Minimal invasive synthesis in soft-nanoreactors: gas-triggered precipitation within reverse wormlike micelles

The precise control of nanoparticle (NP) morphology and size is fundamental to tailoring their electronic, optical, and catalytic properties. While self-assembled systems offer a promising route for bottom-up synthesis, traditional methods often suffer from a structural instability, and localized precipitation when liquid-phase triggers are used. Here, we report a versatile soft-nanoreactor platform based on reverse wormlike micelles (RWLMs) that utilizes a non-invasive, gas-triggered precipitation protocol to govern nanoparticle formation while preserving the structural integrity of the anisotropic environment.

Using a system of phosphatidylcholine and water in cyclooctane, we introduce a gas-triggered protocol to synthesize different nanoparticles, including Mg(OH)₂, AgCl, CaCO₃, and CdS. Reagent confinement and nanoreactor stability were monitored throughout the synthesis using rheology and Fourier-transform infrared (FT-IR), complemented by small-angle X-rays scattering (SAXS) and cryogenic transmission electron microscopy (cryo-TEM) to confirm NP formation within the aqueous channels.

Crucially, the intrinsic structural flexibility of the phospholipid interface allows the nanochannels to locally deform and expand, accommodating NP growth even beyond the initial micellar radius without collapsing the overall anisotropic network. Our results reveal that NP morphology is guided by the precursor concentration and the dynamic nature of the RWLM network, enabling a transition from quasi-spherical particles to highly monodisperse nanorods (radius of 6 nm and aspect ratio of 2). This study establishes RWLMs as flexible, and tunable nanoreactors, providing a framework for the design of functional nanomaterials within complex fluid environments.