Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session B32: Adsorption and Physisorption |
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Sponsoring Units: DCMP Chair: Harry Smith, University College London Room: Room 224 |
Monday, March 6, 2023 11:30AM - 11:42AM |
B32.00001: Identifying electronic states of Covalent Organic Frameworks using STM Harshavardhan Murali, Zachery Enderson, Raghunath Dasari, Timothy C Parker, Seth Marder, Hong Li, Qingqing Dai, Jean-Luc E Bredas, Phillip N First Two dimensional heterotriangulene-based Covalent Organic Frameworks (COFs) have been predicted to be semiconducting materials with both flat bands and Dirac-type bands [1]. We have synthesized nanometer-scale networks based on the dimethylmethylene-bridged triphenylamine (DTPA) units [2] on gold and silver surfaces using on-surface synthesis, and study them using Scanning Tunneling Microscopy and Spectroscopy (STM/STS). We attempt to match the features identified in the finite-sized network with the band structure obtained from first-principles calculations on the periodic lattice. For filled states, we find that the molecular bands appear similar to calculations of the freestanding COF electronic structure. For unfilled states, however, surface state electrons in the underlying metal contribute significantly to the STS spectra and spectral maps. We analyze the experimental data using a clustering algorithm to separate the contributions of molecular states and substrate states. Using tight-binding for molecular states and plane-waves for substrate states, we also explore how well the overlayer/substrate interaction, and boundary effects, can be modeled for finite-sized COF islands. |
Monday, March 6, 2023 11:42AM - 11:54AM |
B32.00002: Adsorption of organophosphate nerve agent VX on the (101) surface of anatase titanium dioxide Gloria Bazargan, Igor V Schweigert, Daniel Gunlycke We quantify the adsorption of the organophosphate venomous agent X (VX) on the clean and hydroxylated (101) surfaces of anatase titanium dioxide (TiO2) with density functional theory (DFT) calculations. Our results show that adsorption on the clean anatase (101) surface occurs through the VX phosphoryl oxygen (O=P) site and involves the formation of a Ti···O=P dative bond. Steric effects inhibit adsorption through the VX nitrogen and sulfur sites by the formation of Ti···N and Ti···S dative bonds. On the hydroxylated (101) surface, adsorption similarly proceeds through the VX phosphoryl oxygen site but entails the formation of surface–adsorbate hydrogen bonds. Additionally, weak non-covalent interactions between the surface hydroxyl groups and the adsorbate’s nitrogen and sulfur atoms stabilize VX/(101) complexes formed by adsorption through these secondary sites. |
Monday, March 6, 2023 11:54AM - 12:06PM |
B32.00003: Spiropyran and merocyanine adsorption on an ionic insulator surface Andreas Riemann, Lauren Rankin, Dylan Henry Spiropyran (SP) is a photochromic, three-dimensional molecular switch which can be converted to Merocyanine (MC), a planar isomer of Spiropyran where the central C-O bond has been broken. The adsorption behavior of various SP/MC species adsorbed on a NaCl substrate has been investigated using a combination of density functional theory and molecular mechanics calculations. The calculations show a nearly flat adsorption geometry of merocyanine trans-conformers with higher adsorption energies than their respective cis-conformers or the spiropyran isomer itself. In a next step to study the onset of film growth of these SP/MC molecules, two identical isomers were placed in high symmetry orientations with respect to each other governed by the underlying substrate and its symmetry. In these cases, dimers can form in parallel and anti-parallel orientation to each other with slightly different inter-molecular binding energies. Similar onset of film growth by means of dimer formation has been experimentally observed in merocyanine molecules adsorbed on a noble metal substrate. |
Monday, March 6, 2023 12:06PM - 12:18PM |
B32.00004: Spectroscopic study of screening of interactions by a single layer graphene Babu R Gaire, Saranshu Singla, Ali Dhinojwala Graphene supported on a substrate is used for electronic applications and it remains unknown whether the underlying substrate influences the performance of graphene. The conclusions based on the contact angle measurements remain inconclusive. In this study, we report the direct measurements of interfacial interactions by monitoring the shift of the sapphire OH vibrational peaks using interface sensitive sum frequency generation spectroscopy (SFG) in contact with liquids of different polarity. We compare this shift of the sapphire OH peak in contact with liquids of different polarity with and without the single-layer graphene in between. For polar liquids with strong hydrogen bonding interactions, we observe a lower shift for graphene-coated sapphire compared to those liquids in direct contact with a sapphire substrate, indicating screening of polar interactions by single-layer graphene. We also finds that liquids with aromatic groups show surprisingly low screening. We will discuss the differential screening ability of graphene layer for various polar and non-polar liquids. Our experimental results can aid in designing more efficient graphene-based technology. |
Monday, March 6, 2023 12:18PM - 12:30PM |
B32.00005: Morphology Evolution and Crystal Alignment of Copper Phthalocyanine Thin Film under Thermal Annealing Ryan T Mizukami, Thomas Gredig The surface film morphology and nanostructure of small molecule-based thin films play a great role in gas sensor and photovoltaic applications. The morphology evolution of copper phthalocyanine (CuPc) thin films is studied with atomic force microscopy after thermal annealing in vacuum. The concurrently deposited samples are individually annealed in vacuum at temperatures up to 300°C for 30 minutes. The small round CuPc crystals measure around 20nm in diameter as deposited. At the 150°C annealing temperature, they become noticeably elongated, but are randomly oriented. At even higher annealing temperatures, 250°C, the crystals elongate more and start to form domains of similarly aligned crystals. This work demonstrates how the post-annealing procedure can affect the structural properties of small molecular thin films. |
Monday, March 6, 2023 12:30PM - 12:42PM |
B32.00006: How Aqueous Salt Solutions Affect Hydrophobic Surfaces Adele N Poynor The study of how salty water meets a hydrophobic surface is important because in nature water is rarely pure. In order to study this phenomenon, we need smooth and homogenous surfaces; however, salt solutions can damage our surfaces. We study this damage for a variety of self-assembled monolayers (SAMs) in different aqueous salt solutions, using contact angle measurements, scanning electron microscopy, surface plasmon resonance. |
Monday, March 6, 2023 12:42PM - 12:54PM |
B32.00007: Water Confined in Boron Nitride Nanotubes: Role of Entropic Effects Bhargav Sai Chava, Ghansham Rajendrasingh Chandel, Siddhartha Das The thermodynamic factors dictating the stability of water confined in sub-nanometer and nanometer-wide channels are of great interest in nanofluidics. This study reports an entropy-dominated filling of mildly hydrophilic boron nitride nanotubes (BNNTs) with diameters ranging from 0.85 to 1.69 nm. The factors governing such entropic favorability depend on the BNNT-diameter-dictated water structure. Due to a pronounced dangling water-OH bond fraction, the rotational entropic component is dominant in the 0.85 nm diameter BNNT. Further, the water rotational entropy steadily decreases with an increase in the tube diameter, following the same trend as the fraction of dangling water-OH bonds. The translational entropic component is most dominant in the 1 nm wide BNNT due to the enhanced in-plane motion of water molecules that form a single-file structure spanning a significant radial expanse. In BNNTs with a diameter larger than 1 nm, while the translational entropy decreases with an increase in tube diameter, it remains the dominant component in stabilizing water inside these BNNTs. Such a favorable translational entropy for water in larger BNNTs can be attributed to the presence of high specific water volume and a lower number of hydrogen bonds per molecule as compared to bulk water. |
Monday, March 6, 2023 12:54PM - 1:06PM |
B32.00008: Chain dynamics in adsorbed polymer layers featuring strongly- and weakly-interacting polymer-substrate pairings Katelyn Randazzo, Daniele Cangialosi, Biao Zuo, Rodney Priestley Though once conceptualized as "dead," adsorbed nanolayers of polymer atop a substrate are now recognized as capable of undergoing a glass transition, suggesting active local chain dynamics within this nanoscale region. While there exist a range of approaches for studying polymer dynamics, conventional characterization techniques such as calorimetry and ellipsometry are unsuitable for accessing high resolution information about the mobility within nanolayers adsorbed on a typical 2D substrate. Here, we leverage a combined characterization approach to report the respective dynamics of polystyrene and poly(methyl methacrylate) adsorbed on a silica surface. We investigate adsorption at the matrix-nanoparticle interface within a bulk nanocomposite system as a platform of study which, when combined with selective labeling, enables targeted local measurements of adsorbed layer properties via broadband dielectric spectroscopy, fluorescence spectroscopy, and transmission electron microscopy. Taken together, our findings contribute to a refined understanding of how chain dynamics are governed by underlying polymer-substrate interactions in adsorbed layers, affording new avenues towards intentional design of desirable material properties. |
Monday, March 6, 2023 1:06PM - 1:18PM |
B32.00009: Strain Driven Work Function Reduction in the XI/W (X = Li, Na, K, Rb, and Cs) Systems Leopoldo Diaz, Robert C Albers, Avadh B Saxena, Mahdi Sanati A first-principles approach was used to study the interaction between an alkali metal iodide XI (X = Li, Na, K, Rb, and Cs) overlayer and the (100), (110), and (111) surfaces of W. It was shown that the XI adsobate forms tilted dipoles on the W surface and significantly reduces the work function. These findings contradict experimentally proposed models that suggest that the surface electrostatic energy of the dipoles causes the dipoles to be normal to the W surface. A novel model, based on the internal strain caused by the alkali metal's different atomic sizes, is introduced that can explain the dipole moment orientation, strength, and work function changes for all XI/W systems. Furthermore, by calculating the elastic formation energy of the XI adsorbates, the new model is used to explain the formation energy trends for all systems. |
Monday, March 6, 2023 1:18PM - 1:30PM |
B32.00010: Stabilize Cassie state and promote frequent jumping of condensed droplets for high-performance anti-frosting Siyan Yang, Xuehu Ma, Zuankai Wang Frost accretion, characterized by sequential vapor-liquid-solid phase changes, is undesirable in diverse industrial fields by virtue of heat transfer deterioration, machinery breakdown or even disasters. Such phenomenon lies in the complex and dynamic interactions between vapor/liquid and surfaces, in which tailoring the condensation dynamics, especially using superhydrophobic surfaces, holds great promise to dictate the spatially hysteretic frosting dynamics. However, previous studies have overlooked that to what extent the fusion of wetting state and jumping frequency of condensed droplets on superhydrophobic surfaces is favorable for anti-frosting. Herein, we propose a design of nanowire-cluster (NC) superhydrophobic surface that provides stabilized Cassie state and frequent self-jumping during the droplet lifecycle, enabling highly prolonged frost occurrence as well as frost propagation. With merits in desirable condensation dynamics, a NC surface with microgroove vertex angle of 30°and solid-liquid fraction of 31% presents enlarged droplet spacing and reduced mean droplet size, which are jointly responsible for hindering in inter-droplet ice bridge and droplet freezing. As a result, it delays the growth of frost by about a factor of 8 and 3 compared to its counterpart with either Cassie state or droplet jumping ability alone. In particular, the overall frost-free and frost-propagation duration can reach remarkable 200 min at a surface temperature of -8 ? and RH of 50%. |
Monday, March 6, 2023 1:30PM - 1:42PM |
B32.00011: Polarization-induced dipole moments of physisorbed H2 Anders Hellman Physisorption on metal surfaces provides unique experimental opportunities to establish detailed information about the interaction potential, the induced dipole, and their dependence on the normal distance, z, between the inert adsorbate and the solid surface. These observables involve challenging issues for electron structure theory at distances where electron- |
Monday, March 6, 2023 1:42PM - 1:54PM |
B32.00012: Computational study of the molecular ordering of vanadyl phthalocyanine monolayers on surfaces Corina Urdaniz, William H Koll, Kyungju Noh, Luciano Colazzo, Fabio Donati, Christoph Wolf, Andreas Heinrich, Yujeong Bae, Jay A Gupta, Christoph Wolf The versatility of on-surface chemistry allows for designing a wide variety of molecule-based |
Monday, March 6, 2023 1:54PM - 2:06PM Author not Attending |
B32.00013: Freezing of a spreading droplet: A theoretical and experimental study Ganesh Prabhu Komaragiri, Abrar Ahmed, Prashant R Waghmare Here, we study the simultaneous spreading and freezing of sessile droplets. The droplets are generated by a jetting or a liquid needle system. The drop is deposited on a subcooled surface, triggering the droplet's solidification. Only a few studies have elucidated such a complex mechanism where the dynamics of droplet freezing is studied while the mass and volume of the sessile drop are increasing. The theoretical model presented here is inspired by the well-established overall energy balance approach. We modified the initial boundary condition considering the jetting paraments and coupled it with the heat transfer from the impinging cold substrate. Further non-dimensionalization of the governing equations suggests the Bond, Reynolds, and Weber numbers are decisive factors to comment on the outcome. This model predicts the temporal evolution of the droplet growth and solidification rate while the drop is spreading. We validated our model for earth gravity and extended the utilization of this analysis for micro and Martian gravity. The jetting parameters dictate the freezing dynamics in all three gravity conditions (earth, micro and Martian). We corroborated our theoretical analysis with the experimental results obtained in Martian and microgravity conditions simulated by parabolic flight maneuvers. |
Monday, March 6, 2023 2:06PM - 2:18PM |
B32.00014: Analysis of nonlocal electronic correlation on enantioselective adsorption Raymond C Amador van der Waals (vdW) interactions play a central role in the structure, stability, and function of a wide variety of systems, ranging from microscopic, few-molecule systems such as the benzene dimer, to mesoscopic scales as seen in surfaces and clusters. They are responsible for many natural processes, and thus, an accurate description of vdW forces is essential for improving our understanding of various biological, chemical, and physical phenomena[1]. In this talk, we present our findings on the role of non-local vdW interactions on chirality; more specifically, in the enantioselective adsorption and debromination of the 10,10’-dibromo-9,9’-bianthracene (DBBA) and 9-Phenanthracenylboronic acid (9-PBA) molecules, as catalyzed by chiral surfaces of the palladium-gallium (PdGa) intermetallic compound[2]. After a brief recapitulation on the framework of density-functional theory (DFT) with dispersion corrections[3], we discuss its principle shortcomings within the context of many-body perturbation theory, and how our current calculations address and rectify these faults via higher- order treatments of the exchange integrals. We then present several figures of interest – adsorption configurations before and after geometry optimizations, charge localization plots of adsorption, molecular energetics obtained via ab-initio molecular dynamics, as well as the location of the transition state from metadynamics – and explore effects of both vdW interactions and the nonlocal exchange term via inclusion of hybrid functionals[4]. In doing so, we provide the foundations for further study of non-local electronic correlation in chirality. |
Monday, March 6, 2023 2:18PM - 2:30PM |
B32.00015: Stoichiometric control of 2D superconductivity and mobility at SrTiO3-based interfaces Gyanendra Singh, Gerbold Ménard, Guilhem Saïz, Roger Guzman, Wu Zhou, Jordi Fraxedas, Jaume Gázquez, Gervasi Herranz, Nicolas Bergeal, Alexei Kalaboukhov SrTiO3-based conducting interfaces, that exhibit coexistence of gate tunable multi-orbital 2D superconductivity and strong Rashba spin-orbit coupling (RSOC), have ingredients to generate topological superconducting electronics for quantum application. However, the common challenge is to control the superconducting critical temperature (Tc) and electronic mobilities (μ) that are sensitive in 2D from defects, imperfections, cation stoichiometry, etc. originating from non-trivial synthesis process and limits the device dimension from its characteristic length. Besides, the origin conductivity and superconductivity are still debated, the numerous studies on LaAlO3/SrTiO3 interfaces suggest that superconducting condensate only forms in extreme dirty limit and suppresses strongly at low electrostatic doping below Lifshitz transition. Here we report that a small variation of Lanthanum (La) and Aluminum (Al) ratio in Al-rich LaAlO3, as identified in XPS and STEM-EELS measurements, provides an excellent degree of freedom, not yet explored, to fine-tune systematically carrier density, mobility, and strikingly formation of superconducting condensate as well. Gate tunable superconducting phase diagram display even growing Tc below Lifshitz transition attributed to the observed larger electronic mobility which is comparable to superconducting coherence length. Our result paves the way to understand the origin of superconductivity subtler way and form devices with moderate dimensions for topological superconducting electronics. |
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