Publications

2014
Kathy Vinokurov, Yehonadav Bekenstein, Vitaly Gutkin, Inna Popov, Oded Millo, and Uri Banin. 2014. “Rhodium growth on Cu 2 S nanocrystals yielding hybrid nanoscale inorganic cages and their synergistic properties.” CrystEngComm, 16, 40, Pp. 9506-9512.
Guohua Jia, Amit Sitt, Gal B Hitin, Ido Hadar, Yehonadav Bekenstein, Yorai Amit, Inna Popov, and Uri Banin. 2014. “Couples of colloidal semiconductor nanorods formed by self-limited assembly.” Nature materials, 13, 3, Pp. 301. Publisher's Version Abstract

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Colloidal nanocrystal synthesis provides a powerful approach for creating unique nanostructures of relevance for applications. Here, we report that wurtzite ZnSe nanorod couples connected by twinning structures can be synthesized by means of a self-limited assembly process. Unlike for individual nanorods, the band-edge states calculated for the nanorod couples are predominantly confined to the short edges of the structure and this leads to low photoluminescence polarization anisotropy, as confirmed by single-particle fluorescence. Through a cation-exchange approach, the composition of nanorod couples can be readily expanded to additional materials, such as CdSe and PbSe. We anticipate that this family of nanorod-couple structures with distinct compositions and controlled properties will constitute an ideal system for the investigation of electronic coupling effects between individual nanorod components on the nanoscale, with relevance to applications in optics, photocatalysis and optoelectronic devices.

Lilach Bareket, Nir Waiskopf, David Rand, Gur Lubin, Moshe David-Pur, Jacob Ben-Dov, Soumyendu Roy, Cyril Eleftheriou, Evelyne Sernagor, and Ori Cheshnovsky. 2014. “Semiconductor nanorod–carbon nanotube biomimetic films for wire-free photostimulation of blind retinas.” Nano letters, 14, 11, Pp. 6685-6692. Publisher's Version Abstract

We report the development of a semiconductor nanorod-carbon nanotube based platform for wire-free, light induced retina stimulation. A plasma polymerized acrylic acid midlayer was used to achieve covalent conjugation of semiconductor nanorods directly onto neuro-adhesive, threedimensional carbon nanotube surfaces. Photocurrent, photovoltage, and fluorescence lifetime measurements validate efficient charge transfer between the nanorods and the carbon nanotube films. Successful stimulation of a light-insensitive chick retina suggests the potential use of this novel platform in future artificial retina application

2013
Amit Sitt, Na’ama Even-Dar, Shira Halivni, Adam Faust, Lior Yedidya, and Uri Banin. 2013. “Analysis of shape and dimensionality effects on fluorescence resonance energy transfer from nanocrystals to multiple acceptors.” The Journal of Physical Chemistry C, 117, 43, Pp. 22186-22197. Publisher's Version Abstract

The dynamic process of energy transfer from semiconductor nanocrystals acting as donors to multiple acceptors attached to their surface emerges as an important tool for probing the nanoparticle environment in the nanometric scale. Understanding the underlying principles which govern the dynamics of the energy transfer process, and in particular the role of the shape and dimensions of the nanocrystal in determining it, is crucial for utilizing it for a range of applications including sensing, biolabeling, and energy funneling. We describe and theoretically analyze the temporal behavior of energy transfer from core/shell spherical dot, dot in a rod, and dot in a pod nanocrystals to multiple acceptors linked to their surface. Using a modified restricted geometries model, we evaluate the different parameters which affect the energy transfer and demonstrate the role of the nanocrystal geometry and dimensions in determining the dynamics of the energy transfer process. The modeled dynamics show good agreement to experimental data measured for spherical and dot in a rod nanocrystals. The results obtained from the model indicate that energy transfer may be used for extracting the dimensions and dimensionalities of nanocrystals and for probing real-time processes in the ensemble level, which are relevant for characterization and sensing applications.

Amit Sitt, Ido Hadar, and Uri Banin. 2013. “Band-gap engineering, optoelectronic properties and applications of colloidal heterostructured semiconductor nanorods.” Nano Today, 8, 5, Pp. 494-513.
Yorai Amit, Adam Fasut, Oded Milo, Eran Rabani, Anatoly Frenkel, and Uri Banin. 2013. “How to Dope a Semiconductor Nanocrystal.” ECS Transactions, 58, 7, Pp. 127.
Nir Waiskopf, Rany Rotem, Itzhak Shweky, Lior Yedidya, Hermona Soreq, and Uri Banin. 2013. “Labeling Acetyl-and Butyrylcholinesterase Using Semiconductor Nanocrystals for Biological Applications.” BioNanoScience, 3, 1, Pp. 1-11.
Ido Hadar, Gal B Hitin, Amit Sitt, Adam Faust, and Uri Banin. 2013. “Polarization properties of semiconductor nanorod heterostructures: From single particles to the ensemble.” The journal of physical chemistry letters, 4, 3, Pp. 502-507. Publisher's Version Abstract

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Semiconductor heterostructured seeded nanorods exhibit intense polarized emission, and the degree of polarization is determined by their morphology and dimensions. Combined optical and atomic force microscopy were utilized to directly correlate the emission polarization and the orientation of single seeded nanorods. For both the CdSe/CdS sphere-in-rod (S@R) and rod-in-rod (R@R), the emission was found to be polarized along the nanorod’s main axis. Statistical analysis for hundreds of single nanorods shows higher degree of polarization, p, for R@R (p = 0.83), in comparison to S@R (p = 0.75). These results are in good agreement with the values inferred by ensemble photoselection anisotropy measurements in solution, establishing its validity for nanorod samples. On this basis, photoselection photoluminescence excitation anisotropy measurements were carried out providing unique information concerning the symmetry of higher excitonic transitions and allowing for a better distinction between the dielectric and the quantum-mechanical contributions to polarization in nanorods.

Yorai Amit, Hagai Eshet, Adam Faust, Anitha Patllola, Eran Rabani, Uri Banin, and Anatoly I Frenkel. 2013. “Unraveling the impurity location and binding in heavily doped semiconductor nanocrystals: The case of Cu in InAs nanocrystals.” The Journal of Physical Chemistry C, 117, 26, Pp. 13688-13696. Publisher's Version Abstract

The doping of colloidal semiconductor nanocrystals (NCs) presents an additional knob beyond size and shape for controlling the electronic properties. An important problem for doping with aliovalent elements is associated with resolving the location of the dopant and its structural surrounding within small NCs, an issue directly connected with self-purification. Here we used a postsynthesis diffusion-based doping method for introducing Cu impurities into InAs quantum dots. X-ray absorption fine structure (XAFS) spectroscopy experiments along with first-principle density functional theory (DFT) calculations were used to probe the impurity sites. The concentration dependence was investigated for a wide range of doping levels, helping to derive a self-consistent picture where the Cu impurity occupies an interstitial site within the InAs lattice. Moreover, at extremely high doping levels, Cu–Cu interactions are identified in the XAFS data. This structural model is supported by X-ray diffraction data, along with the DFT calculation. These findings establish the reproducibility of the diffusion-based doping strategy giving rise to new opportunities of correlating the structural details with emerging electronic properties in heavily doped NCs.

Mark J Polking, Prashant K Jain, Yehonadav Bekenstein, Uri Banin, Oded Millo, Ramamoorthy Ramesh, and Paul A Alivisatos. 2013. “Controlling localized surface plasmon resonances in GeTe nanoparticles using an amorphous-to-crystalline phase transition.” Physical review letters, 111, 3, Pp. 037401. Publisher's Version Abstract

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Infrared absorption measurements of amorphous and crystalline nanoparticles of GeTe reveal a localized surface plasmon resonance (LSPR) mode in the crystalline phase that is absent in the amorphous phase. The LSPR mode emerges upon crystallization of amorphous nanoparticles. The contrasting plasmonic properties are elucidated with scanning tunneling spectroscopy measurements indicating a Burstein-Moss shift of the band gap in the crystalline phase and a finite density of electronic states throughout the band gap in the amorphous phase that limits the effective free carrier density.

Uri Banin, Yuval Ben-Shahar, and Kathy Vinokurov. 2013. “Hybrid semiconductor–metal nanoparticles: from architecture to function.” Chemistry of Materials, 26, 1, Pp. 97-110. Publisher's Version Abstract

Hybrid nanoparticles combine two or more disparate materials on the same nanosystem and represent a powerful approach for achieving advanced materials with multiple functionalities stemming from the unusual materials combinations. This review focuses on recent advances in the area of semiconductor–metal hybrid nanoparticles. Synthesis approaches offering high degree of control over the number of components, their compositions, shapes, and interfacial characteristics are discussed, including examples of advanced architectures. Progress in hybrid nanoscale inorganic cage structures prepared by a selective edge growth mechanism of the metal onto the semiconductor nanocrystal is also presented. The combined and often synergistic properties of the hybrid nanoparticles are described with emphasis on optical properties, electronic structure, electrical characteristics, and light induced charge separation effects. Progress toward the application of hybrid nanoparticles in photocatalysis is overviewed. We conclude with a summary and point out some challenges for further development and understanding of semiconductor–metal hybrid nanoparticles. This progress shows promise for application of hybrid nanoparticles in photocatalysis, catalysis, optical components, and electronic devices.

 

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.