Jiping Yang

Bio: Jiping Yang is an academic researcher from Rice University. The author has contributed to research in topics: Selective chemistry of single-walled nanotubes & Carbon nanobud. The author has an hindex of 10, co-authored 14 publications receiving 2130 citations. Previous affiliations of Jiping Yang include University of Texas at Austin.

Functionalization of carbon nanotubes by electrochemical reduction of aryl diazonium salts: a bucky paper electrode

Abstract: Small-diameter (ca. 0.7 nm) single-wall carbon nanotubes are predicted to display enhanced reactivity relative to larger-diameter nanotubes due to increased curvature strain. The derivatization of these small-diameter nanotubes via electrochemical reduction of a variety of aryl diazonium salts is described. The estimated degree of functionalization is as high as one out of every 20 carbons in the nanotubes bearing a functionalized moiety. The functionalizing moieties can be removed by heating in an argon atmosphere. Nanotubes derivatized with a 4-tert-butylbenzene moiety were found to possess significantly improved solubility in organic solvents. Functionalization of the nanotubes with a molecular system that has exhibited switching and memory behavior is shown. This represents the marriage of wire-like nanotubes with molecular electronic devices.

Charge transport through self-assembled monolayers of compounds of interest in molecular electronics.

Abstract: The electrical properties of self-assembled monolayers (SAMs) on metal surfaces have been explored for a series of molecules to address the relation between the behavior of a molecule and its structure. We probed interfacial electron transfer processes, particularly those involving unoccupied states, of SAMs of thiolates or arylates on Au by using shear force-based scanning probe microscopy (SPM) combined with current−voltage (i − V) and current−distance (i − d) measurements. The i − V curves of hexadecanethiol in the low bias regime were symmetric around 0 V and the current increased exponentially with V at high bias voltage. Different than hexadecanethiol, reversible peak-shaped i − V characteristics were obtained for most of the nitro-based oligo(phenylene ethynylene) SAMs studied here, indicating that part of the conduction mechanism of these junctions involved resonance tunneling. These reversible peaked i − V curves, often described as a negative differential resistance (NDR) effect of the junction,...

Process for derivatizing carbon nanotubes with diazonium species and compositions thereof

Abstract: The invention incorporates new processes for the chemical modification of carbon nanotubes. Such processes involve the derivatization of multi- and single-wall carbon nanotubes, including small diameter (ca. 0.7 nm) single-wall carbon nanotubes, with diazonium species. The method allows the chemical attachment of a variety of organic compounds to the side and ends of carbon nanotubes. These chemically modified nanotubes have applications in polymer composite materials, molecular electronic applications and sensor devices. The methods of derivatization include electrochemical induced reactions thermally induced reactions (via in-situ generation of diazonium compounds or pre-formed diazonium compounds), and photochemically induced reactions. The derivatization causes significant changes in the spectroscopic properties of the nanotubes. The estimated degree of functionality is ca. 1 out of every 20 to 30 carbons in a nanotube bearing a functionality moiety. Such electrochemical reduction processes can be adapted to apply site-selective chemical functionalization of nanotubes. Moreover, when modified with suitable chemical groups, the derivatized nanotubes are chemically compatible with a polymer matrix, allowing transfer of the properties of the nanotubes (such as, mechanical strength or electrical conductivity) to the properties of the composite material as a whole. Furthermore, when modified with suitable chemical groups, the groups can be polymerized to form a polymer that includes carbon nanotubes.

Chemical and Potential-Assisted Assembly of Thiolacetyl-Terminated Oligo(phenylene ethynylene)s on Gold Surfaces

Abstract: Reliable and reproducible methods have been developed for the formation of self-assembled monolayers (SAMs) of thiolacetyl-terminated oligo(phenylene ethynylene)s on a Au surface. The thiolacetyl g...

Determination of the molecular electrical properties of self-assembled monolayers of compounds of interest in molecular electronics.

Abstract: In this communication we report preliminary results with a tuning fork-based scanning probe technique combined with current-voltage (i-V) measurements, for the rapid characterization and screening of monolayer films in an inert atmosphere. We studied self-assembled monolayers (SAMs) of a variety of molecules with different structures that are being considered for possible application in molecular electronic devices and devised a high throughput analysis method for their characterization. There is currently a high level of interest in the electrical properties of isolated molecules especially in the use of unconventional substances and single molecules or SAMs to construct electronic devices.1-3 Advances in synthetic supramolecular chemistry, coupled with recent developments in device fabrication techniques and scanning probe techniques,4 allow single molecules to be manipulated and investigated electronically. Synthetic chemistry is mature enough to offer a huge range of molecular structures with different properties. A challenge has been to develop reliable and fast screening methods to characterize electronic properties of molecules and to be able to correlate the electrical behavior of the molecules with their structure. A few initial efforts have used long molecular wires across lithographically patterned proximal gold-coated probes separated by approximately 10 nm, but these studies were unreliable and not suitable for molecules shorter than the array gap.1,3 The Langmuir-Blodgett technique was also used to prepare a single molecular layer which was sandwiched between Al and Ti/Al contacts to form a device.5 Other efforts employed a nanopore arrangement or mechanically controllable break junctions6 where electronic measurements were performed between adjustable proximal point contacts. Still others have been performed in nanopores on a structure7 that has a metal top contact formed by vacuum evaporation, an active SAM, and a metal bottom contact. These techniques have provided interesting results, but the preparation of such nanostructures is time-consuming and fabrication-intensive. An attractive approach is to utilize a conducting atomic force microscope (AFM) tip8 as one of the contacts to form a metal-molecule-metal junction. We show here that a tuning fork-based scanning probe microscope (SPM)9 for rapid probe positioning combined with i-V measurements can be used to characterize and screen a large variety of molecules with different electrical properties. In the work reported here the molecules of interest were assembled on a flat gold substrate and then studied by this technique in a controlled environment. The basic principle of the device is illustrated in Figure 1. The tip, sharpened by electrochemical etching, as used for STM tips, is attached to a small tuning fork. The tuning fork is excited by an attached piezoelectric element, generally oscillating in the region of 33 to 100 kHz, and is used for rapid approach of the tip to the SAM. When the tip just contacts the SAM surface, the amplitude and frequency of the oscillation decrease, and this can be used to sense the presence of a surface. This same technique is used with many near-field scanning optical microscopy (NSOM) instruments to maintain tip position. Thus, the tip can be moved to the substrate and positioned fairly rapidly. The tip is then retracted slightly (about 10 nm) and moved to a different location on the SAM. The potential of the tip is swept with respect to the substrate over the desired potential range, and the current is recorded, as the tip is again approached toward the SAM, this time in small steps (e.g., 2 A). Before the tip contacts the molecules in the SAM, essentially no current flows. Upon contact, when the potential across the SAM containing electron-donating or electronwithdrawing groups attains a characteristic bias voltage, a current flows through the film. The magnitude of the current that flows in the i-V curve is a function of the conductance of the molecules. The synthesis of the compounds reported here and the preparation and characterization of the SAM have been described elsewhere10,11 (see Supporting Information). The i-V measurements were made in an argon atmosphere on seven compounds (Table 1).12 Figure 2 shows typical i-V characteristics of compounds I, II, and IV when the tip first contacts the surface of a SAM. For the alkylthiol (I) only the expected tunneling behavior at biases beyond about (4.8 V is seen (Figure 2A). Figure 2B shows the i-V curve of a SAM of 2′-ethyl-4,4′bis(phenylethynyl)-1-benzenethiolate (II) on gold. When the negative scan reaches about 2.8 V, a peaked current response of a few pA is observed. This type of response has been observed previously in similar studies with nanopore junctions and has been † The University of Texas at Austin. ‡ Rice University. (1) Tour, J. M. Acc. Chem. Res. 2000, in press. (2) Jortner, J.; Ratner, M. Molecular Electronics; Blackwell: London, 1997. (3) Metzger, R. M. Acc. Chem. Res. 1999, 32, 950. (4) See, e.g.: (a) Cygan, M. T.; Dunbar, T. D.; Arnold, J. J.; Bumm, L. A.; Shedlock, N. F.; Burgin, T. P.; Jones, L., II; Allara, D. L.; Tour, J. M.; Weiss, P. S. J. Am. Chem. Soc. 1998, 120, 2721. (b) Semaltianos, N. G. Chem. Phys. Lett. 2000, 329, 76. (5) (a) Collier, C. P.; Wong, E. W.; Beloradsky, M.; Raymo, F. M.; Stoddart, J. F.; Kuekes, P. J.; Williams, R. S.; Heath, J. R. Science 1999, 285, 391. (b) Wong, E. W.; Collier, C. P.; Beloradsky, M.; Raymo, F. M.; Stoddart, J. F.; Heath, J. R. J. Am. Chem. Soc. 2000, 122, 5831. (6) Reed, M. A.; Zhou, C.; Muller, C. J.; Burgin, T. P.; Tour, J. M. Science 1997, 278, 252. (7) Chen, J.; Reed, M. A.; Rawlett, A. M.; Tour, J. M. Science 1999, 286, 1550. (8) (a) Wold, D. J.; Frisbie, C. D. J. Am. Chem. Soc. 2000, 122, 2970. (b) Kelley, T. W.; Granstrom, E. L.; Frisbie, C. D. AdV. Mater. 1999, 11, 261. (c) Dai, H.; Wong, E. W.; Lieber, C. M. Science 1996, 272, 523. (d) Alpersion, B.; Cohen, S.; Rubinstein, I.; Hodes, G. Phys. ReV. B 1995, 52, R17017. (e) Klein, D.; McEuen, P. Appl. Phys. Lett. 1995, 66, 2478. (9) Karrai, K.; Grober, R. D. Appl. Phys. Lett. 1995, 66, 1842. (10) Chen, J.; Wang, W.; Reed, M. A.; Rawlett, A. M.; Price, D. W.; Tour, J. M. Appl. Phys. Lett. 2000, 77, 1224. (11) Kosynkin, D.; Tour, J. M. Org. Lett., submitted for publication. (12) The number of molecules contacting the tip estimated from the tip radius (∼5 nm), the van der Waals radius (∼ 0.35 nm) of the molecules for a deformation depth of 0.2 nm of the SAM was about 35. Figure 1. Schematic representation of the measurement and formation of the metal-molecule-metal junction with a tuning fork-based SPM tip contacting the SAM on Au (not to scale). Ar atmosphere. 2454 J. Am. Chem. Soc. 2001, 123, 2454-2455

Chemistry of Carbon Nanotubes

Abstract: Department of Materials Science, University of Patras, 26504 Rio Patras, Greece, Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation, 48 Vass. Constantinou Avenue, 116 35 Athens, Greece, Institut de Biologie Moleculaire et Cellulaire, UPR9021 CNRS, Immunologie et Chimie Therapeutiques, 67084 Strasbourg, France, and Dipartimento di Scienze Farmaceutiche, Universita di Trieste, Piazzale Europa 1, 34127 Trieste, Italy

Graphene/Polymer Nanocomposites

Abstract: Graphene has emerged as a subject of enormous scientific interest due to its exceptional electron transport, mechanical properties, and high surface area. When incorporated appropriately, these atomically thin carbon sheets can significantly improve physical properties of host polymers at extremely small loading. We first review production routes to exfoliated graphite with an emphasis on top-down strategies starting from graphite oxide, including advantages and disadvantages of each method. Then solvent- and melt-based strategies to disperse chemically or thermally reduced graphene oxide in polymers are discussed. Analytical techniques for characterizing particle dimensions, surface characteristics, and dispersion in matrix polymers are also introduced. We summarize electrical, thermal, mechanical, and gas barrier properties of the graphene/polymer nanocomposites. We conclude this review listing current challenges associated with processing and scalability of graphene composites and future perspectives f...

Advances in molecular quantum chemistry contained in the Q-Chem 4 program package

Abstract: A summary of the technical advances that are incorporated in the fourth major release of the Q-Chem quantum chemistry program is provided, covering approximately the last seven years. These include developments in density functional theory methods and algorithms, nuclear magnetic resonance (NMR) property evaluation, coupled cluster and perturbation theories, methods for electronically excited and open-shell species, tools for treating extended environments, algorithms for walking on potential surfaces, analysis tools, energy and electron transfer modelling, parallel computing capabilities, and graphical user interfaces. In addition, a selection of example case studies that illustrate these capabilities is given. These include extensive benchmarks of the comparative accuracy of modern density functionals for bonded and non-bonded interactions, tests of attenuated second order Moller–Plesset (MP2) methods for intermolecular interactions, a variety of parallel performance benchmarks, and tests of the accuracy of implicit solvation models. Some specific chemical examples include calculations on the strongly correlated Cr_2 dimer, exploring zeolite-catalysed ethane dehydrogenation, energy decomposition analysis of a charged ter-molecular complex arising from glycerol photoionisation, and natural transition orbitals for a Frenkel exciton state in a nine-unit model of a self-assembling nanotube.

Emerging Transparent Electrodes Based on Thin Films of Carbon Nanotubes, Graphene, and Metallic Nanostructures

Abstract: Transparent electrodes are a necessary component in many modern devices such as touch screens, LCDs, OLEDs, and solar cells, all of which are growing in demand. Traditionally, this role has been well served by doped metal oxides, the most common of which is indium tin oxide, or ITO. Recently, advances in nano-materials research have opened the door for other transparent conductive materials, each with unique properties. These include CNTs, graphene, metal nanowires, and printable metal grids. This review will explore the materials properties of transparent conductors, covering traditional metal oxides and conductive polymers initially, but with a focus on current developments in nano-material coatings. Electronic, optical, and mechanical properties of each material will be discussed, as well as suitability for various applications.

RESEARCH ARTICLE Advances in molecular quantum chemistry contained in the Q-Chem 4 program package

Abstract: A summary of the technical advances that are incorporated in the fourth major release of the Q-Chem quantum chemistry program is provided, covering approximately the last seven years. These include developments in density functional theory methods and algorithms, nuclear magnetic resonance (NMR) property evaluation, coupled cluster and perturbation theories, methods for electronically excited and open-shell species, tools for treating extended environments, algorithms for walking on potential surfaces, analysis tools, energy and electron transfer modelling, parallel computing capabilities, and graphical user interfaces. In addition, a selection of example case studies that illustrate these capabilities is given. These include extensive benchmarks of the comparative accuracy of modern density functionals for bonded and non-bonded interactions, tests of attenuated second order Møller–Plesset (MP2) methods for intermolecular interactions, a variety of parallel performance benchmarks, and tests of the accuracy of implicit solvation models. Some specific chemical examples include calculations on the strongly correlated Cr2 dimer, exploring zeolite-catalysed ethane dehydrogenation, energy decomposition analysis of a charged ter-molecular complex arising from glycerol photoionisation, and natural transition orbitals for a Frenkel exciton state in a nine-unit model of a self-assembling nanotube.