The nanoporous materials prepared from iron-iron oxide core-shell nanoparticles are of great interest due to their enhanced possibilities for distribution in the environment, a high rate of chemical reactivity and also the possibility to enhance environmentally friendly reaction paths. However, production of these nanoparticle porous materials by conventional methods is difficult. Therefore, we use a cluster deposition system, which prepares the iron nanoclusters and iron-iron oxide core shell nanoclusters at room temperature. The nanoporous films are synthesized by using the nanoclusters as building blocks. These films are characterized using Transmission Electron Microscopy (TEM), Atomic Force Microscopy (AFM), and the Brunauer-Emmett-Teller (BET) method for surface area determination.

When conductive solids with nanoscale porosity are immersed in electrolyte and biased against a suitable counter electrode, the surface is charged and the properties of the matter at the surface vary reversibly as the function of the bias voltage. Due to the immense surface area at nanoscale pore size, the local changes are reflected in the macroscopic materials properties. Specifically, changes in the superficial interatomic bonding lead to a stress and strain of the material, with strain amplitude and strain energy density of sufficient magnitude to suggest possible application as actuator materials. We discuss an experiment which provides an insight into the underlying microscopic processes at the metal electrolyte interface: are changes in the surface bonding in the metal dominant, or does the effect arise mainly from the formation of chemical bonds with adsorbates? We studied the variation of the surface stress charge coefficient of Pt in weakly adsorbing aqueous solutions of NaF of various concentrations. As the concentration is reduced, we find initially an increase in the magnitude of the surface stress-charge coefficient, followed by saturation at a value of -1.9V. Since specific adsorption is expected to be reduced as the solution become more diluted, in favor of the capacitive charging, the results support the notion that changes in the bonding between the metal atoms control the variation in the surface stress during double-layer charging.

H2NiTi4O10/TiO2 intercalated compound was fabricated by successive intercalation reactions of H2NiTi4O10 with n-C6H13NH2/C2H5OH mixed solution and acid TiO2 sol, followed by irradiating with a high-pressure mercury lamp. H2NiTi4O10, a layered perovskite type compound with TiO2-loading, exhibited a high activity for decomposition of methyl orange under UV and visible light irradiation. The experimental results showed that methyl orange was degraded with the decomposition ratio of 59.0 % by using H2NiTi4O10/TiO2 as photocatalyst under visible light ( > 420 nm) irradiation for 24 h. The H2NiTi4O10/TiO2 possessed higher photocatalytic activity than those commercial titania powder (Degussa P-25) which showed the decomposition ratio just only 24% under same condition.

A quick and dependable technique has been developed that allows us to selectively produce anodized TiO2 in the form of nanotubes. The process employs mild chemical conditions and ambient temperature. The method can consistently produce nearly 100% surface coverage of nanotubes within 10 min of anodizing. Anodizing in relatively high pH electrolytes for 1 hour permitted us to produce nanotubes of 2μm length. We attribute the repeatability of our results to a brief pre-anodizing etching step that consistently leads to excellent anodizing results. Without this etching step, we experienced very poor consistency in that only small patches of titania nanotubes were formed.

This work presents the rapid detection of Bacillus subtilis spores, harmless simulants for Bacillus anthracis, using surface-enhanced Raman spectroscopy (SERS) on silver film over nanosphere (AgFON) substrates. Calcium dipicolinate (CaDPA), a biomarker for bacillus spores, can be extracted effectively from spores with nitric acid and successfully detected by SERS. The highly tunable nature of AgFON optical properties was exploited to establish general optimization conditions. AgFON surfaces optimized for 750-nm laser excitation have been characterized by UV-vis diffuse reflectance spectroscopy. The SERS signal from extracted CaDPA was evaluated over the spore concentration range 10-15-10-12 M to determine the adsorption capacity of the AgFON surface and the limit of detection (LOD). These sensing capabilities have been successfully transitioned to an inexpensive, portable Raman spectrometer. Using the extraction method and this field-portable instrument, the anthrax infectious dose of 104 spores were detected with only a 5-second collection period on a one-month-old prefabricated AgFON substrate.

The preparation of ordered mesoporous boron nitride by using borazinic precursors as boron nitride source (tri(methylamino)borazine (MAB) and tri(chloro)borazine TCB) and a mesoporous carbon CMK-3 as template is reported. A template elimination performed by hydrogenation allows to obtain an organized porous structure. The X-ray diffraction, TEM and pore size analysis show that the structure of the BN molecular sieves synthesized from CMK-3 consists in a 2D regular array of uniform mesopores of 3.4 nm in diameter.

We present a selection of x-ray diffraction patterns of spherical (He, Ar), dumbbell- (N2, CO), and chain-like molecules (n-C9H20, n-C19H40) solidified in nanopores of silica glass (mean pore diameter 7nm). These patterns allow us to demonstrate how key principles governing crystallization have to be adapted in order to accomplish solidification in restricted geometries. 4He, Ar, and the spherical close packed phases of CO and N2 adjust to the pore geometry by introducing a sizeable amount of stacking faults. For the pore solidified, medium-length chainlike n-C19H40 we observe a close packed structure without lamellar ordering, whereas for the short-chain C9H20 the layering principle survives, albeit in a modified fashion compared to the bulk phase.

Nanoporous metal samples with millimetre size were prepared either by compacting nanocrystalline powders or by dealloying, the dissolution of the less noble metal(s) of an alloy. The samples were immersed in an electrolyte, and their length was measured as a function of the applied potential in-situ in a dilatometer. The results obtained for nanocrystalline platinum, nanoporous gold and for gold platinum alloys show that the length varies in dependence of the surface charge. The strain amplitude of nanocrystalline platinum was 0.15%, and even larger strains have been measured using an Au-Pt alloy. This strain is comparable to commercial piezoceramics, but it is achieved using smaller voltages.

The strain measured for nanoporous gold prepared by dealloying was smaller than that mainly due to the larger structure size (20 nm structure size compared to 6 nm Pt crystallite size), but in the case of gold, it was possible to prepare stable composite structures of a metal foil and of the nanoporous gold. If such a bimetallic foil is charged, it is found to bend. Due to the mechanical amplification of the contraction or expansion of the nanoporous part of the foil, it was possible to observe the effect of electric charges on the surface stress of metals directly with the naked eye for the first time.

These results demonstrate that nanoporous metals might be useful for actuator applications and for the study of surface strain effects. Furthermore, they are the first realization of a general concept that suggests that most of the properties of conducting nanomaterials can be tuned by controlling the surface charge.

Nano-structured colloidal semiconductors with heterogeneous photocatalytic behavior have drawn considerable attention over the past few years. This is due to their large surface area, high redox potential of the photogenerated charge carriers and selective reduction/oxidation of different class of organic compounds. Nano-structured TiO2 is widely used as a photocatalyst for the effective decomposition of organic compounds in air and water under UV radiation. On the other hand, the development of visible light activated photocatalysis, for utilizing the available solar energy remains a challenge and requires low band gap materials as sensitizer. Among the various inorganic sensitizers, bulk CdS with an Eg of 2.5 eV and an energetically high-lying conduction band has been identified as a potential candidate. This can be coupled with a large band gap semiconductor (TiO2 with Eg ∼ 3.2 eV) for visible light photocatalysis and solar energy conversion. In the CdS sensitized TiO2 nano-composite system, charge injection from the conduction band of the semiconductor sensitizer to that of TiO2 can lead to an efficient and longer charge separation by minimizing electron-hole recombination. In the present paper, we have carried out a systematic synthesis of nano-structured CdS/TiO2 via reverse micelle process. The structural and microstructural characterizations of the as-prepared CdS/TiO2 nano-composites are determined using XRD and SEM-EDS techniques. The visible light assisted photocatalytic performance is monitored by means of degradation of phenol in water.

Highly oriented plate-like rod/tube arrays of ZnO are synthesized by a solution-based approach at low temperature. The ZnO rod/tube arrays grow oriented vertically on silicon substrate and the intersectant ZnO nanosheets stand on the backbones of ZnO rods/tubes. The constructions of plate-like rod or tube arrays depend on the processing conditions. The growth mechanisms are investigated based on the nucleation and growth process. The initial ZnO film formed on substrate is crucial for the growth of ZnO rods/tubes perpendicular to the substrate. The nanosheets grow around the ZnO rods/tubes by the secondary nucleation and growth process. The ZnO tubes are formed by the etching of the ZnO polar faces. The novel ZnO structures are expected to have great potential for electronics, photoelectronics, sensors, and catalysis etc.

Hydrated CeOx2 nanoparticles of rod-like morphology have been obtained via a two-stage chemical precipitation method. The structure of the particles has been investigated using high resolution imaging techniques with a transmission electron microscope. The particles are found to exhibit five-fold symmetry and multiple twinning around {111} crystallographic planes. A structural model for the rod-like morphology is proposed. The mechanism of formation of such a structure is likely to depend on the unique chemistry of cerium and the preparation route.

Porous aluminum oxide membranes with a complete and even covering of alumina nanowires were formed in a one-step anodization process in dilute phosphoric acid electrolyte. The anodizing conditions can be adjusted to start forming alumina wires that originate on the surface of the porous alumina layer at the triple junction points (the edges of the hexagonal inter-pore structure where three pores meet). The wires tangle together as they become longer; eventually creating a tangled mesh layer above the porous oxide layer. SEM micrographs of the oxide cross section show tapered wires that are approximately 2 to 10 m long, depending on anodizing time, and range in width from a few nanometers to 50nm. The aluminum substrate can be chemically removed and the alumina barrier layer dissolved to leave a free standing porous alumina membrane with very high surface area alumina wires on one face. Some possible future applications of this high surface area structure involve filtration of liquids and gasses, combined with chemical functionalization on the large surface area.

A high-throughput work flow for rapid synthesis and testing of metal oxide nanoparticles for the discovery of new gas sensors of improved sensitivity and selectivity has been developed. The material libraries consist of nanoscaled metal oxide particles which are obtained either from pyrolysis of appropriate precursors or from polyol mediated synthesis. The design of a multielectrode array with 8x8 interdigital electrodes allows efficient and automated pipetting robot assisted sample preparation and material deposition. For characterisation of the sensor arrays high throughput impedance spectroscopy has been used. Test gas sequences and sensor temperatures can be varied. As an example, the properties of an In2O3-based library are introduced.

For the first time, silica nanofiber mats containing vanadium pentoxide crystals have been made via a sol-gel/electrospinning technique without using any polymer binder. XRD analysis after calcination of the fibers indicates the presence of vanadium pentoxide crystals. The average diameter of 20mol%V fibers after calcination at 800°C is 420nm. SEM and TEM images demonstrate crystal growth on the surface of the fibers after calcination at 800°C. XPS analysis also indicates the growth of V2O5 crystals at high enough temperatures. Physisorption of 20mol%V fibers after calcination at 800°C gave a BET surface area of 1.9 m2/g and an average pore diameter of 6 nm.

Ordered uniform nanoporous carbons with pore sizes in the range of 10 – 600 nm were synthesized against removable colloidal crystalline templates by carbonization of phenol and formaldehyde as a carbon precursor. The porous carbons have high surface areas, large pore volumes, and three-dimensionally interconnected uniform pore structures, and thus were used as a support of a Pt(50)-Ru(50) alloy catalyst to study their effect on the anodic performance of the catalyst in direct methanol fuel cell. The use of the ordered uniform porous carbon allowed higher degree of dispersion of the catalysts and efficient diffusion of reagents, resulting in much improved catalytic activity for methanol oxidation in the fuel cell. In general, the smaller pore sizes the porous carbons have, the higher surface areas and the better catalytic activity for methanol oxidation they showed.

Nanocrystalline tin oxide powder was prepared using a solution precipitation technique after adding the surfactant sodium bis (2-ethylhexyl) sulfosuccinate (AOT). Powders were characterized using X-ray diffraction (XRD), surface area (BET) and transmission electron microscopy (TEM). The gas sensitivity for surfactant added powders increased for liquid petroleum gas (LPG) as well as compressed natural gas (CNG), due to the decreased particle size and the increased surface area. The LPG gas sensitivity increased several times using phosphorus treated surfactant AOT.

The wide bandgap semiconductor TiO2 has become the dominant UV-activated photocatalyst in the field of air and water detoxification because of its high stability, low cost, high oxidation potential and chemically favorable properties. The demand for visible-light activated photocatalytic systems is increasing rapidly; however, currently, the efficiency and availability of photocatalysts that can be activated effectively by the solar spectrum and particularly indoor lighting is severely limited. In this paper, a new coprecipitation/hydrolysis synthesis route is used to create a TiO2-ZnFe2O4 nanocomposite that is directed towards extending the photoresponse of TiO2 from UV to visible wavelengths (>400nm). The effect of TiO2's accelerated anatase-rutile phase transformation due to the presence of the coupled ZnFe2O4 narrow bandgap semiconductor is evaluated. The transformation's dependence on pH, calcination temperature, particle size, and ZnFe2O4 concentration has been analyzed using XRD, SEM, and UV-Visible spectrometry. The requirements for retaining the highly photoactive anatase phase present in a ZnFe2O4 nanocomposite are outlined. The visible-light activated photocatalytic activity of the TiO2-ZnFe2O4 nanocomposites have been compared to an Aldrich TiO2 reference catalyst, using a solar-simulated photoreactor for the degradation of phenol.

A highly doped n-type silicon wafer is anodized in an aqueous hydrofluoric acid solution to generate a porous silicon skeleton with a convenient morphology. After drying, the mesoporous sample is exposed to an electrodeposition process in which the pores are filled with the ferromagnetic metal Ni. Anodization and deposition of Ni lead to a ferromagnetic nanoscopic system which shows an interesting behaviour in the high field range (> 3 T). In addition to the expected low field switching below 500 Oe a second switching at fields of a few Tesla with a steep slope is also present. This feature with its extremely high sensitivity for changes of the external magnetic field gives rise to high magnetic field sensor applications based on a silicon technology.

Highlights of our pioneering development of atomic resolution in situ environmental transmission electron microscope (ETEM) for direct probing of gas-solid reactions and in situ nanosynthesis are described. Dynamic studies on supported nanoparticle catalysts and carbon nanotubes under different reaction environments have been carried out. The results provide deep insights into the dynamic nanostructure of the materials and their mode of operation.

Metal clusters supported by transition metal oxides, as exemplified by the Au/TiO2 system, have found broad applications as catalytic and sensor materials. The unusual properties of these systems originate from the specific interactions of metal clusters mediated by an oxide substrate, including local reduction below the cluster. In this work, we present recent results on the local interactions between one-dimensional defects on a TiO2 surface and their reactivity with oxygen and Au nano-clusters studied by a combination of Scanning Tunneling Microscopy and Spectroscopy (STM/S). High-resolution STM images, interpreted with first-principles theory, show that the observed one-dimensional strands have partially reduced Ti atoms coordinated above three-coordinated, surface oxygen atoms. When strands are exposed to 5 x 10-7 Torr O2 at 300 K, oxygen is adsorbed and randomly nucleated on and along the strands. The results indicate the presence of exposed Ti that act as an active site for oxygen adsorption even at room temperature. Gold nano-particles of diameters 5 nm and less have also been deposited on the sub-stoichiometric rows of TiOx and characterized by STM. Like point defects and step edges on TiO2(110), the strands serve as nucleation sites for gold nano-clusters. The 1D defects of the surface are interpreted in terms of a surface crystallographic shear type structure, in contrast to the proposed Ti2O3 added row model by Onish and Iwasawa [Phys. Rev. Lett. 76, (1996) 791]. The implications of this behavior and specific interaction between gold clusters, defects and gas molecules for catalytic activity of the Au/TiO2 system are discussed.