Publications by authors named "Tony E Karam"
The synthesis, characterization, ultrafast dynamics, and nonlinear spectroscopy of 30 nm nanospheres of brilliant green-bis(pentafluoroethylsulfonyl)imide ([BG][BETI]) in water are reported. These thermally stable nanoparticles are derived from a group of uniform materials based on organic salts (nanoGUMBOS) that exhibit enhanced near-infrared emission compared with the molecular dye in water. The examination of ultrafast transient absorption spectroscopy results reveals that the overall excited-state relaxation lifetimes of [BG][BETI] nanoGUMBOS are longer than the brilliant green molecular dye in water due to steric hindrance of the torsional degrees of freedom of the phenyl rings around the central carbon.
View Article and Find Full Text PDFPhoton-Induced Near-Field Electron Microscopy of Eukaryotic Cells.
Angew Chem Int Ed Engl
September 2017
Photon-induced near-field electron microscopy (PINEM) is a technique to produce and then image evanescent electromagnetic fields on the surfaces of nanostructures. Most previous applications of PINEM have imaged surface plasmon-polariton waves on conducting nanomaterials. Here, the application of PINEM on whole human cancer cells and membrane vesicles isolated from them is reported.
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- The study investigates the ultrafast dynamics of TiO2-Au nanocomposites, focusing on how gold nanocluster size affects electronic interactions and relaxation processes.
- The relaxation times linked to the plasmon depletion band remain unchanged with varying gold shell sizes, while electron transfer lifetimes significantly shorten as the shell size increases.
- Size-dependent periodic oscillations linked to acoustic phonons are noted, revealing that larger gold clusters result in lower frequencies but consistent damping times, which has implications for enhancing catalytic materials.