Improved Suzuki–Miyaura reaction conversion efficiency using magnetic nanoparticles and inductive heating

Journal of Materials Science - The use of magnetic nanoparticles in C–C coupling reactions enables the facile recovery of the catalyst under environmentally friendly conditions. Herein, the...     

Polymer grafting onto magnetite nanoparticles by “click” reaction

In this article, we described click chemistry methodology for the incorporation of biocompatible polymer chains to Magnetite nanoparticles (NPs). We used a reduction co-precipitation method to obtain Fe₃O₄ particles in aqueous solution. As a next step, magnetic NPs surface were modified by a silanization reaction with (3-bromopropyl)trimethoxysilane in order to introduce bromine groups on the particles surface which were converted to azide groups by the reaction with sodium azide. Acetylene functionalized poly(ethylene glycol) (a-PEG) and poly(ε-caprolactone) (a-PCL) were synthesized and grafted onto the surface of azide functionalized NPs via “click” reaction to obtain magnetic NPs. Success of the different functionalization processes at different stages was studied using Fourier Transform infrared spectroscopy (FTIR). The morphologies of magnetic NPs were further investigated by transmission electron microscopy (TEM). The magnetization and superparamagnetic behavior of naked Fe₃O₄ NPs and coated NPs at room temperature was investigated by the measurement of hysteresis curves using a Vibrating Sample Magnetometer (VSM).     

Improvement of dissolution behavior of poorly water soluble drugs by biodegradable polymeric submicron carriers containing sparingly methylated β-cyclodextrin

The objective of this study was to develop submicron carriers of two drugs that are practically insoluble in water, i.e. meloxicam and aceclofenac, to improve their dissolution behavior. The phase solubility of the drugs was studied using different concentrations of sparingly methylated β-cyclodextrin, Kleptose^® Crysmeβ (Crysmeb), in the presence and absence of 0.2 % w/v water-soluble chitosan. Drug-loaded submicron particles (SMPs) were prepared using chitosan chlorhydrate and Crysmeb by the ionotropic gelation method. The SMPs were characterized in terms of powder X-ray diffraction, Fourier transforms infrared spectroscopy, size determination, process yield, drug loading, encapsulation efficiency, surface morphology and in vitro release. The drug loading in the SMPs was enhanced in the presence of Crysmeb. The in vitro drug release was found to be enhanced with SMPs prepared using higher concentrations of Crysmeb. These results indicate that SMPs formed from chitosan chlorhydrate and Crysmeb are promising submicron carriers for enhancing the dissolution of meloxicam and aceclofenac.     

Room-temperature ferromagnetic and photoluminescence properties of indium–tin-oxide nanoparticles synthesized by solid-state reaction

In the present study, indium–tin-oxide (ITO) nanoparticles were synthesized using solid-state reaction and studied for their structural, vibrational and magnetic properties. The ITO nanoparticles were prepared under reduced pressure, which can increase the oxygen vacancies in the samples. The X-ray diffraction studies confirmed singe-phase cubic bixbyite structure of ITO with average crystallite size of 47 nm. The lattice vibrational studies (FT-IR and Raman spectroscopy) at room temperature indicated that Sn ions were occupied in In₂O₃ lattice and gives corresponding active vibrational modes in the respective spectra. The magnetic studies at room temperature reveal the ferromagnetic nature of ITO and the strength of magnetization is superior to those of In₂O₃ and SnO₂. However, the magnetic studies at 100 K revealed reduced ferromagnetism, which could be attributed to reduced itinerary electrons at low temperature. Blue and blue–green emissions were found from the ITO nanoparticles, which could be due to vacancies or surface defects present in the system.     

Preparation of β-TCP with high thermal stability by solid reaction route

Starting from commercial materials, -TCP powder was prepared by a conventional solid reaction route. Using DTG, TG and DTA, the mass change and the heat flow during heating of the commercial powder mixture were tested. The phase evolution at each step of the heating was monitored using XRD analyses. Based on the tests and the analyses the reaction details were analyzed. The -TCP powder prepared in this study has high thermal stability. The phase transition temperature from to was determined to be 1350°C, 200°C higher than commercial -TCP powder (Plasma Biotal). The high phase transition temperature was due to Mg trace in the starting materials.     

Highly selective electrocatalytic Cl− oxidation reaction by oxygen-modified cobalt nanoparticles immobilized carbon nanofibers for coupling with brine water remediation and H2 production

Combining the H2 production with brine remediation is regarded as a sustainable approach to achieving clean H2 energy. However, designing stable Cl? oxidation reaction (COR) electrocatalyst is the key to realize this route. Herein, a type of oxygen-modified Co nanoparticles anchored graphitic carbon nanofibers catalyst (Co/GCFs) was synthesized through a two-step strategy of adsorption and pyrolysis. The Co/GCFs-2.4 exhibits high selectivity and stability for COR at neutral electrolyte. It is worth noting that unlike the water oxidation, the chemical valence of cobalt has not changed during the COR. Further results demonstrated that the oxygen-modified Co nanoparticles provide active sites for selective COR, meanwhile, the graphitic carbon gives rise to strong catalytic stability. Thanks to the superior COR and H2 production activity of Co/GCFs-2.4, a two-electrode brine electrocatalysis system employing Co/GCFs-2.4 as both cathode and anode for H2 production exhibited robust stability, efficient and high Faraday efficiency (98%-100%). We propose that this work provides a novel strategy for designing efficient and stable catalysts with electrocatalytic COR and HER activities at neutral brine water for practically coupling with H2 production by water electrolysis and brine water remediation.     

Magnetite–hematite nanoparticles prepared by green methods for heavy metal ions removal from water

Mixed magnetite–hematite nanoparticles were synthesized via different routes such as, coprecipitation in air and N₂ atmosphere, citrate–nitrate, glycine–nitrate and microwave-assisted citrate methods. The prepared samples were characterized by X-ray diffraction (XRD), high resolution transmission electron microscope (HRTEM), BET measurements and magnetic hysteresis. XRD data showed the formation of magnetite–hematite mixture with different compositions according to the synthesis method. The particle size was in the range of 4–52 nm for all the prepared samples. From HRTEM micrographs, it was found that, the synthesis method affects the moropholgy of the prepared samples in terms of crystallinity and porosity. The magnetite–hematite mixture was employed as a sorbent material for removal of some heavy metal ions from water such as lead(II), cadmium(II) and chromium(III). The effects of pH value and the contact time on the adsorption process were studied and optimized in order to obtain the highest possible adsorption efficiency of the magnetite–hematite mixture. The effect of the synthesis method of the magnetite–hematite mixture on the adsorption process was also investigated. It was found that samples prepared by the coprecipitation method had better adsorption efficiency than those prepared by other combustion methods.     

Arrhenius plot for a reaction catalyzed by a single molecule of β-galactosidase

The activity of a single enzyme molecule of Escherichia coli β-galactosidase was measured using a capillary electrophoresis continuous flow assay. As the enzyme molecule traversed the capillary the incubation temperature was increased from 27 to 37 °C, providing a continuous record of the change in rate with temperature. This data was used to develop a single enzyme molecule Arrhenius plot, from which the activation energy of the reaction was determined to be 31 kJ mol(-1).     

Glycerol valorization by base-free oxidation with air using platinum–nickel nanoparticles supported on activated carbon as catalyst prepared by a simple microwave polyol method

Biodiesel is one of the most common biofuels, and its production yields a large amount of glycerol as a by-product. It is necessary to develop new technologies for the use of this by-product, adding value to the biodiesel production chain. In this work we investigated glycerol oxidation under mild reaction conditions (air as oxidizing agent and base-free medium) promoted by suitable catalysts. We prepared mono- and bimetallic catalysts of platinum, copper and nickel in the form of nanoparticles by conventional heating and by an alternative method using microwave heating. The nanoparticles were dispersed in activated carbon and tested in glycerol oxidation aiming its valorization into molecules with high added value. Copper and nickel monometallic materials were not active in glycerol oxidation. Platinum monometallic and platinum–copper and platinum–nickel bimetallic materials showed catalytic activity, with platinum–nickel prepared by microwave heating being the most active material in reactions tested. This catalyst presented glycerol conversion of approximately 20% with a turnover number of 9465 in a reaction time of 6 h and 58% of selectivity to glyceric acid, the main product obtained. The best performance of platinum–nickel prepared by microwave heating catalyst was attributed to the probable formation of a metallic alloy between Pt and Ni, as evidenced by the decrease in the lattice parameter for PtNi bimetallic nanoparticles. The results showed that it was possible to obtain an active catalyst in glycerol oxidation reaction under mild conditions via a simple methodology using microwave heating, which demands 94% less time in comparison with conventional heating.     

Gold nanoparticles supported on ceria-modified mesoporous–macroporous binary metal oxides as highly active catalysts for low-temperature water–gas shift reaction

New gold catalytic system prepared on ceria-modified meso-/macroporous binary metal oxide support (CeO₂/TiO₂–ZrO₂) and used as water–gas shift reaction (WGSR) catalyst is reported. The support was prepared through the surfactant templating technique combining with the use of mixed alkoxide solutions. Ceria-modifying additive and gold were deposited consecutively on the meso-/macroporous TiO₂–ZrO₂ by deposition-precipitation method. The samples were characterized by powder X-ray diffraction, scanning and transmission electron microscopy, N₂ adsorption analysis, and temperature-programmed reduction. The catalytic activity of the new gold-based catalysts was evaluated in WGSR and it was compared with that of gold catalysts supported on simple and binary mesoporous oxides (TiO₂, ZrO₂, and TiO₂–ZrO₂) and ceria-modified mesoporous titania support (CeO₂/mTiO₂). A high degree of synergistic interaction between ceria and support and a positive modification of structural and catalytic properties have been achieved. The new gold catalytic system is found to be a promising catalyst for practical WGSR application.     

Lipid nanoparticles of zaleplon for improved oral delivery by Box–Behnken design: optimization,in vitro and in vivo evaluation

Purpose: Zaleplon (ZL) is a hypnotic drug prescribed for the management of insomnia and convulsions. The oral bioavailability of ZL was low (～30%) owing to poor water solubility and hepatic first-pass metabolism. The cornerstone of this investigation is to develop and optimize solid lipid nanoparticles (SLNs) of ZL with the aid of Box–Behnken design (BBD) to improve the oral bioavailability.

Methods: A design space with three formulation variables at three levels were evaluated in BBD. Amount of lipid (A₁), amount of surfactant (A₂) and concentration of co-surfactant (%) (A₃) were selected as independent variables, whereas, particle size (B₁), entrapment efficiency (B₂) and zeta potential (ZP, B₃) as responses. ZL-SLNs were prepared by hot homogenization with ultrasonication method and evaluated for responses to obtain optimized formulation. Morphology of nanoparticles was observed under SEM. DSC and XRD studies were examined to understand the native crystalline behavior of drug in SLN formulations. Further, in vivo studies were performed in Wistar rats.

Results: The optimized formulation with 132.89?mg of lipid, 106.7?mg of surfactant and 0.2% w/v of co-surfactant ensued in the nanoparticles with 219.9?±?3.7?nm of size, ?25.66?±?2.83?mV surface charge and 86.83?±?2.65% of entrapment efficiency. SEM studies confirmed the spherical shape of SLN formulations. The DSC and XRD studies revealed the transformation of crystalline drug to amorphous form in SLN formulation. In conclusion, in vivo studies in male Wistar rats demonstrated an improvement in the oral bioavailability of ZL from SLN over control ZL suspension.

Conclusions: The enhancement in the oral bioavailability of ZL from SLNs, developed with the aid of BBD, explicated the potential of lipid-based nanoparticles as a potential carrier in improving the oral delivery of this poorly soluble drug.     

Using ionic liquid as the solvent to prepare Pd–Ni bimetallic nanoparticles by a pyrolysis method for ethanol oxidation reaction

Room temperature ionic liquids (RTILs) of 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIBF4) is used as the solvent for the first time to prepare multi-walled carbon nanotubes (MWCNTs) supported nanocomposite catalysts of Pd_xNi_y (atomic ratios of Pd to Ni are 1:1, 1:1.5, 1:2, and 1:2.5) nanoparticles (denoted as Pd_xNi_y/MWCNTs) by using a simple pyrolysis process. The Pd_xNi_y/MWCNTs catalysts are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Results show that the Pd_xNi_y nanoparticles (NPs) are quite uniformly dispersed on the surface of MWCNTs with an average crystallite size of ∼7.0 nm. The electro-catalytic activity of the Pd_xNi_y/MWCNTs catalysts for ethanol oxidation reaction (EOR) is examined by cyclic voltammetry (CV). It is revealed that the onset potential is ∼80 mV lower and the peak current is about three times higher for ethanol oxidation for MWCNT catalysts with Pd₁Ni_1.5 compared to those of Pd/MWCNTs. The catalytic mechanisms of the Pd₁Ni_1.5/MWCNTs towards EOR are also proposed and discussed.     

Effect of Si/Fe ratio on the boron and phosphorus doping efficiency of β-FeSi2 by magnetron sputtering

Boron-doped or phosphorus-doped β-FeSi₂ thin films have been prepared on silicon substrate by magnetron sputtering. Effects of Si/Fe ratio on the boron and phosphorus doping efficiencies have been studied from the resistivities of doped β-FeSi₂ thin films and current-voltage characteristics of doped β-FeSi₂/Si heterojunctions. The experimental results reveal that the carrier concentration and doping efficiency of boron or phosphorus dopants at the Fe-rich side are higher than that at the Si-rich side. The effect of Si/Fe ratio can be deduced from the comparison of the formation energies under two extreme conditions. At the Fe-rich limit condition, the formation energy of boron or phosphorous doping is lower than that at the Si-rich condition. Therefore, the activation of impurities is more effective at the Fe-rich side. These results demonstrate that the boron-doped and phosphorous-doped β-FeSi₂ thin films should be kept at the Fe-rich side to avoid the unexpected doping sites and low doping efficiency.     

Preparation and characterization of water soluble and conducting poly(sodium 4-styrenesulfonate) doped poly(3,4-ethylenedioxythiophene)/multi-walled carbon nanotubes core–shell nanocomposites by in situ polymerization

Water soluble and conducting poly(sodium 4-styrenesulfonate) (PSSNa) doped poly(3,4-ethylenedioxythiophene) (PEDOT)/multi-walled carbon nanotubes (MWNTs) nanocomposites were synthesized by PSSNa functionalized MWNTs and 3,4-ethylenedioxythiophene (EDOT) in situ oxidation polymerization. In the process, MWNTs were functionalized by PSSNa via physicochemical interaction, PSS groups on the surface of MWNTs absorbed EDOT monomers and acted as counter ions during in situ polymerization, macromolecules of PEDOT growth on the surface of MWNTs formed a homogeneous core (MWNTs)–shell (PEDOT) nanostructure. Owing to water soluble PEDOT–PSSNa coating on the surface of MWNTs and the association of PSSNa acting as inter-linking between PEDOT and MWNTs, the core–shell nanostructures were dissolved in water forming stable aqueous solution with good transparence. The composite was more stable in the temperature range up to 300 °C and exhibited improved thermal stability at the range of 300–500 °C compared with PEDOT–PSSNa. Because of π–π interactions between MWNTs and PEDOT coatings as well as homogenously dispersion of MWNTs in PEDOT, conductivity of the composites at room temperature was increased by two orders of magnitude over PEDOT–PSSNa.     

Electrophoretic deposition of Y2O3-stabilized ZrO2 nanoparticles on the surface of dense La0.7Sr0.3MnO3−δ cathodes produced by pyrolysis and solid-state reaction

La_0.7Sr_0.3MnO_3?δ (LSM) cathode materials have been prepared through pyrolysis of liquid precursors and by solid-state reaction. We examined the effect of the cathode material synthesis procedure on the growth of thin films of a solid electrolyte based on Y₂O₃-stabilized ZrO₂ (YSZ) nanopowder with an average geometric size of 10.9 nm on a dense surface of model cathodes by electrophoretic deposition. Using electron microscopy, BET surface area measurements, X-ray diffraction, thermal analysis, and dilatometry, we investigated the structure, specific surface area, phase composition, thermal properties, and sintering-induced volume changes of cathode materials differing in prior history. The results demonstrate that the starting cathode materials differed markedly in properties, but the cathodes produced by sintering them were identical in phase composition: they consisted entirely of a rhombohedral phase. The room-temperature electrical conductivity of the cathodes produced by solid-state reaction was 0.231 ± 0.01 S/cm, exceeding that of the cathodes produced through pyrolysis by an order of magnitude.     

Influence of the reaction time and the Triton x-100/Cyclohexane/Methanol/H2O ratio on the morphology and size of silica nanoparticles synthesized via sol–gel assisted by reverse micelle microemulsion

The present paper describes the synthesis of silica nanoparticles via the sol–gel method assisted by reverse micelle microemulsion, using reagents as Triton x-100/Cyclohexane/Methanol/H₂O, and also the effect on particle size of some synthesis parameters such as the water-surfactant molar ratio (R), Co-surfactant-surfactant (ρ), and synthesis time (t). The structure, morphology, and size of the silica nanoparticles were characterized with transmission electron microscopy and scanning electron microscopy. A variation of ρ = [Methanol]/[Triton X-100] affects the size, morphology, and dispersion of the particles. An increase in the concentration of methanol produces a decrease in particle size. The condition that resulted in smaller particle size, better spherical morphology, and monodispersity was when ρ = 7.6, which generated an approximate size of 83 ± 7 nm. The parameter R = [H₂O]/[Triton X-100] affects not only the size of the particles, but also their morphology. Higher values of R result in a decrease in the amount of catalyst present in the interior of the micelle, but in turn generate a greater amount of water, which results in a decrease in particle size and polydispersity. Time is a parameter that directly affects the size of the silica particles. The optimal time for the synthesis of nanoparticles was 2 h, resulting in silica nanoparticles of 25 ± 3 nm, monodisperse, with spherical morphology and without the presence of agglomerations.     

Synthesis of Yb<Superscript>3+</Superscript>, Ho<Superscript>3+</Superscript> and Tm<Superscript>3+</Superscript> co-doped β-NaYF<Subscript>4</Subscript> nanoparticles by sol–gel method and the multi-color upconversion luminescence properties

Well-crystalline β-NaYF₄:Yb³⁺, Ho³⁺, Tm³⁺ nanoparticles were synthesized by sol–gel method using isopropyl alcohol [(CH₃)₂CHOH] as a complexing agent. The samples were characterized by X-ray diffraction, scanning electron microscopic analysis and fluorescence spectrum analysis methods. Under the excitation of 980 nm laser diode (LD), the samples displayed bright upconversion luminescence (UCL), which was generated from the energy level transition of Ho³⁺ and Tm³⁺ ions. With the increase of Tm³⁺, Ho³⁺ and Yb³⁺-doping concentration, the UCL intensity of blue, green and red light emission of the samples varied. Calculation of the CIE color coordinate of the β-NaYF₄:Yb³⁺, Ho³⁺, Tm³⁺ nanoparticles revealed that with the adjustment of Tm³⁺, Ho³⁺ and Yb³⁺ doping concentration and the excitation power of 980 nm LD, the multi-color UCL can be realized. Approximately single red light output with the CIE color coordinate of x?=?0.545, y?=?0.306 and white light output with the CIE color coordinate of x?=?0.325, y?=?0.320 can be obtained in the synthesized β-NaYF₄: Yb³⁺, Ho³⁺, Tm³⁺ nanoparticles.