We report here a novel hybrid nanostructure for ultra-sensitive sensing applications based on surface-enhanced Raman spectroscopy (SERS). We rationally engineered gold-coated polymer pillar structures, named as gold nanofingers, in analogy to the tweezers at nanoscale, for active molecule capture and detection using SERS technique. Using nanoimprint lithography, we have demonstrated a cost effective manufacturing method of making such hybrid structures over large scale and achieve reliable enhancement factor. In particular, we have demonstrated the sensing application of the nanofinger structures for melamine and chlropyrifos. The limit of detection (LOD) of melamine in water is found to be 10 nM (1.3 ppb), and LOD of chlropyrifos (a pesticide) is found to be 1 nM (0.35 ppb), which is below the EPA tolerance level of 0.1 ppm for chlropyrifos on citrus fruits.

We present a simple one-step methodology for direct structuring of porous nanomaterials on the micro- and nano-scale. Our technique, direct imprinting of porous substrates (DIPS), relies on the application of a pre-patterned and reusable stamp to directly imprint porous substrates. DIPS is performed at room temperature and pressure in less than one minute, and circumvents the conventional requirement for resist processing and etching procedures. It is shown that arbitrarily shaped patterns and structures can be transferred to porous nanomaterials with a very high (sub-100nm) feature resolution that is primarily limited by the pore dimensions of the substrate material. DIPS is demonstrated on a wide variety of porous nanomaterials including metals, semiconductors, and insulators. Furthermore, DIPS can be utilized to locally modify material properties including pore dimensions, density, dielectric function, and surface roughness. Lastly, example structures fabricated by DIPS are discussed for their relevance to important applications ranging from drug delivery and imaging, to solar energy conversion, and biosensing.

We have developed a reproducible protocol for studying the effect ofmicrowave radiation on the mechanical behavior of Bombyx mori cocoon silk. In the course of this work, we identifiedmultiple improvements that can be made to ASTM F 1317-98, the standardaccording to which microwave oven power output is calibrated.

Exposure to microwaves does not significantly affect mechanical propertiesof silkworm silk, if samples are kept in a desiccator after degumming (orafter degumming and microwaving) and prior to testing in a dry environment.This finding contrasts with previous work in which samples were not kept ina desiccator, and were tested in a relatively humid environment.

Because the effect of microwave radiation on the mechanical behavior of silkis sensitive to ambient moisture, meaningful comparison or pooling of testresults acquired in different laboratories is contingent on standardizationof both the sample storage environment and the environment in which samplesare tested. Interpretation of the extensive existing literature on silkmechanical properties must take account of the reality that the samplestorage and testing environments are not standardized and are usually notreported.

Costly and often highly-flammable chemicals, such as hydrogen and carbon-containing gases, are largely used for carbon supply in current carbon nanotube (CNT) synthesis technologies. To mitigate related economic and safety concerns, we have developed a versatile CNT synthesis sequence, where low-cost and safe-to-handle-and-store waste solid polymers (plastics) are used for in situ generation of hydrogen and carbon-containing gases. Introduction of different waste plastics, such as polyethylene, polypropylene and polystyrene, into a multi-stage pyrolysis/ combustion/synthesis reactor allows for efficient CNT formation. This process is largely exothermic and scalable. It uses low-cost stainless steel screens to serve both as substrates as well as catalysts for CNT synthesis. This technique enables a solution for both waste plastic utilization and sustainable CNT production.

Network Identification by Deconvolution (NID) method is used to capture the heat cumulative effect in the homodyne configuration of the Pump-Probe Transient Thermoreflectance (PPTTR) experiment. This cumulative effect is very important in the interpretation of the PPTTR which is becoming widely used for the extraction of thin film thermal conductivity. We show that this intrinsic behavior can be introduced as a cumulative effect weight function in the time constant spectrum of the structure under study. We show how the main features of this weight function change when we change the laser repetition rate and/or the laser pump beam modulation frequency, and how these changes may affect the extraction of the thermal properties of the sample under study, particularly the thermal conductivity and the interface thermal resistance. Numerical simulations of the PPTTR experiment are used to validate the application of NID method. Limitations of the method will also be discussed.

Films of silver nanoparticles have optical properties that are useful for applications such as plasmonic light trapping in solar cells. We illustrate experimentally and by means of simulations how the particle shape affects the optical properties. In addition we show that these nanoparticle films can be represented by an effective medium layer with an almost identical reflectance and transmittance. The Bergman effective medium theory that we used provides a link between the nanoparticle shape and the optical properties. This insight can be used for the optical analysis of nanoparticle films and for further optimization of plasmonic solar cells.

The present work reports surface segregation in polycrystalline yttria-stabilised zirconia (cubic) including 10 mol% Y2O3 (10YSZ). The 10YSZ specimen was annealed in the range 1073 K - 1673 K in the gas phase of controlled oxygen activity. The segregation-induced intensity profiles of 89 Y, 40 Ca, 28 Si, 27 Al, 133 Cs, 197 Au and 90 Zr was measured using secondary ion mass spectrometry (SIMS). The data obtained show that (i) annealing of 10YSZ results in the formation of segregation-induced concentration gradients of 89 Y, 40 Ca, 28 Si, 27 Al and (ii) segregation-induced profiles depend on oxygen activity.

MnO nanoparticles (NPs) were surface functionalized by two different approaches, (1) using a dopamine-poly(ethylene glycol) (PEG) (DA-PEG) ligand and (2) by encapsulation within a thin silica shell applying a novel approach. Both MnO@DA-PEG and MnO@SiO2 NPs exhibited excellent long-term stability in physiological solutions. In addition, the cytotoxic potential of both materials was comparatively low. Furthermore, owing to the magnetic properties of MnO NPs, both MnO@DA-PEG and MnO@SiO2 lead to a shortening of the longitudinal relaxation time T 1 in MRI. In comparison to the PEGylated MnO NPs, the presence of a thin silica shell led to a greater stability of the MnO core itself by preventing excessive Mn ion leaching into aqueous solution.

Due to its outstanding thermal and chemical stability, single-crystal sapphire is a crucial material for high-temperature optical sensing applications. The potential for using hydrogen ion implantation to fabricate stable, high temperature optical waveguides in single crystal sapphire is investigated in this work. Hydrogen ions were implanted in c-plane sapphire with energies of 35 keV and 1 MeV and fluences 1016-1017/cm2. Subsequent annealing was carried out in air at temperatures ranging from 500˚C to 1200˚C. Complementary techniques were used to characterize the samples, including ellipsometry and prism coupling to examine optical properties, Rutherford backscattering/ion channeling for crystal defects, and nuclear reaction analysis for hydrogen profiling. Several guiding modes were observed in H-implanted (1 MeV) samples annealed above 800˚C through prism coupling, and a maximum index modification of 3% was observed in the 35 keV samples and 1% in the 1 MeV samples through ellipsometry, with the 1 MeV index variation being confirmed through prism coupling. The possible causes of the index modifications, such as H related defects, as well as implications for tailoring the refractive index of sapphire are discussed.

The rapid rate of discovery and development in the nanotechnology field will undoubtedlyincrease both human and environmental exposures to engineered nanomaterials. Whether theseexposures pose a significant risk remains uncertain. Despite recent collective progressthere remain gaps in our understanding of the nanomaterials physiochemical properties thatdrive or dictate biological responses. The development and implementation of rapidrelevant and efficient testing strategies to assess these emerging materials prior tolarge-scale exposures could help advance this exciting field. I present a powerfulapproach that utilizes a dynamic in vivo zebrafish embryonic assay to rapidly define thebiological responses to nanomaterial exposures. Early developmental life stages are oftenuniquely sensitive to environmental insults, due in part to the enormous changes incellular differentiation, proliferation and migration required to form the required celltypes, tissues and organs. Molecular signaling underlies all of these processes. Mosttoxic responses result from disruption of proper molecular signaling, thus, earlydevelopmental life stages are perhaps the ideal life stage to determine if nanomaterialsperturb normal biological pathways. Through automation and rapid throughput approaches, asystematic and iterative strategy has been deployed to help elucidate the nanomaterialsproperties that drive biological responses.

An amorphous silicon (a-Si:H) thin film transistor (TFT) circuit designed for charging of an energy storage device using a photovoltaic (PV) array is presented. The TFT circuit is fabricated at plastic compatible temperatures (∼150°C) and as such can easily be integrated within a range of platforms including flexible displays. The circuit provides a high degree of output voltage stability over a range of light intensities and device stress.

Graphene, two-dimensional layers of sp2 -bonded carbon, has many unique properties. In this paper, graphene is decorated with flower-like MnO2 nanostructures for the application in energy storage devices. The as-prepared graphene and MnO2 nano-flowers, which were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), were assembled into an asymmetric supercapacitor. The specific capacitance of the graphene electrode reached 245 F/g at a charging current of 1 mA. The MnO2 nano-flowers which consisted of tiny rods with a diameter of less than 10 nm were coated onto the graphene electrodes by electrodeposition. The specific capacitance after the MnO2 deposition is 328 F/g at the charging current of 1 mA with an energy density of 11.4Wh/kg and power density of 25.8 kW/kg. This work suggests that our graphene-based electrodes can be a promising candidate for high-performance energy storage devices.

Oxygen vacancy formation and migration in ceria is central to its performance as an ionic conductor. Ceria doped with suitable aliovalent dopants has enhanced oxygen ion conductivity – higher than that of yttria stabilized zirconia (YSZ), the most widely used electrolyte material in solid oxide fuel cells (SOFC). To gain insight into atomic defect migration in this class of promising electrolyte materials, we have performed total energy calculations within the framework of density functional theory (DFT+U) to study oxygen vacancy migration in ceria, Pr-doped ceria (PDC) and Gd-doped ceria (GDC). We report activation energies for various oxygen vacancy migration pathways in PDC and GDC. Results pertaining to the preferred oxygen vacancy formation sites and migration pathways in these materials will be discussed in detail. Overall, the presence of Pr and Gd ions significantly affects oxygen vacancy formation and migration, in a complex manner requiring the investigation of many different migration events. We propose a relationship that explains the role of additional dopants in lowering the activation energy for vacancy migration in PDC and GDC.

Interfacial polarization in electrolytes or other ionic media is a well-known phenomenon in connection with the relative surface potential difference. The created space charge affects the distribution of charge carriers in an electrolyte itself similarly to the field effects in semiconductors. This results in a number of secondary effects, from dielectrophoresis to the varied conductivity of the media. Some of these effects, including dielectrophoresis, and electric field sensing in the electrolytes, are analyzed analytically, modeled numerically, and evaluated experimentally. The physical nature of the thermoelectric effect in gels and a totally ionic field effect transistor is revealed, and the correspondence to experimental data is demonstrated.

The synthesis and self-assembly of a water-soluble, tricyclic, self-complementary heterocycle that features the hydrogen bond donor-acceptor arrays of both guanine (G) and cytosine (C) juxtaposed between a pyridine ring is presented. In solution, this tricycle, which has been termed xK1, self-assembles into Rosette Nanotubes (RNTs) that have an inner diameter of 1.4 nm. Unlike the RNTs formed from the bicyclic congener K1, we demonstrate that xK1 with its extended ð system, forms a J-type RNT assembly determined through UV-Vis, CD and fluorescence spectroscopy experiments. This observation brings the possibility of developing electrically conducting RNTs for applications in the areas of photovoltaics and molecular wires.

Based on atomistic simulations, the nonlinear elastic properties of monolayer graphene nanoribbons under quasistatic uniaxial tension are predicted, emphasizing the effect of edge structures (armchair and zigzag, without and with hydrogen passivation). The results of atomistic simulations are interpreted using a theoretical model of thermodynamics, which enables determination of the nonlinear functions for the strain-dependent edge energy and the hydrogen adsorption energy, for both zigzag and armchair edges. Due to the edge effects, the initial Young’s modulus of graphene nanoribbons under infinitesimal strain varies with the edge chirality and the ribbon width. Furthermore, it is found that the nominal strain to fracture is considerably lower for armchair graphene nanoribbons than for zigzag ribbons. Two distinct fracture mechanisms are identified, with homogeneous nucleation for zigzag ribbons and edge-controlled heterogeneous nucleation for armchair ribbons.

Automotive components, for the most part, are designed to last for the life of the vehicle. This is especially true for more expensive subsystems. As we move towards electrified vehicles with large traction batteries, it becomes increasingly important to (a) reduce the cost of the batteries and (b) improve battery life. This life challenge for the traction battery is quite different from that of most consumer electronics applications, which often require no more than a few years of life and a few hundred cycles of full charge and discharge. In this paper, we provide context for the automotive battery landscape and subsequently introduce a potential solution pathway to the cycle life problem associated with high capacity negative electrodes for lithium ion batteries. The approach is based on a solid (in the substantially lithiated state) to liquid (in the absence of significant lithium) transition for the gallium electrode. Because of gallium’s low melting point (29°C), heating the cell to just above ambient temperature transforms the electrode to a semi-liquid state, cracks vanish, to a large extent, and the electrode heals.

Carbon nanotube (CNT)-based piezoresistive strain sensors have the potential to outperform traditional silicon-based piezoresistors in MEMS devices due to their high strain sensitivity. However, the resolution of CNT-based piezoresistive sensors is currently limited by excessive 1/f or flicker noise. In this paper we will demonstrate several noise mitigation techniques that can be used to decrease noise in the CNT-based sensor system without reducing the sensor’s strain sensitivity. First, the CNTs were placed in a parallel resistor network to increase the total number of charge carriers in the sensor system. By carefully selecting the types of CNTs used in the sensor system and by correctly designing the system it is possible to reduce the noise in the sensor system without reducing sensitivity. The CNTs were also coated with aluminum oxide to help protect the CNTs from environmental variations. Finally, the CNTs were annealed to improve contact resistance and to remove adsorbates from the CNT sidewall. Overall, using these noise mitigation techniques it is possible to reduce the total noise in the sensor system by almost two orders of magnitude and increase the dynamic range of the sensors by 29 dB.

In this work we report on the infrared properties of the thermoelectric (1-x)PbTe-xPbSnS2 system with x=0.03, 0.06, 0.11 and 0.33. The results obtained by the analysis of the reflectivity spectra are discussed together with the structural and morphological characteristics obtained by XRD and SEM-EDS measurements. The system was found macroscopically homogeneous for x=0.03 and x=0.06 and phase separated for x=0.11 and x=0.33. The analyzed ~150cm-1 PbS impurity mode demonstrated a composition close to the PbTe0.98S0.02 for the major phase. The incorporation of PbSnS2 causes a reduction in plasma frequency (decrease in carrier frequency concentration) and an increase in carrier mobility.

Scholars have tried to link the dramatic rise of iron production in the Near East during the Early Iron Age with changes to the political landscape that occurred at the end of the Late Bronze Age. These attempts have been hindered by a lack of excavated iron production contexts dating to the Early Iron Age. The recent discovery of an Early Iron Age metal workshop at the site of Tell Tayinat, Turkey, provides an opportunity to reexamine some previous assumptions. Preliminary chemical analysis of metal and slag samples indicates that during the 12th century BC iron- and bronze-working were not separate, specialized industries. Instead, production of both materials took place within the same workshop context. Furthermore, this work highlights the importance of prestige goods in the Early Iron Age repertoire.