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News Article | September 23, 2016
Site: www.nanotech-now.com

Abstract: Researchers at Nanoscience Center of University of Jyväskylä in Finland have succeeded in producing short chains and rings of gold nanoparticles with unprecedented precision. They used a special kind of nanoparticles with a well-defined structure and linked them together with molecular bridges. These structures – being practically huge molecules – allow extremely accurate studies of light–matter interaction in metallic nanostructures and plasmonics. This research was funded by The Academy of Finland. Researchers at Nanoscience Center of University of Jyväskylä in Finland have succeeded in producing short chains and rings of gold nanoparticles with unprecedented precision. They used a special kind of nanoparticles with a well-defined structure and linked them together with molecular bridges. These structures – being practically huge molecules – allow extremely accurate studies of light–matter interaction in metallic nanostructures and plasmonics. This research was funded by The Academy of Finland. Nanotechnology gives us tools to fabricate nanometer sized particles where only a few hundred metal atoms form their core. New interesting properties emerge in this scale, for example, the light–matter interaction is extremely strong and catalytic activity increased. These properties have led to several applications, such as, chemical sensors and catalysts. “Synthesis of nanoparticles usually yields a variety of sizes and shapes”, say lecturer Dr Tanja Lahtinen. The approach we use is exceptional in the sense that after purification we get only a single type of a nanoparticle. These nanoparticles have a specified number of each atom and the atoms are organized as a well-defined structure. It is essentially a single huge molecule with a core of gold. These nanoparticles were linked wit h molecular bridges forming pairs, chains, and rings of nanoparticles. “When these kind of nanostructures interact with light, electron clouds of the neighboring metal cores become coupled”, explains researcher Dr Eero Hulkko. The coupling alters significantly the electric field what molecules in between the particles feel. “Studying nanostructures that are well-defined at the atomic level allows us to combine experimental and computational methods in a seemless way”, continues Dr Lauri Lehtovaara, Research Fellow of the Finnish Academy. We are aiming to understand light–matter interaction in linked metallic nanostructures at the quantum level. Deeper understanding is essential for development of novel plasmonic applications. The research continues a long-term multidispilinary collaboration at Nanoscience Center of University of Jyväskylä. “I am very happy that our dedicated efforts on studying monolayer protected clusters and their applications have created an unique multidisiplinary center of excellence which is able to continuously publish high impact science”, says Hannu Häkkinen, an Academy Professor and head of the Nanoscience Center. In addition to the above persons, Karolina Sokołowska, Dr Tiia-Riikka Tero, Ville Saarnio, Dr Johan Lindgren, and Prof Mika Pettersson contributed to the research. The research was published in the Nanoscale on xx.9.2016. Computational resources were supplied by CSC - IT Center for Science. About Suomen Akatemia (Academy of Finland) The Academy of Finland’s mission is to fund high-quality scientific research, provide expertise in science and science policy, and strengthen the position of science and research. We are an agency within the administrative branch of the Finnish Ministry of Education, Science and Culture. We work to contribute to the renewal, diversification and increasing internationalisation of Finnish research. Our activities cover the full spectrum of scientific disciplines. We support and facilitate researcher training and research careers, internationalisation and the application of research results. We are also keen to emphasise the importance of research impact and breakthrough research. We therefore encourage researchers to submit boundary-crossing applications that involve risks but also offer promise and potential for scientifically significant breakthroughs. Our funding for research amounts to 310 million euros in 2014. Each year, our funding contributes to some 8,000 people’s work at universities and research institutes in Finland. For more information, please click If you have a comment, please us. Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.


Figure: Upper row: (a) top and (b) side view of the 136-atom silver nanocluster. Lower row: (c) top and (d) side view of the 374-atom silver nanocluster. The metal cores of these clusters have a diameter of 2 and 3 nm, respectively. Silver atoms in the metal core are denoted by large orange sphere. The core is protected by a silver-thiol layer (green: silver; yellow: sulfur; carbon: gray). Credit: Courtesy of Nanfeng Zheng, Xiamen University A wide international collaboration involving researchers from four countries – China, Australia, Germany and Finland – have managed to synthesize and characterize two previously unknown, record-large silver nanoclusters of 136 and 374 silver atoms. These diamond-shaped nanoclusters (see Figure), consisting of a silver core of 2 to 3 nanometers and a protecting layer of silver atoms and organic thiol molecules, are the largest ones whose structure is now known to atomic precision. The research was published in Nature Communications on 9 September 2016. The nanoclusters where synthesized in Xiamen University in China and characterized by X-ray crystallography and electron microscopy in China, Australia and Germany. Their electronic structure and optical properties were studied computationally in the Nanoscience Center (NSC) of the University of Jyväskylä in Finland. Gold nanoclusters that are stabilized by a thiol molecular layer have been known for decades, but only during the latest years silver clusters have attracted more interest in the research community. Silver is a desirable material for nanocluster synthesis since it is a cheaper metal than gold and its optical properties are better controllable for applications. However, synthesis recipes that would produce silver clusters that are stable for prolonged times are not so widely known as for gold. "These largest atomically precise silver nanoclusters known thus far serve as excellent model systems to understand how silver nanoparticles grow," says Professor Nanfeng Zheng whose research group prepared the clusters in Xiamen University in China. "The internal structure of the metal core is a combination of little crystallites of silver that are joined together to form a five-fold symmetric diamond-shape structure." "From a theoretical point of view these new clusters are very interesting," says Academy Professor Hannu Häkkinen from the NSC in Jyväskylä. "These clusters are already big enough that they have properties similar to silver metal, such as strong absorption of light leading to collective oscillations of the electron cloud known as plasmons, yet small enough that we can study their electronic structure in detail. Much to our surprise, the calculations showed that electrons in the organic molecular layer take part actively in the collective oscillation of the silver electrons. It seems possible to then activate these clusters by light in order to do chemistry at the ligand surface." Explore further: New breakthrough for structural characterization of metal nanoparticles More information: H. Yang, Y. Wang, X. Chen, X. Zhao, L. Gu, H. Huang, J. Yan, C. Xu, G. Li, J. Wu, A.J. Edwards, B. Dittrich, Z. Tang, D. Wang, L. Lehtovaara, H. Häkkinen and N. Zheng, "Plasmonic twinned silver nanoparticles with molecular precision", Nature Communications 7, 12809 (2016), published online 9 September 2016, doi: 10.1038/ncomms12809


News Article | October 13, 2016
Site: phys.org

The DNA itself has no part in the electrical function, but acts as a scaffold for forming a linear, pearl-necklace-like nanostructure consisting of three gold nanoparticles. Credit: the University of Jyväskylä Nature has inspired generations of people, offering a plethora of different materials for innovations. One such material is the molecule of the heritage, or DNA, thanks to its unique self-assembling properties. Researchers at the Nanoscience Center (NSC) of the University of Jyväskylä and BioMediTech (BMT) of the University of Tampere have now demonstrated a method to fabricate electronic devices by using DNA. The DNA itself has no part in the electrical function, but acts as a scaffold for forming a linear, pearl-necklace-like nanostructure consisting of three gold nanoparticles. The nature of electrical conduction in nanoscale materials can differ vastly from regular, macroscale metallic structures, which have countless free electrons forming the current, thus making any effect by a single electron negligible. However, even the addition of a single electron into a nanoscale piece of metal can increase its energy enough to prevent conduction. This kind of addition of electrons usually happens via a quantum-mechanical effect called tunnelling, where electrons tunnel through an energy barrier. In this study, the electrons tunnelled from the electrode connected to a voltage source, to the first nanoparticle and onwards to the next particle and so on, through the gaps between them. "Such single-electron devices have been fabricated within the scale of tens of nanometres by using conventional micro- and nanofabrication methods for more than two decades," says Senior Lecturer Jussi Toppari from the NSC. Toppari has studied these structures already in his PhD work. "The weakness of these structures has been the cryogenic temperatures needed for them to work. Usually, the operation temperature of these devices scales up as the size of the components decreases. Our ultimate aim is to have the devices working at room temperature, which is hardly possible for conventional nanofabrication methods - so new venues need to be found." Modern nanotechnology provides tools to fabricate metallic nanoparticles with the size of only a few nanometres. Single-electron devices fabricated from these metallic nanoparticles could function all the way up to room temperature. The NSC has long experience of fabricating such nanoparticles. "After fabrication, the nanoparticles float in an aqueous solution and need to be organised into the desired form and connected to the auxiliary circuitry," explains researcher Kosti Tapio. "DNA-based self-assembly together with its ability to be linked with nanoparticles offer a very suitable toolkit for this purpose." Gold nanoparticles are attached directly within the aqueous solution onto a DNA structure designed and previously tested by the involved groups. The whole process is based on DNA self-assembly, and yields countless of structures within a single patch. Ready structures are further trapped for measurements by electric fields. "The superior self-assembly properties of the DNA, together with its mature fabrication and modification techniques, offer a vast variety of possibilities," says Associate Professor Vesa Hytönen. Electrical measurements carried out in this study demonstrated for the first time that these scalable fabrication methods based on DNA self-assembly can be efficiently utilised to fabricate single-electron devices that work at room temperature. The research builds on a long-term multidisciplinary collaboration between the research groups involved. In addition to the above persons, Dr Jenni Leppiniemi (BMT), Boxuan Shen (NSC), and Dr Wolfgang Fritzsche (IPHT, Jena, Germany) contributed to the research. The study was published on 13 October 2016 in Nano Letters. Collaborative travel funding was obtained from DAAD in Germany. Explore further: Chains of nanogold – forged with atomic precision More information: Kosti Tapio et al, Toward Single Electron Nanoelectronics Using Self-Assembled DNA Structure, Nano Letters (2016). DOI: 10.1021/acs.nanolett.6b02378


News Article | September 9, 2016
Site: www.nanotech-now.com

Abstract: A wide international collaboration involving researchers from four countries - China, Australia, Germany and Finland - have managed to synthesize and characterize two previously unknown, record-large silver nanoclusters of 136 and 374 silver atoms. These diamond-shaped nanoclusters (see Figure), consisting of a silver core of 2 to 3 nanometers and a protecting layer of silver atoms and organic thiol molecules, are the largest ones whose structure is now known to atomic precision. The research (1) was published in Nature Communications on 9 September 2016. The nanoclusters where synthesized in Xiamen University in China and characterized by X-ray crystallography and electron microscopy in China, Australia and Germany. Their electronic structure and optical properties were studied computationally in the Nanoscience Center (NSC) of the University of Jyväskylä in Finland. Gold nanoclusters that are stabilized by a thiol molecular layer have been known for decades, but only during the latest years silver clusters have attracted more interest in the research community. Silver is a desirable material for nanocluster synthesis since it is a cheaper metal than gold and its optical properties are better controllable for applications. However, synthesis recipes that would produce silver clusters that are stable for prolonged times are not so widely known as for gold. "These largest atomically precise silver nanoclusters known thus far serve as excellent model systems to understand how silver nanoparticles grow," says Professor Nanfeng Zheng whose research group prepared the clusters in Xiamen University in China. "The internal structure of the metal core is a combination of little crystallites of silver that are joined together to form a five-fold symmetric diamond-shape structure." "From a theoretical point of view these new clusters are very interesting," says Academy Professor Hannu Häkkinen from the NSC in Jyväskylä. "These clusters are already big enough that they have properties similar to silver metal, such as strong absorption of light leading to collective oscillations of the electron cloud known as plasmons, yet small enough that we can study their electronic structure in detail. Much to our surprise, the calculations showed that electrons in the organic molecular layer take part actively in the collective oscillation of the silver electrons. It seems possible to then activate these clusters by light in order to do chemistry at the ligand surface." ### The other NSC researchers involved in the work were Xi Chen and Lauri Lehtovaara. The computational work was done at the CSC - the Finnish IT Centre for Science. The work at the University of Jyväskylä was supported by the Academy of Finland. For more information, please click If you have a comment, please us. Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.


News Article | September 22, 2016
Site: phys.org

Researchers at Nanoscience Center of University of Jyväskylä in Finland have succeeded in producing short chains and rings of gold nanoparticles with unprecedented precision. They used a special kind of nanoparticles with a well-defined structure and linked them together with molecular bridges. These structures – being practically huge molecules – allow extremely accurate studies of light–matter interaction in metallic nanostructures and plasmonics. This research was funded by the Academy of Finland.


News Article | January 21, 2016
Site: phys.org

The proton NMR spectrum originating from the ligand layer of the Au102 nanoparticle in water (left). The spectrum has been fully interpreted by assigning the observed signals (peaks) to all of the 22 symmetry-unique thiol ligands numbered in the solid state structure of the Au102 particle (right). From ref. 1. Researchers at the University of Jyväskylä, Finland, and Colorado State University, USA, have for the first time ever determined the dynamical behaviour of the ligand layer of a water-soluble gold nanocluster in solution. The breakthrough opens a way towards controllable strategies for the functionalisation of ligated nanoparticles for applications. The work at the University of Jyväskylä was supported by the Academy of Finland. The research was published in Nature Communications on 21 January 2016. Nanometre-scale gold particles are intensively investigated for applications as catalysts, sensors, drug delivery devices and biological contrast agents and as components in photonics and molecular electronics. The smallest particles have metal cores of only 1–2 nm with a few tens to a couple of hundred gold atoms. Their metal cores are covered by a stabilising organic ligand layer. The molecular formulas and solid-state atomic structure of many of these compounds, called "clusters", have been resolved during the past few years. Still, it is a considerable challenge to understand their atomic-scale structure and dynamical behaviour in the solution phase. This is crucial information that can help researchers understand how nanoclusters interact with the environment. The researchers studied a previously identified molecularly precise nanocluster that has 102 gold atoms and 44 thiol ligands (Figure 1, right). The solid-state structure of this cluster was resolved from single-crystal X-ray diffraction experiments in 2007. The ligand shell has a low symmetry and produces a large number of signals in conventional proton-NMR measurement (Figure 1, left). The researchers achieved a full assignment of all signals to specific thiol ligands by using a combination of correlated nuclear magnetic resonance (NMR) experiments, density functional theory computations and molecular dynamics simulations. The Finnish researchers at Jyväskylä have previously used this specific cluster material, for instance, for structural studies of enteroviruses. "Now that we know exactly which ligand produces which NMR signal, we can proceed with precise studies on how this nanocluster interacts with the chemical and biological environment in the water phase. This gives unprecedented potential to understand and control the inorganic-organic interfaces that are relevant to hybrid inorganic-biological materials," says Academy Professor Hannu Häkkinen from the Nanoscience Center at the University of Jyväskylä. Häkkinen coordinated the work of the Finnish-US team. More information: Kirsi Salorinne et al. Conformation and dynamics of the ligand shell of a water-soluble Au102 nanoparticle, Nature Communications (2016). DOI: 10.1038/ncomms10401


News Article | September 22, 2016
Site: www.cemag.us

Researchers at the Nanoscience Center of the University of Jyväskylä in Finland have succeeded in producing short chains and rings of gold nanoparticles with unprecedented precision. The researchers used special kinds of nanoparticles with a well-defined structure and linked them together with molecular bridges. These structures — practically huge molecules — allow for extremely accurate studies of light-matter interaction in metallic nanostructures and plasmonics. The research was funded by the Academy of Finland. Nanotechnology gives us tools to fabricate nanometer-sized particles where only a few hundred metal atoms form their core. New interesting properties emerge in this scale. For example, the light-matter interaction is extremely strong and catalytic activity increases. These properties have led to several applications, such as, chemical sensors and catalysts. “Synthesis of nanoparticles usually yields a variety of sizes and shapes,” says lecturer Dr. Tanja Lahtinen. "The approach we use is exceptional in the sense that after purification we get only a single type of a nanoparticle. These nanoparticles have a specified number of each atom and the atoms are organized as a well-defined structure. It's essentially a single huge molecule with a core of gold." The nanoparticles were linked with molecular bridges forming pairs, chains, and rings of nanoparticles. “When these kinds of nanostructures interact with light, electron clouds of the neighboring metal cores become coupled,” explains researcher Dr. Eero Hulkko. The coupling significantly alters the electric field that molecules between the particles feel. “Studying nanostructures that are well-defined at the atomic level allows us to combine experimental and computational methods in a seamless way,” adds Academy Research Fellow Dr. Lauri Lehtovaara. "We're aiming to understand light-matter interaction in linked metallic nanostructures at the quantum level. Deeper understanding is essential for development of novel plasmonic applications." The research builds on a long-term multidisciplinary collaboration at the Nanoscience Center of the University of Jyväskylä. “I'm very happy that our dedicated efforts on studying monolayer protected clusters and their applications have created a unique multidisciplinary center of excellence that is able to continuously publish high-impact science,” says Academy Professor Hannu Häkkinen, head of the Nanoscience Center. In addition to the above persons, Karolina Sokołowska, Dr. Tiia-Riikka Tero, Ville Saarnio, Dr. Johan Lindgren, and Professor Mika Pettersson contributed to the research. The research was published in the Nanoscale journal on Sept. 21. Computational resources were supplied by CSC — IT Center for Science.


News Article | January 22, 2016
Site: www.cemag.us

Researchers at the University of Jyväskylä and Colorado State University have for the first time ever determined the dynamical behavior of the ligand layer of a water-soluble gold nanocluster in solution. The breakthrough opens a way towards controllable strategies for the functionalization of ligated nanoparticles for applications. The work at the University of Jyväskylä was supported by the Academy of Finland. The research was published in Nature Communications this week. Nanometer-scale gold particles are intensively investigated for applications as catalysts, sensors, drug delivery devices and biological contrast agents and as components in photonics and molecular electronics. The smallest particles have metal cores of only 1 to 2 nm with a few tens to a couple of hundred gold atoms. Their metal cores are covered by a stabilizing organic ligand layer. The molecular formulas and solid-state atomic structure of many of these compounds, called “clusters,” have been resolved during the past few years. Still, it is a considerable challenge to understand their atomic-scale structure and dynamical behavior in the solution phase. This is crucial information that can help researchers understand how nanoclusters interact with the environment. The researchers studied a previously identified molecularly precise nanocluster that has 102 gold atoms and 44 thiol ligands. The solid-state structure of this cluster was resolved from single-crystal X-ray diffraction experiments in 2007. The ligand shell has a low symmetry and produces a large number of signals in conventional proton-NMR measurement. The researchers achieved a full assignment of all signals to specific thiol ligands by using a combination of correlated nuclear magnetic resonance (NMR) experiments, density functional theory computations and molecular dynamics simulations.   The Finnish researchers at Jyväskylä have previously used this specific cluster material, for instance, for structural studies of enteroviruses. “Now that we know exactly which ligand produces which NMR signal, we can proceed with precise studies on how this nanocluster interacts with the chemical and biological environment in the water phase. This gives unprecedented potential to understand and control the inorganic-organic interfaces that are relevant to hybrid inorganic-biological materials,” says Academy Professor Hannu Häkkinen from the Nanoscience Center at the University of Jyväskylä. Häkkinen coordinated the work of the Finnish-U.S. team. The researchers involved in the work are Kirsi Salorinne, Sami Malola, Xi Chen, and Hannu Häkkinen from the University of Jyväskylä, and O. Andrea Wong, Christopher D. Rithner, and Christopher J. Ackerson from Colorado State University. The computational work was done at the CSC — the Finnish IT Centre for Science.  Release Date: January 21, 2016 Source: Academy of Finland


News Article | February 15, 2017
Site: phys.org

Considerable research into perovskites at NREL and elsewhere has proved the material's effectiveness at converting sunlight into electricity, routinely topping 20 percent efficiency. The sunlight creates mobile electrons whose movement generates the power but upon encountering defects can slip into a non-productive process. Known as a recombination, this process reduces the efficiency of a solar cell. For the cell to be the most efficient, the recombination must occur slowly. With prior studies into perovskites focusing on bulk recombination, one area left unexamined until now concerned the surface recombination in lead iodide perovskites. NREL's scientists determined recombination in other parts of a methylammonium perovskite film isn't as important as what's happening on the surface, both the top and bottom. Matthew Beard and his colleagues within NREL's Chemistry and Nanoscience Center studied surface recombination in single-crystal and polycrystalline films using transient reflection spectroscopy. Their findings, Top and bottom surfaces limit carrier lifetime in lead iodide perovskite films, appear in Nature Energy. "What's important is to know where the recombination is coming from," said Beard, lead author of the research paper. "There are multiple sources of possible recombination. In order to improve your device, you're asked to get rid of all non-radiative recombination. Typically people forget about surfaces. They think about grain boundaries. They think about bulk defects and so forth." Beard's co-authors are all from NREL: Ye Yang, Mengjin Yang, David T. Moore, Yong Yan, Elisa M. Miller, and Kai Zhu. Beard said the research determined surface recombination emerged as an obstacle to overcome. Surface recombination directly affects the performance of a photovoltaic device. The ability to engineer surfaces stands poised to benefit perovskite-based optoelectronic applications. A fast surface recombination can be used to design photodetectors, while lasers and light-emitting diodes require a slower speed. A second study that concurrently appeared in the journal Physical Chemistry Chemical Physics was authored by Mengjin Yang, Yining Zeng, Zhen Li, DongHoe Kim, Chun-Sheng Jiang, Jao van de Lagemaat, and Kai Zhu further strengthened the conclusions of the Nature Energy paper. This study, using high-resolution fluorescence-lifetime imaging, also showed that surface recombination is the determining factor instead of grain boundary recombination. The researchers compared two types of samples: single crystals and polycrystalline films. Surprisingly surface recombination is worse for single crystalline samples compared to the polycrystalline samples found in solar cell devices. Chemically, excess methylammonium iodide was present on the surface of the polycrystalline film but absent on the single-crystal sample. "That seems to help," Beard said. "The single crystal has a lead-rich surface and a faster surface recombination." The research suggested a light coating of a protective material on the surface of the polycrystalline thin films could further improve the performance of perovskite solar cells. More information: Mengjin Yang et al. Do Grain Boundaries Dominate Non-Radiative Recombination in CHNHPbIPerovskite Thin Films?, Phys. Chem. Chem. Phys. (2017). DOI: 10.1039/C6CP08770A Ye Yang et al. Top and bottom surfaces limit carrier lifetime in lead iodide perovskite films, Nature Energy (2017). DOI: 10.1038/nenergy.2016.207


News Article | August 24, 2016
Site: www.cemag.us

Yale University physicist Leonid Glazman has developed a quantitative theory to explain the effect of quantum and thermal fluctuations of charge in tiny “electron puddles” for a study reported in the journal Nature. Scientists at the Nanoscience Center in Paris have created an “electron puddle” within a semiconductor in order to study the particle-wave duality in the nature of electrons.

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