Bulletin of the American Physical Society
APS March Meeting 2020
Volume 65, Number 1
Monday–Friday, March 2–6, 2020; Denver, Colorado
Session X52: Nanomaterial Interactions and Applications |
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Sponsoring Units: DMP Chair: Daniel Dougherty, North Carolina State University Room: Mile High Ballroom 1E |
Friday, March 6, 2020 11:15AM - 11:27AM |
X52.00001: Spin Relaxation Times of Copper Phthalocyanine (CuPc) Qubits diluted in Diamagnetic Zinc Phthalocyanine (ZnPc) Host Matrices Chandler Merrill, Henna Popli, Hans Malissa, Ryan Stolley, Joel Miller, Valy Vardeny, Christoph M Boehme We report on electron paramagnetic resonance (EPR) measurements of powder CuPc prepared in a solid-state complex, ZnPc. The free electron spin of CuPc constitutes a two-state quantum system that may potentially be a candidate as a quantum bit (qubit) for quantum computing applications [1]. We test whether the CuPc electron spin increases its spin dephasing time, T2, when the exchange interactions between adjacent CuPc qubits is reduced by diluting CuPc molecules in a zinc phthalocyanine (ZnPc) host matrix [2] at concentrations of 0%, 1%, 5%, and 10%, which modifies the average distance between CuPc molecules. ZnPc is a diamagnetic molecule that nominally does not exhibit an EPR signal and, also, the dominant Zn isotopes are I=0. We study the system using continuous wave and pulsed EPR, and we find similar results to previous studies on CuPc in liquid host matrices, T2 on the order of 1 µs observed for both, CuPc as well as another yet unidentified paramagnetic center that is likely due to an admixture to the ZnPc matrix. We also study the temperature dependence of the EPR signals between 5 K and room temperature. [1] M.Warner et. al, Nature, 503, 504(2013). [2] S.Seelan, et. al, Journal of Molecular Catalysis A: Chemical, 168, 61(2001). |
Friday, March 6, 2020 11:27AM - 11:39AM |
X52.00002: First Principles Studies of the Structural Evolution of a Dicyanobenzene Molecular Junction with Gold Electrodes Mo Li, Joshua Young, Manuel Smeu Molecular electronics have attracted attention due to their potential in decreasing the size of transistors to the molecular scale. We present our first principles studies of the structural and electronic properties of a single-molecule dicyanobenzene junction with gold electrodes. Density functional theory (DFT) was used to simulate the formation process of the dicyanobenzene molecular junction by elongating a gold nanowire with a dicyanobenzene molecule placed above a thin gold wire. As the wire was stretched and broken, we found four significant stages of system rearrangement. The molecule first rotated (the first stage) and then gradually slipped into the junction and bonded to the gold atomic tips in three stages. For each stage, we performed calculations using the non-equilibrium Green’s function combined with the DFT (NEGF-DFT) method to obtain the electronic transport pathway and the conductance of the molecular junction. We found that after the main transmission channel switches from via the gold bridge to via the molecule, the conductance increases while the junction is elongated, which is due to an interesting alignment between the frontier molecular levels and the Fermi energy of the electrodes. |
Friday, March 6, 2020 11:39AM - 11:51AM |
X52.00003: Scanning tunneling microscopy study of atomistic energy level engineering in donor-acceptor molecules Giang Duc Nguyen, Gary Tom, Christopher M Tonge, Zachary M Hudson, Sarah A Burke Donor-acceptor materials show highly tunable electronic properties via exchange of the donor and acceptor units, making them appealing for light-harvesting and light-emitting applications. While ab-initio calculations can be used for guidance in molecular design of these complexes, there has been little microscopic characterization of the donor-acceptor electronic interaction at the molecular level. Here we present atomistic energy level engineering in N-heterotriangulence derivatives functionalized with different acceptor units. Individual isolated molecules deposited on Ag(111) substrate were studied with scanning tunneling microscopy (STM). The bond-resolved STM (BRSTM) technique was performed to confirm the molecular structure. We performed STM spectroscopy to obtain the molecular energy levels with the spatial distribution mapping of molecular orbitals respectively. Our STM results are corroborated by density function calculations and macroscopic optical absorption/emission measurements. |
Friday, March 6, 2020 11:51AM - 12:03PM |
X52.00004: Temperature and Pressure Dependent Properties of A3Ti2O7 Sizhan Liu, Eli Stavitski, Zhenxian Liu, SuYin Wang, Yu-Sheng Chen, Bin Gao, Jaewook Kim, Sang-Wook Cheong, Sanjit Ghose, Trevor Tyson Theoretical models of the A3Ti2O7 system suggest that electric polarization is due to the combination of the coherent TiO6 octahedral rotation and tilting, both being nonpolar. For the doped A3Ti2O3 systems, different size atoms enable the possibility of site-selective substitution in A’ or A site to tune the TiO6 octahedral rotation and tilting. In this work, a structural study over a broad range of temperatures and pressures has been conducted by x-ray diffraction, Raman spectroscopy, x-ray absorption spectroscopy, x-ray pair distribution function measurements and DFT modeling. The long-range and local symmetries and local atomic and electronic structural changes will be discussed and compared with previous work. |
Friday, March 6, 2020 12:03PM - 12:15PM |
X52.00005: Characterizing Cellulose Crystallographic Texture in Plant Cell Walls Using Grazing Incidence X-ray Scattering Sintu Rongpipi, Dan Ye, William John Barnes, Sarah Kiemle, Arthur Woll, Chenhui Zhu, Charles Anderson, Daniel Cosgrove, Esther Winter Gomez, Enrique D Gomez Cellulose, the most abundant biopolymer on earth, is a versatile material with tuneable properties. It exists as semi - crystalline microfibrils in plant cell walls. This crystalline structure is important for plant growth and determines properties of cellulosic materials. However, several aspects of this crystalline structure remain elusive - one of them being orientation of cellulose crystallites. We studied the structure of cellulose in plant primary cell walls through grazing incidence wide angle X-ray scattering (GIWAXS). GIWAXS of cell wall reveal strong texturing of cellulose. The degree of texturing is determined through pole figures constructed from combination of GIWAXS and XRD rocking scans. We find that cellulose texturing depends on developmental age of tissue. GIWAXS of cell wall mutants reveals interactions between wall polysaccharides. We find that cellulose texture is disrupted in pectin and cellulose mutants but not in xyloglucan mutants. These findings provide insights on cellulose crystalline structure which can help design cellulose-like materials and efficient biomass conversion process. |
Friday, March 6, 2020 12:15PM - 12:27PM |
X52.00006: Redesign and Develop Effective Liposomal Formulation for Prodrug Delivery Through Synchrotron X-ray Studies of Molecular Interactions Tiep Pham, Paola Leon-Plata, Pin Zhang, Chang Liu, Wei Bu, Binhua Lin, Ying Liu Liposomal formulations may provide advantages for drug delivery to overcome high dose and toxicity issues of anticancer chemotherapy prodrugs such as capecitabine. However, because of the enormous combination and the unique molecular structure of the prodrug, it is difficult to prepare liposomal-capcitabine fomulations with high drug loading and long-term stability based on empirical trials. |
Friday, March 6, 2020 12:27PM - 12:39PM |
X52.00007: Long-Term Performance Prediction of Mixed Matrix Membranes at Different Adsorbent Dose and Operating Conditions Raka Mondal Mixed matrix membranes (MMMs) with nanoparticles showing adsorption property of small sized solute can find wide application in large-scale water purification. The breakthrough behavior of the membrane dictates its life indicating need for regeneration or eventual replacement. A two-dimensional transient model was developed using equations of continuity, motion and convective-diffusive-adsorption based solute transport. The governing partial differential equations has been solved using finite element method by COMSOL v5.3® software package. The model was verified for adsorptive removal of chromium(VI) from synthetic solution using graphene oxide incorporated MMM hollow fibers. The model parameters were evaluated using experimental data of long-term filtration the solution with respect to throughput and rejection characteristics. The validated model was extended for simulation of large-scale filter interrelating feed concentration, adsorbent dose, trans-membrane pressure drop and cross flow rates. From the simulation, at a fixed operating condition, a performance curve was generated linking and breakthrough volume of the MMMs. It can be extended for design of any large-scale hollow fiber MMM based filtration system. |
Friday, March 6, 2020 12:39PM - 12:51PM |
X52.00008: Time-dependent mechanical response of ice adhesion on metal substrates Marina Machado de Oliveira, Joseph R Murphy, WIlliam Rice, John Ackerman, Vladimir Alvarado Ice adhesion on aerospace-relevant materials is both complex and poorly understood. Measuring and understanding the underlying physics requires reliable testing techniques that can yield multifaceted datasets. The latter includes surface morphology (i.e., roughness and its spatial correlation structure), resolving substrate-induced strain, and direct mechanical testing of adhesion. Our initial creep test data using a stress-controlled rheometer showed an apparent adhesion dependence on both surface roughness and temperature: namely, that the adhesion strength is higher for rougher surfaces and seems to increase with temperature. To shed light on these initial findings, we performed time-dependent stress ramps from -20 to -7oC to determine the dynamical stress relaxation mechanism. Additionally, we investigated the spatial correlation surface roughness maps for aluminum specimens. Stress-ramp results confirmed a connection between surface roughness and apparent adhesion. Moreover, the creep-test behavior appears to represent an upper bound of the time-dependent adhesive behavior of ice. These results take us a step forward to understanding ice adhesion mechanisms. |
Friday, March 6, 2020 12:51PM - 1:03PM |
X52.00009: Electrical Measurement of Water Assisted Ion Desorption and Solvation on Isolated Carbon Nanotubes Patrick Edwards, Bo Wang, Steve Cronin, Adam W. Bushmaker With continued reduction in the feature size of device structures we are quickly approaching the one-dimensional limit of electrical conduction. In this regime it becomes increasingly important to study the effects of individual dopants and defects on device performance. Recent studies on the electrical properties of suspended carbon nanotube field-effect transistors (CNT-FETs) have revealed extreme sensitivity in device conductivity in the presence of individual gaseous ions adsorbed at the nanotube surface. We will present an investigation on the mean residence time of gaseous ions adsorbed on the surface CNT-FETs with and without native surface water layers that exist in atmospheric conditions. Devices dehydrated by various methods were all found to have substantially higher mean ion residence times. We propose that native water molecules in ambient conditions provide a reduction pathway for incoming gaseous ions, yielding Hydronium ions (H3O+). We characterize the interaction between these ions with the CNT-FET surface via large switching events in device conduction and compare to measurements taken on desiccated devices. |
Friday, March 6, 2020 1:03PM - 1:15PM |
X52.00010: Enhancing Superionic Conductivity in Cluster-Based Sodium-Rich Antiperovskites Hong Fang, Purusottam Jena Sodium (Na) superionic conductors are the key to developing next-generation solid-state batteries with safety and low cost. However, most of the known Na-conductors exhibit limited ionic conductivities at room temperature (RT), hindering their practical applications. To meet the challenge, a series of Li- and Na-rich antiperovskite superionic conductors based on cluster ions (e.g. BH4- and BCl4-) have been theoretically developed [e.g. Fang et al. PNAS 114, 11046, 2017; ACS App. Mat. Inter. 11, 963, 2018]. These materials exhibit superior properties as solid electrolytes with greatly enhanced ionic conductivities at RT. One cluster-based solid electrolyte of such, Na3O(BH)4, has been successfully synthesized for the first time most recently and its measured RT ionic conductivity is well above 10-3 S/cm which is four orders of magnitude higher than that of its halogen counterparts Na3OX (X = Cl, Br, I) [Sun et al. J. Am. Chem. Soc. 141, 5640, 2019]. In this work, we aim to further enhance the ionic conductivity of the Na-superionic conductor by using chemical mixing according to the size effect. The study further shows the advantage of utilizing cluster ions as building blocks, introducing additional degrees of freedom into tuning the properties of superionic conductors. |
Friday, March 6, 2020 1:15PM - 1:27PM |
X52.00011: Absorption spectra and density of states of cubic Frenkel exciton system with Gaussian diagonal disorder Abdelkrim Boukahil, Nouredine Zettili We used the coherent potential approximation to investigate the density of states and the optical absorption of Frenkel exciton systems in cubic lattices with nearest neighbor interactions and a Gaussian diagonal disorder. Our results for the simple cubic are in good agreement with previous investigations using finite-array calculations. |
Friday, March 6, 2020 1:27PM - 1:39PM |
X52.00012: Flexible bimodal photoemission electron source based on Au-coated fiber optic nanotips Sam Keramati, Ali Passian, Vineet Khullar, Joshua Beck, Cornelis Uiterwaal, Herman Batelaan Ultrashort laser-driven coherent electron sources based on nanotip needles have been studied motivated by their desired properties for ultrafast electron diffraction and microscopy, electron point projection microscopy, etc. While the conventional schemes require focusing the fs laser beam on or near the apex of a nanotip, which is prone to misalignment and unwanted scattering, we demonstrate and characterize a nanotip electron source based on tapered optical fibers coated with Au on one end. Our theoretical analysis followed by detailed experiments at a range of visible wavelengths confirm that the observed nonlinear electron emission is assisted by surface plasmon excitation in the metallized fiber taper. Fiber tips leverage over the conventional tips in two major ways: 1) They are alignment-free by end-fire coupling, 2) They emit not only using ultrashort pulsed lasers but also by low-power CW diode lasers in the long wavelength regime. The fiber tips are useful where back-illumination or raster scanning an electron source is needed as in electron nanolithography using a single fiber or a bundle for parallel processing. |
Friday, March 6, 2020 1:39PM - 1:51PM |
X52.00013: INVESTIGATION OF MULTICOLORED AND WHITE LIGHT EMISSION FROM IR-EXCITED NANO-PARTICLES Lidong Ma, Baldassare Di Bartolo The search for multicolored light produced by some IR laser-excited luminescent nano-powders has revealed, for laser power exceeding a threshold value, the emission of white light (WL) with black-body characteristics. We are directing our research to the study of the physical parameters that may influence the threshold power of the laser and the efficiency of the WL emission. |
Friday, March 6, 2020 1:51PM - 2:03PM |
X52.00014: On-and-off chip magnetic cooling for semiconductor nanostructures below 1 mK Dominik Zumbuhl, Mohammad Samani Magnetic cooling has the potential to make the regime beyond dilution refrigerators and below 1 mK accessible to experiments, to investigate interesting novel physics such as exotic quantum phases, new (topological) quasi particles and unprecedented quantum coherence, e.g. in quantum transport. In Basel, the strategy is to cool each of the sample wires with its own, separate demagnetization refrigerator and to simultaneously provide on-chip cooling. This approach reduces external heat leaks (off-chip cooling) and provides local cooling (on-chip) where it’s most effective. |
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X52.00015: A realistic dimension-independent approach for charged defect calculations in semiconductors Hui-Xiong Deng, Jun-Wei Luo, Suhuai Wei First-principles calculations of charged defects have become a cornerstone of research in semiconductors and insulators by providing insights into their fundamental physical properties. But current standard approach using the so-called “jellium model” has encountered computational difficulty for low-dimensional semiconducting materials. In this presentation, we propose a physical, straightforward, and dimension-independent universal model to calculate the formation energies of charged defects in both three-dimensional (3D) bulk and low-dimensional semiconductors. This realistic model reproduces the same accuracy as the traditional jellium model for most of the 3D semiconducting materials, and remarkably, for the low-dimensional structures, it is able to cure the divergence caused by the artificial long-range electrostatic energy introduced in the jellium model, and hence gives meaningful formation energies of defects in charged state and transition energy levels of the corresponding defects. Our realistic method, therefore, will have significant impact for the study of defect physics in all low-dimensional systems including quantum dots, nanowires, surfaces, interfaces, and 2D materials. |
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