Azide-Alkyne Huisgen [3+2] Cycloaddition Using CuO Nanoparticles

Recent developments in the synthesis of CuO nanoparticles (NPs) and their application to the [3+2] cycloaddition of azides with terminal alkynes are reviewed. With respect to the importance of click chemistry, CuO hollow NPs, CuO hollow NPs on acetylene black, water-soluble double-hydrophilic block copolymer (DHBC) nanoreactors and ZnO-CuO hybrid NPs were synthesized. Non-conventional energy sources such as microwaves and ultrasound were also applied to these click reactions, and good catalytic activity with high regioselectivity was observed. CuO hollow NPs on acetylene black can be recycled nine times without any loss of activity, and water-soluble DHBC nanoreactors have been developed for an environmentally friendly process.open6

Metal Hybrid Nanoparticles for Catalytic Organic and Photochemical Transformations

In order to understand heterogeneous catalytic reactions, model catalysts such as a single crystalline surface have been widely studied for many decades. However, catalytic systems that actually advance the reactions are three-dimensional and commonly have multiple components including active metal nanoparticles and metal oxide supports. On the other hand, as nanochemistry has rapidly been developed and been applied to various fields, many researchers have begun to discuss the impact of nanochemistry on heterogeneous catalysis. Metal hybrid nanoparticles bearing multiple components are structurally very close to the actual catalysts, and their uniform and controllable morphology is suitable for investigating the relationship between the structure and the catalytic properties in detail.In this Account, we introduce four typical structures of metal hybrid nanoparticles that can be used to conduct catalytic organic and photochemical reactions. Metal@silica (or metal oxide) yolk-shell nanoparticles, in which metal cores exist in internal voids surrounded by thin silica (or metal oxide) shells, exhibited extremely high thermal and chemical stability due to the geometrical protection of the silica layers against the metal cores. The morphology of the metal cores and the pore density of the hollow shells were precisely adjusted to optimize the reaction activity and diffusion rates of the reactants. Metal@metal oxide core-shell nanoparticles and inverted structures, where the cores supported the shells serving an active surface, exhibited high activity with no diffusion barriers for the reactants and products. These nanostructures were used as effective catalysts for various organic and gas-phase reactions, including hydrogen transfer, Suzuki coupling, and steam methane reforming.In contrast to the yolk- and core-shell structures, an asymmetric arrangement of distinct domains generated acentric dumbbells and tipped rods. A large domain of each component added multiple functions, such as magnetism and light absorption, to the catalytic properties. In particular, metal-semiconductor hybrid nanostructures could behave as effective visible photocatalysts for hydrogen evolution and CO oxidation reactions. Resulting from the large surface area and high local concentration of the reactants, a double-shell hollow structure showed reaction activities higher than those of filled nanoparticles. The introduction of plasmonic Au probes into the Pt-CdS double-shell hollow particles facilitated the monitoring of photocatalytic hydrogen generation that occurred on an individual particle surface by single particle measurements.Further development of catalysis research using well-defined metal hybrid nanocatalysts with various in situ spectroscopic tools provides a means of maximizing catalytic performances until they are comparable to or better than those of homogeneous catalysts, and this would have possibly useful implications for industrial applications. (Chemical Equation Presented). © 2015 American Chemical Society136361sciescopu

Efficient and robust automated feature engineering

Thesis: M. Eng., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2018.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (pages 59-61).Feature engineering is the key to building highly successful machine learning models. We present AutoFE, a system designed to automate feature engineering. AutoFE generates a large set of new interpretable features by combining information in the original features. Given an augmented dataset, it discovers a set of features that significantly improves the performance of any traditional classification using an evolutionary algorithm. We demonstrate the effectiveness and robustness of our approach by conducting an extensive evaluation on 8 datasets and 5 different classification algorithms. We show that AutoFE can achieve an average improvement in predictive performance of 25.24% for all classification algorithms over their baseline performance obtained with the original features..by Hyunjoon Song.M. Eng

The Scandinavian Cooperative Advantage of Fashion : A Study of Swedish Fashion Brands

In recent years the fashion industry has experienced a high frequency of famous Creative Directors departing the companies for unknown reasons. The same problem does not seem to occur in the Scandinavian fashion industry. This study’s purpose is to explore why Scandinavia does not experience the same problem, contribute a deeper understanding of the leader-designer relationship in the Swedish fashion industry, and to examine how the Scandinavian Cooperative Advantage is applicable in the Swedish fashion industry. Three case studies were conducted at the Swedish fashion companies TRIWA, Baron and Weriseg where both leaders and designers were interviewed. The findings showed that the leaders view their designers as an essential part of the organisation but how they are prioritised depend on the situation. Further more, this study indicates that all of the studied companies have a stakeholder approach, uses a value creating strategy based on cooperation with their stakeholders, are aligned with a typical Swedish organizational culture, and has a Swedish Management Style. Thus this study indicates that the notion of Scandinavian Cooperative Advantage is applicable at the Swedish fashion industry and that this might be a factor for their success

Precise adjutment of structural anisotropy and crystallinity on metal-Fe3O4 hybrid nanoparticles and its influence on magnetic and catalytic properties

In the present study, we demonstrate the precise adjustment of the morphology and crystallinity of metal (Pd or Au)–Fe3O4 hybrid nanoparticles by reaction kinetics control. The nucleation and growth of the Fe component on the Pd surface are precisely controlled by using a mixture of capping agents, oleylamine and oleic acid. After the oxidation, the resulting Pd–Fe3O4 structures are produced as yolk–shell, irregular core–shell, and dumbbell-like NPs. Along with the morphology change, the average crystal domain size of Fe3O4 and the void gap between the metal cores and the shells are simultaneously adjusted. The crystal domain sizes of Fe3O4 directly influence the magnetic properties, and the structural arrangement of the Pd cores and the Fe3O4 shells leads to a large difference of conversion yields in the Suzuki coupling reactions. Our approach is successfully extended to other metal–Fe3O4 hybrid systems, such as those of Au and Fe3O4.11191sciescopu

Selective Growth and Structural Analysis of Regular MnO Nanooctapods Bearing Multiple High-Index Surface Facets

Although numerous morphologies of MnO nanostructures have been reported, an exact structural analysis and mechanistic study has been lacking. In the present study, the formation of regular MnO octapods was demonstrated in a simple procedure, comprising the thermal decomposition of manganese oleate. Because of their structural uniformity, an ideal three-dimensional model was successfully constructed. The eight arms protruded from the cubic center with tip angles of 38°and surface facets of {311} and {533} with rounded edges. The concentrations of oleate and chloride ions were the determining factors for the octapod formation. Selective coordination of the oleate ions to the {100} faces led to edge growth along the direction, which was then limited by the chloride ions bound to the high-index surface facets. These structural and mechanistic analyses should be helpful for understanding the complex nanostructures and for tuning their structure-related properties. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim1111sciescopu

Colloidal zinc oxide-copper(I) oxide nanocatalysts for selective aqueous photocatalytic carbon dioxide conversion into methane

Developing catalytic systems with high efficiency and selectivity is a fundamental issue for photochemical carbon dioxide conversion. In particular, rigorous control of the structure and morphology of photocatalysts is decisive for catalytic performance. Here, we report the synthesis of zinc oxide-copper(I) oxide hybrid nanoparticles as colloidal forms bearing copper (I) oxide nanocubes bound to zinc oxide spherical cores. The zinc oxide-copper(I) oxide nanoparticles behave as photocatalysts for the direct conversion of carbon dioxide to methane in an aqueous medium, under ambient pressure and temperature. The catalysts produce methane with an activity of 1080 mu mol g(cat)(-1) h(-1), a quantum yield of 1.5% and a selectivity for methane of >99%. The catalytic ability of the zinc oxide-copper(I) oxide hybrid catalyst is attributed to excellent band alignment of the zinc-oxide and copper(I) oxide domains, few surface defects which reduce defect-induced charge recombination and enhance electron transfer to the reagents, and a high-surface area colloidal morphology © The Author(s) 20171561sciescopu

Ex Situ and in Situ Surface Plasmon Monitoring of Temperature-Dependent Structural Evolution in Galvanic Replacement Reactions at a Single-Particle Level

The galvanic replacement reaction has recently been established as a standard protocol to create complex hollow structures with various compositions and morphologies. In the present study, the structural evolution of Ag nanocubes with Au precursors is monitored at the single-particle level by means of ex situ and in situ characterization tools. We explore two important features distinct from previous observations. First, the peak maximum of localized surface plasmon resonance (LSPR) spectra abruptly shifts at the initial stage and reaches a steady wavelength of ∼600 nm; however, the structure continuously evolves to yield a nanobox even during the late stages of the reaction. This steady wavelength results from a balance of the LSPR between the red-shift by the growth of the inner cavity and the blue-shift by the deposition of Au on the interior, as confirmed by theoretical simulations. Second, the change in morphology at different temperatures is first analyzed by both ex situ and in situ monitoring methods. The reaction at 25°C forms granules on the surface, whereas the reaction at 60°C provides flat and even surfaces of the hollow structures due to the large diffusion rate of Ag atoms in Au at a higher temperature. These plasmon-based monitoring techniques have great potentials to investigate various heterogeneous reaction mechanisms at the single-particle level. (Graph Presented). © 2015 American Chemical Society1561sciescopu

Poly(ethylene glycol)- and carboxylate-functionalized gold nanoparticles using polymer linkages: Single-step synthesis, high stability, and plasmonic detection of proteins

Gold nanoparticles with suitable surface functionalities have been widely used as a versatile nanobioplatform. However, functionalized gold nanoparticles using thiol-terminated ligands have a tendency to aggregate, particularly in many enzymatic reaction buffers containing biological thiols, because of ligand exchange reactions. In the present study, we developed a one-step synthesis of poly(ethylene glycol) (PEG)ylated gold nanoparticles using poly(dimethylaminoethyl methacrylate) (PDMAEMA) in PEG as a polyol solvent. Because of the chelate effect of polymeric functionalities on the gold surface, the resulting PEGylated gold nanoparticles (Au@P-PEG) are very stable under the extreme conditions at which the thiol-monolayer-protected gold nanoparticles are easily coagulated. Using the solvent mixture of PEG and ethylene glycol (EG) and subsequent hydrolysis, gold nanoparticles bearing mixed functionalities of PEG and carboxylate are generated. The resulting particles exhibit selective adsorption of positively charged chymotrypsin (ChT) without nonselective adsorption of bovine serum albumin (BSA). The present nanoparticle system has many advantages, including high stability, simple one-step synthesis, biocompatibility, and excellent binding specificity; thus, this system can be used as a versatile platform for potential bio-related applications, such as separation, sensing, imaging, and assays.112151sciescopu