Heteronanotrimers by Selective Photodeposition of Gold Nanodots on Janus‐Type Cu _2‒ <i> _x </i> S/CuInS ₂ Heteronanocrystals

This study focuses on the development of environmentally friendly Au-Cu_2-xS/CuInS₂ heteronanotrimers. The chosen strategy relies on the laser photodeposition of a single gold nanodot (ND) onto Janus Cu_2- _xS/CuInS₂ heteronanocrystals (HNCs). This method offers precise control over the number, location, and size (5 to 8 nm) of the Au NDs by adjusting laser power for the career production, concentration of hole scavenger for charge equilibration in redox reactions, and gold precursor concentration, and exposure time for the final ND size. The photoreduction of gold ions onto HNCs starts systematically at the Cu_2- _xS tip. The Au deposition then depends on the CuInS₂ segment length. For short HNCs, stable Au-Cu_2- _xS/CuInS₂ heteronanotrimers form, while long HNCs undergo a secondary photo-induced step: the initial Au ND is progressively oxidized, with concomitant deposition of a second gold ND on the CuInS₂ side, to yield Au₂S-Cu_2- _xS/CuInS₂-Au heteronanotrimers. Results are rationalized by quantitative comparison with a model that describes the growth kinetics of NDs and Au-Cu_2- _xS transformation and emphasizes the importance of charge separation in predicting selective deposition in heteronanotrimer production. The key parameter controlling Au-Cu_2‒ _xS/CuInS₂ HNCs is the photoinduced electric field gradient generated by charge separation, which is tailored by controlling the CuInS₂ segment size.