In situ thermal fabrication of copper sulfide–polymer hybrid nanostructures for tunable plasmon resonance

Here, a novel strategy for fabricating plasmonic-polymer hybrid nanostructures via the in situ thermal synthesis of copper sulfide (CuS) nanocrystals within poly(N-vinyl caprolactam)-based microgels is presented. In particular, the carboxyl groups inside the microgels enriched Cu(2+) ions via electrostatic interaction, which further facilitated the nucleation inside the microgel matrix. The increase in nanocrystals' sizes with more added precursors indicated nanocrystals' continuous growth. The plasmon resonances in CuS nanocrystals were obtained due to the high-density free carriers in the covellite CuS. Both the sizes and the plasmon resonances of the as-synthesized CuS nanocrystals could be modulated by adjusting the amount of precursor. The fabricated hybrid nanostructures possessed good temperature responsivity, adjustable loading capacity, good colloidal stability, and pH dependent plasmon resonance. Furthermore, effective photothermal conversion performance was obtained under the illumination of a 980 nm NIR laser for controlling the phase transition of microgels, revealing promising potential in remotely controlled release of drugs.