Facile fabrication of gold nanoparticle-titanium oxide alternate assemblies by surface sol-gel process

Multistructured assemblies consisting of gold nanoparticles and titanium oxide were alternately fabricated by a surface sol-gel process. First, a quartz glass substrate was immersed into an organic solution of titanium butoxide [Ti(OBu)(4)]. Then, the substrate was rinsed with water, and dried in air, giving ultra-thin titanium oxide [Ti(O)]-modified quartz glass substrate. This modified glass substrate was immersed into an aqueous colloidal solution of gold nanoparticles (AuPs) that were stabilized with citrate ions, giving a AuP-Ti(O)-modified glass substrate. By repeating these surface sol-gel processes, the multistructured assemblies of AuPs and Ti(O), [AuP/Ti(O)](n)/Glass (n = 1-4) were fabricated. Plasmon band intensity increased with the number of surface sol-gel process cycles. The resultant assemblies were stable even after I I days, or after treatment with an aqueous electrolyte solution. The alternate assembling of AuPs and Ti(O) was confirmed by quartz crystal microbalance measurements and absorption and X-ray photoelectron spectroscopies. Accordingly, we have succeeded in the preparation of stable AuP-Ti(O) composite films on the substrates.