TY - JOUR
T1 - Absorption vs. Redox reduction of Pd 2+ and Cu 2+ on triboelectrically and naturally charged dielectric polymers
AU - Piperno, Silvia
AU - Cohen, Hagai
AU - Bendikov, Tatyana
AU - Lahav, Meir
AU - Lubomirsky, Igor
PY - 2012/4/28
Y1 - 2012/4/28
N2 - It has recently been reported that Teflon and polyethylene (PE) if rubbed by polymethylmethacrylate (PMMA) or Nylon as well as non-rubbed PMMA and Nylon induce "redox" reactions, including those of the reduction of Pd +2 and Cu +2 ions. On this basis, it was deduced that these dielectric materials may hold ≅10 13-10 14 of "hidden" electrons cm -2, a value at least three orders of magnitude higher than the charge that a dielectric surface can accumulate without being discharged in air. The "hidden" electrons were termed "cryptoelectrons". In variance to these reports, we offer here an alternative interpretation. Our model is supported by X-ray photoelectron spectroscopy, contact angle and vibrating electrode (modified Kelvin probe) measurements performed on representative examples. Rubbing of the polymers was found to transfer polymer fragments between the rubbed surfaces altering their physical properties. The transferred polymer fragments promote adsorption of Cu 2+ and Pd 2+ ions. It was found that Teflon and PE rubbed with PMMA and Nylon, and non-rubbed PMMA and non-rubbed Nylon do not induce "redox" reactions of Cu 2+ and Pd 2+ ions but adsorb these ions on their surfaces. Furthermore, the earlier reported reduction of Pd 2+ to Pd 0 by electrons, as detected by catalytic activity of Pd 0 in a Cu-plating bath, can be alternatively explained by reduction of adsorbed Pd 2+ by the reducing agents of the bath itself. Based on these findings, we support the hypothesis that charging of dielectric polymers is due to ions or free radicals rather than electrons and there is no evidence to invoke a hypothesis of "cryptoelectrons".
AB - It has recently been reported that Teflon and polyethylene (PE) if rubbed by polymethylmethacrylate (PMMA) or Nylon as well as non-rubbed PMMA and Nylon induce "redox" reactions, including those of the reduction of Pd +2 and Cu +2 ions. On this basis, it was deduced that these dielectric materials may hold ≅10 13-10 14 of "hidden" electrons cm -2, a value at least three orders of magnitude higher than the charge that a dielectric surface can accumulate without being discharged in air. The "hidden" electrons were termed "cryptoelectrons". In variance to these reports, we offer here an alternative interpretation. Our model is supported by X-ray photoelectron spectroscopy, contact angle and vibrating electrode (modified Kelvin probe) measurements performed on representative examples. Rubbing of the polymers was found to transfer polymer fragments between the rubbed surfaces altering their physical properties. The transferred polymer fragments promote adsorption of Cu 2+ and Pd 2+ ions. It was found that Teflon and PE rubbed with PMMA and Nylon, and non-rubbed PMMA and non-rubbed Nylon do not induce "redox" reactions of Cu 2+ and Pd 2+ ions but adsorb these ions on their surfaces. Furthermore, the earlier reported reduction of Pd 2+ to Pd 0 by electrons, as detected by catalytic activity of Pd 0 in a Cu-plating bath, can be alternatively explained by reduction of adsorbed Pd 2+ by the reducing agents of the bath itself. Based on these findings, we support the hypothesis that charging of dielectric polymers is due to ions or free radicals rather than electrons and there is no evidence to invoke a hypothesis of "cryptoelectrons".
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U2 - 10.1039/c2cp23000c
DO - 10.1039/c2cp23000c
M3 - Article
C2 - 22398656
AN - SCOPUS:84859348210
VL - 14
SP - 5551
EP - 5557
JO - Physical Chemistry Chemical Physics
JF - Physical Chemistry Chemical Physics
SN - 1463-9076
IS - 16
ER -