Core-Shell Gold Nanorod@Zirconium-Based Metal-Organic Framework Composites as in Situ Size-Selective Raman Probes.

Abstract

Nanoparticle encapsulation inside zirconium-based metal-organic frameworks (NP@MOF) is hard to control and the resulting materials often have non-uniform morphologies with NPs on the external surface of MOFs and NP aggregates inside the MOFs. In this work, we report the controlled encapsulation of gold nanorods (AuNRs) by a scu-topology Zr-MOF, via a room-temperature MOF synthesis. This is achieved by functionalizing the AuNRs with polyethylene glycol (PEG) surface ligands, al-lowing them to retain colloidal stability in the precursor solution and to seed the MOF growth. Using this approach, we achieve core-shell yields exceeding 99%, tuning the MOF particle size via the solution concentration of AuNRs. The functionality of AuNR@MOFs is demonstrated by using the AuNRs as embedded probes for selective surface-enhanced Raman spectroscopy (SERS). The AuNR@MOFs are able to both take-up or block molecules from the pores, thereby facilitating highly-selective sensing at the AuNR ends. This proof-of-principle study serves both to present the outstanding level of control in the synthesis as well as the high potential for AuNR@Zr-MOF composites for SERS.