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 Objectives: Harness the interfacial activity of nanoparticles, and the reactivity of functionalized ligands, for the preparation of robust, self-assembled structures, devices, and membranes Materials for nano-composite films Responsive Nanocomposites: using ligands to direct nanoparticles to polymer domains and interfacial boundaries Thermal annealing Idealized schematic of responsive nanocomposite Effect on mechanical properties?? 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 170 deg C Diblock copolymer host: polystyrene-poly(4-vinylpyridine) Self-assembled nanorods and bionanorods using fluid interfaces 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 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 Lin, Y., Skaff, H., Emrick, T., Dinsmore, A. D. & Russell, T. P., Science 299, Interfacial energy well: The structure and orientation of nanorods at the liquid-liquid interface can be manipulated by varying nanorod concentration in the bulk. At low TMV concentration, the rods orient parallel to the interface, which maximizes interfacial stabilizaiton. At high TMV concentrations, the rods orient normal to the interface, both mediating the interfacial interactions and neutralizing inter-rod electrostatic repulsion. For charged nanorods like TMV, repulsive forces dominate the oil-water interfaces, which is strongly affected by the ionic strength, but not the pH, of the bulk solution in the range of pH = 6~8. Removal of the buffer solution leads to cleavage of the TMV nanorods at the oil/water interface. Au nanoparticles: EG4-058A Citrate-stabilized gold nanoparticles in water ~20 nm in diameter ~1 mg/ml in water Di-sulfonated poly(arylene ether sulfone) (BPS): BPS-XY series, X = mol% of disulfonated monomer (0<X<100), Y = “H” (free acid form), “N” (sodium salt form), or “K” (potassium salt form). Acid/base tolerance: steady water permeability and salt rejection over a wide range of pH 1.Measured in cross-flow cells. Feed solution: 2000 ppm NaCl, pressure = 27.2 atm (400 psig), flow rate = 1 gpm, temperature = 25oC. 2. BPS-32K/0.5%Au: BPS-32K with 0.5 wt% of Au nanoparticles (EG4-058A) Binding energy of nanoparticles at oil-water interface Nanoparticle binding energy (  E) is measured from the change of interfacial tension as particles adsorb on a droplet. This data is for citrate-stabilized gold nanoparticles assembling on a droplet of octafluoropentylacrylate. We find  E ~ R2 (R is the nanoparticle radius), as predicted from a continuum-scale model [Pieranski, PRL 45, 569 (1980)]. We also find that  E can be increased by adding salt or by using ethylene glycol polymer ligands. These data provide the first measurements of  E for nanoparticles at oil-water interfaces, and guide the design and fabrication of new materials via interfacial assembly.