Photonic bandgap influence on the SERS effect in metal-dielectric colloidal crystals optical fiber probe

This paper promotes a simple surface-enhanced Raman spectroscopy (SERS) substrate based on metal-dielectric colloidal crystal (MDCC) consisting in 3D self-assembled colloidal of polystyrene nanospheres (PSNPs) doped with gold nanoparticles (AuNPs). We demonstrate that the overlapping of localized surface plasmon resonance (LSPR) of noble metallic nanoparticles and photonic bandgap (PBG) of colloidal crystal can be tuned for the benefit of SERS performance. To tune the photonic bandgap, PSNPs with different diameter were selected, 242 nm and 300 nm, respectively, combined with AuNPs of about 23.3 nm. We found that the SERS signal can be enhanced more than 30 % when the laser excitation wavelength falls on the high wavelength edge of the photonic band gap. Moreover, the MDCCs have been fabricated by top-down methodology directly onto optical fiber providing efficient SERS-on-tip probes. The SERS features of the fiber probes in optrode configurations have been investigated by using different concentration of Rodamine (R6G) as molecular reporter. In all investigated cases, SERS activities is very well detectable even in case of R6G concentration of 1μM and analytical enhancement factors, AEF, of up to 3300 are obtained.