Co3O4 Nanostructured Sensor for Electrochemical Detection of H2O2 as a Stress Biomarker in Barley: Fe3O4 Nanoparticles-Mediated Enhancement of Salt Stress Tolerance.

This research investigates the enhancement of barley's resistance to salt stress by integrating nanoparticles and employing a nanostructured Co3O4 sensor for the electrochemical detection of hydrogen peroxide (H2O2), a crucial indicator of oxidative stress. The novel sensor, featuring petal-shaped Co3O4 nanostructures, exhibits remarkable precision and sensitivity to H2O2 in buffer solution, showcasing notable efficacy in complex analytes like plant juice. The research establishes that the introduction of Fe3O4 nanoparticles significantly improves barley's ability to withstand salt stress, leading to a reduction in detected H2O2 concentrations, alongside positive impacts on morphological parameters and photosynthesis rates. The developed sensor promises to provide real-time monitoring of barley stress responses, providing valuable information on increasing tolerance to crop stressors.

Co3O4 Nanopetals Grown on the Porous CuO Network for the Photocatalytic Degradation.

Designing a novel photocatalytic composite for the efficient degradation of organic dyes remains a serious challenge. Herein, the multi-layered Co3O4@NP-CuO photocatalyst with unique features, i.e., the self-supporting, hierarchical porous network as well as the construction of heterojunction between Co3O4 and CuO, are synthesized by dealloying-electrodeposition and subsequent thermal treatment techniques. It is found that the interwoven ultrathin Co3O4 nanopetals evenly grow on the nanoporous CuO network (Co3O4@NP-CuO). The three-dimensional (3D) hierarchical porous structure for the catalyst provides more surface area to act as active sites and facilitates the absorption of visible light in the photodegradation reaction. Compared with the commercial CuO and Co3O4 powders, the newly designed Co3O4@NP-CuO composite exhibits superior photodegradation performance for RhB. The enhanced performance is mainly due to the construction of heterojunction of Co3O4/CuO, greatly promoting the efficient carrier separation for photocatalysis. Furthermore, the possible photocatalytic mechanism is analyzed in detail. This work provides a promising strategy for the fabrication of a new controllable heterojunction to improve photocatalytic activity.

Preparation of Fe3O4-Ag Nanocomposites with Silver Petals for SERS Application.

The formation of silver nanopetal-Fe3O4 poly-nanocrystals assemblies and the use of the resulting hetero-nanostructures as active substrates for Surface Enhanced Raman Spectroscopy (SERS) application are here reported. In practice, about 180 nm sized polyol-made Fe3O4 spheres, constituted by 10 nm sized crystals, were functionalized by (3-aminopropyl)triethoxysilane (APTES) to become positively charged, which can then electrostatically interact with negatively charged silver seeds. Silver petals were formed by seed-mediated growth in presence of Ag+ cations and self-assembly, using L-ascorbic acid (L-AA) and polyvinyl pyrrolidone (PVP) as mid-reducing and stabilizing agents, respectively. The resulting plasmonic structure provides a rough surface with plenty of hot spots able to locally enhance significantly any applied electrical field. Additionally, they exhibited a high enough saturation magnetization with Ms = 9.7 emu g-1 to be reversibly collected by an external magnetic field, which shortened the detection time. The plasmonic property makes the engineered Fe3O4-Ag architectures particularly valuable for magnetically assisted ultra-sensitive SERS sensing. This was unambiguously established through the successful detection, in water, of traces, (down to 10-10 M) of Rhodamine 6G (R6G), at room temperature.

One-step electrodeposition of CuSCN/CuI nanocomposite and its hole transport-ability in inverted planar perovskite solar cells.

The synthesis of CuSCN/CuI nanocomposite by single-step electrodeposition is developed. The surface morphology and film thickness are controlled by changing the electrochemical potential and deposition time. The mixed-phase formation of CuSCN/CuI is confirmed through x-ray diffraction and Raman spectral analysis. Nanopetal (NP) like morphology of CuSCN/CuI is observed in FESEM micrographs. Interestingly, the NPs density and thickness are increased with increasing the deposition potential and time. The device fabricated using CuSCN/CuI nanocomposite as a hole transport layer (HTL) which is grown for 2 min delivers the best photovoltaic performance. The maximum power conversion efficiency of 18.82% is observed for CuSCN/CuI NP with a density of 1153µm-2and thickness of 142 nm. The charge transfer ability of the CuSCN/CuI NP HTL is analyzed by electrochemical impedance spectroscopy. Based on the observation, moderate charge transport resistance and optimum film thickness are required for achieving maximum photovoltaic performance in perovskite solar cells (PVSCs). Thus, the developed CuSCN/CuI NP HTL is a potential candidate for PVSCs.

Silver decorated 2D nanosheets of GO and MoS2serve as nanocatalyst for water treatment and antimicrobial applications as ascertained with molecular docking evaluation.

In this work, synthesis of graphene oxide (GO) and reduced graphene oxide (rGO) was realized through a modified Hummers route. Different concentrations (5 and 10 wt%) of Ag were doped in MoS2and rGO using a hydrothermal technique. Synthesized Ag-MoS2and Ag-rGO were evaluated through XRD that confirmed the hexagonal structure of MoS2along with the transformation of GO to Ag-rGO as indicated by a shift in XRD peaks while Mo-O bonding and S=O functional groups were confirmed with FTIR. Morphological information of GO and formation of MoS2nanopetals as well as interlayer spacing were verified through FESEM and HRTEM respectively. Raman analysis was employed to probe any evidence regarding defect densities of GO. Optical properties of GO, MoS2, Ag-rGO, and Ag-MoS2were visualized through UV-vis and PL spectroscopy. Prepared products were employed as nanocatalysts to purify industrial wastewater. Experimental results revealed that Ag-rGO and Ag-MoS2showed 99% and 80% response in photocatalytic activity. Besides, the nanocatalyst (Ag-MoS2and Ag-rGO) exhibited 6.05 mm inhibition zones againstS. aureusgram positive (G+) and 3.05 mm forE. coligram negative (G-) in antibacterial activity. To rationalize biocidal mechanism of Ag-doped MoS2NPs and Ag-rGO,in silicomolecular docking study was employed for two enzymes i.e.ß-lactamase and D-alanine-D-alanine ligase B (ddlB) from cell wall biosynthetic pathway and enoyl-[acylcarrier-protein] reductase (FabI) from fatty acid biosynthetic pathway belonging toS. aureus. The present study provides evidence for the development of cost-effective, environment friendly and viable candidate for photocatalytic and antimicrobial applications.

Surface Study of CuO Nanopetals by Advanced Nanocharacterization Techniques with Enhanced Optical and Catalytic Properties.

In the present work, a facile one-step hydrothermal synthesis of well-defined stabilized CuO nanopetals and its surface study by advanced nanocharacterization techniques for enhanced optical and catalytic properties has been investigated. Characterization by Transmission electron microscopy (TEM) analysis confirmed existence of high crystalline CuO nanopetals with average length and diameter of 1611.96 nm and 650.50 nm, respectively. The nanopetals are monodispersed with a large surface area, controlled morphology, and demonstrate the nanocrystalline nature with a monoclinic structure. The phase purity of the as-synthesized sample was confirmed by Raman spectroscopy and X-ray diffraction (XRD) patterns. A significantly wide absorption up to 800 nm and increased band gap were observed in CuO nanopetals. The valance band (VB) and conduction band (CB) positions at CuO surface are measured to be of +0.7 and -1.03 eV, respectively, using X-ray photoelectron spectroscopy (XPS), which would be very promising for efficient catalytic properties. Furthermore, the obtained CuO nanopetals in the presence of hydrogen peroxide ( H 2 O 2 ) achieved excellent catalytic activities for degradation of methylene blue (MB) under dark, with degradation rate > 99% after 90 min, which is significantly higher than reported in the literature. The enhanced catalytic activity was referred to the controlled morphology of monodispersed CuO nanopetals, co-operative role of H 2 O 2 and energy band structure. This work contributes to a new approach for extensive application opportunities in environmental improvement.

A Ni(OH)2 nanopetals network for high-performance supercapacitors synthesized by immersing Ni nanofoam in water.

Developing a facile and environmentally friendly approach to the synthesis of nanostructured Ni(OH)2 electrodes for high-performance supercapacitor applications is a great challenge. In this work, we report an extremely simple route to prepare a Ni(OH)2 nanopetals network by immersing Ni nanofoam in water. A binder-free composite electrode, consisting of Ni(OH)2 nanopetals network, Ni nanofoam interlayer and Ni-based metallic glass matrix (Ni(OH)2/Ni-NF/MG) with sandwich structure and good flexibility, was designed and finally achieved. Microstructure and morphology of the Ni(OH)2 nanopetals were characterized. It is found that the Ni(OH)2 nanopetals interweave with each other and grow vertically on the surface of Ni nanofoam to form an "ion reservoir", which facilitates the ion diffusion in the electrode reaction. Electrochemical measurements show that the Ni(OH)2/Ni-NF/MG electrode, after immersion in water for seven days, reveals a high volumetric capacitance of 966.4 F/cm3 at a current density of 0.5 A/cm3. The electrode immersed for five days exhibits an excellent cycling stability (83.7% of the initial capacity after 3000 cycles at a current density of 1 A/cm3). Furthermore, symmetric supercapacitor (SC) devices were assembled using ribbons immersed for seven days and showed a maximum volumetric energy density of ca. 32.7 mWh/cm3 at a power density of 0.8 W/cm3, and of 13.7 mWh/cm3 when the power density was increased to 2 W/cm3. The fully charged SC devices could light up a red LED. The work provides a new idea for the synthesis of nanostructured Ni(OH)2 by a simple approach and ultra-low cost, which largely extends the prospect of commercial application in flexible or wearable devices.

Mechanism Investigation of High-Performance Li-Polysulfide Batteries Enabled by Tungsten Disulfide Nanopetals.

Understanding the reaction kinetics and mechanism of Li-polysulfide batteries is critical in designing advanced host materials for improved performance. However, up to now, the reaction mechanism within the Li-polysulfide batteries is still unclear. Herein, we study the reaction mechanism of a high-performance Li-polysulfide battery by in situ X-ray diffraction (XRD) and density functional theory (DFT) calculations based on a multifunctional host material composed of WS2 nanopetals embedded in rGO-CNT (WS2-rGO-CNT) aerogel. The WS2 nanopetal serves as a "catalytic center" to chemically bond the polysulfides and accelerate the polysulfide redox reactions, and the 3D porous rGO-CNT scaffold provides fast and efficient e-/Li+ transportation. Thus, the resulting WS2-rGO-CNT aerogel accommodating the polysulfide catholyte enables a stable cycling performance, excellent rate capability (614 mAh g-1 at 2 C), and a high areal capacity (6.6 mAh cm-2 at 0.5 C). In situ XRD results reveal that the Li2S starts to form at an early stage of discharge (at a depth of 25% of the lower voltage plateau) during the discharge process, and ß-S8 nucleation begins before the upper voltage plateau during the recharge process, which are different from the conventional Li-S battery. Moreover, the WS2 itself could be lithiated/delithiated during the cycling, making the lithiated WS2 (Li xWS2, 0 ≤ x ≤ 0.3) a real host material for Li-polysulfide batteries. DFT calculations suggest that Li xWS2 (0 ≤ x ≤ 0.3) exhibits moderate binding/anchoring interactions toward polysulfides with adsorption energies of 0.51-1.4 eV. Our work reveals the reaction mechanism of the Li-polysulfide batteries and indicates that the lithiated host plays an important role in trapping the polysulfides.

Mesoporous Nickel Oxide (NiO) Nanopetals for Ultrasensitive Glucose Sensing.

Glucose sensing properties of mesoporous well-aligned, dense nickel oxide (NiO) nanostructures (NSs) in nanopetals (NPs) shape grown hydrothermally on the FTO-coated glass substrate has been demonstrated. The structural study based investigations of NiO-NPs has been carried out by X-ray diffraction (XRD), electron and atomic force microscopies, energy dispersive X-ray (EDX), and X-ray photospectroscopy (XPS). Brunauer-Emmett-Teller (BET) measurements, employed for surface analysis, suggest NiO's suitability for surface activity based glucose sensing applications. The glucose sensor, which immobilized glucose on NiO-NPs@FTO electrode, shows detection of wide range of glucose concentrations with good linearity and high sensitivity of 3.9 µA/µM/cm2 at 0.5 V operating potential. Detection limit of as low as 1 µΜ and a fast response time of less than 1 s was observed. The glucose sensor electrode possesses good anti-interference ability, stability, repeatability & reproducibility and shows inert behavior toward ascorbic acid (AA), uric acid (UA) and dopamine acid (DA) making it a perfect non-enzymatic glucose sensor.

Enhanced catalytic activity without the use of an external light source using microwave-synthesized CuO nanopetals.

We report enhanced catalytic activity of CuO nanopetals synthesized by microwave-assisted wet chemical synthesis. The catalytic reaction of CuO nanopetals and H2O2 was studied with the application of external light source and also under dark conditions for the degradation of the hazardous dye methylene blue. The CuO nanopetals showed significant catalytic activity for the fast degradation of methylene blue and rhodamine B (RhB) under dark conditions, without the application of an external light source. This increased catalytic activity was attributed to the co-operative role of H2O2 and the large specific surface area (≈40 m2·g-1) of the nanopetals. We propose a detail mechanism for this fast degradation. A separate study of the effect of different H2O2 concentrations for the degradation of methylene blue under dark conditions is also illustrated.

Ethanol-Mediated 2D Growth of Cu2O Nanoarchitectures on Nanoporous Cu Templates in Anhydrous Ethanol.

Two types of cupric oxide (Cu2O) nanoarchitectures (nanobelts and nanopetal networks) have been achieved via immersion nanoporous copper (NPC) templates in anhydrous ethanol. NPC templates with different defect densities have been prepared by dealloying amorphous Ti60Cu40 ribbons in a mixture solution of hydrofluoric acid and polyvinylpyrrolidone (PVP) with different ratios of HF/PVP. Both a water molecule reactant acting as OH- reservoir and the ethanol molecule serving as stabilizing or capping reagent for inhibiting the random growth of Cu2Oplayed a role of the formation of 2-dimensional Cu2O nanoarchitectures. Cu2O nanobelts are preferred to form in anhydrous ethanol on the NPC templates from Ti60Cu40 ribbons dealloying in the solution with low HF concentration and small addition of PVP; and Cu2O nanopetals are tended to grow in anhydrous ethanol from the NPC templates from Ti60Cu40 ribbons dealloying in the solution with high HF concentration and large addition of PVP. With increasing the immersion time in anhydrous ethanol, Cu2O nanopetals united together to create porous networks about 300 nm in thickness. The defect sites (i.e., twin boundary) on nanoporous Cu ligaments preferentially served as nucleation sites for Cu2O nanocrystals, and the higher defect density leads to the formation of uniform Cu2O layer. Synergistic effect of initial microstructure of NPC templates and stabilizing agent of ethanol molecule results in different Cu2O nanoarchitectures.

Effects of Graphene Nanopetal Outgrowths on Internal Thermal Interface Resistance in Composites.

Thermal resistance at the interface between fiber and matrix is often the determining factor influencing thermal transport in carbon fiber composites. Despite its significance, few experimental measurements of its magnitude have been performed to date. Here, a 3ω method is applied to measure the interfacial thermal resistance between individual carbon fibers and an epoxy matrix. The method incorporates bulk and interfacial regions to extract interfacial characteristics. Measured values indicate an average thermal interface resistance of 18 mm(2) K/W for an interface between bare fiber and epoxy, but the average value drops to 3 mm(2) K/W after a microwave plasma chemical vapor deposition of two-dimensional graphene nanopetals on the carbon fiber surface.

Self-assembled metastable γ-Ga2O3 nanoflowers with hexagonal nanopetals for solar-blind photodetection.

Metastable γ-Ga2O3 nanoflowers assembled from hexagonal nanopetals are successfully constructed by the oxidation of metallic Ga in acetone solution. The nanoflowers with a hollow interior structure exhibit a short response time and a large light-current-dark-current ratio under a relatively low bias voltage, suggesting an especially important potential application in solar-blind photodetection.