Nanoparticles, especially plasmonic gold nanorods (AuNRs), have gained significant attention due to their unique properties and diverse applications across various fields such as medicine, electronics, and energy. Recently, researchers introduced an innovative characterization technique utilizing optical back coupling (OBC) combined with size exclusion chromatography (SEC) to provide comprehensive insights on the size and shape distributions of these nanoparticles.
The study outlines how the optical back coupling technique, which previously analyzed sedimentation coefficients through analytical ultracentrifugation, can be effectively adapted to standard laboratory settings using size exclusion chromatography. This method leverages the exceptional spectral extinction of plasmonic nanoparticles, allowing for the determination of multidimensional properties including length, diameter, aspect ratio, volume, and surface area distributions all within one experiment.
Conducted by scientists from renowned institutions, including the Deutsche Forschungsgemeinschaft, this groundbreaking research was published on March 12, 2025. They validated their approach utilizing various gold nanorods characterized by different aspect ratios, with supplementary confirmation through scanning transmission electron microscopy (STEM).
Traditional techniques for nanoparticle characterization, such as transmission electron microscopy (TEM) and dynamic light scattering (DLS), face limitations, such as the need for extensive analysis, high costs, and limited resolution. The new OBC-SEC method, on the other hand, offers rapid and precise two-dimensional characterization, even allowing researchers to distinguish subtle differences among nanoparticles.
By evaluating the optical features of the nanoparticles as they are separated through the SEC process, researchers could classify the AuNRs according to their hydrodynamic diameter, effectively linking these sizes to their potential applications. For their experimental setup, the researchers utilized the Ultimate 3000 UHPLC (high-performance liquid chromatography) system, employing specific protocols including maintaining constant flow rates and using optimized mobile phases to maximize efficiency.
This technique uniquely positions researchers to obtain detailed size distributions, allowing for what was previously considered inaccessible data related to the synthesis and applications of nanoparticles.
Overall, the OBC-SEC technique signifies a substantial advancement for nanoparticle characterization, presenting new pathways for optimizing nanoparticle performance across various applications such as photothermal therapy for cancer, where their size and shape significantly influence their therapeutic effectiveness.
Future iterations of this methodology hold the promise of adding even greater depth to nanoparticle analysis, potentially applying it to other nanostructured materials and enhancing its applicability to broader scientific inquiries.