Structural colors were obtained by the deposition of plant cell walls biopolymers films on reflective support. Multilayered xyloglucan(XG)/cellulose nanocrystals(CN) thin films were obtained by spin-assisted layer-by-layer assembly while arabinoxylan (AX) thin films were elaborated via the spin-coating of AX/melamine formaldehyde resin followed by a cross-linking step. The effects of aqueous solutions on the stability of the structural colors were evaluated. The films were subsequently used to detect cellulase and xylanase activities by the change in the colors due to the film degradation. This enzymatic assay method appeared to be about 150 more sensitive that a standard method. Moreover due its simplicity, the method could be used to detect other biomass-hydrolyzing enzymes and more generally for other heterocatalytic degradations of solid polymer layers.

Biomolecules rich in aspartic acid (Asp) are known to play a role inbiomineral morphology and polymorph selection, and have been shown togreatly enhance the growth kinetics of calcite. The mechanism by which thesecompounds favor calcification may be related to their effects upon cationsolvation. Using molecular dynamics, we investigated the influence of smallcarboxylated molecules on the hydration states and water exchange rates ofdivalent cations. We show that the carboxylate moieties of Asp promotedehydration of Ca2+ and Sr2+ and that contact ion pair(CIP) formation is not required to disrupt the hydration of these cations. Ca2+- Asp and Sr2+ - Asp CIP formation decreasesthe total inner sphere coordination from an average of 8.0 and 8.4 in bulkwater to 7.5 and 8.0, respectively. Water residence times estimated for Mg2+, Ca2+and Sr2+ follow the expectedtrend of decreasing residence time with increasing ionic radius. In thepresence of Asp, both solvent-separated ion pair (SSIP) and CIP formationdecrease the residence times of Ca2+and Sr2+ innersphere water molecules. Comparable impacts on Mg2+ hydration arenot observed. Mg2+ - Asp CIP formation is energeticallyunfavorable and Asp does not affect Mg2+ inner sphere waterresidence times.

Two different types of ferroelectric/semiconductor heterostructures, made up of Pb(Zr,Ti)O3/ZnO and BiFeO3/ZnO respectively, were fabricated on Pt(111)/Ti/SiO2/Si(100) by sol-gel process. Obvious diodelike behavior were observed in BiFeO3/ZnO heterostructures when current-voltage characteristics were measured, while Pb(Zr,Ti)O3/ZnO heterostructures exhibited a symmetrical behavior. It is found that Pb(Zr,Ti)O3/ZnO heterostructures showed a large polarization and the remnant polarization was approximately 15μC/cm2. The remnant polarization performed a modulation on the channel resistance. The different properties of two heterostructures might lead to different applications.

High resolution transmission electron microscopy in combination with geometric phase analysis is used to investigate the interface misfit dislocations, strain relaxation, and dislocation core behavior versus the surface treatment of the GaAs for the heteroepitaxial growth of GaSb. It is pointed out that Sb-rich growth initiation promotes the formation of a high quality network of Lomer misfit dislocations that are more efficient for strain relaxation.

The temperature dependence of yield stress and the associated dislocation dissociation in L12 intermetallic compounds are investigated in order to check the feasibility of the classification of L12 intermetallic compounds so far reported in terms of the planarity of core structures of partial dislocations with b = 1/2<110> and 1/3<112> on {111} and {001} glide planes. In contrast to what is believed from the reported classification, the motion of APB-coupled dislocations is proved to give rise to the rapid decrease in yield stress at low temperatures for Co3Ti and Co3 (Al,W). The temperature dependence of yield stress at low temperatures is newly interpreted in terms of a thermal component of solid-solution hardening, at least, for these two L12 compounds. We have proposed a new way to describe the yield stress–temperature curves of L12 compounds with three parameters (the athermal and thermal components of solid-solution hardening and the anomalous strengthening component) when the dislocation dissociation scheme is of the APB-type.

With the aim of investigating fundamental properties and nano-imprintabilities of glassy alloy in the film form, Zr49Al11Ni8Cu32, Pd39Cu29Ni13P19 and Cu38Zr47Al9Ag6 alloy thin films were fabricated on Si substrate by a magnetron sputtering method. These thin films exhibit distinct glass-tradition phenomenon and large supercooled liquid region of about 80 K, confirming as a glassy structure and have very smooth surface and sufficient hardness to maintain imprinted shape, which are suitable for nano-imprint processing. Moreover, thermal nano-imprintabilies of these obtained films are demonstrated by using a dot array mold with a dot diameter of 90 nm and a pitch of 180 nm. Surface observations revealed that periodic nano-hole arrays were successfully imprinted on the surface of these films and precisely corresponded to the periodic dot pattern of the mold. Particularly, Pd-based glassy alloy thin film indicated more precise pattern imprintability, namely, more flat residual surface plane and sharper hole edge. These results suggest that these glassy alloy thin films, especially Pd-based glassy alloy thin film have high potential for application to the nano-imprinting materials.

The room-temperature dependences of the electrical conductivity σ, Seebeck coefficient S, Hall coefficient RH, and the thermoelectric power factor P on the thickness (d=10–300 nm) of the thin films grown on mica substrates by thermal evaporation in vacuum of Bi-Sb solid solutions crystals with 4.5 at.% Sb were obtained. It was established that an increase in d up to ~ 200 nm leads to a change in kinetic coefficients and that in the thickness dependences of the thermoelectric properties, quantum oscillations were observed. It was shown that the monotonic component of the σ(T) dependence can be satisfactorily approximated by theoretical calculations based on the classical Fuchs - Sondheimer theory. The theoretically estimated period of oscillations is in a good agreement with the experimentally observed period.

A recent approach in disease diagnosis and viral epidemics is aimed atpoint-of-care tests that could be administered near the patient rather thantime-consuming processes involving centralized laboratories. Point-of-caredevices provide rapid results in simple and low-cost manner requiring onlysmall sample volumes. These devices will strongly benefit from advancedmaterials and fabrication methods to improve their efficiency andsensitivity. We report a functionalized carbon nanotube label for animmunosensor application. Carbon nanotube label was prepared by modifyingthe carbon nanotube surface to anchor biomolecules. First, the carboxylicacid treated multi-walled carbon nanotubes (MWCNTs) were uniformly dispersedwith polyvinylpyrrolidone (PVP) by sonication in aqueous solution. PVPpartially wraps around the carbon nanotubes and exposes the surface of thenanotubes for further functionalization. The MWCNTs were then conjugatedwith human immunoglobulin G (IgG) using EDC/Sulfo-NHS coupling chemistry,where the antibodies occupied sites not covered by PVP. The dispersion,surfactant modification, and antibody conjugation of the MWCNTs were alsoconfirmed using SEM and TEM images. The successful functionalization of theMWCNTs and reactivity of the covalent attached antibodies were demonstratedfor specific antigen binding on the microelectrode device. The carbonnanotube-based detection mechanism could be tailored for screening variousanalyte specific molecules. Furthermore, the reported technique could easilybe integrated in various microfluidic and lab-on-a-chip devices for thedevelopment of functional electronic sensors providing quantitative,sensitive, and low-cost detection in pointof- care setup.

Porous scaffolds of alkaline-soluble collagen including nanocompositeparticles of chondroitin sulfate and low crystalline hydroxyapatite forcartilage regeneration were fabricated by freeze-drying and thermaldehydration treatments; porous collagen scaffolds were also synthesized as areference. The scaffolds were cross-linked using glutaraldehyde (GA) vaportreatment in order to enhance biodegradable resistance. Microstructuralobservation with scanning electron microscope indicated that the scaffoldswith and without GA cross-linkage had open pores between 130 to 200 μm indiameter and well-interconnected pores of 10 to 30 μm even aftercross-linkage. In vitro biodegradable resistance tocollagenase was significantly enhanced by GA cross-linking of the scaffolds.All these results suggest that the GA cross-linked scaffolds consisting ofcollagen, chondroitin sulfate, and low crystalline hydroxyapatite havesuitable microporous structures and long-term biochemical stability forcartilage tissue engineering.

In the Bi2O3-MO-P2O5 diagram, on the basis of previous compounds based on 2D-ribbon like units, we have predicted and prepared the infinite term. It contains [Bi2O2]2+ planes arranged within a never-observed crystallographic form. In this series, the ribbons-like units are polycations built on the linkage of n O(Bi,M)4 tetrahedra along their width and infinite in a perpendicular dimension. Hence, this novel form completes the continuous series of analogue compounds, whose building units now extend from the single chain to the infinite plane, via a number of discrete n values (2,3,4,5,6,7,8,9,10,11). The presented materials of formulae Bi4MP2O12 (M= Zn and Mg) roughly show the same crystal structure. However different arrangements of the groups located between the [Bi2O2]2+ planes are at the origin of a complex superstructure in the case of the zinc compounds.

Nanotechnology, or the use of materials with one dimension less than 100nm, offers the ability to change particle reactivity by simply changing their size. This novel property of nanomaterials is used to create more effective medical treatments for cancer, tissue engineering and regenerative medicine, but the influence of nanoparticle size on environmental toxicity has not been thoroughly addressed to date. This study examines the influence of the size of silver particles on drosophila egg development by exposing their eggs to particle concentrations ranging from 10ppm-100 ppm of silver. Size, chemistry and agglomeration of the silver particles are evaluated using transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and dynamic light scattering (DLS). This analysis confirmes individual silver particle size in the ranges of 20-30nm, 100nm and 500-1,200 nm with similar chemistry. DLS and TEM data also indicates agglomeration in water; with the TEM images showing individual particles in the correct size range, but the DLS z-average sizes of the silver nanoparticle are 782 ± 379 nm for the 20-30nm silver nanoparticles, 693 ± 114 nm for the 100nm silver nanoparticles and 508 ± 32 nm for the 500-1,200nm silver particles. Most importantly, here we show significantly more drosophila egg toxicity when exposed to larger, non-nanometer, silver particles. Upon exposure to silver nanoparticles sized 20-30nm, drosophila eggs do not exhibit a statistically significant (p<0.05) decrease in their likelihood to pupate, but eggs exposed to larger silver particles (500-1,200nm) are 91% (±18%) less likely to pupate. Exposure to silver nanoparticles reduces the percentage of pupa able to emerge as adults. At 10ppm of silver particle exposure, only 57% (± 48) of the pupa exposed to 20-30nm silver particles become adults whereas 89% (±25) of the control group becoem adults and 94%(±52) and 91%(±19) of the 500-1,200nm and 100nm group, respectively, reached adulthood. In this manner, this paper provides evidence that nanoscale silver particles (<100nm) are less toxic to drosophila eggs than conventional (>100nm) sized silver particles.

Organic light-emitting diodes (OLEDs) are developing into a competitivealternative to conventional light sources. Nevertheless, OLEDs need furtherimprovement in terms of efficiency and color rendering for lightingapplications. Fluorescent blue emitters allow deep blue emission and highstability, while phosphorescent blue emitter still suffer from insufficientstability. The concept of triplet harvesting is the key for achievinginternal quantum efficiencies up to 100 % and simultaneously benefiting fromthe advantages of fluorescent blue emitters. Here, we present a stacked OLEDconsisting of two units comprising four different emitters in total. Thefirst unit takes advantage of the concept of triplet harvesting and combinesthe light emission of a fluorescent blue and a phosphorescent red emitter.The second unit emits light from a single emission layer consisting of amatrix doped with phosphorescent green and yellow emitters. With thisapproach, we reach white color coordinates close to the standard illuminantA and a color rendering index of above 75. The presented devices arecharacterized by high luminous efficacies of above 30 lm/W on standard glasssubstrates without outcoupling enhancement.

A wide information gap exists between our present atomic-scale knowledge of metal oxidation derived from conventional ultrahigh vacuum (UHV) surface science experiments and the oxidation mechanisms obtained from the growth of bulk oxide thin films under technologically relevant realistic (or near-) atmospheric conditions. To bridge this pressure gap, we present an in-situ transmission electron microscopy (TEM) study of the initial oxidation stage of Cu(100) and Cu-Au(100) surfaces where the oxygen partial pressure varies from 5x10-4 to 150 Torr. For Cu(100), with increasing oxygen partial pressure (pO2), the nucleation density of the oxide islands increases and so does the growth rate of the oxide islands. As the pO2 continues to increase, a transition from epitaxial cube-on-cube Cu2O islands to randomly oriented oxide islands is observed. A kinetic model based on the classic heterogeneous nucleation theory is developed to explain the effect of oxygen partial pressure on the oxide orientation. It is shown that such a transition in the oxide nucleation orientation is related to the effect of oxygen pressure on the nucleation barrier and atom collision rate. The Cu-Au(111) alloy revealed the same oxygen pressure dependency of the oxide nucleation orientation as pure Cu oxidation.

Materials science is an interdisciplinary field that examines the structure-property relationships in matter for its applications to many areas of science and engineering. Providing a means for intuitive development of understanding of these relationships by young learners and university undergraduates alike is critical. The effectiveness of an immersive low-cost 3D virtual reality (VR) environment was evaluated during a pilot study sponsored by the Center of Integrated Nanomechanical Systems (COINS) program. The 3D VR environment involves the use of a specialized display, sensors, computers, and immersive visual technology equipment. In collaboration with Cognitive Science investigators, our research focused on understanding the impact of the 3D VR environment on the visual ability to perceive structures in three dimensions and on quantifying the learning of COINS participants. The premise was to measure the learning of undergraduate participants in activities designed to evaluate the quality of the learning environment. Our investigation consisted of three stages in which participants learned about carbon nanotubes (CNTs) via traditional methods, physical models and virtual models. Traditional methods (2D projection graphs) were not appealing to participants and did not facilitate depth perception. Physical (ball-and-stick) models motivated participants by allowing interactivity but bond distance/angle measurements were tedious. Virtual models (3D models) offered complete manipulation, real-time measurements and the capability of mimicking realistic atomic forces (attractive/repulsive), giving the user a better insight into the structure of CNTs compared to previous methods. While immersive environments offer virtual models with some of the same benefits of physical models, it is the extended features (e.g. accurate distance representation, computer simulations capability and analysis tools for further investigations) that suggest such environments as effective learning tools for materials science education. Preliminary data analysis suggests that highly accurate perception of a molecular structure is facilitated by the use of immersive environments in which the operator may manipulate and measure important intrinsic information about the structure. Moreover, computer simulations of materials are of great scientific interest for technological progress. We are presently working on the development of the immersive 3D VR environment to perform atomistic simulations to enable scientists to perform accelerated calculations to solve problems with performance enhancements over conventional methods. Another important value in the immersive 3D VR environment lies in its expanded use for multi-disciplinary research, influencing structure-dependent applications, science learning, and design of nanodevices in fields such as materials science, chemistry, engineering, cognitive science, nanotechnology, and computer science among others.

X-ray-excited luminescence of GaN doped with Eu ions as a luminescent center was observed in the wavelength range from 350 nm to 650 nm. Three peaks at 375 nm, 550 nm and 622 nm were found. To survey the mechanism of the photoluminescence due to non-resonance excitation, photoluminescence X-ray excitation spectra are also measured. The mechanism of the luminescence occurrence was briefly discussed based on the model developed by Emura et al.

A high-quality silver mirror coating technology capable of offering various colors for the decoration of molding items is desirable. We have developed both chemical reagents and procedures for improving the silver mirror coating layers. Treatment A with a sodium thiosulfate aqueous solution is a cleaning process for the silver layers. Treatment B with a water-based solution of silane coupling agent is a process for improving the adhesion property of mirror coating layers. Both treatments improve the durability of the silver mirror coating.

Large-scale graphene sheets were grown on thin nickel film coated Si substrates using a reliable and repeatable thermal Chemical Vapor Deposition (CVD) technique. The graphene films were then transferred onto a SiO2 coated Si wafer to fabricate a 5 mm x 5 mm resistive sensor structure. Raman spectroscopy analysis confirmed the existence of graphene. Preliminary sensing results were demonstrated by the detection of hazardous gases such as NO2 and MMH (mono-methyl hydrazine). Characterization of the device channel resistivity (switching response) was conducted as a function of the analyte type and concentration. The sensor response indicates a charge transfer mechanism between the analytes and graphene.

This paper presents the preparation of multi-walled carbone nanotubes (CNTs) and CdS nanoparticles based hybrid materials. We aim at comparing two kinds of CNTs’ functionalization by thiol groups in order to demonstrate that the surface chemistry done on the CNTs can direct the morphology of the nanohybrids. Indeed, strong oxidation of CNTs leads to shorter nanotubes opened at their ends, allowing the grafting of mercaptotriethoxysilane whereas the generation of diazonium salts in presence of pristine nanotubes should lead to the functionalization of the whole lateral surface of the nanotubes. CdS nanoparticles can then be anchored to thiol groups, leading to interesting hybrid precursors for photovoltaic applications.

First principles calculations have given a new insight into the energies of point defects in many different materials, information which cannot be readily obtained from experiment. Most such calculations are done at zero Kelvin, with the assumption that finite temperature effects on defect energies and barriers are small. In some materials, however, the stable crystal structure of interest is mechanically unstable at 0K. In such cases, alternate approaches are needed. Here we present results of first principles calculations of austenitic iron using the VASP code. We determine an appropriate reference state for collinear magnetism to be the antiferromagnetic (001) double-layer (AFM-d) which is both stable and lower in energy than other possible models for the low temperature limit of paramagnetic fcc iron. Another plausible reference state is the antiferromagnetic (001) single layer (AFM-1). We then consider the energetics of dissolving typical alloying impurities (Ni, Cr) in the materials, and their interaction with point defects typical of the irradiated environment. We show that the calculated defect formation energies have fairly high dependence on the reference state chosen: in some cases this is due to instability of the reference state, a problem which does not seem to apply to AFM-d and AFM-1. Furthermore, there is a correlation between local free volume magnetism and energetics. Despite this, a general picture emerge that point defects in austenitic iron have geometries similar to those in simpler, non-magnetic, thermodynamically stable FCC metals. The defect energies are similar to those in BCC iron. The effect of substitutional Ni and Cr on defect properties is weak, rarely more than tenths of eV, so it is unlikely that small amounts of Ni and Cr will have a significant effect on the radiation damage in austenitic iron at high temperatures.