Template-free Hydrothermal Synthesis Research Articles

Sensitive and fast electrochemical recognition of nitroaromatic explosives in liquid phase using ultrathin graphitic carbon nitride nanotubes

In the present work, a simple, effective method to synthesis high-quality carbon nitride nanotubes with ∼90 nm diameter and 5–9 nm in thickness along with a high-yield (63 %) via template-free hydrothermal synthesis is reported. By using these graphitic carbon nitride nanotubes an advanced electrochemical sensor was demonstrated to selectively sense explosive 2,4-dinitrotoluene. It is demonstrated that bigger linear range towards 2,4-dinitrotoluene, sensing up to 425 μM is reported. Furthermore, the experiments demonstrated that this sensor possesses a high sensitivity not only for 2,4-dinitrotoluene but also for other nitroaromatic explosives.

A High-Performance Supercapacitor Based on Hierarchical Template-Free Ni/SnO2 Nanostructures via Hydrothermal Method.

Novel flake-like Ni1-xSnxO2 particles were successfully prepared by template-free hydrothermal synthesis. The prepared samples were investigated for their properties by different characterization techniques. Scanning micrographs showed that the obtained particles consisted of nanoflakes. The X-ray diffraction results of the Ni1-xSnxO2 revealed the formation of mixed-phase Ni/SnO2 having the typical tetragonal structure of SnO2, and the cubic structure of Ni in a nanocrystalline nature. The doping with Ni had a certain influence on the host's lattice structure of SnO2 at different doping concentrations. Confirmation of the functional groups and the elements in the nanomaterials was accomplished using FTIR and EDS analyses. The electrochemical performance analysis of the prepared nanomaterials were carried out with the help of the CV, GCD, and EIS techniques. The specific capacitance of the synthesized nanomaterials with different concentrations of Ni dopant in SnO2 was analyzed at different scanning rates. Interestingly, a 5% Ni-doped SnO2 nanocomposite exhibited a maximum specific capacitance of 841.85 F g-1 at 5 mV s-1 in a 6 M KOH electrolyte. Further, to boost the electrochemical performance, a redox additive electrolyte was utilized, which exhibited a maximum specific capacitance of 2130.33 at 5 mV s-1 and an excellent capacitance retention of 93.22% after 10,000 GCD cycles. These excellent electrochemical characteristics suggest that the Ni/SnO2 nanocomposite could be utilized as an electrode material for high-performance supercapacitors.

Selectivity of Control of Oxygen Reduction Reaction over Mesoporous Transition Metal Oxides Catalysts for Electrified Purification Technologies

Introduction: The use of abundant feedstocks, such as water and air, in manufacturing of value-added products is important in achieving the UN’s Sustainable Development Goals.1 In this context, electrified direct synthesis of chemicals from oxygen in the air is of special interest since it avoids greenhouse gas emissions if the electricity used to drive the synthesis comes from sustainable sources such as solar- and wind-power. The controlling of oxygen reduction path over catalysts incorporation with oxygen evolution reaction as auxiliary reaction enables the electrosynthesis of value-added chemicals, oxygen and hydroxyl radical. The development of cheap materials e.g., mesoporous transition metal oxides, is urged to replace the expensive and scarce of platinum group metal (PGM)-based catalysts, with the ability to provide competitive reaction rate in alkaline media.2 Experimental: A template-free hydrothermal method is developed for the synthesis of mesoporous NiO and NiCo2O4. The materials’ physicochemical properties are characterized by X-ray diffraction, physisorption, electron microscopy, selected electron area diffraction, and X-ray photoelectron spectroscopy. The electrochemical properties and electrocatalytic oxygen activity are evaluated via cyclic voltammetry and electrochemical impedance spectra in alkaline electrolyte using a standard three electrodes electrochemical working station equipped with (ring) rotating disk electrode (RDE/RRDE) techniques.The catalysts coated on carbon fiber paper (CFP) are used as electrode assembled with anion exchange membrane in two-electrodes-electrochemical cell for device test. NiO- and NiCo2O4-modified CFP are used as cathode and anode, respectively, for constructing electrochemical generator of hydroxyl radical. 50 mL min-1 O2 flow was maintained in catholyte to enable oxygen saturation. 20 mg L-1 rhodamine B (RhB)was fed into cathode. Off-line UV-vis measurements were used for RhB quantification. In Electrochemical oxygen purifier, NiCo2O4-modified CFP are used as electrodes. 0.1 - 3 M KOH aqueous solutions were used as anolyte and air-saturated catholyte. The volume of produced oxygen on the anode after 2 h was collected and measured by a water displacement method. Results and Discussion: A facile template-free hydrothermal synthesis is developed for bifunctional oxygen electrocatalysts (OER and ORR) of NiO and NiCo2O4. Physicochemical characterization shows that both NiO and NiCo2O4 are mesoporous with the pore size within a range of 2 - 8 nm and specific surface areas of 60 and 120 m2 g-1, respectively. In addition, NiO and NiCo2O4 possess cubic crystal structures with the corresponding crystal sizes of ~6.0 and 9.3 nm.Electrochemical analysis shows that mesoporous NiCo2O4 has about two times larger capacitance and eight times smaller charge transfer resistance compared to NiO. NiCo2O4 shows higher electrocatalytic activity in OER and selectivity to water as the terminal product of ORR. On the contrary, ORR over NiO yielded hydroxyl radicals, as a product of a Fenton-like reaction of H2O2. The product selectivity in ORR is used to construct two electrolyzers of electrified purification of oxygen and generation of hydroxyl radicals. The optimization of configuration of hydroxyl radical generator enables the degradation of RhB up to 90% after 1 hour, and the electrochemical oxygen purifier shows high efficiency of about 100%. Significance: It is demonstrated that the synthesized mesoporous transition metal oxides via a simple template-free hydrothermal route, and the materials can be used as alternatives to PGM-based electrocatalysts for driving electrochemical cell towards to various products. The work also clearly shows how the composition and structure of catalysts affect the oxygen reactions, and the selectivity of ORR used for producing value-added chemicals coupling with OER. It is shown that the established electrochemical oxygen purifier and hydroxyl radical generator have a high conversion efficiency. Schematic 1. (a) Scheme of operation of the hydroxyl radical generator, (b) the degradation efficiency and rate constants as function of current densities; (c) Scheme of the oxygen purifier, and (d) the generated oxygen volume as a function of working power of the electrochemical cell with different anolyte concentrations. Acknowledgements: This work was supported by the competence center FunMat-II funded by the Swedish Agency for Innovation Systems (Vinnova, grant no 2016-05156), the Swedish Energy Agency (project no 42022-1), and Swedish Research Council (VR 2019-05577, Flexible metal-air primary batteries). Reference: 1 United Nations. Transforming our world: The 2030 agenda for sustainable developement. (UN General Assembly, New York, 2015).2 Yang, Y. et al. Electrocatalysis in Alkaline Media and Alkaline Membrane-Based Energy Technologies. Chem. Rev. 6, 6117–6321 (2022). Figure 1

Selectivity Control of Oxygen Reduction Reaction over Mesoporous Transition Metal Oxide Catalysts for Electrified Purification Technologies

Direct electrification of oxygen-associated reactions contributes to large-scale electrical storage and the launch of the green hydrogen economy. The design of the involved catalysts can mitigate the electrical energy losses and improve the control of the reaction products. We evaluate the effect of the interface composition of electrocatalysts on the efficiency and productivity of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), both mechanistically and at device levels. The ORR and OER were benchmarked on mesoporous nickel(II) oxide and nickel cobaltite (NiO and NiCo2O4, respectively) obtained by a facile template-free hydrothermal synthesis. Physicochemical characterization showed that both NiO and NiCo2O4 are mesoporous and have a cubic crystal structure with abundant surface hydroxyl species. NiCo2O4 showed higher electrocatalytic activity in OER and selectivity to water as the terminal product of ORR. On the contrary, ORR over NiO yielded hydroxyl radicals as products of a Fenton-like reaction of H2O2. The product selectivity in ORR was used to construct two electrolyzers for electrified purification of oxygen and generation of hydroxyl radicals.

Facile Synthesis of Organic Template-Free Chabazite Zeolite-Coated Kaolin Ceramic Membrane for Continuous Separation of Cerium from Aqueous Solutions

Developing an organic template-free zeolite coated on a low-cost ceramic support is essential to reduce the overall cost of the membrane for heavy metal separation. In this study, a low-cost and highly durable kaolin-supported zeolite-coated composite membrane was fabricated and tested for removal of cerium metal ions from its aqueous solution. Different strategies were followed to fabricate the composite membrane through the organic template-free hydrothermal synthesis method, such as coating the ceramic tubes solely on the interior surface, exterior surface, and both sides. The results obtained from X-ray diffraction, field emission scanning electron microscopy, and field emission transmission electron microscopy indicated that the hydrothermal synthesis route produced pure, ultrafine, and uniform particles of chabazite zeolite with a cation exchange capacity of 3.96 meq/g. The effect of coating on the membrane surface(s) was investigated by measuring the weight increment, porosity, pore size, and pure water permeability; the results revealed that the ceramic tube coated on both sides has the highest amount of zeolite loading, that is, 1.82 ± 0.18 g, along with a porosity of 30.50 ± 0.50%, a water permeability of 1.74 L/m2 h bar, and an average pore diameter of 36 nm. The average pore diameter of the composite membrane (both-side-coated tubes) obtained from BET analysis (34 nm) was in good agreement with the pore size (36 nm) estimated through the pure water permeability test. Furthermore, the performance of the composite membrane coated on both sides was evaluated toward removing cerium ions from aqueous solutions. The effect of applied pressure, pH, and concentration of the feed solution was investigated. During the cross-flow filtration tests, the permeate flux decline was not observed for all the applied pressures. More than 99.9% removal of cerium was achieved under the different conditions of feed concentration and pH. This study establishes the application of the prepared composite membrane for cerium removal from aqueous solutions.

Fluorine substituted hydroxyapatite microspheres: Template-free hydrothermal synthesis and sustained fluoride-releasing properties

To avoid sudden release of fluoride, F-substituted hydroxyapatite (FHA) porous microspheres were prepared for the treatment of F-deficiency tissues. In the absence of any template-directing reagents, FHA microspheres with diameters of about 30 ?m were successfully fabricated via hydrothermal method with urea as homogeneous precipitant to regulate the nucleation, growth and self-assembly process. Urea concentration and hydrothermal temperature played an important role in the formation and regulation of spherical hydroxyapatite. The synthesized FHA microspheres with large specific surface area, large pore volume and complex porous structure were efficient for the adsorption and long-term stable release of ionic extracts. Concentration of F- ions in physiological salt solution was maintained in the range of the therapeutic window without exceeding the toxic threshold within 30 days. The ionic extracts of FHA porous microspheres promoted the proliferation of human osteoblast-like cells (MG-63). The fabricated FHA microspheres may be a potential candidate as bioactive fluoride-release carriers for the treatment of osteoporosis and bone defects.

Template-free hydrothermal synthesis of nickel sulfide nanocrystals on MWCNTs: efficient and stable bifunctional electroactive material for oxygen electrocatalysis

Efficient and low-cost bifunctional electrocatalyst for oxygen electrocatalysis is developed using nickel sulfide and multi-walled carbon nanotubes.

Template-free hydrothermal synthesis of δ-MnO2 hierarchical nanoflowers with potassium ions intercalation as cathodes for high-performing aqueous zinc ion batteries

δ-MnO2 (K0.44Mn2O4·1.5H2O) hierarchical nanoflowers self-assembled with nanosheets were synthesized via a template-free hydrothermal route by using a mixture suspension of KMnO4 and MnSO4·H2O as precursors. The primary δ-MnO2 nanosheets spread along (001) plane with a thickness of ca. 2–5 nm. It is argued that the intercalations of K+ ions and water molecules among the interlayers of MnO6 octahedrons make the layered lattice structure of δ-MnO2 much stable, resulting in the δ-MnO2 hierarchical nanoflowers. The enlarged interlayer spacings effectively activate the storage of Zn2+ ions in the δ-MnO2 hierarchical nanoflowers. As cathodes for aqueous zinc ion batteries, thus, the δ-MnO2 hierarchical nanoflowers exhibit excellent electrochemical performances. The Zn//δ-MnO2 battery can deliver a high specific capacity of 293.6 mAh/g at a current density of 0.3 A/g and still maintains 217.8 mAh/g after 100 cycles. Besides, a high rate capacity of 84.6 mAh/g can be achieved at 3 A/g. It is believed that but for the promotion of Zn2+ ions diffusion by expanding interlayer spacings, the high specific area and mesoporous structure of the hierarchical architecture of the δ-MnO2 nanoflowers strongly improve the electrochemical performances through fully contacting with the electrolytes.

Template-free hydrothermal synthesis of hollow alumina microspheres and its excellent catalytic properties for thiolation

In view of the important industrial application value of alumina supports in the field of oil refining and reforming, it is of great significance to develop a simple and economical synthesis method for the hierarchical porous alumina. Herein, the hollow microsphere alumina was hydrothermally synthesized without template. The surface of the hollow microsphere alumina supports has a raised fluffy structure, the microsphere diameter is about 5 ∼ 8 μm, and the thickness of the shell is about 1 μm. The morphology evolution process from solid microspheres to core–shell microspheres with spindle-shaped nanoclusters, and then to hollow fluffy microspheres with protruding surface was observed by investigating the effect of hydrothermal synthesis temperature on the morphology of microspheres. Because of its specific morphology and surface characteristics, the microsphere can better disperse the active component KW to prepare KW/Al2O3 catalyst and used in the thiolation to methyl mercaptan. Compared with our previously used catalysts prepared from commercial alumina, this KW/Al2O3 catalyst was not only able to greatly reduce the amount of active component, but also exhibited higher CH3SH selectivity. On the 10KW/Al catalyst, the CH3SH selectivity reached 66.2 % at 340 °C, which was about 10 % higher than that of the previous commercial alumina catalyst. This work can provide theoretical basis and practical guidance for the reasonable design of new alumina support and high efficiency methyl mercaptan catalyst.

Prussian Blue Nanozyme Normalizes Microenvironment to Delay Osteoporosis.

Osteoporosis (OP) is the most common orthopedic disease in the elderly and the main cause of age-related mortality and disability. However, no satisfactory intervention is currently available in clinical practice. Thus, an effective therapy to prevent or delay the development of OP should be devised. Osteoclastogenesis overactivation and excessive bone resorption are the main characteristics of OP. Accordingly, a paradigm for nanozyme-mediated normalization of the disease microenvironment to regulate osteoclast differentiation and delay OP is proposed. Hollow Prussian blue nanozymes (HPBZs) are prepared via template-free hydrothermal synthesis and selected as representative nanozymes. The intrinsic osteoclast activity-remodeling bioactivities of the HPBZs are explored in vitro and in vivo, focusing on their impact on osteogenesis and specific molecular mechanisms using an OP murine model. The HPBZs significantly normalize the OP microenvironment, thereby inhibiting osteoclast formation and osteoclast resorption, possibly owing to the suppression of intracellular reactive oxygen species generation, the mitogen-activated protein kinase, and nuclear factor κB signaling pathways. Consistently, in an ovariectomy-induced OP murine model, HPBZ treatment significantly attenuates osteoporotic bone loss in vivo. The findings confirm the HPBZ-mediated normalization of the disease microenvironment for the treatment of OP and suggest its application to other inflammation-related diseases.

Oxidation-Induced and Hydrothermal-Assisted Template-Free Synthesis of Mesoporous CeO2 for Adsorption of Acid Orange 7.

Hydrogen peroxide (H2O2), an accessible and eco-friendly oxidant, was employed for the template-free hydrothermal synthesis of mesoporous CeO2 based on a cerium carbonate precursor (Ce2(CO3)3•xH2O). Its microstructure and physicochemical properties were characterized by XRD, TEM and N2 sorption techniques. The formation of the CeO2 phase with a porous structure was strongly dependent on the presence of H2O2, while the values of the BET surface area, pore diameter and pore volume of CeO2 were generally related to the amount of H2O2 in the template-free hydrothermal synthesis. The BET surface area and pore volume of the mesoporous CeO2 synthesized hydrothermally at 180 °C with 10 mL H2O2 were 112.8 m2/g and 0.1436 cm3/g, respectively. The adsorption process had basically finished within 30 min, and the maximum adsorption efficiency within 30 min was 99.8% for the mesoporous CeO2 synthesized hydrothermally at 140 °C with 10 mL, when the initial AO7 concentration was 120 mg/L without pH preadjustment. The experimental data of AO7 adsorption were analyzed using the Langmuir and Freundlich isotherm modes. Moreover, the mesoporous CeO2 synthesized at 140 °C with 10 mL H2O2 was regenerated in successive adsorption–desorption cycles eight times without significant loss in adsorption capacity, suggesting that the as-synthesized mesoporous CeO2 in this work was suitable as an adsorbent for the efficient adsorption of AO7 dye from an aqueous solution.

Excellent nitroarene reduction activity of ilmenite nanochips prepared by facile template-free hydrothermal synthesis

Aiming at demonstrating the highly-efficient catalytic reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP), we synthesized the ilmenite (FeTiO3) nanochips by using the facile template-free hydrothermal growth technique, and characterized their material properties and catalytic reduction activities. To investigate the effects of the hydrothermal reaction temperatures on the morphological, textural, and 4-NP reduction characteristics, the rhombohedral FeTiO3 nanochips were prepared at three different temperatures of 120, 150, and 180 °C. Among them, the FeTiO3 nanochips prepared at 180 °C displayed to possess more homogeneous distributions in their morphological shape and average size, compared to those of other samples. Furthermore, the high porosity (i.e., specific surface area: 95.3 m2/g, total pore volume: 0.1275 cm3/g) and the high charge transfer activity (Fe2+ + Ti4+ → Fe3+ + Ti3+) of the 180 °C-synthesized FeTiO3 nanochips enabled us to demonstrate the excellent 4-NP–to–4-AP reduction performances with a high reduction rate (∼91%) for a short reduction time (6 min). The results advocate that the FeTiO3 nanochips can be effectively utilized as a 4-NP reduction catalyst for future environmental technology.

Template-free hydrothermal synthesis of lithium iron tavorite with complex morphologies driven by phase transformation

Materials science is increasingly relying on sustainable methods for the synthesis of advanced materials. This work demonstrates the first template-free approach for the crystallization of tavorite, LiFePO4(OH), in the form of hollow microspheres and unique core (single crystal)–shell (aggregated particles) cross-like dendrites. The different morphologies have been obtained by hydrothermal synthesis. The kinetic pathways of crystallization reveal how the transformation of two different thermodynamically unstable phases, such as giniite (Fe5(PO4)4(OH)2⋅2H2O) and lithium sulfate (Li2SO4), leads to the same tavorite structure, but with different morphologies based on the different mechanisms for crystal growth. Additionally, we provide standardized powder X-ray diffraction data and insights into the influence of the iron precursor on the crystal morphology of tavorite.

Rubik’s cube shaped organic template free hydrothermal synthesis and characterization of zeolite NaA for CO2 adsorption

Here in this work a simple and direct method to synthesize Rubik’s cube-like Linda Type (LTA) zeolite NaA structure is reported. Linda Type (LTA) zeolite was synthesized by hydrothermal method without using any organic template additives. The molar ratio of 3.165Na2O:Al2O3:1.926SiO2:128H2O have been used to prepare the zeolite NaA hydrogel. The thermal stability of the synthesized zeolite NaA was studied through the thermogravimetric analysis (TGA). The results of X-ray diffraction (XRD) analysis showed that the crystallinity of the synthesized zeolite is good and the material is of high purity. Through the FTIR study, functional groups belonging to the zeolite NaA was confirmed. From the FESEM analysis, morphology of the synthesized sample was found to be Rubik’s cube-like structure. The elemental composition of the material was studied using the EDAX analysis and the ratio of Si:Al was found to be ∼ 1. Further from the SAED patterns of the prepared sample, it was observed that the material is polycrystalline in nature. From the nitrogen adsorption/desorption results the zeolite NaA samples was found to be mesoporous in nature. The pore size of the samples have been obtained using the Barrett-Joyner-Halenda (BJH) analysis. The CO2 adsorption isotherm study was carried out at 298 K and the isotherm was fitted by using Langmuir and Freundlich adsorption isotherm.

Phase stabilization and exposed {1 0 0} facet growth of α-Ag3VO4 photocatalyst: A low-temperature, template-free hydrothermal synthesis approach

The low-temperature phase stabilization, exposed {100} facet growth and solar light photocatalytic activity of α-Ag3VO4 microcrystals synthesized by a template-free hydrothermal procedure from AgNO3, NH4VO3 and ammonia were reported. By simply selecting a stoichiometric AgNO3/NH4VO3 molar ratio and a suitable amount of ammonia, pure α-Ag3VO4 powders were received readily at temperature as low as 100 °C while the competitive phase formation of the less photoactive Ag4V2O7 was inhibited completely. Especially, by increasing hydrothermal temperature from 100 to 160 °C, the crystallographic orientation growth of α-Ag3VO4 microcrystals along a-axis occurred and gradually diminished. For optimized sample, α-Ag3VO4 microcrystals were enclosed by exposed {100} facets, providing a significant enhancement in photocatalytic activity for methyl orange photodegradation under simulated solar light irradiation with respect to that of the random-oriented bulk sample. The role of ammonia on the low-temperature phase stabilization and exposed {100} facet growth of Ag3VO4 was also discussed.

Channeling carbon dioxide

Gas Separation The separation of gas molecules with physisorbents can be challenging because there is often a tradeoff between capacity and selectivity. Zhou et al. report a template-free hydrothermal synthesis of the one-dimensional channel zeolite mordenite, in which some silicon was replaced by iron. Rather than forming a powder that requires further shaping, this mechanically stable material self-assembled into monoliths. Iron atoms bound in tetrahedral zeolite sites narrowed the channels and enabled the size-exclusion separation of carbon dioxide (CO2) over nitrogen (N2) and methane. High CO2 uptake and highly efficient CO2–N2 separation was demonstrated for both dry and humid conditions. Science , aax5776, this issue p. [315][1] [1]: /lookup/doi/10.1126/science.aax5776

Self-assembled iron-containing mordenite monolith for carbon dioxide sieving.

The development of low-cost, efficient physisorbents is essential for gas adsorption and separation; however, the intrinsic tradeoff between capacity and selectivity, as well as the unavoidable shaping procedures of conventional powder sorbents, greatly limits their practical separation efficiency. Herein, an exceedingly stable iron-containing mordenite zeolite monolith with a pore system of precisely narrowed microchannels was self-assembled using a one-pot template- and binder-free process. Iron-containing mordenite monoliths that could be used directly for industrial application afforded record-high volumetric carbon dioxide uptakes (293 and 219 cubic centimeters of carbon dioxide per cubic centimeter of material at 273 and 298 K, respectively, at 1 bar pressure); excellent size-exclusive molecular sieving of carbon dioxide over argon, nitrogen, and methane; stable recyclability; and good moisture resistance capability. Column breakthrough experiments and process simulation further visualized the high separation efficiency.

Template-free microwave-assisted hydrothermal synthesis of manganese zinc ferrite as a nanofertilizer for squash plant (Cucurbita pepo L)

Manganese, zinc, and iron are the most essential micronutrients required for plant growth and applied as foliar fertilizers. Herein, a simple template-free microwave-assisted hydrothermal green synthesis technique was adapted to produce manganese zinc ferrite nanoparticles (Mn0.5Zn0.5Fe2O4 NPs) at different temperatures (100, 120, 140, 160 and 180 °C). The prepared nanomaterials were employed at different concentrations (0, 10, 20, and 30 ppm) as foliar nanofertilizers during the squash (Cucurbita pepo L) planting process. X-ray diffraction patterns of the prepared nanomaterials confirmed successful production of the nanoferrite material. The prepared nanofertilizers showed type IV adsorption isotherm characteristic for mesoporous materials. FE-SEM and HR-TEM imaging showed that the nanoparticles were cubic shaped and increased in particle size with the increase in microwave temperature during production. The impact of application of the synthesized ferrite nanoparticles on vegetative growth, proximate analysis, minerals content and the yield of squash plant was investigated for two consecutive successful planting seasons. The nanoferrite synthesized at 160 °C and applied to the growing plants at a concentration of 10 ppm gave the highest increase in % yield (49.3 and 52.9%) compared to the untreated squash for the two consecutive seasons, whereas the maximum organic matter content (73.0 and 72.5%) and total energy (260 and 258.3 kcal/g) in squash leaves were obtained in plants treated with 30 ppm ferrite nanoparticles synthesized at 180 °C. On the other hand, the maximum organic matter content (76.6 and 76.3%) and total energy (253.6 and 250.3 kcal/g) in squash fruits were attained with plants supplied by 20 ppm ferrite nanoparticles synthesized at 160 °C. These results indicate that the simple template-free microwave-assisted hydrothermal green synthesis technique for the production of manganese zinc ferrite nanoparticles yields nanoparticles appropriate for use as fertilizer for Cucurbita pepo L.

Rectifying resistance switching behaviors of SnO2 microsphere films modulated by top electrodes

Based on the bipolar resistive switching (RS) characteristics of SnO2 films, we have fabricated a new prototypical device with sandwiched structure of Metal/SnO2/fluorine-doped tin oxide (FTO). The SnO2 microspheres film was grown on FTO glass by template-free hydrothermal synthesis, which was evaporated with various commonly used electrodes such as aluminium (Al), silver (Ag), and gold (Au), respectively. Typical self-rectifying resistance switching behaviors were observed for the RS devices with Al and Au electrodes. However, no obvious rectifying resistance switching behavior was observed for the RS device with Ag electrode. Above results were interpreted by considering the different interface barriers between SnO2 and top metal electrodes. Our current studies pave the ways for modulating the self-rectifying resistance switching properties of resistive memory devices by choosing suitable metal electrodes.

Synthesis and photoelectrochemical water oxidation of (Y, Cu) codoped α-Fe2O3 nanostructure photoanode

Hematite (α-Fe2O3) is one of the best capable photoanode material for water oxidation under visible light. The role of synergetic effect between two metal dopants for enhanced water oxidation is not adequately studied. The mono-doping (Y) and co-doping (Cu, Y) effect on the crystal structure, morphology, optical properties and their influence as photoanodes for energy harvesting applications are systematically explored. In this study, we have synthesized the pure, mono-doped (Y), and co-doped (Y and Cu) hematite nanostructures for enhanced photoelectrochemical (PEC) performance using a simple template free hydrothermal synthesis technique. The optimized photoelectrode showed a substantial improvement (∼36-times) in the PEC photocurrent density over pristine, mono-doped and co-doped photoanodes. Electrochemical impedance spectroscopy analysis confirmed that the co-dopant enhanced the charge carrier density of hematite and it acts as an electron donor. Moreover, it is demonstrated that the photocurrent density increases after mono-doping from 0.012 mAcm−2 to 0.020 mAcm−2 and further improved to 0.439 mAcm−2 with co-dopant at 1.23 V vs. RHE. The considerably enhanced PEC activity is ascribed to the higher conductivity, enhanced interfacial charge transfer at the surface of hematite and the synergistic effect between two metal dopants.