Publications

2012
Uri Banin and Amit Sitt. 2012. “Colloidal self-assembly: Superparticles get complex.” Nature materials, 11, 12, Pp. 1009-1011.
Shira Halivni, Amit Sitt, Ido Hadar, and Uri Banin. 2012. “Effect of nanoparticle dimensionality on fluorescence resonance energy transfer in nanoparticle–dye conjugated systems.” ACS nano, 6, 3, Pp. 2758-2765. Publisher's Version Abstract

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Fluorescence resonance energy transfer (FRET) involving a semiconductor nanoparticle (NP) acting as a donor, attached to multiple acceptors, is becoming a common tool for sensing, biolabeling, and energy transfer applications. Such nanosystems, with dimensions that are in the range of FRET interactions, exhibit unique characteristics that are related to the shape and dimensionality of the particles and to the spatial distribution of the acceptors. Understanding the effect of these parameters is of high importance for describing the FRET process in such systems and for utilizing them for different applications. In order to demonstrate these dimensionality effects, the FRET between CdSe/CdS core/shell NPs with different geometries and dimensionalities and Atto 590 dye molecules acting as multiple acceptors covalently linked to the NP surface is examined. Steady-state emission and temporal decay measurements were performed on the NPs, ranging from spherical to rod-like shaped systems, as a function of acceptor concentration. Changes in the NP geometry, and consequently in the distributions of acceptors, lead to distinctively different FRET behaviors. The results are analyzed using a modified restricted geometries model, which captures the dimensionality of the acceptor distribution and allows extracting the concentration of dye molecules on the surface of the NP for both spherical and elongated NPs. The results obtained from the model are in good agreement with the experimental results. The approach may be useful for following the spatial dynamics of self-assembly and for a wide variety of sensing applications.

Yehonadav Bekenstein, Kathy Vinokurov, Uri Banin, and Oded Millo. 2012. “Electronic properties of hybrid Cu2S/Ru semiconductor/metallic-cage nanoparticles.” Nanotechnology, 23, 50, Pp. 505710.
Yehonadav Bekenstein, Kathy Vinokurov, Tal J Levy, Eran Rabani, Uri Banin, and Oded Millo. 2012. “Periodic negative differential conductance in a single metallic nanocage.” Physical Review B, 86, 8, Pp. 085431.
Asaf Salant, Menny Shalom, Zion Tachan, Sophia Buhbut, Arie Zaban, and Uri Banin. 2012. “Quantum rod-sensitized solar cell: nanocrystal shape effect on the photovoltaic properties.” Nano letters, 12, 4, Pp. 2095-2100.
Chi-Tsu Yuan, Yong-Gang Wang, Kuo-Yen Huang, Ting-Yu Chen, Pyng Yu, Jau Tang, Amit Sitt, Uri Banin, and Oded Millo. 2012. “Single-particle studies of band alignment effects on electron transfer dynamics from semiconductor hetero-nanostructures to single-walled carbon nanotubes.” ACS nano, 6, 1, Pp. 176-182. Publisher's Version Abstract

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We utilize single-molecule spectroscopy combined with time-correlated single-photon counting to probe the electron transfer (ET) rates from various types of semiconductor hetero-nanocrystals, having either type-I or type-II band alignment, to single-walled carbon nanotubes. A significantly larger ET rate was observed for type-II ZnSe/CdS dot-in-rod nanostructures as compared to type-I spherical CdSe/ZnS core/shell quantum dots and to CdSe/CdS dot-in-rod structures. Furthermore, such rapid ET dynamics can compete with both Auger and radiative recombination processes, with significance for effective photovoltaic operation.

Kathy Vinokurov, Janet E Macdonald, and Uri Banin. 2012. “Structures and mechanisms in the growth of hybrid Ru–Cu2S nanoparticles: From cages to nanonets.” Chemistry of Materials, 24, 10, Pp. 1822-1827. Publisher's Version Abstract

Combining metal and semiconductor segments with well-defined morphologies on a single hybrid nanoparticle provides functionality benefiting from the joint and possibly also synergetic properties of the disparate components. We have recently reported the synthesis of a novel family of Ru nano-inorganic caged (NICed) copper(I) sulfide hybrid nanoparticles, which were grown through a mechanism of selective edge growth of the Ru on the copper(I) sulfide seeds. In this work we investigate the effect of reaction conditions on the Ru–Cu2S products. There is an extraordinary sensitivity to reaction temperature in which four product structures were discovered upon varying the reaction temperature from 190 to 220 °C. The products changed from homogeneous nuclei of Ru along with the free Cu2S seed at lower temperature, to Ru nano-inorganic caged copper(I) sulfide, to long thin Ru structures protruding from the seed surface at the higher temperature range. The resulting materials were imaged and characterized by transmission electron microscopy (TEM), high-resolution TEM (HRTEM), high-angle annular dark field-scanning TEM (HAADF-STEM), and powder Xray diffraction. Differential scanning calorimetric (DSC) analysis of the Cu2S template nanoparticles revealed an endothermic peak at the specific temperature for selective edge growth of Ru, and was assigned to a surface change on the seed particle. Competition between homogeneous nucleation of the secondary material Ru and heterogeneous nucleation on the seed Cu2S nanoparticle leading to a rich reaction landscape is discussed.

Ilai Schwarz, Moshe G Harats, Nitzan Livneh, Shira Yochelis, Ayelet Strauss, Adiel Zimran, Uri Banin, Yossi Paltiel, and Ronen Rapaport. 2012. “Theory and experiments of Bragg cavity modes in passive and active metallic nanoslit array devices.” JOSA B, 29, 2, Pp. A127-A137.
Denis Mongin, Ehud Shaviv, Paolo Maioli, Aurélien Crut, Uri Banin, Natalia Del Fatti, and Fabrice Vallée. 2012. “Ultrafast photoinduced charge separation in metal–semiconductor nanohybrids.” ACS nano, 6, 8, Pp. 7034-7043.
Uri Banin and Elizabeth Janet Macdonald. 2012. “Cage nanostructures and prepartion thereof.” United States of America.
Uri Banin and Taleb Mokari. 2012. “Nanostructures and method for selective preparation.” United States of America.
Ronen Rapaport, Shira Yochelis, Yossef Paltiel, and Uri Banin. 2012. “Photon emitter embedded in metallic nanoslit array.” United States of America.
Yorai Amit, Adam Faust, Itai Lieberman, Lior Yedidya, and Uri Banin. 2012. “Semiconductor nanorod layers aligned through mechanical rubbing.” physica status solidi (a), 209, 2, Pp. 235-242. Publisher's Version Abstract

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Large‐scale lateral alignment of nanorods (NRs) is of interest for manifestation of their anistropic properties including polarized emission and directional electrical transport. This study investigates the utility of mechanical rubbing for macroscopic scale alignment of colloidal semiconductor NRs. CdSe/CdS seeded‐rods, exhibiting linearly polarized emission, are aligned by mechanical rubbing of a spin‐coated glass substrate. The dragging force exerted by the rubbing fibers results in deflection and reorientation of the NRs along the rubbing direction. The rubbed samples were characterized by various methods including absorption, polarized emission, optical fluorescence microscopy, atomic force microscopy, and ultra‐high resolution scanning electron microscopy. The emission polarization contrast ratio (CR), defined as the ratio between emission intensities parallel and perpendicular to the rubbing direction, was used to characterize the rods alignment. The effects of substrate treatments on the CR were studied, showing that partially hydrophobic surface provides optimal conditions for alignment. Excess organic ligands added to the deposited NR solution strongly affect the extent of alignment. This was studied for a series of NR samples of different dimensions and an optimal additive ratio of ∼3 ligand molecules per 1 nm2 NR surface area was found to yield the highest CR. Average CR values of 3.5 were detected over the entire 6 cm2 substrate area, with local values exceeding 4.5. While samples of rubbed spherical quantum dots and spin‐coated films of NRs show no emission polarization, the emission intensity from rubbed NR samples is polarized obeying Malus' law (wherein, the intensity is proportional to cos2(θ)). Mechanical rubbing, well known for its use in LC devices, may be considered as a method for large‐scale alignment of NRs on substrates.