Bulletin of the American Physical Society
Joint Fall 2013 Meeting of the Texas Sections of the APS, AAPT, and Zone 13 of the SPS
Volume 58, Number 10
Thursday–Saturday, October 10–12, 2013; Brownsville, Texas
Session C2: Nanoscience |
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Chair: Karen Martirosyan, Unversity of Texas at Brownsville Room: UBCB 1.108 |
Friday, October 11, 2013 2:00PM - 2:12PM |
C2.00001: Improved Numerical Model of Diffraction Patterns Produced by Synthetic Opals Implementing Finite-Size Sphere Scattering Liliana Ruiz Diaz, Malik Rakhmanov We continue our investigation of diffraction patterns produced by synthetic opals which are self-assembled photonic crystals. These opals consist of domains in which silica nanospheres are arranged in roughly uniform crystalline structures. Our previous experiments showed that these structures produce particular diffraction patterns when light is incident on a single domain. In an attempt to understand these patterns, we created a numerical model in which the nanospheres were represented by lattice points. In order to obtain a more accurate simulation we now replace the lattice points by dielectric spheres which scatter light according to Maxwell equations. This new model leads to a more realistic picture of the diffraction patterns. It allows us to modify the crystalline structure of the opal, change the physical properties of the nanospheres, and include defects. [Preview Abstract] |
Friday, October 11, 2013 2:12PM - 2:24PM |
C2.00002: Pressure discharge characteristics in the nanoenergetic systems with hydroxides Tyler Trevino, Mkhitar Hobosyan, Karen Martirosyan The growing demand on energetic materials created a new branch of nanotechnology which utilizes the methods of synthesis and characterization of nano-sized particles to produce so called Nanoenergetic Gas-Generators (NGG), which are alternatives to traditional energetic materials including pyrotechnics, propellants, primers and solid fuels. The thermite systems are pyrotechnic mixtures of metal powders and metal oxides that generate an exothermic oxidation-reduction reaction, releasing large amounts of energy at extremely high temperatures. The intimate contact significantly enhances and gives the ability to build an energetic material in molecular level, which is crucial for the pressure discharge efficiency of nano-thermites. The DTA-TGA, Zeta-size analysis and FTIR technique were performed to characterize the Bi(OH)3 particles. The self-assembly of Aluminum and Bi(OH)3 was conducted in sonic bath with appropriate solvents and linkers. The resultant thermite pressure discharge values were tested in modified Parr reactor. Overall, the self-assembled thermites give much higher-pressure discharge values than the thermites prepared with conventional roll-mixing technique. [Preview Abstract] |
Friday, October 11, 2013 2:24PM - 2:36PM |
C2.00003: Carbon Nanotubes Forests and Yarns for Nanoenergetic Materials Patricia Martinez, Anvar Zakhidov, Karen Martirosyan, Mkhitar Hobosyan A novel nanoenergetic yarn composite was fashioned by composing multi-walled carbon nanotube (MWCNT) sheets embedded with Al-I$_{2}$O$_{5}$ clusters, a nanoenergetic material (NM) whose volumetric energy is two orders of magnitude greater than that of Trinitrotoluene (TNT) and with a detonation velocity of approximately 2500 m/s. The NM/MWCNT composites were spin-twisted to create nanoenergetic yarns. MWCNTs were selected as the substrate matrix due to their unique intrinsic properties of high heat dissipation, high tensile stress and elasticity, all of which can be used in the manipulation and distribution of thermal energy during the nanoexplosions of the Al-I2O5 clusters. The detonation of the composite showed that MWCNT do not burn, but rather, they direct the explosion of NM along the twisted yarn. The thread-like structure of the composites allows the utilization of textile technologies to create complex weaves which can be used in new industrial and scientific applications as nanoexplosive fabrics with desired energetic properties. [Preview Abstract] |
Friday, October 11, 2013 2:36PM - 2:48PM |
C2.00004: Simulation of Reaction Time in Spherical Aluminum Oxide Nanoparticles During Rapid Oxidation Zamart Ramazanova, Maxim Zyskin, Karen Martirosyan Kinetics of oxidation of metal nanoparticles acquired practical importance with rapidly developing nanoenergetic systems and materials. Nanoenergetic thermites include mixtures of Al and metal oxides in nanoscale. Our research focuses on modeling aluminum combustion of nano-sized particles, surrounded by rich amount of oxygen stored by oxides. Oxidation kinetic of spherical aluminum nanoparticles was evaluated by using Cabrera- Mott moving boundary mechanism. The self-consistent Cabrera-Mott electrical potential was determined by solving a nonlinear Poisson equation. Motion of the oxide layer boundary was determined from the gradient of the potential on the boundary (appearing as a Gibbs factor), leading to computation of reaction times. We estimated the reaction time for several different Al nanoparticles sizes and oxide thicknesses, with initial outer/inner oxide layer radius of (a) 5-3 nm; (b) 5-4nm; (c)10-7nm; (d)10-9; (e) 25-22nm; (f) 25-24nm. Our results show dramatic increase of oxidation rate at nanoscale. Nonlinear effects, as well as self-heating, play important role in increased oxidation rates. [Preview Abstract] |
Friday, October 11, 2013 2:48PM - 3:00PM |
C2.00005: Novel Upconversion Nanoparticles for Biomedical Imaging Applications Brian Yust, Francisco Pedraza, Dhiraj Sardar With the confluence of biology, chemistry, and physics now being a reality in many hot topics of research, nanoparticles are being translated into the realm of biomedicine as novel biomarkers, sensors, and therapeutic agents. In particular, rare-earth ions doped into fluoride, oxide, and oxysulfide nanocrystals exhibit extraordinary optical properties which are useful for biomedical applications including sharp absorption and emission lines in the visible and near-infrared (NIR) and long fluorescent lifetimes. Rare-earth based nanomaterials are advantageous as biomarkers because they do not photobleach like organic fluorophores, require lower power excitation sources, and do not blink such as quantum dots. Here, we present the optical characterization and upconversion quantum yield of KYb2F7:Er, Tm. The strong NIR to NIR upconversion emission is ideal for bio-imaging since light in the NIR regime is not strongly scattered or absorbed by most soft tissues. Finally, the nanoparticles are incubated with monkey retinal endothelial cells in order to determine toxicity, and nonspecific cell uptake is imaged using multiphoton microscopy. [Preview Abstract] |
Friday, October 11, 2013 3:00PM - 3:12PM |
C2.00006: Highly Efficient Near Infrared to Near Infrared Photoluminescence in GdF$_{3}$:Nd$^{3+}$ Nanoparticles for Bioimaging Madhab Pokhrel, L. Chris Mimun, Ajithkumar Gangadharan, Brian Yust, Ashish Dhanale, Liang Tang, Dhiraj Sardar There is an increasing interest in rare earth (RE) doped nanoparticles due to their sharp absorption and photoluminescence (PL) in the near infrared (NIR) spectral region. These NIR based nanoparticles could allow biological imaging at substantial depths with enhanced contrast and high spatial resolution due to the absence of auto fluorescence in biological samples under infrared excitation. In this conference, we present the highly efficient infrared photoluminescence in GdF$_{3}$:Nd$^{3+}$ nanoparticles under 800 nm excitation within the hydrodynamic size limitations for bio-applications. The downconversion (Stokes emission) absolute quantum yield (QY) measurements in powder, poly maleic anhydride- alt-1- octadicene (PMAO) coated powder and colloidal solutions have been investigated. QY measurements have revealed that downconversion QY in an average 5 $\pm$ 2 nm sized GdF$_{3}$: 1{\%} Nd$^{3+}$ colloidal nanoparticles are 200 times higher than efficient upconversion (UC) particles NaYF$_{\mathrm{4}}$: 20 {\%} Er/ 2{\%} Yb of same size. Furthermore, the utility of these NIR emitting nanoparticles in infrared bioimaging will be demonstrated by confocal imaging and spectroscopic study. [Preview Abstract] |
Friday, October 11, 2013 3:12PM - 3:24PM |
C2.00007: Development of self-regulating thermosensitive magnetic nanoparticles Anna Kuklina, Chamath Dannangoda, Karen Martirosyan In oncology, the term ``magnetically induced hyperthermia'' refers to the type of cancer treatment in which the heat is generated by the response of administered ferrofluid to alternating magnetic field. Malignant tumors are more susceptible to the damaging effects of heat within the rage of 40-44 $^{\circ}$C that healthy tissue. However, major limitation associated with hyperthermia cancer treatment is the difficulty of temperature control, due to uneven distribution of magnetic particles and variations in tissue heat conductivity that results in localized overheating of healthy tissue. The focus of this project is the development of self-regulating thermosensitive magnetic nanoparticles, which would lose the magnetic moment when temperature reaches the upper limit of biologically tolerable range. The reduction of the Curie temperature of the magnetic fluid can be accomplished by doping superparamagnetic iron oxide nanoparticles with various biocompatible oxides, such as zinc, titanium, and magnesium. Described approach would make hyperthermia treatment minimally invasive and reduce associated side effects. [Preview Abstract] |
Friday, October 11, 2013 3:24PM - 3:36PM |
C2.00008: Automation of alumina nanopore fabrication by anodization Leonardo A. Bello Puentes, Igor V. Roshchin, Pavel Lapa To fabricate arrays of nanopores, we use anodization of aluminum films. This process requires monitoring of current, voltage and temperature. We designed a control system that uses Labview, a data acquisition card (DAQ) with a built-in analog-to-digital converter (ADC), and amplification circuits. One of the challenges is to measure a broad dynamic range of current from 1 mA to 10 A. The resolution of our 12-bit ADC, which is inexpensive and commonly used with Labview, does not allow measuring 4 decades of current directly. We implement an amplifier that automatically switches between three ranges of measured currents. The response of the operational amplifier is not linear in the entire range of input voltages, and we establish the linear region of amplification for this operational amplifier chip, with the intention of resolving 1 mA current at the smallest range. Using this linear range, we establish the limits for the three ranges of the measured current and configure the auto-ranging that is controlled by a finite state machine (FSM) implemented in Labview. Since the thickness of the anodized material is proportional to the total charge passed through the sample, the system can stop the anodization process for a preset thickness of the material. [Preview Abstract] |
Friday, October 11, 2013 3:36PM - 3:48PM |
C2.00009: Exothermic interaction in the nanostructured system Al$_{2}$O$_{3}$-PTFE at various heating rates Mkhitar Hobosyan, Karen Martirosyan The interaction in the system Auminum oxide-polytetrafluoroethylene (PTFE, Teflon TM) is very important for the energetic systems. In this work we attempt to study PTFE-Al$_{2}$O$_{3}$ system at heating rates up to 200 $^{\circ}$C/min. The thermodynamic analysis by using the thermochemical code HSC-7 confirmed exothermic behavior of reaction. The Differential Scanning Calorimetry (DSC) technique was used to characterize dynamic features of interaction between polytetrafluoroethylene (PTFE) and calcinated Al$_{2}$O$_{3}$ under different heating rates. The result shows that there is a transformation from endothermic to the exothermic mode. At heating rates less than 150 $^{\circ}$C/min the reaction is mainly endothermic, while at heating rates higher than 150 $^{\circ}$C/min we have observed an exothermic reaction behavior. In endothermic mode the activation energy was estimated to be 265 kJ/mol, and at heating rates higher than 150 $^{\circ}$C/min the activation energy was 21 kJ/mol. The activation energy of the reaction was calculated based on the peak temperatures of heat flow curves obtained from DSC measurements, using the isoconversional method. Experimental study shows that at the exothermic mode the PTFE reacts with Al$_{2}$O$_{3}$ in a single step producing AlF$_{3}$ and carbon. The study shows that the PTFE can potentially remove the oxide layer from aluminum and increase the direct contact area between oxygen and aluminum, which increases the reaction rate and improves the energy discharge in nanoenergetic systems. [Preview Abstract] |
Friday, October 11, 2013 3:48PM - 4:00PM |
C2.00010: Three Dimensional Spatial Recognition Mapping of Magnetic Fields Utilizing Commercial Commodity Hardware Francisco Lozano A three dimensional portable tracking system can be developed using the relatively cheap commodity hardware known as the Wiimote. The Wiimote can be used to track position data, and can be coupled with data from other instruments. This research aims to integrate position and magnetic field strength data to build a virtual map of surrounding magnetic fields. [Preview Abstract] |
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