Aligned monolayer assembly of zeolite crystals on platinum, gold, and indium–tin oxide surfaces with molecular linkages

Abstract

Zeolite-A crystals with the average sizes of ∼0.5 × 0.5 × 0.5 μm and ∼1.7 × 1.7 × 1.7 μm and silicalite-1 crystals with the average size of ∼1.6 × 1.2 × 0.6 μm were synthesized, and 3-aminopropyl (AP) and 3-chloropropyl (CP) groups, respectively, were tethered on the surfaces of each zeolite. The AP-tethering zeolite microcrystals (Z–AP) readily self-assembled into uniformly aligned monolayers with high degrees of coverage (DOCs) and close packing (DCPs) on the surfaces of conducting substrates (CSs) such as platinum (Pt), gold (Au), and indium–tin oxide (ITO) glass upon refluxing the toluene solution of Z–AP and CSs for 3 h. The CP-tethering zeolite (Z–CP) crystals also readily self-assembled into uniformly aligned monolayers in high DOCs and DCPs on the surfaces of CSs that were pre-coated with the polymeric amines such as dendritic polyamine (DPA) and polyethylenimine (PEI), respectively. The binding strength of the zeolite microcrystals to CS increased in the order: Z–AP–CS < Z–CP–DPA–CS < Z–CP–PEI–CS for a given CS and a given type of zeolite, and ITO < Au ≅ Pt for a given molecular linkage and a given type of zeolite.