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Amherst, MA, United States

Selhorst R.C.,20 Governors Drive | Puodziukynaite E.,20 Governors Drive | Dewey J.A.,20 Governors Drive | Wang P.,University of Massachusetts Amherst | And 3 more authors.
Chemical Science

Transition metal dichalcogenides (TMDCs) such as MoS2 comprise an important class of 2D semiconductors with numerous interesting electronic and mechanical features. Full utilization of TMDCs in materials and devices, however, necessitates robust functionalization methods. We report well-defined tetrathiafulvalene (TTF)-based polymers, exploiting synthetic routes that overcome challenges previously associated with these systems. These platforms enable basal plane coordinative interactions with MoS2, conceptually in parallel with pyrene-containing platforms for graphene and carbon nanotube modification. Not yet reported for TMDCs, these non-covalent interactions are universal and effective for MoS2 irrespective of the lattice structure, affording significantly enhanced solution stabilization of the nanosheets. Additionally, the TTF-functionalized polymers offer electronic structure modulation of MoS2 by ground state charge transfer and work function reduction, demonstrated using Kelvin probe force microscopy (KPFM). Notably, coordination and electronic effects are amplified for the TTF-polymers over TTF itself. Experiments are supported by first-principles density functional theory (DFT) calculations that probe polymer-TTF surface interactions with MoS2 and the resultant impact on electronic properties. © The Royal Society of Chemistry 2016. Source

Pham J.T.,20 Governors Drive | Lawrence J.,20 Governors Drive | Grason G.M.,20 Governors Drive | Emrick T.,20 Governors Drive | Crosby A.J.,20 Governors Drive
Physical Chemistry Chemical Physics

Hybrid materials that possess high inorganic fractions of nanoscale particles can be advantageous for a wide range of functions, from optoelectronic or electronic devices to drug delivery. However, many current nanoparticle (NP) based materials lack the necessary combination of simple fabrication and robust mechanical properties that span across length scales greater than tens of microns. We have developed a facile, evaporative assembly method called flow coating to create NP based ribbons that can subsequently form helical structures. Here we analytically examine the stretching properties of these helical ribbons which are nanometers thick, microns wide, and arbitrarily long. We find that the force-extension behavior is well described by the elastic and surface energies, which can be used as a guideline for their design. In addition, we show that the properties may be tuned by changing the ribbon dimensions or material composition to yield a different stiffness. These macroscale mechanical properties, along with properties inherent to the nanometer length scale of the particles can provide tunable multifunctionality for a number of applications. This journal is © the Partner Organisations 2014. Source

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