NIRT Controlling Interfacial Activity of Nanoparticles Robust Routes
NIRT: Controlling Interfacial Activity of Nanoparticles: Robust Routes to Nanoparticlebased Capsules, Membranes, and Electronic Materials (CBET 0609107) Todd Emrick and Thomas P Russell, Polymer Science & Engineering Department, University of Massachusetts Amherst Anthony Dinsmore and Narayanan Menon, Physics Department, University of Massachusetts Amherst Benny D. Freeman, Chemical Engineering Department, University of Texas at Austin Objectives: Harness the interfacial activity of nanoparticles, and the reactivity of functionalized ligands, for the preparation of robust, self-assembled structures , devices, and membranes Interfacial assembly of nanoparticles: droplets and sheets Pieranski, P. Phys. Rev. Lett 45, 569 (1980) Responsive Nanocomposites: using ligands to direct nanoparticles to polymer domains and interfacial boudaries E(z)/k. T Water Nanoparticle Assembly Oil phase Idealized schematic of responsive nanocomposite H 2 O Thermal annealing interior Oil Emin z/R 20µm TOPO-covered Cd. Se quantum dots Fluorescence confocal images of quantum dots on water droplets in a continuous oil phase Effect on mechanical properties? ? Lin, Y. , Skaff, H. , Emrick, T. , Dinsmore, A. D. & Russell, T. P. , Science 299, 226 -229. Interfacial energy well: OH Droplet resizing through track-etch membranes Confocal images reduction in droplet size from 200 mm to 10 mm and less TCB OH HO 50% OH terminated: NPs distributed within PVP domain 25% OH terminated: NPs segregate to PS-PVP interface Water 170 deg C Nanoparticle ripening + entropic penalty = reorganization 50 nm 100 nm Diblock copolymer host: polystyrene-poly(4 -vinylpyridine) avg. 4. 5 nm diameter Au NPs Lamellar morphology (solvent annealed films) with avg. 2. 4 nm Au NPs 80 mm 20 mm Electronically active assemblies Nanocomposite membranes: exploratory materials for water purification Gallium droplets in HCl coalesce instantly PEGylated gold nanoparticles stabilize Ga droplets for days suspension (Ligand: HS-C 11 H 22 [ O-CH 2 ]4 OH) compare to… SEM and Na. Cl permeability of nano-composite films Materials for nanocomposite films Deposited on substrate with gold microfab leads; washed & dried. Current-voltage curve shows Coulomb blockade effect: Vthreshold ~ 0. 2 V, consistent with having 2 junctions in series. [A. J. Quinn and G. Redmond, Surf. Sci. 601, 2740 (2007). TEM: 5 -nm Au on Ga Sulfonated poly(arylene ether sulfone) (BPS) Dry on substrate, image with TEM BPS-XY series, X = mol% of disulfonated monomer (0<X<100), Y = “H” (free acid form) or “N” (sodium salt form). Glass-side surface of films Air-side surface of films 50 nm Ti. O 2 wt%(%) Dry Temperature (C) Film Thickness (μm) Na. Cl Permeability (cm 2/s) BPS-30 N 0 80 20. 4 3. 71 E-10 Ti. O 2 -BPS 30 N 20 60 32. 1 6. 74 E-10 Ti. O 2 -BPS 30 N 20 80 21. 4 3. 92 E-10 Ti. O 2 -BPS 30 N 45 80 36. 6 8. 53 E-10 Ti. O 2 -BPS 30 N 20 100 21. 7 4. 08 E-10 Ti. O 2 -BPS 30 N 20 110 23. 9 5. 49 E-10 Ti. O 2 -BPS 30 N 20 130 15. 2 3. 63 E-10 Hydrophilic part Ti. O 2 nanoparticles: Average particle diameter: 10 nm Density 3. 9 g/cm 3 Morphology: Spherical Hydrophobic part Repeatable: 16 I-V curves on this sample; several other samples with similar results. Next: Apply insulating coating and gate electrodes. Cross-section of films Film Ga + HCl + nano-Au with C 11 -TEG ligands Sonicate at 40 o. C (above Tm) Ga drop coated with monolayer of 5 -nm Au particles in 1 mm V A Gallium droplet V A Ga droplet (conductor) V 1 mm Ga droplets make good contact to layer of Au NPs (no nm-resolution lithography needed) Current limited by tunneling across Au NPs (Coulomb blockade; quantitative agreement w/ prior experiments using lithographically-defined electrodes [Klein et al. , APL 68, 2574 (‘ 96); Wang et al. PRB 63, 035403 (‘ 01)]) Potential for large-scale production of devices by self-assembly.
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