Photoluminescence of a Freely Suspended Monolayer of Quantum Dots Encapsulated into Layer-by-Layer Films

A single monolayer of CdSe/ZnS quantum dots (QDs) has been encapsulated into a 60 nm free-suspended layer-by-layer (LbL) film. The QD monolayer showed a low light-emission within this film in contact with supporting solid substrates, but the manifold increase of photoluminescencence intensity was observed when the film was lifted and freely suspended over the microfabricated cylindrical cavities. This phenomenon was discussed in relationship with the effect of the elimination of the surface quenching enhanced by optical reflection from highly reflective silicon cavities. We suggest that a significant increase of the photoluminescence intensity of QD monolayers suspended over the microfabricated array can be interesting for future diagnostic and sensing applications.