Interviews with plenary speakers of the XV Brazil-MRS Meeting: Paul S. Weiss (UCLA, USA).

Posted on Thursday 15 de September de 2016

Taking precise measurements of atoms and molecules. Accurately control molecules so that they form specific nanostructures or work together to achieve desired results. The nanoscientist Paul Weiss will address this and much more at the XV Brazil-MRS Meeting. Weiss is Professor at the University of California, Los Angeles (UCLA) and editor-in-chief of ACS Nano journal. At the annual SBPMat event, in addition to delivering the plenary lecture, Weiss will also participate in a roundtable to discuss scientific publication along with the public and editors of other journals.

Paul Weiss received his S.B and S.M degrees in Chemistry from the Massachusetts Institute of Technology in 1980, after conducting research in high-resolution laser spectroscopy. His doctoral research, also in Chemistry at the University of California at Berkeley, was about excited atom reactions in crossed molecular beams.

In 1986, the year he concluded his PhD, his advisor, Yuan T. Lee, was awarded the Nobel Prize in Chemistry for his contribution to the study of the dynamics of chemical elementary processes. Soon after his doctorate, Weiss began working at Bell Laboratories as a post-doc studying the effects of surface chemistry and gas-surface collisions on semiconductor surface electronic properties. In 1988, he worked at IBM Almaden Research Center, where he remained as a visiting scientist until the following year. There his work was on scanning tunneling microscopy (STM) with one of the STM pioneers, Donald Eigler. STM, which lead to a major breakthrough in nanotechnology by enabling the manipulation of individual atoms and molecules, would become one of Weiss’s favorite techniques.

In 1989, Weiss joined the faculty of Pennsylvania State University (PennState), where he continued his work with STM, expanding the technique and studying atoms and molecules. From 2001 to 2002 he was the director of the Center for Molecular Nanofabrication and Devices of PennState. In 2005 he was designated Distinguished Professor of Chemistry and Physics departments at the university.

It was also at PennState that Weiss met the scientist Anne Andrews, with whom he is married to this day. Andrews was responsible for convincing Weiss to apply his expertise and knowledge on nanoscience in the study of the human brain. In this field, and in collaboration with Andrews and other scientists, Weiss has been committed to developing tools to study the interactions between neurons, which take place through electrical and chemical signals in nanometric spaces.

Concomitantly, Paul Weiss participated in the creation of the scientific journal ACS Nano (2015 impact factor of 13,334) and has been editor in chief since the journal’s first edition, published in August 2007. In 2008, the journal received a major distinction, the PROSE Award for Best New Journal in Science, Technology, and Medicine from the Association of American Publishers.

In 2009, he joined the University of California, Los Angeles (UCLA), where he was named Distinguished Professor of Chemistry & Biochemistry. Furthermore, he received, until 2014, the Fred Kavli Chair in Nanosystems Sciences and the directorship of the California NanoSystems Institute, a multidisciplinary institute of research and innovation in nanoscience and nanotechnology. Weiss has also been leading at UCLA a research group that gathers together chemists, physicists, biologists, materials scientists, electrical and mechanical engineers and computer scientists.

Paul Weiss was a visiting professor at the University of Washington (1996 – 1997) and at Kyoto University (1998 and 2000). In 2015, he was Distinguished Visiting Professor at the California Institute of Technology, and Visiting Scholar at Harvard University.

Paul Weiss has published over 300 papers and has approximately 20 patents. According to Google Scholar he has an h-index of 60 and more than 16,000 citations. He has given over 600 invited, plenary, keynote, and named lectures. Weiss has received many awards and distinctions for his research, teaching and scientific publishing. He is an elected senior fellow of IEEE, an elected fellow of the American Chemical Society, the American Physical Society, the American Association for the Advancement of Science, and the American Vacuum Society, and an honorary fellow of the Chinese Chemical Society.

He is currently Distinguished Professor in the Department of Chemistry & Biochemistry and the Department of Materials Science & Engineering at UCLA. He is also Visiting Professor at Nanyang Technological University and continues to work as editor in chief of ACS Nano. Paul S. Weiss also holds a UC Presidential Chair at UCLA.

Here is a brief interview with this speaker of the XV Brazil-MRS Meeting:

SBPMat newsletter: – In your opinion, what are your main contributions on the themes of your plenary lecture? Could you also share with us a couple of references pertaining to publications on these subjects?

Paul Weiss: – In our work, we explore the ultimate limits of miniaturization. We have assembled and operated the smallest switches and motors in the world. To do that, we have put together two sets of capabilities. First, we designed and applied new microscopes and microscopies that can simultaneously measure structure, function, and spectra, with submolecular resolution. In the other, we have developed the ability to place individual molecules into precisely controlled environments. We combine these to understand functional mechanisms and to design new molecules and assemblies to test our ideas.

Try these papers:

Controlling Motion at the Nanoscale: Rise of the Molecular Machines, J. M. Abendroth, O. S. Bushuyev, P. S. Weiss, and C. J. Barrett, ACS Nano 9, 7746 (2015). (Abstract or Article or PDF)

Molecular Switches and Motors on Surfaces, B. K. Pathem, S. A. Claridge, Y. B. Zheng, and P. S. Weiss, Annual Review of Physical Chemistry 64, 605 (2013). (Abstract or PDF)

From the Bottom Up: Dimensional Control and Characterization in Molecular Monolayers, S. A. Claridge, W.-S. Liao, J. C. Thomas, Y. Zhao, H. Cao, S. Cheunkar, A. C. Serino, A. M. Andrews, and P. S. Weiss, Chemical Society Reviews 42, 2725 (2013). (Abstract or Article or PDF)

SBPMat newsletter: – You are part of the team that created ACS Nano, launched in 2007, right? Could you tell us which elements you attribute to the success of the journal, reflected in its impact factor and the awards received

Paul Weiss: – Yes, I was the founding editor-in-chief and continue in that role.

We decided to create a forward-looking journal in which we would lay out the challenges and opportunities for the field, in order to guide and to accelerate advances. We felt that while there are many journals that published communications in nanoscience and nanotechnology, there was not a strong journal that published comprehensive work, on which others could build. This situation, we decided, was holding back our field. We set out to find the most diverse set of curious editors from different fields and we set the journal up to be extremely fast and fair to all authors. Only scientists make decisions and it takes at least two scientists to make decisions to decline manuscripts. Our editors have conversations every day on where the field is going and what are true advances. We have made it intellectually stimulating for ourselves and we believe also for our readers. The result is that we can see the real impact on the worlds of science, engineering, medicine, and beyond. We published the technology roadmaps proposing the BRAIN Initiative in the US and beyond and the new Microbiome Initiative. Stay tuned for more!

Nanotools for Neuroscience and Brain Activity Mapping, A. P. Alivisatos, A. M. Andrews, E. S. Boyden, M. Chun, G. M. Church, K. Deisseroth, J. P. Donoghue, S. E. Fraser, J. Lippincott-Schwartz, L. L. Looger, S. Masmanidis, P. L. McEuen, A. V. Nurmikko, H. Park, D. S. Peterka, C. Reid, M. L. Roukes, A. Scherer, T. J. Sejnowski, K. L. Shepard, D. Tsao, G. Turrigiano, P. S. Weiss, C. Xu, R. Yuste, and X. Zhuang, ACS Nano 7, 1850 (2013). (Abstract or Article or PDF)

Tools for the Microbiome: Nano and Beyond, J. S. Biteen, P. C. Blainey, M. Chun, G. M. Church, P. C. Dorrestein, S. E. Fraser, J. A. Gilbert, J. K. Jansson, R. Knight, J. F. Miller, A. Ozcan, K. A. Prather, E. G. Ruby, P. A. Silver, S. Taha, G. van den Engh, P. S. Weiss, G. C. L. Wong, A. T. Wright, and T. D. Young, ACS Nano 10, 6 (2016). (Abstract or Article orPDF)

SBPMat newsletter: – Please leave an invitation to our readers to attend your plenary lecture “Cooperative Function in Atomically Precise Nanoscale Assemblies” in the XV Brazil-MRS Meeting.

Paul Weiss: – I hope you will join me at the XV Brazil-MRS Meeting for a discussion of how we can explore and understand function at the nanoscale and what it teaches us about the world around us.

Link to the abstract of the XV B-MRS Meeting plenary talk “Cooperative Function in Atomically Precise Nanoscale Assemblies”: http://sbpmat.org.br/15encontro/speakers/abstracts/3.pdf

Interviews with plenary speakers of the XIV SBPMat Meeting: Ulrike Diebold.

Posted on Wednesday 3 de June de 2015

Metal oxides display a wide range of properties. Accordingly, they become useful in numerous applications, such as gas sensing, catalysis, protection against corrosion, pigmentation, energy conversion, to name a few. An important detail: in order to comprehend and use these materials, the study of their surface is crucial.

Metal oxides surfaces will be the theme of a plenary talk of the XIV SBPMat Meeting. The speech will be given by Ulrike Diebold, a scientist among the leading experts on the subject in the world. Diebold is engaged in surface science since the time of her doctoral degree, defended in 1990 at the Vienna University of Technology (TU Wien), in Austria. A few years later, during her postdoctoral studies in a surface group at Rutgers University, in New Jersey (USA), she started her researches on titanium dioxide. In 1993, she became a Professor of Tulane University, in the city of New Orleans (USA) and she founded and coordinated a group on surface science. When the group labs were hit by hurricane Katrina in 2005, Diebold was welcomed by several institutions and settled, jointly with some members of the Tulane group, in Rutgers. Finally, she went back to the place where her scientific career had started, TU Wien, as a Professor and coordinator of the surface physics group. With her research groups, Diebold continues to advance in her basic and applied science studies on metal oxides, based, among other techniques, on scanning tunneling microscopy (STM), through which the scientist can investigate these materials at atomic scale.

Ulrike Diebold is the author of more than 180 peer-reviewed articles, which have over 12,000 citations. Her h-index, according to Web of Science, is 52. The scientist has already delivered more than 250 invited talks. Throughout her career, she has received numerous awards and distinctions from several entities such as the Alexander von Humboldt Foundation, American Chemical Society, Austrian Academy of Sciences, Austrian Ministry for Science, Catalysis Society of South Africa, Czech Republic Academy of Sciences, European Academy of Sciences, German National Academy of Sciences Leopoldina, National Science Foundation, among others. She is an associate editor for the Materials Physics Division of the journal Physical Review Letters.

What follows is a mini-interview with this plenary speaker of the XIV SBPMat Meeting

Abb5_gold — STM image of single Au atoms on an Fe3O4 surface. This system acts as a model catalyst to study simple reactions with atomic-scale detail. The related experiment is described in: Novotný, Z. et al. Ordered Array of Single Adatoms with Remarkable Thermal Stability: Au/Fe_{3}O_{4}(001). Phys Rev Lett 108, (2012).

SBPMat newsletter: – In your opinion, what are your most significant contributions in the field of metal oxides surfaces? Please explain them, very briefly, and share references from the resulting articles or books, or comment if these studies have produced patents or products.

Ulrike Diebold: – The field started with the book “The Surface Science of Metal Oxides” by Vic Henrich and P.A. Cox, which was published in 1993 (Cambridge University Press). The book has motivated many people to develop an interest in metal oxide surfaces, and research has progressed tremendously since that time. Some is still valid to this day, e.g., the importance of defects for understanding the properties of oxide surfaces, and how critical it is to master surface preparation. Meaningful investigations can only be conducted on ‘well-characterized’ systems with a known and controlled surface structure. About ten years later, in 2003, I wrote a review that focused only on titanium dioxide, which is a widely-used material both in applications and in fundamental research (Surface Science Reports 48 (2003) 53). This review has received quite a bit of attention. Another decade later a whole issue of Chemical Reviews (vol. 113, 2013) was focused on metal oxide surfaces, which pretty much summarizes the state-of-the art in metal oxide surface research.

SBPMat newsletter: – Comment on the possibilities offered by tunneling microscopy to the study of surfaces, especially metal oxides surfaces.

Ulrike Diebold: – Scanning Tunneling Microscopy, which was invented by Heinrich Rohrer and Gerd Binnig in the early 1980s, has revolutionized our understanding of the nanoworld. One can use this technique for imaging the geometric and electronic structure of a surface at the local scale, atom-by-atom. This is particularly important for oxides, where it is often the irregularities in the lattice that are the most interesting entities, i.e., defects such as missing atoms, interstitials, or impurities. Scanning Tunneling Microscopy is the ideal tool to investigate such defects at the atomic level and to literally ‘watch’ defect-mediated chemical reactions.

Abb2_Defects — STM image of defects on a TiO2 surface. The related experiment is described in Dulub, O. et al. Electron-induced oxygen desorption from the TiO2(011)-2×1 surface leads to self-organized vacancies. Science 317, 1052–1056 (2007).

SBPMat newsletter: – If you wish, leave a message or an invitation to your plenary talk to the readers who will attend the XIV SBPMat Meeting.

Ulrike Diebold: – I think it is simply exciting to observe phenomena such as defects disappearing from a surface and coming back, or single molecules dissociating or diffusing across a surface. If you want to see beautiful pictures and movies of processes that could potentially be relevant to your own research, please come to my talk.

More

Featured paper: Luminescence measurements to identify defects in zinc oxide thin films.

Posted on Thursday 27 de February de 2014

The scientific paper by members of the Brazilian community in Materials research featured this month is:

Fernando Stavale, Niklas Nilius, and Hans-Joachim Freund. STM Luminescence Spectroscopy of Intrinsic Defects in ZnO(0001̅) Thin Films. J. Phys. Chem. Lett., 2013, 4 (22), pp 3972–3976. DOI: 10.1021/jz401823c.

Luminescence measurements to identify defects in zinc oxide thin films.

Zinc oxide (ZnO) is a very common material in everyday life. It can be found in screws, sunscreen, catalyzer for methanol synthesis and sophisticated optoelectronic devices, such as computer flexible screens, to name just a few. However, in order to enable some promising applications, such as transistors and new devices, it is important to control electrical properties of this semiconductor material, which are related to specific defects in its atomic structure.

Within this context, three scientists from institutions in Germany and Brazil identified specific defects in zinc oxide films through an original approach, taking advantage of luminescence capability (emission of light not resulting from heat) of zinc oxide. Researchers prepared zinc oxide thin films with different types and amounts of specific defects. Systematically, scientists measured luminescence of each film and, thus, they managed to relate peaks on the measurements with various types of defects in crystal nets. The results of this study were published in periodical The Journal of Physical Chemistry Letters (JPCL).

“In this study, we developed extremely high quality thin films of zinc oxide and we altered the amount of specific defects using thermal desorption, photo-desorption induced by laser and reduction by treatment in hydrogen controlled environment” – says Fernando Stavale, researcher for Centro Brasileiro de Pesquisas Físicas (CBPF), who signs the article as main author.

Characterization technique

In order to make the experiments, scientists used a scanning tunneling microscope (STM) in ultra high vacuum with a few peculiarities designed to generate luminescence, collect the emitted photons and obtain the measurements (spectrum) of luminescence. With this configuration, the STM is known as photon-scanning tunneling microscope. According to Stavale, one of the main scientists in the field of development and application of this technique is Professor Niklas Nilius, correspondent author of the JPCL paper, with whom Stavale has directly worked for three years during his post-doctoral research at Fritz-Haber Max-Planck Society, in Berlin, specifically at Physico-chemical Department led by Professor Hans-Joachim Freund, last author of the JPCL article. “The photon-scanning tunneling microscope has been employed in unprecedented manner to characterize metallic acids at the department directed by Professor Freund” – says Stavale. “The technique is still underused in Brazil and it is an essential part of the projects I develop with my research team at CBPF, situated in Rio de Janeiro” – he adds.

One of the most important features in photon-scanning tunneling microscopy is the use of electrons which are emitted by the tip of the STM to excite samples and, in the case of zinc oxide, to generate the desired luminescence. This phenomenon of emitting light generated by the impact of electrons over the material is called cathodoluminescence.

Experiment scheme in which the tip of the tunneling microscope can be observed, in the photo, exciting the zinc oxide film. The graph shows a spectrum of the oxide cathodoluminescence. At the back , the tunneling microscopy image of a zinc oxide film, with density of 20 layers (~5 nm) shows monoatomic steps and specific defects in the film’s surface. Vacancies of oxygen and zinc, specific defects, correspond to the areas indicated by arrows. The dark areas with hexagonal shape correspond to the areas where the film is noncontinuous, with depth of up to eight atomic layers.

This systematic work allowed scientists to infer that some peaks of luminescence of zinc oxide are due to defects such as vacancies of oxygen and zinc (dots in the lattice containing “vacancies”, instead of the expected oxygen and zinc atoms). “These specific defects are related to electrical properties often observed in zinc oxide, known as n-type doping” – Stavale adds.

The context of the work

The experiments of the JPCL article were conceived and conducted by Brazilian national Fernando Stavale in 2012, during his last year of post-doctoratal research with the group led by Professor Nilius, at Fritz-Haber of Max-Planck Society. Stavale joined the group in 2010 with financial support from Humboldt Institute in Germany. “For three years we have investigated for the first time the role of several dopants, such as chromium, europium and lithium in zinc and magnesium oxides, combined with ultra-thin films, raised in ultra-high vacuum with tunneling microscopy and local cathodoluminescence” – says Stavale about his post-doctoral studies.

The interpretation of results and the JPCL article redaction were performed in 2013 when Fernando Stavale became a CBPF researcher and Niklas Nilius became a Professor at University of Oldenburg, Germany.