Silver loaded anodic aluminum oxide dual-bandgap heterostructure photonic crystals and their application for surface enhanced Raman scattering

Abstract

Photonic crystals (PCs) are regarded as ideal materials for surface-enhanced Raman scattering (SERS) active substrates due to their unique optical behaviors of photonic band gap (PBG). In this work, for the sake of introduction of more PBGs in visible range, the Ag nanoparticle loaded anodic aluminum oxide dual-bandgap heterostructure photonic crystals (Ag@AAO DHPCs) SERS-active substrates are fabricated by using a specially designed periodic voltage–time waveform and vacuum thermal evaporation technology, which have a large-scale highly ordered nanopore structure, tunable high-quality multiple PBGs. As SERS substrates, the Ag@AAO DHPCs show excellent SERS-activity for Rhodamine B (RhB) with ultra-high sensitivity, uniformity, stability and reproducibility, the calculated enhancement factor (EF) can reach as high as 1.3 × 106, and the concentration limit can fall to an ultra-low value of 10−11 mol/L, suggesting that the trace detection of RhB could be realized with them. The outstanding SERS-activity of the Ag@AAO DHPCs would be mainly attributed to the introduction of multiple PBGs in surface plasma resonance (SPR) absorption range of silver nanoparticles and matching with the incident light, therefore, the stronger surface local electromagnetic field is obtained to enhance the SERS-activity through the synergistic effect of the Bragg reflection and the slow photon effect at the PBGs’ edges of AAO DHPCs. The Ag@AAO DHPC SERS-activity substrates are beneficial to the explorations of enhancement mechanism of surface Raman scattering signals and the developments of Raman imaging, biomolecular detection and chemical analysis.