Speaker
Description
Bimetallic Janus nanocrystals result from integrating two distinct metals side-by-side into one single particle[1]. This asymmetric arrangement allows the unique properties associated with each metal to be incorporated in tandem. When dispersed in an appropriate catalytic medium, such particles exhibit self-propulsion mediated by diffusiophoresis[2,3]. Before these properties can be exploited, robust and scalable synthesis protocols are required. Here we demonstrate the preparation of bimetallic palladium-silver Janus nanocrystals using a seed-mediated growth method[4]. The kinetically controlled overgrowth of plasmonic Ag caps on the Pd seeds is followed by coupling in-situ small-angle X-ray scattering (SAXS) with UV-Vis absorption spectroscopy. Currently these self-propelled systems are typically studied at low volume fractions. Moving forward with a robust synthesis and sufficient yield of these particles, it will be possible to realize self-propelled or active colloids at high volume fractions. SAXS and X-ray photon correlation spectroscopy (XPCS) will be used to probe the interactions and dynamics in these active systems. Furthermore, the asymmetry of particles enables to access the rotational diffusion by XPCS. This work provides a groundwork for future studies into the diffusiophoretic self-propulsion of active colloids, which mimic certain collective behavior of living systems.
Figure 1. Schematic illustration of Pd-Ag growth through controlled injection rate (left). In-situ SAXS patterns of palladium seed growth (right).
References
[1] Qiu J. et al. Bimetallic Janus Nanocrystals: Syntheses and Applications. Adv. Mater. 2022, 34, 2102591.
[2] Zinn T. et al. Emergent dynamics of light-induced active colloids probed by XPCS. New J. Phys. 2022, 24, 093007.
[3] Zhu W. et al. Exploring the Synthesis of Self-Organization and Active Motion. J. Phys. Chem. Lett. 2024, 15 (20), 5476-5487.
[4] Zeng, J. et al. Controlling the Nucleation and Growth of Silver on Palladium Nanocubes by Manipulating the Reaction Kinetics. Angew. Chem. Int. Ed. 2012. 51: 2354-2358.
