Photocatalyzed TiO 2 nanoparticles have been shown to eradicate cancer cells. However the required in situ introduction of UV light limits the use of such a therapy in patients. In the present study, the non-photocatalyic anti-cancer effect of surface functionalized TiO 2 was examined. Nanoparticles bearing -OH, -NH2, or -COOH surface groups, were tested for their effect on in vitro survival of several cancer and control cell lines. The cells tested included B16F10 melanoma, Lewis lung carcinoma (LLC), JHU prostate cancer cells, and 3T3 fibroblasts. Cell viability was observed to depend on particle concentrations, cell types, and surface chemistry. Specifically, -NH 2 and -OH groups exhibited significantly higher toxicity than -COOH. Microscopic and spectrophotometric studies revealed nanoparticle-mediated cell membrane disruption leading to cell death. The results suggest that functionalized TiO 2 , and presumably other nanoparticles, may be surface engineered for targeted cancer therapy.

Plasma enhanced chemical vapor deposition (PECVD) was employed to modify surfaces of TiO2 nanoparticles. To help overcome nanoparticle aggregation, a 360° rotating reactor was employed to provide continuous agitation and mixing of the particles during the plasma induced film deposition process. The nanoparticles were coated with thin films produced from the plasma polymerization of tetramethyltin (TMT) monomer. Subsequently, the coated particles were heated in air to remove the carbonaceous material while, simultaneously, oxidizing the tin atoms to tin oxide. The photocatalytic activity of the tin oxide coated TiO2 was then measured and contrasted with that of untreated TiO2 particles. A significantly enhanced increase in the oxidation rate of acid orange (AO7) dye was observed with the modified particles. Additional experiments employing a mixture of TMT and perfluoropropylene oxide monomers were used to achieve surfaces possessing partially fluorinated tin oxide. The fluorine doped tin oxide coatings exhibited even higher catalytic activity than that obtained from TMT only experiments. Some experiments involving characterization of the films before and after the annealing process, specifically those involving X-ray diffraction and atomic force microscopy measurements, were carried our using flat glass or polished silicon substrates. Overall, this study demonstrates the general utility of PECVD technology to provide effective coating of ultrafine nanoscale particles.

Titanium dioxide (TiO(2)) is a preferred catalyst for photocatalytic oxidation of many air pollutants. In an effort to enhance its photocatalytic activity, TiO(2) was modified by pulsed plasma treatment. In this work, TiO(2) nanoparticles, coated on a glass plate, were treated with a plasma discharge of hexafluoropropylene oxide (HFPO) gas. By appropriate adjustment of discharge conditions, it was discovered that the TiO(2) particles can be either directly fluorinated (Ti-F) or coated with thin perfluorocarbon films (C-F). Specifically, under relatively high power input, the plasma deposition process favored direct surface fluorination. The extent of Ti-F formation increased with increasing power input. In contrast, at lower average power inputs, perfluorocarbon films are deposited on the surface of the TiO(2) particles. The plasma surface modified TiO(2) nanoparticles were subsequently employed as catalysts in the photocatalytic oxidation of m-xylene in air, as carried out inside a batch reactor with closed loop constant gas circulation. Both types of modified TiO(2) were significantly more catalytically active than that of the unmodified particles. For example, the rate constant of m-xylene degradation was increased from 0.012 min(-1) with untreated TiO(2) to 0.074 min(-1) with fluorinated TiO(2). Although it is not possible to provide unequivocal reasons for this increased photocatalytic activity, it is noted that the plasma surface treatment converted the TiO(2) from hydrophilic to highly hydrophobic, which would provide more facile catalyst adsorption of the xylene from the flowing air. Also, based on literature reports, the use of fluorinated TiO(2) reduces electron-hole recombination rates, thus increasing the photocatalytic activity.

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Polyallylamine films, deposited on Si wafers by radio frequency (RF) pulsed plasma polymerization (PPP), were employed as insulating layers of metalinsulator-semiconductor (MIS) capacitors. The insulating polymer films were deposited at plasma reactor temperatures of 25°C and 100°C. Multiple frequency capacitance-voltage (C-V) measurements indicated that an in-situ heat treatment during film deposition increased the insulator dielectric constant. The dielectric constant, calculated from the C-V data, rose from 3.03 for samples with no heat treatment to 3.55 for samples with an in-situ heat treatment. For both sample sets, the I-V data demonstrates a low leakage current value (Ͻ20 fA) up to 100 V. Capacitance-time (C-t) measurements were also used to characterize the mobile ions in the polymer that migrate over time with applied voltage. Results indicate that the polymer layers contain few electrically active defect centers and virtually no pinholes. Hysteresis in the C-V curves with differing sweep directions was more pronounced for in-situ heat-treated samples indicative of mobile charge.