Engineering ZIF-8@Ag core–satellite superstructures through solvent-induced tunable self-assembly for surface-enhanced Raman spectroscopy

Abstract

Metal–organic framework (MOF) based substrates have great potential for quantitative analysis of hazardous substances using surface-enhanced Raman spectroscopy (SERS) due to their significant signal enhancement, but face challenges like complex preparation, and lack of tunability. Here, we have successfully prepared a well-defined core–satellite superstructure (ZIF-8@Ag) through solvent-induced assembly of silver nanoparticles (Ag NPs) on truncated rhombic dodecahedral ZIF-8. By wisely selecting toluene as the solvent, the assembly process can be easily initiated through ultrasonic treatment and it allows for precise morphological adjustments to build a range of superstructures with different assembly densities of Ag NPs via feed ratio tuning. The as-prepared ZIF-8@Ag substrate leverages the high-density distribution of Ag NPs and the exceptional adsorption capabilities of ZIF-8. This combination makes it an outstanding SERS substrate for the detection of crystal violet (CV) and methylene blue (MB), achieving a concentration as low as 1 × 10⁻¹⁰ M and 1 × 10⁻⁹ M, respectively. Moreover, the Raman analytical enhancement factor (AEF) of this ZIF-8@Ag substrate can reach 1.35 × 10⁷, and the Raman signals exhibited high homogeneity. These findings are essential for constructing complex structures and achieving better performance in SERS enhancement substrates, which can broaden the application of this technology in other fields.