New research from the Giannis (Yanni) Mpourmpakis and his team introduces the first universal adsorption model that accounts for detailed nanoparticle structural characteristics, metal composition and different adsorbates, making it possible to not only predict adsorption behavior on any metal nanoparticles but screen their stability, as well. The research combines computational chemistry modeling with machine learning to fit a large number of data and accurately predict adsorption trends on nanoparticles that have not previously been seen. By connecting adsorption with the stability of nanoparticles, nanoparticles can now be optimized in terms of their synthetic accessibility and application property behavior. This improvement will significantly accelerate nanomaterials design and avoid trial and error experimentation in the lab. Their work was published in Science Advances on Sept. 13, 2019.Continue reading
The ability to combine continuously tunable narrow-band terahertz (THz) generation that can access both the far-infrared and mid-infrared regimes with nanometer-scale spatial resolution is highly promising for identifying underlying light-matter interactions and realizing selective control of rotational or vibrational resonances in nanoparticles or molecules. Here, we report selective difference frequency generation with over 100 THz bandwidth via femtosecond optical pulse shaping. The THz emission is generated at nanoscale junctions at the interface of LaAlO3/SrTiO3 (LAO/STO) that is defined by conductive atomic force microscope lithography, with the potential to perform THz spectroscopy on individual nanoparticles or molecules. Numerical simulation of the time-domain signal facilitates the identification of components that contribute to the THz generation. This ultra-wide-bandwidth tunable nanoscale coherent THz source transforms the LAO/STO interface into a promising platform for integrated lab-on-chip optoelectronic devices with various functionalities.
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The recently published paper in journal of ACS NANO on Ultrafast Microscopy of Spin-Momentum Locked Surface Plasmon Polaritons is an essential research for designing optical elements to control spin-polarized SPP (surface plasmon polaritons) fields on the nano femto scale. Hrvoje Petek and his colleagues have shown two-photon photoemission electron microscopy images formed by coupling and propagation of longitudinal and transverse components of SPP fields of light. Further, they have also shown the spin-momentum locked SPP wave packets launched with circularly polarized excitation propagate at the same phase and group velocities as for the linearly polarized excitation using time-resolved experiments.Continue reading
Michael Widom and his colleagues showed what happens at the grain boundaries of one particular alloy of the metals nickel and bismuth that makes it brittle in their paper published in Science. Using advanced electron microscopes, Widom’s collaborators at Lehigh University scrutinized these microscopic grain boundaries at an atomic level. In a "very heroic experimental program" they discovered that when grains met, the bismuth and nickel atoms realigned into lattices to form layered superstructures at the grain boundaries. These superstructures had previously been thought to exist only rarely in some alloys. Finding it at many different boundaries led the team to conclude that these superstructures are probably much more common than many people had thought. Continue reading
Owing to high surface to volume ratios and chemical potential, nanoparticles possess unique optical, electrical, and thermal properties, which constitute the basis of novel applications in sensing, catalysis, nanoelectronics, bio-tagging etc. Despite the great advances in the synthesis, the total structure determination of nanoclusters still remains to be a major challenge. Recently Hyung J. Kim and their colleagues have reported the synthesis and crystal structure of a nanocluster composed of 23 silver atoms capped by 8 phosphine and 18 phenylethanethiolate ligands in the journal of Nature Communications.Continue reading
In the recently published paper in Scientific Reports, Sara A. Majetich and their colleagues have demonstrated the engineering of spin canting across a Magnetic nanoparticles (MNP) via the Dzyaloshinskii-Moriya interaction (DMI). In this paper, they have shown that strong DMI can lead to magnetic frustration within the shell and cause canting of the net particle moment. These results have illuminated how core/shell nanoparticle systems can be engineered for spin canting across the whole of the particle, rather than solely at the surface.
In the recently accepted paper in Physical Review Letter, Hrvoje Petek and his colleagues investigate the coherent electron transfer from an interface state that forms upon chemisorption of Ag nanoclusters onto graphite to a σ symmetry interlayer band of graphite. Interfacial charge transfer is a fundamental process in heterogeneous and plasmonically enhanced catalysis. The charge transfer, however, is thought to be restrained by an interfacial potential barrier, such as a Schottky barrier at a metal-semiconductor interface. With optical excitation, the interfacial charge transfer can also be efficiently completed by coherent dipole coupling between the donor and acceptor bands. In this study Petek and his colleagues advance the time-resolved multidimensional multiphoton photoemission spectroscopy technique to not only pump the donor band and probe the acceptor band, but also directly image the coherent polarization dynamics between them. They discover a direct resonant ... Continue reading
The Department of Physics and Materials Science at the University of Memphis, Memphis, TN, USA, is seeking highly qualified individuals for a tenure-track faculty position, at the Assistant Professor level, in the field of Quantum Physics to begin in Fall 2020. The department offers BS and MS programs in physics, with various concentrations, and a joint PhD program in Engineering Physics with the Herff College of Engineering. The current faculty members of the department are actively engaged... Read More
Deadline: Friday, December 20, 2019The ECE Department (http://www.engineering.pitt.edu/ECE/) at the University of Pittsburgh (Pitt) invites applications for two tenure-stream (TS) positions as Assistant Professor in the field of computer engineering, with one in computing, sensing, and electronics for aerospace systems, or reconfigurable and high-performance computing, and the other in neuromorphic computing, or quantum computing, or embedded computing and sensing in medical... Read More
Deadline: Monday, January 20, 2020
Di Xiao and Rongchao Jin continue to be listed among the most cited researchers. Jin’s research focuses on nanochemistry, and he is well-known for developing new methodologies to create gold nanoparticles with precise numbers of atoms. Xiao’s research looks at the properties of materials in relation to quantum mechanics and how these properties can be harnessed for applications in electronic and magnetic devices.
Among five other faculty members, Chandralekha Singh was honored on Nov. 19 at the third annual Provost’s Diversity in the Curriculum awards, which recognizes faculty who have taught a modified course or revised curricula to strengthen diversity and inclusion, resulting in changes of impact.
“There’s a wealth of literature which suggests that serious engagement in diversity in the curriculum, connected with classroom and outside the classroom experiences positively affects students’ awareness and attitudes toward diversity,” said Paula Davis, assistant vice chancellor for health sciences diversity in the School of Health Sciences, in her keynote speech.
Dr. Singh was recognized for incorporating into introductory courses a new “belonging intervention,” which resulted in improved grades for all students. Using a random assignment of classrooms to enable assessment, the intervention aimed to address gender and racial gaps; it is now part of the standard curriculum in the classes in which it was introduced.
The Discipline-Based Science Education Research Center, or dB-SERC, has many excellent resources to share, learn more here and congratulations to Dr. Singh!
Turbulence in fluid mechanics has been a scientific challenge since at least the 16th century when Leonardo da Vinci sketched the chaotic movements of water flowing around obstacles in the Arno River. It is regularly described as one of the last unsolved problem of classical physics – a solution to the Navier-Stokes equation, the mathematical underpinning of turbulence, was declared a Millennium Prize Problem by MIT’s Clay Mathematics Institute in 2000. The $1 million prize remains unclaimed in 2019.
Pitt researcher Peyman Givi hopes to confront that centuries-old challenge with the power of a new generation of computing. He and a team developed an algorithm capable of using quantum computing to model turbulence at an unprecedented level of detail.
Givi, Distinguished Professor of mechanical engineering and materials science, explains the importance of turbulence. “Turbulence is central to the efficiency of fuel. Turbulence enhances mixing – more mixing creates more reactions and more reactions mean more power. No turbulence, little reaction, little power.”
The challenge of modeling turbulence is evident in the Da Vinci drawings. “We create simulations of eddies – the swirling wheels and whirls and vortices of all sizes you see in the drawings. Fluid mechanics is composed of very large differences in scales. If for example you calculate drag on an airplane wing [fluid mechanics involves both liquids and gases], the largest scale is the entire wing, the smallest scale is close to nanometers. A grid big enough to take in all the scales together won’t fit on a computer. So we simulate the largest part – I don’t need to resolve the smallest scale to model the effects. But the model is not an exact science – you are introducing art into science.”
The science may become more exact using quantum computing. Givi is co-author on a May 2019 paper in the journal Combustion Theory and Modelling – “Quantum algorithm for the computation of the reactant conversion rate in homogeneous turbulence” – presenting an algorithm for predicting the rate of reaction in simulated turbulence and exploring the potential for applications of quantum technology to fluid dynamics and combustion problems. Citing the rapid progress in the development of quantum computing hardware, the paper posits the importance of designing algorithms now that could eventually run on that hardware – “quantum algorithm with a real engineering application.”
