Sensitive and Homogeneous Surface-Enhanced Raman Scattering Detection Using Heterometallic Interfaces on Metal–Organic Framework-Derived Structure

Here the use of heterometallic interfaces on metal–organic framework-derived structures as surface-enhanced Raman scattering (SERS)-active substrates is investigated for sensitive and homogeneous SERS detection. Zeolitic imidazole framework-67 (ZIF-67) is grown on a conductive glass substrate via chemical bath deposition, followed by carbonization and oxidation to form ZIF-67-derived Co₃O₄ (ZIF-67-CO). For the sensitive and homogeneous SERS analysis, ZIF-67-CO is converted to the heterometallic interface Au–Ag@ZIF-67-derived Co₃O₄ (denoted as Au–Ag@ZIF-67-CO) via electrodeposition and successive chemical grafting. The optical properties of Au–Ag@ZIF-67-CO indicate a uniform and large-scale distribution of both metals on the surface. Raman signals from the substrate are evenly enhanced based on the Raman intensity and shift mapping over a large area. Due to the multiple absorption bands of the Au–Ag@ZIF-67-CO substrate, signal enhancement can also be achieved with two different laser sources (532 and 785 nm) that are frequently used in SERS. As a result, concentration-dependent and fingerprint SERS signals of small molecules such as 1,2-bis-(4-pyridyl) ethylene, Nile blue A, and 1,1′-diethyl-2,2′-cyanine iodide are obtained, and their signal enhancement factors are 104–105. Collectively, the use of heterometallic-interfaced ZIF-67-CO will be a beneficial approach for collecting reproducible SERS signals of various target analytes.