Дисертації з теми "Single molecule conductance measurements"
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Brooke, Carly. "Synthesis, characterisation and single molecule conductance measurements of organic molecules." Thesis, University of Liverpool, 2012. http://livrepository.liverpool.ac.uk/9397/.
Повний текст джерелаPsychogyiopoulou, Krystallia. "Synthesis, surface spectroscopy and single molecule conductance measurements of some metalloporphyrins." Thesis, University of Liverpool, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.422991.
Повний текст джерелаLanzilotto, Valeria. "Self-assembling and charge transfer properties of thin organic films." Doctoral thesis, Università degli studi di Trieste, 2012. http://hdl.handle.net/10077/7362.
Повний текст джерелаIn the present thesis I dealt the issue of molecular ordering and charge transfer at two types of organic-inorganic interfaces that are representative of the basic constituents of an organic electron device. I investigated i.) the influence of a selected dielectric surface on the ordering of an overlayer of several organic molecules and ii.) the electronic transport properties of a single molecular junction with a metal electrode. Both systems have been characterized by a structural and electronic point of view. Among the techniques available for structural investigation, I made extensive use of Helium Atom Scattering (HAS) and Scanning Tunneling Microscopy (STM). The electronic properties, with particular emphasis to the charge transfer, have been addressed by two methods chosen according to the dimensionality of the system under consideration. For the charge transfer at laterally extended interfaces I used synchrotron based techniques, like Resonant Photoemssion Spectroscopy (RPES), while for the charge transport through a single molecule I used and developed the STM-based break junction technique (STM-BJ). For the first type of interface, I focused on the coupling between the TiO2(110)-1x1 surface and different organic semiconductor molecules: C60, pentacene, perylene-tetracarboxilic-acid-diimide (PTCDI) and perylene. The strong anisotropy of the substrate has been found to drive the adsorption geometry of the molecules leading to the formation of ordered phases (at least for the first layer). In particular pentacene, PTCDI and perylene (polycyclic aromatic hydrocarbons, PAHs) display a common self-assembly mechanism, where the molecules lay on the surface with their long axis oriented parallel to the [001] substrate direction. In the transverse direction [1-10] these molecules are observed to match the substrate periodicity by tilting the molecular plane around the long axis by an angle that depends on the molecular width. Nevertheless the molecule-to-substrate interaction is very weak as indicated by the molecular electronic structure, which is observed by X-ray spectroscopy to remain mostly unperturbed in the first molecular layer. Only PTCDI bears a major interaction with the TiO2(110)-1x1 surface, but confined to the molecular orbitals closest to the gap. The main experimental evidence of this interaction is the appearance of a new molecular filled state in the valence band region close to the Fermi level. By a combined RPES and NEXAFS study we have found that this new electronic state is due to the charge transfer occurring from the substrate Ti defect state (i.e. the excess of electrons associated with oxygen vacancies) to the lowest unoccupied molecular orbital (LUMO). For the second type of hybrid interface, instead, I exploited the nitrogen-link chemistry in order to bridge a phthalocyanine to two gold electrodes and to measure its conductance. In particular, by using the Tetraaza-Cu-Phthalocyanine I investigated the pyridine-gold bond that is relatively weak and insensitive to the local structure, a fundamental requirement for the establishment of well defined and stable transport properties. The weak interaction between the molecule and a representative metal electrode, namely the Au(100) surface, has been confirmed by spectroscopic and STM experiments. At RT the molecules have been found to diffuse on the surface and only at LT (55 K) they can be observed to self-organize into large molecular domains. On these domains, reliable and reproducible single molecule conductance measurements have been performed by using the STM-based break junction method. The conductance value obtained for the Tetraaza-Cu-Phthalocyanine (7x10-4 G0) has been rationalized in terms of the molecular length and degree of conjugation, as well as by correlation to the energy level alignment at the junction.
XXIV Ciclo
1984
Leary, Edmund. "Single Molecule Conductance of Dithiahexyl-Aryl Compounds." Thesis, University of Liverpool, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.507724.
Повний текст джерелаZhao, Xiaotao. "The synthesis and single-molecule conductance of conjugated molecular wires." Thesis, Durham University, 2014. http://etheses.dur.ac.uk/10634/.
Повний текст джерелаPearson, Anita P. "AFM investigation of single molecule force measurements." Thesis, University of Nottingham, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.441016.
Повний текст джерелаRadiom, Milad. "Correlation Force Spectroscopy for Single Molecule Measurements." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/49677.
Повний текст джерелаPh. D.
Berthoumieu, Olivia. "Single molecule studies of seven transmembrane domain proteins." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:ff7ae71d-5481-4523-812b-2128fe32f5fc.
Повний текст джерелаHolden, Seamus J. "Improved methods for sub-diffraction-limit single-molecule fluorescence measurements." Thesis, University of Oxford, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.543548.
Повний текст джерелаPortoles, Jose Fernando. "The development of MEMS devices for traceable single-molecule force measurements." Thesis, University of Nottingham, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.493321.
Повний текст джерелаFraccari, Raquel Leh-na. "Single-molecule DNA detection in nanopipettes using high-speed measurements and surface modifications." Thesis, Imperial College London, 2016. http://hdl.handle.net/10044/1/44085.
Повний текст джерелаTran-Ba, Khanh-Hoa. "Single-molecule diffusion measurements for material characterization in one-dimensional nanostructured polymer films." Diss., Kansas State University, 2015. http://hdl.handle.net/2097/32791.
Повний текст джерелаDepartment of Chemistry
Takashi Ito
This dissertation describes single-molecule tracking (SMT) measurements for the quantitative characterization of one-dimensional (1D) nanostructures in 200 nm-thick surfactant-templated mesoporous silica (STMS) and cylinder-forming polystyrene-poly(ethylene oxide) diblock copolymer (CF-PS-b-PEO) films with a μm-scale thickness. SMT is advantageous for the characterization of nanomaterials over conventional methods because it permits the simultaneous and quantitative assessment of the nanoscale and microscale morphologies, and mass-transport properties of the materials with a high nanometer-scale resolution under ambient conditions. It offers a unique means for the assessment and evaluation of the μm-scale nanostructure alignment in polymer films induced by vertical spin-coating (for STMS films), directional solution flow and solvent-vapor penetration (SVP) methods (both for CF-PS-b-PEO films), highly crucial for many potential technological applications using the materials. Through this work, we have identified suitable sample preparation conditions (e.g. solvent, temperature or solution flow rate) for obtaining highly-ordered mesoporous and microdomain structures over a long-range (> 5 μm). For the quantitative assessment of the 1D SMT data, orthogonal regression analysis was employed, providing assessment of the in-plane orientation and size of individual nanostructures with nanometer-scale precision. The analysis of the 1D trajectory data allowed the radius (ca. 11 nm) of cylindrical PEO microdomains to be estimated, yielding results consistent with the AFM results (ca. 14 nm). The distribution of the trajectory angles offered the estimation of the average orientation and order of the nanostructures in domains/grains for a μm-wide region of the polymer films, revealing the higher efficiency of SVP in the nanostructure alignment as compared to the spin coating and solution flow approaches. Systematic SMT measurements across the film depth and along lateral mm-scale distances afforded valuable insights into the shear- and solvent-evaporation-based alignment mechanisms induced by solution flow and SVP/spin coating approaches, respectively. Fluorescence recovery after photobleaching (FRAP) measurements in a SVP-aligned CF-PS-b-PEO film permitted the longer-range mass-transport properties to be probed, reflecting the effective continuity of the aligned cylindrical nanostructures over > 100 μm in length. In this dissertation, FRAP and more importantly SMT methods have provided a unique and useful means for the in-depth characterization of morphology and mass-transport characteristics in thin polymer films under ambient conditions, in confined spaces, and with a nanometer-scale resolution.
Sapra, K. Tanuj. "Single-Molecule Measurements of Complex Molecular Interactions in Membrane Proteins using Atomic Force Microscopy." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2007. http://nbn-resolving.de/urn:nbn:de:swb:14-1175696409847-74867.
Повний текст джерелаDoroshenko, Olga [Verfasser]. "Accurate structural determination of biomolecules via single-molecule high-precision FRET measurements / Olga Doroshenko." Düsseldorf : Universitäts- und Landesbibliothek der Heinrich-Heine-Universität Düsseldorf, 2020. http://d-nb.info/1203369786/34.
Повний текст джерелаSapra, K. Tanuj. "Single-Molecule Measurements of Complex Molecular Interactions in Membrane Proteins using Atomic Force Microscopy." Doctoral thesis, Technische Universität Dresden, 2006. https://tud.qucosa.de/id/qucosa%3A24922.
Повний текст джерелаJanovjak, Harald. "Exploring the Mechanical Stability and Visco-elasticity of Membrane Proteins by Single-Molecule Force Measurements." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2005. http://nbn-resolving.de/urn:nbn:de:swb:14-1135090167025-44737.
Повний текст джерелаLandry, Matthew. "Analysis of Nanopore Detector Measurements using Machine Learning Methods, with Application to Single-Molecule Kinetics." ScholarWorks@UNO, 2007. http://scholarworks.uno.edu/td/533.
Повний текст джерелаVanDelinder, Virginia Alison. "Microfluidics for blood component separation, medium exchange, response latency measurements, and single molecule fluorescence microscopy." Diss., [La Jolla, Calif.] : University of California, San Diego, 2009. http://wwwlib.umi.com/cr/ucsd/fullcit?p3344833.
Повний текст джерелаTitle from first page of PDF file (viewed Apr. 7, 2009). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 133-155).
Bircher, Roland. "Studies of single-molecule magnets and spin clusters by inelastic neutron scattering and magnetic measurements /." Bern : [s.l.], 2005. http://www.ub.unibe.ch/content/bibliotheken_sammlungen/sondersammlungen/dissen_bestellformular/index_ger.html.
Повний текст джерелаGelléri, Márton [Verfasser], Philippe I. [Akademischer Betreuer] Bastiaens, and Roland [Gutachter] Winter. "TIRF-anisotropy microscopy: homo-FRET and single molecule measurements / Márton Gelléri. Betreuer: Philippe I. Bastiaens. Gutachter: Roland Winter." Dortmund : Universitätsbibliothek Dortmund, 2013. http://d-nb.info/1104736411/34.
Повний текст джерелаDüselder, André [Verfasser], Christoph F. [Akademischer Betreuer] Schmidt, and Sarah [Akademischer Betreuer] Köster. "Single-molecule measurements of Kinesin motor proteins / André Düselder. Gutachter: Christoph F. Schmidt ; Sarah Köster. Betreuer: Christoph F. Schmidt." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2014. http://d-nb.info/1048469956/34.
Повний текст джерелаTeeling-Smith, Richelle Marie. "Single Molecule Electron Paramagnetic Resonance and Other Sensing and Imaging Applications with Nitrogen-Vacancy Nanodiamond." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1424779811.
Повний текст джерелаKurz, Anton [Verfasser], and Dirk-Peter [Akademischer Betreuer] Herten. "Characterization and Application of Photon-Statistics in Single-Molecule Measurements for Quantitative Studies of Fluorescently Labeled Samples / Anton Kurz ; Betreuer: Dirk-Peter Herten." Heidelberg : Universitätsbibliothek Heidelberg, 2013. http://d-nb.info/1177247879/34.
Повний текст джерелаSendler, Torsten. "Leitwertkontrolle einzelner elektrisch kontaktierter Moleküle." Doctoral thesis, Helmholtz-Zentrum Dresden-Rossendorf, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:d120-qucosa-184190.
Повний текст джерелаGross, Linda C. M. "Applications of droplet interface bilayers : specific capacitance measurements and membrane protein corralling." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:0b7ffba6-b86d-499c-a93f-3b2fc46a427b.
Повний текст джерелаAlwan, Monzer. "Etude experimentale de contacts métalliques et moléculaires ponctuels : de l'objet individuel aux statistiques." Thesis, Aix-Marseille, 2012. http://www.theses.fr/2012AIXM4106/document.
Повний текст джерелаWe present here an experimental work which contributes to the study of metallic and molecular point contacts using broken junctions-based devices developed in our team. Under ambient environmental conditions, these techniques are particularly adapted to two disciplinary fields: molecular electronics and nano-mechanics.We have studied the lifetime of gold contacts, which rarely exceed ten milliseconds at room temperature.Through statistical analyses of conductance measurements, we show that this lifetime is limited by the mechanical strain applied to the junction. These results allowed us to propose a breaking mechanism, and to define optimal conditions for the formation of the contacts at room temperature. We present then a preliminary study of conductance measurements of a single molecule, using a broken junction device as well as a scanning tunneling microscope.The results indicate that, despite the conductance measure of a single molecule is possible the observed stability should be considered before envisaging applications
Hemmig, Elisa Alina. "DNA origami structures for artificial light-harvesting and optical voltage sensing." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/274005.
Повний текст джерелаTsai, Miao-Ling, and 蔡妙伶. "Molecular Junctions Stabilized Manually via Tactile Feedback for the Measurements of Single–Molecule Conductance." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/24919375857256461151.
Повний текст джерела國立臺灣大學
化學研究所
98
The ultimate goal of molecular electronics is the construction of electronic circuit devices from individual molecules and the electron transport through single molecules is crucial to molecular devices. The factors that influence electron transport depend not only on molecules themself but also the detail of molecule-electrode contacts. The latter is considered to be the least controllable aspect of experiments would cause conductance variability due to the contact geometry in molecular junctions. In the scanning tunneling microscopy break junction (STM BJ) method, continuous tip retraction would lead to contact conformation changes, we try to establish a stable contact between the molecule and metal probes and ensure that not the properties of an ensemble but a single molecule are been found. The results presented here is the studies of the single molecular conductance for the self-assembled monolayers (SAMs) of hexanedithiol and octanedithiol (SH-(CH2)n-HS, n=6 and 8) molecules onto Au electrodes by the conductive atomic force microscopy and the PicoAngler. By utilizing the PicoAngler with a force-feedback knob for manual control of the fixed tip-substrate spacing, which can stabilize the molecular junction, our method can not only construct the conductance histogram without the preselection process, but also receive the experimental results similar to the previous reports.
Chang, Wei-Hsuan, and 張瑋軒. "Measurements of Single-Molecule Conductance by Conductive Atomic Force Microscopy with Tactile Feedback: the Effect of the Cantilever Force Constant." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/38430640100520236824.
Повний текст джерела國立臺灣大學
化學研究所
99
Abstract In the field of molecular electronics, c-AFM BJ (conductive atomic force microscopy break junction) is one of the methods employed to create molecular junctions of metal–molecule–metal configurations through which single-molecule conductance can be measured. Reported in this thesis work is, for the first time, the acquisition of single-molecule conductance can be correlated with the applied stretching force at the molecular junction by taking advantage of a tensile sensor integrated in the c-AFM. Alkanedithiols (HS(CH2)nSH, n = 6, 8, and 10) are the model compounds and the consistence of their conductance values with literature reports validates this methodology. We construct two-dimensional (2D) histograms from the conductance and force traces using three kinds of force constant of tip (k = 40, 0.3, 0.03 N/m). We have found that (1) The conductance is independent of stretching force at k = 40 N/m. (2) The distribution of conductance become narrow with increasing stretching force at k = 0.3, 0.03 N/m. (3) Multi sets of conductance values are found at k = 0.3, reflecting the reduction of thermal fluctuation by using smaller force constant of tip. A force feedback system, PicoAngler, for fixing tip-substrate spacing to monitor the conductance of single molecular junction with a long lifetime (≈ 450 s) that enables detailed nature of the conductance of single molecules to be gained. When the stretching force is small (0.2 (± 0.1) nN), multi sets of conductance in I-t and I-V curves are produced due to change of conformation in an alkylene chain and binding sites (bridge or the hollow site) of thiolates on gold. On the contract, when the stretching force is large (0.8 (± 0.1) nN), conductance is centralized, resulted from only elongated conformers and the atop binding site.
"Measurements and Control of Charge Transport through Single DNA Molecules via STM Break Junction Technique." Doctoral diss., 2016. http://hdl.handle.net/2286/R.I.38368.
Повний текст джерелаDissertation/Thesis
Doctoral Dissertation Chemistry 2016
Dell, Emma Jane. "Single Molecule Conductance of Oligothiophene Derivatives." Thesis, 2015. https://doi.org/10.7916/D8TX3D71.
Повний текст джерелаKamenetska, Maria. "Single Molecule Junction Conductance and Binding Geometry." Thesis, 2012. https://doi.org/10.7916/D82N587J.
Повний текст джерелаFrei, Michael. "Force and Conductance Spectroscopy of Single Molecule Junctions." Thesis, 2012. https://doi.org/10.7916/D8H70NS8.
Повний текст джерелаKocun, Marta. "Single molecule force measurements of chitosan." Thesis, 2007. http://spectrum.library.concordia.ca/975687/1/MR40858.pdf.
Повний текст джерелаKim, Nathaniel T. "Single Molecule Conductance and Junction Breakdown of Strained Cyclic Disilanes." Thesis, 2016. https://doi.org/10.7916/D8BR8SP7.
Повний текст джерелаPan, Xiaoyun. "Single molecule conductance of biological building blocks purines and imidazole." Thesis, 2019. https://hdl.handle.net/2144/36040.
Повний текст джерелаDüselder, André. "Single-molecule measurements of Kinesin motor proteins." Doctoral thesis, 2013. http://hdl.handle.net/11858/00-1735-0000-0022-5E5D-1.
Повний текст джерелаKao, Jing-Yao, and 高靖堯. "Thermal conductance and thermoelectric figure of merit of Single-Molecule junctions." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/78u2c4.
Повний текст джерела國立交通大學
電子物理系所
104
We investigate the phonon’s thermal current in nanoscale junctions using classical nonequilibrium molecular dynamics simulations(NEMD). The quantum mechanical corrections due to Bose-Einstein distributions are also considered in low-temperature regime.We calculate the thermal conductance of single-molecule junctions connecting to two temperature reservoirs. We systematically investigate the dependence of thermal conductance on lengths and strain in nanowires in a wide range of temperatures. We also investigate its electronic transport properties in the framework of parameter-free density functional theory combined with the Lippmann-Schwinger formalism in scattering approach.We observe that the thermal conductance is proportional to temperature in the low-temperature regime, while the dependence of thermal conductivity on temperature is relatively weak in the high-temperature regime. In atomic junctions, the thermal conductance increases with the increasing compressive stress, and tensile stress can result in a cone shape structure which decrease the magnitudes of thermal. Differently, the thermal conductance only decrease with compressive stress in the molecular junction.In metal nanowire, electronic thermal conductance dominate the total thermal conductance and conversely, the phonon transport dominates the contribution to the thermal conductance in molecular junctions. In addition, we investigate the phonon’s thermal conductance using week-link model in the low-temperature regime and NEMD simulation in the high-temperature regime. We observe that the value of ZT reveals the power law behavior that falls into four phases, ZT∝T^x,x=2,0,2.26,3.
Ting, Ta-Cheng, and 丁大成. "Tuning the Single-molecule Conductance of Metal String Complexes by Electrochemical Gating." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/39214636188149388162.
Повний текст джерела國立臺灣大學
物理研究所
103
The single-molecule conductance is affected by the electron transport through the electrode–molecule–electrode junctions. One of the most important factors is the energy-level difference between the electrode Fermi level and the frontier molecular orbitals. This energy difference can be controlled by electrochemical gating, which means pushing the potential of the working electrode toward the redox potential of the molecule. The compounds here are extended metal-atom chains (EMACs), which have well-defined one-electron oxidation reactions, to study the effect of energy-level alignment on the single-molecule conductance. For the scans of electrochemical potential, the single-molecule conductance is measured at a fixed bias and monitored as a function of electrochemical potential. On the other hand, single-molecule i–V curves are obtained at fixed electrochemical potentials. Transition voltages derived from the corresponding Fowler-Nordheim plots are well correlated with the energy barrier heights. Larger conductance and smaller energy barrier heights were found when electrochemical potential was just about the redox potential, indicating the effect of energy-level alignment.
"Electronic Single Molecule Measurements with the Scanning Tunneling Microscope." Doctoral diss., 2016. http://hdl.handle.net/2286/R.I.38718.
Повний текст джерелаDissertation/Thesis
Doctoral Dissertation Physics 2016
Benesch, Claudia [Verfasser]. "Charge transport in single molecule junctions : vibronic effects and conductance switching / Claudia Benesch." 2008. http://d-nb.info/988165627/34.
Повний текст джерелаHuang, Min-Jie, and 黃敏傑. "Single-Molecule Conductance of Heteropentanuclear Metal String Complexes: Electronic Coupling at Molecule-Electrode Contact and Negative Differential Resistance Behavior." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/91380980853210217452.
Повний текст джерела國立臺灣大學
化學研究所
101
The development of ideal molecule−electrode contacts and the design of functional molecular wires are critical for the realization of molecular electronics. The good molecule−electrode contacts exhibit efficient charge transportation and thus confer large single-molecule conductance. To derive the intrinsic properties of the MMM contact, the conductance of a series of alkanes terminated with–SH, –NCS, and –CN on Au, Pd and Pt were carried out by using the method of STM-bj. The results show the single-molecule conductance via Pt contact is 2~5-fold superior to those via Au contact. Among the three headgroups, –SH bears the largest contact conductance and –CN is smallest. Such disparity in their conductance can be ascribed to the degree of the headgroup–electrode coupling. Simulated bond angles and Mayer bond order at the contact suggest that π characters are significantly involved at Pt and Pd contacts, while σ characters is preferably adopted at Au contacts. These findings demonstrate that the electronic coupling at the contact plays an important factor on contact conductance and on the measured single-molecule conductance. Moreover, we purpose that the resistance of molecular backbone can be extracted via Landauer formula. The resistance values for the same framework are found to be independent of teminal headgroup and electrode material, manifesting that this approach can evaluate quantitatively the resistance of functional moieties from the measured value. To tune electric conductance of extended metal atom chains, the first pentametal EMAC (extended metal-atom chain) of heteronuclear backbone was synthesized by mixing a weakly coupled nickel-atom chain with an Ru2 unit, which has strong metal-metal interactions. The resulted Ni‒Ru‒Ru‒Ni‒Ni is 4-fold more conductive than that of its pentanickel analogue. DFT/UB3LYP analysis shows that the incorporation of the Ru2 unit enhances metal-metal interaction and thus results in the conductance superior to that of pentanickel EMAC. Single-molecule I-V characteristic of NiRu2Ni2(tpda)4(NCS)2 exhibits NDR (negative differential resistance) behavior, unobserved for pentanickel or pentaruthenium complexes. A plausible explanation is derived based on the simulation of energy level and the correlation of the NDR peak positions with the EFermi of Au, Pd, and Pt. The energy levels contributed by the Ru2 moiety make the frontier orbitals discrete such that the molecular conductance decreases upon ramping the electrode EFermi from where aligned with the MOs to nonresonant regimes. Thus, the discrete levels near HOMO are accounted for NDR phenomena.
Chang, Wei-Cheng, and 張惟程. "Syntheses and Studies of Nonhelical Trinuclear (Mo2/M)Heterometallic String Complexes with High Single-Molecule Conductance." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/5k77gc.
Повний текст джерела國立臺灣大學
化學研究所
106
The concept of single-molecule electronics has attracted the interest of many scientists across various disciplines on the platform of nanotechnology. Among these molecular systems, molecules featuring chains of transition-metal atoms are of great interest for their potential applications in molecular electronic devices, because these complexes resemble macroscopic metal wires in a miniature form at the atomic scale. The development of heteronuclear metal string complexes (HMSCs) provides an ideal system for the investigation of the nature of heterometallic electronic effects and molecular electronic applications. Here we report the synthesis and characterization of three HMSCs with planar 1,8-naphthyridin-2(1H)-one (Hnpo) ligand-stabilized tri-metal cores. The frameworks of these HMSCs 1-13, Mo2M(npo)4X2, M= Mn, Fe, Co, Ni, Cu, Zn, X = Cl, NCS were determined to be nonsymmetric by X-ray diffraction, in spite of disordered metal centers. These HMSCs are isostructural (2,2)-trans structure. Unlike those supported by dpa–, these npo-based HMSCs are not helical. A smaller dihedral angle of ∠N-Mo-Mo-N is envisaged to be more favourable for inter-molybdenum dx2-y2 interactions, leading to a larger Mo–Mo bond order. Measurements of the magnetic properties were carried out on a SQUID magnetometer. The members of this new series of HMSCs are paramagnetic due to the terminal 3d-metal ions. The conductance of the complexes was studied by the method of STM-BJ (scanning tunnelling microscopy-based break junction) in which the molecular junctions of electrode-molecule-electrode configurations were generated by breaking the fused tip-substrate contact. The conductance of metal strings was found correlated strongly with metal-metal interactions or bond orders. HMSCs 4, 6 and 8 exhibit higher conductance than homometallic predecessors like [Ni3(dpa)4(NCS)2] and [Cr3(dpa)4(NCS)2]. The increase can be attributed to the Mo Mo quadruple bond of these complexes. The transformation of MoMoFe to MoMoNi and MoMoCo heteronuclear complexes can be achieved by direct metal replacement. The metal substitution method improves not only the purity but also the yield. In addition to the high electric conductance for the potential applications as molecular wires, these new HMSCs are the first series of non-helical metal strings in which the ligands are co-planar with the metal-atom chain. In the second part, we also successfully synthesized triruthenium metal string, [Ru3(npo)4Cl2][PF6] (22) and [Ru3(npo)4(NCS)2] (23) supported by Hnpo ligands. X-ray single crystal analysis shows that compound 22 and 23 exhibits a nonlinear [Ru3]7+ and [Ru3]6+ backbone (∠= 172.72° and ∠=170.62°) with Ru–Ru bond lengths (2.324 and 2.303 Å). We propose compound 22 is paramagnetic species and compound 23 is diamagnetic species.
Ko, Chih-Hung, and 柯志宏. "Superior Contact for Single-Molecule Conductance: Electronic Coupling of Thiolate and Isothiocyanate on Pt, Pd, and Au." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/72957989893864861031.
Повний текст джерела國立臺灣大學
化學研究所
97
One of the critical issues for molecular electronics is the development of optimal molecule-electrode contacts which have long been expected to substantially influence the measured single-molecule conductance. However, other than gold, systematic studies of a homologous series of molecules to extract the headgroup-metal barrier have not been reported. This thesis work scrutinizes the effect of electrode materials on single-molecule conductance by examining alkanedithiols anchored onto Au and Pt electrodes as well as alkanediisothiocyanates on Au, Pd, and Pt. STM-BJ (scanning tunneling microscopy break junction) was employed to create thousands of molecular junctions and to obtain single-molecule conductance. The results show that all molecule-electrode combination exhibits high- and low-conductance datasets (HC and LC). Compared to the contact resistance measured using Au electrodes, alkanediisothiocyanates are about 20% ~ 60% less resistive on Pd and Pt and alkanedithiols are about 50% less resistive on Pt. The difference is ascribed to their Fermi energies and the pi characters of the atoms at the contact. The dependence of single-molecule conductance on the electrode materials is also true for a linear trimetal complex, [Ni3(dpa)4(NCS)2] (dpa = 2,2''-dipyridylamide), suggesting the generality of the findings for both saturated and highly conductive molecular wires. For alkanediisothiocyanates, the probability of acquiring staircase-like traces among all i-s traces increases from 27% on Au to 37-42% on Pd or Pt electrodes. Using density functional theory (DFT), adsorption energies on three-fold hollow site and ontop site are in agreement with probabilities of HC and LC. Calculations of transmission function and comformation of headgroup-metal interface are also carried out to facilitate the rationalization using HOMO-LUMO gap and electronic coupling at the contact.
Tsai, Feng-Jen, and 蔡豐任. "Single-Molecule Conductance of Rh and Ni Heterometallic String Complexes in Mixed Solvents of Dichloromethane and 1,2,4-Trichlorobenzene." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/27324345896886006881.
Повний текст джерела國立臺灣大學
化學研究所
101
Metal string complexes (MSCs), in which the metal centers are co-linear and stably coordinated by four oligopyridylamido ligands, have been demonstrated a unique category of conductive molecular wires. Bond orders which describe the strength of metal-metal interactions are qualitatively well correlated with the single-molecule conductance of the MSCs. Previous examples are limited to homometallic string complexes in which the metal centers are composed of the same element. Explored in this thesis work are the conductive properties of heterometallic string complexes (HMSCs). Specifically, the sequences of the metal cores are RhRhNi, NiRhNi, RhRhNiNiNi, and RhRhRhNiNi. Also examined are Ni3 and Ni5 MSCs. Methods of compound purification and crystallization are improved. The experimental protocols and data analysis are also modified. The conductance measurements are carried out through electrode-molecule-electrode junctions created by an STM (scanning tunneling microscope) tip which repeatedly impinges into and retracts from the substrate. In this study, the tip-substrate contact is ensured by an external device, while it was not monitored in our earlier work. The conductance histograms are prepared by pooling all acquired conductance traces while, in the past, only those with step-like features were selectively used. The results show that the conductance histograms are featureless and that it is very difficult to determine the conductance values for pentametallic string complexes, even for Ni5 MSC. X-ray crystallographic data reveal that solvent molecules, present in the unit cell by previous purification methods, are absent for the new samples. Accordingly, mixed solvents exhibiting a range of polarity are utilized to improve the solubility of MSCs. The conductance peaks are slightly more pronounced in a more polar environment. The conductance peaks of Ni3, Ni5, and NiRhNi are solvent-independent, while the peak positions of asymmetric RhRhNi, RhRhNiNiNi, and RhRhRhNiNi shift associated with the solvent utilized. According to published researches in the effect of environment on molecular junction, we proposed that solvent molecules will affect the head group and alter gold-sulfur contact.
傅明棟. "Studies of Single-Molecule Conductance: Headgroup-Electrode Contact and Negative Differential Resistance Behavior of [Ru2Ni3(tpda)4(NCS)2] Complex." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/93106096588913094967.
Повний текст джерела國立清華大學
化學系
98
The realization of molecular electronics requires comprehension of single molecular I-V characteristics. Aside from the electron transporting properties of the molecular framework, the molecule-electrode binding contributes significantly to the contact resistance, Rn=0, and thus to the values of single-molecule resistance. Isothiocyanate (–NCS) and cyanate (–CN), versatile ligands for EMACs (Extended Metal-Atom Chains), can bind onto metal substrate to complete a metal-molecule-metal configuration for the external measurements. To isolate the contact effect of contact between headgroup and electrode from other factors, alkanediisothiocyanates and alkanedicyanates are studied because the large HOMO-LUMO gap of alkyl chains is not sensitive to the number of methylene units. The conductance at the single molecular level has long been expected to be matched strongly with the Fermi level of metal electrodes. Another factor to affect the electron transporting characteristic of EMACs is varying the metel center. By incorporating a diruthenium moiety into a string of nickel cores, the heteropentanuclear Ni-Ru-Ru-Ni-Ni EMAC has a single-molecule conductance of 6.3 ± 1.0 MΩ, 4-fold superior to that of the pentanickel analogue (23.3 ± 4.1 MΩ) at the ohmic region and results in NDR characteristics, unobserved for its analogues of pentanickel or pentaruthenium EMACs. The diruthenium unit is accounted for discrete HOMO levels that lead to the NDR behavior as a result of the energy alignment with the electrode Fermi. From the Landauer equation, we only focused on the resistance of molecular without the contact. The resistance of trinickel EMAC is 330 kΩ, one order less than hexamethylene.
Janovjak, Harald [Verfasser]. "Exploring the mechanical stability and visco-elasticity of membrane proteins by single-molecule force measurements / vorgelegt von Harald Janovjak." 2005. http://d-nb.info/978344677/34.
Повний текст джерелаSapra, K. Tanuj [Verfasser]. "Single molecule measurements of complex molecular interactions in membrane proteins using atomic force microscopy / vorgelegt von K. Tanuj Sapra." 2007. http://d-nb.info/983900051/34.
Повний текст джерелаNejedlý, Jindřich. "Syntéza π-elektronových systémů vhodných pro přenos a retenci náboje". Doctoral thesis, 2021. http://www.nusl.cz/ntk/nusl-437757.
Повний текст джерела