Gas Phase Multizone Synthesis and Localized Deposition of Pt/In Core−Shell Nanoparticles and Their Photothermoelectric Application

Multizone synthesis and localized deposition of bimetallic nanoarchitectures remain major challenges in additive manufacturing at the nanoscale, particularly when control over nanoarchitecture and localized functionality is required. Here, a multizone gas-phase electrodeposition strategy for the simultaneous synthesis and localized deposition of Pt/In core−shell nanoparticles through coupled vapor-phase encapsulation and electrostatic confinement is reported. In contrast to previous gas-phase electrodeposition studies that primarily focused on metallic and metal-oxide nano- and microarchitectures, the present work extends the process to bimetallic core−shell nanoarchitectures as functional nanoscale building blocks. Spark-generated Pt nanoparticles interact in flight with transported In vapor, enabling ligand-free Pt/In encapsulation before deposition. By controlling the In vapor supply through the evaporation temperature, two distinct nanoarchitectures are obtained: centric Pt-core/In-shell nanoparticles (evaporation temperature 750 °C) and eccentric core−shell nanoparticles (evaporation temperature 900 °C) with asymmetric shell distribution. In-flight particle collection reveals that the asymmetry initiates during high-temperature formation and becomes more pronounced during cooling after deposition. The charged Pt/In core−shell nanoparticles are selectively deposited into predefined Si micro-openings and linear patterns. The eccentric Pt/In structures exhibit broadened visible-light absorption and generate a measurable photo-thermoelectric response under illumination at 532 nm. The polarity reversal strongly supports the thermoelectric origin of the response. This approach establishes gas-phase electrodeposition as a route toward localized bimetallic core−shell nanoarchitectures for optothermal and thermoelectric applications.