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 11 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.