A. Aiboushev, A. Kostrov, F. Gostev, V. Nadtochenko
N.N. Semenov Institute of Chemical Physics Russian Academy of Sciences, RU
nanoplasmonics, femtosecond pump-probe spectroscopy, titanium dioxide, transient absorption, gold nanoparticles
Gold nanoparticles (AuNP) embedded in mesoporous films of wide band gap semiconductors such as TiO2 are used for promising applications in solar cells, visible light-sensitive photocatalysts, and biosensors developed on the basis of the surface plasmon resonance properties (SPR) of metal nanoparticles. In this work, femtosecond transient absorption spectra of gold nanoparticles embedded in mesoporous TiO2 ﬁlm were studied by laser photolysis pump–probe technique using 25 fs pulses at 740nm. The shift of the bleaching peak in transient spectra ~100 meV is detected in the AuNP/TiO2 system, whereas the bleaching peak shift of the same AuNPs in aqueous colloids is not more than 5 meV. The assumption about electron injection from gold nanoparticles to TiO2 matrix was made as well as simple quantitative model was built. Additional measurements for the range of energy for the femtosecond pump pulse were carried out. It occurred that the shift observed is the same for energies from 30nJ to 300nJ. Also, the shift of SPR of AuNPs in dependence of NP charge (red and blue for negatively and positively charged, respectively) was calculated by TDDFT. These facts additionally prove the possibility electron injection from AuNP to TiO2.