Daniel Mandler

Institute of Chemistry
Faculty of Science
The Hebrew University, Jerusalem 91904, Israel
Tel: +972-2-6585831; Fax: +972-2- 6585319
E-mail: mandler@vms.huji.ac.il
Website:http://chem.ch.huji.ac.il/mandler/

Electrochemically Functionalized Coatings

Our research focuses on different aspects of patterning and deposition of nanostructures by electrochemistry. Specifically, we have focused on the following topics:

Electrochemical deposition of nanostructures

We have developed a novel electrochemical method for the formation of nanocomposite thin films made of different nanoobjects, such as carbon nanotubes and nanoparticles within a sol-gel matrix. Specifically, this last year we focused on the electrodeposition of binary sol-gel composite films. SiO2-TiO2 binary composite films were prepared by a unique electrodeposition approach from a mixture of sol-gel precursors containing tetramethoxysilane (TMOS) and titanium tetraisopropoxide (TTIP). A negative potential applied to either stainless steel or ITO substrates caused the reduction of the solvent, thus increasing the concentration of hydroxyl ions, which enhanced the precursor condensation and film deposition. The Ti:Si ratio in the films depended on the deposition potential, time and composition of the precursor solution. This ratio decreased as the films grew thicker due to the more facile kinetics of silica deposition. Nevertheless, the Ti:Si ratio in the films was always lower than in the corresponding precursor solution. As the Ti:Si ratio in the deposition solution increased, the thickness of the films electrodeposited at the same conditions gradually decreased. SIMS and cross-section EDX analysis showed (Figure 1) that the Ti:Si ratio in the films increased from the surface to the substrate, suggesting electrodeposition as a potential method for preparing graded sol-gel films.

Figure 1: Cross-section SEM image (A) and the Ti:Si atomic ratio profile acquired by EDX (B) of the SiO2-TiO2 binary sol-gel film prepared on ITO at -1.3 V for 5 min.

Preparation and Characterization of Mono and Multilayer Films Using the Langmuir?Blodgett Technique

Anisotropic nanohybrides consisting of CdS nanorod tipped by an Au nanoparticle on one edge (Au-NRs) were perpendicularly oriented using the Langmuir-Blodgett (LB) technique. These Au tipped hybrids reveal light induced charge separation at the semiconductor-metal interface. This property makes these particles suitable for photocatalitic and photovoltaic applications. Clearly, the Au-NRs ought to be well oriented in order to obtain an applicative device.

In this study we demonstrated the viability of the LB method to orient these NRs at the water-air interface and transfer them onto surface. To the best of our knowledge, the LB technique has not been used so far for perpendicularly orienting anisotropic nanoobjects. This is an interesting attempt to expand the molecular terms of amphiphilicity into nanoobjects.

The orientation of the Au-NRs was studied in-situ while compressing the LB trough using the Pi-A isotherm, Brewster angle microscopy and horizontal touch voltammetric analysis. The compressed layers were transferred by the Langmuir-Schaefer approach onto TEM grids (Figure 2) and analyzed by TEM, SEM, STEM and XPS. All these techniques provided clear evidence for the preferentially perpendicular orientation of the Au-NRs firstly achieved by the LB method.

Figure 2: TEM images of oriented LS film of Au-NRs (A), closely packed LS layer (B) and layer obtained by slow solvent evaporation (C).

3. Local Deposition of Anisotropic Nanoparticles Using Scanning Electrochemical Microscopy (SECM)

We demonstrated the localized electrodeposition of anisotropic metal nanoobjects, i.e. Au nanorods (GNR) on indium tin oxide (ITO), using scanning electrochemical microscopy (SECM). A gold microelectrode was the source of the gold ions whereby double pulse chronoamperometry was employed to generate initially Au seeds which were further grown under controlled conditions. The distance between the microelectrode and the ITO surface as well as the different experimental parameters (electrodeposition regime, solution composition and temperature) were optimized to produce faceted gold seeds with the required characteristics (size and distribution). Colloidal chemical synthesis was successfully exploited for better understanding the role of the surfactant and different additives in breaking the crystallographic symmetry and anisotropic growth of GNR. Experiments performed in conventional three-electrode cell revealed the most appropriate electrochemical conditions allowing high yield synthesis of well-defined in shape nanorods (Figure 3) as well as nanocubes and bipyramids.

Figure 3: SEM images of GNR electrodeposited on ITO electrode at 50 °C from an aqueous solution containing 1mM HAuCl4, 50 mM CTAC, 50 mM KCl and 1 mM KBr. The first short pulse (5 s) was at -0.6 V while the second long pulse (400 s) was at 0.35 V.

Specific research topics related to Nanoscience and Nanotechnology:

• Electrochemically codeposition of nanoobjects and sol-gel.
• Design of functionalized mono and multilayers of nanometric films by the Langmuir-Blodgett approach.
• Visualization of fingerprints using nanotechnology.
• Application of self-assembled monolayers in electroanalytical chemistry.
• Solar-thermal coatings based on inorganic nanoparticles.

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

• L. Liu, R. Toledano, T. Danieli, J.-Q. Zhang, J.-M. Hu and D. Mandler, Electrochemically Patterning Sol?Gel Structures on Conducting and Insulating Surfaces, Chem. Comm. 2011, 47, 6909-6911.
• E. Malel, J. Colleran and D. Mandler, Studying the Localized Deposition of Ag Nanoparticles on Self-Assembled Monolayers by Scanning Electrochemical Microscopy (SECM), Electrochim. Acta, 2011, 56, 6954-6961.
• D. Mandler and S. Kraus-Ophir, Self-Assembled Monolayers (SAMs) for Electrochemical Sensing, J. Solid State Electrochem., 2011, 15, 1535-1558.
• E. Gdor and D. Mandler, Electrochemical Assisted Deposition of Biodegradable Polymer Nanoparticles/Sol Gel Thin Films, J. Mater. Chem., 2011, 21, 12145-12150
• S. Kraus-Ophir, I. Jerman, B. Orel and D. Mandler, Symmetrical thiol functionalized polyhedral oligomeric silsesquioxanes as building blocks for LB films, Soft Matter, 2011, 7, 8862-8869.
• T. Danieli, J. Colleran and D. Mandler, Deposition of Au and Ag Nanoparticles on PEDOT, Phys. Chem. Chem. Phys. 2011, 13, 20345-20353.
• M. Hitrik, V. Gutkin, O. Lev and D. Mandler, Preparation and Characterization of Mono and Multilayer Films of Polymerizable 1,2 Polybutadiene Using the Langmuir?Blodgett Technique, Langmuir, 2011, 27, 11889-11898.
• R. Guslitzer-Okner and D. Mandler, Electrochemical Coating of Medical Implants, in Modern Aspects of Electrochemistry, N. Eliaz Editor, Springer, 2011, 52, 291-342.
• R. Ginzburg-Turgeman and D. Mandler, Improving the Adhesion of Polymethacrylate Thin Films onto Indium Tin Oxide Electrodes using a Silane-Based ?Molecular Adhesive?, J. Solid State Electrochem. 2011, 15, 2401-2407
• Z. Y. Jin, G. Gueven, V. Bocharova, J. Halamek, I. Tokarev, S. Minko, A. Melman, D. Mandler and E. Katz, ACS Appl. Mater. Interfaces 2012, 4, 466-475.
• Z. J. Wang, J. Zhang, Y. Z. Yin, S. X. Wu, D. Mandler, H. Zhang, Fabrication of Nanoelectrode Ensembles by Electrodepositon of Au Nanoparticles on Single-Layer Graphene Oxide Sheets, Nanoscale, 2012, 4, 2728-2733.
• T. Noyhouzer and D. Mandler, A New Electrochemical Flow Cell for the Remote Sensing of Heavy Metal, Electroanal. 2012, in press.
• N. Jaber, A. Lesniewski, H. Gabizon, S. Shenawi, D. Mandler and J. Almog, Visualization of Latent Fingermarks by Nanotechnology: Reversed Development on Paper ? A Possible Remedy to the Variation in Sweat Composition, Angew. Chem. 2012, in press.
• R. G. Fedorov and D. Mandler, Local Deposition of Anisotropic Nanoparticles Using Scanning Electrochemical Microscopy (SECM), submitted.
• L. Liang and D. Mandler, Electrodeposition of Binary Sol-gel Composite Films: A Method for Preparing Graded Materials, submitted.

Five most significant publications:

• F. Malem and D. Mandler, Self Assembled Monolayers in Electroanalytical Chemistry: Application of w-Mercapto Carboxylic Acid Monolayers for the Electrochemical Detection of Dopamine in the Presence of a High Concentration of Ascorbic Acid. Anal. Chem. 1993, 65, 37-41.
• I. Turyan and D. Mandler, Selective Determination of Chromium by a Self-Assembled Monolayer Based Electrode. Anal. Chem., 1997, 69, 894-897.
• I. Turyan, U. Opara Krasovec, B. Orel, T. Saraidorov, R. Reisfeld, D. Mandler, "Writing-Reading-Erasing" on Tungsten Oxide Films by the Scanning Electrochemical Microscope (SECM). Adv. Mater. 2000, 12, 330-333.
• R. Shacham, D. Avnir, D. Mandler, Electrodeposition of Methylated-Sol-Gel Films on Conducting Surfaces. Adv. Mater. 1999, 11, 384-388.
• M. Sametband, I. Shweky, U. Banin, D. Mandler, and J. Almog, Application of Nanoparticles for the Enhancement of Latent Fingerprints, Chem. Comm. 2007, 1142-1144.

New patents and patents utilization (2010-2012):

• Process for Electrochemical Coating of Conductive Surfaces by Organic Nanoparticles, with Shlomo Magdassi.
• Solar-Radiation-Absorbing Formulation and Related Apparatus and Methods, with Shlomo Magdassi.
• Metalized Balloon Catheter for Drug-eluting balloons with Shlomo Magdassi and Subramanian Venkatraman from the School of Materials Science & Eng, NTU, Singapore.

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

• Magnet SES - solar energy systems
• Magnet NES - nano empowerment systems
• Project with BrightSource on Photothermal Solar Conversion

Success stories:

Cooperation with Industry and Academia

• Collaboration with Shlomo Magdassi (different projects).
• Collaboration with Joseph Almog (visualization of fingerprints by nanotechnology).
• Collaboration with Uri Banin on organizing nanorods using the LB method.
• Collaboration with Meital Reches and David Avnir on developing antibiofouling, anticorrosion and antibacterial systems.

• Collaboration with Moshe Lalouche from Bar Ilan University.
• Collaboration with Rachel Yerushalmi from Ben Gurion University.

Research grants:

• ISF
• GIF
• BSF
• Magnet SES
• Magnet NES
• Magneton
• Ministry of Science - Tashtiot program
• European project
• Office of Naval Research - Technical Support Working Group (TSWG)
• Project with Nanyang Technological University

List of Students, postdocs and researchers:

Staff scientists:Dr. Camille Zwicker, Dr. Noam Tal
Postdocs: Dr. Adam Lesniewski, Dr. Liang Liu, Dr. Sanaa Shenawi
PhD students: (present and graduated) Shlomit Kraus, Tomer Noyhouzer, Esteban Malel, Tamar Danieli, Maria Hitrik, Efrat Gdor, Reut Toledano, Itamar Gofberg, Netta Bruchiel-Spanier.
MSc students: Moran Rave, Dani Tulchinski, Tehila Shahar, Elena Krent, Roman Federov, Lihi Levi, Noa Metoki

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