Nanoparticles In Liquid Phase Research Articles

Synthesis of Vertically Aligned Carbon Nanotube Arrays from Premade Bimetallic Aluminum-Iron Oxide Nanoparticles Monolayer

: Carbon Nanotubes (CNTs) are excellent materials because of their unique physical and chemical properties. Though catalyst nanoparticles preparation from thin film catalysts are common but premade catalysts nanoparticles in liquid phase has control over the size and composition which control the diameter and length of CNTs. Here, we report the synthesis of vertically aligned (VA) CNTs on metal oxide substrates including silicon oxide and stainless-steel using aluminum-iron oxides Al2O3-Fe2O3 nanoparticles monolayer. Oleic acid functionalized Al2O3-Fe2O3 nanoparticles were assembled onto metal oxide substrate as a monolayer using 11-phousnoundecanoic acid (PNDA) linker molecule where phosphonate group bind to the substrate and terminal carboxylic group of PNDA bind to the surface of bimetallic oxide catalysts. Homogenous catalyst nanoparticles distribution from monolayer assembly can reduce the aggregation of catalyst particles which can increases the catalyst lifetime during CNTs growth. Synthesis of VA-CNTs require Al2O3 catalyst support on substrate surface, but our bimetallic Al2O3-Fe2O3 nanoparticles contain both catalyst support (Al2O3) and catalyst (Fe) in the same particle. The successful VA-CNTs synthesis were achieved by chemical vapor deposition (CVD) process using acetylene as carbon precursor in atmospheric pressure. We envision that our catalyst preparation for VA-CNTs growth can be a cost-efficient method for large scale synthesis of CNTs. Further, the VA-CNTs growth on conductive stainless-steel substrate can facilitate the electrochemical application of this hybrid materials for biomolecule sensing and heavy metals detection.

Method for 3D atomic structure determination of multi-element nanoparticles with graphene liquid-cell TEM

Determining the 3D atomic structures of multi-element nanoparticles in their native liquid environment is crucial to understanding their physicochemical properties. Graphene liquid cell (GLC) TEM offers a platform to directly investigate nanoparticles in their solution phase. Moreover, exploiting high-resolution TEM images of single rotating nanoparticles in GLCs, 3D atomic structures of nanoparticles are reconstructed by a method called “Brownian one-particle reconstruction”. We here introduce a 3D atomic structure determination method for multi-element nanoparticle systems. The method, which is based on low-pass filtration and initial 3D model generation customized for different types of multi-element systems, enables reconstruction of high-resolution 3D Coulomb density maps for ordered and disordered multi-element systems and classification of the heteroatom type. Using high-resolution image datasets obtained from TEM simulations of PbSe, CdSe, and FePt nanoparticles that are structurally relaxed with first-principles calculations in the graphene liquid cell, we show that the types and positions of the constituent atoms are precisely determined with root mean square displacement values less than 24 pm. Our study suggests that it is possible to investigate the 3D atomic structures of synthesized multi-element nanoparticles in liquid phase.

Electropulse coating by deposition of metal nanoparticles in liquid phase on a solid surface

The process of formation of metal nanoparticles in a liquid dielectric phase and their deposition on a solid surface is studied. The fundamental possibility of forming a coating on a porous surface is shown. Keywords: nanoparticle, metal, electropulse deposition, liquid medium, coating, thin-film structure, single crystal. lew1967@mail.ru

Improvement of the properties of light metal matrix Micro/Nanocomposite Materials: myth or reality?

The use of materials reinforced by micro-nanoparticles (MMC) is more and more widespread. According to recent studies, the addition of micro-particles in solid materials (polymers, concrete or metal alloys) gives them interesting properties in terms of thermal conductivity, electrical conductivity and mechanical resistance. These properties open new perspectives in terms of environmental consequences. They allow for example to lighten structures while improving their mechanical characteristics, to increase the performance of electrical conductors by reducing energy losses. We provide an example related to light metal alloys widely used in automotive industry and aeronautics. However, the introduction of particles presents several difficulties. The efficiency of particle addition at liquid state depends on many factors, like their dimension, the type of sedimentation forces and the chemical composition of both liquid alloys and particles:(i) at the metallurgical level, the particles are often very reactive and may modify the composition and the micro-structure of the alloy, which can be sometimes beneficial and sometimes damaging,(ii) in terms of scale-up and development of actual processes, the introduction of micro- and especially nanoparticles in liquid phase is a very difficult operation to achieve. Many types of devices are proposed but none is really satisfactory, especially regarding the homogeneity of the materials.We present some application cases related to magnesium alloys that perfectly illustrate the advantages and disadvantages of MMCs.

Shape-based separation of micro-/nanoparticles in liquid phases.

The production of particles with shape-specific properties is reliant upon the separation of micro-/nanoparticles of particular shapes from particle mixtures of similar volumes. However, compared to a large number of size-based particle separation methods, shape-based separation methods have not been adequately explored. We review various up-to-date approaches to shape-based separation of rigid micro-/nanoparticles in liquid phases including size exclusion chromatography, field flow fractionation, deterministic lateral displacement, inertial focusing, electrophoresis, magnetophoresis, self-assembly precipitation, and centrifugation. We discuss separation mechanisms by classifying them as either changes in surface interactions or extensions of size-based separation. The latter includes geometric restrictions and shape-dependent transport properties.

Characterization: Characterizing Physical Properties of Superparamagnetic Nanoparticles in Liquid Phase Using Brownian Relaxation (Small 22/2017)

Characterization: Characterizing Physical Properties of Superparamagnetic Nanoparticles in Liquid Phase Using Brownian Relaxation (Small 22/2017)

Characterizing Physical Properties of Superparamagnetic Nanoparticles in Liquid Phase Using Brownian Relaxation

Superparamagnetic iron oxide nanoparticles (SPIONs) have been extensively used as bioimaging contrast agents, heating sources for tumor therapy, and carriers for controlled drug delivery and release to target organs and tissues. These applications require elaborate tuning of the physical and magnetic properties of the SPIONs. The authors present here a search-coil-based method to characterize these properties. The nonlinear magnetic response of SPIONs to alternating current magnetic fields induces harmonic signals that contain information of these nanoparticles. By analyzing the phase lag and harmonic ratios in the SPIONs, the authors can predict the saturation magnetization, the average hydrodynamic size, the dominating relaxation processes of SPIONs, and the distinction between single- and multicore particles. The numerical simulations reveal that the harmonic ratios are inversely proportional to saturation magnetizations and core diameters of SPIONs, and that the phase lag is dependent on the hydrodynamic volumes of SPIONs, which corroborate the experimental results. Herein, the authors stress the feasibility of using search coils as a method to characterize physical and magnetic properties of SPIONs, which may be applied as building blocks in nanoparticle characterization devices.

Microwave‐Assisted Synthesis of Metallic Nanomaterials in Liquid Phase

AbstractMetallic nanoparticles are one of the fundamental materials in nanoscience and nanotechnology because they gave novel optical, electronic, magnetic, and catalytic properties, different from those of bulk metals. Since these unique properties depend on shape, size, and composition of nanoparticles, their controlled syntheses are required. Among many synthesis methods of metallic nanoparticles in liquid phase, microwave (MW)‐assisted syntheses recently received a great attention because shape‐ and size‐selective syntheses of nanoparticles are possible in a shorter overall processing time than those in the conventional oil‐bath heating. This minireview is not meant to give an exhaustive overview of all metallic nanoparticles synthesized by MW heating, but to represent principles and advantage of MW‐assisted processes from recent representative researches. I especially focus on preparation and application of core‐shell type hybrid particles, which have unique chemical, physical, and optical properties, different from monometallic nanoparticles. Specific roles of MW irradiation in the formation of metallic nanoparticles are discussed.

To the nature of the support effect in palladium-catalyzed aqueous-phase hydrogenation of maleic acid

Influence of the support nature on catalytic properties of the supported Pd nanoparticles in liquid-phase (water, ethanol) hydrogenation of maleic acid (MA) to succinic one was extensively studied. Different oxides (SiO2, diatomites, WO3, Ta2O5, Nb2O5, V2O5, TiO2, CeO2, ZrO2, Ga2O3, In2O3, Cr2O3, Fe2O3, Al2O3), salts (CaF2, BaSO4) and carbon supports either with extremely low or high porosity were employed as the catalyst supports. XPS studies of the catalysts revealed no significant support-induced changes of the electronic state of the active component. For palladium on non-porous supports, its TOF values in MA hydrogenation turned to be constant in ethanol medium but varied with the support nature in water. In the case of porous supports, the TOFs diminished in both media and were governed by mean pore size and surface acidity of the supports. The dependence of TOF values on mean distance between adjacent Pd nanoparticles is also revealed. The catalytic results are explained by the presence of the electric double layer at the catalyst-solution interface, which affect its catalytic performance.

Self-Assembly of Charged Nanoparticles by an Autocatalytic Reaction Front.

In this work we present that aggregation of charged and pH sensitive nanoparticles can be spatiotemporally controlled by an autonomous way using the chlorite-tetrathionate autocatalytic front, where the front regulates the electrostatic interaction between nanoparticles due to protonation of the capping (carboxylate-terminated) ligand. We found that the aggregation and sedimentation of nanoparticles in liquid phase with the effect of reversible binding of the autocatalyst (H(+)) play important roles in changing the front stability (mixing length) and the velocity of the front in both cases when the fronts propagate upward and downward. Calculation of interparticle interactions (electrostatic and van der Waals) with the measurement of front velocity revealed that the aggregation process occurs fast (within a few seconds) at the front position.

Composition and Oxidation State of Cobalt and Nickel-Iron Oxide Colloidal Nanoparticles in Liquid Phase

The magnetic nanoparticles of cobalt-and nickel-iron oxide have been extensive interest due to their superparamagnetic properties and their potential applications in many fields. The iron, cobalt and nickel can stay in many oxidation states and are easily oxidized especially in ambient air therefore the composition and oxidation states of these oxides can be unintentionally modified. Usually, the composition and oxidation states in these magnetic nanoparticles are determined by various experimental techniques required a sample in solid phase. This may lead the nanoparticles to directly contact with air and change the state. In this study, the magnetic nanoparticles in colloidal phase with concentration of 24mg/ml, derived from co-precipitation process, were directly injected to liquid cell for X-ray absorption near-edge structure (XANES) measurement. The iron-, cobalt-or nickel-iron oxide nanoparticles were prepared by dissolving CoCl2/FeCl3 or NiCl2/FeCl3, respectively, in deionized water with various atomic ratios. The average iron oxide nanoparticle size obtained by dynamic light scattering is about 4.2 nm with polydispersity of 0.987. Spherical shape with some stabilizer layer was observed by transmission electron microscope. The iron content in various composition nanoparticles was estimated in liquid phase by the ratio between the Fe edge peak and Co or Ni edge peak. The oxidation states of metal ions were also derived from the linear fitting of standard compounds at particular oxidation states. The shifts of peak positions were examined to indicate the variation of oxidation state as well.

Synthesis and characterization of green agents coated Pd/Fe bimetallic nanoparticles

The low stability and mobility of nanoparticles in liquid phase is one of the biggest challenges for the application of zero-valent iron (ZVI) technology. In this research, three green agents, polyethylene glycol (PEG), starch, and guar gum were coated on Pd/Fe bimetallic nanoparticles (NPs) to enhance the stability and reactivity of Pd/Fe NPs. The modified NPs (PEG-Pd/Fe, Starch-Pd/Fe, and Guar gum-Pd/Fe NPs) were characterized in terms of specific surface area, particle size, shape, morphology, and structural feature, etc. The results show that the diameters of modified Pd/Fe NPs are in the range of 60–100 nm. Compared with the pristine unmodified Pd/Fe NPs, the aggregations of modified Pd/Fe NPs were successfully reduced. XRD patterns indicate that modified Pd/Fe NPs remained the body centered cubic crystal structure, and the modification process contributed to improve the antioxidant ability. 2,4-Dichlorophenol (2,4-DCP) dechlorination experiments show that physico-chemical properties of the three modifiers have different effects on the reactivity of modified Pd/Fe NPs. The initial pH value of the reaction system had complex effects on the dechlorination of 2,4-DCP by using modified Pd/Fe NPs. Activation energies of pristine, PEG-Pd/Fe, Starch-Pd/Fe, and Guar gum-Pd/Fe NPs were calculated to be 39.47 kJ/mol, 38.66 kJ/mol, 36.59 kJ/mol, and 33.88 kJ/mol, respectively, implying that the modification process can enhance the dechlorination rate of Pd/Fe NPs, and that catalytic hydrodechlorination process of 2,4-DCP with modified Pd/Fe NPs is a surface-controlled chemical reaction.

Formation and properties of hydrophobic CeO2 nanoparticles

Uniform hydrophobic cerium oxide (CeO2) nanoparticles in a cubic structure with an average size of 4.6 nm were obtained by a novel oil-water interface method in the presence of 0.40 M NaOH. Effects of reactants concentration, oxidation reaction temperature, and the type of surfactants on the final products were investigated. The products were characterized by X-ray diffraction, transmission electron microscopy, UV-visible spectroscopy, room-temperature photoluminescence spectroscopy and contact angle measurements. The products exhibited high luminescence and strong hydrophobicity. The data suggest that Ce(OH) 4− (x < 4) is a precursor complex for the formation of CeO2 nanoparticles in liquid phase and its concentration controls the size of CeO2 particles. The adsorption of the surfactant influences the formation of the hydrophobic particles of CeO2 by the oil-water interface method.

Sherrie Elzey and De-Hao Tsai win ABC Best Paper Award.

Sherrie Elzey was born in 1981. She earned her B.S. degree in chemistry and B.A. degree in physics from the University of Northern Iowa (Cedar Falls, IA, USA). She received a National Defense Science and Engineering Graduate fellowship and earned her Ph.D. degree from the University of Iowa (Iowa City, IA, USA). She was then awarded a National Research Council postdoctoral fellowship at the National Institute of Standards and Technology (NIST; Gaithersburg, MD, USA). At NIST, she conducted research in the Materials Measurement Laboratory focusing on method development for measuring the size and elemental composition of representative therapeutic nanoparticles with functionalized surfaces. After her postdoctoral research, she joined TSI (Shoreview, MN, USA) as an applications engineer, where she applied a variety of sizing methods to measure airborne and liquid-phase nanoparticles. She is currently a regional sales manager at TSI. De-Hao Tsai was born in 1976. He earned a B.S. degree in chemical engineering from the National Cheng Kung University (Tainan, Taiwan) in 1998, and an M.S. degree in chemical engineering from the National Tsing Hua University (Hsinchu, Taiwan) in 2000. He received his Ph.D. degree in materials science and engineering from the University of Maryland (College Park, MD, USA) in 2007 under the supervision of Michael R. Zachariah. He is currently Assistant Professor in the Department of Chemical Engineering at NTHU. Prior to joining NTHU, he worked as a research scientist at Cabot Microelectronics (Aurora, IL, USA; 2008–2009) and as a research associate at NIST (2009–2013). During his tenure at NIST, his research work focused onmeasurements for applications in nanomedicine supervised by Vincent A. Hackley. In 2013, he received the 2013 Distinguished Associate Award for Technical Achievement at NIST to acknowledge his exemplary leadership in the development of innovative physical and chemical metrology for applications in cancer nanotechnology.

Photoassisted and photocatalytic degradation of sulfur mustard using TiO2 nanoparticles and polyoxometalates

The decomposition of highly toxic chemical warfare agent, sulfur mustard (bis(2-chloroethyl) sulfide or HD), has been studied by homogeneous photolysis and heterogeneous photocatalytic degradation on titania nanoparticles. Direct photolysis degradation of HD with irradiation system was investigated. The photocatalytic degradation of HD was investigated in the presence of TiO(2) nanoparticles and polyoxometalates embedded in titania nanoparticles in liquid phase at room temperature (33 ± 2 °C). Degradation products during the treatment were identified by gas chromatography-mass spectrometry. Whereas apparent first-order kinetics of ultraviolet (UV) photolysis were slow (0.0091 min(-1)), the highest degradation rate is obtained in the presence of TiO(2) nanoparticles as nanophotocatalyst. Simultaneous photolysis and photocatalysis under the full UV radiation leads to HD complete destruction in 3 h. No degradation products observed in the presence of nanophotocatalyst without irradiation in 3 h. It was found that up to 90 % of agent was decomposed under of UV irradiation without TiO(2), in 6 h. The decontamination mechanisms are often quite complex and multiple mechanisms can be operable such as hydrolysis, oxidation, and elimination. By simultaneously carrying out photolysis and photocatalysis in hexane, we have succeeded in achieving faster HD decontamination after 90 min with low catalyst loading. TiO(2) nanoparticles proved to be a superior photocatalyst under UV irradiation for HD decontamination.

ChemInform Abstract: Catalysis of Metal Oxide‐Supported Gold Nanoparticles in Liquid Phase

AbstractReview: ca. 70 refs.

Revealing oxidation kinetics of dielectric-embedded Ag nanoparticles via in situ optical microspectroscopy

The oxidation kinetics of Ag nanoparticles (NPs) embedded in an aluminum oxide film deposited on quartz have been assessed via an in situ real-time monitoring of plasmonic evolution during thermal processing in air. A temperature-dependent exponential decay in the peak intensity of Ag NPs’ absorption was revealed, which was analyzed through first-order kinetics. An activation energy of 3.28 (±0.27)×104Jmol−1 was estimated in good agreement with the oxidative dissolution of similar-sized Ag NPs in liquid phase reported by Ho et al. [11]. Results are discussed in the context of mechanistic parallelisms and physico-chemical interactions in the air-atmosphere/nanocomposite-film/substrate system.

Synthesis and physico-chemical characterization of Au/TiO 2 nanostructures formed by novel “cold” and “hot” nanosoldering of Au and TiO 2 nanoparticles dispersed in water

A novel approach to synthesize Au/TiO 2 nanostructures with interesting optical properties is presented and discussed. It is based on the nanoparticle “cold” or “hot” nanosoldering occurring when two water suspensions of Au and TiO 2 nanoparticles are merely mixed at room temperature or laser irradiated after mixing. Thanks to the high fraction and mutual reactivity of surface species, immediately after the mixing process, the encounters between Au and TiO 2 nanoparticles in liquid phase are enough for “cold” nanosoldering of gold nanoparticles onto TiO 2 nanoparticles to occur. The optical characterizations show that this fast process (timescale less than 1 min) is followed by a slower process, attributable to some change of the Au nanoparticles. This latter process is significantly accelerated by the 532 nm laser light illumination. The structural and optical properties of “cold” and “hot” nanosoldered Au–TiO 2 nanoparticles were investigated by TEM, UV–vis and fluorescence spectroscopies. Interesting optical limiting response was detected at laser fluences above 0.8 J/cm 2. The nature of the nonlinear effect was investigated by the Z-scan technique, determining both the nonlinear absorption coefficient and the refraction index. Such interesting non-linear optical properties are worth to be tailored for specific applications.

Aggregation and Dispersion Behavior Control of Nanoparticles in Liquid Phase

Aggregation and Dispersion Behavior Control of Nanoparticles in Liquid Phase

Cystine modified nano-sulfur and its spectral properties

A novel sulfur form, insect-like nano elemental sulfur (nano-S 0) was prepared by adding cystine to sulfur-ethanol solution. The modification and modulation of cystine on elemental sulfur (S 0) nanoparticles in liquid phase were studied. Transmission electron microscope (TEM), resonance Rayleigh scattering (RRS), infrared (IR) and Raman spectra (RS) were used to study the function of cystine in modification and assembly of S 0 nanoparticles. The results show that the cystine modulated the S 0 nanoparticles in the aspects of the size, shape and stability in the liquid phase. The cystine-nano-S 0 Sol obtained was stable in solution for long time.