The search for durable dyes led several past civilizations to develop artificial pigments. Maya Blue (MB), manufactured in pre-Columbian Mesoamerica, is one of the best known examples of an organic-inorganic hybrid material. Its durability is due to the unique association of indigo molecule and palygorskite, a particular fibrous clay occurring in Yucatan. Despite 50 years of sustained interest, the microscopic structure of MB and its relation to the durability remain open questions. Combining new thermogravimetric and synchrotron X-ray diffraction analyses, we show that indigo molecules can diffuse into the channel of the palygorskite during the heating process, replacing zeolitic water and stabilizing the room temperature phases of the clay.

We report preliminary studies on the preparation of carbon nanoparticles (CNPs) of ~ 20 nm in diameter derived from asphaltenes under mild conditions. This transformation occurred upon heating a thin film of asphaltenes cast on a carbon coated copper grid under both nitrogen and oxygen atmosphere. The resulting CNPs were characterized by thermogravimetric analysis (TGA), scanning/transmission electron microscopy (SEM/STEM), transmission electron microscopy (TEM), elemental analysis (EA) and Auger electron spectroscopy (AES). The findings point towards asphaltenes, a crude oil by-product, as a potential source for carbon nanomaterials.

Low resistance and high reflectance ohmic contacts on p-type GaN were achieved using an Ag-based metallization scheme. The ohmic nature of the contacts can be obtained by annealing the contacts in an O2 ambient. However, Ag based contacts degrade due to agglomeration of Ag when annealed above 400 o C [1]. In this work a Ni (1 nm)/Ag (150 nm)/Pt (50 nm)/Ni (20 nm)/Au (50 nm) metallization stack is investigated to reduce Ag agglomeration. The inclusion of platinum as a diffusion barrier is expected to suppress excess oxygen diffusion into the Ag films thereby preventing Ag agglomeration and can also provide high thermal stability when compared to other metallization schemes. The reflectivity of this kind of metallization scheme is around 85-90 % in the wavelength range of 400-600 nm making it suitable for blue and green LEDs, with a specific contact resistivity value comparable to other well developed contacts to p-GaN.

The dissolution kinetics of type B carbonate apatite (CAp) disks sintered atdifferent temperatures were investigated under acidic conditions similar toan osteoclastic desorption process in bone remodeling. The type B CAp disks,which were uniaxially pressed at 98MPa and sintered at temperatures of 600to 700 ºC, showed single crystalline phase and a high relative density of60-62 % compared to the stoichiometric density of 3.16g/cm3 ofhydroxyapatite (HAp). The dissolution rate of type B CAp disks sintered at650 ºC was 3.5 times faster than that of HAp disks at 650 ºC. These resultsindicate that the Type B CAp sintered disks show potential use as abiodegradable material for artificial bone.

Developing a durable and scalable transparent conductor (TC) as an electrode with high optical transmission and low sheet resistance is a significant opportunity for enabling next generation solar cell devices. High performance fibrous composite materials based on a carrier polymer with embedded functional nanostructures have the potential to serve as a TC with high surface area that can be deposited by the novel and scalable process of electrospinning. This work presents the development of a fibrous TC, where polyacrylonitrile (PAN) is used as a carrier polymer for multi-walled carbon nanotubes (MWCNT) to create electroactive nanofibers 200-500nm in diameter. Once carbonized, thin layers of this material have a low sheet resistance and high optical transmission. It is shown that in a two stage carbonization process, the second stage temperature of above 700C is the primary factor in establishing a highly conductive material and single layers of nanofibers are typically destabilized at high temperatures. A high performance TC has been developed through optimizing carbonization rates and temperatures to allow for single nanofiber layers fabricated by electrospinning MWCNT/PAN solutions onto quartz. These TCs have been optimized for concentrations of MWCNTs less than 20% volume fraction with well above 90% transmissivity and sheet resistances of between .5-1kohm/square. The required MWCNT loading is well below that for TCs based on random networks of MWCNTs.

We present a scalable, continuous manufacturing method of nanoparticle production based on laser ablation of an aerosol generated from an aqueous precursor solution. A Collison nebulizer is used to generate a mist of ~10 μm diameter water droplets containing dissolved transition metal salts, suspended in 1 atmosphere of buffer gas. Water from the droplets quickly evaporates, leaving solid particles ~2 μm in diameter for a typical solution concentration. These microparticles are then ablated by a pulsed KrF excimer laser (10 ns, λ = 248 nm, 2 J/cm2 at focus). Ablation results in plasma breakdown of the microparticle and photothermal decomposition of the precursor material. Following ablation, nanoparticles 5-20 nm in diameter are formed and collected. For AgNO3 ablated in He gas, metal Ag nanoparticles were produced. For Cu(NO3)2 ablated in He, crystalline Cu2O nanoparticles were produced. For Ni(NO3)2 ablated in He, crystalline NiO nanoparticles were produced. A combination of AgNO3 and Cu(NO3)2 ablated in a reducing atmosphere of 10% H2 and 90% He yielded Ag-Cu alloy nanoparticles. In contrast to conventional wet-chemical synthesis processes, our nanoparticles are formed ‘bare,’ without surfactants or organic material contaminating the surface. Owing to their small size and high free surface area, nanoparticles produced by this process are ideally suited for applications that include catalysis and facilitated transport membranes.

The ion beam synthesis of Pb nanoparticles (NPs) in silica/silicon films is studied in terms of the combination of a two-step annealing process consisting of a low temperature long time aging treatment followed by a high temperature short time furnace annealing. The samples are analyzed through Rutherford Backscattering Spectrometry and Transmission Electron Microscopy. The aging process leads to the suppression of the classical homogeneous nucleation of metallic Pb NPs in the silica, thus promoting Pb redistribution during the high temperature annealing. This causes the formation of dense bi-dimensional NP arrays located at the silica-silicon interface, presenting small size dispersion.

Density-functional theory (DFT) calculations of interphase boundary energies provide useful input for many precipitate growth models in alloy systems [1]. One example is Al-Ag, where a rich variety of precipitate types exist, and the sizes and shapes are determined roughly by a Wulff construction, namely, minimizing surface free energies with respect to geometry. This is only a first approximation, however, as kinetic-considerations and crystallography do not allow for a uniform, isotropic growth. Consequently, a nonequilibrium growth model is developed for γ-plates [2], which attempts to connect semi-coherent (ledge) and incoherent (edge) interface growth rates in a way that incorporates shape and interface energies. Through this connection, we make a DFT model with approximate unit cells that mirror experimental conditions, which gives accurate predictions for precipitate aspect ratios and time-development of nonequilibrium shapes. Starting from an explicit calculation of Suzuki segregation of solute to stacking-faults, we find a mechanism for nucleation of nanoscale γ-plates on quenched defects, identify a bulk structure from a calculated phase diagram that gives the relevant HCP equilibrium precipitate structure occurring at 50 at.% Ag and calculate critical nucleation parameters for γ-precipitate formation. Applications to island-coarsening and lath morphology are also discussed.

Integration of nanomaterials into composite systems is the next evolutionary step in nanoscale science. Until recently nanocomposites are formed by embedding nanomaterial components into matrices, through chemical bonding or with various wrapping agents. We seek to show that through directed self assembly nanomaterials can be coupled with photosensitizing ruthenium complexes while avoiding chemical augmentation and insulating effects from polymer, surfactant or DNA wrapping. We have synthesized dinuclear ruthenium complexes (dimers) possessing rigid conjugated π-electron systems that form a nanoscale pocket. The pocket is dimensionally suited to interact strongly with nanomaterials forming an architecture that could facilitate photon collection and charge transfer across the interaction. This study explores the binding interaction of our ruthenium dimers with SWNTs. The binding strength varies relative to the magnitude of formal charge which trends with DFT simulations that predict SWNT dimer interactions. SWNT surface saturation by ruthenium dimers can be observed using UV-visible spectroscopy and characterized with adsorption isotherms. We also explore a new technique to measure nanomaterial interactions, isothermal titration calorimetry (ITC). We show that ITC can be used to directly measure the binding enthalpy of nano material surface interactions in solution.

We synthesized amorphous semiconductor films composed of Mo-encapsulating Si clusters (MoSin : n∼10) on solid substrates. The MoSi10 films had Si networks similar to hydrogenated amorphous Si and an optical gap of 1.5 eV. Electron spin resonance signals were not observed in the films indicating that dangling bonds of Si were terminated by Mo atoms. We fabricated thin-film-transistors using the MoSi10 film as a channel material. The electric field effect of the film was clearly observed. This suggests that the density of mid-gap states in the film is low enough for the field effect to occur.

Ventilator associated pneumonia (VAP) is a serious and costly clinical problem. Specifically, receiving mechanical ventilation over 24 hours increases the risk of VAP and is associated with high morbidity, mortality and medical costs. Cost effective endotracheal tubes (ETTs) that are resistant to bacterial infection would help to prevent this problem. The objective of this study was to determine differences in bacterial growth on nanomodified and unmodified ETTs under dynamic airway conditions, a bench top model based upon the general design of Hartmann et al. (1999) was constructed to test of the effectiveness of nanomodified ETTs under the airflow conditions present in the airway. Twenty-four hour studies performed in a dynamic flow chamber showed a marked difference in the biofilm formation on different areas of unmodified tubes. Areas where tubes were curved, such as at the entrance to the mouth and the connection between the oropharynx and the larynx, seemed to collect the largest amount of biofilm. On the nanomodified tubes biofilm formation was markedly different occurring on smaller pieces.

The biofilm formation on ETTs in the airflow system after 24 hours showed a large difference depending upon where tubes were oriented within the apparatus. This illustrates the importance of dynamic flow on biofilm formation in pediatric ETTs. It is of particular interest that increased biofilm density on both unmodified and nanomodified tubes appeared to occur at curves in the tube where changes in flow pattern occured. This emphasizes the need for more accurate models of airflow within pediatric ETTs, suggesting that not only does flow affect pressure gradients along the tube, but in fact, determines the composition of the film itself. More testing is needed to determine the effects of biofilm formation on the efficiency of ETT under airflow, however this study provides significant evidence for nanomodification alone (without the use of antibiotics) to decrease bacteria function.

We focused on detailed evaluations of properties of the ultra-thin pore-seal layer (< 3 nm-thick), such as Cu diffusion barrier property and thermal stability. Cu diffusion into dense thermal silica and porous silica low-k which are covered with the pore seal layer was evaluated using metal-insulator-semiconductor (MIS) capacitors under bias thermal stress (BTS). Triangular voltage sweep (TVS) measurement shows that the ultra-thin layer on dense thermal silica suppresses the drift of Cu ions. The Time-Dependent Dielectric Breakdown (TDDB) lifetime of porous silica low-k covered with the ultra-thin pore seal layer results in a drastic increase of the capacitor lifetime with respect to the no-pore-seal control system (stable at 125 °C at least for 10000 s). Thermal decomposition of bulk material of the pore sealant was measured by thermal gravity (TG) test in nitrogen. Bulk material did not decompose through around 350 °C. The amount of ultra-thin pore seal layer fabricated on silicon wafer after thermal cycle stress in vacuum was measured by x-ray photoelectron spectroscopy (XPS). Amount of pore sealant did not decrease even after 2 cycles of 20 min, at 250 °C. Those results show that the ultra-thin layer, which we propose here, has a potential as a pore seal layer for porous low-k films.

We are interested in utilizing the thermo-switchable properties of precursor poly(p-phenylene vinylene) (PPV) polymers to develop capacitor dielectrics that will fail at specific temperatures due to the material irreversibly switching from an insulator to a conducting polymer. By utilizing different leaving groups on the polymer main chain, the temperature at which the polymer transforms into a conductor can be varied over a range of temperatures. Electrical characterization of thin-film capacitors prepared from several precursor PPV polymers indicates that these materials have good dielectric properties until they reach elevated temperatures, at which point conjugation of the polymer backbone effectively disables the device. Here, we present the synthesis, dielectric processing, and electrical characterization of a new thermo-switchable polymer dielectric.

Porous silicon waveguides with integrated porous silicon grating couplersare demonstrated as small molecule biosensors. Two fabrication methods arepresented for the grating couplers: standard electron beam lithography withreactive ion etching and a new technique based on direct imprinting ofporous substrates. Although the gratings fabricated using standardlithographic techniques have steeper sidewalls and enable a larger availablesensing surface area inside the waveguide, the imprinted gratings have theadvantage of rapid and low-cost fabrication. Both the lithographically andimprinted sensors are shown to have waveguide losses on the order of 10dB/cm, and both are demonstrated for detection of 16mer nucleic acids.

With the aim of addressing the material gap issue between model and real systems in heterogeneous catalysis, we exploited Pulsed Laser Deposition (PLD) to produce Pd clusters supported on ultrathin alumina films (Pd/Al2O3/NiAl(001) and Pd/Al2O3-x/HOPG). The structural properties have been investigated by in situ Scanning Tunneling Microscopy (STM) in ultra high vacuum (UHV). At first, Pd clusters were deposited by evaporation and by PLD on Al2O3 surfaces grown by thermal oxidation of NiAl(001). The system shows thermal stability up to 650 K. By PLD we deposited Pd clusters with a good size control obtained by varying the background gas pressure and the target-to-substrate distance. We then realized a

Pd/Al2O3-x/HOPG system where both Pd clusters and the alumina film are produced by PLD showing that, by exploiting the same deposition technique, it is possible to synthesize both a model system addressable by in situ STM and a thick film (∼100 μm) closer to realistic systems.

Wide Angle X-ray scattering (WAXS) and indentation hardness have been usedto study the development of crystallinity at room temperature ofbiodegradable poly(hydroxybutyrate) (PHB) and its copolymer withhydroxyvalerate (PHB/HV) containing 12% of valerate. Measurements werecarried out immediately after quenching the samples from the molten state(200 ºC) in ice water and over two weeks of storage at room temperature.WAXS showed that the crystallization of the PHB-based polymers initiatedwithin the first minutes of storage at room temperature, the copolymerdisplaying a higher rate of crystallization than the homopolymer. For allsamples, the degree of crystallinity, α, nearly reached aplateau value within the first hour of crystallization. Concurrently to thedevelopment of crystallinity, microhardness values, H,clearly rose as crystallization occurred. Monitoring the crystallization forover two weeks showed that after the rapid increase of αand H, there was a slow monotonic growth of theseproperties. A correlation between nanostructure and microhardness is foundat all stages of the crystallization process.

Progress in achieving improved performance in the generation and utilization of hydrogen depends on our ability to identify materials with optimized electrical and (photo)- electrochemical performance. Given their high volume fraction of interfaces, high chemical stability and versatility (ionic, electronic, optical property control), nanocrystalline electroceramic materials are of growing interest for advanced energy conversion and storage technologies. As grain size decreases towards the Debye length and grain boundaries come in closer proximity, space charge properties begin to dominate, resulting in modified charge transport. Through systematic variation of grain boundary properties by heterogeneous indiffusion of cations, the electronic and ionic carrier profiles in the space charge region may be altered. The relationships between space charge potential and defect profiles in the space charge regions are quantitatively analyzed, and implications for nano-ionic materials in thin film solid oxide fuel cells are discussed. From the standpoint of photoelectrochemical water splitting for hydrogen generation, optimizing the band gap, band alignments, and transport properties while retaining stability has remained a challenging objective. Novel nanocrystalline composite structures are discussed which exhibit features amenable to optimization of required properties and electrical measurements to determine key transport properties of titanium dioxide nanopowder, a photoanode material are introduced.

We have examined the change of mechanical characteristics of silicon nanocontacts with and without the pre-treatment by flowing current through the contact. The silicon nanocontact formed between silicon tips by a mechanical contact was quickly deformed during its tensile test under a transmission electron microscope, after applying over 100 μA at a high bias voltage around 15 V between tips for a short duration. In the tensile experiment, the diameter of the nanocontact easily decreased from the initial diameter of 98 nm to 30 nm and the length increased from 11 nm to 66 nm. At 30 nm in diameter, it was suddenly fractured without further elongation and became round tips with smooth surfaces. According to the close observation, the silicon nanocontact seemed amorphous. In the retraction process of the silicon nanocontact, steps moved along the surface from the neck of the nanocontact to the tip side at the speed of 7.0 nm/s. Nano-scaled round step propagations were repeated from the neck to the tip. The step propagation caused the fast thinning of the nanocontact. On the other hand, the silicon nanocontact formed at 1 V in bias voltage was gradually thinned from 42.5 nm to 1.6 nm in diameter and elongated from 2.9 nm to 61.9 nm in length. From the comparison of silicon nanocontacts with and without the pre-treatment, the silicon nanocontact after flowing substantial current showed quick deformation and had different mechanical characteristics from the silicon nanocontact without the pre-treatment.

Water stable fluorescent ZnO quantum dots (QDs) have been synthesized by wet chemical route in presence of hydrophilic capping agent polyethyleneimine (PEI) as stabilizing agent. The binding interaction of prepared ZnO QDs is studied with bovine serum albumin (BSA) protein. X-ray diffraction measurement reveals hexagonal wurtzite structure of as synthesized ZnO QDs with an average size 4-6 nm, determined using Scherer’s equation and confirmed by transmission electron microscopy (TEM). The ZnO/PEI QDs exhibit strong yellow-green emission centered at 555 nm (2.23 eV). The interaction between BSA and ZnO/PEI QDs has been studied by using spectroscopic and calorimetric methods. Static mode of tryptophan quenching in BSA by ZnO/PEI QDs indicates that a ground state complex formation is taking place between ZnO/PEI and BSA, where, the week interactions (hydrogen bonding and hydrophobic interaction) are contributing towards the stability of the complex.

Partially demineralized (DM) bone is of interest due to its promisingosteointegrative properties for advanced bone grafts. Structural features ofpartially DM (35 vol.%, 45 vol.% and 55 vol.% reduction), and untreatedcortical bone samples were studied by scanning electron microscopy.Mechanical properties were investigated by compression testing in threeanatomical directions at different stages of DM. The radial directionappears to be the stiffest and strongest bone direction for the all DMstages.