FORMATION OF A GOLD SUPERLATTICE ON AN S-LAYER WITH SQUARE LATTICE SYMMETRY

This work describes a new strategy in which a crystalline bacterial ce ll surface layer (S-layer) composed of a monolayer of a single protein species was used as periodic nanometric template in the nucleation of ordered arrays of gold nanoparticles. A square superlattice of unifor m 4 to 5 nm sized gold particles with 12.8 nm repeat distance was fabr icated by exposing the S-layer lattice of Bacillus sphaericus CCM2177, in which thiol groups had been introduced before, to a tetrachloroaur ic(III) acid solution. Transmission electron microscopical studies sho wed that the gold nanoparticles were formed in the pore region during electron irradiation of an initially grainy gold coating covering the whole S-layer lattice. The shape of the gold particles resembled the m orphology of the pore region of the square S-layer lattice. By electro n diffraction and energy dispersive X-ray analysis the crystallites we re identified as gold (Au(0)). Electron diffraction patterns revealed that the gold nanoparticles were crystalline but in the long range ord er not crystallographically aligned. It is postulated that S-layers wi ll allow the fabrication of a wide range of inorganic nanocrystal supe rlattice arrays. (C) 1998 Elsevier Science Limited.