Chemical Redox Reactions Induced by Cryptoelectrons on a PMMA Surface

We show that pristine PMMA can spontaneously transfer electrons to species in a liquid, thereby inducing a variety of electron transfer reactions. The electrons that are transferred we call cryptoelectrons; these have a surface density of the order of 5 x 10(13) cm(-2) and are at a considerably more negative reduction potential than the PMMA bonding electrons. For example, metal ions including Ag+, Cu2+, and Pd2+ were reduced and plated on a PMMA surface and Fe(CN)(6)(3-) was reduced to Fe(CN)(6)(4-). Moreover, protons were reduced when PMMA powder was dropped into a slightly acidic solution, resulting in a pH increase and hydrogen generation. Chemiluminescence was produced in a solution containing Ru(bPY)(3)(2+) and S2O82- with the addition of PMMA powder. These results clearly demonstrate that there are available electrons in PMMA that can participate in redox reactions at a rather negative potential. We also show that contacting PMMA with Teflon depletes this electronic surface charge. However, the PMMA used for a redox reaction or contacted with Teflon that was depleted of the electronic surface charge could be recharged by contacting with a suitable reductant.