Home Page Researchers Shlomo Yitzchaik

Shlomo Yitzchaik

Institute of Chemistry
Faculty of Science
The Hebrew University, Jerusalem 91904, Israel
Tel: +972-2-6586971; Fax: +972-2-6585319
Email: shlomo.yitzchaik@mail.huji.ac.il;
Website: http://chem.ch.huji.ac.il/yitzchaik

4-isopropyl pyridine hydroperoxide coils with regular nanocavities in poly (butyl methacrylate) template

Recently the novel molecule ? 4-isopropyl pyridine hydroperoxide (4-IPPH) was introduced as a product of aerobic oxidation of 4-isopropyl pyridine/4-propyl pyridine mixture. 4-isopropyl pyridine was used as a model to mimicking the spontaneous oxidation of poly(4-vinyl pyridine).

During 2011-2012 has been continued interest in the physical properties of 4-IPPHP. Investigation of the energy band gap of 4-IPPH crystals revealed, that such crystals should exhibit strong semiconductive properties: the energy band gap about 1.3 eV (0.145 Ha) was evaluated (Fig. 1). For comparison, pyridine side chain HOMO-LUMO band gap is 4.05 eV.

Figure 1. Scheme of the 4-IPPH single crystal (left) and energy band gap (right)

Further, in 2011-2012 years the effect of spontaneous oxidation of 4-isopropyl pyridine has been studied for the composition, where the 4-isopropyl pyridine/pyridine bath was doped with the acidic polymer - poly (butyl methacrylate) (PBMA).

Here we report the observation of supramolecular coil with well-defined micro porous structural areas, which was formed in a 4-isopropyl pyridine/pyridine bath in the presence of poly (butyl methacrylate) (PBMA). The well-defined micro porous structural areas composed from 4-IPPH crystallites. The 4-IPPH in polymer template formed crystalline micro pores structure with the size of porous near 2 nm (Fig. 2). Practically, similar porous structures are widely known for the systems which are based on chiral molecules.

Figure 2. Optical microscope image of linear and coil-like solid particles (a); HR SEM image of fibril-like structure of linear 4-IPPH crystals (b); PBMA/4-IPPH coil, formed in bi-molecular bath (c); Detailed structure of the polymer layers (d); Crystalline structure (e). Insert ? Furrier transform of the lattice on (e).

Two kinds of sub-millimeter size solid precipitates ? colorless needle-like crystals andwhite coil-like particles - were visually identified and taken for investigation (Fig.2). The structure of the colorless needle-like crystals had been solved as 4-isopropylpyridine hydroperoxide (4-IPPH) crystals1 by application of single crystal X-Ray Diffraction (Bruker Appex2 KappaCCD difractometer).

At the same time, the white coil-like particles, as can be seen in the HR SEM images typically have a morphology which may be described as ?coiled terraces? (Fig. 2c and d). The terraces are composed of micron-scale alternating smooth and cavity regions shown in Fig. 2e. The prolonged cavity regions are composed of extremely well-defined parallel rows of 1-2 nm size cavities.

The Fourier transform of the extended cavities region (insert in Fig. 2, d) displayed a few characteristic distances (each of tens of nanometer length). Among these characteristic lengths the most frequent ones in all the analyzed crystallites was 78 nm and 58 nm, which are multiples of unit cell parameters known for 4-IHHP crystal structure: 78 nm ? (b=7.7?)x100; 58 ? (c=11.5?)x50.

In order to further refine organization of coil-like particles we applied powder X-Ray diffraction. Figure 3 shows experimental XRD pattern acquired from powder material. Careful examination of an XRD pattern reveals that the specimen contains known 4-IPPH (C8H11NO2, CCDC 701960). Theoretical peak's positions of this phase are labeled by vertical lines in Fig. 3. The profile matching has allowed refining the values of unit cell parameters. The refined values of unit cell parameters are a=9.49 ? b=7.76 ?, c=11.69 ? and ?=112.6. The average crystallite size calculated with using Scherrer equation is 79.1 nm. (For comparison: 4-IPPH crystals is monoclinic, P21/c (No.14), a) 9.334(2) ?, b) 7.725(2) ?, c) 11.499(2) ?, ?=112.29. Crystallographic data have been deposited in the Cambridge Crystallographic Data Center under accession #701960).

Figure 3. . Powder XRD pattern acquired from a powder sample (peak's positions of 4-IPPH phase are labeled by vertical lines).

To conclude, two types of 4-IPPH crystals formed in a mixed bath of pyridine/4-isopropyl pyridine: needle-like crystals in the presence of poly (butyl methacrylate) and extended crystalline coils are formed with the spiral terrace layers. Considering the coil like structures, we can assume that the stability of a new type of coil structure can be explain by high flexibility of 4-IPPH crystals, which has strong similarity to the chain polymer structure and competition of different kind of molecular interactions during the crystal growth. At the present stage the physical properties of the coil-like structures of 4-IPPH is under investigation.

Specific research topics related to Nanoscience and Nanotechnology:

  • Neuromorphic computing devices
  • Nanoporous photoactive smart gels
  • Molecular-nanolayers based biochemical sensors
  • Hybrid thin films for photovoltaic solar cells applications

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

  • Nahor, A.; Berger, O.; Bardavid, Y.; Toker, G.; Tamar, Y.; Asscher, M.; Yitzchaik, S.; Sa?ar, A. Hybrid Structures of Porous Silicon and Conjugated Polymers for Photovoltaic Applications Phys. Status Solidi (c), 2011, 8, 1908-1912.
  • Bardavid, Y.; Goykhman, I.; Nozaki, D.; Cuniberti, G.; Yitzchaik, S. Dipole Assisted Photo-Gated Switch in Spiropyran Grafted Polyaniline Nanowires J. Phys. Chem. C 2011, 115, 3123?3128.
  • Horesh, M.; Lidich, N.; Yitzchaik, S.; Hanein Y. A Temperature-Differential Affinity Biosensor: Model and D-optimal Performance Limits IEEE Sens. J., 2011, 11, 2007-2015.
  • Snir, E.; Joore, J.; Timmerman, P.; Yitzchaik, S. Monitoring selectivity in kinase-promoted phosphorylation of peptidic substrates using label-free electrochemical detection methods Langmuir, 2011, 27, 11212-11221.

Significant publications:

  • Yitzchaik, S. and Marks, T.J., "Chromophoric self-assembled superlattices" Acc. Chem. Res. 1996, 29, 197-202. [106].
  • Cohen, R.; Zenou, N.; Cahen, D.; Yitzchaik, S., "Molecular Electronic Tuning of Si Surfaces" Chem. Phys. Lett. 1997, 279, 270-274. [55].
  • Burtman, V.; Zelichenok, A.; Yitzchaik S., "Organic Quantum-Confined Structures via Molecular Layer Epitaxy" Angew. Chem. Int. Eng. Ed. 1999, 38, 2041-2045. German Version: Angew. Chem. 1999, 111, 2078-2082. [22]
  • Sfez, R.; De-Zhong, L.; Turyan, I.; Mandler, D.; Yitzchaik, S., "Polyaniline Monolayer Self-Assembled on Hydroxyl-Terminated Surfaces" Langmuir 2001, 17, 2556-2559. [44].
  • He, T.; Ding, H.; Peor, N.; Lu, M.; Corley, D.; Chen, B.; Ofir, Y.s; Gao, Y.; Yitzchaik, S.; Tour, J.M., "Silicon/Molecule Interfacial Electronic Modifications" J. Am. Chem. Soc. 2008, 130, 1699-1710. [34]

Patents (2010-2012)

  • Spira, M., Shappir, J. and Yitzchaik, S., "Electronic device for communication with living cells" -U.S. Patent Number: US 07795039 - September 14, 2010.
  • Hanein, Y., Yitzchaik, S., Sernagor, E., Banin, U., Cheshnovsky, O., "Photoelectrical devices for stimulating neurons" US Patent Appl. 61/227,472 (22.7.2009); PCT Application No. PCT/IL2010/000574 (July 20, 2010).
  • Yitzchaik, S. and Vaganova, E., "Polymeric Gel with High Level Sensitivity to Visible Light Irradiation: Voltage/Structural Control of Electron Transfer Centers" US Application No. 61/500,292 (2011).
  • Yitzchaik, S. and Vaganova, E., PCT Application No. PCT/IL2012/050212 "Polymeric compositions and uses thereof" (July 26, 2012).

Cooperation with industries and defense projects (2010-2011):

Participation in Magnet consortia - Industrial partners: Tower Semiconductors, and Orbotech; Academic partners: Prof. A. Saar and Prof. M. Ascher: "Solar Energy Solutions (SES)".

Cooperation with other universities in Israel:

Within Hebrew University:
  • Chemistry: Prof. M. Ascher, Dr. R. Yerushalmi, Dr. D. Danovich
  • Physics: Prof. A. Saar and Prof. Y. Shappir.

With other universities:

E. Lifshitz (IIT); Y. Hanein Y. Hanein and O. Cheshnovsky (TAU); E. Wachtel (WIS); P. Timmerman (Univ. of Amsterdam); K. Kamar?s (Hungarian Academy of Sciences); A. Bianco (CNRS, Strasbourg); H.-H. Limbach (Free University Berlin); S. Borges (IMEC-Belgium); T.J. Marks (Northwestern Univ.); Yu-Ju Chen [Academia Sinica, Taiwan]; G. Wendin (Chalmers, Sweden), D. Vuillaume, (CNRS-IEMN, France), G. Cuniberti, (TUD, Germany), C. Gamrat (CEA, France) M. Calame, (UNIBAS, Switzerland), V. Beiu, UAEU (United Arab Emirates).

Research grants:

  • 2009-2012: Chief scientist, Ministry of Industry and Labor, Magnet "Solar Energy Solutions (SES)" partners: Prof. A. Sa?r and Prof. M. Ascher.
  • 2012-2015: Ministry of Sciences and Technology (MOST), ?Nano-composites for direct light induced cell stimulation? Partners: Prof. Y. Hanein and Prof. O. Cheshnovsky (TAU) and Prof. U. Banin (HUJ).
  • 2012-2015: Ministry of Sciences and Technology (MOST), ?Novel hybrid structures of porous silicon-conducting polymers-quantum dots for Solar Cell Applications? Partners: Prof. A. Saar and Prof. E. Lifshitz (IIT).
  • 2012-2013: Yissum - Baby Seed Project ?Supersensitive low energy capacitor for distance control of flexible-touch screens.?
  • 2012-2015: Academia Sinica ? Hebrew University ?Using nanotechnology for developing kinase inhibitors as anti-cancer leads? partners: Assaf Friedler [HUJI], Danny Porath [HUJI], and Yu-Ju Chen [AS]
  • 2012-2017: The International Nano-Science and Technology Advisory Board (INAB) FTA program: ?Hybrid Nanomaterials and Formulations for Functional Coatings and Printed Devices?
  • 2013-2016: EC 7th Framework (STREP): SYMONE. ?Synaptic Molecular Networks for Bio-inspired Information Processing?; Partners: G. Wendin (Chalmers, Sweden), D. Vuillaume, (CNRS-IEMN, France), G. Cuniberti, (TUD, Germany), C. Gamrat (CEA, France) M. Calame, (UNIBAS, Switzerland), V. Beiu, UAEU (UAE).

Distinctions and awards:

  • 2010: The Erasmus Mundus Lecturer - The European Commission: Nanotechnology in Modern Society (EMM-nano).
  • 2009: The Gesellschaft Deutscher Chemiker (German Chemical Society) award with the Richard-Willstatter-Lecture

Students, postdocs and researchers (include those graduated in 2009-2010):

Staff scientist: Dr. Evgenia Vaganova.
Postdocs: Dr. Jugun Chinta, Dr. Sharon Waichman, Dr. Ramesh V. Naidu.
Ph.D. students: Elsa Snir.
M.Sc students: Einav Amit, Alina Gankin, Evgeniy Mervinetskiy, Leah Reiss.
Students: Shahar Derei, Tamar Sery, Dorin Hazout.

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