Bayindir Group Member Discusses Global Challenges with Nobel Laureates
Global Challenges – Opportunities for Nanotechnology, an international nanotechnology workshop organized by the Center for Nanoscience in Munich, Swiss Nanoscience Institute and ETH Zurich, was recently held on the island of Sen Servolo in Italy. Bayındır Group was represented in this prestigious event by Tural Khudiyev. The workshop was highlighted by round-table discussions with eminent researchers who pioneered in several important fields, including Gerd Binning (who received the Nobel Prize in Physics for his efforts in the development of the scanning tunneling microscope), Christoph Gerber (co-inventor of the atomic force microscope) and Jean-Marie Lehn (father of supramolecular chemistry and the recipient of the 1987 Chemistry Nobel Prize for his work on cryptands).
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Bayindir Group Mogan Lake Picnic
Bayındır Group was at Mogan Lake this weekend. With spring coming, weather warming and flowers blooming everyone’s eyes started to slip away from work to outdoors. Thus, it was not a surprise that the offer of making the next group meeting at a lakeside was welcomed with enthusiasm by all. Gölbaşı, Mogan Lake was just the place for the event with its rich natural habitat. Gölbaşı (meaning ‘lakeside’ in Turkish) is a town 20 km south of the city of Ankara. Besides the endemic ‘Sevgi Çiçeği’ (translates as ‘love flower’ and Latin name is Centaurea tchihatcheffii), Gölbaşı is home to hundreds of bird and plant species. The day started lively with everyone joining the volleyball game and with homemade nourishments coming out. We had the chance to observe some beautiful birds of Mogan Lake such as Bahri (English name is Great Crested Greb) and Sakarmeke (English name is Coot). Kids perhaps got the most out of the day with their never-ending energies, and the number of kids indicated that Bayındır group has been productive not just in terms of research. We thank participants for this refreshing day.
Optics and Photonics News: Our work is selected in Optics 2012
Optics and Photonic News, the monthly journal of Optical Society of America (OSA), dedicates the last issue of each year to highlight the most exciting peer-reviewed optics research to have emerged over the past 12 months. Our research regarding nanowire-based photodetectors have been selected as one of the most important scientific breakthroughs in the year 2012, as published in the December 2012 issue of the journal. In this study, semiconducting nanowires were precisely aligned over metal electrodes in order to form a large area photodetection circuitry. [ Optics and Photonics News ]
[ Nanophotonics: Nanowire Sensors ]
Prestigious European Research Council Grant Awarded to Bayindir Group
Professor Mehmet BAYINDIR, asistant director of UNAM and faculty member of Physics Department, has been awarded ERC Starting Grant which was created to encourage “pioneering frontier research in any field of science, engineering and scholarship.” The ERC grant of € 1.5 million is for five years. Dr. Bayindir’s proposal focuses on the development of a novel fabrication technique (top-to-bottom iterative size reduction) in nanotechnology.
» We are looking for postdoctorial researchers/research scientists for ERC project.
Large Area Nanowire Photodetection Circuitry
Nanowires are unique among all kind of nanostructures regarding their extraordinary physical and material characteristics. Bridging the nanoscale with the macroscopic world with high throughput remains one of the biggest challenges of the nanotechnology, despite many incisive and elaborate efforts. Large scale production of ordered arrays of indefinitely long polymer encapsulated nanostructures via iterative thermal drawing by the Bayindir Research Group in 2011 could be considered as a significant step towards utilization of nanowires in macroscopic devices. Recently, we managed to produce a large area photodetection device by efficiently integrating these ordered arrays of nanowires on a photolithographically defined circuitry. The article published in Nano Letters journal, describes their innovative approach towards large scale integration of nanowires to macroscopic world in detail.
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A Novel Top-to-Bottom Fabrication Technique in Nanotechnology
Producing kilometer-long nanowire and nanotube arrays
It is not often that prefix multipliers kilo- and nano- come together; and when they do exclusively in the opening chapters of physical sciences textbooks the point being made is that the universe around us spans enourmous space and time scales while operating in unimaginably small ones. We are truly awestruck and inspired by the tension. Kilometer long nanowires do have a similar eponymous echo. The new fabrication technique, reported in Nature Materials by Bayindir research group at UNAM-National Nanotechnology Researsh Center, Bilkent University is essentially a size reduction technique. Controlled thermal size reduction is repeated iteratively until a macroscopic rod is scaled down to nano sizes radially while elongated axially. In this way a variety of semiconducting, piezoelectric and polymer nanowires and tubes can be produced. Millions of ordered indefinetely long nanowires, nanotubes, and one dimensional core-shell structures are obtained in a protective polymer. It seems fiber drawing has just been reinvented in the age of nanotechnology.
[ Read the article ] [ Nanowires without end ] [ New Frontiers in Nanofabrication ] [ Producing Kilometer-long Nanostructure ] [ Science News: New Technique Spins Superlong Nanowires ] [ Nanowerk: A new top-down nanofabrication scheme ] [ Nano Times: Nanowires and Nanotubes ] [ Nano Today: Nanowire growth stretches to extraordinary lengths ] [ Bilkent News: Nanostructures without end ]
Google search: [ nanowire nature materials bayindir ] [ nanowire nature materials yaman ] [ nanowire nature materials bilkent ]
Large Scale Nanowires Feature Structural Color
Something is of a particular hue usually because it is intrinsically that color, like the leaves of green plants. But equally likely the color of an object, small like a soap bubble or a bird feather, or immense like the firmament, appear to be of a particular color because it simply reflects (or to be precise scatters) that wavelength of light. We use the former pigment colors when we paint our rooms, or the artists paint their pictures not because pigment colors are the most appealing to the eye -structural colors are brighter and intenser- but because the structural color can not be easily obtained, or at least it was not until now. Professor Bayindir and his team report in Nano Letters that they can now produce multistructured materials with a precision and quantity that mimic certain coloring mechanisms found in nature. First of all the structures to obtain structural coloring must be smaller or of the order of the visible light wavelength, that is submicron region, the reign of nanotechnology. We regularly find such finely layered structures in nature in large sizes to be the result of self assembly and biological formation. Similar nanoscale materials has not been out of reach of humans for many decades by now, but these painstakingly made structures has almost never been large scale. (Read the rest of this entry)
Digital Photonic Nose for Machine Olfaction
Researchers at UNAM developed an infrared absorption based photonic nose that uses photonic bandgap fibers to differentiate and assign unique binary codes to odorous molecules, opening a new path for photonic based olfactory sensors.
Machine olfaction research aspires to mimic the exquisite sense of smell in mammals, using arrays of cross responsive sensors backed with sophisticated pattern recognition algorithms for the differentiation of thousands of complex odors. Each odorant, with its particular shape, size, functional group and charge combination, induces a unique combinatorial response from a library of olfactory receptors where slight differences between molecules or even a change in the concentration change its sensation. Recently, Professor Bayindir's group at UNAM developed a distinct opto-electronic nose concept, published in Advanced Materials, based on the molecular absorption of volatile organic compounds inside a hollow core photonic bandgap infrared transmitting fiber array. The sensing unit of the array is a specific fiber that is used to detect the molecular absorption level from the odorant at that specific wavelength. (Read the rest of this entry)
Highly Selective Digital Photonic Nose Technology
Electronic nose instrumentation has been at forefront of international research interest for a long time for its potential in fragrance and cosmetics production, food and beverages quality control, chemical engineering, environmental monitoring, and more recently, medical diagnostics and monitoring. In the last decade, in addition to electrical means of detecting volatile species, optical sensing mechanisms are being explored with success. Bayindir Research group at UNAM reports a highly-selective digital photonic nose technology in Analytical Chemistry. (Read the article)
Towards Tunable Metamaterials
The marriage of microfluidics and metamaterials. Electromagnetic metamaterials are of great interest due to their unusual permittivity and permeabilities. Recently negative index materials operating at microwave and THz frequencies are using wire arrays to obtain negative electric permittivity and split ring resonators (SRRs) to negative magnetic permeability. However using standard fabrication methods it is not possible to either tune or alter refractive indices from negative to positive.
In this study fabrication techniques from microfluidics is used in tuning the refractive indices of metamaterials. By fabricating SRR shaped micro-channels inside a polymer, PDMS, and by injecting a conducting liquid into the microchannels we showed that it is possible to obtain negative permeability. We are working on the fabrication of a double negative material, that exhibits both negative permeability and tunable permittivity. (Read the rest of this entry)
UNAM researchers engineer flexiable fibers for IR Lasers
UNAM researchers created an infrared fiber that can be used in hospitals for laser surgery. The fibers deliver intense laser light inside the body where it can be used to remove malignant tissues with high precision.
The specialty fibers are designed and developed fully at UNAM, which has its own fiber tower custom built for the project. After the completion of the 3.5 meter high fiber tower in August last year, the researchers are now able to draw tens of meters of photonic band gap fibers from polymer-chalcogenide glass composites.
In distinction to the regular optical fibers, these new generation fibers guide electromagnetic radiation by a dielectric mirror structure embedded inside the hollow core. The mirror structure consists of micrometer sized alternating layer materials. Also, the hollow core of the fiber enables high power laser light transmission that would easily melt solid-core fibers. (Read the rest of this entry)
All-Chalcogenide Tunable Infrared Filter
Dielectric mirrors are simple one dimensional photonic structures made using quarter wave stacks (QWS). It was recently shown that QWSs fabricated with high contrast index materials may possess full photonic band gaps (PBG) resulting in omnidirectional reﬂection. This opens up the possibility of making infrared mirror or ﬁlter design at desired wavelengths by piling suitable dielectric materials and controlling their layer thicknesses. Here, we present an infrared ﬁlter fabricated by thermal evaporation using only chalcogenide glasses. The slanted geometry gives graded layer thickness along the substrate length, resulting in a position dependent omnidirectional photonic band gap whose center shifts from 1.5 µm to 4 µm along the substrate. (Read the rest of this entry)
Nanocalorimetry: Calorimetry of Ultra-small Materials
In chemistry and materials science, the thermodynamical properties of bulk materials, such as phase transition temperatures and enthalpies, are obtained by calorimetry, making it an indispensible metrology technique. However, conventional differential scanning calorimeters require large sample mass to acquire data with reasonable accuracy. It is also known that nano-scale particles and materials show distinctly different thermodynamical properties than their bulk counterparts due to surface and interfacial effects. These effects are negligible in the bulk material but they become dominant at small scales where the total fraction of atoms at the surface is significant. With the ever increasing nanotechnology research, it is therefore desirable to have a means of studying thermodynamical properties of small volume samples, ultimately a single nanoparticle. (Read the rest of this entry)
Lasing Action from a Toroidal Microcavity
Micro-resonators with ultrahigh quality factors (Q-factor) became an important field of study as they find potential applications in numerous fields such as laser action, nonlinear optics, frequency metrology, telecommunications and cavity quantum electrodynamics. The superior optical confinement properties of such resonators make them excellent research tools. Micro-toroids are remarkable micro-resonators; they can simply be produced by CMOS compatible fabrication techniques, and due to their relatively smaller mode volume they have a high confined electromagnetic energy density. Inducing laser action from a micro-cavity with an ultrahigh Q-factor is a critical step in developing more efficient lasers -both low threshold and no threshold. In this regard, we generated laser action from a silica micro-toroid covered with an active polymer yielding the lowest threshold obtained until now by free space excitation. (Read the rest of this entry)
Silica aerogels are composed of silica network of 3-4 nm particles surrounded with 30-40 nm holes. As a result of the three dimensional network with holes, they have very low density and up to 99.8% air trapped inside. In our group we are capable of producing highly transparent, flexible and thermally stable organically modified silica aerogel thin films by sol-gel technique. Due to their inorganic-organic hybrid nature obtained films exhibit both thermal and environmental stability in addition to flexibility. They can be applied to various surfaces including glass, wood, cloth, metal and plastics with contact angles reaching 179.9° and preserve their superhydrophobic behavior even when they are bent. (Read the rest of this entry)
President Abdullah Gül stopped by our laboratories during his visit to UNAM-Institute of Materials Science and Nanotechnology on Wednesday, September 02, 2009. The President was briefed about projects on superhydrophobic aerogel thin films, microfluidic metamaterials, tumor therapy with infrared lasers, and explosive sensing materials by graduate students. (Read the rest of this entry)
Dr. Rohrer visits our group laboratories
Nobel Laureate Henrich Rohrer visited Bayindir Research Group during his weeklong visit to UNAM, Bilkent University. Researchers had the rare opportunity to present and discuss their research, and hear Dr. Rohrer's insight on nanoscience and nanotechnology. Dr. Rohrer shared the 1986 Physics Nobel Prize, with Ernst Ruska and Gerd Binnig for the design of the scanning tunneling microscope.