Beta-lead oxide quantum dot (β-PbO QD)/polystyrene (PS) composite films and their applications in ultrafast photonics.

Polymer composite films, particularly those based on polymers and layered nanomaterials, are attractive materials for exploiting the properties of multiple materials for applications in electronics and photonics. In this work, a beta-lead oxide quantum dot (β-PbO QD)/polystyrene (PS) composite film is successfully fabricated by a solution blending method. The β-PbO QDs are well-distributed within a β-PbO QD/PS composite film and the composite film is transparent and flexible. Owing to the almost complete insolubility of both β-PbO QDs and PS, the as-fabricated β-PbO QD/PS composite film holds the nonlinear photonic response from 540 nm to 1060 nm under complete water immersion, confirming its excellent stability to high humidity. Additionally, the β-PbO QD/PS composite film exhibits a considerable capacity for optical modulation owing to a strong nonlinear absorption coefficient compared with those of other two-dimensional (2D) materials. On the basis of a home-made β-PbO QD/PS composite film saturable absorber, stable mode-locked pulses at 1060 nm are generated under humid conditions. It is anticipated that the β-PbO QD/PS composite films enable the exploitation of new waterproof, flexible photonic devices based on functional 2D materials and polymers.