A recyclable supramolecular membrane for size-selective separation of nanoparticles

Transcription

1 A recyclable supramolecular membrane for size-selective separation of nanoparticles E. Krieg, E. Shirman, H. Weissman, E. Shimoni, S. G. Wolf, I. Pinkas, B. Rybtchinski J. Am. Chem. Soc. 2009, 131, E. Krieg, H. Weissman, E. Shirman, E. Shimoni, B. Rybtchinski ature anotechnology 2011 DI: /A /A 274

2 Dr. Boris Rybtchinski 2002: PhD with Prof. D. Milstein, organometallic chemistry and catalysis (Weizmann Institute of Science, Rehovot, Israel) : Post-Doc with Prof. M. R. Wasielewski; Self-Assembly and rganic Photonics (orthwestern University, Evanston, Illinois, USA) Since 2005: Group Leader, rganic anostructures: Self-assembly and Photofunction, Weizmann Institute of Science

3 Dr. Boris Rybtchinski rganic anostructures Angew. Chem. Int. Ed.2009, 48,, J. Am. Chem. Soc. 2008,, 130, Hybrid anostructures J. Phys. Chem. B 2010, 114,

4 Electron Microscopy SEM (Scanning Electron microscopy) TEM (Transmission Electron Microscopy) In the SEM, a set of scan coils moves the electron beam In the TEM, the focused, monochromatic electron acrossthespecimenina2dimensional grid fashion. When beam interacts with and is transmitted through the the electron beam scans across the specimens, different sample, focused into an image and projected onto a interactions take place. These interactions are decoded with phosphor coated screen which emits visible light. The various detectors situated in the chamber above the specimen. Some electrons from the surface material are knocked out of their orbitals by the electron beam, and are called SECDARY ELECTRS. These electrons are detected by the secondary electron detector. Different interactions give images based on topography, elemental composition or density of the sample. A SEM can magnify up to about 100,000x. brighter areas of the image represent areas where more electronshavepassedthroughthesample.thedarker areas represent areas where fewer electrons have passed through as a result of higher specimen density. A TEM can magnify up to about 500,000x

5 Electron Microscopy TEM Electron beam passes through thin sample. Specially prepared p thin samples or particulate material are supported on TEM grids. Specimen stage halfway down column. Image shown on fluorescent screen. Image is a two dimensional projection of the sample. SEM Electron beam scans over surface of sample. Sample can be any thickness and is mounted on an aluminum stub. Specimen stage in the chamber at the bottom of the column. Image shown on TV monitor. Image is of the surface of the sample. E. coli bacteria original magnification X

6 Synthesis of PP2b H 2 imidazole, 140 C, 4h 79% Bromine, CH 2 Cl 2, 50 C, 24h 92% Br Br Br Br PEG 17 H, ah, CH 2 Cl 2, 2days 67% Br PEG 17 3 : 1 Pd 2 (All) 2 Cl 2, P(tBu) 3, DIPA 24h 63% PEG 17 PEG 17 Br Br a)[pd(pph 3 ) 2 Cl 2 ], CuI, THF, ipr 2 H, 20 C, 76% b) KF, MeH, 99%

7 Studies on PP2b aggregated solution Individual fibers: 5.9± 1.0 nm diameter Cryo-SEM image at 10-4 M in THF/water (80:20, v/v) Individual fibers: 72± 7.2± nm diameter Cryo-TEM image at 10-4 M in THF/water (80:20, v/v) a) ) Filtration experiment. b-d) Mixing experiment. The pictures are taken after (b) 1 min, (c) 6 h, and (d) 4 days. Gel-like 3D supramolecular networks

8 Studies on PP2b supramolecular gel Above cgc= 6 x 10-3 M, PP2b forms gel between 10 to 20 vol% THF ±1.1 1 nm in diameter Schematic illustration of the PP2b assembly hierarchy. Cryo-SEM images of the gel of PP2b ( M, water/thf mixture (80:20)) at different magnifications. (c) Whirls with diameters of μm. (d) Directional arrangement of fibers within a microstream in the gel.

9 Responsiveness of PP2b supramolecular gel Effect of reversible charging of the gel in water/thf mixture (85:15, v/v). (a) Inverted tubes of the gel ( M) before reduction, after reduction with 1 equiv of a 2 S 2 4, and after oxidation back to the neutral state using air. (b) Polarized light microscopic images of the corresponding samples. (c) UV/vis spectra of aggregated solutions of PP2b (10-4 M) in water/thf mixture (80:20, v/v) before reduction (red), after reduction (black), and after exposing the reduced sample to air (blue). Inset: EPR spectrum of neutral (red) and reduced form (black). Reversible switching between swollen gel, shrunken gel, and solution by exploiting response to temperature and reversible charging.

10 Supramolecular filtration membrane 12µm a, Photograph showing the preparation of the membrane by filtration of a supramolecular solution of PP2b ( M) in water over a CA filter (pore size, 0.45 mm) c, Cryo-SEM image of the cross-section of a 1 1 mm piece of the supramolecular membrane (0.65 mg PP2b cm -2 ) on the CA support. d, Magnified image showing the sharp border between the coarse CA and the smooth PP2b layer (dashed line). e, High-magnification image of the supramolecular PP2b layer.

11 Supramolecular filtration membrane Stable flow rates at pressures up to 0.7bar Flow rate at 0.4bar comparable to commercial ultrafiltration membrane Complete removal from the CA support using a water/ethanol mixture (4:6, v/v)

12 Filtration of gold nanoparticles Au3 h, UV/Vis spectra of the Au3 solution before filtration (black trace), retentate (red trace) and filtrate (blue trace). i, Photographs showing the retrieval of PP2b and gold nanoparticles from the water/ethanol mixture. Au3: Mercaptopropionic-acid stabilized gold nanoparticles