Multipodal Au-C grafting of calix[4]arene molecules on gold nanorods.

The interface robustness and spatial arrangement of functional molecules on metallic nanomaterials play a key part in the potential applications of functional nano-objects. The design of mechanically stable and electronically coupled attachments with the underlying metal is essential to bring specific desirable properties to the resulting hybrid materials. In this context, rigid multipodal platforms constitute a unique opportunity for the controllable grafting of functionality. Herein, we provide for the first time an in-depth description of the interface between gold nanorods and a chemically-grafted multipodal platform based on diazonium salts. Thanks to Raman and X-ray photoelectron spectroscopies and theoretical modeling, we deliver insights on the structural and electronic properties of the hybrid material. More importantly, it allows for the accurate assignment of Raman bands. The combination of experimental and theoretical results establishes the formation of four carbon-gold anchors for the calix[4]arene macrocycle leading to the exceptional stability of the functionalized nano-objects. Our results lay the foundations for the future design of robust and versatile platforms.