A meso-tetraphenylporphyrin derivative with two butanethiol and two carboxylate groups on opposite phenyl substituents was first covalently bound to citrate gold particles by a self-assembly procedure. In a second self-assembly step the remaining areas on the gold surface were covered with a monolayer of a bolaamphiphile ("bola") containing a hydrosulfide end group for the attachment to gold and a triethylene glycol (TEG) end group for solubilization in water as well as in toluene. Bolas with octyl ends for dissolution only in toluene and with chiral gluconamide ends for water were also synthesized and applied. Two central secondary amide functions separated by 10 methylene units formed hydrogen bond chains within the monolayer and made it impermeable for cyanide ions. The porphyrin bottom of the water-filled gaps did not allow the passage of cyanide either. The holey membrane provided a complete protection against corrosion of the gold particles by 0.1 M cyanide in the bulk water. The porphyrin molecules on the bottom of the 2.2 nm wide gaps showed a weak fluorescence. It was quenched quantitatively by a tetracationic manganese porphyrinate, which fitted exactly into the gaps. A tetracationic porphyrin with a width of 3.4 nm caused no fluorescence quenching. The gaps thus have the uniform size of a monomeric porphyrin, and no domain formation was apparent. The same gaps with walls made of octadecanethiol did not discriminate between the two porphyrins of different size, both causing quantitative quenching. 1,2-trans-Cyclohexanediol or tyrosine were irreversibly immobilized within the gaps at pH 7 and stopped the entrance of the fitting porphyrin in both the rigid and the flexible gaps. The citrate gold particles thus proved to be smooth enough to allow the formation of well-defined gaps. It was also shown that 800 mg of gold colloid carries about 20 mg of membrane and gap material, which is enough for their characterization by solid-state NMR spectroscopy.