Visible‐Light Photoswitchable Covalent Tetra‐Ortho‐Fluoro‐Azobenzene Carbon Nanodot Hybrids for Optostimulation

Carbon nanodots (CNDs) have attracted growing interest due to their potential applications in sensing, imaging, and optically controlled bio-applications. Herein, the covalent functionalization of citric acid/ethylenediamine-based CNDs with a tetra-ortho-fluoro-azobenzene derivative (F-Azo) is presented. This approach aims to integrate the intrinsic photoluminescence of CNDs with the reversible photoisomerization properties of F-Azos triggered by visible light. The CND-F-Azo hybrids are synthesized via a terminal carboxylic acid group located on the F-Azo, which can be attached via amide coupling to surface-accessible amines on the CNDs. The structural and optical characterization of the resulting hybrid material is performed using a variety of analytical and spectroscopic techniques, as well as computational analyses supporting the covalent linking between the molecular and nanomaterial components and the interactions existing between them. In order to assess the impact of functionalization on physicochemical properties, the hybrid is further analyzed with respect to zeta potential, lipophilicity, and cell viability using HEK-293 cell assays. To assess cellular uptake and intracellular localization, confocal fluorescence imaging is employed. This work contributes to the development of light-responsive nanomaterials with tailored surface properties, highlighting the potential of Azo-functionalized CNDs as multifunctional platforms for future in vitro and in vivo optostimulation applications.