Highly Controlled Janus Organic-Inorganic Nanocomposite as a Versatile Photoacoustic Platform.

Controlling the structural order of nanoparticles (NPs), morphology, and composition is of paramount significance in tailoring the physical properties of nanoassembly. However, the commonly reported symmetrical nanocomposites often suffer an interference or sacrifice of the photophysical properties of the original components. To address this challenge, we developed a novel type of organic-inorganic Janus nanocomposite (JNCP) with an asymmetric architecture, offering unique features such as the precisely controlled localization of components, combined modular optical properties, and independent stimuli. As a proof of concept, JNCPs were prepared by incorporating two photoacoustic (PA) imaging agents, namely an organic semiconducting dye and responsive gold nanoparticles (AuNP) assembly in separate compartments of JNCP. Theoretical simulation results confirmed that the formation mechanism of JNCPs arises from the entropy equilibrium in the system. The AuNP assembly generated a PA images with the variation of pH, while the semiconducting molecule served as an internal PA standard agent, leading to ratiometric PA imaging of pH. JNCP based probe holds great potential for real-time and accurate detection of diverse biological targets in living systems.