Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session X10: Chemical Physics on the NanoscaleLive
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Sponsoring Units: DCP Chair: Nikolaos Liaros, University of Maryland, College Park |
Friday, March 19, 2021 8:00AM - 8:12AM Live |
X10.00001: Development of Nanosensors for Arsenic Detection in Drinking Water Muhammad Abbas, Irshad Hussain Arsenic (III) poisoning is among the most significant public health concerns worldwide, and arsenic is among the WHO’s top ten most toxic chemicals. Millions of people in more than 50 countries are consuming arsenic polluted water. Long term exposure to arsenic-contaminated water or food may cause cancer (e.g., kidney and lungs) and skin diseases. The WHO and EPA recommended the maximum contaminant limit to 10 μg/L (10ppb) in drinking water. Traditionally, High-tech lab instruments such as ICP-MS, atomic fluorescence spectroscopy (AFS), and atomic absorption spectroscopy (AAS) are used. However, these instruments are highly expensive and cannot be used for on-site detection. Nanomaterials based sensors are cheaper, robust, portable, sensitive, and selective. Gold nanoparticles (AuNPs) based materials are the best candidates for developing sensors due to their optical properties and better conductivity. We report an efficient and user-friendly sensitive and selective AS (III) colorimetric sensor to screen contaminated water samples. AuNPs change the color from red to blue, and this shift is proportional to the amount of arsenic present in the water. The detection limit with the naked eye is 50 μg/L, whereas, with UV/Vis spectroscopy, it is 3 μg/L. |
Friday, March 19, 2021 8:12AM - 8:24AM Live |
X10.00002: Fluorophores “turned-on” by corrosion reactions can be detected at the single-molecule level Anuj Saini Corrosion is an interfacial process that has a profound impact on society. While the mechanism of iron corrosion has been known for centuries, we haven’t been able to visualize corrosion at the molecular scale due to the spatial and temporal limits of current microscopies and the long time scale of corrosion to develop larger microscale features. We demonstrate that fluorogenic molecules that “turn-on” upon redox reactions can sense the corrosion of iron at the single molecule scale. We first observe the cathodic reduction of non-fluorescent resazurin to fluorescent resorufin in the presence of iron in bulk solution. We show that the fluorescence signal is directly related to the amount of electrons that are available due to corrosion progression and can be used to quantify the catalyzed increase in the rate of corrosion by NaCl. By using modern fluorescence microscopy instrumentation we detect real-time, single-molecule “turn-on” of resazurin by corrosion, overcoming the previous limitations of microscopic fluorescence corrosion detection. Analysis of the total number of individual resorufin molecules shows heterogeneities during the progression of corrosion that are not observed in ensemble measurements. |
Friday, March 19, 2021 8:24AM - 8:36AM Not Participating |
X10.00003: Melting and supercooling of gold nanoparticles in an electric field trap in high vacuum prior to deposition on a substrate Joyce Coppock, Quinn Waxter, José Hannan, Samuel Klueter, Luke D Robertson, Bruce E Kane A nanoparticle levitated in an electric field trap in high vacuum has minimal thermal contact with its surroundings. It can be heated efficiently with a laser beam, allowing thermodynamic measurements as well as precise control of its temperature. While the method is generalizable to many nanoscale materials, we use 200 nm gold nanoparticles to establish the technique. We discuss improvements to our method of injecting charged particles into the trap via electrospraying of a liquid nanoparticle suspension. We present measurements of the temperature of a trapped gold nanoparticle across the melting transition and show that it can be supercooled below its melting temperature. We repeat these measurements with 532 nm (green) and 660 nm (red) laser light. To facilitate further examination of trapped particles, we have developed a method of expelling the particle from the trap and depositing it on a removable substrate with high positional accuracy using an electrostatic lens. We discuss plans to improve adhesion by raising the temperature of particles to soften or melt them at the time of deposition. |
Friday, March 19, 2021 8:36AM - 8:48AM Live |
X10.00004: Reshaping of Truncated Pd Nanocubes: Atomistic Modeling and TEM analysis James Evans, King Lai, Minda Chen, Benjamin Williams, Yong Han, Chia-Kuang Tsung, Wenyu Huang Stability against reshaping of metallic fcc nanocrystals synthesized with tailored far-from-equilibrium shapes is key to maintaining optimal properties for applications such as catalysis and plasmonics. We develop a stochastic atomistic model and perform KMC simulations for reshaping mediated by surface diffusion incorporating realistic diffusion kinetics across and between different facets, along step edges and around corners, etc. For the reshaping of fcc metal nanocubes, we also provide an analytic determination of the energy variation along the optimal pathway for reshaping which involves transfer of atoms across the nanocube surface from edges or corners to form new layers on side {100} facets. The effective barrier from this analysis is shown to increase strongly with the degree of truncation of edges and corners in the synthesized nanocube. Theory matches and elucidates experimental TEM results for the reshaping kinetics for Pd nanocubes yielding a high effective barrier of Eeff » 4.6 eV for the appropriate degree of truncation. Reference: ACS Nano 14 (2020) 8551. |
Friday, March 19, 2021 8:48AM - 9:00AM Live |
X10.00005: Elucidating the Band Structure of Vanadium Pentoxide Nanoparticles Via Soft X-Ray Spectroscopy Emma Anquillare, Feipeng Yang, Li Cheng Kao, Xuefei Feng, Virginia Altoe, Vedran Jovic, Yi-Sheng Liu, Linda H Doerrer, Jinghua Guo, Kevin Smith Vanadium pentoxide nanoparticles are recognized for their catalytic properties, including water-splitting photocatalysis, and also serve as promising candidates for multivalent ion battery cathodes. In both instances, nanostructuring has been shown to directly enable or improve efficacy compared to bulk V2O5. However, in spite of their popularity as a research subject, little remains known about the fundamental changes in electronic band structure brought about by V2O5 nanostructuring. Here, ultra-small, monodisperse vanadium pentoxide nanoparticles are first characterized using Transmission Electron Microscopy and X-Ray Diffraction. For the first time to our knowledge, soft x-ray absorption spectroscopy (XAS), x-ray emission spectroscopy (XES), and resonant inelastic x-ray scattering (RIXS) are then used to reveal a holistic, detailed portrait of nanoparticle conduction and valence bands. This data is directly compared to that of the bulk material, and observed changes are discussed. |
Friday, March 19, 2021 9:00AM - 9:12AM Live |
X10.00006: The unexpected imprints of the tug of war between quantum coherence and environmental noises on the efficiency at the maximum power of a molecular photocell. Subhajit Sarkar, Yonatan Dubi The molecular photocell, i.e., a single-molecule donor-acceptor complex placed between two external leads, besides being technologically important, is a paradigmatic example of a many-body system operating in strong nonequilibrium. There exist parameter regimes where an intricate interplay between environmental noise and quantum coherence effectively increases the efficiency of the transport process, a phenomenon, known as, “environment assisted quantum transport,” or ENAQT in short. We discuss, within the set-up of a molecular photocell, that while a single environment can assist quantum transport, the combined effect of more than one type of environment can, quite counterintuitively, hamper the transport efficiency over a broad parameter regime. The efficiency at maximum power provides clear signatures of such surprising behaviors. Our findings are verifiable given recent advances in the experimental ability. |
Friday, March 19, 2021 9:12AM - 9:24AM Live |
X10.00007: Synergistic effect of Bi-doped exfoliated MoS2 nanosheets on their bactericidal and dye degradation potential. USMAN QUMAR In this study, bare and bismuth (Bi)-doped molybdenum disulfide (MoS2) nanosheets were synthesized via a hydrothermal method. Different Bi weight ratios of 2.5, 5, 7.5 and 10% were doped in MoS2 to evaluate its catalytic and antimicrobial activities. Doped nanosheets were |
Friday, March 19, 2021 9:24AM - 9:36AM Live |
X10.00008: Quantum Size Effects in the Magnetic Susceptibility of a Metallic Nanoparticle Marc Roda-Llordes, Carlos Gonzalez-Ballestero, Adrián Ezequiel Rubio López, María José Martínez-Pérez, Fernando Luis, Oriol Romero-Isart We theoretically study quantum size effects in the magnetic response of a spherical metallicnanoparticle (e.g. gold). Using the Jellium model in spherical coordinates, we compute the inducedmagnetic moment and the magnetic susceptibility for a nanoparticle in the presence of a static external magnetic field. Below a critical magnetic field the magnetic response is diamagnetic, whereasabove such field the magnetization is characterized by sharp, step-like increases of several tenths ofBohr magnetons, associated with the Zeeman crossing of energy levels above and below the Fermi sea. We quantify the robustness of these regimes against thermal excitations and finite linewidth ofthe electronic levels. Finally, we propose two methods for experimental detection of the quantumsize effects based on superconducting quantum interference devices. |
Friday, March 19, 2021 9:36AM - 9:48AM Live |
X10.00009: Excited State Imaging and STM Characterization of Materials on the Nanoscale Alison Wallum, Huy Nguyen, Zetai Liu, Sikai Wu, Martin Gruebele, Joseph W Lyding In an effort to spatially resolve excited state properties of nanomaterials with sub-nm resolution, our group has developed an excited state imaging technique known as single-molecule absorption scanning tunneling microscopy (SMA-STM). This technique allows us to probe changes in tunneling associated with laser excitation, creating an image that maps the excited state electronic structure of nanomaterials. We have applied this technique widely to study excited state properties of nanomaterials including quantum dots (QDs) and carbon nanotubes (CNTs), and will discuss results surrounding the interactions of optically excited QDs and CNTs. This work will focus on semi-quantitative modeling of our experiments showing the distant-dependent transverse polarization of CNTs in the presence of an excited QD and modeling energy transfer between materials. We will also discuss preliminary work with traditional STM on carbon nanothreads and their variants, which aims to characterize the ground state electronic properties of these carbon materials. Initial results show highly variable band gaps of aggregate structures likely due to varied ordering and defects, while techniques allowing for investigation of individual threads will ultimately position us for excited state characterization. |
Friday, March 19, 2021 9:48AM - 10:00AM Live |
X10.00010: Complex Imaging Reflectometry Using Tabletop Coherent EUV Beams for Spatially and Depth-Resolved Imaging Yuka Esashi, Michael Tanksalvala, Christina L. Porter, Bin Wang, Nicholas W Jenkins, Zhe Zhang, Joshua L Knobloch, Brendan McBennett, Naoto Horiguchi, Chen-Ting Liao, Jianwei Miao, Michael Gerrity, Henry C Kapteyn, Margaret Murnane Next-generation nano and quantum devices have intricately designed complex structures. Moreover, there is a need to integrate advanced 2D and spintronic materials, with control over the electronic, magnetic, transport and interfacial properties. For optimizing these systems, new characterization techniques with high spatial resolution and sensitivity are needed. We present a tabletop complex imaging reflectometer illuminated by coherent high harmonic extreme ultraviolet (EUV) light. It uses coherent diffractive imaging algorithms to generate phase and amplitude reflectivity maps of a sample at many incidence angles. Both the phase and reflectance of EUV wavelengths are very sensitive to the structure and material of the sample, yielding ~50 nm transverse resolution and ~Å axial precision. From the angle-dependent reflectivity, we can solve for the 3D composition in a spatially-resolved and non-destructive manner. Using a semiconductor sample, we solve for layer thicknesses, structure heights, interface quality and dopant levels, which were verified using correlative metrology. |
Friday, March 19, 2021 10:00AM - 10:12AM Live |
X10.00011: A Kinetic Pathway toward Narrowest Zigzag Graphene Nanoribbons Grown on Cu(111) Yifei Yang, Limei Wang, Zhenyu Zhang, Ping Cui Narrowest zigzag graphene nanoribbons (nZGNRs) have advantages over extended graphene in both electronic and magnetic properties. However, the fabrication of nZGNRs via bottom-up approach remains a standing challenge. Here, based on first-principles calculations we propose to grow nZGNRs via self-assembly of 1,4-Dibromo-2,5-Bis(bromomethyl)benzene precursors on Cu(111). We first show that the precursor can be easily adsorbed on Cu(111), accompanied by simultaneous debromination in the bromomethyl groups with energy barriers of ~0.1 eV. The remaining Br atoms are more easily detached than the H atoms of the precursors, with energy barriers of 0.5~0.7 eV, leading to C8H6 radicals that are suitable for formation of nZGNRs. Two such radicals can couple to form a nZGNR-like radical dimer with the unsaturated C atoms located on the positions similar to the C8H6 radicals at ~573 K, enabling the coalescence of the subsequent C8H6 radicals. Furthermore, we show that the nZGNR-like radical dimer is energetically more favorable than most by-product dimers, ensuring a relatively high reaction yield. These findings provide a new route toward fabrication of nZGNRs for various realistic applications in electronics and spintronics. |
Friday, March 19, 2021 10:12AM - 10:24AM Live |
X10.00012: Time resolved charge transport properties of single-molecule junctions Yuji Isshiki, Tomoaki Nishino, Fujii Shintaro Charge transport properties through molecules have been studies on the single molecule scale using the break junction (BJ) technique. Here, we investigate time resolved single-molecule transport properties, which has been masked by time averaged electric measurement. Target molecules are benzene-type molecules with different anchor group of thiol, amine, and isocyanide. Single-molecule junctions of each target molecule sandwiched by Au electrodes are created by the BJ technique. We developed current vs bias voltage (I−V) measurement technique to obtain time resolved change in the metal-molecule electronic interactions (Γ) and the molecular energy level relative to the Fermi level of the electrodes (ε). Time resolved I−V curves were measured during the self-breaking process of the single-molecule junctions at room temperature. We found both ε and Γ decreased for all molecules in a 1 ms time window just before the self-breaking event. The decay factor tA (Here, A(t) = A0 exp(−t/tA) and A = ε or Γ) were tε > tΓ for thiol, tε = tΓ for amine, and tε < tΓ for isocyanide. This study provides insight into time resolved change in the transport properties and the electronic structure (i.e., e and G) on the single-molecule scale. |
Friday, March 19, 2021 10:24AM - 10:36AM Live |
X10.00013: DFT3: An Efficient DFT Solver for Nanoscale Simulations and Beyond. Xuecheng Shao, Wenhui Mi, Michele Pavanello To date, there are two kinds of DFT algorithms: Kohn-Sham DFT (KS-DFT) and orbital-free DFT (OF-DFT). KS-DFT is most common, uses a prescription whereby the lowest N eigenvalues (where N is the number of electrons) of a one-particle Hamiltonian need to be computed. OF-DFT prescribes to compute just one state recovering the effect of the other states with pure density functionals. In this work, we propose a new DFT solver (DFT3). From KS-DFT we borrow the self-consistent field iteration, so that computationally expensive density functionals are evaluated seldom. From OF-DFT we borrow the reliance on kinetic energy functionals, thus removing the need to diagonalize bringing strong computational savings. DFT3 leverages recent advances in OF-DFT development to output a computationally cheap and accurate ab initio electronic structure method. The key aspect of DFT3 is it's still made use of an eigenvalue-like problem targeting just one solution while retaining the ability to sample ensemble N-representable electron densities. We implemented this method in DFTpy software. In comparison to OF-DFT and KS-DFT, DFT3 cuts the timing down by orders of magnitude and maintains linear scalability with system size. |
Friday, March 19, 2021 10:36AM - 10:48AM On Demand |
X10.00014: The Origin of Photoluminescence Center in 0D Cs4PbBr6 Perovskite Zhaojun Qin, SHENYU DAI, Viktor G. Hadjiev, Chong Wang, Lixin Xie, Yizhou Ni, Chunzheng Wu, Guang Yang, Shuo Chen, Liangzi Deng, Qingkai Yu, Guoying Feng, Zhiming M. Wang, Jiming Bao 0D perovskite Cs4PbBr6 has attracted considerable attention recently because of highly efficient green photoluminescence (PL) and highly debated opposing opinions on its photoluminescence origin: embedded CsPbBr3 nanocrystals versus intrinsic Br vacancy states. In this work, we provide sensitive but noninvasive methods to directly demonstrate that CsPbBr3 nanocrystals inclusions in Cs4PbBr6 are the dominant green PL source. We first use correlated Raman-PL method to identify the difference between emissive and non-emissive Cs4PbBr6 crystals and reveal the existence of CsPbBr3 nanocrystals in emissive Cs4PbBr6. We then measure the response of luminescence centers to hydrostatic pressure. The observations of red-shifting, diminishing, and eventual disappearance of both green emission and Raman under pressure exclude Br vacancies as possible luminescent centers. The resolution of this long-lasting controversy paves the way for further device applications of low dimensional perovskites, and our techniques are applied to other emerging materials. |
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