(Invited) Atomic Layer Deposition for Stabilizing Surface-Bound Molecules for Photoelectrochemistry and Catalysis

Abstract

Molecularly sensitized devices that rely on surface bound molecules to impart functionality are keenly susceptible to device degradation via hydrolysis of anchor group chemistries and subsequent molecule detachment. Recent commercialization success in dye-sensitized solar cells is largely possible due to brute-force encapsulation engineering. However, using molecular sensitizers in aqueous environments as water oxidation catalysts or biological sensors poses an even greater challenge. This talk will highlight advances in the use of low temperature atomic layer deposition (ALD) applied after surface functionalization to drastically improve molecular attachment in aqueous environs. We have shown that ultrathin (< 1 nm) ALD coatings of inorganic oxides "surrounding" the molecular sensitizers improve attachment by orders of magnitude. These “coated” molecules still function as light absorbers, electron transfer agents, and catalytic species. The current state-of-the-science will be discussed including what has been learned about the changes in chemical structure upon ALD processing via in-situ FTIR spectroscopy and ex situ sum frequency generation spectroscopy. Finally, we will show the utility of this approach in creating new hybrid catalysts that combine the selectivity of homogeneous molecular catalysts with the recoverability of heterogeneous inorganic catalysts.