This paper describes a strategy for functionalizing graphite and carbon nanotube surfaces with multilayered polymeric films. Poly(amphiphiles) adsorb noncovalently onto these surfaces from aqueous solutions, due to hydrophobic interactions. The covalent attachment of a second polymer layer to this initial adsorbed layer results in the formation of a cross-linked polymer bilayer; additional layers can be deposited by the covalent or electrostatic attachment of polyelectrolytes. We used these multilayered polymer films to mediate the attachment of gold nanoparticles to graphite, single-walled nanotube (SWNT), and multiwalled nanotube (MWNT) surfaces. This approach provides a convenient method for attaching other nanostructures, biological molecules, or ligands to carbon nanotubes.

Cu interconnect technology requires the use of Ͻ5-nm-thick interfacial layers to inhibit Cu transport into adjacent dielectric layers. We demonstrate the use of 3.5-nm-thick polyelectrolyte layers comprising polyethyleneimine ͑PEI͒ and polyacrylic acid ͑PAA͒ for this application. Cu/PAA/PEI/SiO 2 /Si structures show more than a factor-of-5 greater failure time compared to that observed in Cu/SiO 2 /Si structures. Increasing the number of PAA/PEI bilayers does not show any further improvement in barrier properties. Spectroscopic probing of the Cu/PAA interface reveals that polychelation of Cu with carboxyl groups in PAA is the primary reason for Cu immobilization. Our study suggests that polyelectrolyte nanolayers are attractive for applications such as tailoring barrierless low-k polymeric dielectrics, and for isolating nanoscale components in future device systems.

Mimicking trimeric interactions in the aromatic side chains of the proteins: A gas phase study of indole…(pyrrole)2 heterotrimer JCP: BioChem. Phys. 6, 05B601 (2012) Mimicking trimeric interactions in the aromatic side chains of the proteins: A gas phase study of indole…(pyrrole)2 heterotrimer J. Chem. Phys. 136, 174302 (2012) Ligand migration in myoglobin: A combined study of computer simulation and x-ray crystallography JCP: BioChem. Phys. 6, 04B620 (2012) Ligand migration in myoglobin: A combined study of computer simulation and x-ray crystallography J. Chem. Phys. 136, 165101 (2012) Deoxycholate induced tetramer of αA-crystallin and sites of phosphorylation: Fluorescence correlation spectroscopy and femtosecond solvation dynamics JCP: BioChem. Phys. 6, 04B614 (2012) Additional information on J. Appl. Phys. Whispering gallery mode (WGM) optical biosensors are capable of extraordinarily sensitive specific and nonspecific detection of species suspended in a gas or fluid. Recent experimental results suggest that these devices may attain single-molecule sensitivity to protein solutions in the form of stepwise shifts in their resonance wavelength, k R , but present sensor models predict much smaller steps than were reported. This study examines the physical interaction between a WGM sensor and a molecule adsorbed to its surface, exploring assumptions made in previous efforts to model WGM sensor behavior, and describing computational schemes that model the experiments for which single protein sensitivity was reported. The resulting model is used to simulate sensor performance, within constraints imposed by the limited material property data. On this basis, we conclude that nonlinear optical effects would be needed to attain the reported sensitivity, and that, in the experiments for which extreme sensitivity was reported, a bound protein experiences optical energy fluxes too high for such effects to be ignored. V C 2012 American Institute of Physics.

Whispering gallery mode (WGM) optical resonator sensors are an extremely sensitive label-free technology for detecting the binding of biomolecules in solution. To better understand the fast transient response observed with these devices, we model mass transfer to spherical and toroidal WGM sensors of identical outer radius. Finite element simulations predict a 3-10 fold higher binding frequency for toroidal sensors. These results agree to within an order of magnitude with experimental data from the literature and suggest a design strategy to improve the transient response of a sensor by making the device small only in the dimension that governs boundary layer development.