Session B1: Poster Session

Detection of DNA nucleotides by investigating the changes of electric field in the channel of opened quantum system

In the current paper the chemisorbed DNA nucleotides to a graphene sheet placed between two gold electrodes in a contact-channel-contact system were investigated. The changes of electric filed in the channel were distinguished to detection of DNA nucleotides. We used the non-equilibrium Green's function combined with the Density Functional Theory to analyze the system. The mulliken population was deciphered for graphene and nucleobases. Some other parameters in this method such as the image plane which is in close accordance with the position of the peak of induced density, the projection plot of electron difference density and electrostatic difference potential of nucleotides were extract. In this study, the nucleotides were rotated around the z-axis from 0 to 180 in steps of 20, and the isosurface plot of electron difference density of nucleotides and electron difference potential of nucleotides were shown. The qualitative and quantitative differences among these mention parameters wereconsidered as yardstick to identify DNA nocleotides. Single layer graphene which is only one-atom-thick is an excellent electrical conductor with good electronic conductivity. Here we used the graphene as a biosensor. High accuracy obtained using this method is a plus point   

Contract For Differences to Marcine Frackowiak

For CFD/Contract for Differences accompanied by "One Man's Crusade to Exonerate Hydrogen for Hindenburg Disaster" from Addison BAIN, APS News, v 9, n 7 -July 2000 sought in this context:"a transition between an economy dominated by a few individuals from a situation where the wealth is more evenly spread out"-JP Bouchaud & Mezard, 2000 . Involves the CFD/Computational Fluid Dynamics & HCCI/Homogeneous Charge Compression Ignition - Marcine Frackowiak, dissertation, 2009 of "laden & ontladen " follows "ignition of the blaze" are responsible to those May, 1937 accidents.Devotes to ICMNS 2016 invited Speakers, spintronics theirselves include active control & manipulation of spin degree of freedom ever denotes: the nano-obelisk of scanning electron microscopy of galliumNitride/GaN nanostructures- Yong-Hoon Cho, et.al:"Novel Photonic Device using core-shell nanostructures", SPIE-newsroom,10.1117/2.1201503.005864 herewith commercial activated carbon/C can be imaged directly using abberation-corrected transmission electron microscopy-PJF Harris,et.al, J.Phys.Condens.Matt, 20 (2008 ) in fig b & c images networks of hexagonal rings can be clearly be seen depicts equal etchings of Akhenaten, Nefertiti & their childrens.   

Conformational Flexibility of Xanthene-based Covalently-linked Dimers

Our group investigated metal-free molecules that accelerate oxidation of water to molecular oxygen. One avenue of our research involves an investigation of the iminium and oxonium ion dimers (2R$^{\mathrm{+}})$ as potential water oxidation electrocatalysts based on 3 catalytic steps: (1) 2R$^{\mathrm{+}} \quad +$ 2H$_{\mathrm{2}}$O $\to $ 2ROH $+$ 2H$^{\mathrm{+}}$; (2) 2ROH $\to $ RO$-$OR $+$ 2H$^{\mathrm{+}} \quad +$ 2e$^{\mathrm{-}}$; (3) RO$-$OR $\to $ R$^{\mathrm{+}}-$R$^{\mathrm{+}} \quad +$ O$_{\mathrm{2}} \quad +$ 2e$^{\mathrm{-}}$. The second step of the catalytic cycle involves the oxidation of two ROH alcohol units to generate the peroxide RO$-$OR. The relative geometry of the 2 monomer units is essential for efficient formation of the weak peroxide bond. In search for an ideally suited covalent linker that brings two ROH monomer units into the desired relative orientation, we studied conformational flexibility of 3 covalently-linker dimers (CLDs) consisting of two xanthene-based moieties connected by a diphenyl ether (DPE), 9,9-dimethylxanthene (Xan) or biphenyl (biph) as a linker. The study employs NMR spectroscopy, X-ray crystallography, and DFT calculations. As each dimer exhibits conformational degrees of freedom associated with rotations of the xanthene moiety, three different conformations are possible: \textit{In\textunderscore in}, \textit{In\textunderscore out} and \textit{Out\textunderscore out}, but only \textit{In\textunderscore in} is desirable for catalysis. While DPE(OH)$_{\mathrm{2}}$ and Xan$_{\mathrm{3}}$(OH)$_{\mathrm{2}}$ have \textit{In\textunderscore out} conformation in solid state, biph(OH)$_{\mathrm{2}}$ exist as \textit{In\textunderscore in }conformer. Solution studies show that DPE(OH)$_{\mathrm{2}}$ freely rotate on NMR timescale, but Xan$_{\mathrm{3}}$(OH)$_{\mathrm{2}}$ and biph(OH)$_{\mathrm{2}}$ are locked in \textit{In\textunderscore in} conformer.   

Wet-Sample Electron Microscopy and Dynamic Light Scattering on Microgels Particles.

Scanning electron microscopy and dynamic light scattering are employed to study the behavior of thermoresponsive polymer microgel systems, with a reversible shrinking-phase transition above 40.5\textdegree (the low critical solution temperature), under dynamic temperature conditions. In order to enable the direct imaging of the microgels in solution, a wet-sample electron microscopy methodology is developed, in which the sample is sealed behind a thin SiN window that isolates the liquid sample from the electron column vacuum. Thus the dynamics of individual microgel particles under changing temperature conditions can be imaged with the high spatial resolution afforded by scanning electron microscopy. Correlation of these measurements with the results from dynamic light scattering on microgel solutions provides unique insights into the complex behavior of these systems, which are relevant for applications in drug delivery and bio-sensing. Moreover, the development of the wet-sample electron imaging methods is relevant for other soft matter systems that are challenging to image using electron microscopy.   

Distinguishing single and multiple biomolecular bonds in an atomic force microscopy experiment

The goal of this experiment was to clearly characterize single biomolecular bonds using an AFM. However, it can be difficult to get clean force curves as a result of the formations of multiple bonds. We developed a method to distinguish multiple bonds from single bonds. To test this model we measured forces between avidin and biotin. This was accomplished by incubating the substrate in a biotin solution and taking force measurements with an avidin functionalized cantilever. The results of the experiment showed that we were able to clearly distinguish single from multiple bonds. Based on this, we were able to analyze observed rupture force distributions and obtained bonding characteristics of single avidin-biotin bonds.   

Forelimbs of theropod dinosaurs on the basis of humeral bone strength.

The humeral section modulus is evaluated for members of Ceratosauria, Carnosauria, Tyrannosauroidea, Compsognathidae, Ornithomimosauria, Therizinosauria, Oviraptorosauria, Avialae, Troodontidae, and Dromaeosauridae to determine the strength of their forelinbs. The effects of scaling are evident. The strength of humeri shorter than 20 cm show no dependence on taxon. In contrast, the strength of humeri longer than 20 cm do show a dependence on taxon. Ceratosaurs, carnosaur, tyrannosaurs, and therizinosaurs have very strong humeri. Ornithomimosaurs are observed to have humeri that are weaker than the humeri of ceratosaurs, carnosaurs, and tyrannosaurs. The humeri of the herbivorous therizinosaurs are observed to have the same strength as the humeri of ceratosaurs, carnosaurs, and tyrannosaurs.   

Effects of Advection on Reaction-Diffusion Waves

A quasi-one-dimensional reaction-diffusion-advection system is created by placing the classic model system for reaction-diffusion (RD) waves, the chemical Belousov-Zhabotinsky (BZ) reaction, in a syringe-capillary system. These RD waves are pure concentration profile changes of a specific chemical compound, without any mass transport in the solution. After initiating BZ waves at the open end of the capillary, BZ solution is pushed into the capillary against the direction of the wave propagation. By varying the advection velocity of the fluid ($v_\mathrm{adv}$), we observed its effect on the propagating speed of the BZ waves ($v_\mathrm{wave}$) and created, under certain conditions, quasi-one-dimensional standing waves. In this case, $v_\mathrm{adv}=v_\mathrm{wave}$ and the 'moving' wave seems to stand still within the capillary.   

Dynamic centrality in random subnetworks

Communication networks in social groups typically have a "scale-free" structure, dominated by a small fraction of highly-connected "hubs". This long-tail degree distribution exists even if one considers the communication that occurs on a particular day; however, it has been shown that the identity of the hubs in a real-world email network can shift dramatically from day to day, a property which has been termed dynamic centrality. In this presentation, we show that dynamic centrality arises naturally when the daily networks are simply random subsets of nodes and links from the underlying long-term network.   

The concept of metastability for one-legged standing

Standing on one foot has been characterized by a continuum between static equilibrium (standing) and dynamic equilibrium (walking). This suggests that sways of the body are important for a person to maintain the upright position and prevent a fall. We examine the center of pressure (COP) changes with visual input, and find that the character of COP dynamics is different on different time scales: it is random (stochastic) on short time scales $0 < t < 20\, \mbox{ms}$, ballistic (deterministic) on intermediate time scales $20\, \mbox{ms} < t < \mbox{200 ms}$, and random on long time scales $200 \, \mbox{ms} < t < 25 \, \mbox{s}$.   

Photoisomerization: a new way of thinking about a longstanding problem concerning UV photochemical decomposition of CH$_{\mathrm{2}}$I$_{\mathrm{2}}$ in the gas phase

Diiodomethane (CH$_{\mathrm{2}}$I$_{\mathrm{2}})$ is a naturally occurring polyhalogenated alkane that plays an important role in atmospheric and environmental chemistry, particularly in the ozone layer decomposition. For a long time it has been assumed that UV excitation of CH$_{\mathrm{2}}$I$_{\mathrm{2}}$ leads to direct photodissociation, i.e. breaking of a C-I bond and separation of polyatomic radical and halogen atom fragments without formation of any other primary product species. In our ultrafast transient absorption work powered by ultra-short (40 fs) laser pulses we show that the UV photochemistry of CH$_{\mathrm{2}}$I$_{\mathrm{2}}$ is more complicate that it was previously thought. The S$_{\mathrm{1}}$ excitation (330, 340 nm light) of CH$_{\mathrm{2}}$I$_{\mathrm{2}}$ in the gas phase leads to ultrafast isomerization of this molecule yielding the isomeric species (CH$_{\mathrm{2}}$I-I), which has been long invoked in solution phase studies as a main, solvent-cage-induced photoproduct. The presence of this isomer is manifested by a broad transient absorption band (550 nm) emerging \textasciitilde 40 fs after excitation, and decaying with a \textasciitilde 70 fs lifetime. In the gas phase, the formation of the isomeric species takes place via the direct isomerization mechanism, i.e. without need of a solvent cage, in a quantum yield \textgreater 20 {\%}. Also, the radical dissociation channel is observed in the \textless 400 nm region.   

Numerical modelling of shading induced degradation in CIGS photovoltaics

The efficiency of thin-film photovoltaic (PV) devices based on copper indium gallium diselenide (CIGS) has increased rapidly over the last few years. Despite lower cost, market penetration is hindered by uncertainty and long-term reliability issues. One important reliability issue for CIGS PV is reverse bias degradation caused by shading. In this work, electrothermal finite element simulation of CIGS modules is employed to study the effects of shading, reverse bias, and material nonuniformities. We observe that thermal runaway can occur at localized spots with lower reverse breakdown voltages relative to the surrounding area. Our calculations are compared to literature data and recent data collected at the National Renewable Energy Lab as part of this project. An important next step is to better understand the anomalous reverse current-voltage characteristics of CIGS devices. Initial efforts to study that phenomenon using semiconductor device simulation is presented.   

Photocatalytic Reductions using p-GaP Photoelectrode and NAD+/NADH Analogs

This project investigates photocatalytic reduction of protons using NAD$^{\mathrm{+}}$/NADH analogs attached to the surface of appropriate photocathode (p-GaP). The NAD$^{\mathrm{+}}$ analogs are first photo-chemically reduced to NADH analogs, then the hydride transfer from NADH analogs to protons leads to the H$_{\mathrm{2}}$ evolution. The light harvesting is achieved by NAD$^{\mathrm{+}}$ analogs (red photons) and by p-GaP (blue photons). Our initial study of the photoreduction step involved six NAD$^{\mathrm{+}}$ analog dyes, only two of which showed successful photosensitization of GaP. Subsequent femtosecond pump-probe measurements indicated that the two successful dyes are the ones with sufficiently long excited-state lifetimes (\textgreater 600 ps). The hydricities of model NADH analogs were evaluated using computational and experimental methods, and the results showed that most of the NADH analogs are excellent hydride donors. However, the proton reduction using NADH analogs occurred only in the presence of Pd as a catalyst. The results indicated that NADH analogs exhibit high thermodynamic hydricities, but sluggish hydride transfer kinetics.   

A Simulation Tool for Leakage Currents and Ion Transport in Photovoltaic Modules

The reliability of solar electricity is becoming more challenging as utility-scale photovoltaic (PV) array voltages increase to 1500 V or more to reduce system cost. Modules that are at high voltages with respect to ground can experience power loss due to potential induced degradation (PID). Leakage currents that flow between the solar cells and module frame via the dielectric packaging materials are predicators of electrochemical corrosion and other deleterious PID effects, including delamination and shunting. The shunting effect (often referred to as PID-s) has been associated with sodium ion migration and contamination of structural faults across the p-n junctions of the solar cells. In this work we report on the development of a simulation tool for leakage currents and ion transport in PV modules. By consolidating the relevant physical models of charge transport through the bulk dielectric packaging materials and along interfaces, leakage current and sodium ion distribution are calculated as functions of voltage, temperature, and relative humidity. Results are compared to data from the literature. With 3D and time-dependent capabilities, this simulation tool allows for the prediction of leakage current in outdoor environmental conditions and in damp heat stress tests.   

Synthesis of Swellable Organically Modified Silica at Various Temperatures and Concentrations

Osorb\texttrademark is the trade name for a class of swellable organically modified silica (SOMS) materials. It is remarkable in its extreme hydrophobicity, reusability, and ability to absorb many times its mass and volume in organic solvents. A range of SOMS was synthesized using different concentrations of the precursor bis(trimethoxysilyethyl)benzene (BTEB) at various concentrations and ratios of acetone to water. The highest-swelling sample absorbs 74 mL of acetone per gram of material. Temperature was also varied during production of the SOMS. At low temperature (0-25\textdegree C), dilute BTEB produces a lower-swelling SOMS, while at higher temperature (45\textdegree C) the dilution enhances the swellability of the resulting material. Tests were conducted on the samples to determine the amount of force generated by the SOMS as they swell upon exposure to acetone. Some of the 100 mg samples produced in excess of 195 N of force. The relationship between the swell properties of a sample and the force that sample generates during a swell was explored; however, no discernible correlation was found between these two properties.   

Triarylmethyl, and Acridinium Cation-Based Dyes for use as Hydrogen Evolution Catalyst

Solar energy conversion is limited by the temporal variance in solar radiation, necessitating the need for solar energy storage. One method is to use sunlight to drive uphill chemical reactions creating solar fuels, mainly hydrogen. To facilitate this we have investigated several pathways to generate fuels from abundant metal-free feedstock using sunlight. One key element in the scheme is a catalyst that can drive the reaction when given separated charges. We present select triarylmethyl (6O$+)$, and acridinium (2O$+)$ cation-based dyes that have been evaluated for their photo-catalytic behavior. Specifically redox potentials, ground state excited state radical and ionized absorptions and fluorescence spectra to measure energetics and determine viability for use with GaP as a light co-absorber.   

Evaluation of Wind Power for Ball State University

Based on two years of site-specific wind speed measurements and actual power curve performance estimates of five commercial wind turbines, a feasibility study of wind-power potential near Ball State University has been conducted. Student involvement in the form of an immersive-learning course and independent study research has formed an integral part of this project. Using measured wind speed data from the study site, estimates of the expected energy produced per year from each turbine will be presented. These results, combined with conventional costs of electrical energy, show that four out of the five selected turbines could be expected to achieve payoff of combined lifetime costs well within the turbines' estimated lifetimes. Expected savings on the cost of electrical energy range from {\$}2 million to {\$}4 million for a 25-year lifetime. Physical factors affecting the power output of the turbines, and uncertainties in the estimation of the wind power and economic feasibility projections will also be presented.   

Study on Dissolved Oxygen and Water Quality Using Physical Continuity Equations and Computational Simulations

In order to protect the survival of aquatic life, there must be a minimum amount of dissolved oxygen present in. As the physical and biological degradation continues, the biological oxygen demand increases, resulting in the decrease in dissolved oxygen available in the aquatic environment. In order to restore balance, the process of reaeration occurs, in which oxygen is added to the decreased amount of dissolved oxygen. To analyze the balance and degradation, the physical continuity equation, a one-dimensional model of oxygen concentration in a fixed control volume, is crucial to understand. The equation is based on mass flow rate balance, which is affected by oxygen removal from water through degradation of organic materials, as well as reaeration through the transfer of oxygen from the atmosphere and into the water. In this paper, dissolved oxygen(DO) and biological oxygen demand(BOD) were calculated for various water bodies including ponds, sluggish streams, and swift streams. For all water bodies, DO was depleted faster than it was replenished, but the DO of the stream dropped until the rate of deoxygenation became the same as the rate of reaeration. Depending on the range of the reaeration constants, the DO and BOD of the bodies converge to equilibrium in different ways.   

Raman spectroscopy of the interfacial charge transfer between C60 and gold

Surfaced Enhanced Raman Spectroscopy (SERS) is a significant extension of the conventional Raman method, which utilizes the fact that molecules absorbed on metal surfaces dramatically increases the Raman scatterings. While the conventional Raman can be used only with large quantities of materials, due to its very small scattering cross section, SERS allows for almost single-molecule measurements. However, along with the useful enhancements, SERS also brings changes to the spectra of molecules. One main example is the shifting of vibrational frequencies. In particular, there is experimental data of this effect for C60 molecules adsorbed on a gold surface. Curiously, not all peaks shift, only a subset. There is a hypothesis that the metal involved in SERS shares electric charge with the molecules in question, which in turn causes the change of frequency. In this work, we use Density Functional Theory (DFT) to computationally find what charge does to the Raman spectrum of a molecule and why only certain vibrations exhibit these changes. Results of this study should help to fully understand the mechanics behind SERS.   

Optimizing Dynamic Light Scattering for the Analysis of Anisotropic Nanoparticles in Solution

To further our understanding of light scattering on anisotropic soft particles, such as ELP micelles, the light scattering of anisotropic gold nanoparticles was undertaken. We used Depolarized Dynamic Light Scattering (DDLS) and Scanning Electron Microscopy (SEM) to study commercial gold nanoparticles. According to SEM, all particles were larger than the company specs by nearly two times. DLS on 1:1 nanospheres showed no rotational diffusion (VH) signal, scattering vector (q) dependence on decay rate consistent with that of spherical particles, no concentration dependence on the translational diffusion coefficient (D$_{\mathrm{VV}})$, no absorption, and a hydrodynamic radius (R$_{\mathrm{h}})$ of 12.2 \textpm 0.4nm. The 3:1 nanorods also revealed no VH signal, spherical q-dependence on decay rate, no concentration dependence on D$_{\mathrm{VV}}$, and a R$_{\mathrm{h}}$ of 20.9 \textpm 0.5nm. In addition, 3:1 nanorods experienced a change in absorbance as well as color which didn't affect particle diffusion. This was caused by the particle's ability to support a localized surface plasmon resonance (LSPR). LSPR, an optical property of gold and silver allows for the emission of plasmons when light is incident on the particle surface. DDLS on 6.7:1 rods revealed a noticeable VH signal and significant change in absorption, which did not alter diffusion properties of the particles.   

Ultrafast Hole Transfer From CdSe Quantum Dots to Nitroxide Free Radicals

Organic molecules coupled to inorganic semiconductor quantum dots (QDs) have been proposed to be interesting candidates for photocatalytic applications.$^{\mathrm{\thinspace }}$Among these molecules, nitroxide free radicals are proven to be efficient photoluminescence (PL) quenchers when coupled with II-IV QDs but the mechanism of this PL quenching has not been well-understood. Here, we assessed the mechanism of the PL quenching of photoinduced colloidal CdSe QDs by 4-Amino, 2,2,6,6-tetramethylpiperidine-1-oxyl radical (4-Amino-TEMPO). Analysis of the time-resolved photoluminescence and transient absorption spectroscopies show a hole transfer from the valence band of CdSe QDs to 4-Amino-TEMPO. This reductive quenching happens in sub-picosecond timescale. Such ultrafast hole extraction of colloidal CdSe QDs by 4-Amino-TEMPO implies that these radicals are efficient hole acceptors when coupled directly to CdSe QDs, therefore suggesting CdSe QDs/ Nitroxide free radicals hybrid systems can play a significant role in the future of optoelectronic applications.   

Controlling and Understanding the Origin of Free Carriers in Indium Nitride Nanocrystals

Over the last decade, much interest has been devoted to nitride semiconductors such as indium nitride, InN, which has led to considerable advances in both the growth of InN and understanding of its intrinsic properties.Due to its low-energy direct bandgap of 0.7 eV, large electron affinity, \textasciitilde 6 eV, large thermal and electrical conductivities and unusually small electron effective mass, InN offers tremendous potential for future optoelectronic or electronic applications. However, the growth of nanocrystalline InN still presents some important challenges, and a thorough understanding of the materials properties under quantum confinement conditions is still lacking. Because of a very large electronic affinity, InN is generally always degenerately doped, with electron concentrations that exceed 10$^{\mathrm{20}}$ cm$^{\mathrm{-3}}$. InN nanoparticles consequently show a strong localized plasmon response absorbance in the infrared region, associated with a large density of free electrons. Exploring the properties and understanding the origin of these free electrons would be a big step forward to develop high quality intrinsic InN NCs. In this presentation, we will discuss the properties and origin of the free electrons in InN NCs. Important phenomena in InN NC as well as future study will also be discussed.   

Simulating Electromagnetic Propagation through Nanowire Arrays of Varying Geometric Arrangements

Nonreciprocal devices restrict the propagation direction of electromagnetic (EM) waves and are commonly used to isolate signals in millimeter-wave (mmW) communication and remote sensing systems. Nonreciprocity in mmW components is often realized by Faraday rotation, a time reversal symmetry breaking process that rotates linear polarization direction about the axis of propagation. Faraday rotation results from the interaction of an EM wave with an anisotropic medium--commonly realized by immersing a ferrite in a static magnetic field. Artificial ferrites composed of irregularly spaced ferromagnetic nanowires embedded in dielectric membranes have been experimentally explored. We employ the finite difference time domain method to understand whether or not models that include regularly spaced nanowires will yield the same propagation results as those that include irregular spacing. In our simulations, we vary lattice geometries while keeping nanowire density constant. We model the interaction of dielectric nanowire arrays with short-wavelength EM waves (having wavelengths comparable to the nanowire spacing). Our long-term goal is to model Faraday rotation resulting from the interaction of artificial ferrites with mmWs (having relatively long wavelengths).   

Delayed Charge Transfer between CdSe Quantum Dots and Organic Radicals through Trapping-Restore-Transfer Route

Semiconductor nanocrystals, or quantum dots (QDs), are fascinating materials that have high extinction coefficients, high luminescence quantum yields, and tunable electronic properties. Charge transfer processes involving QDs is a particularly interesting area of research both fundamentally and for real life applications. Here, we combined CdSe QDs with Carboxyl-phenyl nitronyl nitroxide (CPNN) radicals to study electron transfer processes. CPNN has a significant quenching effect up the photoluminescence of QDs. From the quenching study, we found that QD-CPNN system has a delayed transfer behavior: excitons recombining faster are quenched more efficiently and vice versa. We modeled this phenomenon with a trapping-restore model, in which the exciton is stored in surface traps of QDs, and the recombination and transfer happens after the exciton was re-populated into the excited state by thermal energy. At higher concentration of CPNN, a saturation behavior of quenching was shown. We applied Langmuir Isotherm to the Stern-Volmer relationship to fit the entire quenching data. A quenching rate constant was extracted from both models and showed a good agreement on each other.   

Enhanced Emission of Nanocrystal Solids Featuring Charge-Separated Excitons.

Solution processing of semiconductor nanocrystal (NC) solids represents an attractive platform for the development of next--generation optoelectronic devices, which excitonic character enables a unique optical, electrical, and thermal behavior. In search for an enhanced light-emitting performance, nanocrystal solids are typically designed to have large interparticle gaps that minimize the exciton diffusion to dissociative sites. This strategy, however, causes a nanoparticle film to become electrically insulating, making the injection of charges inefficient. Here, we demonstrate that the exciton diffusion in light-emitting nanocrystal solids can be suppressed without compromising their electrical conductivity by using a judiciously designed core/shell nanocrystal morphology. Our study shows that solids comprising type II heterostructured nanocrystals (ZnSe/CdS) exhibit an intrinsically slower exciton diffusion to recombination centers than films composed of type I nanoparticles (CdSe/CdS). As a result, type II NC assemblies promote longer exciton lifetimes ultimately leading to a brighter emission. The slower propagation of excitons through type II solids is consistent with a reduced overlap between absorption and emission spectral profiles in these materials (large Stokes shifts), which results in a decreased FRET rate. We expect that the enhanced emission of type II nanocrystal assemblies can benefit the development of nanocrystal-based light-emitting technologies.   

Increase of the Photoluminescence efficiency of PbS Nanosheets by surface passivation.

Semiconductor nanosheets, the most promising class of nanostructured materials for future application in miniaturized optoelectronic devices, photonic circuits and can offer sustainable solutions to current energy problems. Methods to grow thin vertically aligned PbS nanosheets have recently emerged. They have revealed some novel properties, such as highly efficient carrier multiplication, long photoluminescence lifetime, enhanced optical absorption, extremely narrow emission spectra and they are exceptionally radiative/bright. We show that the luminescence efficiency of thin PbS nanosheets can be improved upto 27{\%} by passivating into a Trioctylphosphine (TOP) solution. Electron-hole photo-generation and oxidative dissolution combined with surface passivation by the lead-coordinating ligand are essential elements to improve the luminescence efficiency. The results suggest that presence of Trioctylphosphine (TOP) into colloidal thin PbS nanosheets indicating longer photoluminescence lifetime as well as better photoluminescence efficiency depending on the time. We also have extended our research by doing time and temperature dependent comparison between flat and vertical TOP treated Nanosheets to explore their different characteristics.   

The photochemistry of 1,1-di(2-pyridyl) dihydrodioxin - Copper complexes.

1,1-di(2-pyridyl)dihydrodioxin demonstrated a great affinity to form metallocomplex with Copper ion( in valence state I and II), two nitrogen atoms offer unshared electron pair to Copper and form bidentant complexes. Transient absorption spectra of 1,1-di(2-pyridyl)DHD -- Copper complexes in acetonitrile at excitation wavelength 325 nm and time delays up to 1 nanosecond were measured.   

The photochemistry of Pyridyl dihydrodioxin - Copper complexes.

Dihydrodioxine conaining pyridine rings in its structure demonstrated a great affinity to form metallocomplexes with Copper ion (in valence state I and II), nitrogen atoms on pyridines offer unshared electron pair to Copper and form bidentant complexes. Transient absorption measurements and mass spectra of those Copper complexes in acetonitrile were taken.   

Understanding the growth mechanism of PbSe Nanorods

Colloidal nanomaterials have been of great interest due to their unique optoelectronic properties. The shape and size tuning of the nanomaterials at nanometer scale results in novel optical and electronic properties. Due to a high conductivity and large multiple exciton generations, PbSe nanorods are considered great for optoelectronic applications. We have developed a procedure for nanorods synthesis. TEM images, photoluminescence, absorption and PL lifetime peaks show that the rods produced are of high quality. We have studied the role of temperature and growth time on size tuning of PbSe nanorods. We have also studied the effect of the amount of chloroalkane, the ratio of oleic acid to lead, the amount of acetic acid and water on PbSe nanorod.   

RF-Sputtered Cd$_{\mathrm{2}}$SnO$_{\mathrm{4}}$ for Flexible CdTe solar cells

Cd$_{\mathrm{2}}$SnO$_{\mathrm{4}}$ (CTO) is an interesting material as a transparent conducting oxide for photovoltaic devices. However, as-deposited CTO films show poor conductivity and transparency, so a high temperature post-deposition annealing step is required to achieve desired optical and electrical properties. Wu[1] showed that this step may be eliminated by leveraging the high temperature closed space sublimation (CSS) used for the deposition of the high efficiency CdTe absorber layer. Here, we investigate the optical and electrical properties of RF-sputtered CTO films after undergoing the CSS CdTe deposition process. The CTO layer in these devices shows nano-crystallinity with a significant improvement in the electrical and optical properties compared to the as-deposited CTO films. CdTe devices were completed on a number of substrates using CTO as transparent conducting oxide, with a best device efficiency of 14.5{\%} on a flexible Corning\textregistered Willow\textregistered Glass substrate. [1] .X. Wu, W. P. Mulligan, and T. J. Coutts, Thin Solid Films \textbf{286} (1), 274 (1996).   

Thermal Stability, from Hydrocarbon alkyl to New Bonding Modes'

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Each Hidden Extra Dimension of the Fundamental String has Special Geometry which Generates Special Frequency Mode and Time's Flux

In our vision, the geometry of each extra dimension of fundamental string plays a vital role in string motion/vibration, generation of its wavelength and special frequency mode. On the other hand, nature of time is wavy-like motion of the mater and the nature of space is jerky-like motion of the mater [Gholibeigian et. al. APS 2016, abstract {\#}D1.032]. So, each fundamental string in its motion/vibration generates different wavelength correspondence of geometry of each extra dimension and its direction which is in face front of the motion. Each direction has its own time flux (time's dimension). It means that the ``world-sheet'' of each fundamental string has its correspondence ``time-sheet'' including different time's fluxes (dimensions). So, our proposed relativistic classical equation of string theory is: $n.t_{p} \frac{\partial R}{\partial \tau }+\frac{\partial ^{2}X^{\mu }(\sigma ,\tau )}{\partial \tau^{2}}=n.t_{p} (\frac{\partial R}{\partial \sigma })+c^{2}\frac{\partial^{2}X^{\mu }(\sigma ,\tau )}{\partial \sigma^{2}}$, In which $R=f(mv,\sigma ,\tau )$ is time's flux, $X^{\mu }$ is space-time coordinates of the string, $\sigma \& \tau $ are coordinates on the string world sheet, respectively space and time along the string, string's mass $m,$ velocity of string's motion$ v,$ factor$ n$ depends on geometry of each extra dimension \quad which relates to its flux time and $t_{p} $ is Planck's time.   

Synthesis of Piezoelectric Polymer Films

The significance of polymer films in the biomedical and engineering industries continues to rise. Polyvinylidene diflouride (PVDF) is a chemical compound used to synthesize these polymer films. PVDF films exhibit piezoelectric properties; therefore, when pressure is applied to the PDVF film, it generates an electric charge. This property allows PVDF films to be utilized for a broad range of applications including pressure sensors, electronic switches, ultrasounds, blood pressure detectors, and artificial skins amongst others. We are currently interested in producing PVDF polymer films with strong piezoelectric effects and determining how modifications during synthesis affect their properties. The characterization of the polymer films has been accomplished through Fourier Transform Infrared Spectroscopy (FTIR), Raman Spectroscopy, and X-ray Diffraction (XRD). We found that introducing Fe$_{\mathrm{3}}$O$_{\mathrm{4}}$ and Co$_{\mathrm{x}}$Fe$_{\mathrm{3-x}}$O$_{\mathrm{4}}$ magnetic nanoparticles, changing the annealing duration, and varying the annealing temperature altered the properties of the PVDF films. Understanding how the synthesis method of a polymer film can influence its piezoelectric properties is a first step in the development of PVDF film technology.   

Matchstick Forests: Studying Fire Spread On Hills Using a Scaled Model

A scaled forest was created using matchsticks attached to an aluminum plate with a flame resistant putty. The setup allowed for one end of the the aluminum plate to be raised, creating a constant positive slope of $\tan\theta$. The use of a 3D-printed grid to align the matchsticks ensured that the matchsticks had a constant spacing and were perpendicular to the ground regardless of the angle of the aluminum plate. By lighting one end of the matchstick grid on fire and recording the flame propagation across the grid, the rate of spread of the fire $R$ was measured. We investigated whether or not this setup could be used to predict the relationship between $R$ and $\theta$ and could be scaled up to analyze real forest fires.   

Comparison of Corrections to the Helmholtz and Schrodinger Equations using First Order Perturbation Theory

We studied the effects of a photonic correction term, derived from Maxwell's equations, to the Helmholtz equation by comparing it to the electron's relativistic correction term to the Schrodinger Equation that derives from the Dirac Equation. These correction terms are found in differential equations of the form $H\Psi + H'\Psi = \lambda\Psi$ where $H$ is the Helmholtz or Schrodinger Hamiltonian without the correction, $H'$ is the correction, $\Psi$ represents the eigenfunctions, and $\lambda$ the energy eigenvalues. We examined the photon correction term in the case of a spherically symmetric refractive index, which acts as an analog to a spherically symmetric potential for the electron. Using first order perturbation theory, we calculated the first order corrections to the photon's frequency given by the eigenvalues of the Helmholtz equation. The first order photon frequency corrections were examined by comparing the energy level diagrams of the electron and the photon.   

Preliminary experiments to map the plasma sheath edge above a step electrode

We describe an experimental method to measure the shape of the plasma sheath edge above a step electrode using microscopic dust particles. A plasma is created around a step-shaped electrode, and dust particles are dropped from above onto the high side of the step. The dust particles become negatively charged in the plasma and slide along the sheath edge, which roughly conforms to the step geometry. A sheet of laser light illuminates the particles for video capture. The particle trajectories give the sheath edge shape.~ Preliminary experimental results may be presented.   

A Photon Needs a Package of Information and Law to Move a Planck Length

A photon needs to get a package of complete information including laws about its quantum state for processing and selecting its next step. Its next step which is moving a Planck's length, takes a Planck time. The processed information is carried by the photon and is added to the history and entropy of the universe. In other words, in each second, a photon processes $1.8\times 10^{43}$packages of information for finding its path. A package of information including the new quantum state of the photon should always be available for photon during a Planck time. Information is communicated from dimension of information, which may be in addition of space-time's dimensions, with all particles and space-time. Based on our vision, the stored soft super-translation hairs in terms of soft gravitons or photons on black hole's horizon, or stored information on a holographic plate at the future boundary of the horizon [Hawking et. al., Jan 5, 2016], can be only accessible for those particles (gravitons and photons) which are in those positions, not for other particles in other locations of black hole which are far from the horizon and need packages of information during each Planck time.   

Identification and Characterization of Long Period Variable Stars in M69

We will be analyzing multiple band digital images to identify and characterize long period variables (LPVs) in the globular star cluster M69. Previous observations searching for short period variable stars identified over 50 potential variable stars, many of which appear to be LPVs. We are using images taken between 2009 and 2014 in the V and I bands to identify, photometer, and determine the period, amplitude, and mean magnitudes of these additional variable stars to classify their variability types. Our ultimate goal is to improve the census of variable stars in globular clusters and provide observations to constrain stellar pulsation models.   

Measurement of Thermal Effects in the Dispersion Relation of the Dust Acoustic Wave

A complex or dusty plasma is a four-component plasma system composed of ions, electrons, neutral particles and charged microparticles. The presence of these charged microparticles reveals different plasma phenomena, including a new wave mode known as the dust acoustic, or dust density, wave (DAW). The DAW is a low frequency, longitudinal mode that propagates through the microparticle component of the dusty plasma system and is self-excited by the energy from the ions streaming through this component. In recent years the DAW has been the subject of intense study and has provided a way to examine the thermal properties of the microparticle component. In this presentation, we report the results of an experimental study examining the thermal effects in the dispersion relation of this wave mode over a range of neutral gas pressures.   

Observation and Analysis of KIC 8462852: Occultation by Comets or Civilization?

A particularly interesting star, KIC 8562852, recently became famous for its enigmatic dips in brightness. The interpretation broadcast by many popular media outlets was that the dips were caused by a megastructure built around the star by an intelligent civilization. The best scientific hypothesis relies on a natural phenomenon: the break-up of a comet orbiting the star. To further address this problem, we have measured the star for four months using BGSU's 0.5m telescope and digital CCD camera, and we present the star's brightness as a function of time. Using three very clear nights, we refined the brightness of four comparison stars which can be used by the local astronomical community to monitor the star's brightness. These newly refined magnitudes should reduce the uncertainties in our brightness measurements; this error analysis is essential in determining the significance of any brightness deviations. An observed dip in brightness would confirm the comet hypothesis by establishing a cyclical pattern, or may serve as a basis for new understanding of variable stars. An additional element to the project involves creating CCD calibration images and a well-documented procedure for future use.   

The virial theorem: a discussion through examples

The virial theorem expresses a simple relation between the time averages of the kinetic and the potential energy of a mechanical system. We will discuss its general proof and will illustrate it with a series of examples.   

Evolution of nonlinear ion-acoustic pulses in cylindrical plasma

We simulate the propagation and evolution of large-amplitude, compressive, ion acoustic pulses in plasma for a cylindrical geometry. The code is a hybrid simulation with particle-in-cell ions and Boltzmann electrons. We initialize the simulation with an inward propagating (i.e., moving toward smaller radii $r$), planar Korteweg-deVries (KdV) soliton, and follow its evolution in time. We find supersonic pulses where the pulse amplitude is directly proportional to the speed increment above the ion acoustic speed in agreement with KdV theory. Due to the cylindrical geometry, the pulse amplitude increases proportionally to $r^{-1/2}$. However the pulse profile is not stationary and the pulse develops a significant tail for smaller $r$.   

Hydrothermal synthesis of carbon nanospheres.

Carbon nanospheres were synthesized via green chemistry approach by polycondensation reaction of glucose under hydrothermal conditions from 140$^{\mathrm{o}}$C to 190$^{\mathrm{o}}$C for 6 hours. The final black products were centrifuged and washed with ethanol and water and dried under vacuum for 48 hours. The synthesized particles were characterized by TEM, SEM, XRD, TGA, and Raman spectroscopy to assess morphology, crystallinity, presence of required phase, phase transition, and the presence of impurity. The synthesized particles are highly dispersed and spherical with size ranges from 26 nm to 300 nm. Raman peak at 1580 cm$^{\mathrm{-1}}$ corresponds to graphitic presence and the overall experimental result depicts that 170$^{\mathrm{o}}$C for 6 hours of autoclaving is an optimized condition for high dispersity and good morphology.   

An alternative approach to extended Drude model

The original Drude model, proposed over a hundred years ago, is still used to determine optical properties of solids. Within this model both the plasma frequency and quasiparticle scattering rate are constant, which makes the model rather inflexible. In order to circumvent this problem, the so-called extended Drude model was proposed, which allowed for the frequency dependence of both the quasiparticle scattering rate and the effective mass. In this work we will propose an alternative approach to the extended-Drude model. In the new approach we will assume that the quasiparticle effective mass is frequency independent, but the plasma frequency is frequency dependent. The new model is applied to several different materials, such as a high-Tc superconductor Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ (Bi2212) with T$_c$= 92K and a conventional superconductor 2H-NbSe$_2$ with T$_c$= 72 K.   

Analysis of Debye Scattering of 2-D and 3-D Simulated Carbon Crystals for Comparison with Electron Diffraction Patterns of Graphitic Stardust

The objective of this research is to understand the structure of graphitic stardust found in primitive meteorites (e.g. the Murchison meteorite). The meteoritic carbon formations of interest exhibit a core-rim structure, where the core -- with a density less than that of the graphitic rim -- comprises the majority of the grain. There is reason to hypothesize that the cores of these grains are the result of the rapid freezing (quenching) of a liquid carbon droplet. In order to understand these structures, simulated 3-D carbon crystals were rapidly quenched from a gaseous state using the molecular dynamics (MD) simulation software, GROMACS. The resulting condensates from these simulations have been analyzed using radial distribution function (RDF) calculations and Debye scattering calculations. In addition, it was necessary to understand how individual layers of differently shaped graphene sheets affect Debye scattering. Therefore, the Debye formula was also applied to simulated 2-D crystals -- different sized apex-angled triangular shaped graphene sheets - using the research software, Mathematica. The Debye scattering patterns from the 2-D and 3-D crystals were then compared with the experimental electron diffraction data from the stardust.   

Dual Frequency AFM Using an Analog Processing Module.

Understanding the distribution of cell receptors on live cells is an important part of understanding how cells interact with their environment. Such understanding can be vital in understanding many diseases, including cancer. Our goal is to efficiently and accurately map a biological cell for both topography and specific binding sites simultaneously. This project focuses on testing the feasibility of dual frequency signal processing using a universal analog signal processing module (UASPM) in tandem with any atomic force microscope (AFM). The scope of this study includes the design, construction, and testing of this universal analog module. ~This UASPM will first sum the signals from two lock-in amplifiers with minimal noise to produce the desired probe drive signal; ~the lower frequency will match the resonance frequency of the functionalized cantilever and the higher frequency will be an overtone. The UASPM will then split and ~\textonehalf wave rectify the photo-diode output from the AFM. Both the \textonehalf wave rectified output and the raw output will then be fed back to their respective lock-in amplifiers for processing: The lower frequency will allow the intermittent contact mode (IC) to map topography while the rectified higher frequency will map specific bonding regions and test quantitatively for bond stiffness. The UASPM should be universal and function in tandem with any AFM setup supporting IC, peak-force, or other AC modes and a BNC pinout.~   

Corrected Band Gap Of Zinc Oxide ZnO using DFT + U

ZnO is a wide band gap semiconductor with potential for many electronic applications. The major challenge of ZnO is the problem of controlling defects. Unfortunately, DFT has limitations that lead to underestimated values of the energy band gap, which is critical for the energetics of defects. In this work, we employ DFT+U and HSE functional calculations to study native point defects and formation energy for ZnO Wurtzite structure. The incorrect DFT band gap was calculate to be 1.1 eV. The extremely costly HSE calculations led to an improved band gap value of 2.5 eV, which is still significantly smaller than the experimentally observed 3.4 eV. In order to make a major improvement we use the Hubbard correction (DFT+U), which introduces on-site corrections for Zn 3d and O 2p electrons. We performed a large set of calculation covering a broad range of all possible combinations U-parameters for Zn and O, and found that the right band gap of 3.4 eV can be obtained by using numerous combinations. Such ambiguity leads to a poorly - defined methodology and probably unreliable results. In order to resolve this ambiguity, we use the concept of relating the U - corrections to the electronegativities of the atoms, which gives a physically meaningful criteria for choosing U-parameters.   

All-or-none folding of tethered polymer arrays

In this work we study the all-or-none folding transition of polymer chains tethered to a surface. This type of transition, similar to the folding transition of small proteins, provides a potential "on/off" switch to change surface properties and thus may be useful for smart-material and sensor device applications.  We model the polymers as square-well-sphere chains and carry out Wang-Landau computer simulations.  These simulations give the density of states, and thus the partition function, from which we can extract all thermodynamic information needed to study phase transitions. Here we investigate small arrays of chains of length N, end-tethered to a hard surface with tethering sites separated by distance $\Delta$x.  For large enough $\Delta$x the chains undergo independent folding transitions, whereas, for small $\Delta$x the chains undergo a cooperative transition, co-folding into a single crystallite.  This multi-chain transition involves a larger free-energy barrier than the single-chain transitions and thus has stronger "on/off" character.   Effects of chain length, array size, and array geometry are also explored.   

Dynamic properties of the Kondo state: proposal for an investigation of the linear response

Electronic correlations give rise to unusual properties of matter that range from superconductivity to exotic magnetic states. Kondo spins are examples of quantum systems whose properties are dominated by the correlation effects and can be studied in Single-Electron transistors (SETs) where the spin confinement can be tuned electrically. We have recently shown [1] that transport through SETs becomes non-adiabatic when the spin confinement potential is modulated with frequencies $\hbar \omega$ comparable to the Kondo temperature, typically 10-20 Ghz in our SETs. Here, we present a method for a direct observation of the {\em reactive component} of the Kondo-induced current in SETs. This measurement is expected to provide a more direct comparison of transport data to predictions for the full linear response of SETs in the Kondo regime than the previous measurements of the time-averaged conductance of Kondo states subjected to microwave radiation. We will present a detailed analysis of the new detection technique and compare the method to earlier experiments on Kondo dynamics via transport and light scattering measurements. [1] Bryan Hemingway, Stephen Herbert, Michael Melloch and Andrei Kogan, {Dynamic response of a spin-1/2 Kondo singlet} PRB {\bf 90}, 125151, 2014.   

Biolabeling Through the Use of Water-Soluble Colloidal Quantum Dots

Nanomaterials continues to be a growing field of study due to their wide range of potential applications. Quantum dots are artificially synthesized crystalline clusters of atoms able to confine electron motion as a result of their incredibly small size. Recently, medical applications of nanomaterials have expanded greatly. Quantum dots are ideal for biolabeling due to their rather narrow photoluminescence emission peaks. By synthesizing quantum dots of a specific diameter, it is possible to predetermine the peak photoluminescence wavelength of a sample. Through ligand exchange and immunoconjugation of the quantum dots with proteins, it is possible to use the quantum dots as biolabels to study the inner machinations of the cellular world. These processes have a predictable effect on the properties of the quantum dots: most importantly, their photoluminescence peak wavelength. By understanding the ways in which these processes effect the quantum dots, it is possible to choose the correct quantum dots for a specific final emission wavelength. Further research is being conducted to perform bio-imaging using these processes and resolve some current limitations found therein.   

A robust method for the synthesis of colloidal PbS nanosheets

Two dimensional colloidal PbS semiconductor materials are interested in low cost and easy processable thin plate optoelectronic and photovoltaics devices such as solar cells and transistors. Here we report a robust method by which colloidal PbS nanosheets can be synthesized with nearly 100{\%} success rate. It is achieved by replacing lead acetate with lead oxide to prepare the lead precursor for the reaction. Acetic acid either injected externally or produced during the reaction has a significant effect on the growth of the nanosheets by turning them into three-dimensional clusters. In the new synthesis, the purity of trioctylphosphine (the co-solvent for sulfur precursor) has no significant effect on the formation of nanosheets. Thickness tunability is also achieved in the acetic-acid-free synthesis.   

Thickness-tunable synthesis of Two-dimensional PbS/CdS heterostructure.

Emissive PbS/CdS core/shell nanosheets are synthesized using cation-exchange methods. A significant blue-shift of the photoluminescence is observed, indicating a stronger quantum confinement in the PbS core as its thickness is reduced to eight atomic layers. High resolution transmission-electron-microscopy images of the cross-sections of the core/shell nanosheets show atomically sharp interfaces between PbS and CdS. Accurate analysis of the thickness of each layer reveals the relationship between the energy-gap and the thickness in an extremely one-dimensionally confined nanostructure. Photoluminescence lifetime of the core/shell nanosheets is significantly longer than the core-only nanosheets, indicating better surface passivation which means a more significant potential for energy application.   

Low Temperature Current Density-Voltage Measurements of CdTe Solar Cells with Single Walled Carbon Nanotube Back Contacts: Determining Carrier Transport Mechanism and Barrier Height

Current density-voltage (JV) characteristics of CdTe solar cell with single walled carbon nanotube (SWCNT) back contacts were measured as a function of temperature to determine the charge transport mechanism and the barrier height between the SWCNTs and CdTe. The JV characteristics under forward bias were used to determine if the charge transport mechanism was thermionic emission (TE), a drift and diffusion mechanism, or tunneling for each temperature. The back contact barrier height was determined by determining the saturation current density as a function of the temperature. For SWCNT back contacts the transport of majority carriers through the back contact in the temperature range from 300 K to 180 K is limited by drift and diffusion rather than by thermionic emission. Below 180 K, tunneling becomes the dominant process for charge transport. The barrier height for a SWCNT contact is lower than that of the standard Cu/Au back contact. Interestingly, it appears to be nearly constant for SWCNT films independent of the work function of the metal overlaying the SWCNTs   

Thermoluminescence during phase transition

Low-temperature thermoluminescence (TL) has been applied to investigate the behavior of red emission in SrTiO$_{3}^{\, }$bulk single crystals during phase transition. We observed a TL peak close to the phase transition temperature which makes the peak very narrow in terms of temperature and wavelength. Also, different heating rates have been used to study the unusual behavior for kinetics of TL process in SrTiO$_{3}$. The measurements reveal that by increasing the heating rate the TL peak shifted to the lower temperatures which is not commonly observed in other materials.   

Elasticity-Driven Backflow of Fluid-Driven Cracks

Fluid-driven cracks are generated by the injection of pressurized fluid into~an~elastic medium. Once the injection pressure is released, the crack closes~\sout{up}~due to elasticity and the fluid in the crack drains out of the crack through an outlet, which we refer to as backflow. We experimentally study the effects of crack size, elasticity of the matrix, and fluid viscosity on the backflow dynamics. During backflow, the volume of liquid remaining in the crack as a function of time exhibits a transition from a fast~decay at early times to a power law behavior at late times. Our results at late times can be explained by scaling arguments balancing elastic and viscous stresses in the crack. This work may relate to the environmental issue of flowback in hydraulic fracturing.