Plasma Processing Approach to Molecular Surface Tailoring of Nanoparticles:  Improved Photocatalytic Activity of TiO₂

Abstract

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.

Surface chemistry influences implant‐mediated host tissue responses

“…These monomers were selected to provide a diverse variety of chemistries ranging from uncharged hydrophobic (C 6 F 14 ) and hydrophilic (EO 2 V), to cationic (VAA) and anionic (NH 2 C 2 H 4 NH 2 ) hydrophilic surfaces. A home built custom reactor, capable of continuous 360° rotation during the plasma deposition was employed to overcome the tendency for particle aggregation and thus promote more uniform polymer film coverage of the substrates [37,38]. One gram samples of the particles were coated in each run.…”

“…Our laboratory has recently developed a modified Radio Frequency Glow Discharge (RFGD) technique to functionalize a wide variety of micro [37], and more recently, nanosized, spheres [38]. Additionally, using a pulsed plasma technique, we have previously shown that we can effectively control the film chemistry obtained from a given monomer undergoing polymerization via simple variations in the plasma duty cycles employed.…”

Surface chemistry influences cancer killing effect of TiO2 nanoparticles

“…This efficient mass transport and agitation of the particles successfully overcomes the tendency for nanoparticle aggregation providing continuous exposure of fresh TiO 2 surface to the plasma generated reactive molecules and ions. The specific process employed has been previously shown to be extremely effective in coating fine powders [31], including nanoparticles [32]. In a typical run, 3.5 g of TiO 2 particles were loaded inside the borosilicate glass reactor and the reactor was evacuated to 5 mTorr background pressure.…”

“…Under the pulsed condition, the extent of retention of the functional group in a given monomer increases as the duty cycle employed during the plasma polymerization is decreased [32]. The average power input is defined as: Average power (W) = (Duty cycle) × Peak Power (W), where the duty cycle represents the ratio of the plasma on time divided by the plasma (on + off) time.…”

Cold Plasma – A Promising Tool for the Development of Electrochemical Cells

“…To obtain partially fluorinated tin oxide, hexafluoropropylene oxide (C 3 F 6 O) was added to Sn(CH 3 ) 4 . It should be noted that significantly increased photocatalytic activity of TiO 2 nanoparticles was achieved using the PECVD approach (Cho, J. et al, 2006).…”