Gas Sensing Discrimination using a Cellular Nonlinear Network Al Chawa, Mohamad Moner; Picos, Rodrigo; Panes-Ruiz, Luis Antonio ...
2021 17th International Workshop on Cellular Nanoscale Networks and their Applications (CNNA),
2021-Sept.-29
Conference Proceeding
In this work, we developed a signal processing Cellular Nonlinear Network (CNN) for the detection and classification of real sensor data obtained from a memristive gas sensors matrix. Applying a gas ...sensor CNN we can discriminate between hazardous gases such as Ammonia (NH 3 ) and Hydrogen Sulfide (H 2 S) and determine their concentration levels.
The quantum dynamics of electrons in bulk states is investigated by scanning tunneling microscopy and spectroscopy on a Ag(100) surface. By measuring conductance maps above a threshold voltage, we ...observe standing waves at step edges and defects. We interpret these to originate from electrons in a bulk band edge at the Gamma point. From the spatially decaying waves, the wave vector and the quantum coherence parameters-coherence length, lifetime, and linewidth-are determined as a function of energy. We measure a coherence length of about 5-7 A, which is order of magnitudes lower than typically observed for surface or image-potential states. The energy of the band edge is extracted from the dispersion relation and agrees with the peak measured in scanning tunneling spectra at 1.9 eV above the Fermi energy. Theoretical calculations confirm the nature of the state elucidating the experimental findings.
In situ low-voltage aberration corrected transmission electron microscopy (TEM) observations of the dynamic entrapment of a C sub(60) molecule in the saddle of a bent double-walled carbon nanotube is ...presented. The fullerene interaction is non-covalent, suggesting that enhanced pi - pi interactions (van der Waals forces) are responsible. Classical molecular dynamics calculations confirm that the increased interaction area associated with a buckle is sufficient to trap a fullerene. Moreover, they show hopping behavior in agreement with our experimental observations. Our findings further our understanding of carbon nanostructure interactions, which are important in the rapidly developing field of low-voltage aberration corrected TEM and nano-carbon device fabrication.
Conductive metal-organic frameworks (MOFs) are emerging electroactive materials for (opto-)electronics. However, it remains a great challenge to achieve reliable MOF-based devices via the existing ...synthesis methods that are compatible with the complementary metal-oxide-semiconductor technology, as the surface roughness of thus-far synthetic MOF films or pellets is rather high for efficient electrode contact. Here, we develop an on-liquid-gallium surface synthesis (OLGSS) strategy under chemical vapor deposition (CVD) conditions for the controlled growth of two-dimensional conjugated MOF (2D c-MOF) thin films with ten-fold improvement of surface flatness (surface roughness can reach as low as ~2 Å) compared with MOF films grown by the traditional methods. Supported by theoretical modeling, we unveil a layer-by-layer CVD growth mode for constructing flattening surfaces, that is triggered by the high adhesion energy between gallium (Ga) and planar aromatic ligands. We further demonstrate the generality of the as-proposed OLGSS strategy by reproducing such a flat surface over nine different 2D c-MOF films with variable thicknesses (~2 to 208 nm) and large lateral sizes (over 1 cm2). The resultant ultra-smooth 2D c-MOF films enable the formation of high-quality electrical contacts with gold (Au) electrodes, leading to a reduction of contact resistance by over ten orders of magnitude compared to the traditional uneven MOF films. Furthermore, due to the efficient interfacial interaction benifited from the high-quality contacts, the prepared van der Waals heterostructure (vdWH) of OLGSS c-MOF and MoS2 exhibits intriguing photoluminescence (PL) enhancement, PL peak shift and large work function modulation. The establishment of the reliable OLGSS method provides the chances to push the development of MOF electronics and the construction of multicomponent MOF-based heterostructure materials.
In the latest experimental advances, Ni-, Co- and Cu-HAB MOFs were synthesized in 2D forms, with high electrical conductivities and capacitances as well. Motivated by these experimental advances, we ...employed first-principles simulations to explore the mechanical, thermal stability and electronic properties of single-layer Ag-, Co-, Cr-, Cu-, Fe-, Mn-, Ni-, Pd- and Rh-HAB MOFs. Theoretical results reveal that Co-, Cr-, Fe-, Mn-, Ni-, Pd- and Rh-HAB nanosheets exhibit linear elasticity with considerable tensile strengths. Ab-initio molecular dynamics results confirm the high thermal stability of all studied nanomembranes. Co- and Fe-HAB monolayers show metallic behavior with low spin-polarization at the Fermi level. Single-layer Ag-, Cu-, Cr-, and Mn-HAB however yield perfect half-metallic behaviors, thus can be promising candidates for the spintronics. In contrast, Ni-, Pd- and Rh-HAB monolayers exhibit nonmagnetic metallic behavior. The insights provided by this investigation confirm the stability and highlight the outstanding physics of transition metal-HAB nanosheets, which are not only highly attractive for the energy storage systems, but may also serve for other advanced applications, like spintronics.
The physical origin of the so-called chirality-induced spin selectivity (CISS) effect has puzzled experimental and theoretical researchers over the past few years. Early experiments were interpreted ...in terms of unconventional spin-orbit interactions mediated by the helical geometry. However, more recent experimental studies have clearly revealed that electronic exchange interactions also play a key role in the magnetic response of chiral molecules in singlet states. In this investigation, we use spin-polarized closed shell density functional theory calculations to address the influence of exchange contributions to the interaction between helical molecules as well as of helical molecules with magnetized substrates. We show that exchange effects result in differences in the interaction properties with magnetized surfaces, shedding light into the possible origin of two recent important experimental results: enantiomer separation and magnetic exchange force microscopy with AFM tips functionalized with helical peptides.
A key step towards building single molecule machines is to control the rotation of molecules and nanostructures step by step on a surface. Here, we used the tunneling electrons coming from the tip of ...a scanning tunneling microscope to achieve the controlled directed rotation of complex o-MeO-DMBI molecules. We studied the adsorption of single o-MeO-DMBI molecules on Au(111) by scanning tunneling microscopy at low temperature. The enantiomeric form of the molecule on the surface can be determined by imaging the molecule by STM at high bias voltage. We observed by lateral manipulation experiments that the molecules chemisorb on the surface and are anchored on Au(111) with an oxygen-gold bond via their methoxy-group. Driven by inelastic tunneling electrons, o-MeO-DMBI molecules can controllably rotate, stepwise and unidirectional, either clockwise or counterclockwise depending on their enantiomeric form.
The miniaturization of gears towards the nanoscale is a formidable task posing a variety of challenges to current fabrication technologies. In context, the understanding, via computer simulations, of ...the mechanisms mediating the transfer of rotational motion between nanoscale gears can be of great help to guide the experimental designs. Based on atomistic molecular dynamics simulations in combination with a nearly rigid-body approximation, we study the transmission of rotational motion between molecule gears and solid-state gears, respectively. For the molecule gears under continuous driving, we identify different regimes of rotational motion depending on the magnitude of the external torque. In contrast, the solid-state gears behave like ideal gears with nearly perfect transmission. Furthermore, we simulate the manipulation of the gears by a scanning-probe tip and we find that the mechanical transmission strongly depends on the center of mass distance between gears. A new regime of transmission is found for the solid-state gears.
PDF
