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The Dinesh O. Shah Professorship in Surface Science

After serving the University of Florida and our Gator Engineers for more than three decades, Dr. Shah legacy continues to shape the Chemical Engineering Department. Find out more about one of the department’s most important initiatives.

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Research featured as a frontispiece of Angewandte Chemie

Research performed as collaboration between Professors Helena Hagelin-Weaver in Chemical Engineering and Clifford Russell Bowers in Chemistry has been featured as a frontispiece in a recent issue of Angewandte Chemie. In this work, the hydrogenation of propene to propane was investigated over CeO2 nano-cubes, nanorods and nano-octahedra using parahydrogen induced polarization (PHIP) nuclear magnetic resonance (NMR). PHIP-NMR is a unique method which can identify if the two hydrogen atoms added across the double-bond of propene originate from the same molecule (pair-wise addition of hydrogen) or is the result of random addition, and can thus give insight into the mechanism of hydrogenation reactions. The highlighted research reveals that while the hydrogenation of propene over CeO2 is strongly dependent on the CeO2 surface structure (and thus also CeO2 shape), the pair-wise addition of hydrogen is not. This research collaboration has also resulted in a JACS paper (see below). READ MORE.

Smart Shape Memory Polymers Published in Nature Communications

Shape memory polymers are a class of smart materials that can memorize and recover their permanent shape in response to an external stimulus, such as heat, light, and solvent. They have been utilized in a wide spectrum of applications ranging from biomedical devices to aerospace morphing structures. Led by a Chemical Engineering graduate student - Yin Fang, Prof. Jiang’s group has recently pioneered a new type of shape memory polymer that can be instantaneously triggered by applying an external pressure or by exposing to a large variety of vapors, such as acetone and toluene. These unconventional stimuli induce an easily perceived color change of the special polymer.

This striking chromogenic effect could find important applications in reconfigurable/rewritable nanooptical devices for all-optical integrated circuits, reusable and inexpensive chromogenic vapors sensors for homeland security and environmental monitoring (e.g., detecting explosives and toxic vapors in buildings), novel biometric and anti-counterfeiting materials, and healthcare screening. The results have recently been published in Nature Communications (doi: 10.1038/ncomms8416) and Advanced Materials (doi: 10.1002/adma.201500835). Dr. Curtis Taylor from UF Department of Mechanical and Aerospace Engineering and Dr. Vito Basile from National Council of Research, Italy are major collaborators of the work. DTRA, NASA, and NSF sponsored this discovery.

Paper chosen as Editor's pick in JVST B

The Elevated Temperature Performance of Si-implanted Solar-Blind beta-Ga2O3 Photodetectors paper by Professor Fan Ren et al has recently been selected as Editor’s pick in the Journal of Vacuum Science & Technology B. The temperature dependent photoresponse of planar photodetectors fabricated on ß-Ga2O3films grown on Al2O3 by metalorganic chemical vapor deposition to 254?nm wavelength, and blindness to 365?nm light, are reported over the range of 25–350?°C. Ohmic contacts were formed by Si-implantation and annealing at 900?°C, followed by deposition of Ti/Au metallization. The photocurrent induced by 254?nm illumination increased monotonically with temperature, from ~2.5 ×?10-7 A at 25?°C to ~2.2 ×?10-6 A at 350?°C at a fixed 254?nm light intensity of 760?µW/cm2. The photosensitivity decreases at high temperatures in many photoconductors(thermal quenching), in sharp contrast to the photosensitivity increase with high temperatures in this study. This is ascribed to the presence of states in the gap of Ga2O3, whose presence was proven by exposure to below band-gap energy. In this case, the current still increased due to the presence of defect levels in theband gap and the generation of photocurrent is due to a transition between the valence or conduction band and impurity or defect levels within the band gap. The temperature dependent photo-to-dark current ratio for this wavelength was 328 at room temperature and decreased to ~9 at 350?°C. The responsivity increased from 5 to 36?A/W over this temperature range, with corresponding external quantum efficiencies of 2.5 × 103% at 25?°C and 1.75 × 104 % at 350?°C. Similarly large numbers reported for Ga2O3photodetectors have previously been ascribed to carrier multiplication effects. See more HERE.

Journal of the American Chemical Society Paper on Alkene Hydrogenation

In a recent paper published in Journal of the American Chemical Society, Professors Helena Hagelin-Weaver (Chemical Engineering) and Clifford Russell Bowers (Chemistry) investigated the hydrogenation of propene to propane over titania-supported platinum (Pt/TiO2) catalysts using parahydrogen induced polarization (PHIP) nuclear magnetic resonance (NMR). Using PHIP-NMR a small amount of propane product resulting from the pair-wise addition of hydrogen over the supported metal catalyst was observed. Furthermore, PHIP signal was observed also on the propene reactant. It was shown that this is the result of a previously hidden pathway of pairwise replacement, i.e. dehydrogenation and pairwise rehydrogenation, over this catalyst. READ MORE.

Recent paper featured as highlight and cover art of Journal of Cellular physiology

Research performed by Qiao Zhang and his coworkers was recently selected to be a highlight article and cover art by the Journal of Cellular Physiology. Despite being densely packed with DNA, nuclear bodies and a nucleoskeletal network, the nucleus is a remarkably dynamic organelle. Chromatin loops form and relax, RNA transcripts and transcription factors move diffusively, and nuclear bodies move. Zhang’s work shows a new type of motion of RNA splicing speckles in the cell nucleus. Small speckles move to larger speckles with which they fuse in an ATP and RNA polymerase II dependent manner. The random motion of speckles is regulated by both intra- and extra-nuclear forces. Qiao and his coworkers also devised a novel method to create a pressure gradient flow inside the nucleus. Speckles moved and deformed along curvilinear paths in respond to the pressure flow, suggesting the presence of channels with a low mechanical resistance to motion through which the speckles can move. READ MORE

Chemical Communications paper about co-surfactant states around carbon nanotubes

Research performed by Chemical Engineering Ph.D. student, Yang Zhao, under the advisement of Dr. Kirk Ziegler was recently published in Chemical Communications. Single wall carbon nanotubes (SWCNTs) contain a mixture of nanotubes with different chiralities known as (n,m) types. This work reports the formation of thermodynamic co-surfactant states around SWCNTs. The stability of these thermodynamic states enables high-fidelity separations of specific SWCNT (n,m) types based on their selective desorption from hydrogels. By modulating the surfactant concentration of sodium dodecyl sulfate (SDS) and sodium deoxycholate (DOC), the Ziegler group found a very specific co-surfactant ratio that elutes a high-purity (90%+) fraction of (6,5) SWCNTs. The elution of only one (n,m) type at a specific co-surfactant ratio while other types are exposed to more surfactant suggests that each (n,m) type forms a thermodynamically-stable structure in the co-surfactant solution. These findings provide a promising foundation for the development of large-scale, high-throughput chromatographic separations that can collect each (n,m) type sequentially. This work was performed in collaboration with the Dr. Jean-Claude Bonzongo group (Environmental Engineering Sciences Department, UF). The full article may be found HERE.

Angewandte Chemie paper about Alkane Activation

The Weaver group recently published a paper in Angewandte Chemie that reports the first vibrational spectra of a “pre-activated” alkane adsorbed on a solid surface. A strong interaction between propane and the metal atoms of a palladium oxide surface causes the activated C-H bonds to undergo a large downshift in their stretching frequencies which the Weaver group could measure using surface infrared spectroscopy. By using partially deuterated propane compounds, Weaver and his students were able to show that the adsorbed propane molecules adopt highly specific configurations in which the primary C-H bonds are selectively activated by the metal oxide. Their work demonstrates that geometrical registry between the molecules and the surface plays a decisive role in determining the preferred bonding configurations of alkanes adsorbed on metal oxides. These findings can provide guidance to future efforts aimed at designing catalyst structures with potential to achieve selective alkane conversions. The full article may be found HERE.

Research featured as a frontispiece of Advanced Optical Materials

The research conducted by a Chemical Engineering graduate student, Yin Fang, with Professors Jiang and Taylor (UF Aerospace and Mechanical Engineering) has featured as a frontispiece in the recent issue of Advanced Optical Materials. This work explores a new type of smart nanooptical coatings with bistable optical states using thermoresponsive shape memory polymers. The heat-triggered transition between a disordered temporary state and a 3-D ordered permanent state leads to an easily perceived color change, which provides a unique mechanism for developing reconfigurable nanooptical devices for all-optical integrated circuits. READ MORE