Enhancement in sensitivity and detection of luminescent quenching based oxygen sensing by gold nanoparticles

The field of plasmonics has shown a great promise in the enhancement of luminescence detection. Here, a simple method to enhance oxygen detection by quenching of Ru[(4,7-diphenyl-1,10-anthroline)3]2+ (or Ru[dpp]2+) in a sol-gel matrix by localized surface plasmon resonance (LSPR) of gold nanoparticles (AuNP) is presented. In the experiments, AuNP (10 ± 1.5 nm diameter) were added to a sol that was prepared by hydrolysis of trimethoxysilane, octyltrimethoxysilane and ethanol in the presence of Ru[dpp]2+ luminophore. The resulting sol of the mixture was spincoated on glass and allowed to age in the dark for one week to form the sol-gel film. A control sample was also prepared using the procedure, except that AuNP was not added to the sol. The resulting AuNP embedded sol-gel shows 8.3 times improvement in the baseline (0% O2) intensity (I0) over the control. Moreover, there is a dramatic improvement in the sensitivity from 0.0011 per % O2 in the control to 0.059 per % O2 with AuNP, for O2 level below 15%. Signal to noise ratio also improved, thus leading to a 100-fold improvement in the detection limit. Using phaseluminometry, it was determined that there is a reduction in the luminescence lifetime when AuNP is added to the sol-gel matrix. This reduction in the lifetime can be explained by the near-field interaction between the luminophores and the AuNP.