Innovative UVC Light (185 nm) and Radio-Frequency-Plasma Pretreatment of Nylon Surfaces at Atmospheric Pressure and Their Implications in Photocatalytic Processes

Abstract

Innovative pretreatment by UVC light (185 nm) and by radio-frequency (RF) plasma at atmospheric pressure to functionalize the Nylon surface, increasing its bondability toward TiO(2), is reported in this study. In the case of UVC light pretreatment in air, the molar absorption coefficient of O(2)/N(2) at 185 nm is very low and the air in the chamber absorbs very little light from the UVC source before reaching the Nylon sample. Nylon fabrics under RF plasma were also functionalized at atmospheric pressure because of the marked heating effect introduced in the Nylon by the RF plasma. This effect leads to intermolecular bond breaking and oxygenated surface groups in the topmost Nylon layers. Both pretreatments enhanced significantly the photocatalytic discoloration of the red-wine stain in Nylon-TiO(2) compared with samples without pretreatment. The UVC and RF methods in the absence of vacuum imply a considerable cost reduction to functionalize textile surfaces, suggesting a potential industrial application. Red-wine-stain discoloration under simulated sunlight was monitored quantitatively by diffuse-reflectance spectroscopy and by CO(2) evolution. X-ray photoelectron spectroscopy (XPS) was used to monitor the changes of the C, N, and S species on the Nylon topmost layers during the discoloration process. Significant changes in the XPS spectra of Ti 2p peaks were observed during discoloration of the wine spots. Wine stains attenuated the signal of the Ti 2p (458.4 eV) peak in the Nylon-TiO(2)-stained wine sample at time zero (from now on, the time before the discoloration process). Furthermore, a decrease of the wine-related O 1s signal at 529.7 eV and N 1s signal at 399.5 eV was observed during the discoloration process, indicating an efficient catalytic decomposition of the wine pigment on Nylon-TiO(2). X-ray diffraction detected the formation of anatase on the Nylon fibers. High-resolution transmission electron microscopy shows the formation of anatase particles with sizes between 8 and 20 nm.

Accelerated self-cleaning by Cu promoted semiconductor binary-oxides under low intensity sunlight irradiation

“…(8) would compete for the holes leading to oxidative radical species as noted in Eqs. (5)- (6) Cu (n−1)+ + h + → Cu n+ (8) Reactions (3) and (4) are thermodynamically allowed since the potential of Cu is more positive with respect to the potential required to generate electron Eqs. (3) and (4) and is more negative than the potential required for hole generation in Reaction (8).…”

“…Photocatalysis as a useful tool for the self-cleaning of glass, polymer thin films and textile fabric surfaces has recently been reported by Daoud [1][2][3][4], Kiwi [5][6][7][8], Hashimoto/Fujishima et al [9,10], Bahnemann [11][12][13], Radetic [14] and Pakkanen [15]. TiO 2 has been chosen as the standard photocatalyst used in the field of environmental photochemistry due to its stability, effective separation of charges under band-gap irradiation and availability of fairly pure samples.…”

“…There is nowadays a need to develop resistant photocatalysts presenting faster self-cleaning kinetics compared to TiO 2 and composite-TiO 2 surfaces which are too slow for many industrial applications [5][6][7][8][11][12][13]. The second area that needs improvement lies in the fact that most of the self-cleaning films are deposited from colloids on surfaces that are subsequently heated to diffuse and anneal the colloid into the surface at temperatures that fabrics and polymer films do not resist [5][6][7][8][9][10][11][12][13].…”

“…The second area that needs improvement lies in the fact that most of the self-cleaning films are deposited from colloids on surfaces that are subsequently heated to diffuse and anneal the colloid into the surface at temperatures that fabrics and polymer films do not resist [5][6][7][8][9][10][11][12][13]. The deposition/adhesion of this non-uniform low adhesive colloidal TiO 2 films are easily wiped out by finger or cloth since they are not mechanically stable.…”

“…We address hereby innovative self-cleaning by TiO 2 -ZrO 2 and TiO 2 -ZrO 2 -Cu films on PES reducing the self-cleaning time of methylene blue (MB). In the past our laboratory has worked on the self-cleaning of wine stains by TiO 2 on fabrics within 24 h [1,[5][6][7][8]13]. The self-cleaning performances of the TiO 2 -ZrO 2 and TiO 2 -ZrO 2 -Cu PES were compared with the self-cleaning performance of MB on PE-TiO 2 under Suntest light irradiation using the same experimental conditions [19].…”