Research

Scientists Capture Snapshots of the Proton Conduction Process in Water

The motion of protons (positively charged H atoms) in water is associated with water’s conduction of electricity and is involved in many important processes including vision, signaling in biological systems, photosynthesis and, the operation of fuel cells. Both artificial photosynthetic systems and fuel cells are of growing interest for clean energy technologies. However, the details of how protons move in water have remained elusive, and an enhanced understanding of the nature of this process is needed to improve the technologies that depend on proton transfer.

An international team of scientists, including a University of Pittsburgh professor and graduate student, has used spectroscopic methods to obtain snapshots of the process by which a proton is relayed from one water molecule to the next. The research is published in a paper in the December 2, 2016 issue of the journal Science.

Although synthetic chemists typically regard carbon-carbon single bonds as inert, they have used metal catalysts to spring open C–C bonds in strained rings, such as cyclopropanes and cyclobutanes. Performing a similar transformation with less strained but more common five- and six-membered rings, however, has proven more difficult.

Now, synthetic and theoretical chemists report a way of opening up C–C bonds in aryl substituted cyclopentanones to produce α-tetralones. The reaction was developed by University of Chicago’s Guangbin Dong and Ying Xia, and at Pitt, Peng Liu and his post doc Gang Lu studied the mechanism from a quantum chemical point of view with DFT (Density Functional Theory) calculations.

The results are published in the online issue of Nature.

Application of a femtosecond spectroscopy technique to a copper surface has allowed the desorption of carbon monoxide molecules to be tracked with unprecedented detail.

In this view point article, Hrvoje Petek comments on the work of Ken-ichi Inoue et al. on the multidimensional nonequilibrium dynamics of CO as it desorbs from a Cu(100) surface.  He opens by saying that "it has long been a chemist’s dream to catch a chemical reaction in the act", with the aim "to observe and interfere with this process in mid-course and thereby control its outcome".

A natural citrus fruit extract has been found to dissolve calcium oxalate crystals, the most common component of human kidney stones, in a finding that could lead to significantly improving kidney stone treatment, according to researchers at the University of Pittsburgh, the University of Houston, and Litholink Corporation, among which is Giannis Mpourmpakis.

In a study published Aug. 8 in the journal Nature, the researchers offer the first evidence that the compound hydroxycitrate (HCA) effectively inhibits calcium oxalate crystal growth and, under certain conditions, is able to dissolve the crystals. HCA shows “promise as a potential therapy to prevent kidney stones,” the researchers wrote. 

The latest study in David Waldeck's group, published in ACS Nano Letters, demonstrates that chiral imprinted CdSe quantum dots (QDs) can act as spin selective filters for charge transport.

Semiconductor quantum dots remain an attractive material for photovoltaics because of their solution processability and potential for multiple exciton generation; enabling a promising route for the realization of low cost, high efficiency solar cells. In addition, previous experiments have shown that spin selective charge transport can enhance the photoconversion efficiencies of organic bulk heterojunctions. The present work therefore explores whether chiral induced spin selectivity (CISS) can be used as an alternative approach to affect charge transport through quantum dot films and demonstrates that quantum dot thin films composed of chiral semiconductors preferentially transmit electrons with a particular spin orientation.

When it comes to computers, people never look for “bigger and better,” but rather “smaller and faster.” How do we continue to keep up with that demand, making technology smaller, faster, and more energy-efficient? According to Vincent Sokalski, the answer may be in the fundamental origins of magnets—the spin of electrons.

Sokalski and his group studied the interaction of electron spins in magnetic materials poised for use in next-generation cellphones and computers and discovered how to better measure and predict the changing magnetic state of those materials. This new understanding, recently published in Physical Review B under the title "Energetic Molding of Chiral Magnetic Bubbles", is exciting for the future of computing technology because it will allow scientists to explore and develop materials that are more energy-efficient and faster than traditional semiconductor-based materials.

"All is well with particle-hole symmetry". Roger Mong and colleagues accross the United States provided strong evidence for a recent conjecture that contrasts with the predictions of standard theory and predicts a liquid consisting of massless Dirac particles that respects the symmetry between particles and holes

In an external magnetic field, the energy of an electron in a two-dimensional system takes discrete values, called Landau levels. At high enough fields, all electrons in a solid can fit in the lowest Landau level. If exactly half of that level is filled with electrons, standard theory predicts that a special fermion liquid phase will form that makes a distinction between the filled and empty states (particles and holes). However, a recent conjecture, in contrast, predicted a liquid consisting of massless Dirac particles that respects the symmetry between particles and holes, for which the authors of this paper provided strong evidence.

In their latest article, Jeremy Levy and his group put forward compelling experimental evidence of the role of surface chemistry on conductivity in complex oxides heterostructures. 

This work, published in Nature Communications on February 10, 2016 illustrates how the conductivity of the 2DEG layer in LAO/STO can be modulated using solvent immersion and illumination. 

"Scanning near-field optical microscopy combined with pump–probe spectroscopy can resolve ultrafast dynamics at the nanoscale."

In this short article, Hrvoje Petek reflects on a new technique that combines the nanometre resolution of near-field microscopy with the femtosecond resolution of pump–probe spectroscopy. This technique has been developed by Markus Raschke and colleagues at the University of Colorado at Boulder and submitted in the present issue of Nature Nanotechnology.