Simple and convenient preparation of Au-Pt core-shell nanoparticles on surface via a seed growth method

Au-Pt core-shell nanoparticles were prepared on glass surface by a seed growth method. Gold nanoparticles were used as seeds and ascorbic acid-H2PtCL6 solutions as growth solutions to deposit Pt shell on the surface of gold nanoparticles. These core-shell nanoparticles and their growth process were examined by UV-Vis spectroscopy, X-ray photoelectron spectroscopy, atomic force microscopy and field-emission environmental scanning electron microscopy and the results indicated that the deposition speed was fast and nanoparticles with obvious core-shell structure could be obtained after 2 min. Moreover, this seed growth method for preparation of the core-shell nanoparticles is simple and convenient compared with other seed growth methods with NH4OH as a mild reductant. In addition, electrochemical experiments indicated that these Au-Pt core-shell nanoparticles had similar electrochemical properties to those of the bulk Pt electrode.

Growth of cationic lipid toward bilayer, lipid membrane by solution spreading: scanning probe microscopy study

The growth of cationic lipid dioctadecyldimethylammonium bromide (DODAB) toward bilayer lipid membrane (BLM) by solution spreading on cleaved mica surface was studied by atomic force microscopy (AFM). Bilayer of DODAB was formed by exposing mica to a solution of DODAB in chloroform and subsequently immersing into potassium chloride solution for film developing. AFM studies showed that at the initial stage of the growth, the adsorbed molecules exhibited the small fractal-like aggregates. These aggregates grew up and expanded laterally into larger patches with time and experienced from monolayer to bilayer, finally a close-packed bilayer film (5.4 +/- 0.2 nm) was approached. AFM results of the film growth process indicated a growth mechanism of nucleation, growth and coalescence of dense submonolayer, it revealed the direct information about the film morphology and confirmed that solution spreading was an effective technique to prepare a cationic bilayer in a short time.

Self-assembled monolayer growth of octanol on mica: Atomic force microscopy and Fourier-transform infrared spectroscopy studies

The growth kinetics of self-assembled monolayers formed by exposing freshly cleaved mica to octanol solution has been studied by atomic force microscopy (AFM) and Fourier-transform infrared spectroscopy (FTIR). AFM images of samples immersed in octanol for varying exposure times showed that before forming a complete monolayer the octanol molecules aggregated in the form of small islands on the mica surface. With the proceeding of immersion, these islands gradually grew and merged into larger patches. Finally, a close-packed film with uniform appearance and few defects was formed. The thickness of the final film showed 0.8 nm in height, which corresponded to the 40degrees tilt molecular conformation of the octanol monolayer. The growth mechanisms consisted of nucleation, growth, and coalescence of the submonolayer films. The growth process was also confirmed by FTIR. And the surface coverage of the submonolayer islands estimated from AFM images and FTIR spectra as a function of immersion time was quite consistent.

Periodic radial growth in ring-banded spherulites of poly(epsilon-caprolactone)/poly(styrene-co-acrylonitrile) blends

The isothermal crystallization process of a PCL/SAN blend (90/10 wt.-%) was investigated by using real time image analysis and hot stage optical microscopy. It was found that the growth rate of ring-banded spherulites in the isothermal crystallization process is not constant. Slow growth occurs in the bright bands, while fast growth is found in the dark bands. The radially unequal growth rate of ring-banded spherulites in PCL/SAN blends may be related to the convex band structure on the surface. This new discovery gives us the idea that rhythmic growth is effective in the growth process of ring banded spherulites.

Os isotope dating and growth hiatuses of Co-rich crust from central Pacific

Up to now, accurate determination of the growth age and hiatuses of the Co-rich crust is still a difficult work, which constrains the researches on the genesis, growth process, controlling factors, regional tectonics, paleo-oceanographic background, etc. of the Co-rich crust. This paper describes our work in determining the initial growth age of the Co-rich crust to be of the late Cretaceous Campanian Stage (about 75-80 Ma), by selecting the Co-rich crust with clear multi-layer structures in a central Pacific seamount for layer-by-layer sample analysis and using a number of chronological methods, such as Co flux dating, dating by correlation with Os-187/Os-188 evolution curves of seawater, and stratigraphic division by calcareous nannofossils. We have also discovered growth hiatuses with different time intervals in the early Paleocene, middle Eocene, late Eocene and early-middle Miocene, respectively. These results have provided an important age background for further researches on the Co-rich crust growth process and the paleo-oceanographic environment evolution thereby revealed in the said region.

The Effects Of Reduced Salinity On Colonial Growth And Membership In A Hydroid

The effect of different salinity levels on colonial growth and gonozooid frequency of the hydroid Campanularia flexuosa Hincks has been studied. It is shown that the usual cumulative presentation of growth data tends to obscure evidence of acclimation and other features of importance to an interpretation of adaptations of the growth process to salinity changes. A method of analysis is described that not only demonstrates acclimation, but apparently shows how growth is controlled after disturbance by changes in salinity. One other response to reduced salinity and other unfavourable changes in water chemistry is an increase in gonozooid frequency due to the diversion of resources from the formation of new hydranths.

Growth and public infrastructure

The paper analyzes a multicountry extension of the Barro model of productive public expenditure. In the presence of positive infrastructural externalities between countries, the provision of infrastructure will be inefficiently low if countries do not coordinate. This provides a role for a supranational body, such as the European Union, to coordinate the policies of the individual governments. It is shown how intervention by a supranational body can raise welfare by internalizing the infrastructural externality. Infrastructural externalities increase the importance of tax policy in the growth process and distribute the benefits of taxation across countries.

Growth and Melting of Metallic Nanoclusters in Glass: A Review of Recent Investigations

The mechanisms of nucleation and growth and the solid-to-liquid transition of metallic nanoclusters embedded in sodium borate glass were recently studied in situ via small-angle X-ray scattering (SAXS) and wide-an-le X-ray scattering (WAXS). SAXS results indicate that, under isothermal annealing conditions, the formation and growth of Bi or Ag nanoclusters embedded in sodium borate glass occurs through two successive stages after a short incubation period. The first stage is characterized by the nucleation and growth of spherical metal clusters promoted by the diffusion of Bi or Ag atoms through the initially supersaturated glass phase. The second stage is named the coarsening stage and occurs when the (Bi- or Ag-) doping level of the vitreous matrix is close to the equilibrium value. The experimental results demonstrated that, at advanced stages of the growth process, the time dependence of the average radius and density number of the clusters is in agreement with the classical Lifshitz-Slyozov-Waoner (LSW) theory. However, the radius distribution function is better described by a lognormal function than by the function derived from the theoretical LSW model. From the results of SAXS measurements at different temperatures, the activation energies for the diffusion of Ag and Bi through sodium borate glass were determined. In addition, via combination of the results of simultaneous WAXS and SAXS measurements at different temperatures, the crystallographic structure and the dependence of melting temperature T(m) on crystal radius R of Bi nanocrystals were established. The experimental results indicate that T(m) is a linear and decreasing function of nanocrystal reciprocal radius 1/R, in agreement with the Couchman and Jesser theoretical model. Finally, a weak contraction in the lattice parameters of Bi nanocrystals with respect to bulk crystals was established.

Growth of the hermit crab Clibanarius vittatus (Bosc, 1802) (Crustacea, Anomura, Diogenidae) at São Vicente, São Paulo, Brazil

O presente estudo teve como objetivo analisar o crescimento de machos e fêmeas do ermitão Clibanarius vittatus (Bosc, 1802), da região de São Vicente, São Paulo, Brasil. Foram realizadas coletas mensais de maio/2001 a abril/2003, na Praia dos Pescadores em São Vicente. Os 2.501 animais capturados foram identificados, determinados quanto ao sexo e mensurados quanto ao seu comprimento de escudo cefalotorácico (CEC). Para o estudo sazonal do crescimento, a população foi dividida em classes de tamanho de 5mm de (CEC), e analisada pelo método de Bertalanffy, com o auxílio do software Fisat II. Foram obtidos 703 indivíduos machos e 1.798 fêmeas, com média de tamanho de 8.94±1.80 e 6.61±1.13mm, respectivamente. Constatou-se um padrão de crescimento sazonal, com machos atingindo um tamanho assintótico (14.92mm) superior ao das fêmeas (13.85mm), além de iniciarem o processo de crescimento aproximadamente cinco meses antes destas. Desta forma, é provável que este seja um padrão que auxilia na diminuição da disputa intra-específica por conchas, uma vez que os machos atingiram maior tamanho e estariam disponibilizando conchas menores para as fêmeas.

An efficient microwave-assisted hydrothermal synthesis of BaZrO3 microcrystals: growth mechanism and photoluminescence emissions

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Growth mechanism of octahedron-like BaMoO4 microcrystals processed in microwave-hydrothermal: Experimental observations and computational modeling

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Novel Aspects of the Purpose-Built Materials Strategy: Evidence of Topographic Template Effect and Oriented Attachment Growth Mechanism

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Synthesis of SnO2 nanoribbons by a carbothermal reduction process

This communication describes, for the first time, the growth of SnO2 nanoribbons by a controlled carbothermal reduction process. An analysis of the transmission electron microscopy image revealed that these nanoribbons have a well-defined shape, with a typical width in the range of 70-300 nm. In general, the nanostructured ribbons were more than 100 mum in length. The results reported here support the hypothesis that this ribbon-like nanostructured material grows by a vapor-solid process. This study introduces two hypotheses to explain the SnO2 nanoribbon growth process.

Controlling the growth of zirconia needles precursor from a liquid crystal template

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Structure and growth mechanism of CuO plates obtained by microwave-hydrothermal without surfactants

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)