In the field of nanomaterials, multifunctional nanosystems play a prominent role in many applications as new magnetically recoverable catalysts, information processing, fuel cells, efficient bio/nanosensors, and nanomedicine. Aiming at the obtainment of new nanomaterials for biotechnological applications such as biosensors or theragnostic systems, we present a multifunctional system able to merge different properties in only one nanotool. The system is prepared by loading the pores of mesoporous zirconia nanoparticles with CoFe 2 O 4 , by a wet impregnation method, further modifying the surface of the material with bis(phosphonic acid) to load gold nanoparticles, produced by laser ablation. The obtained nanocomposite functionalized with a SERS probe represents a specific example of a magnetoplasmonic nanosystem. The results show the efficacy of the strategy of exploiting mesoporous zirconia nanoparticles for obtaining magnetoplasmonic nanotools.
The use of readily prepared bisphosphonic acids obtained in few steps through a thio‐Michael addition of commercially available thiols on tetraethyl vinylidenebisphosphonate enables the straightforward surface modification of amorphous mesoporous zirconia nanoparticles. Simple stirring of the zirconia nanoparticles in a buffered aqueous solution of the proper bisphosphonic acid leads to the surface functionalization of the nanoparticles with different kinds of functional groups, charge and hydrophobic properties. Formation of both chemisorbed and physisorbed layers of the bisphosphonic acid take place, observing after extensive washing a grafting density of 1.1 molecules/nm2 with negligible release in neutral or acidic pH conditions, demonstrating stronger loading compared to monophosphonate derivatives. The modified nanoparticles were characterized by IR, XPS, ζ‐potential analysis to investigate the loading of the bisphosphonic acid, FE‐SEM to investigate the size and morphologies of the nanoparticles and 31P and 1H MAS NMR to investigate the coordination motif of the phosphonate units on the surface. All these analytical techniques demonstrated the strong affinity of the bisphosphonic moiety for the Zr(IV) metal centers. The functionalization with bisphosphonic acids represents a straightforward covalent approach for tailoring the superficial properties of zirconia nanoparticles, much straightforward compared the classic use of trisalkoxysilane or trichlorosilane reagents typically employed for the functionalization of silica and metal oxide nanoparticles. Extension of the use of bisphosphonates to other metal oxide nanoparticles is advisable.
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