Very highly conductive Au films on glass substrates have been prepared by stepwise, layer-by-layer immobilization of 11-nm diameter colloidal Au particles and a short organic cross-linker. Particle coverage, optical spectra, nanometer-scale topography, and electrical resistance have been measured as a function of the number of colloidal Au layers and reveal a rapid transition from insulating to metallic behavior.

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Mesoporous thin films of rhenium-based "molecular squares", [Re(CO)3Cl(L)]4 (L ) pyrazine, 4,4′-bipyridine), have been utilized as sensors for volatile organic compounds (VOCs). The sensing was conducted using a quartz crystal microbalance with the target compounds present in the gas phase at concentrations ranging from 0.05 to 1 mM. Quartz crystal microbalance studies with these materials allowed for distinction between the following VOCs: (1) small aromatic versus aliphatic molecules of almost identical size and volatility and (2) an array of benzene molecules derivatized with electron donating/withdrawing substituents. The experiments suggest that the mesoporous host materials interact with VOC guest molecules through both van der Waals and weak charge-transfer interactions. In addition, size selectivity is shown by exposure of the molecular squares to cyclic ethers of differing size.