Trapping of molecules in alkanethiol self-assembled monolayer matrices

Reactions of NH4+ in water solutions with self-assembled monolayer (SAM) su rfaces result in the deposition of ammonia in the monolayers. Similarities between this and the soft landing of ions seen in low energy gas phase ion- surface collisions suggest that monolayers can be used as matrices to prese rve species. Ammonia can be incorporated only into thicker SAMs such as tho se made from octadecanethiol. Reactions with larger ions do not lead to tra pping. Trapped ammonia desorbs during prolonged exposure of the SAMs to vac uum.