@article{14287, abstract = {We describe an approach to bottom-up fabrication that allows integration of the functional diversity of proteins into designed three-dimensional structural frameworks. A set of custom staple proteins based on transcription activator–like effector proteins folds a double-stranded DNA template into a user-defined shape. Each staple protein is designed to recognize and closely link two distinct double-helical DNA sequences at separate positions on the template. We present design rules for constructing megadalton-scale DNA-protein hybrid shapes; introduce various structural motifs, such as custom curvature, corners, and vertices; and describe principles for creating multilayer DNA-protein objects with enhanced rigidity. We demonstrate self-assembly of our hybrid nanostructures in one-pot mixtures that include the genetic information for the designed proteins, the template DNA, RNA polymerase, ribosomes, and cofactors for transcription and translation.}, author = {Praetorius, Florian M and Dietz, Hendrik}, issn = {1095-9203}, journal = {Science}, number = {6331}, publisher = {American Association for the Advancement of Science}, title = {{Self-assembly of genetically encoded DNA-protein hybrid nanoscale shapes}}, doi = {10.1126/science.aam5488}, volume = {355}, year = {2017}, } @article{14290, abstract = {DNA nanotechnology, in particular DNA origami, enables the bottom-up self-assembly of micrometre-scale, three-dimensional structures with nanometre-precise features1,2,3,4,5,6,7,8,9,10,11,12. These structures are customizable in that they can be site-specifically functionalized13 or constructed to exhibit machine-like14,15 or logic-gating behaviour16. Their use has been limited to applications that require only small amounts of material (of the order of micrograms), owing to the limitations of current production methods. But many proposed applications, for example as therapeutic agents or in complex materials3,16,17,18,19,20,21,22, could be realized if more material could be used. In DNA origami, a nanostructure is assembled from a very long single-stranded scaffold molecule held in place by many short single-stranded staple oligonucleotides. Only the bacteriophage-derived scaffold molecules are amenable to scalable and efficient mass production23; the shorter staple strands are obtained through costly solid-phase synthesis24 or enzymatic processes25. Here we show that single strands of DNA of virtually arbitrary length and with virtually arbitrary sequences can be produced in a scalable and cost-efficient manner by using bacteriophages to generate single-stranded precursor DNA that contains target strand sequences interleaved with self-excising ‘cassettes’, with each cassette comprising two Zn2+-dependent DNA-cleaving DNA enzymes. We produce all of the necessary single strands of DNA for several DNA origami using shaker-flask cultures, and demonstrate end-to-end production of macroscopic amounts of a DNA origami nanorod in a litre-scale stirred-tank bioreactor. Our method is compatible with existing DNA origami design frameworks and retains the modularity and addressability of DNA origami objects that are necessary for implementing custom modifications using functional groups. With all of the production and purification steps amenable to scaling, we expect that our method will expand the scope of DNA nanotechnology in many areas of science and technology.}, author = {Praetorius, Florian M and Kick, Benjamin and Behler, Karl L. and Honemann, Maximilian N. and Weuster-Botz, Dirk and Dietz, Hendrik}, issn = {1476-4687}, journal = {Nature}, number = {7683}, pages = {84--87}, publisher = {Springer Nature}, title = {{Biotechnological mass production of DNA origami}}, doi = {10.1038/nature24650}, volume = {552}, year = {2017}, } @article{14308, abstract = {Here we describe an approach to bottom-up fabrication with nanometer-precision that allows integrating the functional diversity of proteins in designed three-dimensional structural frameworks. We reimagined the successful DNA origami design principle using a set of custom staple proteins to fold a double-stranded DNA template into a user-defined shape. Each staple protein recognizes two distinct double-helical DNA sequences and can carry additional functionalities. The staple proteins we present here are based on the transcription activator-like (TAL) effector proteins. Due to their repetitive structure these proteins offer a unique programmability that enables us to construct numerous staple proteins targeting any desired DNA sequence. Our approach is general, meaning that many different objects may be created using the same set of rules, and it is modular, because components can be modified or exchanged individually. We present rules for constructing megadalton-scale DNA-protein hybrid nanostructures; introduce important structural motifs, such as curvature, corners, and vertices; describe principles for creating multi-layer DNA-protein objects with enhanced rigidity; and demonstrate the possibility to combine our DNA-protein hybrid origami with conventional DNA nanotechnology. Since all components can be encoded genetically, our structures should be amenable to biotechnological mass-production. Moreover, since the target objects can self-assemble at room temperature in near-physiological buffer, our hybrid origami may also provide an attractive method to realize positioning and scaffolding tasks in vivo. We expect our method to find application both in scaffolding protein functionalities and in manipulating the spatial arrangement of genomic DNA.}, author = {Praetorius, Florian M and Dietz, Hendrik}, issn = {0006-3495}, journal = {Biophysical Journal}, keywords = {Biophysics}, number = {3}, publisher = {Elsevier}, title = {{Genetically encoded DNA-protein hybrid origami}}, doi = {10.1016/j.bpj.2016.11.171}, volume = {112}, year = {2017}, } @article{14309, abstract = {Establishing precise control over the shape and the interactions of the microscopic building blocks is essential for design of macroscopic soft materials with novel structural, optical and mechanical properties. Here, we demonstrate robust assembly of DNA origami filaments into cholesteric liquid crystals, one-dimensional supramolecular twisted ribbons and two-dimensional colloidal membranes. The exquisite control afforded by the DNA origami technology establishes a quantitative relationship between the microscopic filament structure and the macroscopic cholesteric pitch. Furthermore, it also enables robust assembly of one-dimensional twisted ribbons, which behave as effective supramolecular polymers whose structure and elastic properties can be precisely tuned by controlling the geometry of the elemental building blocks. Our results demonstrate the potential synergy between DNA origami technology and colloidal science, in which the former allows for rapid and robust synthesis of complex particles, and the latter can be used to assemble such particles into bulk materials.}, author = {Siavashpouri, M and Wachauf, CH and Zakhary, MJ and Praetorius, Florian M and Dietz, H and Dogic, Z}, issn = {1476-4660}, journal = {Nature Materials}, number = {8}, pages = {849--856}, publisher = {Springer Nature}, title = {{Molecular engineering of chiral colloidal liquid crystals using DNA origami}}, doi = {10.1038/nmat4909}, volume = {16}, year = {2017}, } @inproceedings{14310, author = {Siavashpouri, Mahsa and Wachauf, Christian and Zakhary, Mark and Praetorius, Florian M and Dietz, Hendrik and Dogic, Zvonimir}, booktitle = {APS March Meeting 2017}, publisher = {APS}, title = {{Molecular engineering of colloidal liquid crystals using DNA origami}}, year = {2017}, } @article{1433, abstract = {Phat is an open-source C. ++ library for the computation of persistent homology by matrix reduction, targeted towards developers of software for topological data analysis. We aim for a simple generic design that decouples algorithms from data structures without sacrificing efficiency or user-friendliness. We provide numerous different reduction strategies as well as data types to store and manipulate the boundary matrix. We compare the different combinations through extensive experimental evaluation and identify optimization techniques that work well in practical situations. We also compare our software with various other publicly available libraries for persistent homology.}, author = {Bauer, Ulrich and Kerber, Michael and Reininghaus, Jan and Wagner, Hubert}, issn = { 0747-7171}, journal = {Journal of Symbolic Computation}, pages = {76 -- 90}, publisher = {Academic Press}, title = {{Phat - Persistent homology algorithms toolbox}}, doi = {10.1016/j.jsc.2016.03.008}, volume = {78}, year = {2017}, } @article{17936, abstract = {We report that the single‐molecule junction conductance of thiol‐terminated silanes with Ag electrodes are higher than the conductance of those formed with Au electrodes. These results are in contrast to the trends in the metal work function Φ(Ag)<Φ(Au). As such, a better alignment of the Au Fermi level to the molecular orbital of silane that mediates charge transport would be expected. This conductance trend is reversed when we replace the thiols with amines, highlighting the impact of metal–S covalent and metal–NH2 dative bonds in controlling the molecular conductance. Density functional theory calculations elucidate the crucial role of the chemical linkers in determining the level alignment when molecules are attached to different metal contacts. We also demonstrate that conductance of thiol‐terminated silanes with Pt electrodes is lower than the ones formed with Au and Ag electrodes, again in contrast to the trends in the metal work‐functions.}, author = {Li, Haixing and Su, Timothy A. and Camarasa‐Gómez, María and Hernangómez‐Pérez, Daniel and Henn, Simon E. and Pokorný, Vladislav and Caniglia, Caravaggio D. and Inkpen, Michael S. and Korytár, Richard and Steigerwald, Michael L. and Nuckolls, Colin and Evers, Ferdinand and Venkataraman, Latha}, issn = {1521-3773}, journal = {Angewandte Chemie International Edition}, number = {45}, pages = {14145--14148}, publisher = {Wiley}, title = {{Silver makes better eElectrical contacts to thiol‐terminated silanes than Gold}}, doi = {10.1002/anie.201708524}, volume = {56}, year = {2017}, } @article{17937, abstract = {Fabricating nanoscopic devices capable of manipulating and processing single units of charge is an essential step towards creating functional devices where quantum effects dominate transport characteristics. The archetypal single-electron transistor comprises a small conducting or semiconducting island separated from two metallic reservoirs by insulating barriers1,2,3,4,5. By enabling the transfer of a well-defined number of charge carriers between the island and the reservoirs, such a device may enable discrete single-electron operations6,7,8,9. Here, we describe a single-molecule junction comprising a redox-active, atomically precise cobalt chalcogenide cluster wired between two nanoscopic electrodes10,11. We observe current blockade at room temperature in thousands of single-cluster junctions. Below a threshold voltage, charge transfer across the junction is suppressed. The device is turned on when the temporary occupation of the core states by a transiting carrier is energetically enabled, resulting in a sequential tunnelling process and an increase in current by a factor of ∼600. We perform in situ and ex situ cyclic voltammetry as well as density functional theory calculations to unveil a two-step process mediated by an orbital localized on the core of the cluster in which charge carriers reside before tunnelling to the collector reservoir. As the bias window of the junction is opened wide enough to include one of the cluster frontier orbitals, the current blockade is lifted and charge carriers can tunnel sequentially across the junction.}, author = {Lovat, Giacomo and Choi, Bonnie and Paley, Daniel W. and Steigerwald, Michael L. and Venkataraman, Latha and Roy, Xavier}, issn = {1748-3395}, journal = {Nature Nanotechnology}, pages = {1050--1054}, publisher = {Springer Nature}, title = {{Room-temperature current blockade in atomically defined single-cluster junctions}}, doi = {10.1038/nnano.2017.156}, volume = {12}, year = {2017}, } @article{17939, abstract = {We report a series of single-molecule transport measurements carried out in an ionic environment with oligophenylenediamine wires. These molecules exhibit three discrete conducting states accessed by electrochemically modifying the contacts. Transport in these junctions is defined by the oligophenylene backbone, but the conductance is increased by factors of ∼20 and ∼400 when compared to traditional dative junctions. We propose that the higher-conducting states arise from in situ electrochemical conversion of the dative Au←N bond into a new type of Au–N contact. Density functional theory-based transport calculations establish that the new contacts dramatically increase the electronic coupling of the oligophenylene backbone to the Au electrodes, consistent with experimental transport data. The resulting contact resistance is the lowest reported to date; more generally, our work demonstrates a facile method for creating electronically transparent metal–organic interfaces.}, author = {Zang, Yaping and Pinkard, Andrew and Liu, Zhen-Fei and Neaton, Jeffrey B. and Steigerwald, Michael L. and Roy, Xavier and Venkataraman, Latha}, issn = {1520-5126}, journal = {Journal of the American Chemical Society}, number = {42}, pages = {14845--14848}, publisher = {American Chemical Society}, title = {{Electronically transparent Au–N bonds for molecular junctions}}, doi = {10.1021/jacs.7b08370}, volume = {139}, year = {2017}, } @article{17940, abstract = {Single-molecule conductance studies have traditionally focused on creating highly conducting molecular wires. However, progress in nanoscale electronics demands insulators just as it needs conductors. Here we describe the single-molecule length-dependent conductance properties of the classic silicon dioxide insulator. We synthesize molecular wires consisting of Si–O repeat units and measure their conductance through the scanning tunneling microscope-based break-junction method. These molecules yield conductance lower than alkanes of the same length and the largest length-dependent conductance decay of any molecular systems measured to date. We calculate single-molecule junction transmission and the complex band structure of the infinite 1D material for siloxane, in comparison with silane and alkane, and show that the large conductance decay is intrinsic to the nature of the Si–O bond. This work highlights the potential for siloxanes to function as molecular insulators in electronics.}, author = {Li, Haixing and Garner, Marc H. and Su, Timothy A. and Jensen, Anders and Inkpen, Michael S. and Steigerwald, Michael L. and Venkataraman, Latha and Solomon, Gemma C. and Nuckolls, Colin}, issn = {1520-5126}, journal = {Journal of the American Chemical Society}, number = {30}, pages = {10212--10215}, publisher = {American Chemical Society}, title = {{Extreme conductance suppression in molecular siloxanes}}, doi = {10.1021/jacs.7b05599}, volume = {139}, year = {2017}, } @article{17941, abstract = {How heteroatomic substitutions affect electron transport through π-conjugated hydrocarbons has been the subject of some debate. In this paper we investigate the effect of heteroatomic linkers in a molecular junction on the electron-transmission spectrum, focusing on the occurrence of quantum interference (QI) close to the Fermi level, where conductivity can be significantly suppressed. We find that the substitution or addition of heteroatoms to a carbon skeleton at the contact positions does not change the main feature of QI due to the underlying carbon skeleton. QI in the overall system thus remains a robust feature. This empirical observation leads us to derive, in two mathematical ways, that these findings can be generalized. We note that addition or substitution of a carbon atom by a heteroatom at the contact positions will increase or decrease the number of electrons in the π-system, which will lead to a change in the alignment of the molecular orbitals of the isolated system relative to the electrode Fermi level. Both Hückel and density functional theory calculations on model systems probe the effect of this Fermi level change and confirm qualitatively the implications of the underlying mathematical proofs.}, author = {Tsuji, Yuta and Stuyver, Thijs and Gunasekaran, Suman and Venkataraman, Latha}, issn = {1932-7455}, journal = {The Journal of Physical Chemistry C}, number = {27}, pages = {14451--14462}, publisher = {American Chemical Society}, title = {{The influence of linkers on quantum interference: A linker theorem}}, doi = {10.1021/acs.jpcc.7b03493}, volume = {121}, year = {2017}, } @article{17942, abstract = {Quantum interference effects, whether constructive or destructive, are key to predicting and understanding the electrical conductance of single molecules. Here, through theory and experiment, we investigate a family of benzene-like molecules that exhibit both constructive and destructive interference effects arising due to more than one contact between the molecule and each electrode. In particular, we demonstrate that the π-system of meta-coupled benzene can exhibit constructive interference and its para-coupled analog can exhibit destructive interference, and vice versa, depending on the specific through-space interactions. As a peculiarity, this allows a meta-coupled benzene molecule to exhibit higher conductance than a para-coupled benzene. Our results provide design principles for molecular electronic components with high sensitivity to through-space interactions and demonstrate that increasing the number of contacts between the molecule and electrodes can both increase and decrease the conductance.}, author = {Borges, Anders and Xia, Jianlong and Liu, Sheng Hua and Venkataraman, Latha and Solomon, Gemma C.}, issn = {1530-6992}, journal = {Nano Letters}, number = {7}, pages = {4436--4442}, publisher = {American Chemical Society}, title = {{The role of through-space interactions in modulating constructive and destructive interference effects in benzene}}, doi = {10.1021/acs.nanolett.7b01592}, volume = {17}, year = {2017}, } @article{17943, abstract = {This Account provides an overview of our recent efforts to uncover the fundamental charge transport properties of Si–Si and Ge–Ge single bonds and introduce useful functions into group 14 molecular wires. We utilize the tools of chemical synthesis and a scanning tunneling microscopy-based break-junction technique to study the mechanism of charge transport in these molecular systems. We evaluated the fundamental ability of silicon, germanium, and carbon molecular wires to transport charge by comparing conductances within families of well-defined structures, the members of which differ only in the number of Si (or Ge or C) atoms in the wire. For each family, this procedure yielded a length-dependent conductance decay parameter, β. Comparison of the different β values demonstrates that Si–Si and Ge–Ge σ bonds are more conductive than the analogous C–C σ bonds. These molecular trends mirror what is seen in the bulk. The conductance decay of Si and Ge-based wires is similar in magnitude to those from π-based molecular wires such as paraphenylenes However, the chemistry of the linkers that attach the molecular wires to the electrodes has a large influence on the resulting β value. For example, Si- and Ge-based wires of many different lengths connected with a methyl–thiomethyl linker give β values of 0.36–0.39 Å–1, whereas Si- and Ge-based wires connected with aryl–thiomethyl groups give drastically different β values for short and long wires. This observation inspired us to study molecular wires that are composed of both π- and σ-orbitals. The sequence and composition of group 14 atoms in the σ chain modulates the electronic coupling between the π end-groups and dictates the molecular conductance. The conductance behavior originates from the coupling between the subunits, which can be understood by considering periodic trends such as bond length, polarizability, and bond polarity. We found that the same periodic trends determine the electric field-induced breakdown properties of individual Si–Si, Ge–Ge, Si–O, Si–C, and C–C bonds. Building from these studies, we have prepared a system that has two different, alternative conductance pathways. In this wire, we can intentionally break a labile, strained silicon–silicon bond and thereby shunt the current through the secondary conduction pathway. This type of in situ bond-rupture provides a new tool to study single molecule reactions that are induced by electric fields. Moreover, these studies provide guidance for designing dielectric materials as well as molecular devices that require stability under high voltage bias. The fundamental studies on the structure/function relationships of the molecular wires have guided the design of new functional systems based on the Si- and Ge-based wires. For example, we exploited the principle of strain-induced Lewis acidity from reaction chemistry to design a single molecule switch that can be controllably switched between two conductive states by varying the distance between the tip and substrate electrodes. We found that the strain intrinsic to the disilaacenaphthene scaffold also creates two state conductance switching. Finally, we demonstrate the first example of a stereoelectronic conductance switch, and we demonstrate that the switching relies crucially on the electronic delocalization in Si–Si and Ge–Ge wire backbones. These studies illustrate the untapped potential in using Si- and Ge-based wires to design and control charge transport at the nanoscale and to allow quantum mechanics to be used as a tool to design ultraminiaturized switches.}, author = {Su, Timothy A. and Li, Haixing and Klausen, Rebekka S. and Kim, Nathaniel T. and Neupane, Madhav and Leighton, James L. and Steigerwald, Michael L. and Venkataraman, Latha and Nuckolls, Colin}, issn = {1520-4898}, journal = {Accounts of Chemical Research}, number = {4}, pages = {1088--1095}, publisher = {American Chemical Society}, title = {{Silane and Germane molecular electronics}}, doi = {10.1021/acs.accounts.7b00059}, volume = {50}, year = {2017}, } @article{17944, abstract = {The electronic, mechanical, and thermoelectric properties of molecular scale devices have fascinated scientists across several disciplines in natural sciences and engineering. The interest is partially technological, driven by the fast miniaturization of integrated circuits that now have reached characteristic features at the nanometer scale. Equally important, a very strong incentive also exists to elucidate the fundamental aspects of structure-function relations for nanoscale devices, which utilize molecular building blocks as functional units. Thus motivated, a rich research field has established itself, broadly termed “Molecular Electronics,” that hosts a plethora of activities devoted to this goal in chemistry, physics, and electrical engineering. This Special Topic on Frontiers of Molecular Scale Electronics captures recent theoretical and experimental advances in the field.}, author = {Evers, Ferdinand and Venkataraman, Latha}, issn = {1089-7690}, journal = {The Journal of Chemical Physics}, number = {9}, publisher = {AIP Publishing}, title = {{Preface: Special topic on Frontiers in Molecular Scale Electronics}}, doi = {10.1063/1.4977469}, volume = {146}, year = {2017}, } @article{17945, abstract = {We perform temperature dependent conductance measurements on sub-nanometer sized single molecules bound to gold electrodes using a scanning tunneling microscope-based break junction technique in Ultra-High Vacuum (UHV). We find a threefold increase in the conductance of amine-terminated conjugated molecules when the temperature increases from 4 K to 300 K in UHV. Furthermore, the conductance measured at 300 K in UHV is consistent with solution-based measurements under ambient conditions where the transport mechanism corresponds to off-resonant electron tunneling across the molecule. Our measurements indicate that at 300 K, conductance is largely independent of pressure or solvent around the junction. In addition, our data unambiguously show that temperature can affect the tunneling conductance of single molecule-metal junctions. We show that the structure of the metal electrodes that form in these junctions varies systematically with temperature, and hypothesize that this changing structure of the interface alters electron tunneling probability and propose a mechanism to explain our findings.}, author = {Kamenetska, M. and Widawsky, J. R. and Dell’Angela, M. and Frei, M. and Venkataraman, Latha}, issn = {1089-7690}, journal = {The Journal of Chemical Physics}, number = {9}, publisher = {AIP Publishing}, title = {{Temperature dependent tunneling conductance of single molecule junctions}}, doi = {10.1063/1.4973318}, volume = {146}, year = {2017}, } @article{17947, abstract = {We investigate light-induced conductance enhancement in single-molecule junctions via photon-assisted transport and hot-electron transport. Using 4,4′-bipyridine bound to Au electrodes as a prototypical single-molecule junction, we report a 20–40% enhancement in conductance under illumination with 980 nm wavelength radiation. We probe the effects of subtle changes in the transmission function on light-enhanced current and show that discrete variations in the binding geometry result in a 10% change in enhancement. Importantly, we prove theoretically that the steady-state behavior of photon-assisted transport and hot-electron transport is identical but that hot-electron transport is the dominant mechanism for optically induced conductance enhancement in single-molecule junctions when the wavelength used is absorbed by the electrodes and the hot-electron relaxation time is long. We confirm this experimentally by performing polarization-dependent conductance measurements of illuminated 4,4′-bipyridine junctions. Finally, we perform lock-in type measurements of optical current and conclude that currents due to laser-induced thermal expansion mask optical currents. This work provides a robust experimental framework for studying mechanisms of light-enhanced transport in single-molecule junctions and offers tools for tuning the performance of organic optoelectronic devices by analyzing detailed transport properties of the molecules involved.}, author = {Fung, E-Dean and Adak, Olgun and Lovat, Giacomo and Scarabelli, Diego and Venkataraman, Latha}, issn = {1530-6992}, journal = {Nano Letters}, number = {2}, pages = {1255--1261}, publisher = {American Chemical Society}, title = {{Too hot for photon-assisted transport: Hot-electrons dominate conductance enhancement in illuminated single-molecule junctions}}, doi = {10.1021/acs.nanolett.6b05091}, volume = {17}, year = {2017}, } @article{17949, abstract = {Single-molecule electronic devices provide researchers with an unprecedented ability to relate novel physical phenomena to molecular chemical structures. Typically, conjugated aromatic molecular backbones are relied upon to create electronic devices, where the aromaticity of the building blocks is used to enhance conductivity. We capitalize on the classical physical organic chemistry concept of Hückel antiaromaticity by demonstrating a single-molecule switch that exhibits low conductance in the neutral state and, upon electrochemical oxidation, reversibly switches to an antiaromatic high-conducting structure. We form single-molecule devices using the scanning tunneling microscope–based break-junction technique and observe an on/off ratio of ~70 for a thiophenylidene derivative that switches to an antiaromatic state with 6-4-6-π electrons. Through supporting nuclear magnetic resonance measurements, we show that the doubly oxidized core has antiaromatic character and we use density functional theory calculations to rationalize the origin of the high-conductance state for the oxidized single-molecule junction. Together, our work demonstrates how the concept of antiaromaticity can be exploited to create single-molecule devices that are highly conducting.}, author = {Yin, Xiaodong and Zang, Yaping and Zhu, Liangliang and Low, Jonathan Z. and Liu, Zhen-Fei and Cui, Jing and Neaton, Jeffrey B. and Venkataraman, Latha and Campos, Luis M.}, issn = {2375-2548}, journal = {Science Advances}, number = {10}, publisher = {American Association for the Advancement of Science}, title = {{A reversible single-molecule switch based on activated antiaromaticity}}, doi = {10.1126/sciadv.aao2615}, volume = {3}, year = {2017}, } @article{17950, abstract = {Whilst most studies in single-molecule electronics involve components first synthesized ex situ, there is also great potential in exploiting chemical transformations to prepare devices in situ. Here, as a first step towards this goal, we conduct reversible reactions on monolayers to make and break covalent bonds between alkanes of different lengths, then measure the conductance of these molecules connected between electrodes using the scanning tunneling microscopy-based break junction (STM-BJ) method. In doing so, we develop the critical methodology required for assembling and disassembling surface-bound single-molecule circuits. We identify effective reaction conditions for surface-bound reagents, and importantly demonstrate that the electronic characteristics of wires created in situ agree with those created ex situ. Finally, we show that the STM-BJ technique is unique in its ability to definitively probe surface reaction yields both on a local (∼50 nm2) and pseudo-global (≥10 mm2) level. This investigation thus highlights a route to the construction and integration of more complex, and ultimately functional, surface-based single-molecule circuitry, as well as advancing a methodology that facilitates studies beyond the reach of traditional ex situ synthetic approaches.}, author = {Inkpen, Michael S. and Leroux, Yann R. and Hapiot, Philippe and Campos, Luis M. and Venkataraman, Latha}, issn = {2041-6539}, journal = {Chemical Science}, number = {6}, pages = {4340--4346}, publisher = {Royal Society of Chemistry}, title = {{Reversible on-surface wiring of resistive circuits}}, doi = {10.1039/c7sc00599g}, volume = {8}, year = {2017}, } @article{17951, abstract = {Thiophene-1,1-dioxide (TDO) oligomers have fascinating electronic properties. We previously used thermopower measurements to show that a change in charge carrier from hole to electron occurs with increasing length of TDO oligomers when single-molecule junctions are formed between gold electrodes. In this article, we show for the first time that the dominant conducting orbitals for thiophene/TDO oligomers of fixed length can be tuned by altering the strength of the electron acceptors incorporated into the backbone. We use the scanning tunneling microscope break-junction (STM-BJ) technique and apply a recently developed method to determine the dominant transport channel in single-molecule junctions formed with these systems. Through these measurements, we find that increasing the electron affinity of thiophene derivatives, within a family of pentamers, changes the polarity of the charge carriers systematically from holes to electrons, with some systems even showing mid-gap transport characteristics.}, author = {Low, Jonathan Z. and Capozzi, Brian and Cui, Jing and Wei, Sujun and Venkataraman, Latha and Campos, Luis M.}, issn = {2041-6539}, journal = {Chemical Science}, number = {4}, pages = {3254--3259}, publisher = {Royal Society of Chemistry}, title = {{Tuning the polarity of charge carriers using electron deficient thiophenes}}, doi = {10.1039/c6sc05283e}, volume = {8}, year = {2017}, } @article{18198, abstract = {Higgs and Goldstone modes are collective excitations of the amplitude and phase of an order parameter that is related to the breaking of a continuous symmetry. We directly studied these modes in a supersolid quantum gas created by coupling a Bose-Einstein condensate to two optical cavities, whose field amplitudes form the real and imaginary parts of a U(1)-symmetric order parameter. Monitoring the cavity fields in real time allowed us to observe the dynamics of the associated Higgs and Goldstone modes and revealed their amplitude and phase nature. We used a spectroscopic method to measure their frequencies, and we gave a tunable mass to the Goldstone mode by exploring the crossover between continuous and discrete symmetry. Our experiments link spectroscopic measurements to the theoretical concept of Higgs and Goldstone modes.}, author = {Leonard, Julian and Morales, Andrea and Zupancic, Philip and Donner, Tobias and Esslinger, Tilman}, issn = {1095-9203}, journal = {Science}, number = {6369}, pages = {1415--1418}, publisher = {American Association for the Advancement of Science}, title = {{Monitoring and manipulating Higgs and Goldstone modes in a supersolid quantum gas}}, doi = {10.1126/science.aan2608}, volume = {358}, year = {2017}, }