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Roy Shenhar

Institute of Chemistry
Faculty of Science
The Hebrew University, Jerusalem 91904, Israel
Tel: +972-2-6586 311; Fax: +972-2-6585 345
E-mail: roy.shenhar@mail.huji.ac.il;
Website: http://chem.ch.huji.ac.il/~roys/

Block copolymer nanotechnology

Research in the Shenhar group focuses on studying materials that are organized on the nanometer scale. We specialize in ?block co-polymers? ? a family of chain-like molecules containing two types of ?beads? organized in sequences (such as AAAAAAAAAAAAA-BBBBBBBBBBBBBBBB). These materials are available in a variety of compositions and chain lengths. When we create very thin films of these materials, periodic structures spontaneously form. We utilize these structures as templates for organizing functional nanoscale components such as metal and semiconductor nanoparticles. Besides the fundamental interest in expanding our abilities to organize material on the nanoscale, the creation of arrays of nanoparticles that are periodically ordered gives rise to unique properties, which could be useful for photonic application and sensing devices.

Our research involves the design, synthesis, characterization, and application of block copolymers (and other polymers) for nanotechnology. Block copolymers feature a variety of periodic nanoscale morphologies that are accessible in a highly controlled fashion through a spontaneous process of phase separation, and are therefore attractive as structured matrixes for directing the two- and three-dimensional arrangement of nanoparticles in composite materials. Controlling the morphology of nanoparticle ensembles in this way will enable fine-tuning their collective properties, which is important for a variety of applications, from microelectronics to diagnostics. Additionally, it allows the fundamental investigation of the dependence of these collective properties on the morphology of the ensemble, an option that was largely inaccessible so far due to our limited control over the morphology of the assembly.

A major effort in our research is dedicated to the polymer-mediated assembly of inorganic nanoparticles into morphologically controlled hierarchical structures. We have recently discovered that the utilization of two phase separation processes occurring on different time scales allows the organization of spherical gold nanoparticles into hierarchical structures, in which they are segregated into one type of domain and exhibit internal structure as well. Using this new strategy, we were able to assembly gold nanoparticles modified with PEG into hexagonal patterns on top hosting domains of the hosting PMMA domains of the PS-b-PMMA block copolymer (Fig. 1). Our current efforts are now aimed at expanding this research to the detection and measurement of novel optical and transport properties of the entire assemblies and their dependence on morphology.

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Fig. 1.SEM images of solvent annealed films of PS-b-PMMA (Mn 895 kDa) mixed with 12 nm gold particles protected with a mixed monolayer of citrate and PEG.

We are also interested in organizing nanoparticles using topographical thin film templates. We have developed the utilization of semi-crystalline polymer films as templates for selective deposition of nanoparticles. Recently, we have studied the fundamentals of nanoparticle organization using these templates, and delineated guidelines for obtaining two types of arrangements (i.e., near channel edges vs. uniform filling of the channels, Fig. 2) based on the nanoparticle size, chemistry, and its concentration. These results have been submitted for publication.

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Fig. 2.SEM images of 7 nm gold nanoparticles deposited into the channels formed in a poly(ethylene glycol) film under different conditions: (a) deposition mostly at channel edges. (b) uniform deposition inside the channels.

A developing direction of research in our group focuses on the combination of nano-fabrication techniques with self-assembly methodologies. We believe this combination will provide a powerful approach and the most versatile solution for the creation of long-range, organized materials, enjoying both from the accuracy of reproducibility offered by lithography techniques and from the high resolution and affordability of the self-assembled systems.

Other areas of activity in the group include the creation of novel block copolymers consisting of supramolecular polymer blocks, utilization of block copolymer films for spatially-confined deposition of polyelectrolytes through the layer-by-layer deposition, and employment of block copolymer templates for the creation of lithography-free microelectronic devices (e.g., transistors and memory devices).

Specific research topics related to Nanoscience and Nanotechnology:

  • Polymer mediated nanoparticle organization: Nanoparticle patterning on semi-crystalline films. Inorganic nanorod and metallic nanoparticle organization using block copolymer thin films.
  • Employment of block copolymer in composite systems for nanoparticle synthesis: Development of morphologically-directed, template synthesis of nanoparticles. Investigation of hierarchical structures of novel organometallic amphiphiles with block copolymers. In-situ preparation of anisotropically shaped nanoparticle assemblies in polymer matrixes.
  • Design and synthesis new block copolymers: Quasi-block copolymers. Shape and morphology responsive block copolymers. Replication of non-regular surface patterns for microelectronic device fabrication.
  • Development of assembly strategies using block copolymers: Spatially confined layer-by-layer (LbL) deposition using block copolymer films as templates. Inducing long-range ordering of block copolymer domains by incorporation of graphene nano-ribbons. Three-dimensional lithography.

List of publications in Nanoscience and Nanotechnology (2011-2012)

  • Mariela J. Pavan and Roy Shenhar "Two-Dimensional Nanoparticle Organization Using Block Copolymer Thin Films as Templates" J. Mater. Chem. 2011, 21, 2028-2040. Identified as a "Hot Article" for the Journal of Materials Chemistry
  • Eran Avnon, Nir Yaacobi-Gross, Elina Ploshnik, Roy Shenhar, and Nir Tessler "Low Cost, Centimeter Scale Nanoimprinting - Application to Organic Solar Cell Optimization" Org. Electron. 2011, 12, 1241-1246.
  • Ester Weiss, Kostas Ch. Daoulas, Marcus M?ller, and Roy Shenhar "Quasi-Block Copolymers: Design, Synthesis, and Evidence for their Formation in Solution and in the Melt" Macromolecules 2011, 44, 9773-9781.
  • Inbal Davidi, Artyom Semionov, David Eisenberg, Gil Goobes, and Roy Shenhar "Mesomorphic Behavior Induced by Stacking Interactions Between Poly(2-Vinyl Pyridine) and Palladium Pincer Surfactants in the Solid State" Soft Matter 2012, 8, 7393 - 7401.

Significant publications:

  • Roy Shenhar and Vincent M. Rotello "Nanoparticles as scaffolds and building blocks" Acc. Chem. Res. 2003, 36, 549-561. Cited: 304 times.
  • Roy Shenhar, Tyler B. Norsten and Vincent M. Rotello "Polymer-mediated nanoparticle assembly: Structural control and applications" Adv. Mater. 2005, 17, 657-669. Cited: 237 times.
  • Roy Shenhar, Eunhee Jeoung, Sudhanshu Srivastava, Tyler B. Norsten, and Vincent M. Rotello "Cross-linked nanoparticle stripes and hexagonal networks obtained via selective patterning of block copolymer thin films" Adv. Mater. 2005, 17, 2206-2210. Cited: 51 times.
  •  Mariela Pavan and Roy Shenhar, "Two-Dimensional Nanoparticle Organization Using Block Copolymer Thin Films as Templates" J. Mater. Chem. 2011, 21, 2028-2040. Cited: 3 times. Identified as a "Hot Article" for the Journal of Materials Chemistry
  •  Elina Ploshnik, Asaf Salant, Uri Banin, and Roy Shenhar, "Hierarchical co-assembly of nanorods and block copolymers in thin films", Adv. Mater. 2010, 22, 2774-2779. Cited: 4 times

Patents (2011-2012)

  • Roy Shenhar and Meirav Ben-Lulu "Selective layer-by-layer deposition over block copolymer nano-domains" U.S. Provisional patent application, 61/496,128, Filing date: 13.6.2011
  • Roy Shenhar, Marcus Muller, Kostas Ch. Daoulas, and Paul F. Nealey "Quasi-block copolymers: advanced resist materials for integrated device fabrication" U.S. Provisional patent application, 61/528,934, Filing date: 30.8.2011.

Cooperation with other universities in Israel:

Within Hebrew University:
  • Prof. Uri Banin, Institute of Chemistry; Assembly of nanocrystals with block copolymers
  • Prof. Shlomo Magdassi, Institute of Chemistry, Development of transparent conductive substrates using a combined inkjet-block copolymer approach
  • Prof. Yossi Paltiel, School of Engineering, Electrical noise measurements of assembled nanoparticles
With other universities:
  • Professor Nir Tessler - Electrical Engineering, Technion; Block copolymer-based electronic devices
  • Dr. Gil Goobes, Department of Chemistry, Bar Ilan University; Hierarchical block copolymer/surfactant mesomorphic structures

Research grants (2011-2012):

  • Funding agency: NanoSci-ERA+ (EU) "Interfacing Functional Nanocomposites for Non-Volatile Memory Devices" Roy Shenhar (coordinator), Nir Tessler, Alexander Boker, Agur Sevink, Andrei Zvelindovsky.
  • Funding agency: Israeli Science Foundation (ISF) "Exploration of the self-assembly of block copolymers and rod-shaped nanoparticles in ultrathin films".
  • Funding agency: US-Israel Binational Science Foundation (BSF) "Replicating Non-Regular Surface Structures Using Copolymers Featuring Dynamic Compositions" Roy Shenhar and Paul F. Nealey.

Distinctions and awards:

  • PhD student David Eisenberg won the best poster award in The 13th International Symposium on Novel Aromatic Compounds (ISNA13), Luxemburg, Luxemburg, July 2009.
  • MSc student Esti Weiss-Lavi won the Casali scholarship in Applied Chemistry for 2010.
  • PhD student Elina Ploshnik won the 2010 award from the Waldman Memorial Endowment in Polymer Research.
  • PhD student Meirav Ben-Lulu won a Minerva Short-Term Research Grant (MRG)
  • PhD student Meirav Ben-Lulu won the 2010 Harry and Sylvia Hoffman for Leadership and Responsibility Program

Students, postdocs and researchers:

Junior scientists/post-docs: Rajashekharayya Sanguramath Ph.D. students: David Eisenberg (graduated August 2011), Elina Ploshik, Inbal Davidi, Mariela Pavan, Meirav Ben Lulu.
M.Sc students: Ronit Dor, Amit Halevi, Elisheva Michman.

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