Hierarchical Flower-like Nanostructures Research Articles

Synthesis of ZnO@Fe2O3 microflowers with enhanced performance in volatile organic compound detection

Metal-oxide semiconductor is widely applied in gas sensor for volatile organic compound detection. However, these sensors usually exhibit poor selectivity and inferior sensitivity. Here, ZnO@Fe2O3 microflowers were synthesized using FeOOH microflowers as precursors via a simple solution reaction route, followed by heat treatment. The ZnO@Fe2O3 microflowers were characterized using a series of techniques, and their sensing responses to volatile organic compounds (VOCs) were evaluated in comparison with those of pristine Fe2O3. The ZnO@Fe2O3 microflower sensor exhibited better responses to several gases, especially acetone, with a response of 74.3 towards 100 ppm acetone, which is 2.85 times higher than that of the Fe2O3 microflower sensor. The sensor also presented high selectivity, reproducibility, and stability in sensing different VOCs. The large specific surface area, heterostructure, favorable hierarchical flower-like nanostructure assembled by the nanosheets, and high porosity of the ZnO@Fe2O3 microflowers contributed to its enhanced gas-sensing responses. Overall, this synthetic strategy for fabricating flower-like ZnO@Fe2O3 nanostructures can be widely applied.

Controllable Synthesis of Flower-like Hierarchical CuCo2S4 Nanostructure Arrays for High-Performance Hybrid Supercapacitors

Transition metal sulfides (TMSs) are considered as attractive materials in the areas of energy storage because of their unique redox properties, excellent electronic conductivity, as well as environmental friendliness. However, poor cyclic stability and limited electrochemical active sites hinder their further application. To address this issue, a flower-like hierarchical CuCo2S4 structure is constructed by a two-step hydrothermal method. In this nanostructure, CuCo2S4 grows outward to form a tightly bound hierarchical structure on the nickel foams (NFs). This oriented structure can provide more laminar gaps for electrolyte ion diffusion, exposing more reaction sites to increase the ion transport efficiency between the layers, reducing the ion transport resistance and improving the reaction kinetics. Thus, the CuCo2S4 electrode exhibits excellent energy storage performance, exhibiting a high specific capacity of 1415.6 F g−1 at 1 A g−1. After 10,000 cycles of 10 A g−1, it still has 91.9% of the initial performance. In addition, an asymmetrical supercapacitor (ASC) was constructed by choosing CuCo2S4 as the anode and RGO as the cathode, which has the maximum energy density (61.8 Wh Kg−1) at 812.1 W Kg−1 and significant cycling endurance (92.05% retention) at 10,000 turns. Briefly, the researchers successfully constructed an array of CuCo2S4 flower-like hierarchical nanostructures and confirmed their potential application in supercapacitors.

A sensitive electrochemical sensor based on graphene quantum dots/hierarchical flower-like gold nanostructures for determination of cytostatic drug flutamide

Using an electrochemical sensor with high sensing capability and manufacturing simplicity, flutamide (FLU) can be quantitatively measured. A glassy carbon electrode is modified with graphene quantum dots (GQDs) and hierarchical flower-like gold nanostructures (HFGNs). Combining GQDs and HFGNs enhanced the electrode surface and electron transfer rate, improving the signal's intensity and sensitivity. Nanostructure characterization, electrochemical characterization, and detection studies indicated the high performance of the platform in terms of sensitivity, selectivity, reproducibility, and stability. With these improvements, linear correlations were achieved between 0.01 and 400 µM, with a detection limit of 6.2 nM (based on 3Ssb/m). Pharmaceuticals and complex biological samples along with interfering agents have been successfully analyzed with this platform.

Template preparation of porous Pt-modified SnO2 microflowers for high-response detection of VOCs

Porous SnO2 microflowers consisting of uniform nanosheets modified by Pt nanoparticles were synthesized using a self-sacrificing template followed by a reduction strategy. The Pt@SnO2, SnO2–Se, and SnO2–S samples were characterized using a series of techniques. The gas-sensing behaviors of the samples toward volatile organic compounds (VOCs) were studied. The Pt@SnO2 sensors exhibited superior gas-sensing performance for formaldehyde gas. The Pt@SnO2 sensors presented a stronger response (100.2), shorter response–recovery times (14 s/23 s), and lower working temperature (200 °C) for 100 ppm formaldehyde gas. The Pt@SnO2 sensors also showed excellent responses toward other VOCs, such as 100 ppm ethanol (82.5), acetone (73.9), and isopropanol (62.1). The gas-sensing mechanism of the Pt@SnO2 sensors was examined. The larger available surface area, favorable hierarchical flower-like nanostructure assembled by nanosheets, larger pore size, and larger proportion of oxygen vacancies and adsorption-state oxygen species, smaller crystallite size, and spillover effect of Pt catalysts contributed to the enhanced gas-sensing behaviors of Pt@SnO2 sensors. Overall, the synthetic strategy for flower-like SnO2 nanostructures can be applied widely.

Controlled Synthesis of Flower-like Hierarchical NiCo-Layered Double Hydroxide Integrated with Metal-Organic Framework-Derived Co@C for Supercapacitors.

Layered double hydroxides (LDHs) have come to the foreground recently, considering their unique layered structure and short ion channels when they act as electrode materials for supercapacitors (SCs). However, due to their poor rate and cycle performance, they are not highly sought after in the market. Therefore, a flower-like hierarchical NiCo-LDH@C nanostructure with flake NiCo-LDH anchored on the carbon skeleton has emerged here, which is constructed by calcination and hydrothermal reaction and applying flake ZIF-67 as a precursor. In this structure, NiCo-LDH grows outward with abundant and homogeneously distributed Co nanoparticles on Co@C as nucleation sites, forming a hierarchical structure that is combined tightly with the carbon skeleton. The flower-like hierarchical nanostructures formed by the composite of metal-organic frameworks (MOFs) and LDHs have successfully enhanced the cycle and rate performance of LDH materials on the strength of strong structural stability, large specific surface area, and unique cooperative effect. The NiCo-LDH@C electrode displays superb electrochemical performance, with a specific capacitance of 2210.6 F g-1 at 1 A g-1 and 88.8% capacitance retention at 10 A g-1. Furthermore, the asymmetric supercapacitor (ASC) constructed with NiCo-LDH@C//RGO reveals a remarkable energy density of 45.02 W h kg-1 with a power density of 799.96 W kg-1. This project aims to propose a novel avenue to exploit NiCo-LDH electrode materials and provide theory and methodological guidance for deriving complex structures from MOF derivatives.

Biological Recognition-Based Electrochemical Aptasensor for Point-of-Care Detection of cTnI.

As a "gold standard biomarker", cardiac troponin I (cTnI) is widely used to diagnose acute myocardial infarction (AMI). For an early clinical diagnosis of AMI, it is necessary to develop a facile, fast and on-site device for cTnI detection. According to this demand, a point-of-care electrochemical aptasensor was developed for cTnI detection by coupling the advantages of screen-printed carbon electrode (SPCE) with those of an aptamer. Thiol and methylene blue (MB) co-labelled aptamer (MB-Apt-SH) was assembled on the surface of hierarchical flower-like gold nanostructure (HFGNs)-decorated SPCE (SPCE-HFGNs) to recognize and analyze cTnI. In the presence of cTnI, the specific biological recognition reaction between cTnI and aptamer caused the decrease in electrochemical signal. Under the optimal condition, this designed aptasensor showed wide linear range (10 pg/mL-100 ng/mL) and low detection limit for (8.46 pg/mL) for cTnI detection with high selectivity and stability. More importantly, we used a mobile phone coupled with a simple APP to efficiently detect cTnI in 10 μL 100% human serum samples, proving that this aptasensor has a promising potential in point-of-care testing.

Wide-spectrum detector based on hierarchical flower-like In2S3 nanostructures by solvothermal process

Hierarchical flower-like In2S3 nanostructures were synthesized using a solvothermal process. The device based on In2S3 nanostructure was fabricated and the photoresponse properties were investigated. The flower-like In2S3 nanostructures display a strong quantum confinement with a wide band response in range from ultraviolet (UV) to the visible region. The results indicated that the photodetector based on hierarchical flower-like [Formula: see text]-In2S3 nanostructures will have important applications in multiple band detection devices.

Electrochemical H2O2 sensor based on a Au nanoflower-graphene composite for anticancer drug evaluation

Reliable H2O2 sensors for in situ cellular monitoring under drug stimulation can be developed as a powerful and versatile tool for drug evaluation. Herein, a novel electrochemical biosensor capable of detecting and quantifying H2O2 was fabricated by graphene and shape-controlled gold nanostructures. With the help of polyelectrolytes, gold exhibited hierarchical flower-like nanostructures. This kind of nanozyme material exhibited a prominent electrochemical response for H2O2. Electrocatalytic activity for H2O2 reduction with high sensitivity (5.07◊10−4 mA μmol L−1 cm−2) and good detection capability (the lowest detection limit is 4.5 μmol L−1 (S/N = 3)) were achieved. This electrochemical biosensor was successfully used to measure the concentration of H2O2 released from HepG2 hepatoma cells. Ascorbic acid (AA) and Camellia nitidissima Chi saponins (CNCS) were selected as model drugs, and their anticancer activities were compared by in situ monitoring of H2O2. Interestingly, the electrochemical sensor showed remarkable sensitivity, accuracy, and rapidity compared with the traditional enzymatic detection kit. In brief, the as-synthesized nanostructured H2O2 sensors can be applied to assess the antitumor properties of candidate drugs and inspire developments for personalized health care monitoring and cancer treatment.

Adsorption sites and electron transfer characteristics of methyl orange on three-dimensional hierarchical flower-like nanostructures of Co-Al-layered double hydroxides: Experimental and DFT investigation

The dried layered double hydroxides (LDHs), have poor dispersibility, and are difficult to recycle in water. In this study, the cobalt-aluminum LDHs were prepared by hydrothermal reaction (BC@Co-Al-LDHs), and then further calcined to obtain hollow-structured BC@Co-Al-LDOs. The surface morphologies and physicochemical characteristics of these two materials were characterized. Simultaneously, batch tests were conducted to study their adsorption performances for methyl orange (MO). The maximum removal rate (90.24 %) and adsorption capacity (147.68 mg/g) of BC@Co-Al-LDOs for MO were 37.11 % and 60.72 mg/L higher than those of BC@Co-Al-LDHs, respectively. Based on the fitting results of the adsorption kinetic model, the type of MO adsorption by the two materials was chemisorption. Furthermore, density functional theory (DFT) was used to further study the adsorption mechanism of MO on the surface of these materials at the molecular level. The theoretical calculation results demonstrated that the SO3− in the MO was more prone to electrophilic reactions and accepted electrons from BC@Co-Al-LDHs, simultaneously, the Co adsorption site had the most accessible adsorption energy (−5.342 eV) contributing to the vertical adsorption. In addition, the partial density of states (PDOS) measurement revealed that MO interacted with the BC@Co-Al-LDHs essentially through s and p orbital hybridization.

Flower-like hierarchical Sn3O4/montmorillonite nanostructure for the enhanced microwave-induced degradation of rhodamine B

A flower-like hierarchical nanostructure of Sn3O4/montmorillonite is first reported in this work. The nanomaterial was prepared by a one-pot hydrothermal synthesis method using tin chloride as the precursor, and the physicochemical characteristics of the material were examined by instrumental analyses. The prepared nanostructure was evaluated as a catalyst in the microwave-induced removal of rhodamine B (RhB). The influences of Sn content, oxidant, time of irradiation, and initial concentration of RhB were investigated. The results showed homogeneously dispersed Sn3O4 in a montmorillonite support with a cubic phase, and crystallite size smaller than to Sn3O4 was obtained. XPS investigation revealed the Sn3O4 phase, which is consistent with the band gap energy of 2.75 eV from UV-DRS measurements. The homogeneous distribution of the Sn3O4 nanoparticles influenced the increasing specific surface area of the nanocomposite compared to montmorillonite. The enhanced physicochemical properties significantly enhanced the catalytic activity in microwave induced RhB oxidation, with the degradation efficiency reaching 99.9% after 20 min of treatment. The kinetics of catalytic oxidation were best fitted to the pseudo-second-order equation and obeyed the Langmuir-Hinshelwood kinetics model. Furthermore, the catalytic oxidation condition optimization using a Box-Behnken Design revealed the contribution of oxidant, pH and catalyst dose as influencing factors for the efficiency.

Comparative investigation on synthesis, morphological tailoring and photocatalytic activities of Bi2O2CO3 nanostructures

It is well established that the morphologies and sizes of photocatalysts have important effects on their photocatalytic activities; developing special nanostructures with excellent photocatalytic activity is a fundamental subject to promote the industrial application of photocatalysis technology. In this study, we have synthesized various Bi2O2CO3 nanostructures via different hydrothermal routes, including nanosheets, nanoplates, nanoparticles, nanosheet-assembled hierarchical nanotubes, pinecone-like hierarchical nanostructures, and carnation flower-like hierarchical nanostructures. The properties of the as-synthesized nanostructures were investigated by various techniques. Their photocatalytic activities were systematically compared by degrading methylene blue (MB) and reducing Cr(VI) ions under simulated-sunlight irradiation, revealing that they exhibit largely different photocatalytic activities. Among various Bi2O2CO3 nanostructures, the nanoparticles demonstrate the highest photodegradation activity for degrading MB, whereas the hierarchical nanotubes exhibit the highest photoreduction activity for reducing Cr(VI) ions. Moreover, the photodegradation of other organic pollutants over Bi2O2CO3 nanoparticles was also investigated. The underlying photocatalytic mechanism was discussed and analyzed in details.

SnSe/Cu<sub>2</sub>SnSe<sub>3</sub> Heterojunction Structure with High Initial Coulombic Efficiency for Lithium-Ion Battery Anodes

Due to high theoretical specific capacity and abundant reserves, tin selenide-based materials have received tremendous attentions in the fields of lithium-ion batteries. Nevertheless, the huge volume changes during insertion/de-intercalation processes deteriorate the Coulombic Efficiency greatly. In order to solve it, the researchers have made great efforts by means of controlling nanoparticles granularity, carbon coating, ion doping et al. In this study, SnSe/Cu2SnSe3 heterojunction nanocomposites were synthesized by solvo-thermal method. The resulting SnSe/Cu2SnSe3 is a three-dimensional flower-like hierarchical nanostructure composed of nanoscale thin lamellae of a thickness of 8-12 nm. The unique nanostructure could shorten the diffusion path of lithium ions and expedite charge transfer, and therefore enhance the reaction kinetics. Compared with SnSe, the initial Coulombic efficiency of SnSe/Cu2SnSe3 is raised from 59% to 90% as the anode material of lithium-ion batteries.

Adsorption Sites and Electron Transfer Characteristics of Methyl Orange on Three-Dimensional Hierarchical Flower-Like Nanostructures of Co-Al-Layered Double Hydroxides: Experimental and Dft Investigation

Adsorption Sites and Electron Transfer Characteristics of Methyl Orange on Three-Dimensional Hierarchical Flower-Like Nanostructures of Co-Al-Layered Double Hydroxides: Experimental and Dft Investigation

Simultaneous detection of dual biomarkers using hierarchical MoS2 nanostructuring and nano-signal amplification-based electrochemical aptasensor toward accurate diagnosis of prostate cancer

Accurate and reliable quantification of tumor biomarkers in clinical samples is of vital importance for early stage diagnosis and treatment of cancer. However, a poor specificity of prostate specific antigen (PSA) testing alone fostering overdetection and overtreatment, remains a great controversy in prostate cancer (PCa) screening. Here we report an electrochemical aptasensor using hierarchical MoS2 nanostructuring and SiO2 nano-signal amplification for simultaneous detection of dual PCa biomarkers, PSA and sarcosine, to enhance the diagnostic performance of PCa. In this strategy, hierarchical flower-like MoS2 nanostructures as functional interface accelerated intermolecular accessibility and improved DNA hybridization efficiency. Moreover, the spherical SiO2 nanoprobe that conjugated with both electroactive tags and DNA probes, allowed effective electrochemical signal amplification. By deliberately designing different hybridization modes, we individually implemented the optimization of PSA and sarcosine sensing system. Based on this, simultaneous determination of PSA and sarcosine was achieved, with limit of detection (LOD) down to 2.5 fg/mL and 14.4 fg/mL, respectively, as well as excellent selectivity. More importantly, using this approach, we could directly differentiate cancer patients with healthy ones for clinical serum samples. The ultrasensitive biosensor provides single-step analysis with simple operation and a small sample volume (∼12 μL), shedding new light on accurate diagnosis and early-detection of cancer in clinical applications.

Peering into the Formation of Template-Free Hierarchical Flowerlike Nanostructures of SrTiO3.

The development of efficient advanced functional materials is highly dependent on properties such as morphology, crystallinity, and surface functionality. In this work, hierarchical flowerlike nanostructures of SrTiO3 have been synthesized by a simple template-free solvothermal method involving poly(vinylpyrrolidone) (PVP). Molecular dynamics simulations supported by structural characterization have shown that PVP preferentially adsorbs on {110} facets, thereby promoting the {100} facet growth. This interaction results in the formation of hierarchical flowerlike nanostructures with assembled nanosheets. The petal morphology is strongly dependent on the presence of PVP, and the piling up of nanosheets, leading to nanocubes, is observed when PVP is removed at high temperatures. This work contributes to a better understanding of how to control the morphological properties of SrTiO3, which is fundamental to the synthesis of perovskite-type materials with tailored properties.

A smartphone-assisted portable biosensor using laccase-mineral hybrid microflowers for colorimetric determination of epinephrine

A novel smartphone-assisted portable biosensor based on laccase-mineral hybrid microflowers (La-HMFs) was applied for real-time, accurate and reliable quantification of epinephrine (EP). La-HMFs with flower-like hierarchical nanostructure was synthesized via biomineralization using Cu3(PO4)2⋅3H2O as the mineral. Characterization results revealed laccase molecules as the framework were immobilized within La-HMFs. Smartphone-assisted colorimetric assays showed wide linear detection range (1–400 μM) and favorable anti-interference ability for EP detection, and the detection limit was 0.6 μM. Further, due to the protective effect of Cu3(PO4)2⋅3H2O, the immobilized laccase exhibited good stability and desirable reusability.

Surfactant-free synthesis of 3D hierarchical flower-like NiO nanostructures with enhanced ethanol-sensing performance

Different morphologies hierarchical flower-like Nickel oxide nanostructures were fabricated by changing the volume of ammonia (Va = 1, 4, and 8 ml) under a template-free and low-cost hydrothermal method and subsequent calcinations. The nanoflowers were composed of two-dimensional (2D) nanosheets. The sensor based on the samples of Va = 8 exhibited the most excellent gas-sensing performance to ethanol. Moreover, a possible growth mechanisms were also proposed. The facile preparation method and the improved properties derived from the three-dimensional structures are significant in the synthesis and future applications of functional nanomaterials.

Shape-Controlled Hierarchical Flowerlike Au Nanostructure Microarrays by Electrochemical Growth for Surface-Enhanced Raman Spectroscopy Application.

How to fabricate Au nanostructures conveniently on microstructured/nanostructured arrays surface with low cost has become a crucial and urgent challenge. In this study, we demonstrate hierarchical flowerlike Au nanostructures with rich nanothorns (HF-AuNTs) through one-step electrochemical deposition. The morphology of the HF-AuNTs is easily manipulated by controlling the applied potential or precursor solution concentration of electrodeposition. The as-prepared HF-AuNTs possessing unique local morphology of thin petals and dense thorns are further applied in the Si micropit arrays to acquire HF-AuNTs microarrays. As an initial detection, these HF-AuNTs microarrays exhibit a fascinating surface-enhanced Raman spectroscopy consistency (relative standard deviation is 7.17%) and sensitivity with the limitation of crystal violet reaching to 10-10 M, and Rhodamine 6G reaching to 10-11 M. The HF-AuNTs microarrays with well-defined shape and elaborate structure may be applicated in SERS substrates, superhydrophobic materials, and so on.

Hierarchical WO3–NiO microflower for high sensitivity detection of SF6 decomposition byproduct H2S

In this work, hierarchical WO3–NiO microflowers have been designed and prepared through a controllable hydrothermal route for high sensitivity detection of H2S produced by SF6 decomposition. The hierarchical flower-like nanostructures assembled with numerous nanosheets were influenced by the introduction of WO3, which is regarded as a significant strategy for improving the gas sensing properties. The synthesized nanostructures were tested by various characterization to investigate the different microstructures of the nanocomposites. The H2S sensing performances of the sensors fabricated with these flower-like nanostructures were measured, which indicated that 3.0 at% WO3–NiO microflower based sensor possessed excellent properties such as higher gas responses and more prominent repeatability compared with those of other fabricated sensors. The enhanced performances might be mainly ascribed to the creation of the heterojunction at n-type WO3 and p-type NiO interface, which caused the improvement of the potential barrier and depletion layer. In addition, the larger specific surface area of flower-like nanostructures also possessed abundant sites for surface reaction.

Design of flower-like V2O5 hierarchical nanostructures by hydrothermal strategy for the selective and sensitive detection of xylene

Present work proposes the insight towards synthesis of flower-like vanadium oxide hierarchical nanostructures (V2O5 HNs) through a simple and template-free hydrothermal method and their utilization as a potential xylene gas sensing materials. XRD and XPS analysis supports to the configuration of highly crystalline orthorhombic phase of V2O5. Surface morphologies of V2O5 were controlled through varying the reaction times during hydrothermal synthesis. SEM and TEM studies undoubtedly corroborates that the flower-like V2O5 HNs (3–5 μm in diameters) are composed of large number of nanosheet- and nanoneedle-type structures. BET and BJH analysis supports to the mesoporous character of V2O5 HNs with specific surface area of 19.5291 m2/g. Gas sensing studies on as-fabricated V2O5 HNs sensors were performed towards a various target gases, temperatures, and varying concentrations thoroughly and described. Gas sensing studies demonstrate that the flower-like V2O5 HNs sensors are selective and effective towards xylene @300 °C. Among various V2O5 HNs sensors, the sensor based on V2O5-3 exhibits maximum response of 3.03 to 500 ppm xylene together with good response repeatability and long term stability (towards 100 ppm, Ra/Rg = 2.20) @300 °C. Finally, the selective detection of xylene using as-grown flower-like V2O5 HNs can cover the road in the direction of the development of sensing systems for the acute detection and monitoring of toxic xylene.