tin(II) dichloride dihydrate (SnCl 2 ·2H 2 O) and sodium citrate (Na 3 C 6 H 5 O 7 ·2H 2 O) in alkali solution. The obtained SnO 2 nanoplates were less than 5 nm thick and self-assembled into flower-shaped nanostructures. The introduction of citrate was essential for the preparation of the SnO 2 nanoplates. The nanoscale shape and self-assembled architecture of SnO 2 nanoparticles were mainly controlled by the alkalinity of the solution. When the self-assembled SnO 2 nanostructures were used as anode materials in Li-ion batteries, they exhibit a reversible capacity of 670 mA h g −1 after 30 cycles and an average capacity fading of 0.95% per cycle after the second cycle. The good electrochemical performance of the SnO 2 sample prepared via the hydrothermal synthesis indicates the possibility of fabricating specific self-assembled three-dimensional nanostructures for Li-ion batteries.