NIRT: Controlling Interfacial Activity of Nanoparticles: Robust Routes to Nanoparticle- based Capsules, Membranes, and Electronic Materials (CBET ) 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 Sulfonated poly(arylene ether sulfone) (BPS) BPS-XY series, X = mol% of disulfonated monomer (0<X<100), Y = “H” (free acid form) or “N” (sodium salt form). TiO 2 nanoparticles: Average particle diameter: 10 nm Density 3.9 g/cm 3 Morphology: Spherical Hydrophilic part Hydrophobic part Materials for nanocomposite films SEM and NaCl permeability of nano-composite films FilmTiO 2 wt%(%)Dry Temperature (C)Film Thickness (μm)NaCl Permeability (cm 2 /s) BPS-30N E-10 TiO2-BPS30N E-10 TiO2-BPS30N E-10 TiO2-BPS30N E-10 TiO2-BPS30N E-10 TiO2-BPS30N E-10 TiO2-BPS30N E-10 Air-side surface of films Glass-side surface of films Cross-section of films Objectives: Harness the interfacial activity of nanoparticles, and the reactivity of functionalized ligands, for the preparation of robust, self-assembled structures, devices, and membranes TCB Water 20  m 80  m Droplet resizing through track-etch membranes Confocal images reduction in droplet size from 200  m to 10  m and less H 2 O interior Oil phase Nanoparticle Assembly 20µm Fluorescence confocal images of quantum dots on water droplets in a continuous oil phase TOPO-covered CdSe quantum dots z/R E(z)/kT Oil Water E min Pieranski, P. Phys. Rev. Lett 45, 569 (1980) Interfacial assembly of nanoparticles: droplets and sheets Lin, Y., Skaff, H., Emrick, T., Dinsmore, A. D. & Russell, T. P., Science 299, Interfacial energy well: Nanocomposite membranes: exploratory materials for water purification Responsive Nanocomposites: using ligands to direct nanoparticles to polymer domains and interfacial boudaries 50 nm 100 nm 25% OH terminated: NPs segregate to PS-PVP interface 50% OH terminated: NPs distributed within PVP domain OH HO Lamellar morphology (solvent annealed films) with avg. 2.4 nm Au NPs avg. 4.5 nm diameter Au NPs Nanoparticle ripening + entropic penalty = reorganization Thermal annealing 170 deg C Idealized schematic of responsive nanocomposite Diblock copolymer host: polystyrene-poly(4-vinylpyridine) Effect on mechanical properties?? Electronically active assemblies TEM: 5-nm Au on Ga 50 nm PEGylated gold nanoparticles stabilize Ga droplets for days Gallium droplets in HCl coalesce instantly Dry on substrate, image with TEM Ga + HCl + nano-Au with C 11 -TEG ligands Sonicate at 40 o C (above T m ) compare to… Ga droplet (conductor) Ga droplet A 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, (‘01)]) Potential for large-scale production of devices by self-assembly. 1  m V A V Gallium droplet Ga drop coated with monolayer of 5-nm Au particles in suspension (Ligand: HS-C 11 H 22 [ O-CH 2 -CH 2 ] 4 OH) Deposited on substrate with gold microfab leads; washed & dried. Current-voltage curve shows Coulomb blockade effect: V threshold ~ 0.2 V, consistent with having 2 junctions in series. [A. J. Quinn and G. Redmond, Surf. Sci. 601, 2740 (2007). Repeatable: 16 I-V curves on this sample; several other samples with similar results. Next: Apply insulating coating and gate electrodes.