Fabrication of densely packed gold nanoparticle films and their fluorescence enhancement effect

Stable and densely packed two-dimensional films of gold nanoparticles (AuPs) were fabricated on a glass substrate, in which the gold nanoparticle film (AuPF) formed at a liquid/liquid interface was sandwiched between titanium oxide [Ti(O)] layers; the Ti(O) layer was prepared by a surface sol-gel process. The structure of AuPF on the substrate was measured and evaluated by absorption spectroscopy, quartz crystal microbalance (QCM) measurement, and scanning electron microscopy (SEM). Without the Ti(O) layer, the deposited gold nanoparticles moved to form aggregates on the substrate surface, as was verified from SEM measurements. A clear plasmon band due to AuPs was observed in the deposited AuPF both on the bare and Ti(O)-modified substrates. Tetratolylporphyrin (TTP) was cast on the surface of AuPFs. The excitation efficiencies of TTP on the as-described modified substrates were compared. The use of the Ti(O) layer was quite effective both for preserving the morphology of AuPF as well as for reducing the quenching effect of the photoexcited TPP by Au.