This paper describes a kinetic study of the mediator-template assembly of gold nanoparticles in solutions based on the spectrophotometric measurement of the surface plasmon resonance optical property. Gold nanoparticles of ∼5 nm diameter encapsulated with tetraoctylammonium bromide shells were studied as a model system. The core-shell nanoparticles were assembled into 3D spherical assemblies via a mediator-template assembly route in which a thioether-based multidentate ligand functions as a mediator and the tetraoctylammonium shell molecules function as a templating agent. In this report, the results were compared with those obtained for the assembly of gold nanoparticles in several different systems with features similar to the mediator-template assembly. The findings further provided further insights into understanding the kinetic factors governing the assembly of nanoparticles, and have important implications to the design and control of the nanostructures for sensory and catalytic applications.

Structural and morphological characteristics of (1-x)α-Fe2O3-xSnO2 (x=0.0-1.0) nanoparticles obtained under hydrothermal conditions have been investigated by X-ray diffraction (XRD) and Mössbauer spectroscopy. On the basis of the Rietveld structure refinements of the XRD spectra at low tin content, it was found that Sn4+ partially substitutes for Fe3+ at the octahedral sites. The mean particle dimension decreases from 70 to 6 nm as the molar fraction x increases. The estimated solubility limits in the system of tin-doped hematite nanoparticles synthesized under hydrothermal conditions are x<0.2 for Sn4+ in α-Fe2O3 and x>0.7 for Fe3+ in SnO2.

Crystallographic orientation of atomic planes makes a metal amenable to specific properties as desired in catalysis and environment sensing. Oriented metal nanoparticles are however less known. Here we present X-ray diffraction, transmission electron microscopy and atomic force microscopy data to provide evidence of copper nanoparticles with preferred orientation, achieved by electro-explosion of copper wires in an aqueous medium. The optical absorption in these particles is devoid of the usual Mie resonance at ∼ 580 nm, while maintaining bulk-like lattice periodicity. Under the highest reorientation (largest orientation index), absorption in the ultraviolet region is characterized by distinct and sharp resonant peaks, which are correlated with occupied valence band density of state (DOS) from copper clusters, making these truly crystalline particles with atom-like electronic properties.

This work presents high sensitive detection of specific adsorption of proteins onto a silicon oxide (SiOx) surface modified by molecules with a biotinyl-end group. We fabricated a SiOx waveguide by sputtering onto a thin gold film and measured the incident angle-dependence of reflectivity using a polarized He-Ne laser under total internal reflection condition. When the s-polarized light was irradiated to the SiOx waveguide (760 nm) coupled with a prism, the incident angle-dependence of reflectivity showed narrow dips due to excitation of the waveguide mode. The waveguide surface was modified by the molecules with the biotinyl-end group as a protein probe. Specific adsorption of streptavidin in a PBS buffer solution was monitored through time course of the reflectivity change at a constant incident angle, where the waveguide mode was excited. As compared with conventional SPR system using a gold surface, high sensitive detection of the specific adsorption was achieved. Additionally, we fabricated micro-patterned arrays of biotinyl-end layers onto the SiOx waveguide surface by micro-contact printing. Then we observed the specific adsorption behavior on the micro-patterned arrays by the imaging based on the waveguide mode using a CCD camera.

The present investigation is centered on the study of the growth curves of E. coli and C. xerosis bacteria in the presence of nanosize particles of Zinc Oxide. Previous works demonstrated the sensitivity of the bacteria, when these were reproduced in media that contain nanoparticles of luminescent silicon and Cobalt Ferrite. Doped ZnO nanocrystals were synthesized by conventional precipitation in ethanol solutions as reported by Spanhel and Anderson for bare ZnO. In our case, the syntheses were carried out under room-temperature conditions.

The experimental results of E. coli bacteria in contact with a stable suspension of nanoparticles of Zinc Oxide, shows a growth curve without adaptation period. Moreover a short and slowly logarithmic stage has been observed, reaching the stationary stage after approximately four hours compared with one in absence of the nanoparticles (standard curve). During the observations, a change in the lifetime of the bacteria (metabolism) with particulate was noticed,as well as the beginning of the mortality stage. However, different results were recorded for silicon and ferrite. For the case of the bacteria C. xerosis, the curve with particles is above its standard curve, for all times with none of the oscillations which occured in the nanometer silicon. For these bacteria the beginning of the mortality stage is observed when they have particles. For both bacteria with Zinc Oxide nanoparticles this occurs approximately after nine hours.

Highly aligned multi-walled carbon nanotube (MWCNT) arrays were synthesized on Si wafers. Water vapor was used to enhance the catalyst performance, which enabled continuous growth of MWCNT arrays for up to 3 hours. Various types of Fe patterning on a Si substrate with a multilayered structure were tested. MWCNT arrays up to 4 mm long were grown by Chemical Vapor Deposition (CVD). Environmental scanning electron microscopy was used to characterize the MWCNT morphology and showed that the nanotubes typically reveal a 20 nm outer diameter and 8 nm inner diameter. To investigate applications, a nanotube tower 1 mm × 1 mm × 4 mm in size was grown and peeled off the Si wafer. Each tower contains millions of individual nanotubes with 20–30 nm diameters. Electrochemical actuation of one MWCNT tower was demonstrated in a 2M NaCl solution. The MWCNT tower actuator operated up to 10 Hz without significantly decreasing strain. Only 1-2 volts was needed to obtain 0.2% strain. The aligned nanotube morphology of the tower is the reason for the high strain in the axial direction, which is an improvement compared to previously tested entangled buckypaper actuators. Cyclic voltammetry (CV) was performed to analyze the redox behavior of the nanotube tower used as an electrode. The CV response showed a sigmodal shape in a 6 mM K3(CN)6 ferrocyanide solution. This behavior provides ideal characteristics for biosensor development and application. Also, the measured electrical volume resistivity of the material was in the range of 0.1 ohm · cm. The overall improvement in the electrochemical actuation and electrical conductivity was much greater than previous nanocomposites obtained by dispersing powdered nanotubes into polymers. The demonstrated good properties suggest nanotube array towers can be considered a novel intelligent material.

Products formed from reactions of methyl iodide, 1-chloropropane, 1-iodopropane and 1-bromopropane with Na0 treated and untreated NaX and NaY zeolites were studied using solid state 13C NMR and IR spectroscopy. At room temperature, methyl iodide dissociates to form framework methoxy in untreated NaX with no reaction observed in untreated NaY. Upon Na0 treatment, both NaX and NaY reacts with methyl iodide to form framework methoxy, methane and ethane. Longer carbon chain 1-iodo, bromo and chloropropane were also studied. 1-iodopropane undergoes dehalogenation to form framework propoxy while 1-chloropropane and 1-bromopropane undergoes dehalogenation/ dehydrohalogenation to form framework propoxy and propene.

The ability to control composition and size in the synthesis of bimetallic nanoparticles is important for the exploitation of the bimetallic catalytic properties. This paper reports recent findings of an investigation of the synthesis of gold-platinum (AuPt) bimetallic nanoparticles in aqueous solution via reduction of AuCl4− and PtCl42− using a combination of reducing and capping agents. In addition to characterization of the morphological properties of the AuPt nanoparticles using TEM and XRD, the electrocatalytic activity of the carbon-supported AuPt nanoparticle catalysts was also examined for oxygen reduction reaction (ORR) using the rotating disk electrode (RDE) technique. The findings have implications to the design of bimetallic nanoparticle catalysts for fuel cell reactions.

Carbon nanotubes (CNTs) were synthesized by thermal chemical vapor deposition (thermal CVD) on n-type Si (100) at 700 ° under C2H2 gas flow ratio of 30 sccm. Fe catalysts were pre-deposited by RF sputtering system with RF power 150 W. Two kinds of as-grown CNTs were used to detect N2: the vertically oriented carbon nanotubes (CNTs) mat and horizontally oriented CNTs bundle. Two-terminal electrical measurements were performed at room temperature of 25 °. The electrical resistance of CNTs mat or bundle was found to increase when exposed to N2 environment, and to return back after the N2 pumping, respectively. However, the CNTs bundle had better sensitivity and possessed faster response and recovery time. This could be ascribed to that the CNTs bundle, with more effective grooves on the surface, provided more lower binding-force sites to absorb N2 molecules than the CNTs mat dose, which prominently had interstitial sites.

Experimental observations and theoretical treatments are carried out for the band shape and relative intensity of the emission from gold nanorods of various aspect ratios in the range between 2.6 (1.5 theory) and 6.3 (9 theory). The calculation of the fluorescence spectra requires knowledge of the nanorod size distribution, the enhancement factors and the shape of the un-enhanced fluorescence spectrum. The comparison between the observed and calculated fluorescence band shapes is found to be good. The calculated changes in the relative intensities with aspect ratios are found to be much greater than that observed experimentally. This is due to the fact that for the observed emission of all the rods studied, nonradiative processes dominate the relaxation mechanism of the excited state, a fact that was not included in the theoretical treatments. Experimental results and theoretical treatments will be presented.

The highly dispersed metal (e.g. Au) nanoparticles have exhibited exceptional catalytic activity for several reactions, including CO oxidation. Their high catalytic activity has been attributed to nanoparticles nano-structural effects (including cluster thickness, shape, chemical information, and number of atoms of the cluster). The three dimensional exact structure and chemical bonding state of these supported nanoparticles is still challenging to be quantified by conventional methods due to their limitations in understanding size distribution of supported metal nanoparticles that are usually less than 1 nm (< 100 atoms). In this paper, the structure of Au heterogeneous catalysts has been successfully characterized by High Resolution Electron Microscopy (HREM), Z-contrast Scanning Transmission Electron Microscopy (STEM). The ligand protected Au13 nanoparticles on TiO2 support have been studied by ozone and thermal treatments to remove the ligands. The ozone removal method results in the truncated cuboctahedral structure while the thermal treatment results in the cuboctahedral structure. The ozone treatment yields less Au nanoparticles sintering than thermal treatment. Their FCC structure was confirmed by quantified Z-contrast STEM, HREM and its Fourier transformation.

We report a novel, simple, and inexpensive method for preparing efficient carbon nanotube-based hydrogen sensors. Sensor devices were fabricated by simply spraying single-walled carbon nanotube (SWNT) dispersions on alumina substrates. Pd-functionalization of the employed SWNTs enabled increasing the device sensitivity to hydrogen. The effect of aging, thermal processing, and the employed carrier gases on the sensor performance is here described. The fabricated thin film sensors exhibited good sensitivity to hydrogen at room temperature in reversible and reproducible detection processes.

This paper describes the synthesis of N-doped, F-doped, and N-F-codoped TiO2 powders (NTO, FTO, NFTO) by spray pyrolysis (SP). An overall comparative study was carried out on these anion-doped powders in order to elucidate the roles of N and F played in visible-light (Vis)-driven photocatalysis. The comparisons in their characteristics were based on the analysis of UV-Vis, PL, NH3-TPD and ESR spectra. As the results, N-doping into TiO2 resulted in both the improvement of Vis absorption and the creation of surface oxygen vacancies (OVs). F-doping produced several beneficial effects including the creation of surface OVs, the enhancement of surface acidity and the increase of Ti3+ ions. The photocatalytic tests indicated that the NFTO demonstrated the highest Vis activity for decomposition of both acetaldehyde and trichloroethylene. This high activity was ascribed to a synergetic consequence of doped N and F.

The recent interest in oxidation catalysis provides the focus for this paper. Until recently gold has been overlooked as a key component of both homogeneous and heterogeneous catalysts. However, the observation in the 1980's that nanocrystalline gold supported on oxides was an effective catalyst for low temperature carbon monoxide oxidation has now captured the imagination of many researchers. At present low temperature carbon monoxide oxidation remains an intensely studied field, but in recent years increased emphasis has been placed on using gold catalysts for selective oxidation. For example the oxidation of alkanes, alkenes and alcohols have all been shown to be effective with gold based catalysts. In addition gold palladium catalysts have been shown to be very effective for the direct formation of hydrogen peroxide and this will be described in this paper.

We demonstrate a micro-molding method for submicron patterning of a low-index sol-gel nanoporous glass for the purpose of fabricating large-area (∼3”×”) label-free photonic crystal optical biosensors. SEM images show that the sol-gel exhibited minimal shrinkage and good substrate adhesion and depict precise and uniform pattern transfer over the fabricated area within the limits of measurement resolution. A unique characterization approach accurately and quickly revealed porous glass patterned over a large area with geometrical and material properties uniform within 1%. We suggest that this robust method is an excellent approach for photonic crystal sensor fabrication, and may also find applications in integrated optics and electronics.

Patterning proteins at the sub-micron and nanoscale has many uses, including fabrication of protein arrays for diagnostic and sensor applications. Many groups have reported micron scale protein patterns using photolithography; however, smaller scales have not been realized. In this study, we demonstrate sub-micron protein patterns using photolithography. Patterning is achieved by chemical transformation of pH-reactive polymer films. Site-specific immobilization of streptavidin within a protein resistant background is demonstrated. This methodology could be utilized for the development of high density proteins arrays for biotechnology applications.

Titanium oxide and titanates based on Ba, Sr and Ca were prepared from commercial solutions of TiCl4 and HNO3. The main preparation steps for the sols consisted of elimination of chloride anions by distillation with nitric acid and addition of metal hydroxides for the titanates. Resulting sols were gelled and used to (1) prepare irregularly shaped powders by evaporation; (2) produce by a dipping technique thin films on glass, Ag, or Ti substrates; and (3) produce spherical powders (diameters <100 μm) by solvent extraction. Results of thermal and X-ray-diffraction analyses indicated that the temperatures required to form the various compounds were lower than those necessary to form the compounds by conventional solid-state reactions and comparable to those required with use of organometallic based sol-gel methods. Temperatures of formation could be further reduced by addition of ascorbic acid to the sols.

Metallic and semi-conducting nano-particles were incorporated into and on the surface of optical fibers to form sensors and other optoelectronic devices on standard telecommunications grade optical fibers. Optical fibers provide a macroscopic platform to exploit the wide range of functionality inherent in nanostructures and nano-particles. Several ways of forming sensitive and robust chemical sensors, based on plasmon resonances of metallic islands and nano-particles, were demonstrated. These nano-particles were formed on tip or surface of the optical fibers by thermal or plasma arc annealing of very thin (4 -12 nm) gold films, that were deposited by electron beam deposition and sputtering. Development of in-line optical fiber structures, involving single mode or multimode optical fibers fused to an arrangement of coreless and graded index fibers, was also carried out. This enabled light propagating in the core of the optical fiber to expand to the surface of the coreless fiber and to effectively interact with nano-particles on the surface and the environment. Metallic and semiconducting nano-particles were also incorporated inside an optical fiber matrix and this could enable us to effectively characterize novel materials and possibly form optical switches. Moreover, these optical fiber sensors and devices were integrated into textile structures to explore the possibility of formation of optoelectronic textiles.

Catalytic properties of noble metal catalysts are often caused by their nanostructures and the interaction between nano particles and oxides supports. We examine the mean inner potential of Pd particles in Pd/TiO2 catalyst and Ag particles in Ag/TiO2 catalysts using electron holography and HRTEM. And we compare the results of the Pd/TiO2 and Ag/TiO2 systems with our previous results of the Au/TiO2 and Pt/TiO2 systems. In the case of the Pd/TiO2 catalysts, when the size of Pd particle is smaller than 5nm, the mean inner potential of Pd changes to be higher than the calculated value of the mean inner potential which is thought to be higher than the experimental values of bulk Pd by 3-5V. The mean inner potential of Pd becomes to increase gradually as the size of the Pd particle decreases. The rate of the increment in the mean inner potential of Pd is lower than that of Au/TiO2 catalysts and Pt/TiO2 catalysts. On the other hand, in the case of Ag/TiO2 catalysts, the mean inner potential of Ag does not increase though the size of the Ag particle decreases to under 2nm.

At 2 % cationic lipid and 98 % phospholipid, pH 6.3, in pure water, high affinity adsorption isotherms with limiting adsorption indicative of one bilayer deposition on each silica particle were obtained whereas for the other molar proportions tested, limiting lipid adsorption was either above or below the level expected for bilayer deposition. This suggested a modulating role for cationic lipid allowing control of total amount of lipid adsorbed on silica. Silica sedimentation documented from photographs was almost absent over a range of lipid concentrations where bilayer deposition was achieved.