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Nano-biomaterial hybridization is a promising strategy to generate unique and advanced material properties that are not available with nano- or biomaterials alone. In particular, the surface stabil...

Here, the influence of Batchelor vortex flow on the cocrystallization of caffeine (CAF) and maleic acid (MA) is studied and compared with that of turbulent eddy flow. Batchelor flow, induced in a r...

To obtain high catalytic properties, finely modulating the electronic structure and active sites of catalysts is important. Herein, we report the design and economical synthesis of Pd@Pt core-shell nanoparticles for high productivity in the direct synthesis of hydrogen peroxide. Pd@Pt core-shell nanoparticles with a partially covered Pt shell on a Pd cube were synthesized using a simple direct seed-mediated growth method. The synthesized Pd@Pt core-shell nanoparticles were composed of high index faceted Pt on the corners and edges, while the Pd-Pt alloy was located on the terrace area of the Pd cubes. Because of the high-indexed Pt and Pd-Pt alloy sites, the synthesized concave Pd@Pt7 nanoparticles exhibited both high H2 conversion and H2O2 selectivity compared with Pd cubes.

In this report, a Couette-Taylor (CT) reactor was applied as an effective continuous process for synthesizing copper sulfide nanoparticles. The rotational speed, mean residence time (MRT), and concentration of the feed solution were important control factors on the morphology and size control of the nanoparticles. Increasing the rotational speed from 80 rpm to 90 rpm changed the morphology of the synthesized nanoparticles from nanofibers to hexagonal nanoplates. Only Cu7S4 nanofibers were obtained in the batch reactor. Through various comparative experiments, we found that MRT and the feed solution concentration affect monomer concentration in the CT reactor, thus controlling the morphology and size of the nanoparticles.

The detection of hydrogen peroxide (H2O2) is essential in many research fields, including medical diagnosis, food safety, and environmental monitoring. In this context, Au-based bimetallic alloy nanomaterials have attracted increasing attention as an alternative to enzymes due to their superior catalytic activity. In this study, we report a coreduction synthesis of gold–copper (Au–Cu) alloy nanoparticles in aqueous phase. By controlling the amount of Au and Cu precursors, the Au/Cu molar ratio of the nanoparticles can be tuned from 1/0.1 to 1/2. The synthesized Au–Cu alloy nanoparticles show good peroxidase-like catalytic activity and high selectivity for the H2O2-mediated oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB, colorless) to TMB oxide (blue). The Au–Cu nanoparticles with an Au/Cu molar ratio of 1/2 exhibit high catalytic activity in the H2O2 colorimetric detection, with a limit of detection of 0.141 μM in the linear range of 1–10 μM and a correlation coefficient R2 = 0.991. Furthermore, the Au–Cu alloy nanoparticles can also efficiently detect glucose in the presence of glucose oxidase (GOx), and the detection limit is as low as 0.26 μM.

Multi-metallic Pd@FePt core&ndash, shell nanoparticles were synthesized using a direct seed-mediated growth method, consisting of facile and mild procedures, to increase yield. The Fe/Pt ratio in the shell was easily controlled by adjusting the amount of Fe and Pt precursors. Furthermore, compared with commercial Pt/C catalysts, Pd@FePt nanoparticles exhibited excellent activity and stability toward the methanol oxidation reaction (MOR), making them efficient in direct methanol fuel cells (DMFC).

In this study we developed a dual therapeutic metal ion-releasing nanoparticle for advanced osteogenic differentiation of stem cells. In order to enhance the osteogenic differentiation of human mesenchymal stem cells (hMSCs) and induce angiogenesis, zinc (Zn) and iron (Fe) were synthesized together into a nanoparticle with a pH-sensitive degradation property. Zn and Fe were loaded within the nanoparticles to promote early osteogenic gene expression and to induce angiogenic paracrine factor secretion for hMSCs. In vitro studies revealed that treating an optimized concentration of our zinc-based iron oxide nanoparticles to hMSCs delivered Zn and Fe ion in a controlled release manner and supported osteogenic gene expression (RUNX2 and alkaline phosphatase) with improved vascular endothelial growth factor secretion. Simultaneous intracellular release of Zn and Fe ions through the endocytosis of the nanoparticles further modulated the mild reactive oxygen species generation level in hMSCs without cytotoxicity and thus improved the osteogenic capacity of the stem cells. Current results suggest that our dual ion releasing nanoparticles might provide a promising platform for future biomedical applications.

Cell therapy based on human adipose derived stem cells (hADSCs) is a known potential therapeutic approach to induce angiogenesis in ischemic diseases. However, the therapeutic efficacy of direct hADSC injection is limited by a low cell viability and poor cell engraftment after administration. To improve the outcomes of this kind of approach, various types of nanoparticles have been utilized to improve the therapeutic efficacy of hADSC transplantation. Despite their advantages, the adverse effects of nanoparticles, such as genetic damage and potential oncogenesis based on non-degradable property of nanoparticles prohibit the application of nanoparticles toward the clinical applications. Herein, we designed a transition metal based inorganic nanocluster able of pH-selective degradation (ps-TNC), with the aim of enhancing an hADSC based treatment of mouse hindlimb ischemia. Our ps-TNC was designed to undergo degradation at low pH conditions, thus releasing metal ions only after endocytosis, in the endosome. To eliminate the limitations of both conventional hADSC injection and non-degradable property of nanoparticles, we have collected conditioned medium (CM) from the ps-TNC treated hADSCs and administrated it to the ischemic lesions. We found that intracellular increment of transition metal ion upregulated the hypoxia-inducible factor 1α, which can induce vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) expressions. Based on the molecular mechanism, the secretion of VEGF and bFGF by ps-TNC treated hADSCs showed a significant improvement compared to that of untreated cells. Injecting the CM collected from ps-TNC treated hADSCs into the mouse hindlimb ischemia model (ps-TNC-CM group) showed significantly improved angiogenesis in the lesions, with improved limb salvage and decreased muscle degeneration compared to the group injected with CM collected from normal hADSCs (CM group). This study suggests a novel strategy, combining a known angiogenesis molecular mechanism with both an improvement on conventional stem cell therapy and the circumvention of some limitations still present in modern approaches based on nanoparticles.

The selective enhancement of catalytic activity is a challenging task, as catalyst modification is generally accompanied by both desirable and undesirable properties. For example, in the case of the direct synthesis of hydrogen peroxide, Pt on Pd improves hydrogen conversion, but lowers hydrogen peroxide selectivity, whereas Au on Pd enhances hydrogen peroxide selectivity but decreases hydrogen conversion. Toward an ideal catalytic property, the development of a catalyst that is capable of improving H-H dissociation for increasing H2 conversion, whilst suppressing O-O dissociation for high H2O2 selectivity would be highly beneficial. Pd-core AuPt-bimetallic shell nanoparticles with a nano-sized bimetallic layer composed of Au-rich or Pt-rich content with Pd cubes were readily prepared via the direct seed-mediated growth method. In the Pd-core AuPt-bimetallic shell nanoparticles, Au was predominantly located on the {100} facets of the Pd nanocubes, whereas Pt was deposited on the corners of the Pd nanocubes. The evaluation of Pd-core AuPt-bimetallic shell nanoparticles with varying Au and Pt contents revealed that Pd-core AuPt-bimetallic shell that was composed of 2.5 mol% Au and 5 mol% Pt, in relation to Pd, exhibited the highest H2O2 production rate (914 mmol H2O2 gmetal&minus, 1 h&minus, 1), due to the improvement of both H2O2 selectivity and H2 conversion.

Here, a novel, versatile synthetic strategy to fabricate a yolk-shell structured material that can encapsulate virtually any functional noble metal or metal oxide nanocatalysts of any morphology in a free suspension fashion is reported. This strategy also enables encapsulation of more than one type of nanoparticle inside a single shell, including paramagnetic iron oxide used for magnetic separation. The mesoporous organosilica shell provides efficient mass transfer of small target molecules, while serving as a size exclusion barrier for larger interfering molecules. Major structural and functional advantages of this material design are demonstrated by performing three proof-of-concept applications. First, effective encapsulation of plasmonic gold nanospheres for localized photothermal heating and heat-driven reaction inside the shell is shown. Second, hydrogenation catalysis is demonstrated under spatial confinement driven by palladium nanocubes. Finally, the surface-enhanced Raman spectroscopic detection of model pollutant by gold nanorods is presented for highly sensitive environmental sensing with size exclusion.

In order to accurately analyze how the surfactant attached on the surface of the nanoparticles affects the catalytic activity, all other experimental conditions should be maintained except the surfactant. In this study, we control the hydrocarbon chain length of the alkylamine and carboxylic acid on the surface of manganese oxide (Mn3O4) nanoparticles while keeping their size and shape using a reverse micelle method. Despite the use of various lengths of surfactants, the size and shape of the synthesized nanoparticles remain virtually unchanged. After the mild heattreatment, they have different secondary particle morphologies even though the nano particles are preserved. Those prepared nanoparticles exhibit the characteristics voltage behavior under the galvanostatic charge and discharge. The obtained electrochemical performances are influenced by the surfactants. A coin cell having Mn3O4 nanoparticles coated by hexanoic acid and hexylamine shows the highest capacity than the other samples.

Copper sulfide (Cu7S4) nanoparticles were synthesized by adding ethanolic elemental sulfur solution to an aqueous solution containing Cu(II) precursor, branched polyethyleneimine (BPEI), and ascorbic acid. By varying the Cu(II) precursor used, we could control the morphology of the nanoparticles produced to be either quasi spherical (CuF2, Cu(NO3)2, and CuSO4) or vine like nanofibers (CuCl2 and CuBr2). By comparing experimental results and conducting calculations we found that selective adsorption of Br− and Cl− onto specific crystal facets and slowing of the reaction rate owing to formation of Cu(I)–anion–BPEI complexes explain the observed change in morphology from spherical particles to vine like nanofibers. We also found that the differences in morphology of Cu7S4 nanoparticles affects the electrochemical performance of Li batteries including the nanoparticles as electrode materials.

In this report, a continuous stirring tank reactor (CSTR) and batch reactor were used for synthesis of silver (Ag) plates. The influences of agitation speed, molar ratio of AgNO3 to NaCl, and concentration of reagent were investigated. Size analysis demonstrated that the size of Ag plates synthesized by the CSTR was larger than the size of plates synthesized by the batch reactor. The reason might be that low concentration of reagent and continuous supply of monomer in CSTR are more favorable for growth of anisotropic structures. CSTR demonstrates good advantages for mass synthesis of Ag plates of large size.

A customized droplet-based microfluidic reactor was fabricated for the synthesis of silver nanoparticles (Ag NPs) using silver nitrate (AgNO3) and branched polyethyleneimine (BPEI) as a precursor and a reducing agent, respectively. The effects of static mixing, temperature, and the volumetric flow rates of AgNO3 and BPEI on the particle size were investigated. The use of a static mixer and the optimization of the reaction temperature enhanced the monodispersity of the Ag NPs. In addition, the size of the Ag NPs was manipulated by changing the flow rate ratio of AgNO3 to BPEI at 60 °C for 60 min.

We successfully synthesized metal hydroxide (Ni(OH)2 and Co(OH)2) nanoplates and platinum/nickel hydroxide hybrid nanostructures (Pt/Ni(OH)2) in an aqueous solution. Transmission electron microscopy studies of the Pt/Ni(OH)2 hybrid nanostructures revealed that a number of 3 nm-sized Pt nanoparticles were well dispersed on the surface of each Ni(OH)2 nanoplate. The Pt/Ni(OH)2 hybrid nanostructures exhibited enhanced electrocatalytic properties due to synergetic effect of Ni(OH)2 and Pt.

Synthesis of magnetite nanocrystals typically requires harsh reaction conditions, including high reaction pressures and/or temperatures, to obtain morphology-controlled nanocrystals like cubic magnetite nanocrystals. We report the synthesis of cubic magnetite nanocrystals with a size of 9 nm at reaction temperatures less than 100 °C in air. The synthesized magnetite nanocubes exhibited uniform size and highly crystalline nature. In addition, we synthesized size-controlled spherical magnetite nanocrystals in the size range of 2.5 nm to 9 nm by modifying the reaction conditions.

We report the external field-guided shape transformation of magnetite-polymer composite particles that play multiple roles in heterogeneous chemical reactions, such as catalysts, catalyst supports, and micro-stirrers. A microfluidic method was used to generate monodispersed emulsion droplets composed of polystyrene, magnetite nanoparticles (MNPs), and chloroform. While the solvent in the droplets was dried in the presence of an external magnetic field, the emulsion droplets were deformed or elongated along the field direction, consequently leading to magnetically responsive particles with anisotropic shape after complete removal of the solvent. Coarse-grained molecular dynamic simulations demonstrated that the shape deformation was due to destabilization of the MNPs upon solvent drying and migration of the aggregated MNPs in the polymer matrix along the external field. The particle shape could be readily tunable by modulating the field strength and direction as well as the concentrations of the MNPs and polymer. We further revealed that these magnetic anisotropic particles coated with palladium nanoparticles could be used as catalysts, catalyst supports, micro-stirrers when the particles were dispersed in a small confined volume of a catalytic precursor solution.

As a joint investigation principle using experimental and theoretical approaches, we report that the anisotropic growth of Pt on Pd nanocubes significantly promotes the direct synthesis of hydrogen peroxide (H2O2) from hydrogen (H2) and oxygen (O2). The superior H2O2 productivity of the anisotropic Pd@Pt core@shell nanocrystals results from the enhanced H2 conversion and the H2O2 selectivity compared to Pd and Pt. From the joint investigation, during the anisotropic growth of the Pd@Pt nanocrystals, high-index facets such as (2 1 0) are generated, and they provide numerous active sites for hydrogen dissociation. Notably, even the nano-catalyst is enclosed by Pt shell, the high-index facets are favorable for opening a new route for hydrogen dissolution into the Pd bulk lattices of the Pd@Pt nanocrystals, in which the dissolved hydrogen can react with chemisorbed O2 over the nanocrystals to form H2O2. This mechanism is suggested by a hydrogen temperature programmed reduction (H2-TPR) analysis, in situ transmission electron microscopy (TEM), and density functional theory (DFT) calculations. This study provides another option to improve the catalytic performance of core@shell nanocrystals via the generation of high-index facets through anisotropic growth of nanocrystals, in addition to the well-known strain and charge transfer effects. We expect that the anisotropic growth approach could be extended to other catalytic reactions.

Metal and oxide nanoparticles (NPs) are attracting extensive attention in biomedical applications, including bioimaging and drug delivery. However, it is difficult to use these NPs as therapeutic agents for specific cell and tissue treatments because of limitations such as material oxidization and cell toxicity. Herein, we synthesized Cu-based angiogenic metal nanoparticles (Cu-AMNs), using a galvanic replacement reaction of Cu NPs and Au precursor, which stabilized and upregulated intracellular behaviors in human adipose-derived stem cells (hADSCs). Our novel therapeutic Cu-AMNs showed remarkable advantages in cell treatment, such as low mitochondrial damage, reduced ATP consumption, decreased cytotoxicity, mild reactive oxygen species generation with enhanced angiogenic paracrine factor secretion, and improved hypoxia inducible factor-1 alpha (HIF-1α) expression. Through the improved expression of HIF-1α, vascular endothelial growth factor (VEGF) secretion was prolonged for 3 days, even in re-attached hADSCs. In addition, Cu-AMNs improved other angiogenic factors and the amount of exocytosed Cu from hADSCs, resulting in strong development of tubular formation by human umbilical vein endothelial cells in vitro. Finally, transplantation of Cu-AMN-treated hADSCs in mice led to a significant in vivo increase in angiogenesis and blood perfusion in a mouse hindlimb ischemia model compared with conventional hADSC therapy.

Uniform silica particles were synthesized by synergistic combination of sodium 4-styrene sulfonate (NaSS) anionic surfactant and organic amine base catalyst such as ethylenediamine (EDA) or diethylenetriamine (DETA). The EDA and DETA organic amine base catalysts could promote the growth reaction rate so that they produced larger silica particles compared to the NH4OH base catalyst because the organic amines provide more basic micro-environment near the surface of the silica particle due to multiple amine groups in a single molecule. Accordingly, the size of the silica particle was 450 ± 12 nm (NH4OH), 725 ± 21 nm (EDA), and 942 ± 130 nm (DETA) in similar pH conditions.

We report a facile aqueous-phase synthetic route to vine-like copper sulfide (CuS) nanofibers prepared by reacting elemental sulfur with Cu+-branched polyethyleneimine (BPEI) complex obtained by the reaction of Cu2+ with ascorbic acid in the presence of BPEI. By controlling the concentration of BPEI, we could easily control the morphology of CuS from nanofibers to hollow nanoparticles. We also found that concentration of BPEI and the presence of halide anion would play important roles in the formation of vine-like CuS nanofibers.

Injecting human mesenchymal stem cells (hMSCs) at wound sites is known to have a therapeutic effect, however, hMSCs have several limitations, such as low viability and poor engraftment after injection, as well as a potential risk of oncogenesis. The use of a conditioned medium (CM) was suggested as an alternative method for treating various wounds instead of direct hMSC administration. In addition to not having the adverse effects associated with hMSCs, a CM can be easily mass produced and can be stored for long-term, thereby making it useful for clinical applications. In general, a CM is collected from hMSCs with low passage number, whereas, the hMSCs with high passage number are usually discarded because of their low therapeutic efficacy as a result of reduced angiogenic factor secretion. Herein, we used a CM collected from high passage number (passage 12, P12) hMSCs treated with gold-iron nanoparticles (AuFe NPs). Our AuFe NPs were designed to release the iron ion intracellularly via endocytosis. Endosomes with low pH can dissolve iron from AuFe NPs, and thus, the intracellularly released iron ions up-regulate the hypoxia-inducible factor 1&alpha, and vascular endothelial growth factor (VEGF) expression. Through this mechanism, AuFe NPs improve the amount of VEGF expression from P12 hMSCs so that it is comparable to the amount of VEGF expression from low passage number (passage 6, P6), without treatment. Furthermore, we injected the CM retrieved from P12 MSCs treated with AuFe NPs in the mouse skin wound model (AuFe P12 group). AuFe P12 group revealed significantly enhanced angiogenesis in the mouse skin wound model compared to the high passage hMSC CM-injected group. Moreover, the result from the AuFe P12 group was similar to that of the low passage hMSC CM-injected group. Both the AuFe P12 group and low passage hMSC CM-injected group presented significantly enhanced re-epithelization, angiogenesis, and tissue remodeling compared to the high passage hMSC CM-injected group. This study reveals a new strategy for tissue regeneration based on CM injection without considering the high cell passage count.

One of the challenges of using nanoparticles as catalysts is the presence of reaction-disturbing stabilizers that surround the nanoparticle surface. In this report, we demonstrate a method to synthesize stabilizer-free bismuth oxychloride (BiOCl) nanoparticles to increase photocatalytic activity. This synthesis method is remarkably simple, involving only BiCl3 and deionized water. After heating an aqueous solution containing BiCl3, plate-shaped BiOCl nanoparticles were formed. The stabilizer-free BiOCl nanoplates exhibited higher photocatalytic activities compared to polyvinylpyrrolidone- and polyethyleneimine-stabilized nanoplates for the degradation of methylene blue.

We describe a facile synthetic route to α-Co(OH)2 nanostructures by heating a solution containing CoCl2, ethylene glycol, and oleylamine. Electron microscopy and X-ray diffraction analyses revealed that flower-like nanostructures of α-Co(OH)2 were formed by assembly of thin α-Co(OH)2 nanosheets. These nanostructures exhibited high activity for electrochemical water splitting with a current density comparable to that obtained on the commercial Pt wire electrode. In addition, these flower-like α-Co(OH)2 nanostructures showed specific capacitance as high as 440 F/g at a current density of 1 A/g and excellent stability without any noticeable loss in capacitance after 5000 cycles of the galvanostatic charge–discharge test.

We investigated the effect of Fe3O4 nanoparticle orientation on the magnetic properties of hybrid polymer nanocomposite thin films. A multilayer thin film consisting of alternating layers of polymers and assembled iron oxide nanoparticles was prepared by spin coating and Langmuir–Blodgett techniques. Transmission electron microscopy and neutron reflectivity measurements were employed to determine structural information related to the lateral orientation of the Fe3O4 nanoparticle monolayer and the layered architecture along the depth of the multilayer, respectively. The magnetic properties of the hybrid multilayer were characterized by SQUID magnetometry and compared with the properties of a spin-coated polymer nanocomposite thin film containing homogenously dispersed Fe3O4 nanoparticles. We found that the closely-packed monolayer structure of the Fe3O4 nanoparticles changed the magnetic properties on account of the dipolar interactions between particles, whereas the homogeneously-dispersed nanoparticles embedded in the polymer matrix exhibited zero remanent magnetization and coercivity due to isolation of the nanoparticles and lack of dipolar interactions.

Flower-like shaped rutile-rich TiO 2 nanoparticles were synthesized by the reaction of HCl with titanium diisopropoxide bis(acetylacetonate) immobilized in reverse micelles composed of oleic acid, water, and xylene. Brunauer Emmett Teller (BET) analysis showed large surface area of the synthesized TiO 2 nanoparticles of 177.8 m 2 /g. We investigated the effect of the concentration of Ti precursor and role of oleic acid in the formation of TiO 2 nanoparticles. Rutile-rich TiO 2 nanoparticles with large surface area showed better photocatalytic activity in decomposing methyl orange under visible-light irradiation than anatase and rutile mixed phase TiO 2 particles.

Here, we report a simple and fast synthetic route to Ag/AgBr hybrid nanostructures prepared by reducing AgBr nanoparticles synthesized by the reaction of Ag+ with Br− in the presence of polyethyleneimine (PEI). By controlling the experimental conditions including reaction temperature and amount of reducing agent, we could easily control the morphology and composition of a variety of Ag/AgBr hybrid nanostructures including Ag nanoparticles decorated with AgBr nanoparticles and hollow cage-like Ag-rich nanostructures. The Ag/AgBr hybrid nanostructures exhibited enhanced photocatalytic activity and recyclability for decomposing methylene blue (MB) under visible-light illumination because of a small bandgap (2.6 eV) and strong SPR effect. In particular, we found that the Ag/AgBr hybrid nanostructures showed a photocatalytic reaction rate that was 1000 times faster than commercial TiO2 (P-25). In addition, the Ag/AgBr hybrid nanostructures had a higher photocatalytic activity compared to Ag/AgCl hybrid nanostructures towards the decomposition of methyl orange (MO) under visible light illumination.

A continuous and defect-free ZIF-8 membrane was successfully grown on a positive surface curvature of a porous tubular alumina support that was prepared from zinc nitrate precursor solution at 120 °C for 4 h of synthesis time. The membrane produced the highest propylene permeation of 198 × 10−10 mol⋅m−2⋅s−1⋅Pa−1 and moderate separation factor of 48. Despite its modest level of separation factor, the membrane was able to enrich propylene from 50 vol%. to 98 vol% from a binary feed mixture containing equal flowrate of propylene and propane. The high purity however came with low propylene recovery of merely 5% because there was a trade-off between the separation factor and permeance as a result of an inversed relationship between the two.

The synthesis of Pd@Pt core&ndash, shell nanocubes was achieved through a direct seed-mediated growth method. This process represents a simple and cost-effective way to produce core&ndash, shell nanocubes. The morphology of the Pd@Pt core&ndash, shell nanocubes varied from simple cubic to concave cubic, depending on the reducing agent and the Pt content. The selection of the reducing agent is important because the reduction rate is directly related to the shell growth. The catalytic activity and stability of the Pd@Pt core&ndash, shell nanocubes in the methanol oxidation reaction were different for the nanocubes with partial and full Pt shells.

Renewable energy harvesting technologies have been actively studied in recent years for replacing rapidly depleting energies, such as coal and oil energy. Among these technologies, the triboelectric nanogenerator (TENG), which is operated by contact-electrification, is attracting close attention due to its high accessibility, light weight, high shape adaptability, and broad applications. The characteristics of the contact layer, where contact electrification phenomenon occurs, should be tailored to enhance the electrical output performance of TENG. In this study, a portable imprinting device is developed to fabricate TENG in one step by easily tailoring the characteristics of the polydimethylsiloxane (PDMS) contact layer, such as thickness and morphology of the surface structure. These characteristics are critical to determine the electrical output performance. All parts of the proposed device are 3D printed with high-strength polylactic acid. Thus, it has lightweight and easy customizable characteristics, which make the designed system portable. Furthermore, the finger tapping-driven TENG of tailored PDMS contact layer with microstructures is fabricated and easily generates 350 V of output voltage and 30 &mu, A of output current with a simple finger tapping motion-related biomechanical energy.

Transition metal layered double hydroxide (LDH) nanomaterials have been considered as good catalytic materials for various applications; however, there has been a limit in the economic efficiency and convenience of the synthetic method. In this work, we report a facile aqueous-phase route to the synthesis of transition metal LDH nanoplates including Mn-Ni and Zn-Ni. Electrochemical characterization of the synthesized Mn-Ni LDHs with different intercalated halogen anions was carried out for the oxygen evolution reaction (OER) and a Tafel slope of about 80 mV per decade was obtained which is comparable to those of the previously reported LDH nanoplates.

Adipose-derived stem cells (ADSCs) have the potential to treat ischemic diseases. In general, ADSCs facilitate angiogenesis by secreting various pro-angiogenic growth factors. However, transplanted ADSCs have a low therapeutic efficacy in ischemic tissues due to their poor engraftment and low viability. Stromal cell-derived factor-1α (SDF-1α) improves the survival rate of stem cells transplanted into ischemic regions. In this study, we developed acid-degradable poly(ethylene glycol)-poly(amino ketal) (PEG-PAK)-based micelles for efficient intracellular delivery of SDF-1α plasmid DNA. The SDF-1α gene was successfully delivered into human ADSCs (hADSCs) using PEG-PAK micelles. Transfection of SDF-1α increased SDF-1α, vascular endothelial growth factor, and basic fibroblast growth factor gene expression and decreased apoptotic activity in hADSCs cultured under hypoxic conditions in comparison with conventional gene transfection using polyethylenimine. SDF-1α-transfected hADSCs also showed significantly increased SDF-1α and VEGF expression together with reduced apoptotic activity at 4 weeks after transplantation into mouse ischemic hindlimbs. Consequently, these cells improved angiogenesis in ischemic hindlimb regions. These PEG-PAK micelles may lead to the development of a novel therapeutic modality for ischemic diseases based on an acid-degradable polymer specialized for gene delivery.

The carboxy-terminal domain (CTD) of RNA polymerase (Pol) II is an intrinsically disordered low-complexity region that is critical for pre-mRNA transcription and processing. The CTD consists of hepta-amino acid repeats varying in number from 52 in humans to 26 in yeast. Here we report that human and yeast CTDs undergo cooperative liquid phase separation, with the shorter yeast CTD forming less-stable droplets. In human cells, truncation of the CTD to the length of the yeast CTD decreases Pol II clustering and chromatin association, whereas CTD extension has the opposite effect. CTD droplets can incorporate intact Pol II and are dissolved by CTD phosphorylation with the transcription initiation factor IIH kinase CDK7. Together with published data, our results suggest that Pol II forms clusters or hubs at active genes through interactions between CTDs and with activators and that CTD phosphorylation liberates Pol II enzymes from hubs for promoter escape and transcription elongation.

We report the colloidal synthesis of rare earth oxide nanoplates with square and disk shapes using thermal decomposition of Ln(CH3CO2)3·xH2O in the presence of a mixture of oleylamine and oleic acid (Ln=La, Pr, Nd, Dy, Er, and Y). In this synthesis, oleylamine plays an important role in the formation of ultra-thin nanoplates with thickness of 1.1 nm, which corresponds to a single unit cell dimension of rare earth oxides, and oleic acid serves as a capping agent for the formation of nanoplates having nano-sized side dimension (around 15-40 nm). By varying the rare earth precursors, we obtained square-shaped nanoplates (La2O3, Pr2O3, and Nd2O3) and disk-shaped nanoplates (Dy2O3, Er2O3, and Y2O3), respectively, confirming that our synthesis could be extended to the synthesis of various rare earth oxide nanoplates.

The hydrothermal decomposition of sodium alginate was analyzed in subcritical water as a function of pH in order to investigate the effects of catalysts on the production of value-added chemicals. A base-catalysed reaction at pH 13 promoted the decomposition of alginate, resulting in the production of lactic acid, fumaric acid and malic acid as major species. At pH 1, monomers (mannuronic acid and guluronic acid), furfural and glycolic acid were predominantly produced by the acid-catalysed hydrothermal decomposition of alginate. Increasing the reaction temperature enhanced both the acid- and base-catalysed reactions, albeit by varying degrees dependent upon the catalyst type. Our results demonstrate that optimizing the reaction temperature and pH is critical for the efficient conversion of seaweed-derived biomass into valuable products.

Synthesizing Cu nanocrystals with tunable sizes in the sub-100 nm regime and good uniformity is essential for their applications in microelectronics. In this paper, we demonstrate a facile and scalable synthetic route to uniform Cu nanocrystals with tunable sizes in the range of 20–100 nm based on an ethylene glycol (EG)-assisted synthetic method with appropriate alkylamine and fatty acid as surfactant and co-surfactant, respectively. In this approach, the size of Cu nanocrystals could be readily controlled by varying alkyl chain length of alkylamine, fatty acid, or both. We also demonstrate that these Cu nanocrystals can be successfully applied to the fabrication of solution-processed electrodes for organic field-effect transistors with reasonably high hole mobility.

We describe a simple, aqueous-phase route to the synthesis of metal nanoparticles including Pt, Pd, Ru, and Au based on the aqueous-phase reduction of metal salts with NaBH4. In this approach, various phosphates were applied as new type of stabilizers for the synthesis of metal nanoparticles thanks to its negatively charged functional group (PO−).

Colloidal nanosheets of nickel-manganese layered double hydroxides (LDHs) have been synthesized in high yields through a facile reverse micelle method with xylene as an oil phase and oleylamine as a surfactant. Electron microscopy studies of the product revealed the formation of colloidal nanoplatelets with sizes of 50-150 nm, and X-ray diffraction, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy studies showed that the Ni-Mn LDH nanosheets had a hydrotalcite-like structure with a formula of [Ni3 Mn(OH)8 ](Cl(-) )⋅n H2 O. We found that the presence of both Ni and Mn precursors was required for the growth of Ni-Mn LDH nanosheets. As pseudocapacitors, the Ni-Mn LDH nanosheets exhibited much higher specific capacitance than unitary nickel hydroxides and manganese oxides.

We report a synthetic method for small and uniform Fe3O4 (magnetite) nanoparticles under mild conditions. Spherical sub-3 nm-sized magnetite nanoparticles were prepared via reverse micelles composed of oleylamine, F127, xylene, and water for the reaction of iron(III) stearate with hydrazine at a reaction temperature of 90 &deg, C in air atmosphere. These synthesized magnetite nanoparticles exhibited good size uniformity. By controlling experimental conditions, we could easily control both size and size uniformity of these magnetite nanoparticles. We further investigated whether Fe3O4 could be used in biomedical applications. Cytotoxicity of Fe3O4 was evaluated with human adipose-derived stem cells (hADSCs). Our results showed that the number of hADSCs did not significantly decrease when these cells were treated with Fe3O4 nanoparticles at a concentration of up to 9 &mu, g/mL. Apoptotic activity and cell proliferation of hADSCs treated with Fe3O4 nanoparticles were similar to those of hADSCs without any treatment. This novel method could be used for synthesizing uniform and biocompatible Fe3O4 nanoparticles with further biomedical applications.

This paper describes a simple route to synthesis of water-dispersible monodisperse maghemite () nanocrystals using 6-aminohexanoic acid (AHA) as a stabilizer. The water-dispersible nanocrystals with an average size of 5 nm were obtained simply by addition of into an octyl ether solution containing AHA at under argon condition. As-prepared AHA coated nanocrystals exhibited highly crystallinity and magnetic property while keeping a good dispersity in an aqueous phase. We also obtained water-dispersible AHA coated nanocrystals using ligand-exchange method, demonstrating that AHA can be a good candidate for preparing water-dispersible uniform metal oxide nanocrystals.

This letter describes a simple and bulk route for synthesizing Au nanoparticles in a sub-10 nm regime using branched polyethyleneimine (BPEI) as a stabilizer. BPEI, a sterically hindered functional polymer, was found to play a key role in stabilizing the Au nanoparticles without any aggregation, even at a high chloroauric acid concentration of 200 mM.

A systematic study was conducted on small Pd nanocrystals (5–6 nm) to understand the effects of catalyst structure and electrolyte on the oxygen reduction reaction (ORR) and formic acid oxidation (FAO). The ORR activities of Pd catalysts strongly depended on their structure and the electrolyte used. It was found that Pd cubes were 10 times more active than Pd octahedra for ORR in an aqueous HClO4 solution due to higher onset potential of OHad formation on the cubic surface. In the case of a H2SO4 solution, the ORR activity of Pd cubes was 17 times higher than that of Pd octahedra due to the stronger adsorption of (bi)sulfate on the surface of octahedral nanocrystals in addition to OHad. In alkaline solutions, however, no structure dependence was observed for ORR due to the outer-sphere electron-transfer mechanism in the potential region for Pd oxide formation. For FAO, no advantage was observed on shape-controlled Pd nanocrystals in comparison to conventional Pd catalysts. The FAO current densities, both ...

This paper describes a simple and fast aqueous-phase route to the synthesis of Ag/AgCl hybrid nanostructures. These hybrid nanostructures were synthesized by reduction of AgCl nanoparticles with controlled shapes prepared by reacting Ag(+) with Cl(-) in the presence of polyethyleneimine (PEI) in an aqueous-phase. We could easily control the morphology and composition of the nanostructures by varying the experimental conditions, including the reaction temperature and the amount of the reducing agent. The as-synthesized Ag/AgCl hybrid nanostructures exhibited enhanced photocatalytic activity and stability during the degradation of methyl orange under visible light irradiation because of their strong surface plasmon resonance (SPR) effect.

Noble-metal nanocrystals with well-defined and controllable morphologies are of great importance to applications in catalysis, plasmonics, and surface-enhanced spectroscopy. Many synthetic approaches have been demonstrated for controlling the growth habit and thus morphology of metal nanocrystals, but most of them are based on a thermodynamic approach, including the use of a capping agent. While thermodynamic control has shown its power in generating nanocrystals with a myriad of different morphologies, it is ultimately limited by the obligation to minimize the surface energy of a system. As a result, it is impractical to use thermodynamic control to generate nanocrystals having high-energy facets and/or a negative curvature. Using rhodium as an example, here we demonstrate a general method based on kinetic control with a syringe pump that can be potentially extended to other noble metals and even other solid materials. For the first time, we were able to produce concave nanocubes with a large fraction of {110} facets and octapods with a cubic symmetry in high yields by simply controlling the injection rate at which the precursor was added into the reaction solution. The concave nanocubes with {110} facets and a unique cavity structure on the surface are important for a variety of applications.

The nanoparticle (NP) synthesis undergoes stepwise processes starting from the input metal ions: nucleation, coalescence, ripening, and growth. Considering the whole process is completed in a very short time, the conventional flask-scale method, which requires at least minutes, is not adequate to trace the mechanism of NP nucleation. In this study, a microfluidic droplet generator is developed, which is capable of in situ sol-gel polymerization for synthetic reaction quenching. As a model, palladium (Pd) NPs are synthesized within microdroplets, and the reaction time is controlled by tuning the length of the microchannel. In the microfluidic design, the outmost microchannel is incorporated, in which tetraethyl orthosilicate (TEOS) dissolved in ethanol is injected. The generated droplets are merged to the outmost flow under the variety of time interval (50 to 5,000 ms), so that the tens of milliseconds observation on NP nucleation is conducted via flash-like sol-gel quenching. Based on the result analysis, the seeds of Pd NPs have undergone slight size fluctuation and then a thermodynamically stable aggregation/coalescence step within 5 s before moving into the growth stage. This microfluidic platform permits the study of the fundamental and initial stage of the NP synthesis, which cannot be approached by the conventional methodology.

We report a novel and facile method for the synthesis of manganese oxide (Mn3O4) nanocrystals with various sizes and shapes. Mn3O4 nanocrystals were synthesized via a reaction of manganese(II) acetate with water in xylene in the presence of surfactants at the temperature of as low as 90 °C in air atmosphere. Structural characterizations revealed that the synthesized nanocrystals were tetragonal Mn3O4 structure and that they were highly crystalline in spite of the low reaction temperature. The size and shape of the nanocrystals were readily controlled by varying the experimental conditions such as precursors, surfactants, and injection temperature of water. Nanoplates with a thickness of 5 nm and side dimensions of 9, 15, and 22 nm were synthesized using oleylamine as the surfactant. When carboxylic acid was used as the cosurfactant along with oleylamine, spherical nanocrystals were obtained with sizes of 5.5, 6.2, 7.2, 8.5, and 15 nm. Interesting anisotropic nanostructures including nanowires and nanokite...

Ceria nanocrystals with a cube shape were synthesized from the hydrolytic sol–gel reaction of cerium salt in the presence of oleylamine. The overall synthetic process is very simple and readily applicable to the large-scale synthesis of tens of grams of product in a single reaction in air. These ceria nanocrystals are readily dispersible in aqueous media without the addition of any extra dispersing agent. The aqueous dispersion of the ceria nanocrystals was successfully used as a chemical mechanical polishing slurry, and it exhibited high removal selectivity between silicon oxide and silicon nitride at pH 7.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

Uniformly sized silica-coated magnetic nanoparticles (magnetite@silica) are synthesized in a simple one-pot process using reverse micelles as nanoreactors. The core diameter of the magnetic nanoparticles is easily controlled by adjusting the w value ([polar solvent]/[surfactant]) in the reverse-micelle solution, and the thickness of the silica shell is easily controlled by varying the amount of tetraethyl orthosilicate added after the synthesis of the magnetite cores. Several grams of monodisperse magnetite@silica nanoparticles can be synthesized without going through any size-selection process. When crosslinked enzyme molecules form clusters on the surfaces of the magnetite@silica nanoparticles, the resulting hybrid composites are magnetically separable, highly active, and stable under harsh shaking conditions for more than 15 days. Conversely, covalently attached enzymes on the surface of the magnetite@silica nanoparticles are deactivated under the same conditions.

A simple and fast synthetic route to ultra-highly concentrated silver nanoparticles with long-term stability by reducing AgNO3 with ascorbic acid in the presence of polyethyleneimine (PEI) as a stabilizer in an aqueous phase is reported. The concentration of silver precursor was as high as 2000 mm (200 g of Ag nanoparticle per liter of water) and the reaction time was less than 10 min. The resulting silver nanoparticles show long-term stability after two months of storage at room temperature without any signs of particle aggregation or precipitation in an aqueous phase. The successful ligand exchange of PEI-stabilized silver nanoparticles to polyethylene glycol (PEG) and polyvinylpyrrolidone (PVP) without particle aggregation is also demonstrated. In addition, the catalytic activities of silver nanoparticles stabilized by various stabilizers prepared by the ligand exchange method was investigated. The PEI-stabilized silver nanoparticles exhibited a higher stability than those of PEG- and PVP-stabilized silver nanoparticles in the diffusion-controlled catalytic reduction of 4-nitrophenol to 4-aminophenol by NaBH4 .