Fibre Reinforced Polymer (FRP) is becoming a valid alternative to many traditional heavy metal industries because of its high specific stiffness over the more classical construction metals. Recent trend of more complex geometry of composites is causing increasing difficulty in composite manufacturing. A method to optimize the manufacturing process is thus imposed to ensure and improve the quality of manufactured parts. Because of the irregular 3D shapes of the composites, traditional flat sensor system is becoming unfavorable and nonpractical for monitoring purpose. In this work, the current development status of a deformable microsystem for in situ cure degree monitoring of a glass fibre reinforced plastic is presented. To accommodate the non-flat shape of the composites, the proposal is to interconnect non-deformable functional island, which contains the capacitive sensor for cure degree monitoring, with meander-shaped deformable interconnections. The developed sensor system is able to withstand the manufacturing process where change of pressure and internal strain, thus force exerted on the sensor system, is involved.

We report the epitaxial growth of γ-Al2O3 on SrTiO3 (STO) substrates by atomic layer deposition (ALD). The ALD growth of γ-Al2O3 on STO(001) single crystal substrates was performed at a temperature of 345 °C. Trimethylaluminum and water were used as co-reactants. In-situ reflection high-energy electron diffraction and ex-situ x-ray diffraction were used to determine the crystallinity of the Al2O3 films. In-situ x-ray photoelectron spectroscopy was used to characterize the Al2O3/STO heterointerface. The formation of a Ti3+ feature is observed in the Ti 2p spectrum of STO after the first few ALD cycles of Al2O3 and even after exposure of the STO substrate to trimethylaluminum alone at 345 °C. The presence of a Ti3+ feature is a direct indication of oxygen vacancies at the Al2O3/STO heterointerface, which provide the carriers for the quasi-two dimensional electron gas at the interface.

The NSF-funded REU summer program in the Department of Physics & Astronomy at Howard University provided cutting-edge research opportunities in Computational Nanophysics, Experimental Nanophysics, Laser Spectroscopy, Atmospheric Physics and Superstring Theory to six undergraduate students recruited from across the U.S. The REU students were engaged in challenging research projects under the supervision of seasoned mentors across a variety of stimulating physics sub-disciplines that included: (1) computation-intensive surface nanophysics of condensed phase systems focused on the adsorption of gases in Metal-Organic Frameworks (MOFs); (2) experimental measurements using light scattering techniques on gels and polymers in the condensed phase; (3) experimental laser spectroscopy with special emphasis on Raman spectral measurements on tungsten oxide nanolayer deposited on a silicon substrate; (4) observation-based and modeling-intensive atmospheric physics project for developing better understanding of wind lidar performance under various aerosol/cloud loading and relative humidity scenarios in the U.S. and regional ozone and aerosols modeling and analysis of data recorded in West Africa; and (5) a cross-disciplinary project involving quantum theory, supersymmetry, graph theory, encryption, and super-commutative algebra and algebraic geometry with applications to string theory. Each student learned a multitude of relevant techniques related to their research projects, with the vision of teaching and nurturing knowledge, both theoretical and experimental, that will be useful throughout their academic careers both in their major discipline and in interdisciplinary research as a whole. Raman Spectroscopy, 3D Physics Modeling, Monte Carlo Simulations, Algebraic Geometry and Graph Theory are some of the techniques that the students learned that illustrate the importance of physics research in general and have wide-ranging applications in interdisciplinary studies. In addition, the students participated in field trips to the University of Maryland (visit coinciding with NanoDay), Georgetown University (cleanroom tour and research presentations), NASA Goddard Space Flight Center (visit coinciding with Science Jamboree Day), and Smithsonian Museums (coinciding with evening fireworks viewing on the Mall on July 4). The REU students gave midterm and final research presentations and submitted a research paper in refereed journal format at the end of their internship. A comprehensive assessment of the REU program was conducted by an independent project evaluator.

Shape memory alloys (SMAs) exist in different phases depending on temperature and stress level. Experimental evidence shows that SMAs oscillate between two shapes during thermal cycling. This phenomenon, known as two-way shape-memory effect, occurs due to a transformation between the austenitic phase and the martensitic phase. The two-way shape-memory behavior is studied here by molecular dynamics simulations in NiTi nanowires of different diameter to understand the effect of loading on the size-dependent behavior. Thermal cycling is performed while holding the system at zero stress and at a fixed compressive stress. At zero stress, the martensite structure formed on cooling depends on the wire diameter. However, when cooling is performed at a sufficiently large constant compressive stress, the formation of a single martensitic variant is observed for all diameters.

Zinc oxide surface states can be utilized for ultra-specific detection of biomolecules. The major challenges in using ZnO for bio-sensing are attaining enhanced sensitivity and specificity. In this study, we explore the functionalization of zinc in ZnO through utilizing the thiol bond. The purpose of this study is to demonstrate that the ZnO based sensor is capable of achieving high specificity in presence of competitive surface binding through the thiol bond. The final goal is to design an ultra-specific biosensor to detect low occurring biomolecules. In this study, we have selected cortisol as a stress marker to demonstrate quantification and detection from synthetic sweat. In order to demonstrate ultra-specificity, we have used two competitive thiol based molecules binding to zinc, a linker Dithiobis succinimidyl propionate (DSP) and reducing agent of DSP, Dithiothreitol (DTT). Electrochemical impedance spectroscopy (EIS) is used to quantify the signal obtained through various ratiometric concentrations of DSP and DTT. To validate the EIS study results, inherent fluorescence studies are done by mapping changes in green emission spectrum of ZnO before and after linker functionalization. The optimal combination in terms of highest signal is identified to be of 25mM DTT and 50mM DSP. This is implemented in the experiments performed to calibrate the cortisol concentration in synthetic sweat. This study demonstrates the detection of cortisol antigen in synthetic sweat present within the physiological levels of 8 ng/mL to 140 ng/mL.

Ag or Au nanocubes are known to be plasmonic nanoparticles with strong plasmonic fields concentrated around their corners1. When these nanoparticles aggregate the individual plasmonic oscillations of each particle begin to couple. The coupling between the two plasmonic nanoparticles is assumed to be dipolar in nature which results in an exponential red shift dependence of their localized surface plasmon resonance (LSPR) on the dimer separation2. Unfortunately, this exponential behavior is shown to fail as the separation distance between the two 42 nm nanocube dimer becomes 6nm or smaller3. Hooshmand et al4 have noted that these separation distances are marked by the formation of hot spots between the facets of the dimer.

This dipolar exponential behavior results from a treatment of the coupling between the two excited nanocubes as a coupling between two oscillating dipole moments2. As a result, the vectorial addition of all the oscillating electronic dipoles is assumed to interact with the nearest nanoparticle as a single oscillating electronic dipole. Herein we suggest that as the separation distance becomes increasingly small, the coupling between the individual oscillating dipoles on the different nanocubes becomes significant. Thus, the dipolar exponential behavior fails to accurately predict the near field coupling between two nanoparticles with small separation distances.

This leads to the realization that the interaction between the individual oscillating dipoles on the two nanocubes changes in a complicated manner as a function of separation distance. At 2nm, a good fraction of the oscillating dipoles are between the adjacent facets of the nanocubes as well as between the the corners. While at 3 nm less are in between the two facets of the nanocubes and a larger portion are localized at the corners. Thus, the coupling is not only dependent on the separation distance but also on what the separation does to the net interaction between the oscillating dipoles on each facet of the two coupled nanocubes. This results in the failure of the exponential behavior as the dipole moment on each nanocube is changing with distance in a complicated manner.

Semiconductor photocatalysis has emerged as an interesting area of research since the discovery of Honda-Fujishima effect. In this study, TiO2/MoO2/graphene composites have been prepared by a solar radiation-assisted co-reduction method, wherein ammonium tetrathiomolybdate salt and graphite oxide are reduced to MoO2 and graphene respectively along with TiO2. The method involved the utilization of focused pulses of natural sunlight using a simple convex lens, thereby eliminating the need for harmful reducing agents. The compound was characterized by XRD and SEM for phase identification and morphology. The TiO2/MoO2/graphene composite exhibits superior photocatalytic water splitting activity without using a co-catalyst. In addition, we demonstrate the electrocatalytic hydrogen production using this earth abundant catalyst, which shows high current density (60 mA/cm2) and low Tafel slope (47 mV/dec). The hydrogen evolved during photocatalysis was detected by gas chromatography.

Tin oxide is of great interest due to their potential technological applications, such as: gas sensors, energy conversion, catalysts and others. Appropriate doping can further enhance the conductivity of the SnO2 material with little loss of transparency. Isolated tin iron oxide fibers (Sn1-xFexO2-δ) with x (molar %) = 0, 2, 4, 6, 8 and 10 were prepared by the electrospinning technique. Anhydrous SnCl4, FeCl3·6H2O, different alcohols, chloroform and a polymer (PEO) were used as precursor materials. Appropriate mixture of these reagents defines the deposition solution. The samples were deposited on glass substrates and annealed at 500o C. The fibers are characterized by scanning electron microscopy (SEM), impedance spectroscopy and temperature dependence current-voltage measurements. The fibers with diameters between 2 to 12 microns were used for sensorial purpose. Thus, water vapor sensor responses were also measured and the experimental results are tested using the Freundlich isotherms model.

We study the stability of small amplitude harmonic perturbation at the interface of a gel material surrounded by air. The equations describing the system's dynamics are solved using classical perturbation methods. Assuming that the amplitude decays over time, we establish conditions for the system to return to its equilibrium state. The proposed model includes the effect of the boundary conditions and can be extended to more general situation in which the material is surrounded by an arbitrary fluid.

Single-walled carbon nanotube (SWCNT) growth from Pt catalysts by an alcohol gas source method, a type of cold-wall chemical vapor deposition (CVD), was investigated. Raman results showed that the diameters of SWCNTs grown from Pt were below 1.2 nm, while transmission electron microscopy (TEM) showed that the diameters of most Pt catalyst particles were above 1.2 nm. This suggests that SWCNT diameters were smaller than Pt catalysts particles. X-ray photoelectron spectroscopy measurements showed that reduction of Pt particles occurred during the SWCNT growth. Based on these experimental data, growth mechanism of SWCNTs was discussed.

The pH-dependence of glass corrosion rates has a well-known U-shaped form with minima for near-neutral solutions. This paper analyses the change of U-shaped form with time and reveals that the pH dependence evolves even for solutions that have pH not affected by glass corrosion mathematically corresponding to a zero surface to volume ratio. The U(t) dependence is due to changes of concentration profiles of elements in the near-surface layers of glasses in contact with water and is most evident within the initial stages of glass corrosion at relatively low temperatures. Numerical examples are given for the nuclear waste borosilicate glass K-26 which is experimentally characterised by an effective diffusion coefficient of caesium DCs = 4.5 10-12 cm2/day and by a rate of glass hydrolysis in non-saturated groundwater as high as rh = 100 nm/year The changes of U-shaped form need to be accounted when assessing the performance of glasses in contact with water solutions.

Nanomedicine is fostering significant advances in the development of platforms for early detection and treatment of diseases. Nanoparticles (NPs) like quantum dots (QDs) exhibit size-dependent optical properties for light-driven technologies, which might become important in bio-imaging, sensing and photo-dynamic therapy (PDT) applications. The present research addresses the synthesis of water-stable Cd-based QDs via a Microwave-Assisted synthesis approach using cadmium sulfate salt, and thioglycolic acid as Cd- and S-precursors, respectively. Selenide ions were available by reductive leaching of metallic Selenium in Sodium bisulfite solution. The size control and the tunability of the optical properties were achieved by a suitable control of the reaction temperature (in the 140°C- 190°C range) and reaction time (10 minutes-40 minutes). X-ray diffraction analyses suggested the development of a CdSe,S face cubic centered structure; the broadening of the diffraction peaks indicated the presence of very small nanocrystals in the samples. The average crystallite size was estimated at 5.50 nm ± 1.17nm and 3.72 nm ± 0.04 nm, for nanoparticles synthesized at 180°C after 40 minutes or 10 minutes of reaction, respectively. HRTEM images confirmed the crystalline nature and the small size of the synthesized nanocrystals. In turn, the exciton was red-shifted from 461nm to 549 nm when the reaction temperature was prolonged from 140°C to 190 °C, suggesting the crystal growth. The corresponding band gap values were approximately 2.2 eV, confirming the quantum confinement effect (bulk value 1.74eV). This red shift was also evidenced in PL measurements where the main emission peak was shifted from 507 nm to 564 nm when the samples were excited at 420 nm. A narrow size-tunable emission also was supported by the full width at half maximum (∼ 45 nm) for the synthesized nanocrystals. The reactive oxygen species generation capability of as-synthesized QDs was also investigated. The correlation between the particle size and the generation of (ROS) by the degradation of methylene blue was evident with a reduction of MB concentration from 10μM to 7.5μM and 6.7μM after 15 minutes of UV irradiation for reaction time of 10 min. and 40 min. respectively. No additional degradation was noticed after 60 minutes of irradiation.

This work studies the change microstructural and mechanical properties of an ankle prosthetic material 316LVM stainless steel, retired from a 36 year old patient. The medical grade 316LVM stainless steel was characterized by scanning electron microscopy (SEM), optical microscopy (OM), X-ray diffraction (XRD), hardness Rockwell C (HRC) and nanoindentation tests. The results showed that the ankle prosthesis has different microstructural change along the implant and presence of corrosion pits with inclusions, the mechanical properties like modulus elasticity and hardness decrease.

Cellular networks are ubiquitous in nature. Most engineered materials are polycrystalline microstructures composed of a myriad of small grains separated by grain boundaries, thus comprising cellular networks. The recently discovered grain boundary character distribution (GBCD) is an empirical distribution of the relative length (in 2D) or area (in 3D) of interface with a given lattice misorientation and normal. During the coarsening, or growth, process, an initially random grain boundary arrangement reaches a steady state that is strongly correlated to the interfacial energy density. In simulation, if the given energy density depends only on lattice misorientation, then the steady state GBCD and the energy are related by a Boltzmann distribution. This is among the simplest non-random distributions, corresponding to independent trials with respect to the energy. Why does such simplicity emerge from such complexity? Here we describe an entropy based theory which suggests that the evolution of the GBCD satisfies a Fokker-Planck Equation, an equation whose stationary state is a Boltzmann distribution.

In this work, we investigate the influence of the core-shell architecture on nanowire (1D) thermal conductivity targeting to evaluate its validity as a strategy to achieve a better thermoelectric performance. To obtain the thermal conductivity values, equilibrium molecular dynamic simulations is applied to Si and Ge systems that are chosen to form core-shell nanostructures. To explore the parameter space, we have calculated thermal conductivity values of the Si-core/Ge-shell and Ge-core/Si-shell nanowires at different temperatures for different cross-sectional sizes and different core contents. Our results indicate that (1) increasing the cross-sectional area of pristine Si and pristine Ge nanowire increases the thermal conductivity (2) increasing the Ge core size in the Si-core/Ge-shell structure results in a decrease in the thermal conductivity values at 300 K (3) thermal conductivity of the Si-core/Ge-shell nanowires demonstrates a minima at specific core size (4) no significant variation in the thermal conductivity observed in nanowires for temperature values larger than 300 K (5) the predicted thermal conductivity around 10 W m −1 K −1 for the Si and Ge core-shell architecture is still high to get desired ZT values for thermoelectric applications. On the other hand, significant decrease in thermal conductivity with respect to bulk thermal conductivity of materials and pristine nanowires proves that employing core–shell architectures for other possible thermoelectric material candidates would serve valuable opportunities to achieve a better thermoelectric performance.

We provide a general description of the operating principle of the photo-induced force microscope (PiFM), which probes the optically induced changes in the dipolar interactions between a sharp polarizable tip and the sample, in terms of classical fields and forces. We rigorously calculate the photo-induced force behavior and compare the predicted profile with experimental results obtained from a gold nanowire.

In this work we have synthesized the colloidal particles of transition metal-hydroxide (M= Ni, Co, Mn, Fe) by a simple chemical precipitation method. The surface of spray deposited CdS thin films were modified using nano-colloids to utlize them as water oxidation catalysts (WOC) for the photoelectrochemical cell (PEC). A systematic comparison of the PEC performance of modified and unmodified film is carried out to understand the role of co-catalyst. Ni(OH)2 modification yields 3.4 times higher photocurrent density than bare CdS photoanode, and exhibits hydrogen-evolution rate of 600 μmol/hr. Fe(OH)2 modified film shows best stability of 8 hours as compared to the others.