West University Place, TX, United States
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Abel P.R.,1 University Station C0400 | Lin Y.-M.,1 University Station C0400 | Celio H.,University of Texas at Austin | Heller A.,1 University Station C0400 | And 2 more authors.
ACS Nano | Year: 2012

Silicon and partially oxidized silicon thin films with nanocolumnar morphology were synthesized by evaporative deposition at a glancing angle, and their performance as lithium-ion battery anodes was evaluated. The incorporated oxygen concentration was controlled by varying the partial pressure of water during the deposition and monitored by quartz crystal microbalance, X-ray photoelectron spectroscopy. In addition to bulk oxygen content, surface oxidation and annealing at low temperature affected the cycling stability and lithium-storage capacity of the films. By simultaneously optimizing all three, films of ∼2200 mAh/g capacity were synthesized. Coin cells made with the optimized films were reversibly cycled for ∼120 cycles with virtually no capacity fade. After 300 cycles, 80% of the initial reversible capacity was retained. © 2012 American Chemical Society.

Yoon S.J.,University of Texas at Austin | Mallidi S.,University of Texas at Austin | Tam J.M.,University of Texas at Austin | Tam J.O.,University of Texas at Austin | And 4 more authors.
Proceedings - IEEE Ultrasonics Symposium | Year: 2010

Plasmonic nanoparticles have been widely used for various biomedical applications such as biological imaging, sensing, and cancer therapy. Specifically, gold nanospheres, nanorods, and nanoshells are used as contrast agents for photoacoustic imaging due to their strong absorptive property. However, there are concerns about using these nanoparticles in-vivo because they are not biodegradable and cannot be cleared from the body. Recently, biodegradable nanoclusters have been reported. The biodegradable nanoparticles are composed of primary 4-nm gold nanoparticles and stabilized by a biodegradable polymer binder. In this study, we demonstrated the utility of biodegradable nanoclusters as a contrast agent in photoacoustic imaging. The tissue mimicking phantoms were used for ultrasound and photoacoustic imaging. The results show that the biodegradable plasmonic nanoclusters can be used as photoacoustic contrast agent. © 2010 IEEE.

Chemelewski W.D.,1 University Station C0400 | Hahn N.T.,1 University Station C0400 | Mullins C.B.,1 University Station C0400
Journal of Physical Chemistry C | Year: 2012

The photoelectrochemical water oxidation performance under simulated solar irradiation of hematite (α-Fe 2O 3) films synthesized by coevaporation of pure Si and Fe in an oxygen ambient, a process known as reactive ballistic deposition, is studied as a function of Si doping level and film porosity, ranging from dense films to nanocolumnar films. It is found that Si segregates to the hematite surface, does not improve the bulk conductivity, and lowers the optical absorption coefficient. Nevertheless, the photoelectrochemical performance of Si-doped, porous films is significantly improved relative to undoped, porous films. However, the improvement relative to dense, undoped films is marginal. It is concluded that Si acts to passivate the hematite surface and aids charge transfer to the solution. Additionally, from incident photon conversion efficiency measurements it is found that Si doping and porosity have little effect on the normalized spectral response of 100 nm thick hematite films. © 2012 American Chemical Society.

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