Remote atmospheric-pressure plasma activation of the surfaces of polyethylene terephthalate and polyethylene naphthalate.

The surfaces of poly(ethylene terephthalate) (PET) and poly(ethylene naphthalate) (PEN) were treated with an atmospheric-pressure oxygen and helium plasma. Changes in the energy, adhesion, and chemical composition of the surfaces were determined by contact angle measurements, mechanical pull tests, and X-ray photoelectron spectroscopy (XPS). Surface-energy calculations revealed that after plasma treatment the polarity of PET and PEN increased 6 and 10 times, respectively. In addition, adhesive bond strengths were enhanced by up to 7 times. For PET and PEN, XPS revealed an 18-29% decrease in the area of the C 1s peak at 285 eV, which is attributable to the aromatic carbon atoms. The C 1s peak area due to ester carbon atoms increased by 11 and 24% for PET and PEN, respectively, while the C 1s peak area resulting from C-O species increased by about 5% for both polymers. These results indicate that oxygen atoms generated in the plasma rapidly oxidize the aromatic rings on the polymer chains. The Langmuir adsorption rate constants for oxidizing the polymer surfaces were 15.6 and 4.6 s(-1) for PET and PEN, respectively.

Effect of twinning on the photoluminescence and photoelectrochemical properties of indium phosphide nanowires grown on silicon (111).

The relationship between crystal quality and the properties of indium phosphide nanowires grown on silicon (111) has been studied by transmission electron microscopy, photoluminescence spectroscopy, and photoelectrochemistry. Wires with no defects and with {111} twin boundaries parallel and perpendicular to the growth direction were obtained by metalorganic vapor-phase epitaxy using liquid indium catalyst. Room temperature photoluminescence from the defect-free nanowires is approximately 7 times more intense than that from the wires with twin boundaries. An open-circuit photovoltage of 100 mV is observed for photoelectrochemical cells made with the defect-free nanowires, whereas no photovoltage is recorded for those with twins.

Hydrogen adsorption on the indium-rich indium phosphide (001) surface: a novel way to produce bridging In-H-In bonds.

The indium phosphide (001) surface provides a unique chemical environment for studying the reactivity of hydrogen toward the electron-deficient group IIIA element, indium. Hydrogen adsorption on the In-rich delta(2 x 4) reconstruction produced a neutral, covalently bound bridging indium hydride. Using vibrational spectroscopy and ab initio cluster calculations, two types of bridging hydrides were identified, a (mu-H)In(2) and a (mu-H)(2)In(3) "butterfly-like" structure. These structures were formed owing to the large thermodynamic driving force for adsorption of H atoms on solid-state indium dimers.