Stacking-order Reversed Multilayers of ZIF-8 and Silver Nanoparticles for the SERS Detection of Organic Dye Species

Abstract

Surface-enhanced Raman spectroscopy (SERS)-active generally using include nanosized noble metals, semiconductors, or their combination, all of which are mostly subject to challenges such as difficulty in controlling fabrication processes, chemical stability of sensor substrates, reproducibility of amplified Raman signals. To address these concerns, novel SERS substrates were produced by combining zeolitic imidazolate framework-8 (ZIF-8) and Ag nanoparticles into stacked layers where the ZIF-8 acted as "trap nets" of the reporter molecules (organic toxins, rhodamine B, methylene blue and crystal violet). Two different multilayers on a glass slide generated by reversing the stacking order, i. e., Ag/ZIF-8/glass and ZIF-8/Ag/glass produced different SERS results. The ZIF-8/Ag/glass multilayer demonstrated a higher enhancement factor (& SIM;10(13)), the lower limit of detection (& SIM;10(-14) M) of rhodamine B, with a relative standard deviation of 4.2% for crystal violet, which was 10 times greater than the former arrangement. The sensitivity of the SERS substrates via exposure to low concentrations of organic dyes species was measured. Structural, surface morphology and optical features of the substrates were further examined. This result can pave the way for the development of metal-organic framework-based SERS platform and provide new insights into its application for label-free sensors in biomedical diagnosis and environmental monitoring.