Metal Ion Precursors Research Articles

Fabrication of Homochiral Metal-Organic Frameworks in TiO2 Nanochannels for In Situ Identification of 3,4-Dihydroxyphenylalanine Enantiomers.

Enantioselective identification of chiral molecules is important for biomedical and pharmaceutical research. However, owing to identical molecular formulas and chemical properties of enantiomers, signal transduction and amplification are still the two major challenges in chiral sensing. In this study, we developed an enantioselective membrane by integrating homochiral metal-organic frameworks (MOFs) with nanochannels for the sensitive identification and quantification of chiral compounds. The membrane was designed using a TiO2 nanochannel membrane (TiNM) as the metal ion precursor of MOFs (using MIL-125(Ti)) and incorporating l-glutamine (l-Glu) into the framework of MIL-125(Ti). Using 3,4-dihydroxyphenylalanine (DOPA) as the model analyte, the as-prepared homochiral l-Glu/MIL-125(Ti)/TiNM exhibits a remarkable chiral recognition to d-DOPA than l-DOPA. More importantly, benefiting from the highly enlarged surface area and confinement effect provided by the MOFs-in-nanochannel architecture, the discrimination for chiral recognition is largely amplified through the chelation interaction of Fenton-like activity of Fe3+ onto DOPA. Using 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) as the substrate, the positively charged ABTS•+ product via Fenton-like reaction induces significant ionic transport changes in nanochannels, which in turn provides information about chiral recognition. This innovative signal amplification strategy on homochiral nanochannels might pave a new way for sensitive monitoring and chiral recognition.

Composite Zn(II) Ferrocyanide/Polyethylenimine Cryogels for Point-of-Use Selective Removal of Cs-137 Radionuclides.

The feasibility of several approaches to the fabrication of monolith composite cryogels containing transition-metal ferrocyanides for Cs+ ion uptake has been evaluated. Although in the series of investigated metal ion precursors (Cu(II), Zn(II), Ni(II), and Co(II)), in situ formation of the sorption active phase in polyethyleneimine (PEI) cryogel was feasible only in the case of Zn(II) ferrocyanide, this approach has shown significant advantages over the immobilization of ex situ synthesized ferrocyanide nanoparticles. Nanoparticles of the mixed ferrocyanide Zn1.85K0.33[Fe(CN)6] formed in situ had an average size of 516 ± 146 nm and were homogeneously distributed in the monolith located at the polymer surface rather than embedded in the matrix. The Young modulus of the PEI cryogel increased after modification from 25 to 57 kPa, but composites maintained high permeability to the flow. Sorption of Cs+ ions has been investigated at superficial velocity up to 8 m/h. Steep breakthrough profiles and uptake efficiency of >99.5% until breakthrough point confirmed that a supermacroporous structure of the monolith composite assured good mass transfer, so that intraparticle diffusion was not the limiting stage of sorption kinetics. Application of the rate-constant distribution model (RCD model) to analyze the breakthrough curves of Cs+ sorption allowed the identification of two types of sorption sites with a difference in sorption rate constants of ~1 log unit. Most likely, sorption on “fast” sorption sites was governed by ion exchange between Cs+ ions in solution and K+ ions in the ferrocyanide lattice. Cs-137 radionuclide removal was investigated using the monolith composite columns of various geometries at superficial velocity up to the 6.6 m/h; specific gamma activity was reduced from 265 kBq/L to the background level, showing high potential of these materials for POU application.

In Situ Biosynthesis of a Metal Nanoparticle Encapsulated in Alginate Gel for Imageable Drug-Delivery System.

Development of drug-delivery systems that allow simultaneous in vivo imaging has gained much interest. We report a novel strategy to encapsulate metal nanoparticles (NPs) within alginate gel for in vivo imaging. The cell lysate of recombinant Escherichia coli strain, expressing Arabidopsis thaliana phytochelatin synthase and Pseudomonas putida metallothionein genes, was encapsulated within the alginate gel. Incubation of alginate gel with metal ion precursors followed by UV irradiation resulted in the synthesis of high concentrations of metal NPs, such as Au, Ag, CdSe, and EuSe NPs, within the gel. The alginate gel with metal NPs was used as a drug-delivery system by further co-encapsulating doxorubicin and rifampicin, the release of which was made to be pH-dependent. This system can be conveniently and safely used for in vitro and in vivo bioimaging, enabled by the metal NPs formed within the gel matrix without using toxic reducing reagents or surfactants.

Hollow Silica Nanotubes for Space-Confined Synthesis of Noble Metal Nanorods and Nanopeapods

Realizing precise control over the size and functionality of nanomaterials is a prerequisite to their diverse applications in the areas of biology, environment, energy, and other emerging nanotechnologies. Herein, we demonstrate a general template strategy capable of fabricating functional noble metallic nanorods and nanopeapods. The templates are hollow silica nanotubes (HSNTs) produced from unimolecular micelles of bottlebrush copolymers. The variation of chain length and chemical composition of bottlebrush copolymers achieved through the reversible-deactivation radical polymerization dictates the length (L), inner diameter (D), and thickness (h) of HSNTs. Using such HSNTs as nanoreactors enables the fabrication of noble metals such as Au, Ag, and Pt nanorods or nanopeapods with silica shells in a space-confined manner. While the thickness and the interior space of HSNTs regulate the diffusion and intake of metal ion precursors, the formation of nanorods or nanopeapods with different lengths and diameters is well controlled. Upon etching out the silica shell, the resulting metallic nanorods are readily functionalized with polymeric ligands for excellent dispersity in aqueous and/or organic media. This feasible and versatile strategy represents a great leap forward in the controlled synthesis of one-dimensional metallic nanomaterials and hopefully promotes understanding their structure-determined physiochemical properties and board applications in medicine and catalysis.

SINTESIS DAN TRANSISI ELEKTRONIK KOMPLEKS TEMBAGA (II)-KLOROFIL

The copper (II)-chlorophyll complex was prepared from the reaction between the chlorophyll isolated from cassava leaves and the metal ion precursor, CuSO4.5H2O in methanol under reflux for four hours. The FTIR spectra of the reaction product compared to the chlorophyll spectra show an indication of a complexation through metal coordination with the N atom from the phyrol ring replacing the magnesium (II) ion in chlorophyll.This assumption is drawn based on changes on FTIR spectra, i.e. vibration absorption originating from the CN and NH groups in the porphyrin ring and the appearance of the distinctive vibration band of nitrogen-metal bonds which is annotated as Cu-N groups at 599.88 cm-1. Another sign is the change in the OH and CO vibration bands which imply changes in aggregate properties that occur through inter-molecular interactions due to the introduction of copper (II) metal into the chlorophyll structure. The formation of copper (II)-chlorophyll compounds is also shown from the results of atomic absorption spectroscopy by recording copper metal in the product and reducing magnesium metal concentration. UV-vis spectra of chlorophyll in methanol show a characteristic band in the dark area (Soret band) at a maximum wavelength of 404 nm and the visible area (Q band) with the strongest intensity at 665 nm. These peaks appear to shift hypsochromically in the copper (II)-chlorophyll compound to 397 nm and 650 nm with higher absorptivity, indicating a change in the electronic transition of the chlorophyll after coordinating with the copper (II) ion. A new peak at 411 nm was also observed which is suggested to indicate that the copper (II) -chlorophyll complex is in an octahedral geometry in the aggregate coordinated via nitrogen atoms in the phyrol ring in place of the magnesium (II) ion.

One step low temperature synthesis of poly vinyl alcohol stabilised a-Ni (OH)2 nanoparticles structural, morphological and optical studies

This research work reports a facile procedure for preparing α-nickel hydroxide nanoparticles. Synthesis of α-Ni(OH)2 nanoparticles was performed at low temperature using poly vinyl alcohol (PVOH) as a stabilising agent. The structure of the nanoparticles was studied using X-ray diffractograms (JCPDS card 22-0444) and Fourier transform infrared (FTIR) analysis. The peaks corresponding to 459 cm−1 and 409 cm−1 in FTIR revealed the actual structure of α-Ni(OH)2. The size of the α-Ni(OH)2 nanoparticles was computed using Scherrer's formula. The estimated size was 4 nm. The HRTEM micrograph of nano-sized α-Ni(OH)2 revealed the formation of nanobristles with diameter of 2 nm. The nanobristles formed a 2D layer due to intercalation of PVOH with nickel hydroxide. The UV absorption spectrum further confirmed the nano size of α-Ni(OH)2. Optical band gap values (Eg) of Ni (OH)2 were determined for various precursor concentrations. The minimum value of band gap for α-Ni(OH)2 nano particles was found to be 2.12 eV for 3.5 g of metal ion precursor.

Investigation of electrodeposition kinetics of In, Sb, and Zn for advanced designing of InSb and ZnSb thin films

In this work, the kinetics of indium, antimony, and zinc electrodepositions were investigated by using a gold rotating disc electrode (RDE). The performed studies shed light on the influence of electrodeposition parameters (i.e., working electrode potential and hydrodynamic conditions) on the chemical composition of In-Sb and Zn-Sb films. Stoichiometric InSb and ZnSb are one of the most promising thermoelectric materials, therefore a strictly controlled chemical composition of deposits is required. During electrochemical studies, as a primary electrolyte, a citrate bath with the addition of metal ion precursors, i.e., 0.06 M InCl 3 and/or 0.045 M SbCl 3 and/or 0.045 M ZnCl 2 , was applied. Based on the linear voltammetry measurements in the RDE system, the Koutecký-Levich analyses were performed. The diffusion coefficients ( D ) determined at 293 K for indium, antimony, and zinc ions equal to 1.45 × 10 −6 , 3.76 × 10 −6 , and 5.94 × 10 −6 cm 2 s −1 , respectively. The activation energy ( E A ) for the diffusion of metal ions was determined using D values calculated at different temperatures. E A of indium, antimony, and zinc ions equals to 25.1, 9.2, and 10.6 kJ mol −1 , respectively. The number of transferred electrons ( n ) and rate constant for heterogeneous reactions ( k ) occurring in the studied electrolytes at different potentials were also determined. • Electrodeposition of In, Sb, and Zn is under diffusion and kinetics control. • Diffusion coefficient of ion increase in line: In-citrate<Sb-citrate<Zn-citrate. • Adsorption of citrate ions on the RDE surface slows down electroreduction of In. • Indium-citrate ions have the highest E A of diffusion among studied species.

Controlling Electronic Energy Structure of Ag–Ιn–Ga–S–Se Quantum Dots Showing Band-Edge Emission

Semiconductor quantum dots (QDs) exhibited unique optical properties owing to the confinement of charge carriers or excitons in all three dimensions, that is quantum confinement, and then have engaged considerable attention for possible wide-ranged applications, such as solar cells, photocatalysts, light-emitting devices, and biological imaging. The majority of published studies of QDs have focused on binary QDs containing highly toxic heavy metals such as CdS, CdSe, and PbS, due to their well-developed synthesis methods, though the presence of highly toxic elements (Pb or Cd) limits their practical utility in prospective real-life applications. Recently, group I-III-VI-based multinary QDs, such as ZnAgInS[1], AgInGaS[2], and AgInGaSe[3], have been an environmentally benign alternative to conventional binary QDs, with comparable physicochemical properties. We previously reported that a sharp PL peak assignable to band-edge emission was observed for AgInGaS QDs surface-coated with GaSx shell, the peak wavelength being blue-shifted from 610 to 500 nm by the increase in the content of Ga in QDs[2]. Since the bulk Eg of AgInGaSe is smaller than that of corresponding AgInGaS, the doping of Se into AgInGaS QDs can be another strategy to tune their Eg. In this study, we investigate the photochemical properties of Se-doped AgInGaS (AIGSSe) QDs, being dependent on the ratio of Se/S in the particles.AIGSSe QDs were synthesized by a solution-phase synthesis method. A mixture of AgOAc, In(acac)3, and Ga(acac)3 was used as a metal ion precursor, and that of thiourea and selenourea was used as a chalcogen precursor. These were added to a test tube with a mixture solvent of oleylamine and dodecanethiol, in which the ratio of Se/(S+Se) varied from 0 to 1.0. The solution was heated at 100~250 oC and then formed QDs were isolated by adding methanol. The resulting wet precipitated were washed several times with methanol, followed by dissolving in chloroform.Absorption spectra of thus-obtained AIGSSe QDs were red-shifted with an increase in the Se/(S+Se) ratio in preparation from 0 to 1.0, the onset wavelength being changed from 580 nm to 806 nm, respectively. The Eg value of the QDs could be controlled between 2.0 eV and 1.4 eV. Although the as-prepared AIGSSe QDs showed a weak broad PL peak assigned to defect-site emission, the surface coating with GaSx removed the broad PL peak and then enhanced the sharp band-edge emission peak. The PL peak wavelength was red-shifted with a decrease in the Eg of QDs. TEM analysis revealed that core-shell-structured AIGSSe@GaSx QDs had a spherical shape with an average size of 4 nm, which were slightly larger than that of AIGSSe QDs used as a core. Thus, we concluded that AIGSSe and AIGSSe@GaSx QDs were successfully prepared via solution-phase method and their Egs were controlled by tuning the ratio of Se/(S+Se) in the composition.

Biogenic-Mediated Synthesis of the Cs2O-MgO/MPC Nanocomposite for Biodiesel Production from Olive Oil.

In this work, a biogenic-mediated approach is successfully used to synthesize a novel heterogeneous Cs2O–MgO/MPC basic nanocomposite. For the first time, the established technicality employs pomegranate seed extract that gives a green capping fuel and reducing mediators during an aqueous solution combustion process of metal ion precursors. The synthesized nanocomposites were identified by X-ray diffraction, Fourier transform infrared, N2 isotherms, field emission scanning electron microscopy, and CO2-TPD analyses. The transesterification process of olive oil was used to evaluate the catalytic performance. The nanocomposite displayed outstanding catalytic efficiency stemming from the boosting of the reactant and product diffusion. The transesterification activity and the optimization design were assessed by applying the response surface methodology. Based on the experimental tests, the finest experimental conditions with a biodiesel yield of 96.1% are 4 h, 4% catalyst amount, an oil/methanol ratio of 1:15, and a temperature of 65 °C. The predicted optimal conditions based on the statistical model are 6 h contact time, 5.2 % catalyst dose, 65 °C reaction temperature, and 1:15 oil/methanol molar ratio, attaining a biodiesel yield of 95.18%. The catalyst reusability has been performed almost continuously up to four cycles, with no loss of the active constituents. The obtained biodiesel demonstrated characteristics close to those of international standards of biodiesel. Besides, the process employed in this study demonstrated significant potential for further development and commercialization and is cheaper than the refined vegetable oil used in traditional approaches of biodiesel manufacturing.

Strong electrostatic adsorption approach to the synthesis of sub-three nanometer intermetallic platinum–cobalt oxygen reduction catalysts

Low-platinum group metal (low-PGM) intermetallics are among the best materials as active and stable electrocatalysts for the oxygen reduction reaction (ORR) in polymer electrolyte membrane fuel cells (PEMFCs). The lack of control over the particle size and size distribution limits the use of thermal annealing method in the synthesis of carbon-supported low-PGM intermetallics because of the surface atomic diffusion at elevated temperatures. Herewith, we report the synthesis of sub-3 nm intermetallic PtCo ORR catalysts using a strong electrostatic adsorption (SEA) approach. The strong adhesion of metal ion precursors ensured to anchor the PtCo nanoparticles on the carbon support, thus suppressing the atomic migration and sintering during their conversions to intermetallic phases. The mass activity of the intermetallic PtCo catalyst was 0.67 A/mg Pt (at 0.9 V vs. RHE) which was more than double that of its alloyed counterpart. Most noticeably, the mass activity of this catalyst dropped by merely 3% of its initial value after the accelerated durability test of 10,000 cycles, in a strong acid condition. This study provides a useful strategy for preparing ultrafine low-PGM intermetallic nanocrystals for ORR and paves the way to use the SEA approach for making intermetallic ORR electrocatalysts using various metals and support materials. • A sub-3 nm intermetallic L1 0 -PtCo ORR catalyst was synthesized using a strong electrostatic adsorption (SEA) approach. • The acidity-dependent synthesis allows the control towards the size and dispersion of A1-PtCo nanoparticles on carbon. • Strong adhesion between PtCo nanoparticles and N-doped mesoporous carbon greatly suppresses the sintering at high temperatures. • The intermetallic L1 0 -PtCo/C electrocatalysts exhibit greatly improved activity and stability for ORR in acid conditions.

Stepwise Assembly of an Electroactive Framework from a Co6 S8 Superatomic Metalloligand and Cuprous Iodide Building Units.

The design of metal-organic frameworks (MOFs) that incorporate more than one metal cluster constituent is a challenging task. Conventional one-pot reaction protocols require judicious selection of ligand and metal ion precursors, yet remain unpredictable. Stable, preformed nanoclusters, with ligand shells that can undergo additional coordination-driven reactions, provide a platform for assembling multi-cluster solids with precision. Herein, a discrete Co6 S8 (PTA)6 (PTA=1,3,5-triaza-7-phosphaadamantane) superatomic-metalloligand is assembled into a three-dimensional (3D) coordination polymer comprising Cu4 I4 secondary building units (SBUs). The resulting heterobimetallic framework (1) contains two distinct cluster constituents and bifunctional PTA linkers. Solid-state diffuse reflectance studies reveal that 1 is an optical semiconductor with a band-gap of 1.59 eV. Framework-modified electrodes exhibit reversible redox behavior in the solid state arising from the Co6 S8 superatoms, which remain intact during framework synthesis.

Enhanced mechanical properties of boron nitride nanosheet/copper nanocomposites via a molecular-level mixing process

Boron nitride nanosheet/copper (BNNS/Cu) nanocomposites were fabricated using a molecular-level mixing process. This process was facilitated by electrostatic interactions between negatively charged functional groups on the BNNSs and Cu metal precursor ions. The mixing process induced the formation of oxygen (O)-mediated bonding between BNNSs and the Cu matrix, which enabled enhanced dispersion of BNNSs and interfacial bonding with the Cu matrix. The mechanical properties of the resulting nanocomposite material, including the yield strength, tensile strength, and modulus, were greatly improved with incorporation of only a small amount of BNNSs using the molecular-level mixing process. The strengthening effect of BNNSs was attributed to a combination of a small contribution from grain size refinement effect and a major contribution from load transfer effect. This extraordinary load transfer strengthening, supported by modeling, is attributed to O-mediated interfacial bonding between the BNNSs and Cu. High-resolution transmission electron microscopy revealed the formation of an amorphous interphase between the BNNSs and the Cu matrix. This O-rich phase may have contributed to the strengthening effect of the BNNSs. The BNNS/Cu nanocomposite showed excellent high-temperature mechanical properties. These superior mechanical properties of the nanocomposite material suggest applications in various structural materials, including those requiring exposure to high temperatures.

Enhancing Galvanic Replacement in Plasmonic Hollow Nanoparticles: Understanding the Role of the Speciation of Metal Ion Precursors

AbstractHollow nanostructures offer great potential for plasmonic applications due to their strong and highly tunable localized surface plasmon resonance. The relationship between the plasmonic properties and geometry of hollow nanoparticles, such as core‐shell size ratio, concentricity of the cavity and porosity of the wall, is well documented. Nanoscale galvanic replacement provides a simple, versatile and powerful route for the preparation of such hollow structures. Here we demonstrate how the efficiency of reductant‐assisted galvanic replacement processes can be enhanced by controlling the degree of hydration and hydrolysis of the metal ion precursor using pH and pL as key control parameters (by analogy to pH, the letter p in the expression pL is used to indicate the decimal cologarithm associated with the concentration of the ligand L). Adjusting precursor speciation prior to the sacrificial template's hollowing process offers a new strategy to tune the morphology and optical properties of plasmonic hollow nanostructures.

Development of a sequential extraction and speciation procedure for assessing the mobility and fractionation of metal nanoparticles in soils

This study describes the development of a sequential extraction procedure for the evaluation of metal nanoparticle mobility and bioaccessibility in soils. The procedure, that was developed using gold nanoparticles (AuNPs) as model species, relies on the fractionation of nanoparticles by sequentially dissolving soil matrix components (carbonates, metal oxides, organic matter and mineral phases) in order to release the entrapped nanoparticle species in the extract solution. By summing up the concentration of AuNPs recovered in each fraction it was found that 93.5% of the spiked AuNP concentration could be recovered which satisfactorily represents the nominal AuNP concentration in the soil. The efficiency of the procedure was found to depend on several procedural artifacts related to the separation of AuNPs from soil colloids and the reactivity of the extraction reagents with AuNPs and their precursor metal ions. Based on the results obtained a protocol for the speciation of the AuNPs and Au ions in the soil sample was also developed. The results of the study show that both AuNPs and Au ions are mainly associated with soil organic matter, which significantly reduces their mobility, while a small amount (<10%) is associated with metal oxides which are more mobile and potentially bioaccessible. The developed procedure provides a springboard for further development of sequential extraction procedures of metal nanoparticles in soils that could be used to assess both the exposure and release of metal nanoparticles and their precursor metal ions in the environment (as total extractable concentration) as well as provide evidence regarding their bioaccessibility and potential bioavailability by determining the concentration of nanoparticles in each specific soil fraction.

Layer-by-Layer Self-Assembly of Metal/Metal Oxide Superstructures: Self-Etching Enables Boosted Photoredox Catalysis.

The capability of noble metal nanoparticles (NPs) as efficient charge transfer mediators to stimulate Schottky-junction-triggered charge flow in multifarious photocatalysis has garnered enormous attention in the past decade. Nevertheless, fine-tuning and controllable fabrication of a directional charge transport channel in metal/semiconductor heterostructures via suitable interface engineering is poorly investigated. Here, we report the progressive fabrication of a tailor-made directional charge transfer channel in Pt nanoparticles (NPs)-inlaid WO3 (Pt-WO3) nanocomposites via an efficient electrostatic layer-by-layer (LbL) self-assembly integrated with a thermal reduction treatment, by which oppositely charged metal precursor ions and polyelectrolyte building blocks were intimately and alternately assembled on the WO3 nanorods (NRs) by substantial electrostatic interaction. LbL self-assembly buildup and in situ self-etching-induced structural variation of WO3 NRs to a microsized superstructure occur simultaneously. We found that such exquisitely crafted Pt-WO3 nanocomposites exhibit conspicuously enhanced and versatile photoactivities for nonselective mineralizing of organic dye pollution and reduction of heavy metal ions at ambient conditions under both visible and simulated sunlight irradiation, demonstrating a synergistic effect. This is attributed to the imperative contribution of Pt NPs as electron traps to accelerate the directional high-efficiency electron transport from WO3 to Pt NPs, surpassing the confinement of electron transfer kinetics of WO3 owing to low conduction level. More intriguingly, photoredox catalysis can also be triggered simultaneously in the same reaction system. The primary in situ produced active species in the photocatalytic reactions were specifically analyzed, and underlying photocatalytic mechanisms were determined. Our work would provide a universal synthesis strategy for constructing various metal-decorated semiconductor nanocomposites for widespread photocatalytic utilizations.

Metal-Organic Frameworks as Metal Ion Precursors for the Synthesis of Nanocomposites for Lithium-Ion Batteries.

Metal-organic frameworks (MOFs) are promising materials with fascinating properties. Their widespread applications are sometimes hindered by the intrinsic instability of frameworks. However, this instability of MOFs can also be exploited for useful purposes. Herein, we report the use of MOFs as metal ion precursors for constructing functional nanocomposites by utilizing the instability of MOFs. The heterogeneous growth process of nanostructures on substrates involves the release of metal ions, nucleation on substrates, and formation of a covering structure. Specifically, the synthesized CoS with carbon nanotubes as substrates display enhanced performance in a lithium-ion battery. Such strategy not only presents a new way for exploiting the instability of MOFs but also supplies a prospect for designing versatile functional nanocomposites.

Metal–Organic Frameworks as Metal Ion Precursors for the Synthesis of Nanocomposites for Lithium‐Ion Batteries

AbstractMetal–organic frameworks (MOFs) are promising materials with fascinating properties. Their widespread applications are sometimes hindered by the intrinsic instability of frameworks. However, this instability of MOFs can also be exploited for useful purposes. Herein, we report the use of MOFs as metal ion precursors for constructing functional nanocomposites by utilizing the instability of MOFs. The heterogeneous growth process of nanostructures on substrates involves the release of metal ions, nucleation on substrates, and formation of a covering structure. Specifically, the synthesized CoS with carbon nanotubes as substrates display enhanced performance in a lithium‐ion battery. Such strategy not only presents a new way for exploiting the instability of MOFs but also supplies a prospect for designing versatile functional nanocomposites.

Iron oxide and various metal oxide nanotubes engineered by one-pot double galvanic replacement based on reduction potential hierarchy of metal templates and ion precursors.

A one-pot double galvanic approach was explored for the rational synthesis of metal oxide nanotubes, predictable based on the reduction potential hierarchy of templates and ion precursors (e.g., Ag nanowire substrate is oxidized by MnO4− ions and it is consecutively reduced by Fe2+ ions to form an Fe2O3 nanotube). This method generated a variety of metal oxide nanotubes via a redox potential landscape.

Synthesis and Characterization of Strontium Cerium Mixed Oxide Nanoparticles Using Plant Extract

Green synthesis of nanomaterials is an emphasis of recent developments. Herein, a facile and eco-friendly method for the synthesis of SrO–CeO2 mixed oxide NPs using ionic liquid (IL) assisted an ethanolic solution of Pedalium murex (PM) plant extract. NPs synthesized at room temperature using an ionic liquid (IL) as a mediator for the nucleation and growth process. SrO–CeO2 mixed oxide NPs system displaying nano rod like structure with 10–15 nm and high surface area that are confirmed by XRD, and SEM studies. GC-MS spectroscopy confirms the presence of N-Hexadecanoic acid (29%), 6-Octadecenoic acid, (Z) present in the plant extract that are capable to convert the corresponding metal ion precursor to SrO–CeO2 mixed oxide NPs. In FTIR the Ce–O and SrCO3 stretching bands were observed at 451 and 856 cm–1 respectively. Raman spectroscopy give stretching frequency at 457 and 159 cm–1 that proofs the presence of CeO2 and SrO present in the mixed oxide. The band gap energy of the SrO–CeO2 mixed oxide NPs was estimated as 3.17 eV from the UV-DRS spectroscopy. The anti-bacterial studies performed against a set of bacterial strains the result showed that SrO–CeO2 mixed oxide NPs more susceptible for gram negative (G–) bacteria then gram positive (G+) bacteria. A unique feature of the antioxidant behavior of NPs reduces the concentration of DPPH radical up to 89%. The toxicology behavior of SrO–CeO2 mixed oxide NPs found due to the high oxygen site vacancies, ROS formation, smallest particle size and higher surface area.

Nanocomposites Based on Ruthenium Nanoparticles Supported on Cobalt and Nitrogen-Codoped Graphene Nanosheets as Bifunctional Catalysts for Electrochemical Water Splitting.

Rational design and engineering of high-efficiency electrocatalysts toward overall water splitting is crucial for the development of hydrogen energy technology. Herein, a facile procedure is described for the preparation of effective bifunctional electrocatalysts for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), where ruthenium nanoparticles are supported on graphene nanosheets that are codoped with atomic cobalt and nitrogen by controlled pyrolysis of melamine-functionalized graphene oxide and metal ion precursors. The obtained nanocomposites (CoNG/Ru) exhibit a remarkable electrocatalytic activity toward both HER and OER in alkaline media, with a respective overpotential of only -15 and +350 mV to reach the current density of 10 mA cm-2, which is much better than the monometallic counterparts and relevant catalysts in the literature. With CoNG/Ru as bifunctional catalysts for overall water splitting in a two-electrode system, a low potential of 1.58 V is needed to reach the current density of 10 mA cm-2, which is even better than that with commercial Pt/C and RuO2 catalysts. This is ascribed to the synergistic interactions between the metal species by metal-metal charge transfer. These results highlight the significance of exploiting the electronic interactions between metal species in carbon-based nanocomposites to develop bifunctional catalysts for electrochemical energy technologies.