•Fluorescence quenching has been found in the PPP coupled to silver nanocap array.•Fluorescence quenching goes with the red-shifted PL peak of PPP in the hybrid.•Decreased Raman signal corresponds to increased PL intensity of PPP in the hybrid.•Inter-ring CC stretching vibration is connected with the fluorescence quenching.The optical properties of poly(2,5-dioctyloxy-p-phenylene) (DOO-PPP) coupled to a silver nanocap array are investigated by Raman and photoluminescence spectra. The emission intensity of the DOO-PPP coupled to the silver nanocap array is much weaker than that of the DOO-PPP film due to the fluorescence quenching of the silver nanocap array. In contrast with the freshly prepared sample, the fluorescence quenching efficiency of the silver nanocap array is obviously decreased for the sample exposed in air; correspondingly, the Raman intensity at 1609 cm−1 is markedly decreased, which is characteristic Raman peak of the inter-ring CC stretching vibration in the conjugated polymer. The experimental results indicate that the inter-ring CC stretching vibration plays an important role for the fluorescence quenching in the DOO-PPP coupled to the silver nanocap array.

•Fluorescence quenching has been found in the PPP coupled to silver nanocap array.•Fluorescence quenching goes with the red-shifted PL peak of PPP in the hybrid.•Decreased Raman signal corresponds to increased PL intensity of PPP in the hybrid.•Inter-ring CC stretching vibration is connected with the fluorescence quenching.The optical properties of poly(2,5-dioctyloxy-p-phenylene) (DOO-PPP) coupled to a silver nanocap array are investigated by Raman and photoluminescence spectra. The emission intensity of the DOO-PPP coupled to the silver nanocap array is much weaker than that of the DOO-PPP film due to the fluorescence quenching of the silver nanocap array. In contrast with the freshly prepared sample, the fluorescence quenching efficiency of the silver nanocap array is obviously decreased for the sample exposed in air; correspondingly, the Raman intensity at 1609 cm−1 is markedly decreased, which is characteristic Raman peak of the inter-ring CC stretching vibration in the conjugated polymer. The experimental results indicate that the inter-ring CC stretching vibration plays an important role for the fluorescence quenching in the DOO-PPP coupled to the silver nanocap array.