Highly sensitive SERS behavior and wavelength-dependence charge transfer effect on the PS/Ag/ZIF-8 substrate

Area of Science:

• Materials Science
• Nanotechnology
• Spectroscopy

Background:

• Development of highly sensitive and reliable substrates for Surface-Enhanced Raman Spectroscopy (SERS) is crucial for molecular detection.
• Zeolite imidazole framework (ZIF-8) materials offer unique structural properties for potential applications in sensing.

Purpose of the Study:

• To synthesize and characterize a novel polystyrene colloidal particles/Ag/zeolite imidazole framework (PS/Ag/ZIF-8) composite material.
• To evaluate the SERS performance of the synthesized PS/Ag/ZIF-8 substrate using 4-mercaptobenzoic acid (4-MBA) as a probe molecule.
• To investigate the SERS mechanism, including electromagnetic and chemical enhancement, and its dependence on laser wavelength.

Main Methods:

• Synthesis of monodisperse PS/Ag/ZIF-8 composite substrates.
• Characterization using X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), UV-Visible spectroscopy, and X-ray Photoelectron Spectroscopy (XPS).
• SERS measurements with 4-MBA as probe molecules under varying laser wavelengths (473 nm, 514 nm, 633 nm, 785 nm).

Main Results:

• The PS/Ag/ZIF-8 substrate demonstrated outstanding SERS activity with 4-MBA.
• The SERS enhancement was attributed to a synergistic effect of electromagnetic and chemical (charge transfer) enhancement.
• An impressive enhancement factor (EF) of 1.23 × 10⁶ was achieved, with observed wavelength-dependent charge transfer effects.

Conclusions:

• The synthesized PS/Ag/ZIF-8 composite is a highly effective SERS substrate.
• Chemical interaction is essential for the observed charge transfer enhancement mechanism.
• This work highlights the potential of metal-organic framework nanostructures in developing advanced SERS substrates.