Nanosphere lithography fabricated nanostructures have highly tunable localized surface plasmons, which have been used for important sensing and spectroscopy applications. In this work, the authors focus on biological applications and technologies that utilize two types of related plasmonic phenomena: localized surface plasmon resonance (LSPR) spectroscopy and surface-enhanced Raman spectroscopy (SERS). Two applications of these plasmonic materials are presented: (i) the development of an ultrasensitive nanoscale optical biosensor based on LSPR wavelength-shift spectroscopy and (ii) the SERS detection of an anthrax biomarker.

The mechanical properties of healthy and diseased bone tissue were extensively studied in mechanical tests. Most of this research was motivated by the immense costs of health care and social impacts due to osteoporosis in post-menopausal women and the aged. Osteoporosis results in bone loss and change of trabecular architecture, causing a decrease in bone strength. To address the problem of assessing local failure behavior of bone, we combined mechanical compression testing of trabecular bone samples with high-speed photography. In this exploratory study, we investigated healthy, osteoarthritic, and osteoporotic human vertebral trabecular bone compressed at high strain rates. Apparent strains were found to transfer into to a broad range of local strains. Strained trabeculae were seen to whiten with increasing strain. Comparison of whitened regions seen in high-speed photography sequences with scanning electron micrographs showed that the observed whitening was due to the formation of microcracks. From the results of a motion energy filter applied to the recorded movies, we saw that the whitened areas are, presumably, also areas of high deformation. In summary, high-speed photography allows the detection of microdamage in real time, leading toward a better understanding of the local processes involved in bone failure.

The mechanical behavior of a helically perforated thin film structure was simulated by finite element analysis. The validity of the results was confirmed by comparison to a nanoindentation measurement performed on a nickel helically perforated thin film sample. It was found that variation of the helical pitch angle from 35° to 70° resulted in a change of 1.5 times in the elastic modulus. Since the fabrication process used to create the actual samples allows for variation of the pitch angle, this result may enable the tailoring of materials for use in micro- and nanoscale devices.

We grew high-quality epitaxial YBa2Cu3O7 (YBCO) superconducting thin films by the trifluoroacetate route on top of chemical solution deposited SrTiO3 buffer layers. We show that high lattice mismatches can be accommodated in heterostructures grown by chemical methods. Clean interfaces were observed between the different layers. The influence of the buffer layer growth conditions on the final superconducting properties was studied in depth. We have proved that the main parameter affecting the YBCO critical currents is the SrTiO3 surface roughness, which promotes the nucleation of a/b axis grains and, as a consequence, the porosity of the YBCO film. On the other hand, an improved dependence of the critical current with perpendicular applied magnetic field was observed. This suggests a strengthened vortex pinning due to a higher density of a/b axis oriented grains.

Thermally stimulated luminescence (TSL) and electron paramagnetic resonance (EPR) studies were carried out on gamma-irradiated europium-doped yttrium borate samples in the temperature range 300–600 K. TSL studies showed the presence of two glow peaks, a relatively weaker one at 390 K and an intense one at around 550 K. Room-temperature EPR spectrum of irradiated samples revealed the formation of two hole trapped radicals, namely, BO32− and O2−. Temperature variation studies showed drastic reduction in the EPR signal intensities of these radicals around 390 and 550 K indicating thermal destruction of O2− and BO32− radicals, respectively. The observed TSL emission is caused by the recombination of thermally released holes from O2− and BO32− radical ions with electrons. The energy released in electron-hole recombination process is used for the excitation of Eu3+ ion resulting in TSL glow peaks. TSL emission studies confirmed that Eu3+ acts as luminescent center for both the peaks.

The electrical and mechanical properties of conducting polymer poly(3,4-ethylenedioxythiophene) coatings on microfabricated neural probes have been evaluated by electrochemical impedance spectroscopy and nanoindentation techniques. Our results reveal that for poly(3,4-ethylenedioxythiophene) coatings, the minimum impedance correlates well with the mechanical properties. The lowest impedance films are also those that are the softest. This is consistent with microstructural observations by atomic force microscopy and scanning electron microscopy showing an increase in the effective surface area (“fuzziness”) of the coatings. The presence of these conducting polymer coatings provides an intermediate step along the interface between the devices and brain tissue. This information provides clues for the design of strategies for improving the long-term performance of these electrodes in vivo.

A recently developed fast oxide ion conductor, namely lanthanum molybdenum oxide (La2Mo2O9, LAMO), was synthesized instantaneously by a citrate-nitrate auto-ignition process at a fixed citrate to nitrate ratio of 0.3 and characterized by thermal analysis, x-ray diffraction, impedance spectroscopy, and thermal expansion measurements. Crystalline LAMO has formed instantaneously during the combustion process. The signature of the order–disorder transition of stoichiometric LAMO around 570 °C was evident from differential thermal analysis, differential scanning calorimetry electrical conductivity, and thermal expansion measurements. Though the in situ x-ray measurements did not indicate any clear evidence of a phase transition, a stepwise change in the lattice parameter near the vicinity of the transition temperature was apparent thereby confirming the phase transition to be of first order in nature. The thermal expansion coefficient of LAMO was calculated to be 13.92 × 10−6/°K at 950 °C. The present method formed phase pure LAMO instantaneously and produced sintered samples with high conductivity, namely, 0.052 S/cm at 800 °C and 0.08 S/cm at 950 °C compared to LAMO prepared through various other solution routes.

The mechanical properties of NiAl/Ni micro-laminated composites with highly gradient microstructure have been investigated. Two types of composites with different gradient microstructures were prepared by reaction synthesis. Intermetallics of type I and type II composites mainly consisted of Al-rich Ni0.45Al0.55 with variable thickness and Ni-rich Ni0.58Al0.42 with similar thickness, respectively. As intermetallic volume fraction increased, yield strength of type II followed the rule-of-mixture well, while that of type I deviated due to the composition variation of intermetallic phases. Fracture toughness of type II was higher than that of type I, and all showed KR curves with upward curvature by large-scale bridging. Even though the relative strength of constituent phases in intermetallic/metal laminates was not constant due to the gradient microstructure, the fracture mode transition showed similar behavior to that of metal/ceramic laminates.

A novel, high-resolution remote Raman microscope was used for the direct in situ assessment of deformation on bridging fibers in a double-edge-notched SiC-Nicalon reinforced ceramic-glass matrix composite at various stages of monotonic tensile loading. The effect of notch length on the bridging strain profiles obtained by individually probing a large number of fibers across the bridged ligament of the composite was investigated. Bridging strain measurements in the microscale are used to identify the role and sequence of the failure micromechanisms developing within the bridging zone and are compared with their macromechanically derived counterparts. The difference of 25% in failure strain between the as-received fiber and the maximum value obtained on composite-fibers through laser Raman microscopy (LRM), is attributed to the different patterns of fiber failure in composites as compared to the techniques used for fibers characterization such as monofilament and bundle testing in air. This article demonstrates how the LRM-strain data can be utilized to obtain a direct, microscale measure of the interfacial-shear strength of the composite. The obtained interfacial shear strength (ISS) value of 7 MPa compares well with the macromechanically predicted value and offers a much higher precision compared to other experimental techniques.

Interfacial reactions in γ–InSn4(Sn–20 at.% In)/Ni couples at 130, 140, 150, and 160 °C were investigated. Ni3Sn4 phase with significant indium solubility was formed in the couple reacted at 130 and 140 °C, and the reaction path was γ–InSn4/Ni3Sn4/Ni. For the couples reacted at 150 and 160 °C, even though both γ–InSn4 and Ni were solid phases, the liquid phase was formed in the couples. A distinguished feature was the nickel substrates becoming nonplanar with spikes at various locations and the Ni3Sn4 phase layer on top of the nickel spikes. Except at regions near the nickel spikes, the reaction layer consisted of precipitates and was not a homogeneous phase. The reaction path is γ–InSn4/Ni3Sn4/Ni at the location with Ni3Sn4 phase growing on Ni. However, if the Ni3Sn4 phase does not nucleate, the liquid phase forms at the interface with accumulation of indium atoms, and the reaction path is γ–InSn4/ liquid/liquid + Ni3Sn4/Ni.

Silicon carbide powders were synthesized by application of sol-gel processing. Fumed silica powder was used as the starting material for the silicon source, and phenolic resin was used for the carbon source. The effects of mixing ratio and difference between hydrophilic and hydrophobic types of fumed silica powders were investigated. The stirred mixtures of fumed silica powders and phenolic resin became apparent sol states owing to homogeneous distribution. SiC powders were formed derived from both the types of fumed silica powders after the gelation and pyrolysis up to 1800 °C. The hydrophilic silica powder was effective to synthesize more homogeneous SiC powders than the hydrophobic type. Single-phase SiC was obtained in the C/Si (molar ratio after pyrolysis at 1000 °C) range between 1.0 and 2.5, while free carbon was contained in the obtained powders of C/Si > 2.5. In contrast, formation of SiC was insufficient, and SiO2 was retained at ratios of C/Si < 1.0.

Titanium foams were produced by the expansion of pressurized argon pores trapped within a preform during a previous powder-consolidation step. Compared with creep expansion at 903 °C, superplastic expansion (induced by a 830–980 °C cycling around the allotropic temperature of titanium) increases foaming rate and final porosity. The pore size and fraction in the preforms were varied by using a range of initial titanium powder sizes and argon pressures. As initial preform porosity increases from 0.06 to 2.7%, foaming rate increases in the early stages of creep and superplastic foaming. However, at a later stage, foaming ceases prematurely for preforms with high initial porosity, as pores connect to the surface, allowing the escape of the pressurized argon. Preforms with 0.40% initial porosity result in foams with an optimal combination of high foaming rate, high final porosity (up to 47%), tailorable open or closed porosity, and Young's modulus as low as 23 GPa.

Nanoparticles and nanocrystalline particles of pure anatase titania (TiO2) were synthesized by solvothermal processing of TiCl4 ethanol and isopropanol solutions at 120 to 200 °C. This one-step and nonsurfactant approach is versatile and the morphology tuning can be achieved by manipulating the growth kinetics. Dispersed nanocrystals of spherical, cubic, and acicular shapes and hollow spherical and core-shell structured micrometer-sized particles were obtained under different experimental conditions. The obtained hollow spherical- and core-shell–structured particles have an average diameter of 700 nm to 1.0 μm, with an average crystallite size of 5 to 16 nm. The dependence of nucleation/crystal growth and morphology development on solvothermal medium, reaction temperature, and reactant concentration was investigated. The reaction mechanism was then suggested and tentatively discussed from coordination and solution chemistry.

Non-destructive investigation of buried interfaces at high-resolution is critical for integrated circuit and advanced packaging research and development. In this letter, we present a novel non-contact microscopy technique using ultrahigh frequency (GHz range) longitudinal acoustic pulses to form images of interfaces and layers buried deep inside a silicon device. This method overcomes fundamental limitations of conventional scanning acoustic microscopy by directly generating and detecting the acoustic waves on the surface of the sample using an ultrafast pump-probe optical technique. We demonstrate our method by imaging copper lines buried beneath a 6-μm silicon wafer; the lateral spatial resolution of 3 μm is limited by the laser spot size. In addition to the high lateral spatial resolution, the technique has picosecond (ps) time resolution and therefore will enable imaging individual interconnect layers in multi-layer stacked devices.

Polyamide 66 (PA66) nanotubes with an array structure were prepared by infiltrating a solution of normal molecular weight PA66 into anodic aluminum oxide (AAO) templates with a pore diameter of 200 nm. The results of field-emission scanning electron microscopy (FESEM) demonstrate that PA66 nanotubes with a wall thickness of about 60 nm can be fabricated by a solution-wetting method and PA66 nanotubes and nanowires can be obtained by a melt-wetting method at different temperature. We also find that PA66 nanotubes have the “super plasticity” for the crystalline belts in their wall may arrange by spiraling and rounding style. Thermogravimetric analysis (TGA) indicates the nanotubes have a better thermal stability than bulk polymer PA66. The mechanism of forming polymer nanotubes by polymer melt-wetting method has been proposed.

Electrostatic potentials within a core/shell nanowire structure, composed of an intrinsic germanium core surrounded by its oxide and a heavily doped germanium shell, were investigated by electron holographic analysis on its cross-section. The potential distribution resulting from interface charges as well as dopants was successfully imaged. The surface potential, screening length, and doping concentration for the heavily doped germanium shell were determined quantitatively from the potential image. These characteristics were compared with values obtained from a numerical solution of Poisson's equation.

In this paper, we describe the application of thin film combinatorial deposition methods to systematically control the microstructure of AlxSi(1−x) alloys through variations in composition and growth temperature. Discrete libraries of compositionally graded films have been sputter deposited onto silicon substrates to produce two structural phase regions: amorphous a-(Al–Si) and amorphous a-Si plus crystalline c-Al. The microstructure was investigated using x-ray diffraction while atomic force microscopy techniques were used to obtain surface morphology and phase distribution.

Microstructure-related local deformation behavior was evaluated using nanoindentation techniques for a type 316 austenitic stainless steel used in energy generation plants. The sample was aged for 39,332 h (4.5 years) at 700 °C. The microstructure included the σ phase precipitated at grain boundaries and in grain interiors. The nanohardnesses of the σ phase and the matrix in the aged and virgin samples were evaluated quantitatively. The hardness of the σ phase was found to be extremely high in the order of 17 GPa, which is much higher than the value of about 3.4 GPa for the matrix in the aged sample. The hardnesses of the σ phase at the grain boundary and the adjoining matrix were the same as those in the grain interior. Moreover, the hardness of the matrix of the aged sample was about 30% lower than that of the virgin sample while the Vickers hardness as a macroscopic strength of the aged sample was about 45% higher than that of the virgin one. The deformation and fracture behavior in a local region was discussed in terms of the inhomogeneous mechanical properties in the multi-phase microstructure.

Nacre, the inner iridescent layer of seashells is a model biomimetic system composed of 95% of inorganic (aragonite) phase and 5% of organic phase. Nacre exhibits an interlocked layered “brick and mortar” structure where the bricks are made up of aragonitic calcium carbonate and mortar is an organic phase. Here, we report the role of indentation load and penetration depth on measurement of nanomechanical properties of nacre. A range of loads from 10 μN to 10,000 μN were applied to obtain the response from different depths of nacre. The values of hardness and elastic modulus decrease with increasing load (i.e., increase in penetration depth). The variation in these values is significant at lower loads and decreases with increase in indentation load. From our results, it appears that the nanoindentation tests done at lower loads are highly influenced by micro and nanostructure in nacre. The indentation experiments performed at low loads indicate an elastic modulus of about 15 GPa for the organic phase. The low load, low penetration experiments appear to be better indicators of nanomechanical behavior. Also, we have observed a step-like behavior in the load-displacement curves at high load indentations on nacre. These features are attributed to the organic layer between the aragonite platelets. The indentation tests with penetration depths more than ∼250-300 nm often disrupt the organic layer and the behavior is not recovered in the unloading part of the curve. The microarchitecture and the composition of nacre contribute to the decrease in hardness values with increasing depth along with the indentation size effects.

Tantalum disulfide (TaS2) nanoplatelets were produced by laser ablation of a TaS2 target under an argon atmosphere. The nanoplatelet dimensions and morphology were characterized by transmission electron microscopy and x-ray diffraction. The effect of the ablation laser power density on the size distribution of the nanoplatelets was studied. The TaS2 nanoplatelets were prone to oxidation upon exposure to air but could be stabilized by using 3-mercaptopropionic acid as the capping agent.